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Biomedical subjects

C Prys-Roberts

Publications and source records attributed to C Prys-Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1984

Plasma serotonin concentrations during and after cardiac surgery.

Plasma serotonin concentrations, assayed as plasma 5-hydroxyindoles (5-HI) and platelet 5-hydroxytryptamine (5-HT), were measured in 12 patients undergoing coronary artery graft surgery (group 1) and five patients undergoing valve replacement (group 2). Mean values of plasma 5-HI before cardiopulmonary bypass (CPB) were 29.8 +/- 2.0 ng ml-1 in group 1 and 30.6 +/- 2.8 ng ml-1 in group 2. No significant changes of plasma 5-HI occurred during or after CPB in either group. Although postoperative hypertension occurred in 75% of group 1 patients, no significant correlation was found between plasma 5-HI concentration and systolic blood pressure. A significant increase of platelet 5-HT occurred during bypass (327 ng/2 X 10(8) platelets increasing to 488 ng/2 X 10(8) platelets, p less than 0.01) but returned to baseline values postoperatively. We conclude that plasma 5-HI concentrations are not involved in the pathophysiology of postoperative hypertension following myocardial revascularization.

Adult↗
PubMed1984

Age influences the minimum infusion rate (ED50) for continuous infusions of Althesin and methohexitone.

The influence of age has been studied on equipotent rates of continuous infusions of two intravenous hypnotic agents. Two end points have been defined; ED50: the rate needed to suppress the initial response to the surgical incision in 50% of patients, and ED95: the corresponding rate in 95% of patients receiving continuous infusion anaesthesia to supplement 67% nitrous oxide in oxygen. All 210 patients included in the study were premedicated with morphine 0.15 mg kg-1. For patients aged 20-40 years (young group), the ED50 values for Althesin (as alphaxalone) and methohexitone were 14.6 micrograms kg-1 min-1 and 59.9 micrograms kg-1 min-1. The ED95 values were 21.0 micrograms kg-1 min-1 and 92.1 micrograms kg-1 min-1. For patients aged 55-80 years (old group), the ED50 values for Althesin and methohexitone were 11.0 micrograms kg-1 min-1 and 44.2 micrograms kg-1 m in-1, while the corresponding ED95 values were 16.4 micrograms kg-1 min-1 and 76.2 micrograms kg-1 min-1.

Adult↗
PubMed1983

Haemodynamic effects of infusions of diisopropyl phenol (ICI 35 868) during nitrous oxide anaesthesia in man.

The haemodynamic effects of diisopropyl phenol in cremophor EL at infusion rates of 50-55 and 100 micrograms kg-1 min-1 in combination with inhalation of 67% nitrous oxide have been studied during spontaneous and controlled ventilation in patients premedicated with morphine and atropine. Under all the conditions studied diisopropyl phenol supplementation of nitrous oxide anaesthesia was associated with a decreased arterial pressure (-20% to -31%) compared with the awake patient, related to a decrease in cardiac output (-27% to 29%) and an increase in systemic vascular resistance (+8% to +30%) during surgery, but to a decrease in cardiac output (-19%) and a decrease in systemic vascular resistance (-17%) during anaesthesia without surgery. Doubling the infusion rate of diisopropyl phenol caused no significant haemodynamic changes during either spontaneous or controlled ventilation. The haemodynamic manifestations of sympathetic nerve activity in response to laryngoscopy and intubation were poorly suppressed by diisopropyl phenol.

Aged↗
PubMed1983

Hepatic function after anaesthesia for major vascular reconstructive surgery.

Three groups of patients received Althesin, minaxolone or di-isopropyl phenol to supplement 67% nitrous oxide in oxygen. A fourth group receiving halothane to supplement nitrous oxide in oxygen acted as a control. Hepatic function tests were measured before operation and on days 1, 3, 5 and 7 after major vascular reconstructive surgery. There were significant increases to a mean value above the upper limit of normal in aspartate amino-transferase activity by day 3 in all groups. Total lactic dehydrogenase activity increased in the patients receiving Althesin, minaxolone and halothane. No change was seen in the alkaline phosphatase in any of the study groups. Gamma glutamyl transpeptidase increased in all groups, but the mean value at day 7 was not greater than the upper limit of normal. The mean activity of ornithine carbamoyl transpeptidase showed no change in any group throughout the study period. Two of the patients receiving minaxolone suffered cholestatic jaundice during the first month. These results suggest that anaesthesia with Althesin or di-isopropyl phenol results in enzyme changes similar to those seen in a comparable group of patients receiving halothane to supplement nitrous oxide in oxygen anaesthesia.

Aged↗
PubMed1983

Baroreflex effects of althesin infusions to supplement nitrous oxide anaesthesia in man.

The effects on baroreflex control of heart rate, of two infusion rates of Althesin (18 and 36 micrograms kg-1 min-1 as total steroid) to supplement 66% nitrous oxide in oxygen anaesthesia, have been studied in six younger (mean age 35.5 yr) and six older (mean age 61.0 yr) patients. Steady-state anaesthesia at both infusion rates was associated with diminished baroreflex sensitivity and resetting of the reflex to allow lower arterial pressures to be maintained without tachycardia.

Adult↗
PubMed1983

Dose-response relationships for infusions of Althesin or methohexitone.

A technique is described for the determination of equipotent rates of infusion of intravenous hypnotic agents. Two end points have been defined; the rates needed to suppress the initial response to the surgical incision in 50% (ED50) and 95% (ED95) of patients receiving continuous infusion anaesthesia to supplement 67% nitrous oxide in oxygen. For patients aged 20-60 years, and premedicated with morphine 0.15 mg/kg intramuscularly, the ED50 values for Althesin (as alphaxalone) and methohexitone by infusion were 13.7 and 48.8 micrograms/kg/minute respectively. The ED95 values were 18.1 and 75.9 micrograms/kg/minute. For patients of a similar age premedicated with diazepam 10 mg orally, the ED50 values for Althesin and methohexitone were 18.5 and 66.0 micrograms/kg/minute respectively; while the ED95 values were 24.2 and 80.8 micrograms/kg/minute.

Adult↗
PubMed1983

Hemodynamic and hepatic effects of methohexital infusion during nitrous oxide anesthesia in humans.

The hemodynamic effects of methohexital, at infusion rates of 60-65 and 120 micrograms/kg/min with concomitant inhalation of 67% nitrous oxide in oxygen, have been studied during spontaneous and controlled ventilation in 8 patients. Under most of the conditions studied methohexital infusion anesthesia was associated with lower arterial pressure (-13% to -33%) than in the awake state, decreased cardiac output (-26% to -38%), and increased systemic vascular resistance (+5% to +37%) during surgery, but also with decreased cardiac output (-25%) and decreased systemic vascular resistance (-13%) during anesthesia without surgery. The higher infusion rate was not associated with decreases in arterial pressure or cardiac output during either spontaneous or controlled ventilation. The hemodynamic response to laryngoscopy and intubation was poorly suppressed by methohexital in that peak arterial pressures exceeded the preanesthetic values by 33%. No evidence of impaired hepatocellular function was found after infusions of methohexital lasting up to 4 h.

Aged↗
PubMed1983

Ventilatory depression related to plasma fentanyl concentrations during and after anesthesia in humans.

Twenty-four patients were allocated randomly into four groups for the study of the pharmacokinetics of, and effects on postoperative ventilation of, two doses of fentanyl (10 micrograms/kg or 25 micrograms/kg) administered at the start of general anesthesia in which ventilation was controlled at a fixed volume, but arterial PCO2 was adjusted to a range of either 38-42 torr, or 20-25 torr. During the first 2 hr after anesthesia, ventilatory depression (CO2 responsiveness decreased to less than 50% of awake values, PaCO2 greater than 48 torr) occurred only in patients who had received 25 micrograms/kg fentanyl, and was more marked in patients who were hyperventilated to a low PaCO2 during anesthesia. Plasma fentanyl concentrations associated with 50% depression of CO2 responsiveness were in the range 1.5-3.0 ng/ml, the lower values found in patients hyperventilated to a low PaCO2. Whole-body clearance of fentanyl was significantly decreased by hypocapnic hyperventilation.

Adult↗
PubMed1983

Ventilatory effects during and after continuous infusion of fentanyl or alfentanil.

The opioid drugs fentanyl and alfentanil were infused at a constant rate as supplements to nitrous oxide in oxygen anaesthesia throughout the period of surgery. These infusions were continued into the period after operation for 1 h after the discontinuation of anaesthesia. Continuous infusion of alfentanil 20 micrograms kg-1 h-1 and fentanyl 3 micrograms kg-1 h-1 resulted in depression of the carbon dioxide response curve with a lesser effect on frequency and minute ventilation. One hour after discontinuing the infusions the degree of ventilatory depression was only marginally less with fentanyl, but considerably less with alfentanil, reflecting the shorter terminal half-life of that drug.

Adult↗
PubMed1983

Ventilatory depression during and after infusion of alfentanil in man.

Sixteen fit young patients undergoing body surface surgery received an infusion of alfentanil 50 or 100 micrograms kg-1 h-1 to supplement nitrous oxide anaesthesia. The alfentanil infusion was continued for 2 h after operation at the slower rate of 20 micrograms kg-1 h-1. The intraoperative infusions provided satisfactory conditions for anaesthesia. The infusion after operation provided adequate analgesia at a cost of depression of carbon dioxide responsiveness to 50% of its value before operation, but only moderate effects on minute volume and PaCO2. Plasma alfentanil concentration during the postoperative infusion was 108 +/- 37 ng ml-1 (mean +/- SD).

Adult↗
PubMed1982

The oscillotonometer in theory and practice.

The accuracy of the Scala Alternans Altera oscillotonometer was investigated by comparison with direct intra-arterial pressures. It was found that the traditional criteria for detecting systolic and diastolic pressures were in error. A slow deflation rate was essential for the accurate measurement of systolic pressure, the maximum amplitude of needle oscillation correlated closely with mean pressure, and the determination of diastolic pressure was so inaccurate as to be clinically useless. The response of the oscillotonometer was also found to be dependent upon the individual combination of oscillotonometer and patient.

Blood Pressure Determination↗
PubMed1982

Interactions of anaesthesia and high pre-operative doses of beta-receptor antagonists.

Haemodynamic responses to anaesthesia and surgery were observed in 13 patients with severe renovascular hypertension treated with high doses of beta-receptor antagonists (equivalent to 10-37 mg/kg/day of propranolol) and 24 patients receiving moderate doses of beta-receptor antagonists (equivalent to 120-480 mg propranolol per day). Chronotropic and inotropic responses to the noxious stimuli of laryngoscopy or surgical stimulation were effectively suppressed by beta-receptor blockade thus increasing arterial pressure due to these stimuli or aortic cross-clamping which indicated a purely resistive load for the left ventricle. In no patient was evidence found that myocardial performance, and its effect on left ventricular ejection, was seriously compromised.

Adrenergic beta-Antagonists↗
PubMed1981

Minaxolone.

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Alfaxalone Alfadolone Mixture↗