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High risk surgical patientsIntroductionDespite improvements in our understanding of the pathogenesis of postoperative organ dysfunction, death and serious morbidity are still common following major surgery. Outcome following major surgery varies significantly both within and between countries.Critical care techniques and therapies are increasingly utilised in the operating room. Improved perioperative care of the high-risk patient has resulted in significant improvements in outcome. This approach requires a detailed understanding of patient and operative risk to facilitate the most appropriate use of scarce resources and to obtain the best postoperative outcomes.Critical care does not solely occur on critical care units but can be achieved with a combination of postoperative care units, step down units and outreach. Quality care does not mandate critical care but can be achieved by a dedicated multidisciplinary care team starting from preoperative assessment through quality recovery to a speedy return home.When a high-risk surgical patient is cared for on a critical care unit the management strategy should be proactive (preventing the onset of organ failure) rather than reactive (treating established organ failures that might have been prevented). Improvement in outcomes of high-risk surgical patients is a success story of modern critical care medicine.This module assumes standard preoperative work up including clinical history and examination, routine bloods, electrocardiogram for those with risk factors for or a history of cardiac disease, and chest X-ray where appropriate.You will find it helpful to read the following references before starting this module.1/ How to recognise the high-risk surgical patientDefining the high-risk surgical patientDefinitionThe high-risk surgical patient can be defined as: An individual with a higher probability of suffering excess morbidity and mortality following surgery as a result of co-morbid medical factors or the nature of the surgical intervention itself or a combination of these.Multidisciplinary approach and communicationAnaesthetic and surgical colleagues should identify high-risk surgical patients prior to surgery. It is therefore essential that the critical care team be in close communication with their anaesthetic and surgical colleagues in order to be aware of these surgical patients and to facilitate the planning of postoperative care. Many high-risk patients undergoing elective surgery are identified in preoperative assessment clinics, either by anaesthetists or trained nurse practitioners. A critical care consult can be requested from such a screening clinic.The PACT module on Communication skills contains a helpful section on communicating with coworkers?.Clinical identification of the high-risk surgical patientHistory and examinationIn addition to information about past episodes of surgery and anaesthesia, the patient history should also be used to identify the presence and determine the severity of co-morbid medical factors and intercurrent illness that may influence operative outcome (e.g. ischaemic heart disease (IHD), chronic obstructive pulmonary disease (COPD), diabetes).For those with risk factors for or a history of cardiac disease, initial history, examination and ECG evaluation should focus on identification of potentially serious cardiac disorders, including:Coronary artery disease e.g. prior myocardial infarction, angina pectorisCongestive heart failureElectrical instability e.g. symptomatic arrhythmiasFor more information see the PACT module on Basic clinical examination?Specific risk factorsThe following factors are associated with an increased risk of mortality and morbidity following surgery.Patient factorsAgePatient age tends to profoundly influence clinicians' preoperative perceptions of risk. However as an isolated indicator of risk, chronological age should be treated with caution since it may be confounded by co-morbidity which is more common in the elderly. Physiological age or physiological reserve may be more useful concepts and cardiorespiratory reserve, in particular, is likely to be an important factor in determining patient outcomes.Pathophysiology and chronic illness/diseaseThe presence of systemic illness can lead to increased perioperative risk particularly where pathology impacts upon cardiorespiratory function. Comorbid problems such as chronic obstructive pulmonary disease, ischaemic heart disease and diabetes contribute to increased risk in an additive way (e.g. the mortality associated with abdominal surgery more than doubles if the patient has chronic heart failure; see Pedersen reference, below). It is important to quantify the nature and severity of these illnesses and to recognise when specialist input from medical teams is required. The goal of these preoperative interventions is to optimise the physiology of the patient prior to the onset of surgical stress.AnecdoteA 54-year-old woman with exertional angina presented for elective hip replacement. She needed appropriate diagnostic and interventional procedures.Investigation and management of cardiac problems is independent of the need of surgery. If this patient were not having surgery there would still need to be investigation and management of the exertional angina. Although there is no demonstrated benefit from specific cardiac investigation and management in terms of modifying outcome following elective surgery per se, it is considered prudent to delay elective surgery in the majority of cases.Surgical factorsOverall surgical mortality in Europe and the USA is thought to be less than 1% and for minor procedures in healthy patients (e.g. day surgery) the mortality risk is extremely low. However, this masks the fact that for certain procedures there is significant associated mortality and risk of perioperative complications.General considerationsAs a general rule, intra-cavity surgery is associated with poorer outcomes when compared with extra-cavity procedures. Similarly, emergency surgery is associated with higher mortality and morbidity than scheduled, elective work. In all of these cases prolonged surgical procedures with larger volumes of blood loss are, as to be expected, associated with poorer outcomes.Type of surgical procedureFor example, data from the United States suggest that carotid endarterectomy is associated with in-hospital 30-day mortality of between 1.5 and 1.7% while lower extremity bypass grafts exhibit mortality of 4.1 to 5.1% and mitral valve replacement is associated with figures as high as 15.1% (see Birkmeyer reference, below). It is clearly important to recognise the risks specific to a given procedure and prepare appropriately.Elective versus emergency proceduresEmergency procedures are associated with a higher operative mortality than elective procedures (reference below). This is likely to be attributable to multiple factors including the acute physiology associated with the emergency, surgical diagnosis and out-of-hours hospital infrastructure considerations, for example pre and post surgical care, and the seniority of surgical and anaesthetic staff.Appropriate preoperative investigationsA range of invasive and non-invasive investigations may be available to the anaesthesiologist in the preoperative period. It is important that these are appropriate and guided by the findings of history and examination. It is important to understand the value, risks and benefits of each investigation and how management will be altered in light of results. There is almost no evidence to support many of the more sophisticated investigations that exist to stratify cardiac risk (e.g. thallium scan).Preoperative testing should be limited to circumstances where the result will influence patient treatment and outcome.Assessment and initial management of cardiac riskCommunicationAssessment and initial management of cardiac risk in the perioperative setting does not differ from management in the non-operative setting. A number of guiding principles apply. Good communication between anaesthesiologist, surgeon, critical care specialist and cardiologist is essential. Indications for testing and treatment should be the same as those outside the perioperative setting. Timing of tests and treatment will be governed by the urgency of surgery, and by the estimated level of risk from cardiac and non-cardiac causes.?Clearly no tests or preoperative cardiological interventions will be appropriate or possible on acute presentation of ruptured aortic aneurysm whereas in less urgent cases appropriate management of cardiac problems can be planned. The ECG, echocardiogram and exercise test are commonly helpful.There is no evidence to support pre-emptive angioplasty or coronary artery surgery except where that would have been indicated in the patient irrespective of their surgical condition and when there is no urgency to the surgical problem.NoteCoronary revascularisation before non-cardiac surgery to enable the patient to get through the non-cardiac procedure is appropriate only for a small subset of patients at very high-risk.Assessment of exercise toleranceExercise tolerance is a key determinant of outcome following surgery. Patients who are able to perform well (higher anaerobic threshold/VO2?max and absence of evidence of ischaemia) when challenged physiologically by either an exercise challenge (bike/treadmill) have improved outcome (see Task 4–pathogenesis of perioperative morbidity?).The patient history may be used to perform a rough estimate of exercise tolerance allowing the anaesthesiologist to gain an indirect assessment of cardiorespiratory reserve. The limitations of such an assessment tool should however be acknowledged. Questioning needs to be specific e.g. 'Did you have to stop when walking from the car park to the entrance of the hospital?'Practical clinical assessment of exercise tolerance can be achieved using a number of objective systems although the ability of these methods to identify those who will be at risk in this situation has not been formally tested.Where available, formal cardiopulmonary exercise testing of patients prior to high-risk surgery can provide very useful information. This technique has been shown to discriminate well between those at high and low risk of mortality following major surgery (Older reference below). Physiological profiling using a pulmonary artery flotation catheter can also be used for this purpose.Scoring systems for surgical riskVarious methods are available for describing perioperative risk in patients. Simple categorical systems (e.g.?the American Society of Anesthesiologists Physical Status Score (ASA) score) are commonly and easily used. Whilst they only discriminate very broadly between levels of risk they are useful for 'flagging up' patients who may require a higher level of care.More complex scoring systems (e.g.?the Physiological and Operative Score for enUmeration of Mortality and Morbidity (POSSUM)) can provide rich datasets for comparison of outcomes between individuals or institutions but are not currently commonly used in day-to-day practice. This type of data could potentially be incorporated into clinical IT systems and used to provide clinicians with more sophisticated information on a day-to-day basis. However, it is important to understand that whilst these data can provide robust comparisons when populations of patients are studied they do not provide precise estimates of risk at an individual patient level.This means that they can be used to guide levels of care, for example elective postoperative critical care, but a high-level of caution should be attached to making decisions about withholding care or futility based on this type of information.American Society of Anesthesiologists Physical Status ScoreASA score?This classification only describes physical status and does not take into account operative status. It is quick and easy to use but there is a degree of subjectivity in allocation of scores. Increasing ASA score is associated with worse outcome following surgery.Patient examples for Q1?to Q3?What are the ASA scores for each patient?How would you rank the patients for surgical risk? Justify your answerHow much weight do you give in your assessment of risk to the patient's exercise tolerance?The Physiological and Operative Score for enUmeration of Mortality and MorbidityPOSSUM is more complex to calculate and requires variables that may not be routinely collected in lower risk patients. However, it is more sophisticated and enables comparison with benchmark populations. Entry of the physiological and operative severity scores (tables below) into a regression equation produces an expected event risk for that patient. Note that physiological component alone is not predictive?–?the expected risk is only available after surgery when the operative severity score is available.POSSUMphysiological score?POSSUMoperative severity score?Raw mortality?Five surgeons (A-E) perform different types of surgery and therefore have a spectrum of risk profiles for their patients and operations. Case-mix adjustment achieved by comparing observed and expected mortality using the POSSUM system allows meaningful comparison of their data and demonstrates that all are performing to a similar standard which is consistent with historical POSSUM data.Case-mix adjusted mortality observed:expected RatioSource: Copeland et al. Br J Surg 1995For the next ten surgical patients you see, try calculating the surgical risk using the POSSUM calculator from the following website. with your colleagues the utility of this score in assessment of patients prior to surgery.Assessing cardiac risk in non-cardiac surgerySeveral scoring systems have been developed with the specific aim of evaluating cardiac risk in non-cardiac surgery. Goldman (reference below) described a system based on assigning different numerical scores to specific diagnoses and then summing the score for an individual to provide an index of overall risk of cardiovascular complications.This was subsequently developed by Detsky and then Lee (reference below) into the Revised Cardiac Risk index. The revised index includes the following six independent predictors of cardiovascular complications: high-risk type of surgery, ischaemic heart disease, history of congestive heart failure, history of cerebrovascular disease, insulin therapy for diabetes, and preoperative serum creatinine >177 ?mol/l (>2.0 mg/dl). Patients are then placed into categories of increasing risk based on the presence of 0, 1, 2 or ≥3 factors.Clinical predictors of increased perioperative cardiovascular risk for non-cardiac surgeryThe joint ACC/AHA guidelines for perioperative cardiovascular evaluation for non-cardiac surgery divide patients into groups of low, intermediate and high levels of cardiovascular risk based on a set of clinical predictors (see table below). These guidelines also include some useful recommendations for additional preoperative investigations to further evaluate cardiovascular risk.Clinical predictors of increased perioperative cardiovascular risk?ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery 2002. Full Text available from:?[Science & Professional/Library/Statements & Guidelines/ View scientific statements by topic/ACC/AHA Joint Guidelines]Scoring system summaryThe ASA score is almost universally used in clinical practice and is a useful way of recording and communicating risk between clinicians. Functional capacity based on exercise tolerance is important. Subjective assessment of exercise tolerance is known to be unreliable so objective exercise testing may be appropriate in those in whom it is not possible to be confident that exercise tolerance is good.In those with cardiovascular risk factors, the ACC/AHA guidelines provide a useful framework for perioperative cardiovascular evaluation.More complex scoring systems such as POSSUM are capable of providing rich comparative audit data about outcome following surgery but have limited utility in the day-to-day assessment of patients prior to surgery.ThinkScreening by objective cardiorespiratory testing could potentially be used to allocate scarce resources e.g. critical care beds.Using the ten patients that you previously scored using the POSSUM system compare the level of risk suggested using the ASA system and the ACC/AHA guidelines for perioperative cardiovascular evaluation. How did the results obtained compare with your initial clinical evaluation?2/ How to describe perioperative complicationsPerioperative adverse outcome is common, and is frequently under-reported. No common system has been widely adopted for describing morbidity or complications following surgery, making comparison between surgeons, institutions or clinical trials difficult. On the critical care unit, established organ failure scores can be used. On normal wards, the Postoperative Morbidity Survey (POMS) is the only validated tool available.Intra-operative complicationsPre-morbid state and the nature of surgery influence the likelihood of adverse intra-operative events. These intra-operative events in turn contribute to postoperative outcome. Because of this they are integral to scoring systems employed to?compare postoperative outcomes. For example, the Operative Severity Score (OSS) of the POSSUM system includes measures of perioperative blood loss and intra-peritoneal soiling by gut contents.Intra-operative complications influence both short-term operative outcomes and may also influence long-term outcome. For example, intra-operative cardiac events seem to have an influence on mortality for at least 12 months in high-risk surgical patients.Postoperative complicationsWhen efforts are made to actively identify and record complications following surgery it is clear that postoperative complications are common following major surgery and are frequently under-reported in routine practice. Placing patients in an environment which facilitates close supervision and monitoring with a view to early recognition and treatment of complications is believed to result in improved overall outcome following surgery.Classically, postoperative events have been classified according to early, intermediate and late, based on their timing relative to operation and local (directly related to the site of surgery) and general. Although this approach has provided a common language for categorising complications it has not aided understanding of pathogenesis.Reporting of complications following surgery has been very variable, making comparisons between studies and institutions very difficult. Reporting of postoperative complications has frequently focused on specific adverse outcomes directly related to the conduct of the operation, for example the breakdown of a bowel anastamosis.It has long been recognised that many patients have multiple organ dysfunction following major surgery (some progress to multiple organ failure) and this is well documented within the intensive care environment using scoring systems such as the SOFA and SAPS (for further information, see the PACT module on Clinical outcome?).Outside of intensive care units many patients have prolonged hospital stay related to relatively 'minor' organ dysfunction (from a critical care perspective) and this is commonly under-diagnosed. Attempts to describe this phenomenon have been very limited and inconsistent, and interventions aimed at treating or preventing these problems have the potential to significantly improve outcomes following surgery.Early warning systemsEarly identification and treatment of postoperative complications is aided by a proactive approach to surveillance in postoperative patients. Critical care outreach staff have an important role to play in this area. Surgical wards commonly have low staffing levels that are not consistent with adequate surveillance for postoperative complications. The use of early warning criteria based on simple physiological variables has become more common to facilitate identification of patients developing postoperative complications. An example of a scoring system for identifying deteriorating patients is the MEWS score. Its use is documented in the Goldhill reference on the next screen.Patients identified to have complications should be aggressively managed by individuals with appropriate knowledge and skills and it is therefore important that the critical care team is involved early. An increase in level of care will almost always be appropriate. This can be achieved either by moving the patient to a critical care unit (ICU, High Dependency Unit (HDU), Post Anaesthetic Care Unit, or similar) or by bringing the environment to the patient by means of provision of augmented level of monitoring and nursing care (ongoing outreach).Operational definitionsAn alternative approach to reporting postoperative morbidity is to use multifactorial systems of assessment, which take into account both interventions and physiological scoring based upon objective clinical observations. One example of such a system is the Postoperative Morbidity Survey (see reference below); the only validated prospective system for describing short-term, postoperative harm.AnecdoteA 79-year-old woman returned to a general, post-surgical ward following a total hip replacement. She was prescribed two litres of normal saline over 24 hours as postoperative fluid replacement and took no oral fluids because of nausea associated with her patient-controlled analgesia. The house officer was finally called when she was found to have been anuric for more than four hours. Review of the fluid balance chart revealed a decreasing urine output over the preceding 12 hours. She required admission to ICU for acute renal failure and eventually required renal replacement therapy leading to a prolonged stay in the critical care setting. This admission was later complicated by severe sepsis secondary to intravenous catheter colonisation.ThinkCan you think of similar scenarios in which close observation, early recognition of a postoperative complication and a simple clinical intervention (in this case appropriate fluid management) may have successfully prevented adverse clinical outcome.3/ How to prevent/treat perioperative complicationsTwo approaches are needed to reduce the incidence and impact of perioperative complications. Firstly, prevention is vital and it is clear that a number of strategies are available which reduce mortality and morbidity following surgery when used in the immediate perioperative period. Secondly, effective treatment depends on early recognition (see Task 2) and appropriate management of specific morbidities.Preventive strategies can be divided into those that have been shown in clinical trials to reduce the mortality and morbidity following surgery and those that have been shown to reduce the level of specific morbidities following surgery.Only two strategies of perioperative care, haemodynamic goal-directed therapy and β-adrenoreceptor blockade, are claimed to reduce both mortality and morbidity following surgery and these will be discussed later in this module.An additional group of interventions that have been shown to improve outcome in other aspects of critical care may also provide benefit in the perioperative setting. Some clinicians extrapolate from these critical care studies and allow them to guide their perioperative practice. These interventions await formal evaluation in the perioperative setting.Interventions influencing specific morbiditiesInterventions that have been demonstrated in randomised controlled trials to reduce the level of specific postoperative morbidities in surgical patients:Maintenance of normothermia?has been shown to reduce wound infection rates and shorten length of hospital stay.Thromboembolic prophylaxis?has been shown to reduce the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) following surgery.Maintenance of good oxygenation?has been shown to reduce wound infection rates and nausea and vomiting.Early enteral feeding?following gastrointestinal surgery, either orally or directly into the small bowel, reduced infectious complications and length of stay when compared with a 'nil by mouth' strategy.Choice of resuscitation fluidAlthough the crystalloid colloid debate is still unresolved (large RCTs are currently underway), the electrolyte composition of the solution seems to have an effect on outcome. Use of isotonic saline (0.9% NaCl solution) or of colloid solutions dissolved in isotonic saline appears to result in increased metabolic acidosis, decreased urine output/renal function and increased coagulopathy when compared with more physiologically balanced solutions such as Hartmann's solution.Prophylactic antibiotics?administered pre-emptively reduce infection rates but there is no evidence of any benefit of further doses beyond the first postoperative day. Commencing antibiotics before the immediate preoperative period provides no benefit. High dose regimens are no better than standard dosage.Haemodynamic goal-directed therapy and β-adrenoreceptor blockade?are discussed below.A multimodal approach incorporating many of the elements listed above coupled with careful preoperative preparation, regional analgesia, early removal of nasogastric and urinary catheters and early mobilisation has been shown to be beneficial in colo-rectal surgery and this type of approach is likely to become more common in other types of surgery.Other interventionsCertain interventions that have been demonstrated in randomised controlled trials to influence mortality or morbidity in other patient groups that may be of benefit in high-risk surgical patients:Transfusion triggersThere is evidence that wound infection rates and tumour recurrence rates are increased following transfusion of autologous blood. Although perioperative data are sparse, the current recommendation (based on clinical trial data from the ICU setting) is a transfusion trigger when the haemoglobin level is 7 g/dl (4.4 mmol/l). However patients with known cardiac disease or significant risk factors for cardiac disease were not included in this study. The introduction of leukodepletion and improved storage methods for red cells make translation of these data into current practice difficult. New data in this area are awaited. Although a transfusion trigger of 7 g/dl (4.4 mmol/l) is commonly accepted, it is important to consider this in the context of other risk factors.Glycaemic control?Tight control of blood sugar levels has been demonstrated in a randomised controlled trial to reduce mortality on the ICU. The patient population in this study were predominantly postoperative. These patients received both insulin and glucose with K+ supplementation where necessary.A 69-year-old man with insulin-dependent diabetes mellitus, hypercholesterolaemia, and mild congestive cardiac failure is listed for an emergency laparotomy for peritonitis. There is no time for investigation of his cardiac status beyond ECG and he is taken to theatre immediately. What perioperative interventions are needed to reduce cardiac risk?NoteOptimal perioperative management will reduce cardiac risk as much as possible.Goal-directed therapyMaximising DO2?improves outcomeThe mortality associated with major surgery can be substantially reduced by prior optimisation of circulating volume and adjunctive inotropic agents to improve cardiac output and systemic oxygen supply. Pooling results of the studies discussed above in a meta-analysis can provide additional information about different approaches to this strategy. Commencement of therapy in the preoperative phase, intra-operatively or up to six hours postoperatively seems to provide benefit. However, a study of fixed dose inodilator therapy perioperatively failed to show benefit in the intervention group. A variety of types of cardiac output monitor (pulmonary artery catheter, oesophageal Doppler velocimetry, pulse contour-based technology) have been used effectively to achieve similar results.Similar benefits have been obtained in patients presenting to an emergency department with severe sepsis or septic shock. Benefits are more likely to be realised the earlier optimisation is applied, and if the control group has a high mortality risk. However, not all research supports this approach.Earlier work in patients with established septic shock found either no benefit or?an adverse effect?from use of high dose dobutamine infusions to achieve oxygen delivery goals (see references below for further details).ThinkDiscuss the possible reasons for the divergences noted above with your colleagues when you next care for high-risk patients presenting for surgery or in the early phase of severe sepsis.Is placement of a pulmonary artery catheter mandatory?Fundamental to the process of maximising oxygen delivery, cardiac output or global blood flow is the measurement of a variable reflecting blood flow and titration of therapy to this variable. The majority of studies in this area have used thermodilution through a pulmonary artery flotation catheter (PAFC) to measure cardiac output. The Canadian Critical Care Clinical Trials Group, however, did not demonstrate improvements in outcome with the use of pulmonary artery catheters in high-risk surgical patients. Published studies have also used heating coil-based 'continuous' cardiac output monitoring techniques (via a PAFC), oesophageal Doppler monitoring (ODM) of stroke volume and pulse contour analysis of arterial wave forms to guide perioperative haemodynamic management. While there is still a role for the PAFC there is increasing interest in less invasive techniques.Fluid challengeThe core intervention in perioperative goal-directed studies has been adequate fluid therapy. The optimal strategy for fluid administration is to use a fluid challenge- based regimen. The response of the cardiac output or stroke volume (or CVP if blood flow monitoring is not utilised) to a small increment of intravascular volume expansion (colloid bolus) is used to guide further fluid therapy.Fluid challenge?If the cardiac output or stroke volume increase in response to a fluid challenge, the cardiac filling curve (Starling curve), is on the ascending slope of its compliance curve (A, in figure), further fluid challenges are appropriate. If there is no increase in the flow parameter in response to a fluid challenge (B) this suggests that further fluid challenges would not lead to further increases in flow. A fall in flow in response to a fluid challenge(C) suggests that the intravascular space is becoming overfilled and cardiac efficiency is decreasing with increased filling, therefore no further fluid should be given at that time.Perfusion guided therapyStudies using monitors of tissue perfusion to guide fluid therapy (e.g. gastric tonometry guided therapy) have so far failed to show benefit from this strategy.Beta-adrenoreceptor blockadeSeveral studies have suggested that the use of perioperative β-blockade in patients with risk factors for ischaemic cardiac disease reduces the incidence of postoperative cardiac events and mortality from cardiac causes. However, a recent systematic review and meta-analysis concluded that although this area looks promising there is currently an insufficient evidence base to recommend this for all patients. Retrospective analysis of large clinical databases supports the notion that patients at high risk of cardiac complications receive some benefit, but that for lower risk patients there is no benefit and possibly even harm from perioperative β-blockade.?It is also known that withdrawing long standing β-blockade preoperatively increases the risk of perioperative adverse cardiac events.Care environmentThe care environment is an essential element of postoperative management. Rational use of resources is also very important. Sending someone to a critical care environment for HDU care is an appropriate use of resources, however sometimes surgery needs to proceed in the absence of the necessary beds. In these circumstances it is important to be resourceful e.g. 24-hour recovery, outreach. Perfect intra-operative management is not on its own adequate but needs to be continued into the postoperative phase.AnecdoteA 44-year-old male presented with faecal peritonitis requiring urgent laparotomy. He was rapidly transferred to the operating suite and fluid resuscitated via peripheral cannulae whilst central venous, arterial and pulmonary artery catheters were placed. Oxygen delivey goals (per Shoemaker) were adopted perioperatively and he had a prolonged recovery for six hours in a postoperative care unit. He was transferred to the postoperative ward where blood gases were regularly monitored and fluid resuscitation was continued along with all routine intra-operative care (e.g. normothermia, adequate oxygenation). All abnormal metabolic variables were normalised overnight and he had a successful outcome returning home within seven days.Increasing global blood flow to specific goals has been shown to improve outcome in which of the following groups of patients: cardiac surgery, fractured neck of femur, trauma, major general surgery?How may goal-directed therapy and β-blockade interact?The relative places of goal-directed therapy often involving adrenergic drugs to maximise global blood flow, and β-blockade to diminish adrenergic activity, are not clearly defined. Although β-blockade appears to reduce postoperative mortality this is in a small selected group of patients with multiple risk factors for ischaemic cardiac disease. However, there is also data to support the use of goal-directed augmentation of global blood flow in this same patient group. It may be that the limitation of the cardiac response to hypovolaemia imposed by β-adrenergic blockade results in increased administration of fluids and improved tissue perfusion. At present there is insufficient data to provide firm recommendations in this area.NoteIn general the continuation of preoperative cardiac medications is recommended although some clinicians recommend omitting ACE inhibitor therapy. Beta-adrenoreceptor blockers should not be omitted unless there is a specific clinical reason to do so (see above).CAUTION!?Stopping β-blockers in a patient who is already taking them is likely to be deleterious for them.4/ Understanding perioperative pathophysiologyThere are three pathological processes contributing to perioperative morbidity and mortality.Myocardial ischaemia leading to an increased risk of arrhythmia, infarction and cardiac failure.Hypovolaemia leading to inadequate tissue perfusion and subsequent organ dysfunction due to hypoxic damage or ischaemia reperfusion injury.Impaired cardiorespiratory performance and inability to respond to the increased demands associated with surgery.Although specific interventions exist which appear to reduce the incidence of perioperative adverse cardiac events (e.g. β-adrenergic blockade), the risk of cardiac ischaemia or infarction perioperatively can be reduced by attention to the following aspects of good anaesthetic practice.Maintenance of stable haemodynamicsHypotension may result in inadequate perfusion pressure across critical coronary stenoses leading to ischaemia or infarction. Hypertension causes increased myocardial work leading to ischaemia due to increased oxygen demand.Fluid balanceAvoidance of hypovolaemia reduces sympathetic outflow and ensures an adequate circulating volume available to perfuse the myocardium. Maintenance of adequate tissue perfusion to other tissues (e.g. gastrointestinal tract) also avoids the proinflammatory effects of hypoperfusion and ischaemia-reperfusion.Adequate pain controlMinimising the sympathetic response to surgical stimulus and postoperative pain reduces tachycardia and cardiac work which in turn reduces the risk of ischaemia.Myocardial ischaemiaNoteIf myocardial oxygen demand persistently exceeds supply, ischaemia will arise. Myocardial ischaemia can in turn cause arrhythmia, infarction and cardiac failure.Hypothermia is associated with catecholamine release and has been shown to increase the incidence of perioperative ischaemia in susceptible individuals. Maintenance of adequate oxygenation is clearly also essential to maintain an adequate supply of oxygen to the myocardium.The factors below predispose to perioperative myocardial ischaemia and should be avoided. Perioperative β-blockers may reduce the myocardial ischaemia in patients with ischaemic heart disease. For more information see the PACT module on Acute myocardial ischaemia?Factors that increase myocardial oxygen demand:Tachycardia?increases myocardial demand due to increased rate of work. Also contributes to ischaemia because the period of diastole, during which most coronary flow occurs, is reduced.Shivering?increases oxygen demand due to the increase in mechanical work performed by skeletal muscle.Systemic Inflammatory Response Syndrome (SIRS)Sepsis?and the accompanying inflammatory response lead to hyperdynamic circulation characterised by high cardiac output, tachycardia, low systemic vascular resistance and low mean arterial and diastolic pressures. All of these may contribute to myocardial ischaemia.Magnitude of tissue injury?–?Prolonged, extensive surgery is associated with greater tissue damage which results in a greater oxygen demand associated with tissue healing and the associated inflammatory insult.Endogenous catecholamines?–?An increase in the circulating levels of endogenous catecholamines may be caused by pain or anxiety in the postoperative period. The associated increase in sympathetic activation leads to positive chronotropy and inotropy and hence further myocardial ischaemia.Exogenous catecholamines?–?Inotropic support may be necessary perioperatively. When used appropriately, exogenous catecholamines may improve oxygen delivery. They may, however, also contribute to myocardial ischaemia through the same mechanisms as endogenous catecholamines.Factors that reduce myocardial oxygen supply:Hypoxaemia?–?Inadequate ventilation and oxygenation will lead to hypoxaemia, reducing the oxygen content of blood and hence myocardial oxygen supply.AnaemiaHypotensionCritical coronary stenoses?Endogenous vasoconstrictors?–?Increased sympathetic activationPainAnxiety?Exogenous vasoconstrictorsVasopressorsWhich risk factors, in a patient's history and routine investigations, would you rate as most important as predictors of increased perioperative cardiovascular risk (myocardial infarction, congestive heart failure, death)?When are patients at highest risk of postoperative cardiac events?Hypovolaemia and reduced tissue perfusionNoteAlthough cardiac risk factors have traditionally attracted much attention, hypovolaemia is both common and AVOIDABLE.Hypovolaemia is the commonest avoidable cause of perioperative morbidity. Commonly measured cardiovascular variables (heart rate, blood pressure and arterial and venous pressures) are a poor guide to intravascular volume status. Perioperative compensated hypovolaemia is common and under-recognised. The reduced intravascular volume results in redistribution of blood flow away from 'non-vital' organs resulting in reduced tissue perfusion. Reduced tissue perfusion may cause tissue hypoxia, leading to impairment of function and, for example, gut leak, and ischaemia reperfusion injury and resulting in inflammatory activation.Subsequent development of SIRS and multiple organ dysfunction syndrome (MODS) is dependent upon the magnitude and duration of the tissue hypoperfusion compounded by other pro-inflammatory insults (e.g. trauma, infection). It is increasingly recognised that there is a highly variable inter-individual response to pro-inflammatory stimuli which is probably, to a large part, genetically determined.Cardiorespiratory performanceThe maintenance of tissue oxygenation during surgery is largely determined by the capacity of the cardiorespiratory system to meet the increased demands of the tissues. Pre-existing coronary artery disease is a major determinant of the likelihood of developing myocardial ischaemia but not necessarily reduced cardiac performance. However, pre-existing cardiac failure or functional impairment such that the increased demands of the tissues for oxygen delivery during surgery cannot be met will result in tissue hypoxia and poor outcome. An understanding of the factors in individual patients and the appropriate targeting of therapies to minimise risk of ischaemia whilst maximising oxygen delivery is the key to success.DO2?level predicts poor outcomeThe association between perioperative cardiac output and survival following major surgery was first noted in the 1950s: survivors having higher cardiac output values than non-survivors. From these observations the hypothesis developed that using the cardiac output and oxygen delivery values exhibited by the survivors, as goals for all patients, would reduce overall mortality.Indices of poor tissue perfusion also predict poor outcomePoor global perfusion, suggested by an increase in plasma lactate and the acute development of a metabolic acidosis, or impaired regional perfusion, suggested by, for example, elevated intragastric CO2measured using a gastric tonometer, are associated with adverse outcome following surgery.Explain which patient is at greater risk of worse perioperative outcome: a 48-year-old who can walk one mile on the flat but has ischaemic changes on exercise testing or a 47-year-old with an exercise tolerance of 20 metres but no evidence of ischaemia on ECG?ThinkThere is an apparent conflict between pushing harder to sustain tissue perfusion in the face of a major inflammatory insult and reducing myocardial oxygen demand by β-blockade.5/ Outcome following surgeryMeaningful data on outcome following surgery are hard to find. No single unified European data set exists and national data collection is unusual. The available data suggest that there are marked variations between countries and it is probable that these are at least in part resource related. A comparison of patient outcomes from two hospitals, one in the United States and one in the United Kingdom, found very different outcomes between the two groups.Mortality related to surgery can occur for a considerable period after the surgical procedure itself. Many of the patients who die do so in the first few days following surgery from complications directly attributable to the operation. However, a significant proportion die many days and weeks post surgery following prolonged multiple organ dysfunction/failure related to the initial inflammatory insult at the time of operation. See figure 1.2 Calendar days from operation to death in the following reference.Mortality recording is relatively straightforward but these data alone provide only a limited amount of information regarding the quality of postoperative outcomes; indeed many patients who survive surgery experience significant morbidity associated with prolonged hospital stays. Morbidity occurring after surgery is commonly under-reported. When it is systematically looked for and described it appears to occur very commonly. This morbidity impacts the patients' postoperative quality of life and inflicts further demands on health service resources. In view of this, an accurate method for recording the nature and extent of postoperative morbidity is clearly desirable; however, to date no validated method capable of achieving this exists.?Find out what information is available preoperatively from the potential high-risk patients, and how could you track their postoperative outcomes (e.g. morbidity, in-hospital mortality, readmissions).ThinkPreoperative recognition of high-risk patients and therapeutic interventions to improve their outcome requires close multidisciplinary collaboration. Whom should you involve in your hospital if a clinical pathway in the pre-, peri-, and postoperative phases were to be established for the high-risk surgical patients? What requirements would this impose for the patient care process and infrastructure (e.g. ICU or recovery room, staffing in anaesthesia or ICU)?ConclusionManagement of the high-risk surgical patient requires careful preoperative assessment in order to accurately define the overall risk level and identify specific risk for particular patients and types of surgery. Several systems for scoring risk can be used and objective measurement of exercise capacity is valuable.Perioperative management should be guided by the preoperative assessment. A number of management styles are known to improve outcome and, in particular, fluid management is important.There is some evidence that an augmented level of postoperative care is associated with improved outcome. This can be achieved by admission to a critical care unit, to a high dependency or overnight recovery facility or by an intensive multidisciplinary approach on a surgical ward (critical care without walls).Measurement of outcome following surgery, including systematic recording of morbidity, is likely to drive change and improve outcomes by highlighting best practice and drawing attention to shortfalls in care.Improvement in outcomes of high-risk surgical patients is a success story of modern critical care medicine.Patient challengesA 76-year-old lady is admitted to your hospital?for an elective left hemi-colectomy for carcinoma of the colon. You are the ICU resident on-call. The anaesthesiologist who sees the patient prior to surgery calls you and requests an intensive care bed postoperatively. She tells you that the lady is fit and well, ASA I and walks her cocker spaniel two miles every day. Routine blood tests, chest radiograph and electrocardiogram are normal. There are no specific anaesthetic risks. Hb 9.8 g/dl.Learning issues??Clinical investigation of the high-risk surgical patient?Scoring systems for surgical riskIs this high-risk surgery? Give reasons.Learning issues??ASA I?Good exercise tolerance?High-risk surgeryHow would you prepare the patient for the operation?Learning issues??Optimum intra-operative factors?Interventions influencing specific morbidities/maintenance of normothermiaNo ICU or High Dependency Unit (HDU) bed is available but the surgeon and anaesthesiologist decide to proceed with surgery, with a plan to admit the patient to the 24-hour recovery unit postoperatively. A lumbar epidural is inserted prior to surgery, general anaesthesia induced and a radial arterial line and central venous catheter inserted for invasive pressure monitoring.During the surgery there is some technically difficult dissection. The operation takes three and a half hours and the total blood loss is 1.6 litres. On two occasions during the operation the blood pressure is noted to be labile but the systolic pressure never falls below 80 mmHg. Total intra-operative fluid administered: 5 litres of lactated Ringer's solution, 3.5 litres of succinylated gelatine and 4 units of packed red cells.Learning issues??Care environment?Intra-operative complicationsOn arrival in recovery the patient is breathing spontaneously post extubation with an SaO2?of 95% on an FiO2?of 35% via a variable performance face mask. Her routine cardiorespiratory observations are normal (heart rate 90 bpm, blood pressure 110/75 mmHg, respiratory rate 18/min) but she has a temperature (tympanic) of 35.1?°C and is shivering intermittently. Urine output is 55 ml per hour. Arterial blood gas analysis is as follows: pH 7.3, ABE – 6.2, PaCO2?5.6 kPa (42 mmHg), HCO3???? 20 mmol/l, PaO2?is 12.1 kPa (91 mmHg), Hb is 10 g/dl.Learning issues??PACT module on Basic clinical examinationHow do you interpret these results and what do you conclude?Learning issues??PACT module on Homeostasis?PACT module on Respiratory failureWhat components of perioperative care can be improved in this patient?Learning issues??Pathogenesis of postoperative organ dysfunction/hypovolaemia and reduced tissue perfusion?Maximising DO2?improves outcome?Maintenance of normothermia?OutcomeAfter six hours in recovery and additional treatment including fluid challenges and active surface warming, the temperature has returned to normal and the metabolic acidosis has completely resolved. You discuss with your colleagues the return of the patient to the general surgical ward.?Do you think she should be allowed to go to the ward? Give reasons.Learning issues??Care environmentGiven the critical care referral is there any further assistance the intensive care service can offer?Learning issues??Critical care outreachThe lady returns to the general surgical ward. Two days later she is nauseated and still not tolerating any oral input. Her temperature is noted to have risen to 38.3?°C and the urine output has fallen to 15-20 ml per hour. Heart rate 105 bpm, blood pressure 110/70 mmHg. Blood cultures are taken, antibiotics commenced and 500 ml of colloid solution are administered by the on-call surgical resident. You are called to the ward to discuss the patient???s clinical deterioration. You think she may have sepsis.Learning issues??PACT module on Sepsis and MODSWhat pathological processes are taking place?Learning issues??Sepsis and MODS?PACT module on Sepsis and MODSWhat is the appropriate management?What measures would you take to provide the necessary and optimum organ support necessary?Learning issues??PACT module on Homeostasis?PACT module on Acute renal failure?PACT module on Mechanical ventilationNo ICU bed is available until the following morning. On admission the patient is hypotensive and tachycardic with increased respiratory rate, SaO2?89% on 60% FiO2, and vomiting. She has a 39 day stay with resistant infections, prolonged mechanical ventilation for ARDS, makes a slow recovery and is discharged home after 54 days.Learning issues??OutcomeNotePrevention is better than cureAn 84-year-old man is admitted to the Accident and Emergency department?with a fractured left neck of femur. He has a history of ischaemic heart disease and is taking atenolol, isosorbide dinitrate and aspirin. He gets short of breath on climbing more than one flight of stairs. He is in pain, tachycardic (heart rate 120/min) and anaemic (Hb 8.5 g/dl) with a normal blood pressure but cool peripheries. The 12-lead ECG shows ST depression in the inferior leads.Learning issues??PACT module on Acute myocardial ischaemia?PACT module on Heart failure?PACT module on ArrhythmiaWhat immediate measures are indicated?Is this high-risk surgery? Explain your answer.Learning issues??Specific risk factors?Myocardial ischaemiaFollowing provision of adequate pain relief, intravenous fluids including some blood and oxygen therapy, the ST depression has resolved. The patient is referred to your intensive care unit.?Should he be admitted to the intensive care unit for 'preoptimisation'? Give your reasons.Learning issues??Care environment?PACT module on Basic clinical examinationShould his cardiac medicines be continued during and after the operation? Give reasons.Learning issues??Beta-adrenoreceptor blockadeThe patient is reviewed by the anaesthesiologist who offers epidural pain relief. This was declined by the patient. The anaesthesiologist makes a plan to use general anaesthesia and operate as soon as possible.?What type of perioperative monitoring is appropriate? Why?Learning issues??Cardiac output measurement devices?Maximising DO2?improves outcomeThe patient is continued on all preoperative cardiac medicines. Invasive arterial monitoring is inserted under local anaesthetic prior to induction of anaesthesia that is induced using a balanced technique with minimal haemodynamic disturbance. An oesophageal Doppler probe is inserted and stroke volume maximised using an established algorithm. The stroke volume increased by 20% from start to finish of surgery, without any evidence of myocardial ischaemia. The operation is completed without any haemodynamic instability or ischaemia being recorded. On admission to the high dependency unit after surgery he is extubated, breathing spontaneously with entirely normal cardiorespiratory profile.?How long would you plan to keep him on the HDU?The patient was maintained on the HDU for 24 hours and reviewed by the cardiology team before being transferred to a step-down unit for a further two days where he continued to have ECG and SaO2?monitoring in addition to his regular observations. He was reviewed regularly by the outreach team who were called to see him on three separate occasions for two episodes of ischaemia and one transient episode of atrial fibrillation, all of which responded to simple measures. He left hospital on day 10 having been reviewed by the cardiology team who arranged out-patient follow-up.Learning issues??Myocardial ischaemia?PACT module on Acute myocardial ischaemia?PACT module on Heart failure?PACT module on Arrhythmia?OutcomeOn reflection, proactive use of critical care to prevent predictable sequelae of high-risk major surgery is a more appropriate use of resources than reactive care of preventable problems. There is an apparent dilemma offered by the evidence favouring on the one hand perioperative β-agonist infusion and on the other favouring perioperative β-blockade.What are your views regarding the delays in admission of the first patient to the ICU?Learning issues??PACT module on TransportationDo you think the second patient should have been maintained on the HDU for longer?From this account what conclusions have you come to about the utility of intensive care following high-risk surgery?Q1. Risk factors for major cardiac events following non-cardiac surgery include:Top of FormA. SmokingTrueFalseB. Type II diabetes mellitusTrueFalseC. Heart failureTrueFalseD. Unstable anginaTrueFalseE. Abnormal ECGTrueFalseQ2. The following methods of monitoring cardiac output have been used in randomised controlled trials of goal-directed therapy in the perioperative periodTop of FormA. Pulse contour analysisTrueFalseB. Bolus thermodilution using a pulmonary artery catheterTrueFalseC. Transoesophageal echocardiographyTrueFalseD. Thoracic bioimpedanceTrueFalseE. Oesophageal Doppler aortic velocimetryTrueFalseQ3. Outcome following major surgery has been demonstrated in a randomised controlled trial to be improved by:Top of FormA. Maintenance of a haemoglobin level of >10 g/dl (6 mmol/l)TrueFalseB. Maintenance of tight glycaemic control during surgeryTrueFalseC. Maximising oxygen deliveryTrueFalseD. Beta-blockade of patients undergoing surgery for repair of fractured neck of femurTrueFalseE. Beta-blockade of patients with a positive dobutamine stress test undergoing major vascular surgeryTrueFalseQ4. The following exclude clinically significant hypovolaemiaTop of FormA. Normal blood pressureTrueFalseB. Normal arterial pHTrueFalseC. Normal lactateTrueFalseD. Urine output >1 ml/kgZ-1TrueFalseE. Cardiac index >3 l/min-1TrueFalseQ5. Cardiac outcome following non-cardiac surgery is improved by:Top of FormA. Activated protein CTrueFalseB. Beta-adrenoreceptor blockadeTrueFalseC. Angioplasty of critical coronary stenosesTrueFalseD. Surgical revascularisation of critical coronary stenosesTrueFalseE. Intra-operative thrombolysisTrueFalseBottom of FormBottom of Form ................
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