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Biomedical subjects

R F Huxtable

Publications and source records attributed to R F Huxtable.

35 records · Page 2Linked to original sources
PubMed1977

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.

Blood Pressure↗
PubMed1977

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.

Ductus Arteriosus, Patent↗
PubMed1977

Tissue oxygen available as a criterion for the effectiveness of continuous positive pressure breathing.

As little as 3-5 cm H2O increase in proximal airway pressure applied to normal lung reduces cardiac output. It is postulated that decreased pulmonary compliance in respiratory distress syndrome (RDS) acts as a barrier thus offsetting this effect. Since cardiac output is not routinely measured, severe reduction in it could accompany regression of disease while maintaining the same airway pressure. This study was undertaken to determine whether tissue oxygen available (O2a) could be used to detect changes in perfusion during continuous positive pressure breating (CPPB). CPPB was evaluated in 10 normal rabbits (CL = 9.5 +/- 1.8 cc/g at 25 cm H2O) and in 10 pulmonary-damaged rabbits (CL = 5.5 +/- 1.4 cc/g at 25 cm H2O) produced by subjecting them to 100% O2. Airway pressure was increased from 0-15 cm H2O in 3 cm H2O increments at 10-min intervals. O2a and PaO2 were monitored continuously. In the normal group, O2a decreased at 3 cm H2O airway pressure, reaching 22% of control at 12 cm H2O, at which pressure PaO2 decreased. Breathing 100% O2 at this airway pressure increased PaO2 to 408 mm Hg, whereas O2a returned to 45% of control. In the experimental group, O2a decreased at 9 cm H2O airway pressure, at 12 cm H2O it was 36% of control at which pressure PaO2 decreased slightly. Breathing 100% O2 at this airway pressure increased PaO2 to 316 mm Hg, and increased O2a to 200% of control. These data indicate that with excessive airway pressure, muscle hypoxia may exist during systemic hyperoxemia and that a low compliance lung exerts a protective effect on O2a. Since changes in cardiac output during CPPB are compliance dependent, and since O2a is perfusion dependent, tissue oxygen available could provide a means of selecting optimal airway pressure during CPPB.

Animals↗
PubMed1977

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.

Cerebral Hemorrhage↗
PubMed1976

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.

Animals↗
PubMed1976

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.

Animals↗
PubMed1976

Extracorporeal membrane oxygenation (ECMO) cardiopulmonary support in infancy.

We have used prolonged extracorporeal membrane oxygenation (ECMO) in the treatment of 13 moribund infants (including 9 neonates), with 4 survivors (3 neonates). Successfully treated cases include post-operative cardiac failure, infant respiratory distress syndrome, massive meconium aspiration, and persistent fetal circulation. All cases have been managed with veno-arterial bypass at flow rates of 80-100 cc/Kg/min. Carotid cannulation for arterial access and careful control of heparin anticoagulation based on whole blood activated clotting time are among the techniques which have contributed to this success. Progressive pulmonary or cardiac failure has been the major problem in older infants, intracranial bleeding is the major problem in neonates. Both of these problems could be minimized by instituting ECMO earlier in the clinical course, but this awaits development of reliable early predictors of mortality.

Blood Coagulation↗
PubMed1975

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.

Animals↗
PubMedDate not supplied

Effect of body weight on gentamicin pharmacokinetics in neonates.

The pharmacokinetics of gentamicin in large-for-gestational-age (LGA) and appropriate-for-gestational-age (AGA) newborn infants were compared in a prospective study. Serum gentamicin concentrations were drawn just before (trough) or after (peak) the third or fourth dose of gentamicin sulfate 2.5 mg/kg given as a 30-minute i.v. infusion every 12 hours to 11 LGA and 12 AGA infants. Peak (Cmax) and trough ( Cmin ) serum concentrations, elimination rate constants (k), volumes of distribution (V), and clearances (CL) were compared between the AGA and LGA groups and within the LGA group between obese (n = 6) and nonobese (n = 5) infants. The serum gentamicin concentrations achieved in the LGA infants were similar to those in the AGA infants, with Cmin values less than 2 micrograms/ml and Cmax values of 4-7 micrograms/ml. The mean pharmacokinetic variables determined were consistent with literature values reported for AGA infants. No significant differences in these variables were observed between the two groups or within the LGA group. Greater variability in Cmax, V, and CL was observed in the LGA group as a whole. The initial dose of gentamicin now recommended for AGA infants should be appropriate for LGA infants. However, serum concentrations should be monitored carefully to detect interindividual variability in pharmacokinetics so that adjustments can be made to ensure therapeutic serum concentrations.

Body Weight↗