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Biomedical subjects

S J Thomas

Publications and source records attributed to S J Thomas.

88 records · Page 5Linked to original sources
PubMed1983

A prospective study of complications of pulmonary artery catheterizations in 500 consecutive patients.

Five hundred twenty-eight pulmonary artery catheters were inserted in 500 patients at the New York University Medical Center between May and November, 1981. Complications occurred in 126 of 528 catheterizations. Serious complications occurred in only 23 of these 528 catheterizations (4.4 percent). These complications, while serious, did not contribute directly to any of 31 deaths seen in these patients. Pulmonary artery catheters were reported by clinicians to have been of benefit in the management of 80 percent of these patients. We conclude, in view of this experience, that the wide use of these catheters is justified, but only if there is a probability that the catheters will significantly contribute to the management of the individual patient.

Adult↗
PubMed1983

The role of the activated clotting time in heparin administration and neutralization for cardiopulmonary bypass.

Precise guidelines for heparin administration and neutralization during cardiopulmonary bypass (CPB) are not established. To a large extent, the uncertainty originates from a disparity between the heparin dosage, the plasma heparin concentration, and the clinical heparin effect. We investigated these relationships in 44 consecutive patients at New York University Medical Center. Following serial loading doses of heparin (2 and 4 mg/kg) there was a wide variation in both the measured clinical heparin effect (activated clotting time--ACT) and the plasma heparin concentration. When the Act was compared to the heparin concentration, there was no linear relationship noted after heparin does commonly employed for CPB. The calculated heparin sensitivity varied over a fourfold range and was not related to the baseline antithrombin III activity. At the completion of CPB, heparin was neutralized with a 2 mg/kg protamine dose regardless of the total heparin dose. Heparin levels fell from 4.17 +/- 1.29 to 0.19 +/- 0.20 units/ml. Additional protamine was given to 49% of the patients as the ACT had not returned to pre-heparin levels. The total protamine dose rarely exceeded 3 mg/kg. This technique resulted in the administration of 30% to 50% less protamine than predicted by other commonly used protocols. In the subsequent 4 hours after protamine administration, heparin levels remained insignificant. Mild heparin rebound was found in two patients (4.5%) but was not associated with excessive bleeding. Following bypass a comparison of heparin levels and ACTs demonstrated the ACT to be a poor indicator of residual circulating heparin. These data show: (1) that neither the heparin dosage nor the plasma heparin concentration can accurately predict the magnitude of the clinical heparin effect in patients undergoing CPB and emphasize the importance of the ACT as the best available measurement of safe anticoagulation, (2) heparin "rebound" was not clinically significant, and (3) heparin was neutralized with 2 to 3 mg/kg protamine in virtually all patients, regardless of the total heparin dose.

Adult↗
PubMed1976

Measurement of cortisol, cortisone, 11-deoxycortisol and corticosterone in foetal sheep plasma during the perinatal period.

A method is described for the resolution and individual quantitation of cortisol, cortisone, 11-deoxycortisol and corticosterone in foetal sheep plasma. The steroids were extracted by solvent partition and separated by LH-20 Sephadex column chromatography. Radioimmunoassay was used for the measurement of 11-deoxycortisol and cortisone and competitive protein-binding for corticosterone and cortisol. The relative levels of these steroids in the plasma of chronically catheterized sheep foetuses from 12 days before birth to term and then in the newborn lamb until 2 days of age are recorded. Cortisol gradually increased from a basal concentration of between 0 - 5 and 3 - 0 mug/100 ml plasma between days 12 and 5 pre partum, and then rose rapidly to 10 mug/100 ml plasma during the last 5 days of pregnancy to reach a maximum during or just after birth. Two days post partum the levels had fallen to approximately 3 mug/100 ml plasma. The mean value for 11-deoxycortisol between days 8 and 3 pre partum was 0 - 4 mug/100 ml plasma and increased in the final days before delivery to 1 - 0 mug/100 ml. Corticosterone initially showed slightly higher levels (approximately 1 - 5 mug/100 ml) in the earlier period of investigation but then fell during the immediate pre-partum period to 0 - 8 mug/100 ml. Cortisone was not detected at any stage of the investigations. The relationship between levels of cortisol and 11-deoxycortisol in foetal plasma and myometrial contractility is shown. An increase in uterine activity was seen to occur at the time that cortisol levels were at their maximum. The 11-deoxycortisol values throughout this particular study remained low. The results are discussed in relation to recorded levels in the adult and to previous studies in vitro with regard to changing steroid biosynthetic enzyme activity.

Animals↗
PubMedDate not supplied

The use of carbon-loaded thermoluminescent dosimeters for the measurement of surface doses in megavoltage x-ray beams.

To determine the absorbed dose to the skin of patients undergoing radiotherapy with megavoltage radiations, it is necessary for the dose to be measured at shallow depths. This report assesses the suitability of carbon-loaded thermoluminescent dosimeters (manufactured by Vinten Instruments Limited) for this purpose. Measurements have been made of the effective measurement depth of the dosimeters, the linearity with dose, and the variation of sensitivity within a batch. The variation of surface dose with incident angle of radiation for 5-MV x rays has been measured using these disks; the results are compared with results obtained using a thin-windowed ionization chamber.

Humans↗
PubMedDate not supplied

A modified power-law formula for inhomogeneity corrections in beams of high-energy x rays.

The Batho power-law formula is in common use in many treatment planning systems to correct for the presence of lungs and other inhomogeneities. While giving excellent agreement with measurement for Cobalt-60 radiation, it tends to underestimate the lung correction required for higher energy x rays and is undefined for distances beyond an interface less than the buildup distance. This paper suggests a simple modification that greatly improves the agreement with measured data and gives a continuously defined function at all depths. Measurements have been made in a polystyrene and cork phantom to simulate the effects of lung; data are presented for beams of 8-MV x rays, 16-MV x rays, and Cobalt-60 gamma rays.

Cobalt Radioisotopes↗
PubMedDate not supplied

Chiropractic adjustment in the management of visceral conditions: a critical appraisal.

OBJECTIVE: To establish whether Australian chiropractors regard spinal adjustment as an intervention option for patients presenting with visceral conditions and to ascertain the preferred level of adjustment for patients presenting with migraine, asthma, hypertension or dysmenorrhea. DESIGN AND SETTING: A survey of all chiropractors registered in Australia. OUTCOME MEASURE: Practitioners' opinions regarding the usefulness of spinal adjustment in the management of patients with visceral conditions were canvassed. Based upon their personal clinical experience, practitioners were requested to comment on the appropriate level of adjustment in the management of various visceral conditions. MAIN RESULTS: Twenty-two percent of the 1311 chiropractors registered in Australia responded to the survey. More than half of the respondents favored a role for spinal adjustment in the management of patients with visceral conditions. The perceived usefulness of spinal adjustment varied according to the condition being managed, as did the preferred level of adjustment. CONCLUSIONS: Chiropractors continue to use spinal adjustment in the management of visceral conditions despite this intervention being regarded as an obstacle to the recommendation of public finding for chiropractic services in Australia. Further investigation into the validity of the chiropractic management of visceral conditions is recommended.

Asthma↗
PubMedDate not supplied

The risk of periventricular-intraventricular hemorrhage with vacuum extraction of neonates weighing 2000 grams or less.

OBJECTIVE: The objective of this retrospective study was to test the hypothesis that vacuum extraction of neonates with a birth weight < or = 2000 gm is associated with an increased risk of periventricular-intraventricular hemorrhage (PV-IVH). STUDY DESIGN: One hundred sixty-eight neonates weighing < or = 2000 gm were entered into this case control study. Fifty-six neonates delivered by silicone-rubber vacuum comprised the study group. For every infant born by vacuum-assisted delivery, two spontaneously delivered neonates served as controls (n = 112) and were matched for best obstetric gestational age (within 1 week), delivery date within 1 year, and birth weight < or = 2000 gm. Maternal and neonatal medical records were reviewed for demographic variables, antenatal complications, indication for vacuum-assisted delivery, neonatal birth weight, Apgar scores, umbilical cord blood gas values, and neonatal morbidity including the incidence of PV-IVH. All perinatal outcome variables were compared between the vacuum-assisted and spontaneously delivered groups. RESULTS: Both groups were similar with regard to maternal age, parity, antepartum complications, gestational age at delivery, neonatal birth weight, and gender. Both groups were also similar with regard to the incidence of 1-minute Apgar score < 5, small for gestational age, cephalhematoma, birth trauma, respiratory distress syndrome, hyperbilirubinemia, and sepsis. There was a significant increased incidence of 5-minute Apgar scores < 7 in the vacuum-assisted group (p = 0.04). No significant difference was observed in the incidence of PV-IVH grades 1 through 4 (21.4% vacuum group vs 16.1% control group, odds ratio 1.42, 0.58 to 3.45). CONCLUSION: Indicated use of the silicone-rubber vacuum to assist vaginal delivery of neonates weighing < or = 2000 gm does not appear to be associated with an increased risk of PV-IVH or other neonatal complications.

Case-Control Studies↗
PubMedDate not supplied

Laparoscopic appendectomy and cholecystectomy during pregnancy: six case reports.

BACKGROUND: Pregnancy was once considered a contraindication to laparoscopic cholecystectomy and appendectomy. The progression of laparoscopic techniques has resulted in a continued reassessment of laparoscopic procedures during pregnancy. There still exists some controversy as to the safety of laparoscopic procedures during pregnancy. This paper reviews our series of six pregnant patients treated laparoscopically for appendicitis and cholecystitis. METHODS: Charts were reviewed of all pregnant patients who underwent laparoscopic cholecystectomy or appendectomy at St Clare's Hospital Schenectady, New York between 1992 and 1996. Six patients were identified. Patients and obstetricians were contacted to investigate the results of the pregnancy. RESULTS: All patients and fetuses survived the procedure. Two patients delivered prematurely but remote from the operative procedure. All infants were healthy postpartum. One patient underwent an elective abortion as she had planned. The abortion was remote from the surgical procedure. CONCLUSION: Our series adds to the growing evidence that laparoscopic cholecystectomy and laparoscopic appendectomy can be performed safely during pregnancy.

Adult↗