Factors that influence the induction dose of propofol

Factors that influence the induction of anaesthesia with propofol were investigated in a prospective study of 1000 patients. Pre-operative albumin and urea concentrations correlated with the minimum induction dose of propofol, but less strong correlations were found with haemoglobin, globulin and total protein concentrations. Age was an important influence on the induction dose of propofol (r = -0.34) which was also closely related to ASA grade. Induction of anaesthesia with propofol is dependent on a number of variables, and this study suggests that pre-operative albumin and urea concentrations are important.     

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.     

The effects of speed of injection on induction with propofol A comparison with etomidate

One hundred and eighty female patients received either propofol 2.5 mg/kg or etomidate 0.3 mg/kg injected over 20, 40 or 80 seconds for induction of anaesthesia after premedication with temazepam 20 mg. The mean induction times for both etomidate and propofol were significantly reduced with increasing speed of injection. The mean induction times for etomidate were significantly less than propofol at the slower rates of injection. At each speed of injection, the decrease in systolic, mean and diastolic arterial blood pressures with etomidate were less than with propofol. The decrease in systolic blood pressure was not significantly affected by injection speed for either drug. Apnoea occurred significantly more frequently with propofol than with etomidate at each speed of injection and the incidence of apnoea greater than 60 seconds with propofol was significantly higher when injected over 20 seconds than 80 seconds. The incidence of pain on injection was unaffected by injection speed for either drug. The incidence of myoclonus and (or) hypertonus was significantly higher following etomidate.     

Propofol: clinical strategies for preventing the pain of injection

Eight modes of administration of propofol were assessed in order to minimise the pain of injection. An intravenous bolus injection in the antecubital fossa was the only approach that caused no pain. When administered intravenously in the dorsum of the hand the pain score and the number of patients who experienced pain was reduced significantly by mixing the agent with lignocaine when compared with a bolus injection. Slowing the speed of injection caused the greatest discomfort. An indirect biochemical mechanism for the pain is proposed.     

Depression of Monocytes and Lymphocytes by Stress-Related Humoral Factors and Anaesthetic-Related Drugs

The in vitro effects of six anaesthesia-related drugs and five stress-related serum factors on monocyte-mediated cytolysis and thymidine uptake in mitogen-(PHA)-stimulated lymphocytes have been studied. Thiopentone depressed both the monocyte and lymphocyte function in a dose-dependent way. However, at thiopentone concentrations which may be present in the serum after a single intravenous anaesthesia induction dose, the monocyte depression was moderate and depression of the lymphocytes was not observed. The other drugs tested, fentanyl, morphine, pancuronium, diazepam and bupivacaine, did not alter the cellular functions significantly. Prostaglandin-E2 in concentrations of 10^-6 and 10^-7 M markedly depressed monocyte-mediated cytolysis. Cortisol, catecholamines and serotonin did not alter this function. However, a synergistic depressive effect of the combination of prostaglandin^ and Cortisol was observed. The proliferative response of PHA-stimulated lymphocytes was depressed by Cortisol in concentrations of 2200 nmol/1 and 1100 nmol/ I. Again, there was a marked synergistic effect of the combination of Cortisol and prostag!andin-E2, while prostaglandin-E2 alone, catecholamines and serotonin did not influence the PHA-response. A possible explanation for the depression of monocyte-mediated cytolysis and lymphocyte-thymidine uptake during and after surgery under general anaesthesia may be the combined effect of endocrine and local stress factors.