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P Steer

Publications and source records attributed to P Steer.

At least 19 recordsLinked to original sources
PubMed1999

Glucose production by the human placenta in vivo.

The human placenta transports glucose by facilitated diffusion down a concentration gradient from mother to fetus. It has previously been considered incapable of glucose synthesis. However, recent work has demonstrated the presence in placental tissue of glucose-6-phosphatase, which is required for the final step in the synthesis of glucose. Following continuous intravenous infusion into the maternal circulation of the stable isotope, 6,6-(2)H(2)glucose, during elective caesarean section, we have observed isotope dilution in the umbilical vein, without further dilution in the umbilical artery. Using a mathematical model containing maternal, placental and fetal compartments, the data were compatible with the release of glucose by the placenta. We conclude that the human placenta at term can produce glucose.

Adult↗
PubMed1998

Fetal growth.

Explore the source record for details and available documents.

Animals↗
PubMed1998

Gender does not affect fetal heart rate variation.

There is a widespread but erroneous view among the lay public that there is a difference in the baseline fetal heart rate between male and female fetuses. It has been suggested that this perception might reflect an actual difference in fetal heart rate variability. Therefore, we studied the fetal heart rate variation in 79 white European women using the Sonicaid System 8002 computer. Fourty-four of the fetuses were male and 35 were female. There was no significant gender difference in any measured aspect of fetal heart rate variation.

Adult↗
PubMed1997

Population pharmacokinetics of intravenous caffeine in neonates with apnea of prematurity.

OBJECTIVE: The study the population pharmacokinetics of caffeine after intravenous administration to premature infants with apnea. METHODS: A prospective, blinded parallel study in which daily caffeine citrate doses of 30, 15, and 3 mg/kg were administered over 7 days by intermittent intravenous infusion. Arterial blood samples (three to six per patient) were assayed for caffeine content by means of HPLC. Population pharmacokinetic modeling was performed with NONMEM. RESULTS: Clearance (L/hr) = (0.00000399 . current weight [grams]) + (0.000128 . postnatal age [days]). For gestational age > 28 weeks, volume of distribution (L) = (0.000764 . weight [grams] + (0.0468 . postnatal age [days]); for gestational age < or = 28 weeks, volume of distribution (L) = (0.000755 . weight [grams]) + (0.0224. postnatal age [days]). Interpatient variability (coefficient of variation, in percent) was approximately 25% for clearance and approximately 11% for volume of distribution. Intrapatient error (standard deviation) was 3.9 mg/L. There was insignificant bias between observed and model-predicated serum caffeine concentrations in a separate group of 30 infants. CONCLUSIONS: Caffeine was well tolerated at all doses. Clearance was markedly lower and volume of distribution was higher than the values reported previously for term infants and adults. Both parameters were significantly influenced by postnatal age and current body weight, whereas volume of distribution in infants > 28 weeks' gestational age was higher than that in more premature babies. The predictive performance and the clinical application of the derived population models was satisfactorily shown.

Apnea↗
PubMed1997

Remifentanil versus alfentanil in a balanced anesthetic technique for total abdominal hysterectomy.

STUDY OBJECTIVES: To compare the intraoperative effects and recovery characteristics of remifentanil hydrochloride and alfentanil when administered as part of balanced anesthesia, and to assess the effects of an additional remifentanil infusion administered as analgesic pretreatment before removal of the uterus. DESIGN: Multicenter, double-blind, randomized, parallel-group study. SETTING: Two university hospitals. PATIENTS: 35 ASA physical status I, II, and III women scheduled for elective total abdominal hysterectomy with general endotracheal anesthesia. INTERVENTIONS: Patients were premedicated with midazolam 0.05 mg/kg intravenously (i.v.). Anesthesia was induced with thiopental 2 mg/kg, vecuronium 0.15 mg/kg, and a single dose of opioid over 60 seconds (Pump 1): remifentanil 2 micrograms/kg (Remi/Placebo and Remi/Remi groups) or alfentanil 50 micrograms/kg (Alf/Placebo group). Anesthesia was maintained with a nitrous oxide/oxygen mixture (66:34 ratio) and a continuous opioid infusion: remifentanil 0.25 microgram/kg/min (Remi/Placebo and Remi/Remi) or alfentanil 0.5 microgram/kg/min (Alf/Placebo). At skin incision, a second blinded drug infusion was also initiated (Pump 2): remifentanil 0.25 microgram/kg/min (Remi/Remi) or saline placebo (Remi/Placebo and Alf/Placebo). Intraoperative responses were controlled with single doses of opioid and/or rate titrations via Pump 1. Pump 2 was terminated on removal of the uterus. Pump 1 was terminated at skin closure. MEASUREMENTS AND MAIN RESULTS: The mean (+/- SD) opioid infusion rates administered for the duration of Pump 2 to suppress responses to removal of the uterus were 0.49 +/- 0.27 microgram/kg/min, 1.99 +/- 1.34 micrograms/kg/min, and 0.49 +/- 0.07 microgram/kg/min for the Remi/Placebo, Alf/Placebo, and Remi/Remi groups, respectively. At these rates, similar proportions of patients in the Remi/Placebo (67%) and the Alf/Placebo (60%) groups had responses. Fewer patients had responses in the Remi/Remi group (8%) compared with the Remi/Placebo and Alf/Placebo groups (p < 0.05). The mean total opioid doses used during maintenance were 84.6 micrograms/kg (Remi/Placebo), 393 micrograms/kg (Alf/Placebo), and 68.7 micrograms/kg (Remi/Remi). Awakening times were significantly shorter (p < 0.05) in the remifentanil population compared with the alfentanil population, but discharge times were similar. More patients received naloxone to reverse opioid effects in the alfentanil population (60%) than in the remifentanil population (20%) (p < 0.05). CONCLUSIONS: A mean remifentanil infusion of 0.49 microgram/kg/min is as effective as a mean alfentanil infusion of 1.99 micrograms/kg/min in suppressing intraoperative responses. Doubling of the remifentanil infusion to 0.5 microgram/kg/min before the major stress event improves suppression of responses and lowers intraoperative use of remifentanil without prolonging recovery times. Remifentanil allows faster awakening times than alfentanil, but preemptive administration of postoperative analgesics is recommended to facilitate discharge.

Adult↗
PubMed1995

Relation between maternal haemoglobin concentration and birth weight in different ethnic groups.

OBJECTIVE: To assess the relation of the lowest haemoglobin concentration in pregnancy with birth weight and the rates of low birth weight and preterm delivery in different ethnic groups. DESIGN: Retrospective analysis of 153,602 pregnancies with ethnic group and birth weight recorded on a regional pregnancy database during 1988-91. The haemoglobin measurement used was the lowest recorded during pregnancy. SETTING: North West Thames region. SUBJECTS: 115,262 white women, 22,206 Indo-Pakistanis, 4570 Afro-Caribbeans, 2642 mediterraneans, 3905 black Africans, 2351 orientals, and 2666 others. MAIN OUTCOME MEASURES: Birth weight and rates of low birth weight (< 2500 g) and preterm delivery (< 37 completed weeks). RESULTS: Maximum mean birth weight in white women was achieved with a lowest haemoglobin concentration in pregnancy of 85-95 g/l; the lowest incidence of low birth weight and preterm labour occurred with a lowest haemoglobin of 95-105 g/l. A similar pattern occurred in all ethnic groups. CONCLUSIONS: The magnitude of the fall in haemoglobin concentration in pregnancy is related to birth weight; failure of the haemoglobin concentration to fall below 105 g/l indicates an increased risk of low birth weight and preterm delivery. This phenomenon is seen in all ethnic groups. Some ethnic groups have higher rates of low birth weight and preterm delivery than white women, and they also have higher rates of low haemoglobin concentrations. This increased rate of "anaemia," however, does not account for their higher rates of low birth weight, which occurs at all haemoglobin concentrations.

Africa↗