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Biomedical subjects

V Walker

Publications and source records attributed to V Walker.

At least 37 records · Page 2Linked to original sources
PubMed1991

Association of hypovolemia after subarachnoid hemorrhage with computed tomographic scan evidence of raised intracranial pressure.

Hypovolemic patients are more likely to suffer delayed cerebral ischemia and infarction after a subarachnoid hemorrhage (SAH). Prompt recognition and correction of hypovolemia may improve the outcome. We have identified computed tomographic (CT) scan findings that increase the probability of a patient presenting with hypovolemia soon after an SAH. The plasma volume (PV) of 25 patients admitted within 96 hours of an SAH was measured using radioiodinated serum albumin. The normal PVs were measured in an outpatient setting 6 months later or predicted from their total body water. Nine patients (36%) were found to be hypovolemic, defined as a fall in PV exceeding 10% of the normal PV (mean fall, 18 +/- 2%). Sixteen patients were normovolemic or hypervolemic (mean PV, +9 +/- 2%). The basal cisterns were compressed or obliterated on the CT scans of all hypovolemic patients compared with 12.5% of normovolemic patients (chi-square, 14.52; P less than 0.01). The probabilities of a patient being hypovolemic if the CT scan indicated raised intracranial pressure were high: hydrocephalus, P = 0.80; compression of the basal cisterns, P = 0.82; and compression of the basal cisterns associated with intracerebral hematoma or midline shift, P = 1.00. Patients with an SAH and radiological evidence of raised intracranial pressure should be considered at particular risk for systemic hypovolemia.

Adult↗
PubMed1991

When disaster strikes. The concerns of staff nurses.

1. This study determined how involvement with an earthquake affected patient care delivery and ascertained what nurses need to continue providing safe and efficient care in future disasters. 2. Although 60% of the staff had experienced a previous disaster, the literature described that learned coping does not automatically "transfer" to present loss experiences. 3. Providing staff with debriefing sessions and other support groups is helpful in the post-trauma period. At all levels, there is a need to communicate concerns and to be involved in disaster drills and other disaster preparedness sessions.

Adaptation, Psychological↗
PubMed1990

Combined epidural and general anesthesia for abdominal aortic surgery.

The hypothesis that combined epidural and light general anesthesia for infrarenal abdominal aortic surgery is associated with a more stable intraoperative course and less postoperative morbidity than general anesthesia alone was tested. The authors compared intraoperative hemodynamic variables and postoperative morbidity between a group with combined epidural and general anesthesia (n = 30) and a group with general anesthesia (n = 19). Patients who had combined epidural and general anesthesia were given epidural bupivacaine intraoperatively and epidural morphine postoperatively. After cross-clamping of the aorta, cardiac index and pulmonary capillary wedge pressure did not change in the group with combined epidural and general anesthesia, whereas cardiac index decreased (mean change, 0.30 L/min/m2; P = 0.0006) and pulmonary capillary wedge pressure increased (mean change, 1 mm Hg; P = 0.007) in the group with general anesthesia. After unclamping, cardiac index increased in both groups (mean change, 0.26 L/min/m2, P = 0.002, and 0.30 L/min/m2, P = 0.001, respectively). Postoperatively, the necessity for ventilatory support and the incidence of respiratory failure were lower in the combined epidural and general anesthesia group than in the general anesthesia group (P = 0.0002 and P = 0.018, respectively). In addition, vasodilator therapy was required less frequently in the group with combined epidural and general anesthesia (P = 0.002). Duration of intensive care unit stay was shorter in the combined epidural and general anesthesia group (2.7 days v 3.8 days, P = 0.003). These data indicate that for infrarenal abdominal aortic surgery, combined epidural and general anesthesia is associated with more stable intraoperative hemodynamics and significantly less postoperative morbidity than general anesthesia alone.

Adult↗
PubMed1990

Effect of hydrocephalus on prostaglandins and thromboxane B2 in ventricular cerebrospinal fluid.

The concentrations of prostaglandin F2 alpha, prostaglandin E2, 6-ketoprostaglandin F1 alpha (prostacyclin metabolite), and thromboxane B2 were assayed in ventricular cerebrospinal fluid obtained from 28 patients with hydrocephalus (17 obstructive, 11 communicating). Seven patients received dexamethasone or hydrocortisone on the day of sampling. No patient received nonsteroidal anti-inflammatory compounds for 48 hours before sampling. The median values did not differ significantly between the two types of hydrocephalus or from the concentrations in lumbar cerebrospinal fluid obtained from patients without intracranial pathology during lumbar myelography for possible lumbar disc disease. Hence, there is no evidence that eicosanoids accumulate in the ventricles in hydrocephalus, and it is unlikely that they have a significant role in its symptomatology.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Metabolism of intravenous phenylalanine by babies born before 33 weeks of gestation.

Random urine samples collected weekly from 22 infants of 25-32 weeks of gestation were analyzed by capillary gas chromatography-mass spectrometry to define the normal organic acid profile. Increased excretion of phenolic acid derivatives of phenylalanine and tyrosine was found in 21 samples from 13 babies during established parenteral nutrition. Compared with 53 samples collected during milk feeding, phenyllactic acid, 4-hydroxy-3-methoxyphenyllactic acid, and N-acetyltyrosine were excreted significantly more often and 4-hydroxyphenyllactic and 4-hydroxyphenylpyruvic acids at significantly higher concentrations. The mean daily intake of phenylalanine (197 mg/kg) was significantly higher and that of tyrosine (22 mg/kg) significantly lower during parenteral nutrition. Three cyclohexanediol isomers were identified which might have derived from phenylalanine or one of its metabolites.

Chemical Phenomena↗
PubMed1990

Urinary excretion of cyclohexanediol, a metabolite of the solvent cyclohexanone, by infants in a special care unit.

Using gas chromatography-mass spectrometry, we investigated the urinary excretion of organic acids of 278 newborn babies in a special care unit to obtain reference data and monitor metabolism. In 101 of 584 urine samples analyzed, we found isomers of cyclohexanediol. trans-1,2-Cyclohexanediol was always most abundant, with small amounts of 1,3- and 1,4-cyclohexanediol and, sometimes, traces of cis-1,2-cyclohexanediol. Glucuronide conjugates were not detected. The probable source was the solvent cyclohexanone, which was found as a contaminant of intravenous dextrose and the parenteral feeding solution, and was also leached into the infusion fluids from the administration set. We recovered 0.89 mg (range 0.74-0.98 mg, n = 5) of cyclohexanone from 150 mL of dextrose pumped through the infusion apparatus over 24 h, the normal rate for a 1-kg premature baby. Although this is well below toxic doses reported for mature animals, more data are needed for the newborn, particularly preterm infants who have a decreased capacity for glucuronide conjugation.

Cyclohexanes↗
PubMed1989

3-Methylisoxazol-5-one, an artefact from acetoacetic acid formed during urinary organic acid analysis.

During the analysis of urine for organic acids for suspected metabolic disorders by solvent extraction, derivatisation and capillary gas chromatography, unaccountably large lactic acid peaks were observed in some samples containing large amounts of acetoacetic acid. Electron impact mass spectrometry showed that this was due to two unknown compounds coeluting with lactic acid. These were found to be two trimethylsilyl derivatives of 3-methylisoxazol-5-one, produced from acetoacetic acid during oximation with hydroxylamine hydrochloride, by a cyclisation reaction. Awareness of the formation of this previously unreported artefact is important to laboratories employing a similar profiling procedure.

Acetoacetates↗
PubMed1989

Urinary excretion of 2,3-butanediol and acetoin by babies on a special care unit.

2,3-Butanediol was detected by capillary gas chromatography in 45 urine samples from 20 babies on a special care unit, 17 of whom were premature. The meso form of the diol predominated and in 21 samples was the only diastereoisomer present. Acetoin was found in 20 of the samples. It was never detected in the absence of 2,3-butanediol. 2,3-Butanediol was not detectable in more than trace amounts in urine from 66 other babies on the unit. The most likely origin of these compounds was from bacterial fermentation of pyruvate in the gut. Their presence may be explained by abnormal gut colonisation with acetoin-producing microorganisms, an abundant supply of nutrient lactose in the colon and increased intestinal permeability. It is further evidence of the magnitude of intestinal carbohydrate fermentation in preterm babies. 2,3-Butanediol could prove a useful biochemical marker for abnormal colonisation of neonates on special care units.

Acetoin↗
PubMed1989

1H NMR studies of urine from premature and sick babies.

High-frequency proton nuclear magnetic resonance (1H NMR) has been applied to a study of urine from premature and sick newborn babies with a variety of clinical disorders. These included severe birth asphyxia, necrotizing enterocolitis, ketosis, and drug treatment. Abnormal levels of metabolites such as lactate, ketone bodies, betaine, dicarboxylic acids, and 4-hydroxyphenolic acids were detected, as was the antibiotic metronidazole and one of its metabolites. The assignment of betaine was confirmed by two-dimensional 1H NMR studies of urine obtained from two adults with homocystinuria receiving treatment with oral betaine. High-resolution 1H NMR spectroscopy of urine is a potentially useful research technique for monitoring metabolism during early life.

Creatinine↗
PubMed1989

Maternal zinc and selenium status in pregnancies with a neural tube defect or elevated plasma alpha-fetoprotein.

Zinc and selenium status was assessed in 30 non-pregnant women, 69 women during normal pregnancy, six with a fetus with a neural tube defect (NTD) and 16 who had a raised plasma alpha-fetoprotein (AFP) but no detectable fetal abnormality. Plasma zinc and selenium concentrations were significantly reduced in the second trimester of normal pregnancy compared with non-pregnant levels. A significant decrease in concentrations of zinc in plasma and selenium in plasma and leucocytes was observed in women in the third trimester compared with women in the second trimester. Women with a fetal NTD and women with an unexplained elevation of plasma AFP had significantly lower leucocyte concentrations of zinc and of selenium. Mean values for plasma zinc, plasma and erythrocyte selenium, and for the activity of glutathione peroxidase in whole blood did not differ from those for normal pregnancy.

Erythrocytes↗
PubMed1989

Carbohydrate fermentation by gut microflora in preterm neonates.

To study organic acid excretion, urine was collected from 52 preterm infants at weekly intervals and analysed by capillary gas chromatography-mass spectrometry. Twelve of 22 babies born before 33 weeks' gestation excreted 2,3-butanediol, as did six born between 33 and 36 weeks. Six very immature babies also excreted acetoin, the metabolic precursor of the diol. Other products derived from carbohydrate included methylmalonic and ethylmalonic acids in one baby, and D-lactic acid in five. Acetoin has never been found in urine before, and the other four acids have been found only rarely. Excretion of these metabolites by preterm babies can be explained by increased intestinal permeability, unabsorbed lactose in the colon, and colonisation with certain opportunistic micro-organisms prevalent in neonatal units, including klebsiella, serratia, and enterobacter. The findings support evidence from breath hydrogen analysis that carbohydrate fermentation takes place in the gut of preterm infants.

Acetoin↗