Biomedical subjects
Publications and source records attributed to R H Phibbs.
Management of perinatal asphyxia is one of those rare opportunities in clinical medicine when death or life-long disability can be prevented with several minutes of skillful and judicious action. Fetal and neonatal asphyxia is approached most successfully as a joint obstetric, pediatric, and anesthetic effort. This article reflects the team approach to perinatal asphyxia.
Umbilical artery catheter use in sick newborns has been associated with infarction of major organs such as the intestine and kidneys; spinal cord infarction has also been reported but is rare. We report two cases of spinal cord infarction and review the six others in the literature for preventable or predisposing conditions. Infusion of blood and hypertonic solutions, shock, and high position of the catheter tip were associated with infarction of the anterior spinal cord in these infants.
Clinical and billing data were collected on all admissions to six California newborn intensive care units during a 6-month period. Charges were adjusted to costs using Medicaid cost to charge ratios and for inflation, and patients were classified by the diagnosis-related group (DRG) system. Costs were from 97% to 708% more than the proposed DRG reimbursement levels. Regression analysis showed that DRGs explained 22% of the variation in costs. An alternative model using binary variables to control for birth weight, assisted ventilation, surgery, survival, multiple births, and mode of discharge explained 42% of the variation in costs. In contrast to other proposed DRG alternatives, this simple model does not require special training or subjective decision-making.
Erythropoietin, hemoglobin, hematocrit, oxygen affinity (P50), and reticulocyte counts were measured weekly starting at 1 week of age in 10 very-low-birth-weight infants and on a single occasion in 15 healthy men. In the adults, "available oxygen" (derived from oxygen carrying capacity and P50) averaged 13.1 ml/dl blood and the mean erythropoietin level was 15.2 mU/ml. Erythropoietin levels in the infants were inversely related to concentration of hemoglobin, P50, and available oxygen. However, despite the much lower mean "available oxygen" of 9.3 ml/dl in the infants compared with that in adults (P less than 0.001), the mean erythropoietin value of 8.2 mU/ml in the infants was less than in adults (P less than 0.001). Furthermore, the erythropoietin response to decreased "available oxygen" was lowest in the least mature infants. VLBW infants often develop clinical evidence of hypoxia during the anemia of prematurity. The relatively low erythropoietin levels in relation to "available oxygen" are compatible with a decreased erythropoietin response to hypoxia compared with that in adults. Such a difference in response could be a contributing factor to the anemia of prematurity.
The purpose of this study was to determine whether an inappropriately low erythropoietin response in premature infants might be a basis for the anemia of prematurity. Erythropoietin was measured by radioimmunoassay in conjunction with hemoglobin and reticulocyte count in untransfused premature infants between birth and 60 days of age. The 27 infants had a mean gestational age of 31 weeks and a mean birth weight of 1378 gm. Between 2 and 30 days, mean erythropoietin concentration was 9.7 mU/ml, significantly and substantially lower than 15.2 mU/ml in 15 concurrently studied healthy adults (P less than 0.01). Subsequently, from 30 to 60 days, values rose gradually to a mean of 17.2 mU/ml, which did not differ significantly from the mean value in adults. Hemoglobin values fell from a mean of 12.9 gm/dl during the first month to 9.0 gm/dl between 30 and 60 days. Thus, during the second postnatal month, preterm infants had essentially the same erythropoietin values as in adults despite a mean hemoglobin concentration that averaged less than two thirds the adult value. This failure to mount a greater erythropoietin response may help to explain why hemoglobin declines to such low values at 2 months of age.
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A clinical syndrome of transient maculopapular rash with associated eosinophilia, thrombocytopenia, and mild lymphopenia developed in 21 of 35 (60%) neonates receiving both intrauterine transfusions and postnatal exchange transfusions, and six of 17 (35%) neonates receiving multiple exchange transfusions for erythroblastosis fetalis. This syndrome did not develop in infants who received intrauterine transfusions without exchange transfusions or single exchange transfusions without prior intrauterine ones. Patients with this rash and associated laboratory abnormalities did not progress to acute or chronic graft-vs-host disease, and on follow-up examinations were alive and well.
To understand the sources of the high costs of neonatal intensive care, financial and medical information on 1,185 admissions to an intensive care nursery was gathered. Multiple regression analysis showed that a significant portion of the variation in individual costs was explained by three measures of risk: low birth weight, surgical intervention, and assisted ventilation. There was a highly skewed distribution of costs. Nearly half of all admissions had none of the above risk factors, had an average cost of about $2,000, and accounted for only 13% of the total costs for the whole sample. In contrast, less than one quarter of the admissions had two or more of the risk factors, had an average cost of $19,800, and accounted for nearly 60% of the total costs. Models that predict costs and length of stay on a basis of seven risk factors were developed to allow for differences in patient populations.
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We used a new, rapidly responding in vivo catheter oximeter to continuously measure arterial oxygen saturation (Sao2) in 34 newborns with cardiopulmonary disease. The Sao2 was compared with the oxygen tension (Pao2) of blood sampled through the catheter in 2 groups. We evaluated the oxygen dissociation curves of 24 untransfused infants whose hemoglobin F (HbF) concentration was greater than or equal to 80%. We also examined the Sao2 curves of 20 extensively transfused infants who had greater than or equal to 80% hemoglobin A (HbA). We found a wide variation in Sao2 at levels of arterial Po2 between 30 and 90 mmHg. Although the oxygen dissociation curve of the transfused group was significantly to the right of the untransfused group, there was considerable overlapping between the 2 curves. This dispersion reflected the wide range of clinical states encountered in newborns with cardiopulmonary disease, and the changes in blood oxygen affinity. In some newborns, when Pao2 was less than 50 mmHg, Sao2 could be > 90% whereas in others, Sao2 could be < 75%. When both Pao2 and Sao2 were low, Sao2 reflected arterial oxygen contents more precisely because of the shape of the individual oxygen dissociation curves in both groups. Opinions vary as to the safe upper limit of Pao2 at which retrolental fibroplasia does not occur. The Sao2 at 2 upper limits of Pao2 (100 and 80 mmHg) was estimated by probit analysis of simultaneous measurements of Pao2 and in vivo Sao2. In both the untransfused and extensively transfused groups of newborns, Pao2 was < 100 mmHg when Sao2 was < 96%. The Pao2 was < 80 mmHg, when the Sao2 was < 92%, if the HbF was greater than equal to 80%, and when Sao2 was < 91%, if HbA was greater than equal to 80%, (95% confidence limits). The findings suggested a caveat against the practice of calculating Sao2 from measurements of pH, Pao2, and Paco2. This can be quite inaccurate when taking samples of arterial blood from newborns.
We measured amniotic fluid surfactant by the semiquantitative foam stability test within 24 hours before delivery of 410 infants, 64 of whom developed HMD diagnosed by standard criteria. When surfactant titers were ranked in eight categories, they predicted graded risks of HMD. On this basis we defined five "risk groups" with significantly different incidences of HMD (I = 0.5%; II = 10%; III = 25%; IV = 41%; V = 79%). Infants in Groups I and II were heavier and more mature than those in Groups III to V. However, among infants of equivalent GA or birth weight, the incidence of HMD still correlated significantly with the foam test results. Within each risk group the incidence of HMD was equal among infants delivered by vagina and by cesarean section, slightly greater among males than females, and inversely proportional to GA. In Group V the incidence of HMD was 100% among infants at less than 33 weeks' GA. We used this relationship to devise a system that improved prediction of HMD by combining the foam test results with GA.
We measured the in vivo oxygen saturation of hemoglobin in the arterial blood of 34 sick newborn infants with a new, rapidly responding, continuously recording, catheter oximeter. The oxygen saturation, SaO2, was found to fluctuate between 85 and 95% in infants with pulmonary disease who are in a stable condition and breathing spontaneously. Severe disaturation occurred during apnea and after procedures such as chest percussion and suctioning of the endotrachael tube. The effects of changes in respiratory therapy were quickly manifested by changes in SaO2. This was particularly useful in guiding resuscitation of newborn infants who were asphyxiated at birth. Blood sampling for measurement of PaO2 can be done less frequently, reducing the need for blood transfusions in small infants.
Improved accuracy of continuous arterial oxygen tension (PaO2) measurement is obtained if allowance is made for the response time of the electrode. Recalibration is necessary only when PaO2 measured in a blood sample differs from the electrode value by more than +/- 11.5 mmHg (1.5 kPa).
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We measured the residual placental blood volume (RPBV) of 20 infants delivered at term by cesarean section of women not in labor. In all cases, the umbilical cord was clamped within 40 seconds of birth. RPBV decreased significantly with increasing age at cord clamping. In addition, RPBV for infants with cords clamped within 20 seconds of birth correlated inversely with maternal systolic blood pressure (mean RPBV = 54.8 ml. per kilogram at 105 torr and 28.4 ml. per kilogram at 148 torr). However, RPBV did not correlate with maternal blood pressure for the whole group of 20 infants or for those with cords clamped later than 20 seconds after birth. These data indicated that in infants delivered by cesarean section placental transfusion is time related during the first 40 seconds of life and that maternal blood pressure also influences the magnitude of placental transfusion during the first 20 seconds after birth. Analysis of data from this study combined with data from a previous study shows that after 40 seconds the net flow between placenta and infant reverses and that cord clamping delayed beyond this point is accompanied by a rise in RPBV back to the level found when the cord was clamped before 20 seconds.
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