Barry V. Kirkpatrick

Alveolar-Arterial oxygen gradients versus the neonatal pulmonary insufficiency index for prediction of mortality in ECMO candidates

Current selection criteria necessary for intelligent application of extracorporeal membrane oxygenation (ECMO) in hypoxic neonates remains controversial. Both the Neonatal Pulmonary Insufficiency Index (NPII) and serial alveolar-arterial oxygenation gradient measurements (A-a)Do2 have been recommended. Accordingly, an analysis of 50 consecutive severely hypoxic neonates was undertaken to assess the predictive value of (A-a)Do2 determinations and NPII in discriminating survivors from non-survivors. These infants with meconium aspiration syndrome (MAS), congenital diaphragmatic hernia (CDH), or persistent pulmonary hypertension of the newborn (PPHN) required maximum mechanical ventilation for hypoxia. Pharmacologic manipulation of pulmonary vascular resistance was attempted in 83%. If postductal (A-a)Do2 remained greater than or equal to 620 torr despite 12 hours of maximum medical therapy, mortality was 100%; however, 35% of nonsurvivors were unfortunately excluded. (A-a)Do2 greater than or equal to 600 torr for 12 hours demonstrated 93.8% mortality, and only 12% of all mortalities were thus excluded. Among nonsurvivors successfully hyperventilated, the NPII could not predict mortality. Ideal selection criteria must exclude those who would otherwise survive without ECMO, yet allow early accurate identification of the neonate certain to die. It would appear that serial (A-a)Do2 determinations best permit this identification and thus orderly application of ECMO.

Clinical use of an extracorporeal membrane oxygenator in neonatal pulmonary failure

Pulmonary failure is the most frequent cause of mortality in newborns, accounting for 15,000 deaths yearly. It may be the result of the respiratory distress syndrome (RDS), meconium aspiration syndrome (MAS), or persistent fetal circulation (PFC), including infants with congenital diaphragmatic hernia (CDH). Early identification of patients with predictably fatal but potentially reversible respiratory failure refractory to conventional management protocols would permit orderly application of extracorporeal membrane oxygenation (ECMO) as a final resuscitative measure. Eight neonates with severe pulmonary failure manifested by A-a DO2 of greater than 620 torr for greater than 12 hr, persistent cardiovascular instability, and relentless progression of acidosis and hypoxemia were predicted to have a 100% mortality in spite of maximal medical therapy. Four patients presented with MAS and 4 others had PFC, including 2 with CDH. All were supported with ECMO using the internal jugular vein and common carotid artery for access to the right atrium and aortic arch. Following support for 77-313 hr, 6 were successfully weaned from ECMO and then from the ventilator. In these few patients the use of extracorporeal membrane oxygenation after exhaustion of standard therapy was accomplished safely and successfully without untoward short-term sequelae. Extracorporeal ventilatory support may purchase the critical time necessary for resolution of the underlying parenchymal disease, including the pulmonary hypertension associated with CDH.

Renal tubular acidosis type 4 in neonatalunilateral kidney diseases

Three neonates, two with unilateral renal vein thrombosis and one with unilateral dysplastic kidney, developed type 4 renal tubular acidosis, manifested by nonazotemic hyperkalemic metabolic acidosis with alkaline urine pH and reduced potassium excretion. Normal plasma concentrations of sodium, aldosterone, and renin activity, together with normal renal fractional excretion of sodium, supported the diagnosis of renal tubular acidosis type 4, subtype 5. Arginine HCl loading studies showed that despite their ability to bring the urine pH to

579 GROWTH OF PREMATURE INFANTS FED WHEY DOMINANT FORMULA WITH MEDIAN CHAIN TRIGLYCERIDES (MCT) AND EOLYCOSE

Previous work has shown that premature infants may not optimally utilize lactose and long chain triglycerides (LCT), both of which are found in standard infant formulas. To enhance growth, one group of well premature infants was fed an experimental formula prepared by Ross Laboratories (Group I). The experimental formula contained 7.26 g/d1 CHO (50% lactose, 50% polycose) and 3.65 g/d1 fat (50% MCT, 50% LCT). Group II infants were fed PM 60/40 (Ross) containing 6.88 gm/dl CHO (100% lactose) and 3.65 gm/d1 fat (coconut and corn oil). Both formulas contained modified cows milk protein (60% whey,40% casein).Volumes fed (cc/Kg/day) were similar in each group.At 7, 14, 21 and 28 days, growth, as measured by weight gain and head circumference (HC), was similar in each group. Growth in the first 28 days of life was not enhanced by feeding formula with MCT and polycose in these study patients.

182 PERIPHERAL ARTERIAL INFUSIONS: HISTOLOGIC FINDINGS

Historically, heparinized NS has been used in peripheral arterial lines. The use of dextrose in these lines could potentially increase total daily calories in the critically ill neonate. A study was undertaken to examine the histologic effects of peripheral arterial catheter placement and continuous fluid infusion. Teflon catheters (24g) were placed by surgical cutdown technique into peripheral paw arteries of 20 anesthetized pups. Timed (8h) infusions with the assigned fluid (D5W, D10W) at 2cc/h were used, with control arteries placed to heparin lock or infused with heparinized NS. Arteries were resected, preserved in formalin, then examined histologically (H&E stain) by the pathologist (blinded to specimen fluid group). One or more abnormalities were noted in 73% of the 80 arterial specimens examined.Conclusions: Focal tissue trauma occurs with catheter placement into small peripheral arteries. There was no histologically identifiable difference between control and dextrose infusion groups (p=0.8005). These results suggest that further investigation is needed to determine the safety of arterial dextrose infusion and the long term effects of catheter trauma in peripheral arteries.

613 EFFECT OF INCREASED ZINC INTAKE ON SERUM ZINC LEVELS IN PREMATURE INFANTS

Previous studies have shown that zinc levels decrease during the first month of life in premature infants. An attempt was made to raise zinc levels by increasing the oral intake in one of two groups of premature infants who were matched for birth wt x = 1440 gm, gestational age x = 31.3 wks, onset and volume (cc/Kg/day) of feedings and caloric intake (k cal/Kg/day).Group I received 1.00 mg Zn/dl of formula while Group II received 0.40 mg Zn/dl of formula. Zinc levels were obtained on study day 0 and every 7th day for 4 weeks and determined by atomic absorption spectrophotometry.Serum albumin, total protein and alkaline phosphatase levels were similar for each feeding group at each time period as was growth, as measured by weight, length and head circumference gains. Despite a 2.5 fold increase in zinc intake in Group I, serum levels were similar to that of control infants. Factors other than zinc intake must govern the level of zinc in the growing premature infant.