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Biomedical subjects

M J Peek

Publications and source records attributed to M J Peek.

At least 19 recordsLinked to original sources
PubMed2003

Carbon monoxide disposition and permeability-surface area product in the foetal circulation of the perfused term human placenta.

In order to estimate the placental barrier to gas transfer, a novel carbon monoxide (CO) wash-in method was used to estimate the permeability-surface area (PS) product for the transfer of gas across the foetal circulation in the perfused human term placenta. The PS product for CO was 0.0096+/-0.006 ml/s/g or 0.012+/-0.007 ml/s/g using compartmental or Crone-Renkin analysis, respectively. Using this result and a published estimate of the placental capillary surface area, the permeability coefficient to CO across the foetal circulation was found to be approximately 4 x 10(-5)cm/s. This result is compatible with the hypothesis that the foetal circulation of the human placenta imposes a potentially significant barrier to gas transfer.

Adult↗
PubMed2001

Anticoagulation in pregnancy and the puerperium.

For the management of acute thrombotic events in pregnancy therapeutic doses of low molecular weight heparins (LMWH) may be used, unless the shorter half-life of intravenous unfractionated heparin (UH) and predictable reversibility by protamine are important. Treatment should be continued up until delivery and into the puerperium. Pregnant women who have had an acute thrombotic event should be delivered by a specialist team. In the case of recent thrombosis, delivery should be planned and the time during which anticoagulation therapy is ceased around the time of delivery should be minimised. Therapeutic doses of LMWH contraindicate the use of regional anaesthesia, and a switch to intravenous UH before delivery may allow greater flexibility in this regard. Prophylactic doses of LMWH can be used to reduce the risk of recurrent thromboembolic events in pregnancy. The regimen used will depend on the previous history, the family history and the presence of risk factors, including the genetic and acquired causes of thrombophilia. Women with mechanical heart valves are at high risk during pregnancy and require therapeutic anticoagulation throughout pregnancy under the direction of experienced specialists. Low-dose aspirin can reduce the risk of recurrent pre-eclampsia by about 15%, but the role of UH and LMWH in the prevention of recurrent miscarriage or obstetric complications associated with uteroplacental insufficiency is still uncertain.

Anesthesia, Obstetrical↗
PubMed2001

Drugs in pregnancy. Drugs for obstetric conditions.

For many reasons, including the fear of fetal anomaly, the recognition of pregnancy being a normal physiological process and maternal choice, few drugs are prescribed and used during pregnancy. Nevertheless, there are certain common obstetric conditions that are associated with significant maternal and perinatal morbidity and mortality where drugs play an important and necessary part in treatment. These conditions include termination of pregnancy, threatened preterm labour, induction of labour and post-partum haemorrhage. This chapter deals with the role of drug therapy in these obstetric scenarios. A large amount of obstetric clinical trial research has been dedicated to the management of these conditions.

Abortifacient Agents↗
PubMed2001

Lethal prenatal onset infantile cortical hyperostosis (Caffey disease).

We describe a sporadic case of lethal prenatal onset infantile cortical hyperostosis (Caffey disease), which resulted in early postnatal death at 30 weeks gestation. The mother presented with antepartum haemorrhage and preterm labour. She was found to have polyhydramnios. The infant showed extensive symmetrical diaphyseal subperiosteal cortical thickening throughout the skeleton with short extremities. Hepatomegaly and lung hypoplasia were present. Currently, in the absence of a specific marker, diagnostic ultrasound offers the only prospect of prenatal diagnosis. This diagnosis should be considered in infants with short angulated long bones, where the diaphyses are irregular and echodense, and where there is no sign of fractures.

Fatal Outcome↗
PubMed1999

Transplacental flecainide therapy for fetal supraventricular tachycardia in a twin pregnancy.

We present the case of a twin pregnancy in which 1 fetus developed hydrops secondary to supraventricular tachycardia at 30 weeks' gestation. Transplacental flecainide administration successfully treated the condition without evidence of maternal or fetal side-effects. The case raises ethical and possibly legal issues that present when 1 fetus in a twin pregnancy develops a condition the management of which could cause complications to the other twin and/or the mother.

Adult↗
PubMed1998

Maternal-to-fetal transfer of thyrotropin-releasing hormone in vivo.

OBJECTIVE: Our purpose was to determine the transplacental transfer of thyrotropin-releasing hormone at the time of fetal blood sampling. STUDY DESIGN: Four hundred micrograms of thyrotropin-releasing hormone was given intravenously to 13 pregnant women between 24 and 35 weeks' gestation and maternal-to-fetal transfer of thyrotropin-releasing hormone was determined at fetal blood sampling 1 to 93 minutes later. The fetal thyrotropic response to thyrotropin-releasing hormone was determined by measuring thyroid-stimulating hormone, thyroxine, and prolactin. For comparison, endogenous fetal and maternal levels of thyrotropin-releasing hormone, thyroid-stimulating hormone, thyroxine, and prolactin levels were determined in a further 20 patients undergoing fetal blood sampling between 19 and 35 weeks' gestation. The concentration of thyrotrophin-releasing hormone was measured by radioimmunoassay and thyroid-stimulating hormone, thyroxine, and prolactin by chemiluminescence assay. RESULTS: Thyrotropin-releasing hormone was undetectable in the maternal circulation, whereas endogenous levels were detectable in the fetus from 19 weeks' gestation (median 150; range 50 to 276 pmol/L) and did not correlate with gestational age. After thyrotropin-releasing hormone injection as an intravenous bolus, peak levels in the mother were attained at 3 minutes (50,000 pmol/L). Maximal transplacental transfer of thyrotropin-releasing hormone occurred within 5 minutes of maternal administration but accounted in fetal blood for only 0.01% of initial dose administered (median 250; 30 to 550 pmol/L). Thyrotropin-releasing hormone-stimulated fetal peak thyroid-stimulating hormone levels occurred within 13 minutes and were higher than maternal values (p < 0.001). There was no change in fetal prolactin level with thyrotropin-releasing hormone therapy. CONCLUSION: Although maternally administered thyrotropin-releasing hormone crosses the placenta sparingly, it still elicits a thyroid-stimulating hormone but not a prolactin response in the human fetus.

Adult↗
PubMed1997

Medical amnioreduction with sulindac to reduce cord complications in monoamniotic twins.

OBJECTIVE: Cord entanglement is a common complication of monoamniotic twins and it is associated with high perinatal mortality. Apart from preterm delivery, no treatment has previously been used to reduce the risks of this complication. We postulated that reducing amniotic fluid volume would stabilize fetal lie and reduce the risk of cord compression. STUDY DESIGN: Cord entanglement was documented in three cases of monoamniotic twins in the midtrimester. Sulindac was administered to the mother. Amniotic fluid index, fetal urine output, and umbilical artery and ductus arteriosus Doppler waveforms were investigated before and during treatment by use of real-time and pulsed Doppler techniques. RESULTS: Sulindac was associated with a dose-related reduction in amniotic fluid index and fetal urine production without alteration in fetal flow velocity waveforms. Fetal lie stabilized after commencement of treatment. All six twins were delivered with no complications. CONCLUSION: Medical amnioreduction with sulindac is a new management option in monoamniotic twins to reduce cord complications.

Amniotic Fluid↗
PubMed1997

Pharmacokinetics and pharmacodynamics of TRH during pregnancy.

OBJECTIVE: To determine the pharmacokinetics and pharmacodynamics of thyrotropin-releasing hormone (TRH) in pregnant women. METHODS: Twenty-four pregnant and eight nonpregnant women were given 400 micrograms TRH as either intravenous infusion or bolus. Serial venous samples were collected for TRH, TSH, thyroxine, and prolactin assay. RESULTS: When given as bolus, mean (+/- standard error of the mean) peak plasma concentration (50 +/- 5.2 and 73 +/- 5.1 ng/mL, P < .01), elimination half life (4.3 +/- 0.3 and 6.3 +/- 0.4 minutes, P < .001), and area under the curve (156.4 +/- 14.8 and 340.1 +/- 32.8 ng/mL/minute, P < .001) in pregnant subjects were reduced compared with controls, whereas plasma clearance (45.4 +/- 6.5 and 23.6 +/- 2.1 mL/kg/minute, P < .01) and volume of distribution (27.8 +/- 1.8 and 19.0 +/- 1.3% body weight, P < .01) were increased. When given by infusion, steady-state concentration (6.6 +/- 0.5 and 9.8 +/- 0.9 ng/mL, P < .01) and elimination half-life (4.6 +/- 0.5 and 6.3 +/- 0.3 minutes, P < .05) were lower in pregnant subjects than in controls. Thyrotropin-releasing hormone kinetics were independent of mode of administration. Although basal TSH and thyroid hormone concentrations were similar in patients and controls, the TSH response to TRH was blunted in pregnant subjects compared with controls (9.3 +/- 0.6 and 16.4 +/- 1.4 microIU/mL, P < .001). The basal (3187 +/- 488 and 147 +/- 16 mIU/L) and maximal prolactin response (6193 +/- 426 and 1316 +/- 106 mIU/L) were increased in pregnant subjects compared with controls (P < .001). CONCLUSION: The peak plasma concentration and elimination half-life of TRH are reduced during pregnancy because of the increased volume of distribution and rapid clearance. Mode of administration does not affect TRH pharmacokinetics, but the maternal pharmacodynamic response differs in patients receiving bolus compared with infusion.

Adult↗
PubMed1997

Activated protein C resistance in normal pregnancy.

This prospective cross-sectional (10 women on each occasion) and longitudinal (20 women) study investigated activated protein C (APC) ratio in normal pregnancy. The APC ratio was measured at booking, 20, 30 and 36 weeks of gestation, and compared with a sample of normal nonpregnant women. No significant difference was found between APC ratios for pregnant women at any gestation and those of the nonpregnant population in either the longitudinal or cross-sectional studies. There was a significant decrease in APC ratios throughout pregnancy, but in all but one case values remained within the normal nonpregnant range. The APC ratio can therefore be used as a screening test for the factor V Leiden mutation during pregnancy.

Biomarkers↗
PubMed1996

Reverse end-diastolic flow in the middle cerebral artery: an agonal pattern in the human fetus.

Serial Doppler ultrasonography in a severely growth-restricted fetus revealed progressive reduction in pulsatility index of the middle cerebral artery, consistent with brain-sparing effect. At 29 weeks, 1 week before fetal death, the pulsatility index in the middle cerebral artery returned to normal values and became reversed the day before fetal death. This report suggests that reverse flow in the middle cerebral artery is one of the terminal hemodynamic events preceding fetal death.

Blood Flow Velocity↗
PubMed1996

Umbilical vein to artery ratio in fetuses with single umbilical artery.

In fetuses with single umbilical artery (SUA) the entire blood flow to the placenta is transported through only one umbilical artery, resulting in a compensatory increase of the arterial diameter. In order to establish whether umbilical vessel size could be used as an additional ultrasonographic criterion for prenatal diagnosis of SUA, we measured umbilical vein and umbilical artery diameters in 55 fetuses with SUA and in 55 with a normal three-vessel cord matched for gestational age. In all but one fetus with SUA, the diameter of the umbilical artery was greater than 50% of that of the umbilical vein, resulting in an umbilical vein to umbilical artery ratio of < or = 2. In contrast, none of the fetuses with a three-vessel cord had a ratio of < or = 2. Increasing diameter of the umbilical artery with no modification of the diameter of the vein is a characteristic prenatal ultrasonographic feature of SUA, making this observation a useful technique for the detection of this vascular anomaly in utero.

Female↗
PubMed1996

Rectal carcinoma in pregnancy.

Rectal carcinoma is an uncommon malignancy in pregnancy. Described below is the case report of a patient with rectal carcinoma diagnosed in pregnancy. together with a review of the current literature. When rectal carcinoma is diagnosed at greater than 20 weeks' gestation the timing and mode of delivery became the major obstetric management decisions. The approaches to these problems are outlined in this report.

Adenocarcinoma, Mucinous↗
PubMed1995

Maternal and neonatal outcome of patients classified according to the Australasian Society for the Study of Hypertension in Pregnancy Consensus Statement.

OBJECTIVE: To outline the maternal and perinatal features and outcome of patients referred to a tertiary referral obstetric hospital for management of their hypertension. SETTING AND PATIENTS: 205 consecutive public patients admitted for assessment of hypertension (either full admission or day-stay) to King George V Hospital's Hypertension in Pregnancy Unit, between February 1993 and January 1994. DESIGN: A prospective study in which patients were classified according to the Australasian Society for the Study of Hypertension in Pregnancy (ASSHP) Consensus Statement classification. RESULTS: Of the 205 patients, 25% did not meet the criteria for pre-eclampsia or chronic hypertension, 33% had mild pre-eclampsia, 34% had severe pre-eclampsia and the remainder had chronic hypertension. The mean gestation at delivery for those with mild pre-eclampsia was 38.3 weeks and for severe pre-eclampsia 35.3 weeks. For the mild and severe groups respectively, the rate of elective delivery for raised blood pressure was 56% and 53%; for caesarean section, 17% and 61%; and for perinatal death, 2% and 4%. In the severe group, 49% had fetal problems and 25% required intravenous antihypertensives. CONCLUSIONS: The multisystem nature of pre-eclampsia makes comparison of management protocols difficult. Ongoing audit is needed of maternal and perinatal outcomes and features of disease in patients with hypertension in pregnancy under a universal classification. The ASSHP classification system successfully identifies patients who require more intensive management and intervention.

Chronic Disease↗
PubMed1995

Antenatal lung maturation--should we all be using thyrotropin-releasing hormone?

Thyrotropin-releasing hormone (TRH) appears to be a promising antenatal therapy to help reduce neonatal lung disease. Clinical trials, however, show differing results. At present the optimum dosage, frequency and method of administration have not been established. TRH has been shown significantly to elevate blood pressure in patients with preeclampsia suggesting it should not be used in this group. Moreover concerns over its use in growth retarded fetuses and its long-term neonatal effects have not been addressed. Further trials are needed before routine clinical use can be recommended.

Fetal Organ Maturity↗