Vasopressin
Action: Increases SVR + MAP, decreases CI, PAP usually unchanged or decreased. Urine output increased/no change.
Indication: Ventricular fibrillation, catecholamine – resistant septic / hyovolaemic shock or excessive vasodilation post-CPB.
Preparation: 1 ampoule Pitressin = arginine vasopressin 20U
Administration: Central IV administration preferable. Endotracheal / intraosseous also effective, dose as for IV bolus.
Infusion: 1U/ml in 60ml syringe. (3 ampoules vasopressin in N/saline)
Dose: Hypovolaemic shock:
Refractory shock: (Hypotension despite adequate preload + catecholamines, exclusion of tamponade / tension pneumothorax/ionised Ca++ <0.8mmol/l) Consider bolus 1-10U for severe hypotension. Commence infusion at 0.1U/min., wean down to 0.04U/min then stop. Hypovolaemic cardiac arrest: bolus 40U.
Post-CPB vasodilation:
Infuse at 0.1U/min. initially, titrate downwards as tolerated following catecholamine reduction to 0.04U/min before ceasing.
Septic shock:
Infuse at 0.04U/min. Higher doses may be associated with increased side effects. Titrate down as tolerated.
Side Effects: Possibly less common in shock than in other clinical settings (as may be vasopressin deficient).
Gastric hypoperfusion: bowel ischaemia / raised liver enzymes / reduced platelet count.
Higher doses: myocardial ischaemic. Hyponatraemia. Cutaneous necrosis from extravasation. Allergy.
Dr. Paul Forrest, 2004