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Biomedical subjects

M Platt

Publications and source records attributed to M Platt.

At least 19 recordsLinked to original sources
PubMed1994

The differential effects of body fat distribution on insulin and glucose metabolism during pregnancy.

OBJECTIVE: Our purpose was to investigate whether maternal obesity, or more specifically body fat distribution, is associated with alterations in carbohydrate metabolism during pregnancy. STUDY DESIGN: A longitudinal study of oral glucose tolerance tests, insulin, C peptide, and glucagon levels during each trimester and post partum was undertaken in nine lean and 14 obese women. Obese women were divided into lower body obese (n = 6, waist/hip ratio < 0.9) and upper body obese (n = 8, waist/hip ratio > or = 0.9). RESULTS: Fasting blood glucose levels declined with advancing gestation only in lean subjects. Upper body obese women demonstrated maximal glucose response and insulin area under the curve by the second trimester, whereas lean and lower body obese women did not until the third trimester. Insulin areas were significantly elevated in upper body obese compared with lower body obese women (second trimester, p < 0.01; third trimester, p < 0.03; post partum p < 0.05). In contrast, C peptide levels were similar in obese subgroups and were significantly elevated only when compared with those of lean women. C peptide/insulin molar ratios were lower in upper body obese women during the second trimester (4.3 +/- 0.8) and third trimester (4.2 +/- 0.7) compared with lean (6.5 +/- 1.3, 6.7 +/- 0.5) and lower body obese women (7.9 +/- 1.4, 6.5 +/- 1.4) (p < 0.01). A significant relationship between waist/hip ratio and glucose level (r = 0.70, p < 0.004) and insulin areas (r = 0.76, p < 0.001) was present in late pregnancy in obese subjects. CONCLUSIONS: Relative hyperinsulinemia and earlier maximal glucose response in upper body obese women suggests that body fat distribution may explain the metabolic heterogeneity present in obese women during pregnancy. Body fat topography may serve as a potential marker for the early development of carbohydrate intolerance during pregnancy.

Adipose Tissue↗
PubMed1994

Psychological profiles distinguishing litigating and nonlitigating pain patients: subtle, and not so subtle.

Chronic pain patients in the midst of litigation over settlement for their injuries were examined as a naturally occurring group where one might expect various distortions or differences in test findings on the Minnesota Multiphasic Personality Inventory-Revised (MMPI-2). Similar groups of 43 chronic pain patients in litigation and 45 not in litigation were examined on 10 key MMPI-2 variables selected a priori. Multivariate analysis of variance revealed a significant difference between groups (p = .036). Litigators were most distinct in endorsing more obvious and fewer subtle symptoms. A conversion profile was also more salient for litigators once the obvious versus subtle differences were taken into account. Implications for use of the MMPI-2 and for clinical work with litigious patients are examined.

Adolescent↗
PubMed1992

Pipecuronium versus high dose vecuronium. II. A comparison of speed of onset and cumulation during propofol anaesthesia.

The onset time and tendency to cumulation of pipecuronium and high-dose vecuronium were compared during nitrous oxide anaesthesia supplemented with a propofol infusion. Pipecuronium 0.06 mg.kg-1 had a similar duration of action to vecuronium 0.2 mg.kg-1 (49 vs 43). Patients who received vecuronium had a shorter onset time of neuromuscular blockade (p less than 0.01). Neither pipecuronium nor vecuronium showed marked cumulation.

Adult↗
PubMed1991

Effect of arterial carbon dioxide tension on the duration of action of atracurium.

The duration of action of atracurium was studied in two groups of patients. In group I (n = 15), patients' lungs were hyperventilated to a mean PaCO2 of 3.3 kPa and in group II (n = 15) lungs were ventilated to maintain a mean PaCO2 of 5.3 kPa. Anaesthesia was maintained using an infusion of propofol. The time taken to return to a T1 twitch height of 10% of control was measured following each incremental dose of atracurium 0.15 mg kg-1. It was found that the duration of action of atracurium was significantly (P less than 0.0005) shorter in the hypocapnic group.

Adolescent↗
PubMed1991

Effects of nitrous oxide on motor evoked potentials recorded from skeletal muscle in patients under total anesthesia with intravenously administered propofol.

The effect of nitrous oxide (N2O) on motor evoked potentials (MEPs) recorded from human subjects under total intravenous anesthesia with propofol (2,6-diisopropylphenol) was studied. MEPs were recorded from the 1st dorsal interosseous muscle of the foot in nine subjects; in two of these, simultaneous recordings were made from the 2nd dorsal interosseous muscle of the hand and from the deltoid muscle. Single transcranial electrical stimuli were used in recording the MEPs. The effects of N2O were studied at concentrations from 20 to 70%. Increasing concentrations of N2O caused a progressive increase in onset latency and a fall in the peak-to-peak amplitude of the MEPs recorded from the foot. Latency values showed a significant increase above the baseline at concentrations of N2O greater than 20% (P values, 0.05-0.005). The response amplitude showed a significant decrease from the baseline at concentrations of N2O greater than 50% (P values, 0.05-0.005). The 2nd dorsal interosseous muscle of the hand demonstrated a pattern of sensitivity to N2O similar to that of the 1st dorsal interosseous muscle of the foot. The onset latency and initial peak-to-peak amplitude of the deltoid muscle were insensitive to N2O at the concentrations used. We conclude that N2O can be used as an anesthetic adjunct without a significant deleterious effect on MEPs during intraoperative monitoring in patients under propofol anesthesia, providing concentrations are maintained below 50%.

Adult↗
PubMed1988

Histologic analysis of placental tissue in first trimester abortions.

The value of histologic evaluation in the analysis of material from first trimester abortions is not completely defined. We prospectively analyzed placenta and decidua from 75 first trimester, spontaneous abortions to ascertain if morphologic features were predictive of karyotype. The histologic features analyzed included hydropic villus change, villus fibrosis, villus scalloping with trophoblastic invaginations, atypical stromal cells, aggregates of lymphocytes in placenta or decidua, and acute inflammation of placenta or decidua. Normal karyotypes were observed in 44 cases and abnormal karyotypes were demonstrated in 31. The presence of villus scalloping with trophoblastic invagination was significantly associated with abnormal karyotypes, particularly triploidy, and the demonstration of acute inflammation was seen significantly more often in cases with normal karyotypes. We conclude that histology can provide only a suggestion as to the likelihood of an abnormal karyotype; the findings are not specific enough to obviate the need for karyotyping in the individual case.

Abortion, Spontaneous↗
PubMed1982

Effects of conventional and high frequency jet ventilation on lung parenchyma.

Despite the increasing acceptance of high frequency jet ventilation (HFJV), very little work has been done to determine if lung damage results from its use. We performed an experimental study to compare the effects of conventional ventilation with those of HFJV on the lung parenchyma of anesthetized dogs. Thirteen animals were studied for periods ranging from 2-24 h. Using a double-lumen Carlen's endotracheal tube, each animals's lungs were ventilated simultaneously but independently, one with conventional ventilation, the other with HFJV. No gross or microscopic evidence of atelectasis or barotrauma was noted in either group. Less hyperaeration was seen in the majority of jet ventilated lungs compared to the conventionally ventilated. In no case did the jet ventilated side show more damage than the control. We concluded that it is possible to use HFJV for 24 h without apparent parenchymal lung damage. Reduced hyperaeration is identified as a possible advantage of HFJV over conventional methods.

Animals↗
PubMed1981

Effects of verapamil on supraventricular tachycardia in patients with overt and concealed Wolff-Parkinson-White syndrome.

Verapamil (0.15 mg/kg) intravenously, was administered to 19 patients with recurrent supraventricular tachycardia (SVT) undergoing electrophysiological evaluation. Twelve patients had overt Wolff-Parkinson-White (WPW) syndrome and seven patients had concealed accessory pathways conducting in the retrograde direction only. Verapamil had a significant effect in delaying conduction and prolonging refractoriness in the atrioventricular (AV) node, but no significant actions on any of the other cardiac tissues that formed the tachycardia circuit in these patients. In particular, it had no significant effects on anterograde or retrograde bypass conduction or refractoriness. Sustained SVT was initiated in 15 patients, and was terminated within 60 to 105 seconds of a 30-second injection of verapamil in 13 patients. Cycle length alternation during SVT was seen in six patients prior to reversion, and spontaneous ventricular complexes (VPCs) were observed following verapamil administration in five patients. Two patients with apparently normal sinus node function showed prolongation of their sinus node recovery times immediately following reversion of SVT by verapamil. Echo zones were assessed before and after verapamil, and sustained or self-terminating SVT could still be induced after the drug in 13 of the 15 patients who had sustained SVT beforehand. It was concluded that intravenous verapamil was effective in terminating sustained SVT in the majority of patients with overt or concealed WPW and that, despite a potential for sinus node depression and the initiation of VPCs, it had no clinically significant side effects. The ability to reinitiate SVT following its administration suggests the need for immediate follow-up with maintenance drug therapy.

Adult↗
PubMed1979

Hemodynamic evaluation of the Carpentier-Edwards bioprosthesis in the aortic position.

The Carpentier-Edwards bioprosthesis is a glutaraldehyde-fixed porcine xenograft with a fully flexible thin-walled stent. Cardiac catheterization studies were performed in 17 patients to evaluate use of this valve in the aortic position. Hemodynamic studies established a mean peak gradient across the prosthesis of 19 mm Hg (range 5 to 65). The mean effective orifice area was calculated to be 1.6 cm2 (range 0.8 to 3.3). All patients demonstrated an improvement in functional class after operation. Mean left ventricular ejection fraction increased from 51 +/- 16 to 68 +/- 9 percent (P less than 0.004) in eight patients operated on for aortic stenosis, but was not significantly changed in patients operated on for aortic insufficiency. Hemodynamic comparison of the Carpentier-Edwards bioprosthesis with the standard Hancock xenograft showed similar effective orifice areas for the 23 and 25 mm diameter valves. In two patients studied the 21 mm Carpentier valve demonstrated a greater effective orifice area than that previously reported for the standard Hancock xenograft. The Carpentier-Edwards bioprosthesis affords both clinical and hemodynamic improvement when used in the aortic position and may allow improved effective orifice area when used in the smaller aortic root.

Adult↗
PubMed1979

Myocardial contractility in patients with ischemic heart disease during long-term administration of quinidine and procainamide. Direct measurement of segmental shortening with radiopaque epicardial markers.

The purpose of this investigation was to determine whether long-term oral administration of commonly prescribed doses of quinidine sulfate and procainamide hydrochloride to patients with ischemic heart disease affects myocardial contractility. Segmental contractility, assessed by the systolic shortening fraction, the relative change in interclip distance from diastole to systole, was measured by cineradiography of metal clips that had been sutured to the epicardium at the time of coronary artery bypass surgery. Global contractility was assessed by gated blood-pool scintigraphy. Systolic shortening fraction determinations and scintigraphy were obtained following five to seven days' administration of procainamide (500 mg every four hours), quinidine (200 mg every six hours), or neither drug in a random sequence. Serum drug levels (milligrams per liter) were 1.8 +/- 0.8 (mean +/- 1 SD) for quinidine and 3.7 +/- 1.1 for procainamide, when measured one hour before the next dose. During quinidine administration, mean segment shortening fraction decreased only slightly, but significantly (P less than 0.02), from 12.4 percent to 10.6 percent. The clinical importance of so small a change is questionable. During procainamide administration, there was a very small, insignificant (P greater than 0.9), decrease in segmental shortening. Global left ventricular function was not significantly changed by either drug. It appears that both drugs can be used over long periods in commonly prescribed doses in patients with ischemic heart disease without a major overall deleterious effect on cardiac performance.

Blood Pressure↗