Robert F. Huxtable

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.

Dermal heat transport analysis for transcutaneous O2 measurement .

Heat from a transcutaneous oxygen electrode is transmitted locally to the blood beneath it causing a shift in the HbO2 dissociation curve. This increases the local PO2, and allows a measurable PO2, at the skin surface. The temperature effect on the HbO2, curve must be accounted for in in vivo calibration of Ptco2, data. To do this, the capillary blood temperature beneath the electrode must be known. A heat balance is written around the capillary blood with heat being conducted in from the electrode and carried out by two means: conduction to deep tissue; and transport away by the flowing capillary blood. The following equation is the steady state solution of the heat transport problem:

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.

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.

An Improved Sensor and a Method for Transcutaneous CO2 Monitoring

Since CO2 diffuses readily through intact skin along a reasonably short diffusion path, measurement of transcutaneous CO2 (tcPco2) is possible, provided the CO2 consumption of the electrode is minimal and epidermal capillary blood flow and stratum corneum permeability are maintained well.

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.

Low Impedance pH Sensitive Electrochemical Devices That are Potentially Applicable to Transcutaneous PGo2 Measurements

Two classes of low impedance, non‐glass membrane electrodes for pH measurement were evaluated: (I) Metal‐metal oxide electrodes and (II) Reduction‐oxidation electrodes. The fundamental causes of oxygen sensitivity of metal‐metal oxide electrodes were examined and three approaches for its suppression were proposed. For the case of Sb‐Sb2Ox electrodes, 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 its open‐circuit value. The oxygen sensitivity also was observed to be 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.

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.

CONTINUOUS MONITORING OF ARTERIAL PaCO2 BY NON-INVASIVE TRANSCUTANEOUS METHOD

Antimony oxide (Sb-SbOx) and pH-sensitive glass electrodes, combined with reference electrodes, surrounded by electrolyte and covered with gas permeable membrane (gpm) were used for transcutaneous PCO2(PtcCO2) measurement. A servo-controlled heater unit maintained sensor temp, and produced local hyperemia. A thermistor was placed under the gpm to measure true sensor temp. O2 sensitivity of Sb-SbOx electrode was reduced greatly in the 65-175 mm Hg PO2 range by cell loading, but below 65 mm Hg, O2 sensitivity was significant. The pH-sensitive glass electrode was preferred due to its insensitivity to O2. After the sensor was placed on the skin of rabbits, it was calibrated in situ and its temp, coefficient established. This was repeated at the end of the 6-hr. experiment. For the best correlation between PaCO2 and PtcCO2, the skin surface temp, was maintained between 40-42°C, as lower temps, made ptcCO2 higher. Based on in situ calibration, the fitted regression line had a slope of 1.029, intercept of -4.39, and SE of 4.14 mm Hg PCO2. In the range of 21-75 mm Hg, PtcCO2 was 2.2 - 3.8 mm Hg below PaCO2. Based on in situ calibration with one point PaCO2, calibration, the line had a slope of 1.0, intercept of 0.6, SE of 3.4 mm Hg PCO2, and linear regression coefficient of 1.0. These data indicate the usefulness of PtcCO2 monitoring to indicate PaCO2 changes under normal physiologic conditions.