Frank L. Hanley

Temperature monitoring during CPB in infants: Does it predict efficient brain cooling?

We examined jugular venous oxygen saturation data in 17 pediatric patients less than 1 year of age undergoing hypothermic cardiopulmonary bypass (CPB). Jugular venous oxygen saturations (JvO2SATS) were measured before bypass and during the active core cooling portion of CPB. The study intervals during CPB included 1 minute after initiation of CPB, at a tympanic membrane temperature of 15 degrees C, and at a rectal temperature of 15 degrees C. During these measurement intervals, there were no significant changes in mean arterial pressure, pump flow rate, arterial oxygen saturation, mixed venous oxygen saturation, carbon dioxide tension, or hematocrit. Six of the 17 patients (29%) demonstrated a significantly lower JvO2SAT (87.1% +/- 6.3% versus 98.1% +/- 0.9%) at a tympanic membrane temperature of 15 degrees C. Patients demonstrating jugular venous desaturation could not be predicted from continuous monitoring of tympanic membrane and rectal temperatures or through on-line measurements of mixed venous oxygen saturation. Low JvO2SAT suggests higher levels of cerebral metabolism and cerebral uptake of oxygen. In the presence of deep hypothermic CPB and stable anesthetic levels, the most likely cause of a low JvO2SAT is inadequate cerebral cooling. We believe JvO2SAT monitoring may be an important adjunct to conventional temperature monitoring in the patient undergoing deep hypothermic CPB or total circulatory arrest.

Total anomalous pulmonary venous drainage in newborns with visceral heterotaxy

Children with visceral heterotaxy often present with total anomalous pulmonary venous drainage (TAPVD) associated with univentricular congenital heart disease. We reviewed our experience with the primary surgical management of this lesion under these circumstances. Over a recent 10-year span, 38 patients within the first 3 days of life were admitted to our institution and underwent primary palliation. Twenty-one of them had TAPVD, 18 to a systemic vein. Twelve (67%) of these 18 were seen with obstruction of the anomalous connection and underwent emergency operation. In 7 patients, repair of TAPVD was combined with a systemic-pulmonary artery shunt because of additional obstruction of the pulmonary blood supply, with two deaths. One patient had primary shunting and then repair of TAPVD. Four patients underwent repair of TAPVD alone. Two of them then showed signs of insufficient pulmonary blood flow, received a shunt in a second procedure, and subsequently died. Early mortality in the group with obstructed TAPVD was thus 4 (33%) of 12 patients. Statistical analysis of all 38 patients (univariate analysis, chi 2 testing) showed that neither the presence of TAPVD (p = 0.7) nor TAPVD repair alone (p = 0.8) or with shunting (p = 0.8) was a definite risk factor for early death. The performance of a shunt during the first operation, however, was associated with lower early mortality (p = 0.03). Total anomalous pulmonary venous drainage is a common finding in newborns with visceral heterotaxy. Its presence and its subsequent early repair (requiring cardiopulmonary bypass) do not increase the mortality risk. The need of a concomitant shunt in obstructed TAPVD can initially be underestimated.

Fate of small homograft conduits after early repair of truncus arteriosus

Neonatal repair of truncus arteriosus is being performed in a number of centers, often with the use of small homograft conduits. The fate of the homograft and the risk of replacement were the subjects of this study. Between January 1987 and October 1991, 43 infants aged less than 3 months (range, 3 to 90 days) underwent primary repair of truncus arteriosus including implantation of a valved homograft conduit (diameter, 7 to 12 mm). Twenty-nine had follow-up of more than 6 months (range, 6 to 65 months; mean, 21.9 months). After a mean period of 31 months (range, 8 to 65 months), 7 patients showed obstruction with right ventricular pressures at least 75% systemic and underwent either a conduit change (n = 5) or a patch augmentation (n = 2). Mean cardiopulmonary bypass time at reoperation was 99 minutes; mortality was zero. Five other children are known to have a right ventricular pressure of 50% to 60% systemic, 2 having undergone balloon dilation. Statistical comparison of the patients with conduit reoperation or high right ventricular pressure (n = 12) with the rest of the population (n = 17) revealed an elevated pulmonary artery to right ventricular pullback gradient on postoperative day 1 after the repair (7.7 versus 1.3 mm Hg; p = 0.001) and choice of an aortic over a pulmonary homograft (100% versus 64.7%; p = 0.065) as significant risk factors. Age and weight at repair, postoperative pulmonary artery pressure, length of follow-up, and size of the homograft showed no significant differences between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Maturational and hemodynamic factors predictive of increased cyanosis after bidirectional cavopulmonary anastomosis

Bidirectional cavopulmonary anastomosis (BCA) is thought to be beneficial in the palliation of patients with univentricular congenital heart disease considered at high risk for Fontan repair. Experience with patients undergoing BCA suggested that those who were older or larger at the time of surgery tended to be more cyanotic postoperatively than their younger and smaller counterparts. This study was designed to identify correlates of systemic arterial oxygen saturation after BCA. Specifically, it was postulated that maturational changes in blood flow distribution might be associated with decreasing arterial oxygen saturation. Database records of all 110 patients undergoing BCA at our institution from June 1988 until the end of 1991 were reviewed. Postoperative catheterization data were available for 66 patients. Twenty-one patients were excluded because they had potentially reversible causes of cyanosis yielding inestimable degrees of error in hemodynamic calculations. In the remaining 45 patients, univariate and multivariate regression analyses were used to identify correlates of systemic arterial oxygen saturation. Growth and maturation as represented by body surface area exhibited a highly significant inverse correlation with arterial oxygen saturation (p = 0.005), as did pulmonary vascular resistance (p = 0.003). Patients who underwent BCA when > 3.9 years of age or with body surface area > 0.65 m2 were at significantly increased risk for excessive postoperative cyanosis, defined as systemic arterial oxygen saturation < or = 75% (p < 0.005). The interval between surgery and catheterization correlated directly with arterial oxygen saturation (p = 0.002), indicating a tendency toward earlier study of more cyanotic patients. None of the other variables examined correlated significantly with arterial oxygen saturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Halothane as an anesthetic for fetal surgery

Halothane has become the preferred anesthetic agent during fetal surgery because it can be administered via maternal inhalation and it improves surgical exposure by relaxing the uterus. However, the effects of halothane anesthesia on fetal cardiovascular homeostasis during fetal surgery have not been documented. In 10 pregnant ewes, inhalation halothane anesthesia was administered and their fetuses were instrumented for cardiovascular evaluation. During a 1-hour period we evaluated the acute effects of halothane anesthesia on fetal hemodynamics, arterial blood gases, cardiac output, placental blood flow, total vascular resistance, systemic vascular resistance, and placental vascular resistance. Fetal cardiac output and placental blood flow were determined by the radiolabelled microsphere technique and resistances were calculated using pressure and flow data. These findings were compared to both the results we obtained in 15 fetal sheep anesthetized with the maternal administration of intravenous ketamine, and to the accepted values found in nonanesthetized, chronically instrumented fetal sheep. Our findings indicate that with halothane anesthesia during fetal surgery fetal cardiac output and placental blood flow significantly decrease, and total vascular resistance increases. Placental vascular resistance increases out of proportion to systemic vascular resistance, resulting in the shunting of blood away from the placenta. The combination of decreased cardiac output and increased shunting of blood away from the placenta causes depressed respiratory gas exchange. These findings are not present with other anesthetic agents. Halothane has significant negative effects on both the fetal heart and the peripheral vasculature which disrupt fetal cardiovascular homeostasis. Halothane is a poor anesthetic during fetal intervention.

Preoperative management of neonatal tetralogy of Fallot with absent pulmonary valve syndrome.

In tetralogy of Fallot with absent pulmonary valve syndrome, aneurysmal enlargement of the central pulmonary arteries can be associated with severe bronchial stenosis and respiratory distress in the neonatal period. The ventilatory status of these patients must be stabilized before diagnostic and therapeutic interventions can be performed. This report describes the experience with prone positioning and emergency sternotomy in the preoperative care of a neonate.