Management of low systemic vascular resistance hypotension following CPB. a comparative study between low dose vasopressin and norepinephrine

ABSTRACT

Post-cardiopulmonary bypass [CPB] low systemic vascular resistance [SVR] hypotension is attributed mainly to CPB activated systemic inflammatory response together with long CPB duration, long-term preoperative use angiotensin-converting enzyme [ACE] inhibitors or beta blockers, and inappropriate low vasopressin secretion. Vasopressin is a potent vasoconstrictor in various hypotensive states including post CPB vasodilatation. The aim of the present study was to compare the effects of low dose vasopressin infusion with norepinephrine on systemic hemodynamics, myocardial performance, internal mammary artery [IMA] graft blood flow, renal function, and clinical outcome. In patients undergoing elective on-pump coronary artery bypass grafting [CABG], hemodynamic variables were measured after weaning from CPB, and patients who had SVR < 800 dyne.s.cm-5, and systolic systemic blood pressure [SBP] < 80 mmHg or mean systemic blood pressure [MAP] < 60 mmHg despite proper volume resuscitation were enrolled in the study and were randomly allocated into 2 groups with 15 patients in each group. These patients received either vasopressin at 0.01-0.1 U/min [VP group], or norepinephrine at 0.01-0.2 microg/kg/min [NE group] to maintain MAP >70 mmHg. Hemodynamic variables were measured before; 1, 4, and 12 hours after the start of study drugs. Blood flow through IMA graft was measured before and 1 hour after infusion of the study drugs. Creatine kinase MB [CK-MB] serum concentrations were obtained immediately after surgery and at 24 hours and 48 hours postoperatively. Arterial lactate concentrations were measured before and at 1, and 4 hours after the start of study drugs. Serum creatinine was measured before and 24 hours and 48 hours after the start of the study drugs. Urine output was measured before and 4 hours after the start of the study drugs. The duration of vasopressor infusion and complications such as stroke or tachyarrhythmias were recorded. Extubation times, intensive care unit [ICU] and hospital length of stay were also recorded. Vasopressin compared to norepinephrine caused a significant increase in Cl, LVSWI, and postoperative urine output together with significant decrease in HR, postoperative CK-MB, duration of vasopressor infusion, and shorter extubation time. Both drugs resulted in a significant increase in MAP and SVR, a significant decrease in arterial lactate, together with non significant change-in IMA blood flow, postoperative serum creatinine, ICU and hospital length of stay, and the incidence of postoperative complications. low dose vasopressin infusion was found to be a valuable alternative to norepinephrine in management of low SVR hypotension after CPB