Intravenous anaesthesia with propofol and alfentanil. The influence of age and weight

Sixty healthy patients undergoing body surface surgery were anaesthetised with continuous infusions of propofol (200 micrograms/kg/minute) and alfentanil (0.25 microgram/kg/minute). Additional bolus doses of propofol (20 mg) were given if movement occurred. The incidence of patient movement in response to skin incision was significantly less in patients over 45 years of age than in those below 45 years (p less than 0.05). Maintenance dosage of propofol sufficient to abolish movement decreased with increasing age (p less than 0.001). Systolic blood pressure decreased in most patients over the first 10 minutes of anaesthesia and the magnitude of this decrease increased with age (p less than 0.0001). These parameters did not correlate strongly with body weight. Dose requirements of propofol are not the same for patients of all ages and strongly suggest that young and old patients should not be treated as a homogeneous group, either for investigative or clinical purposes.     

Ketamine as analgesic for total intravenous anaesthesia with propofol

A prospective study of 18 patients who underwent noncardiac surgery was performed to study the use of ketamine as an analgesic during total intravenous anaesthesia with propofol. A comparison was made with the combination propofol/fentanyl. The propofol/ketamine combination resulted in haemodynamically stable anaesthesia without the need for additional analgesics. Postoperative behaviour was normal in all patients and none of the patients reported dreaming during or after the operation. Propofol seems to be effective in eliminating side effects of a subanaesthetic dose of ketamine in humans. We recommend the propofol/ketamine combination for total intravenous anaesthesia for surgery when stable haemodynamics are required.     

Total intravenous anaesthesia with propofol or inhalational anaesthesia with isoflurane for major abdominal surgery: Recovery characteristics and postoperative oxygenation—an international multicentre study

Two hundred and ten adult patients undergoing open cholecystectomy, vagotomy or gastrectomy were included in a randomised multicentre study to compare postoperative nausea and vomiting, oxygen saturations for the first three postoperative nights, time to return of gastrointestinal function, mobilisation, and discharge from the hospital following induction and maintenance of anaesthesia with propofol and alfentanil or with thiopentone, nitrous oxide, isoflurane and alfentanil. Recovery from anaesthesia was significantly faster in the propofol group (mean (SD) times to eye opening and giving correct date of birth of 14.0 (SD 13.8) and 25.5 (SD 29.5) minutes, and 18.5 (SD 14.8) and 35.5 (SD 37.2) minutes in the propofol and isoflurane groups respectively). There was significantly less nausea in the propofol group (15.4%) than in the isoflurane group (33.7%) in the first two postoperative hours (p < 0.003) but not thereafter. There were no significant differences between the groups in any other recovery characteristics. The incidence of hypoxaemia (arterial oxygen saturation less than 93%) was close to 70% in both groups for the first three postoperative nights, indicating the need for oxygen therapy after major abdominal surgery.     

Comparison of propofol and thiopentone for induction of anaesthesia in premedicated patients

Thirty premedicated ASA I or II patients scheduled for minor gynaecological surgery, were randomly allocated to receive either 1.5 mg/kg or 2 mg/kg propofol of the new emulsion formulation, or 4 mg/kg thiopentone, given over 20 seconds. Anaesthesia was successfully induced in all 30 patients. The mean (SEM) induction times were for propofol 1.5 mg/kg 33.3(3.2) seconds, for 2 mg/kg 30.5(2.7) seconds and for thiopentone 34.6(2.7) seconds. The incidence of apnoea greater than 10 seconds, was respectively 60, 80 and 80%, and the mean duration of apnoea 30.8(5.3), 37.1(5.0) and 23.7(5.0) seconds. The mean systolic blood pressure decreased after propofol 1.5 mg/kg by 16.0 mmHg, after 2 mg/kg by 18.6 mmHg, and increased after thiopentone by 1 mmHg, 2 minutes after injection. Heart rate increased significantly 2 minutes after thiopentone by an average of 15.1 beats/minute, but not after propofol. Pain was not reported during or after the injection. No major adverse reactions occurred at induction or during maintenance of anaesthesia with an inhalation agent. One patient who received 2 mg/kg propofol and isoflurane vomited for 24 hours. The recovery of anaesthesia after propofol induction, was quicker than after thiopentone.     

Pain on injection of propofol

Pain on injection of propofol is a common problem, the cause of which remains unknown. The chemical properties and preparation of propofol, proposed mechanisms for the cause of the pain and clinical strategies to prevent pain on injection of propofol are reviewed in the hope of shedding some light on the subject.     

Pain on injection of propofol. A comparison of cold propofol with propofol premixed with lignocaine

Propofol is frequently associated with pain on injection. Previous studies have suggested that chilling of the propofol decreases pain significantly. This prospective, randomised, double-blind trial was designed to assess the effectiveness of cold propofol compared with propofol premixed with lignocaine in minimising pain on injection. Patients were allocated to one of four groups: propofol + lignocaine 0.1 mg.kg⁻¹, propofol + lignocaine 0.2 mg.kg⁻¹, cold propofol and a control group consisting of propofol premixed with normal saline and maintained at room temperature. The results of this study show that cold propofol is associated with a very high incidence of injection pain while lignocaine 0.1 mg.kg⁻¹ premixed with propofol significantly decreases the incidence of pain (p < 0.001). Increasing the dosage of lignocaine above 0.1 mg.kg⁻¹, however, does not significantly decrease the incidence of pain further. The addition of lignocaine also significantly decreases the incidence of excitatory side-effects.     

Ventilatory effects of propofol during induction of anaesthesia

The ventilatory effects of induction of anaesthesia with either propofol 2.5 mg/kg or thiopentone 4.0 mg/kg have been observed in patients premedicated with either atropine alone or papaveretum and hyoscine. Induction of anaesthesia with propofol was accompanied by a greater degree of ventilatory depression which was of longer duration than following thiopentone. The effect was accentuated by the opioid premedication.     

A comparison of midazolam co-induction with propofol predosing for induction of anaesthesia

In a double-blind, placebo-controlled study of 90 ASA 1 and 2 patients scheduled for elective surgery we compared the effect of pre-administering midazolam 2 mg or propofol 30 mg on the dose of propofol subsequently required to induce anaesthesia. Using loss of response to verbal command and tolerance to placement of a facemask as end-points, the dose of propofol required to induce anaesthesia was significantly smaller in the patients given propofol (1.87 mg.kg-1) or midazolam (1.71 mg.kg-1) when compared to the control group (2.38 mg.kg-1). Although the decrease in blood pressure following induction was no difference between the two study groups and the decrease was felt not to be of clinical significance in this group of patients. As propofol is presented ' ... for use in a single patient only' and the technique of predosing with propofol allowed induction of all patients with less than 200 mg (a single ampoule), we question on a cost basis whether midazolam co-induction is necessary to reduce propofol induction doses.     

Light anaesthesia with propofol for paediatric MRI

Anaesthetic techniques and monitoring equipment may interfere with the technical demands of magnetic resonance imaging. The purpose of this study was to evaluate the safety and efficacy of a light anaesthetic technique with intravenous propofol in nonintubated children. In 20 neuropaediatric patients sedation was induced with propofol 1 mg.kg-1, followed by a continuous infusion titrated to produce adequate immobilisation. Oxygen, 4 l.min-1, was administrated by paediatric face mask. Respiratory rate, end-tidal carbon dioxide tension and oxygen saturation were continuously monitored. In 10 patients capillary blood gas tensions were determined 3 and 20 min after the procedure. Data are reported as mean (SD) and the mean (SD) total propofol dose was 5 (2) mg.kg-1.h-1. Oxygen saturation remained constantly higher than 96% in all patients. End-tidal carbon dioxide tension varied between 35 (7) mmHg 3 min after induction, and 41 (6) mmHg 30 min after the start of the procedure. End-tidal to capillary PCO2 difference was 4 (3) mmHg. Within 20 min after the end of the procedure all patients were fit for dismissal to the ward. One imaging sequence out of 49 was repeated because of movement artefacts. In conclusion, intravenous propofol sedation appears to be a safe and reliable technique for paediatric sedation during magnetic resonance imaging.     

Comparison of etomidate and propofol for anaesthesia in microlaryngeal surgery

Propofol and etomidate were compared as hypnotics in total intravenous anaesthesia for microlaryngeal surgery combined with jet ventilation. Two groups of 15 patients were studied. In group 1, propofol 2.0 mg/kg was used for induction. For maintenance a continuous infusion of 12 mg/kg/hour was used for the first 10 minutes, followed by 9 mg/kg/hour for the next 10 minutes and 6 mg/kg/hour thereafter. In group 2, the induction dose of etomidate was 0.3 mg/kg followed by continuous infusion of 1.8 mg/kg/hour for 10 minutes, 1.5 mg/kg/hour for the next 10 minutes and 1.0 mg/kg/hour thereafter. Alfentanil was given for analgesia and suxamethonium for muscle relaxation. The propofol group showed better surgical conditions, more stable anaesthesia and better recovery according to the Steward score. Recovery times to opening eyes on command were comparable for both groups.     

The effect of prophylactic metaraminol on systemic hypotension caused by induction of anaesthesia with propofol in patients over 55 years old

We conducted a double-blind, randomised, placebo-controlled study evaluating the efficacy of prophylactic metaraminol for preventing propofol-induced hypotension. Thirty patients aged 55-75 years undergoing general anaesthesia were randomly allocated to receive either metaraminol 0.5 mg or saline before administration of fentanyl 1 microg.kg(-1) and propofol 2 mg.kg(-1). Induction of anaesthesia was associated with a decrease in mean and systolic arterial pressure in both groups (p = 0.0001). However, there was no significant difference between the two groups. These results show that prophylactic use of metaraminol 0.5 mg does not prevent the decrease in blood pressure following fentanyl and propofol induction in older patients.