Angiotensin II concentrations and gut mucosal perfusion in infants undergoing cardiopulmonary bypass

Effect of preoperative angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker use on hemodynamic variables in pediatric patients undergoing cardiopulmonary bypass

BACKGROUND

Some have suggested that children undergoing cardiac surgery who receive angiotensin-converting enzyme (ACE) inhibitors experience a greater degree of hypotension after anesthesia induction and in the immediate postcardiopulmonary bypass period than children who did not receive these drugs. Therefore, we examined the effect of ACE inhibitor/angiotensin II receptor blocker (ARB) therapy on intraoperative hemodynamics and vasopressor use in pediatric patients undergoing cardiac surgery.

METHODS

In a retrospective cohort study of patients younger than 18 years who underwent cardiopulmonary bypass between March 1, 2010, and April 1, 2011, we compared intraoperative hemodynamics and vasopressor use between patients who received preoperative ACE inhibitor/ARB therapy and those who did not. The primary outcome was vasoactive infusion score after cardiopulmonary bypass.

RESULTS

The occurrence of hypotension did not differ significantly between the ACE inhibitor/ARB group and the control group during induction of anesthesia or at any time point after cardiopulmonary bypass. At 0, 30, 60, and 90 minutes after cessation of cardiopulmonary bypass, patients on ACE inhibitor/ARB therapy tended to have a higher vasoactive infusion score (7.1, 7.6, 9.4, and 11.3) than patients in the control group (6.3, 6.1, 6.0, and 6.7). Although this difference became more pronounced over time, it did not reach statistical significance.

CONCLUSION

The use of preoperative ACE inhibitors and ARBs in pediatric patients undergoing cardiac surgery did not significantly increase the incidence of hypotension after induction of anesthesia and did not increase significantly the vasoconstrictor requirements upon weaning from cardiopulmonary bypass; however, additional prospective studies are needed.

Postoperative management in patients with complex congenital heart disease

Life-threatening problems occur in the neonate and infant after cardiac surgery because of the interplay of diminished cardiac output (CO), increased metabolic demand, inflammatory responses to cardiopulmonary bypass, and maladaptive responses to stress. Therefore, the postoperative management of patients with complex congenital heart defects is directed at optimization of oxygen delivery to maintain end-organ function and promote wound healing. Traditionally, assessment of circulation in the postoperative congenital heart patient has depended on indirect assessment of CO using parameters such as blood pressure, pulses, capillary refill, and urine output. Because of the limitations of indirect and observer-dependent assessment of CO, we rely on objective measures of tissue oxygen levels for the complex postoperative patient. We have found that continuous monitoring of the mixed venous saturation (SvO2) allows for identification of acute changes in systemic oxygen delivery and frequently precedes other indicators of decreased CO. The postoperative patient can be expected to have a period of decreasing CO, and the need for intervention should be anticipated because critical low output syndrome will develop in a subset of patients. Strategies for postoperative care are developed based on the diagnosis and procedure, but optimizing SvO2 is a consistent goal. A uniform approach to airway maintenance, vascular access, and drug infusions, all universal concerns during the perioperative period, minimizes the potential for these predictable and necessary interventions to result in morbidity or mortality. Management of the postoperative single ventricle patient targets stabilization of the systemic vascular resistance through the use of vasodilators to improve systemic perfusion and simplify ventilator management. Management of any individual patient should be driven by objective analysis of available data and must include efforts to re-evaluate the treatment plan as well as to identify unanticipated problems.