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Biomedical subjects

C Prys-Roberts

Publications and source records attributed to C Prys-Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1987

Alfentanil infusions: relationship between pharmacokinetics and pharmacodynamics in man.

Fourteen fit young patients undergoing body surface surgery received an infusion of alfentanil at either 50 or 100 micrograms kg-1 hr-1 to supplement nitrous oxide anaesthesia. The alfentanil infusion was continued for two hours post-operatively at the lower rate of 20 micrograms kg-1 hr-1. Resting ventilation, carbon dioxide responsiveness and pain scores were measured post-operatively. Values for clearance and elimination half life were similar to data following single doses of alfentanil but showed considerable interindividual variation. However, there was a greater systemic clearance (P = 0.02) when determined using the post-infusion decay data compared with that calculated during anaesthesia (527 ml min-1 compared with 434 ml min-1). This is in accord with observations for other intravenous drugs.

Adult↗
PubMed1987

Hemodynamic effects of infusions of the emulsion formulation of propofol during nitrous oxide anesthesia in humans.

The hemodynamic response to anesthesia with the aqueous emulsion formulation of propofol was studied in healthy patients (ASA I or II), aged 39-57 yr, premedicated with morphine, 0.15 mg/kg. Anesthesia was induced in all patients with propofol, 2 mg/kg. Subsequently, patients were randomly assigned to two groups and maintained by a continuous intravenous infusion (group 1 received 54 micrograms X kg-1 X min-1, group 2 received 108 micrograms X kg-1 X min-1) to supplement 67% nitrous oxide. Three minutes after induction, systolic arterial pressure (SAP) decreased 28% (P less than 0.01) and was associated with decreased (-12%) cardiac output (Q70) and decreased (-15%) systemic vascular resistance (SVR). The hemodynamic response to tracheal intubation was not obtunded, but peak values of arterial pressures and heart rate did not exceed those recorded awake. Thirty minutes elapsed before repeating measurements prior to the first surgical incision. In group 1, SAP and Q70 decreased to 65% and 68% of awake values and in group 2 to 55% and 74% (P less than 0.05). Mild ventilatory depression persisted for the duration of spontaneous ventilation and was not reduced by the stimulus of surgery, which caused no significant hemodynamic responses in either group. Decreasing arterial PCO2 to the awake value by controlled ventilation increased SVR (P less than 0.05), but the associated increased SAP and decreased Q70 did not reach statistical significance. No patient reported awareness. The infusion of the emulsion formulation of propofol was associated with satisfactory anesthesia and recovery and with hemodynamic effects similar to those recorded with other intravenous anesthetics.

Adult↗
PubMed1987

Effect of propofol anesthesia on baroreflex activity in humans.

Previous studies have shown that infusions of propofol, a new intravenous anesthetic, were associated with decreased arterial pressure and slow heart rates. To evaluate the role of baroreflex mechanisms in sustaining these conditions, the effects of two infusion rates of propofol (54 and 108 micrograms.kg-1.min-1) to supplement 66% nitrous oxide in oxygen anesthesia were studied in twelve ASA class I patients having a mean age of 34 years. Baroreflex control of heart rate was studied by perturbing the patients' arterial pressure with phenylephrine or sodium nitroprusside. Valsalva maneuvers were used to assess the response of the systemic arterial system. Steady state anesthesia at both infusion rates was not associated with decreased sensitivity of the baroreflex control of heart rate, but resetting of the reflex occurred to allow lower arterial pressures for a given heart rate than in the awake state. During propofol infusions at either rate, the diastolic pressure overshoot normally associated with the relief of raised airway pressure in the Valsalva maneuver was significantly reduced. It is concluded that propofol/nitrous oxide anesthesia is not associated with impairment of baroreflex sensitivity, but that central sympatholytic and/or vagotonic mechanisms enable low heart rates to be sustained despite decreased arterial pressures.

Adult↗
PubMed1986

Dose requirements of propofol by infusion during nitrous oxide anaesthesia in man. I: Patients premedicated with morphine sulphate.

The study was performed to determine the ED50 and ED95 of a continuous infusion of the emulsion formulation of propofol during 67% nitrous oxide anaesthesia in 57 patients premedicated with morphine sulphate 0.15 mg kg-1. Anaesthesia was induced with propofol 2 mg kg-1, and maintained before incision with a fixed-rate infusion of propofol to supplement nitrous oxide. The response to the first surgical incision, made at least 30 min after induction of anaesthesia, was observed. The ED50 was 53.5 micrograms kg-1 min-1 and the ED95 was 112.2 micrograms kg-1 min-1. At the time of the first surgical incision, the venous whole blood concentrations of propofol at the ED50 and ED95 infusion rates (EC50 and EC95) were 1.66 micrograms ml-1 and 3.39 micrograms ml-1, respectively. The satisfactory maintenance of anaesthesia provided by nitrous oxide supplemented with propofol was associated with haemodynamic stability and rapid, uncomplicated recovery.

Adult↗
PubMed1986

Haemodynamic disturbances during anaesthesia in a patient receiving calcium channel blockers.

Haemodynamic changes (supraventricular tachycardia, decreases in arterial pressure) were observed during laryngoscopy and intubation of the trachea in a patient receiving nifedipine and verapamil. Before the induced stresses of laryngoscopy and tracheal intubation, these drugs had controlled the patient's arterial pressure and heart rate satisfactorily, and possible reasons why this was not so at the commencement of anaesthesia are discussed.

Anesthesia, General↗
PubMed1986

Comparison of isoflurane and halothane in outpatient paediatric dental anaesthesia.

Isoflurane was compared with halothane as the sole supplement to anaesthesia with nitrous oxide and oxygen for outpatient dental extractions in 80 children. Induction and maintenance of anaesthesia were satisfactory with both agents, although there was a higher incidence of coughing, salivation and laryngospasm in the group receiving isoflurane. However, in contrast to predictions from the physical properties of isoflurane and halothane, immediate recovery was significantly slower in patients who had received isoflurane. Recovery was complicated by coughing in a significant number of patients in the isoflurane group. The incidence of reported complications during later recovery was similar with both agents, apart from the complaint of non-specific postoperative aches in a significant number of patients to whom isoflurane was administered.

Anesthesia Recovery Period↗
PubMed1986

Restoration of baroreflex control of heart rate during recovery from anaesthesia.

The effects on baroreflex control of heart rate of halothane or methohexitone used to supplement 67% nitrous oxide in oxygen have been studied in 21 patients. Stable anaesthesia with either agent caused depression of baroreflex sensitivity by more than 50%. The set point of the reflex was also changed by both agents, but in opposite directions. Halothane administration resulted in slower heart rates at lower arterial pressures, whereas the infusion of methohexitone caused faster heart rates at lower arterial pressure. During recovery from anaesthesia, there was a rapid return of baroreflex sensitivity to normal and this was achieved before the patients regained consciousness, with no difference between the two groups. The reflex was reset rapidly and repeatedly during the recovery phase.

Adult↗
PubMed1986

Studies of anaesthesia in relation to hypertension. VII: Adrenergic responses to laryngoscopy.

Arterial pressure and plasma catecholamine concentrations were measured in 16 normotensive and 10 hypertensive patients undergoing elective vascular surgery. Following induction of anaesthesia, both arterial pressure and plasma noradrenaline concentrations decreased in both groups. Following laryngoscopy, there was a moderate increase in arterial pressure in both normotensive and hypertensive patients. In normotensive patients, laryngoscopy was associated with a moderate increase in plasma noradrenaline concentration. There was no change in adrenaline concentration. By contrast, there was a marked increase in noradrenaline concentration, a moderate increase in adrenaline concentration and an arterial pressure response in the group of hypertensive patients. These data are consistent with transient sympathetic overactivity in hypertensive patients following noxious stimuli such as laryngoscopy.

Adrenergic beta-Antagonists↗
PubMed1986

Anaesthesia and severe pulmonary disease.

The key to the management of anaesthesia in patients with severe pulmonary disease lies in predicting the requirement for support of ventilation and/or oxygenation in the postoperative period, and the provision of effective pain relief in such a way as to allow the patient to maintain adequate spontaneous ventilation. This in turn depends on understanding the influence of the relevant surgical intervention on the patient's ability to sustain his normal breathing requirements, to breathe deeply, and to cough.

Anesthesia, General↗
PubMed1985

Assessment of beta-adrenoceptor blockade during anesthesia in humans: use of isoproterenol dose-response curves.

Patients with hypertension or ischemic heart disease are often treated with beta-adrenoceptor antagonists, yet the degree of beta-adrenoceptor blockade has rarely been studied in relation to anesthesia. We have constructed isoproterenol dose-response curves in four groups of patients under general anesthesia: group I, 27 elderly normotensive patients not receiving drugs; group II, 14 hypertensive patients treated with cardioselective beta-adrenoceptor antagonists; group III, 15 hypertensive patients receiving nonselective beta-adrenoceptor antagonists; group IV, 13 patients receiving an infusion of labetalol at 0.15 mg X kg-1 X hr-1. Geometric mean CD25, the dose of isoproterenol required to increase the heart rate by 25 beats/min was 4.4 micrograms (3.5-5.6, 95% confidence interval (CI) of the mean) in group I, and 27 micrograms (19-38, 95% CI), 39 micrograms (29-52, 95% CI), and 95 micrograms (62-147, 95% CI) in groups II, III, and IV, respectively. All differences were significant (P less than 0.01), except those between groups II and III (P less than 0.1). No signs of myocardial ischemia and only a few transient arrhythmias were observed. Isoproterenol dose-response curves are a safe means to assess the degree of beta-adrenoceptor blockade during anesthesia and the postoperative period.

Adrenergic beta-Antagonists↗
PubMed1985

Propofol ('Diprivan') by intravenous infusion with nitrous oxide: dose requirements and haemodynamic effects.

The new formulation of propofol appears to be approximately equipotent to the previous formulation when used as an infusion to supplement nitrous oxide anaesthesia in patients premedicated with morphine. Preliminary haemodynamic studies indicate that the emulsion formulation causes more arterial hypotension than the original Cremophor formulation, though larger numbers are required to confirm this finding.

Adjuvants, Anesthesia↗
PubMed1985

Auscultatory measurement of arterial pressure during anaesthesia: a reassessment of Korotkoff sounds.

The accuracy of the indirect auscultatory method, using Korotkoff sounds for determination of arterial pressures, was investigated by comparison with direct intra-arterial measurements. Eight hundred and sixty-three comparisons were made in 25 patients aged between 27 and 75 years over blood pressures ranging from 59 to 235 mmHg for systolic and 28 to 145 mmHg for diastolic. The regression equation for all systolic pressure measurements was y = 13.9 + 0.81x, and for all diastolic pressure measurements was y = 21.4 + 0.71x. Although there was a significant (P less than 0.001) correlation coefficient between direct and indirect measurements for both systolic (r = 0.93) and diastolic pressures (r = 0.79), the 95% confidence limits (+/- 22 mmHg for systolic and +/- 19 mmHg for diastolic) were very wide, reflecting the influences of observer variation and other sources of error.

Adult↗
PubMed1984

Studies of anaesthesia in relation to hypertension. VI: Cardiovascular responses to extradural blockade of treated and untreated hypertensive patients.

The haemodynamic effects of extradural blockade were investigated in 25 hypertensive patients divided into three groups: 11 treated patients receiving lumbar extradural blockade (LT), nine treated hypertensive patients receiving thoracic extradural blockade (TT), and five untreated patients receiving lumbar extradural blockade (LU). Haemodynamic measurements were performed before and after the establishment of the extradural blockade, and repeated with the patients under light general anaesthesia. Mean upper level (T7) and range (T4-S1) of sensory blockade were similar in the two lumbar extradural groups, and mean segmental spread in the TT group was T4-L1. Changes from baseline to lowest arterial pressure showed a 22% (P less than 0.01) decrease in MAP in the LT group, 18% (P less than 0.05) in the TT group, and 42% (P less than 0.05) in the LU group. The decrease in arterial pressure was associated with a decrease in SVR in the LT group, and also with a decrease in cardiac output in the LU group. Three of the five untreated hypertensive patients demonstrated unacceptable decreases of arterial pressure, associated with abrupt and severe bradycardia, and required immediate treatment (head-down tilt, atropine and methoxamine). These complications were not observed in any of the treated hypertensive patients (P = 0.018).

Adrenergic beta-Antagonists↗
PubMed1984

The validity of informed consent in a clinical study.

Patients, aged 36 to 78 years, who had participated in two studies that included the ventilatory effects of postoperative analgesia, returned a questionnaire canvassing their views of the procedure for obtaining consent and the conduct of the study. Fourteen of 18 patients from one study, and all 18 from the second, returned their questionnaires. Thirty of the 32 patients were satisfied with the pre-operative explanation. Eleven patients felt obliged to take part, not because of coercion, but from a sense of duty to others. The breathing tests caused discomfort to eight patients but only one of them found this more than expected from the pre-operative explanation. Only two patients, both in the second study, said that they would not volunteer again for a similar study. There was no suggestion that the age of the patient or the fact that they were undergoing major surgery had any influence on their attitudes or comprehension. It may be prudent to use this type of questionnaire to evaluate the response of patients to some research projects.

Aged↗
PubMed1984

An assessment of the Dinamap 845.

The accuracy of the Dinamap 845 automatic blood pressure recorder was assessed by comparing its own indirect determinations of blood pressure with direct intra-arterial recordings. It was found that in the majority of cases it was capable of producing reliable trend information during anaesthesia. The instrument may not be able to interpret pressure signals from a patient with a severe dysrhythmia. It is probably an unsuitable monitor for use with very rapidly acting drugs such as sodium nitroprusside.

Anesthesia↗
PubMed1984

Ventilatory effects of pre- and postoperative diamorphine. A comparison of extradural with intramuscular administration.

Twenty-two patients were studied before and after major abdominal vascular surgery to determine the effect on ventilation of 5 mg diamorphine given either extradurally or intramuscularly. Diamorphine depressed ventilation maximally at 30 minutes when given by either route. Before operation resting ventilation was reduced by 33% after extradural and 17% after intramuscular diamorphine; PaCO2 increased by an average of 0.5 kPa (either route); ventilation at 7.3 kPa PaCO2 was reduced 40% after extradural and 33% after intramuscular diamorphine. After operation the effect of diamorphine on ventilation was qualitatively similar but resting baseline ventilation was increased from 9.4 to 10.9 litres/minute. The highest individual PaCO2 values were found during the pre-operative study: 6.5 kPa after extradural diamorphine, 6.4 kPa after intramuscular diamorphine. Pain relief was unsatisfactory after intramuscular diamorphine. Four out of six patients requested further analgesia by 3 hours after administration. No patient who received extradural diamorphine required further analgesia for at least 6 hours.

Adult↗
PubMed1984

Ventilatory effects of nitrous oxide during continuous infusion of fentanyl or alfentanil.

Two groups of eight patients received infusions of either fentanyl at 3 micrograms kg-1 h-1 or alfentanil at 20 micrograms kg-1 h-1 as supplements to 66% N2O in oxygen anaesthesia, during and after body surface surgery. At the end of surgery, the N2O was reduced to 50% and after measurement of ventilatory frequency, minute ventilation, and the ventilatory response to carbon dioxide, N2O was discontinued. The opioid infusions were continued for a further hour and the ventilatory measurements repeated. Both sets of measurements were compared with preoperative values. Minute ventilation (P less than 0.01), frequency (P less than 0.01) and the response to carbon dioxide (P less than 0.01) were reduced during the infusion of fentanyl with N2O; with fentanyl alone, minute ventilation (P less than 0.05) and the response to carbon dioxide (P less than 0.01) were reduced but to a lesser degree. The elimination of nitrous oxide from the inspired gas mixture produced an increase in frequency (P less than 0.05) and increases in the slope (P less than 0.01) and ventilation at 7.3 kPa (P less than 0.025) of the carbon dioxide response curve. Minute ventilation (P less than 0.01) frequency (P less than 0.05) and response to carbon dioxide (P less than 0.01) were all reduced during the infusion of alfentanil with nitrous oxide; with alfentanil alone, minute ventilation (P less than 0.01), tidal volume (P less than 0.05), the slope (P less than 0.025) and the ventilation at 7.3 kPa (P less than 0.01) of the carbon-dioxide response curve were still reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Anesthesia↗