Effect of remifentanil on the auditory evoked response and haemodynamic changes after intubation and surgical incision.
We have observed the effect of intubation and incision, as measured by the auditory evoked response (AER) and haemodynamic variables, in 12 patients undergoing hernia repair or varicose vein surgery who received remifentanil as part of either an inhaled anaesthetic technique using isoflurane or as part of a total i.v. technique using propofol. Anaesthesia was induced with remifentanil 1 microgram kg-1 and propofol, neuromuscular block was achieved with atracurium 0.6 mg kg-1 before intubation, and anaesthesia was maintained with a continuous infusion of remifentanil in combination with either a continuous infusion of propofol or inhaled isoflurane. The AER and haemodynamic variables were measured before and after intubation and incision. The effects of intubation and incision on the AER and haemodynamic variables were not significantly different between the remifentanil-propofol and remifentanil-isoflurane groups. However, the study had a low power for this comparison. When the data for the two anaesthetic combinations were pooled, the only significant effects were increases in diastolic arterial pressure and heart rate immediately after intubation; these were not seen 5 min after intubation. There were no cardiovascular responses to incision. There were no significant changes in the AER after intubation or incision. (+info)
Concentration and second-gas effects in the water analogue.
The water analogue provides a visual model of the process of anaesthetic exchange. In the standard version, a single pipe connects the mouth container to the lung container and the conductance of this mouth-lung pipe is proportional to alveolar ventilation. This implies that inspired and expired ventilations are equal. In fact, with high inspired concentrations of nitrous oxide, early rapid uptake of gas by solution leads to a substantial difference between inspired and expired ventilation which in turn leads to concentration and second-gas effects. It is shown that by representing inspired and expired ventilations separately, and keeping one of them constant while varying the other to compensate for rapid uptake, concentration and second-gas effects are reproduced in the water analogue. Other means of reproducing the effects are reported but we believe that the first method is the most realistic and the most appropriate for teaching. (+info)
Recovery after halothane anaesthesia induced with thiopental, propofol-alfentanil or halothane for day-case adenoidectomy in small children.
We studied recovery from halothane anaesthesia in 93 children, aged 1-3 yr, undergoing day-case adenoidectomy. Children were allocated randomly to receive thiopental 5 mg kg-1 (group TH), alfentanil 10 micrograms kg-1 and propofol 3 mg kg-1 (group PAH) or 5% halothane (group HH) for induction of anaesthesia. In group TH, tracheal intubation was facilitated with succinylcholine (suxamethonium) 1.5 mg kg-1. In groups PAH and HH, tracheal intubation was performed without neuromuscular block, and succinylcholine was used only if required. Anaesthesia was maintained with 1-3% halothane during spontaneous respiration. Times to achieving predetermined recovery end-points were recorded. Quality of recovery was assessed using a score of 1-9 (best to worst) for sedation, crying, restlessness and agitation. A postoperative questionnaire was used to determine the well-being of the child at home, 24 h after operation. Emergence from anaesthesia (response to non-painful stimuli) occurred earlier in group HH (mean 9 (SD 6) min) than in groups PAH (13 (6) min, P < 0.01) and TH (18 (14) min, P < 0.01). Sitting up, walking and home readiness were achieved earlier in groups PAH and HH than in group TH (P < 0.05 for each variable). Children in group TH were more sedated during the first 30 min after anaesthesia than those in the two other groups (P < 0.05) while emergence-related delirium was more common in group HH than in group TH (P < 0.01). Well-being at home was similar in all groups. We conclude that induction of halothane anaesthesia with propofol-alfentanil or halothane provided more rapid recovery and earlier discharge than that with thiopental. (+info)
Haemodynamic stability and ketamine-alfentanil anaesthetic induction.
We have determined if alfentanil could obtund the haemodynamic instability commonly seen at induction of anaesthesia with ketamine. Five groups of ASA I and II patients received ketamine 1 mg kg-1 i.v., preceded by saline (group 1) or alfentanil 10, 20, 30 or 40 micrograms kg-1 (groups 2-5, respectively). Heart rate (HR), mean arterial pressure (AP), postoperative patient complaints and dysphoria were noted. All groups showed increases (P < 0.05) in both HR and AP after administration of ketamine, which were progressively smaller as the dose of alfentanil increased. After tracheal intubation, all groups showed further increases in HR and AP, with groups 3-5 (alfentanil 20-40 micrograms kg-1) showing significant obtundation (P < 0.05) of these increases compared with group 1. No patient in any group reported postoperative dysphoria or dissatisfaction with their anaesthetic. Ketamine 1 mg kg-1 with alfentanil 20-40 micrograms kg-1 provided statistically significant obtundation of the haemodynamic instability that is common with ketamine alone. (+info)
Comparison of recovery of propofol and methohexital sedation using an infusion pump.
Two sedative anesthetic agents administered by an infusion pump were compared during third molar surgery. Forty American Society of Anesthesiologists (ASA) class I or II volunteers were randomly allocated to two groups. All subjects received supplemental oxygen via a nasal hood, fentanyl (0.0007 mg/kg intravenous [i.v.] bolus), and midazolam (1 mg/2 min) titrated to effect. Patients then received either 0.3 mg/kg of methohexital or 0.5 mg/kg of propofol via an infusion pump. Upon completion of the bolus, a continuous infusion of 0.05 mg/kg/min methohexital or 0.066 mg/kg/min propofol was administered throughout the procedure. Hemo-dynamic and respiratory parameters and psychomotor performance were compared for the two groups and no significant differences were found. The continuous infusion method maintained a steady level of sedation. Patients receiving propofol had a smoother sedation as judged by the surgeon and anesthetist. (+info)
Bone marrow harvesting using EMLA (eutectic mixture of local anaesthetics) cream, local anaesthesia and patient-controlled analgesia with alfentanil.
Bone marrow harvesting (BMH) was performed on 40 consecutive allogeneic or autologous donors using EMLA (eutectic mixture of local anaesthetics), local anaesthesia (LA) and patient-controlled analgesia with alfentanil (PCA-A). The effect of alkalinizing the LA solution on reducing pain during LA infiltration in the presence of EMLA was also investigated. EMLA 10 g with occlusive dressing was applied to the harvest sites at least 60 min before BMH. The PCA device was programmed to deliver an intravenous loading dose of 15 microg/kg alfentanil, followed by a background alfentanil infusion of 0.05 microg/kg/min. Demand dose was 4 microg/kg and lockout time was 3 min. Donors were randomized to receive either alkalinized (n = 19) or non-alkalinized (n=21) LA solution (lignocaine 1% with 1:100000 adrenaline). While post-operative nausea and vomiting were the only side-effects, all donors in both groups reported satisfactory pain scores during LA infiltration and satisfactory overall intra-operative comfort scores. They completed BMH using either regimen successfully, found this technique acceptable and would recommend this form of anaesthesia to others. Alkalinizing the LA solution did not significantly improve the pain scores during LA infiltration in the presence of EMLA. In conclusion, BMH can be performed safely using EMLA, LA and PCA-A without major complications. (+info)
Effects of propofol, propofol-nitrous oxide and midazolam on cortical somatosensory evoked potentials during sufentanil anaesthesia for major spinal surgery.
Recording of cortical somatosensory evoked potentials (CSEP) enables monitoring of spinal cord function. We studied the effects of propofol, propofol-nitrous oxide or midazolam during sufentanil anaesthesia on CSEP monitoring during major spinal surgery. Thirty patients with normal preoperative CSEP were allocated randomly to one of the following anaesthesia regimens: propofol (2.5 mg kg-1 followed by 10-6 mg kg-1 h-1) with or without nitrous oxide, or midazolam (0.3 mg kg-1 followed by 0.15 mg kg-1 h-1) combined with sufentanil 0.5 microgram kg-1 h-1 in the propofol and midazolam groups, or 0.25 microgram kg-1 h-1 in the propofol-nitrous oxide group. CSEP were elicited by alternate right and left tibial posterior nerve stimulation and recorded before and after induction (15 min, 1, 2 and 3 h), and during skin closure. CSEP latencies were not significantly modified in the three groups. CSEP amplitude decreased significantly in the propofol-nitrous oxide group (from mean 2.0 (SEM 0.3) to 0.6 (0.1) microV; P < 0.05) but not in the propofol (from 1.8 (0.6) to 2.2 (0.3) microV) or midazolam (1.7 (0.5) to 1.6 (0.5) microV) groups. The time to the first postoperative voluntary motor response (recovery) delay was significantly greater in the midazolam group (115 (19) min) compared with the propofol and propofol-nitrous oxide groups (43 (8) and 41 (3) min, respectively). Consequently, the use of propofol without nitrous oxide can be recommended during spinal surgery when CSEP monitoring is required. (+info)
Anaesthetic effects of pregnanolone in combination with allopregnanolone, thiopental, hexobarbital and flurazepam: an EEG study in the rat.
The anaesthetic interactions of the steroid, 3 alpha-hydroxy-5 beta-pregnan-20-one, in male rats were investigated in different fixed binary combinations with the steroid allopregnanolone (3 alpha-hydroxy-5 alpha-pregnan-20-one), two barbiturates (thiopental and hexobarbital) and the benzodiazepine, flurazepam. Anaesthetic effects were determined using an EEG threshold method. Interactions were assessed using an isobolographic method. The interaction between the two steroids, pregnanolone and allopregnanolone, showed an anaesthetic effect significantly less than additive (antagonistic). The interactions between pregnanolone and the two barbiturates and the benzodiazepine showed an anaesthetic effect significantly greater than additive (potentiation) in all tests performed. These results could be explained by a pharmacodynamic interaction at the hypothetical GABA-benzodiazepine-barbiturate-steroid complex in the CNS. (+info)