Effects of polycythemia and hyperviscosity on cutaneous blood flow and transcutaneous PO2 and PCO2 in the neonate.

Neonatal hyperviscosity syndrome is known to affect multiple organ systems. The effects of polycythemic hyperviscosity on cutaneous blood flow and transcutaneous PO2 and PCO2 were compared in ten term infants prior to and following correction of the hyperviscous state. Cutaneous blood flow was measured by the heat clearance method; transcutaneous PO2 and PCO2 were detected by a polarographic O2 cathode and a potentiometric pH-sensitive glass electrode, respectively. Whole blood viscosity was measured at five shear rates from 11.25/s to 225/s using a Wells-Brookfield viscometer. Following partial exchange transfusion with fresh frozen plasma, there was a significant decrease in arterial blood hematocrit from 62.7% +/- 5.9% to 48.4% +/- 4.8% (P less than .001) and in whole blood viscosity from 13.9 +/- 2.9 cps to 8.5 +/- 1.8 cps (P less than .001) at a shear rate of 11.25/s. The arterial and transcutaneous O2 and CO2 tensions were in the normal range in the hyperviscous state and remained unchanged following exchange transfusion. The static measure of cutaneous blood flow increased 36% from 208 +/- 54 mW to 283 +/- 75 mW (P less than .01) while the dynamic measure of cutaneous blood flow increased 38% to 41% (P less than .01). The lack of demonstrable cutaneous hypoxia and hypercapnia, despite a significant decrease in blood flow in the hyperviscous state, may be due to one or more factors.

Extracorporeal circulation (ECMO) in neonatal respiratory failure.

Sixteen moribund newborn infants with respiratory failure were treated with extracorporeal membrane oxygenation (ECMO) for 1 to 8 days. Cannulation via the right jugular vein and carotid artery was used to establish venoarterial-cardiopulmonary bypass. High flow (80 percent of cardiac output) allowed decreasing FIO2 and airway pressure. Diagnoses and results were as follows: respiratory distress syndrome, four patients (two improved, one survived); meconium aspiration syndrome, eight patients (four improved, three survived); persistent fetal circulation (some with diaphragmatic hernia), four patients (three improved, two survived). Intracranial bleeding occurred in 43 percent, accounting for most of the deaths. In a parallel series of 21 infants treated with conventional ventilator therapy, the mortality rate was 90 percent and intracranial bleeding occurred in 57 percent. ECMO provided life support and gains time in newborn respiratory failure. In high mortality risk infants, the rate of survival is higher and intracranial bleeding lower with ECMO than with optimal ventilator management.

Priapism in preterm infant.

This report of transient priapism in a preterm newborn with respiratory distress syndrome discusses clinical course, therapy, possible etiologic factors, and previously reported cases in newborns. Possible causes include use of arterial catheter, red cell transfusion, hemodynamic changes from a patent ductus arteriosus, and hypoxia.

Prospective application of an index of neonatal necrotizing enterocolitis.

Fifty-five patients were scored 1 to 3 according to the criteria: the character of stools, abdominal findings on palpation, x-ray evidence of pneumatosis intestinalis, the development of pulmonary insufficiency, and the duration of symptoms to positive x-rays. Fifteen patients with scores of less than five were considered to have subclinical NEC with one late death. Twenty-nine of 30 patients with scores of 5-10 responded to medical management with 2 deaths related to recurrent bouts of sepsis without recurrent NEC. Eleven patients required surgery with index scores of 10-14 with 6 deaths occurring uniformly in those patients with scores of 12 or more. Two patients were scored inappropriately low due to the lack of the passage of a stool for analysis. One patient with a score of 4 did not pass a stool but had the other diagnostic criteria for the single false negative of the series. This index correctly determined the severity of NEC of 53 of 55 patients, identified the patients who required surgical intervention and predicted survival.

Management of pulmonary insufficiency in diaphragmatic hernia using extracorporeal circulation with a membrane oxygenator (ECMO).

Persistent fetal circulation (PFC) causes severe pulmonary insufficiency in patients who have demonstrated adequate lung function following diaphragmatic hernia repair. Patent ductus arteriosus (PDA) ligation corrects this condition, but carries the risk of sudden right ventricular failure. Pharmacologic reversal of PFC may be attempted, and if unsuccessful, prolonged venoarterial bypass becomes necessary to provide effective pulmonary support. PDA ligation can then be performed safely and maturation of the pulmonary vasculature allowed to occur. Pulmonary artery pressure monitoring is essential.

Technical aspects in the management of the meconium aspiration syndrome with extracorporeal circulation.

Sixteen neonatal patients diagnosed as having the meconium aspiration syndrome were selected for management with extracorporeal circulation with a membrane oxygenator (ECMO) with 8 survivors over 4 yr. All patients weighed greater than 2 kg. Each was placed in the 100% mortality group according to a Neonatal Pulmonary Insufficiency Index (NPII) based on hourly pH and FiO2 determinations. The typical patient course on ECMO was stabilization for the first 12 hr then improvement on high bypass flow rates for 12-24 hr to maintain a pAO2 for 50-60 mm Hg with minimal ventilator settings with an FiO2 of 0.3-0.4. Bypass flow rates were reduced to maintain adequate pAO2 with similar ventilator settings for another 24 hr. Survivors were taken off bypass and decannulated while on similar ventilator settings. Nonsurvivors did stabilize or improve but usually exhibited symptoms of intracranial hemorrhage by 48 hr. Intracranial hemorrhage appeared to be related to the degree of prebypass acidosis. Successful ECMO support reduced the expected mortality from severe meconium aspiration from 100% to 50%. Early institution of ECMO, before acidosis worsens, seems to be indicated to reduce the morbidity of conventional ventilator management and to prevent intracranial hemorrhage from severe prebypass acidosis. Long term followup indicates that these patients have progressed satisfactorily according to developmental testing for as long as 4 yr.

Pulmonary artery pressure monitoring in persistent fetal circulation (PFC).

The use of the Swan-Ganz catheter to monitor pulmonary artery pressure in adults with cardiopulmonary failure has become commonplace. Our meager experience was with four neonates diagnosed as having persistent fetal circulation monitored by the use of this PA catheter. Tolazoline was infused directly into the pulmonary circulation via the catheter. Pulmonary artery pressure was temporarily reduced by tolazoline administration, with a marked increase in PaO2. More experience is required to define the role of the Swan-Ganz catheter in neonatal physiologic monitoring.

Ligation of the patent ductus arteriosus in newborn respiratory failure.

Patent ductus arteriosus (PDA) is commonly associated with respiratory disease in newborn infants and may require ligation. Surgical ligation of the PDA can be done in small infants with low operative risk and minimal complications. The outcome of patients after ligation depends primarily on the severity of the underlying pulmonary disease. One hundred fifty-one patients have undergone ligation in an eight-year period at this center. A simplified technique performed in the neonatal intensive care unit with the use of local anesthesia and conventional ventilator management is described.

Cardiopulmonary changes following 24-36 hours of hyperoxia.

Cardiopulmonary variables were studied in rabbits breathing room air following 24-36 h of 100 percent 0-2 exposure. Initially, arterial pH and P-co-2 remained within normal limits while arterial P-0-2 decreased significantly. Cardiac output and oxygen consumption increased significantly. Static lung compliance was decreased, and histologic examination showed pulmonary hemorrhage, atelectasis, and adema. Myocardial function under these conditions was restored, and the myocardium was able to produce a compensatory increase in cardiac output. Therefore, changes in myocardial function, as related to oxygen toxicity, are reversable phenomena.

Electrochemical sensor for continuous transcutaneous PCO2 measurement.

A sensor suitable for continuous transcutaneous PCO2 measurements is described. The sensor consists of an antimony-antimony oxide electrode in combination with a silver-silver chloride reference electrode, bathed in an electrolyte and covered by a Teflon membrane. A servo-controlled heater unit was used to maintain the sensor's temperature and to produce local hyperemia. The resulting oxidation-reduction potential under constant temperature is a linear function of the logarithm PCO2. Response time (95%) to step changes in PCO2 from 27 to 70 mmHg was 2.7 +/- 0.3 min. Following a 12-h "aging" time, the electrode exhibited a minimal drift of 5.2 +/- 2.2 mV for 16 h, representing an average PCO2 drift of 0.5 mmHg/h. This sensor was applied on three rabbits and on five human volunteers, and found satisfactory under normal physiological conditions.

Low impedance pH sensitive electrochemical devices that are potentially applicable to transcutaneous PCO2 measurements.

Two cases of low impedance, non-glass membrane electrodes for pH measurement were evaluated: (I) Metal--metal oxide electrodes and (II) Reduction-oxidation electrodes. The fundamental cause of oxygen sensitivity of metal-metal oxide electrodes were examined and three approaches for its suppression were proposed. For the case of Sb--Sb2Ox electordes, oxygen sensitivity can be attenuated partially by cell loading, either directly across the reference electrode or indirectly across a third slave electrode. In a PO2 range of 8--54 kPa, more than 95% of the PO2 response can be suppressed by loading the cell emf to half of tis open-circuit value. The oxygen sensitivity also was observed to diminished by grinding the metal-metal oxide and pressing it under high pressure into a pellet electrode. Other metal-metal oxide electrodes that have promise in transcutaneous measurement are the Pd-PdO2 electrodes. The redox electrodes are typified by the Quinhydrone electrode. A membrane Quinhydrome electrode showed a sensitivity of 56 mV/Decade at 37 degree C and no oxygen sensitivity up to 50 kPa and a drift of 1 mV/h over a 24-h period. However, the stability deteriorated over a long-term period.

Effect of umbilical artery catheters on blood flow and oxygen supply to extremities.

The effect of catheter placement in the abdominal aorta on the blood flow and oxygenation of lower extremities was evaluated in 30 New Zealand rabbits, weighing 0.55-3.5 kg, by inserting 3.5 and 5.0 French polyvinyl chloride catheters, of the type commonly used for umbilical artery catheterization, through the femoral artery, advancing 15-20 cm, and leaving in place for 10-30 min. Arterial blood pressure (BP), common iliac artery blood flow (BF), gracilis muscle tissue oxygen availability (O2a), and subcutaneous temperature (T) in the foot were continuously monitored before and during catheter placement and after withdrawal. There were no changes in the physiologic variables measured in the contralateral leg when the catheter remained below the aortic bifurcation; however, when the catheter was advanced 15-20 cm into the abdominal aorta, a decrease in lower extremity BF, O2a, and T occurred. Because the length of catheter insertion was maintained constant in each animal, the decreases in BF, O2a, and T are related to the relative dimensions of the vessel and the catheter. The ratio of catheter to vessel diamter, in addition to the site of catheter placement, should be considered during the clinical application of arterial catheters. Reduction in blood flow could be detected by continuous differential monitoring of core and extremity temperature or extremity muscle oxygen availability.