Effect of Pco2-adjusted pH on the neonatal heart during hypothermic perfusion and ischemia

Postischemic functional recovery in immature hearts is influenced by performance index and assessment technique

In the in vivo immature heart, conflicting results are reported for postischemic functional recovery. This study determines whether interpretations of functional recovery are influenced by the contractile performance index (systolic pressure, developed pressure, and maximum rate of systolic pressure increase per unit time) reported or the assessment technique (isovolumetric and variable-volume) utilized. In neonatal pigs (n = 6) on cardiopulmonary bypass, each performance index was examined using both assessment techniques before myocardial ischemia and at 15, 30, and 60 min of reperfusion. With the use of the isovolumetric technique, all performance indexes had significantly different recovery. With the use of the variable-volume assessment technique, recovery of systolic pressure was significantly better than the other indexes. When recovery was compared between the two assessment techniques, systolic pressure recovered significantly better when assessed using the variable-volume technique. For each performance index, the correlation between isovolumetric and variable-volume techniques was positive before ischemia but negative during reperfusion, suggesting that the assessment techniques identified conflicting postischemic contractile performances. Thus both the contractile performance index reported and the assessment technique employed are ultimately important in interpreting postischemic functional recovery in the immature heart.

Perioperative effects of alpha-stat versus pH-stat strategies for deep hypothermic cardiopulmonary bypass in infants

OBJECTIVES

In a randomized, single-center trial, we compared perioperative outcomes in infants undergoing cardiac operations after use of the alpha-stat versus pH-stat strategy during deep hypothermic cardiopulmonary bypass.

METHODS

Admission criteria included reparative cardiac surgery, age less than 9 months, birth weight 2.25 kg or more, and absence of associated congenital or acquired extracardiac disorders.

RESULTS

Among the 182 infants in the study, diagnoses included D-transposition of the great arteries (n = 92), tetralogy of Fallot (n = 50), tetralogy of Fallot with pulmonary atresia (n = 6), ventricular septal defect (n = 20), truncus arteriosus (n = 8), complete atrioventricular canal (n = 4), and total anomalous pulmonary venous return (n = 2). Ninety patients were assigned to alpha-stat and 92 to pH-stat strategy. Early death occurred in four infants (2%), all in the alpha-stat group (p = 0.058). Postoperative electroencephalographic seizures occurred in five of 57 patients (9%) assigned to alpha-stat and one of 59 patients (2%) assigned to pH-stat strategy (p = 0.11). Clinical seizures occurred in four infants in the alpha-stat group (4%) and two infants in the pH-stat group (2%) (p = 0.44). First electroencephalographic activity returned sooner among infants randomized to pH-stat strategy (p = 0.03). Within the homogeneous D-transposition subgroup, those assigned to pH-stat tended to have a higher cardiac index despite a lower requirement for inotropic agents; less frequent postoperative acidosis (p = 0.02) and hypotension (p = 0.05); and shorter duration of mechanical ventilation (p = 0.01) and intensive care unit stay (p = 0.01).

CONCLUSIONS

Use of the pH-stat strategy in infants undergoing deep hypothermic cardiopulmonary bypass was associated with lower postoperative morbidity, shorter recovery time to first electroencephalographic activity, and, in patients with D-transposition, shorter duration of intubation and intensive care unit stay. These data challenge the notion that alpha-stat management is a superior strategy for organ protection during reparative operations in infants using deep hypothermic cardiopulmonary bypass.