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4800600-34290000Bradycardia and PacingSinus bradyFitColdDrugs- β-blockers, CCBs, digoxinSick-sinus syndromeHypothyroidismHeart blocks1st degreeProlonged PR interval >0.2s 2nd degreeMobitz I (Wenkebach)Progressive PR prolongation until a beat is droppedMobitz IIPR interval is constant, dropped beat randomly3rd degree (complete)Complete dissociation between P waves and QRS complexesPacingMobitz IICompleteTreatmentIs the patient compromised?Chest painHypotensionAltered LOCCCFAtropine 0.5mg-1.5mg IV q 15 minutesPacingIf pacing not available considerIsoprenaline 10-20mcg IV followed by infusion (may exacerbate hypotension)Adrenaline 10-20mcg IVAssociated with MIIn inferior MI is usually transientIn anterior MI is usually permanent and a poor prognostic indicator- need pacingLife-Threatening Drug Toxicitiesβ-blockers OverdoseHighest risk with propranolol (widens QRS and seizures) and sotalol (prolongs QT)PR prolongation may be the earliest signMay have associated hypoglycaemiaAtropine is only temporisingRx= high dose insulin euglycaemic therapy (1u/kg IV insulin followed by 1-2u/kg/hr infusion with 10% dextrose)QRS widening rx= sodium bicarbonateQT prolongation rx= magnesium, isoprenaline, overdrive pacingGlucagon is no longer commonly usedCalcium channel blocker OverdoseHighest risk with verapamil and diltiazemMay be associated with hyperglycaemiaDecontamination is a priorityCharcoal if within 1 hour of ingestion for standard preparations, or 4 hours for extended release preparationsWhole bowel irrigation after charcoal in extended release preparationsRxCalcium chloride 10% 20ml or calcium gluconate 10% 60mlAtropine is temporisingHigh dose insulin euglycaemic therapyDigoxin ToxicityDifferentiate acute (supratherapeutic ingestion) v chronic (normal doses in patients with dehydration/ renal or hepatic impairment)Levels are more useful in chronic than acute toxicity (although a level over 15 predicts lethality in acute ingestions)Predictors of lethality in acute ingestion ingested dose (more than 10 mg in adults, more than 4 mg in children)cardiac arrestpotassium concentration above 5.0 mmol/Llife-threatening ventricular arrhythmiasdecompensation (hypotension) from bradyarrhythmiasAtropine is temporising, pacing is rarely effective, and tachyarrhythmias often resistant to cardioversionRx= Digibind (Fab freagments) – suggested resource – “Tox Handbook” (Elesevier). Tox Reg (Page 8333)Acute HD stable = 5 vialsAcute HD unstable = 10 vialsAcute cardiac arrest = 20 vialsChronic = 2 vialsHaemodialysisTreat hyperkalaemia aggressively with insulin-dextrose and sodium bicarbonate. There is a theoretical risk of “stone heart syndrome” with calcium administration but this is not based on more than case reports.Transcutaneous PacingIndicationsbradycardia unresponsive to drug therapy3rd degree heart blockMobitz type II second-degree heart block when haemodynamically unstable or operation plannedoverdrive pacing for Torsades (due to prolonged QT)not likely to be effective in asystole (can trial if clear reversible cause)Set intial milliamps (mA) and desired rate to 70Start pacing and increase the mA looking for electrical capture and then feeling for mechanical captureOnce captured set mA 5-10 above the capture threshold ................
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