Lectures C5-6 – Minimally Invasive Surgery



Lectures C5-6 – Minimally invasive surgery. Technical background. Basic surgical techniques. Physiology of laparoscopy

Minimally Invasive Surgery = Minimal Access Surgery = Video-Endoscopic Surgery = Magnified Surgery

History of minimally invasive surgery

1706. “Trocar” is first mentioned (trois (3) + carre (side), or trois-quarts / troise-quarts - old French).

1806. Phillipp B. Bozzini (1773-1809) is often credited with the use of the first endoscope. He used a candle as light source to examine the rectum and uterus.

1879. Maximilian Nitze and Josef Leiter invented the "Blasenspiegel” (cystoscope).

1938. A spring-loaded needle was invented by Veres János (1903-1979). Although the „Veress needle” was originally devised to create a pneumothorax, the same design has been incorporated in the current insufflating needles for creating a pneumoperitoneum.

1985. Dr. Erich Mühe of Böblingen, West Germany, performed the first laparoscopic cholecystectomy in 1985 (with a “galloscope”). After nearly 100 succesful operations, a patient died in a complication not related to the procedure itself. German medical leaders declared it „human experimentation” and Mühe was brought to court. The charge was homicide, and he was sentenced.

1987. Phillipe Mouret, in Lyon, is usually credited with the first successful human laparoscopic cholecystectomy (LC). Perrisat, Dubois and colleagues in communication with Mouret, performed laparoscopic cholecystectomies shortly thereafter. In 10 years, the LC became standard technique for cholecystectomy.

The goals of minimally invasive surgery

• To replace traditional, open surgery

• To transfer traditional open techniques into the laparoscopic field

• It is necessary to maintain - and surpass - results and standards achievable by open means

• Surgery undergoes constant evolution: minimally invasive surgery is „cutting edge”

• Future projections: will make up ~70% of compartment surgery (!)

Established procedures (as of 2005)

• Laparoscopic cholecystectomy

• Diagnostic laparoscopy

• Laparoscopic appendicectomy

• Laparoscopic fundoplication

• Laparoscopic Heller's myotomy

• Laparoscopic adrenalectomy

• Laparoscopic splenectomy

Procedures under evaluation

• Laparoscopic hernia repair

• Laparoscopic colectomy

• Laparoscopic nephrectomy for living related donor

• Parathyroidectomy

• Laparoscopic surgery for perforated duodenal ulcer

Robotic surgery

This is truly the cutting edge of surgery. Most common is adult cardiac procedures.

The major benefits are in decreasing the “human factor”, like shaking of hands, hand-eye coordination problems, etc.

• There are two main types of systems: Da Vinci and Zeus.

• Da Vinci: better manipulators

• Zeus: smaller instruments (3 mm)

• Learning curve: first fundoplication took 4.5 hrs surgical time, now 1.5 hrs, with corresponding decreases in setup time.

Foetoscopic surgery

In-utero procedures done laparoscopically. Some of the procedures being performed include:

• Bladder decompression

• Radio ablation of abnormal vessels in twin gestations

• Laparoscopic division of amniotic bands and drainage of hydrothorax

Advantage of minimal access surgery

• Diagnostic + therapeutic procedures

• Better cosmesis.

• Fewer postoperative complications, hernias / infections

• Fewer postoperative adhesions. Main causes

– fewer hemorrhagic complications;

– less peritoneal dehydration;

– lower degree of tissue trauma;

– lower amount of foreign material (sutures).

• Shorter postoperative recovery. Main causes:

– less tissue trauma;

– stress in general is lower

– less postoperative pain

• Patients are able to return to their normal activities faster (6 days).

Mechanism of wound healing is identical (!) – recovery depends on:

o indication (cause of illness)

o healing time of incisions/ports and

– insults of organs and abdominal wall,

– stress caused by general anesthesia

– peritoneal damage

• Faster recovery

– Laparoscopy: 7-14 days

– Laparotomy: 4-6 weeks

• Economical advantage

– decreased hospital stay will decrease surgical costs by 50-60%

– post. op. recovery time after endoscopic surgery can be shortened by 4-6x

Disadvantages of minimal access surgery

• Lack of tactile feedback

• Increased technical expertise required

• Possible longer duration of surgery

• Increased risk of iatrogenic injuries

• Difficult removal of bulky organs

• More expensive

• Non-corrigated coagulation problems

The laparoscope

The term originates from „lapar” (Gr) = "the soft parts of the body between the rib margins and hips” – loin; skopein (Gr) = "to see/ view / examine.

The laparoscopic tower

Parts (in general): 1. monitor (screen), 2. video system (control unit, etc), 3. light source, 4. insufflator ± carbon dioxide cylinder, 5. suction and irrigation, 6. electrocautery device, 7. data storage system. The endoscope and camera are attached to the units of the tower with cables.

Endoscopes - background

• Traditional system. Diameter of lens < length of endoscope. Distance between lenses is large, the light travels through long distances between lenses, light absorbance 90-95% → image is dark.

• B. Hopkins optics (1966)- rod lens system. Space between lenses is filled with glass and air. Light transfer ↑ loss/absorbance ↓ (approx. 70%) → much better image quality

Endoscopes – optical characteristics

a. View

Angle between the of objective and other lenses within the endoscope: determines the direction of the view. In operating endoscopes: 0°-30° - 0°- endoscope: the amount of light forwarded to the ocular is the highest.

b. Field

Between the borders of the image - „how wide is the view"

c. Focus

Increasing / decreasing the magnification either by turning the laparoscope's zooming ring, or by advancing laparoscope toward or withdrawing it from the targeted area. The depth of field of the laparoscope is measured in centimeters: the closer the objective is to the tissue, the shallower the depth of field.

d. Light loss

Hopkins endoscopes > 12 lenses. Only 20%- of the light leaves the ocular part of the endoscope.

Light guide

The illumination is transmitted to the laparoscope via a flexible fiberoptic light guide (180-250 cm long, 0.5-1.0 cm OD). This illumination is essentially cold - most of the lamp heat is not transferred to the laparoscope.

Light source

• Working in a closed environment requires a source of external illumination.

• Currently the 150-300 W fan-cooled xenon light source is used to provide color-corrected light for extended periods of time without overheating.

The video system

• The coupler between the laparoscope and the video camera is equipped with a focusing and zooming ring.

• Camera head: attached to the endoscope, receives the image and transfers to electric signals. The basis of laparoscopic cameras is the solid-state silicon computer chip the CCD (charge-coupled device). (Willard Boyle and George Smith, 1969, Bell Laboratory).

• Control unit: receives the signals of the camera head, converting the optical image into the initial video signal.

• The video sensor (head) can contain 1- or 3-chip sensor. The 1-chip sensor is economical, whereas the 3-chip involves an improved image quality.

• One-chip camera: single CCD sensor, which is responsible for converting the optical image into the initial video signal that is processed and displayed on the video monitor.

• The 3-chip camera has separate red, green and blue sensors for improved color definition, and a RGB connection to the monitor is recommended.

Physiology of laparoscopy. Pneumoperitoneum - background

First used in gynecology; air by hand. Insufflator: closed system for gas insufflation; pressure-controlled device for creating and maintaining pneumoperitoneum.

In addition to the delivery of gas, insufflators have the ability to control the maximal flow rate of the gas and the pressure of gas (< 15 mmHg) within the abdomen.

Intraabdominal pressure (IAP)

• Adult patients: IAP < 15 mmHg

• Pediatrics: < 6 mmHg

Pneumoperitoneum - technique

• Closed technique, Veress needle

• Open: Hasson technique (1971).

• Open technique: morbidity is less, BUT: the type of complications is the same (!)

Physiology of laparoscopy. Example: laparoscopic cholecystectomy

o CO2 at 15 mmHg in healthy patients

o Overall: decrease CO and SV, increase MAP and SVR

o No adverse events

Advantages

o a large, dome-like space is created → displacement of viscera → enabling the surgeon to see and move about the instruments;

o The gas pressure of an established pneumoperitoneum is above the surrounding atmospheric pressure.

o P venous < IAP → control of capillary and venous bleeding

Ideal gas

• Colorless

• Biologically inert

• Absorbed harmlessly and rapidly into the bloodstream

• Does not support combustion

• Cheap

• High flow (> 16 l/min)

CO2

• Not inert, but widely used

• Cheap

• Easily transported

• Alternatives: helium, nitrous oxide

• Warm and humidify the gas to prevent hypothermia and desiccation

Insufflator reading/monitor

o Gas composition

o IAP

o Gas volume and flow rate

o Alarm system that sounds when the pressure exceeds the preset level

o Automatic exsufflation

o Gas:

• Cylinder (50-200 bar pressure)

• Central unit (3.5-5 bar).

o Inlet valve for connection to a gas tank and an outlet port from which sterile plastic tubing is passed to the patient and is used to deliver the gas.

o IAP = average 12 mmHg (1 bar=760 mmHg) → reduction to 50-80 mmHg

o Lowest gas flow (1 l/min) during the initial phase of pneumoperitoneum (introduction of Veress needle).

o IAP < 12-15 mmHg → venous dysfunction.

o IAP > 12-15 Hgmm = CI ↓, gas exchange problems

o Continuously high IAP → organ damage

Hemodynamic complications

o Can die from tension pneumoperitoneum = equivalent to a intraabdominal compartment syndrome

o Decrease in organ function due to decreased microcirculation

o Tension pneumoperitoneum: IAP > 40 mmHg, very restricted CO, potentiated by hypovolemia, dysrhythmias (due to hypercapnia, vagal stimulation)

o Decreased femoral vein pressure → stasis

Circulation

Venous outflow (preload) ↓

CO ↓

HR ↑

MAP ↑

TPR (afterload) ↑

PVR ↑

Hemodynamic changes are more significant in reverse Trendelenburg position AND incidence and risk of deep venous thrombosis is increased.

Trendelenburg / anti-Trendelenburg position: only when the condition is stable, AFTER the pneumoperitoneum.

ABG

o CO2 in systemic circulation: hypercapnia + respiratory acidosis.

o Insufflation: PaCO2 = 8-10 mmHg rise together with a decrease in pH.

o Equilibration:15-20 min after pneumoperitoneum.

Respiratory effects

o IAP ↑: intrathoracal pressure ↓ lung compliance ↑ airway resistance (restrictive syndrome).

o Compression of lower lung lobes (cause: intraabdominal pressure + anesthesia-induced diaphragm relaxation) → lung volumen ↓, dead space ↑ (Trendelenburg position will enhance these effects). Effect likely irrelevant in healthy patients

o Possibility to improve gas exchange: positive end expiratory pressure (PEEP)

Kidneys (excretion)

o IAP ................
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