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Biomedical subjects

R C Roy

Publications and source records attributed to R C Roy.

48 records · Page 3Linked to original sources
PubMed1986

Response of cerebral blood flow to changes in carbon dioxide tension during hypothermic cardiopulmonary bypass.

Changes in cerebral blood flow (CBF) in response to changes in PaCO2 were measured by intraaortic injection of 133Xe in 12 patients during hypothermic (23-30 degrees C) cardiopulmonary bypass. In each patient, CBF was determined at two randomly ordered levels of PaCO2 obtained by varying the rate of gas inflow into the pump oxygenator (Group I, n = 6) or by varying the percentage of CO2 added to the gas inflow (Group II, n = 6). Nasopharyngeal temperature, mean arterial pressure, pump-oxygenator flow, and hematocrit were maintained within a narrow range. In group I, a PaCO2 (uncorrected for body temperature) of 36 +/- 4 mmHg (mean +/- SD) was associated with a CBF of 13 +/- 5 ml X 100 g-1 X min-1, while a PaCO2 of 42 +/- 4 mmHg was associated with a CBF of 19 +/- 10 ml X 100 g-1 X min-1. In group II, a PaCO2 of 47 +/- 3 mmHg was associated with a CBF of 20 +/- 8 ml X 100 g-1 X min-1, and a PaCO2 of 53 +/- 3 mmHg was associated with a CBF of 26 +/- 9 ml X 100 g-1 X min-1. Within group I, the difference in CBF was significant (P less than 0.05); within group II, the difference in CBF was significant at the P less than 0.002 level. All CBF measurements were lower than those reported for normothermic, unanesthetized subjects of similar age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Hypertensive response to thiopental in man during cardiopulmonary bypass.

We report the effect of 250 mg of sodium thiopental on vascular tone at constant blood flow in 26 patients undergoing cardiopulmonary bypass while the ascending aorta was cross-clamped. Light anaesthesia was effected with fentanyl and enflurane, muscle relaxation with pancuronium. After a latent period of 10.5 +/- 0.7 s there was a hypertensive response of 9.8 +/- 0.5 s duration and of 21.4 +/- 1.7 mmHg (2.8 +/- 0.2 kPa) magnitude; this was followed by hypotension of 39.6 +/- 4.2 s duration and of 18.4 +/- 1.9 mmHg (2.4 +/- 0.3 kPa) magnitude. There was a statistically significant inverse correlation between the hypertension and body temperature (P = 0.005); the time to onset of hypertension correlated directly with pump volume (P = 0.001), weight of the patient (P = 0.03), and cross-clamp time before the drug was given (P = 0.002), and correlated inversely with the serum sodium concentration (P = 0.001). The duration of hypertension was inversely related to the plasma bicarbonate (P = 0.01) and body temperature (P = 0.04). The duration of hypotension was significantly longer in women (P = 0.0001) and was directly related to the duration of cross-clamping (P = 0.0007), to pH (P = 0.0016), and to PCO2 (P = 0.04). We speculate that thiopental induced the hypertensive response due to a potentiation of the vasoconstrictive (local) effect of norepinephrine, and induced the hypotensive response by a central nervous system effect. Thiopental had no apparent effect on venous tone.

Anesthesia, General↗
PubMed1985

Coronary revascularization in patients with bilateral internal carotid occlusions.

Coronary revascularization that is neurologically uneventful in patients with bilateral totally occluded internal carotid arteries has not been previously reported. We performed saphenous vein coronary artery bypass grafting on three such patients and observed them for 6 to 23 months. Preoperatively two of our patients had chronic stable symptoms of cerebrovascular insufficiency, and one had received cerebral revascularization via a superficial temporal-to-middle cerebral artery bypass. Controversy exists regarding proper cerebral protective maneuvers during coronary revascularization for patients with advanced cerebrovascular disease. Cerebral protection for our patients during cardiopulmonary bypass included hypothermia and high perfusion flows and pressures. Two patients also received prophylactic sodium thiopental. None of these three patients had a stroke perioperatively or during the follow-up period. We believe that these case histories strongly suggest that the functional state of the cerebral collateral circulation, as judged by preoperative neurological symptoms, predicts neurological outcome after coronary revascularization better than the specific occlusive anatomy of the extracranial carotid arteries.

Arterial Occlusive Diseases↗
PubMed1984

Effect of pethidine, fentanyl and morphine on post-operative shivering in man.

One hundred consecutive patients who shivered following general or regional anesthesia and a surgical procedure were randomly treated with 25 mg pethidine, 2.5 mg morphine, 25 micrograms fentanyl or sodium chloride 0.9%, given in equal intravenous volumes over a 15-min period. The effects were evaluated every 5 min after the first injection. There was a spontaneous, time-related disappearance of shivering in the sodium chloride-treated patients. In the pethidine-treated group, shivering disappeared more than twice as fast as in the control group. The difference was highly significant at 15 and 20 min (P less than 0.001) and was unrelated to weight, body temperature or duration of anesthesia. Women responded sooner than men, reaching significance at 10 min (P less than 0.05), while men did so only at 20 min. Morphine or fentanyl had no effect. Nausea and vomiting were minimal and of equal incidence in narcotic- and placebo-treated patients.

Adult↗
PubMed1982

Sagittal diameter of the cervical canal in normal Indian adults.

This paper is based on a radiographic study of 300 normal individuals from 18 to 34 years of age comprising 207 males and 93 females. A lateral radiograph of the cervical spine with a focal-film distance of 6 ft was obtained of each subject to measure the sagittal diameter of the cervical spinal canal. The mean sagittal diamter ranged from 21.43 mm at C1 to 16.42 mm at C7 in males and from 20.13 mm at C1 to 15.54 mm C7 in females. This diameter decreased from C1 down to C4 or C5 where there was a gradual but marginal increase to C6. This diameter was smallest at C7. In general the sagittal diameters In females were about 1 mm less than in males at all vertebral levels. The smallest sagittal diamter from C3 to C7 in both sexes was 13 mm. The largest sagittal diameter varied from 20.5 to 28 mm in males and 18.5 to 26 mm in females. The mean sagittal diameter showed some relationship to height in males. No significant difference was observed in relation to weight. The posterior component of the sagittal diameter was smaller in females than in males due to a difference in development of the laminae.

Adolescent↗
PubMed1981

Electroencephalographic evidence of arousal in dogs from halothane after doxapram, physostigmine, or naloxone.

The clinical impressions of enhanced arousal from halothane anesthesia and improvement of postanesthesia recovery scores after doxapram, physostigmine, or naloxone have not been verified in laboratory studies based on the effect of these drugs on MAC. With induction of anesthesia, a shift in the amplitude of the EEG from low to high occurs at anesthetic concentrations well below MAC and appears to coincide with the loss of consciousness. The authors examined the effect of arousal agents on the end-tidal halothane concentration required to produce this shifting EEG. In 24 unmedicated dogs, the end-tidal halothane concentration was elevated to 20 per cent above the shift point concentration (from 0.61 +/- 0.03 to 0.73 +/- 0.03 per cent) and maintained at this level for 30 min. Doxapram, 1 mg/kg, iv, and physostigmine, 0.03 mg/kg, iv, converted the EEG from a high amplitude to a low amplitude tracing in 22 +/- 3 s in eight of eight, and 225 +/- 37 s in seven of eight dogs, respectively. The end-tidal halothane concentration required to restore the shifting EEG was elevated above control for 50 +/- 7 min and 109 +/- 7 min, respectively. Naloxone, 0.06 mg/kg, iv, produced an awake EEG in two of eight dogs in 233 +/- 18 s which persisted for 22 +/- 4 min, and a transiently shifting EEG in three of eight dogs between 200 and 240 s. Naloxone 0.006, mg/kv, iv, produced an awake EEG in 80 +/- 8 s in four of four dogs who had previously received doxapram 3 h earlier. In this model doxapram and physostigmine paralleled the clinically observed onset and duration of arousal. The inconstant arousal from halothane anesthesia induced by naloxone was interpreted in terms of an opiate receptor independent action.

Anesthesia, Inhalation↗