Comparative assessment of the effects of alfentanil, esmolol or clonidine when used as adjuvants during induction of general anaesthesia.

BACKGROUND AND OBJECTIVE: This randomized, double-blinded, prospective study compared the effects of clonidine, esmolol or alfentanil on the level of hypnosis and haemodynamic responses to intravenous induction of anaesthesia and endotracheal intubation. METHODS: Forty-five patients scheduled for elective surgery were allotted to one of three groups. They were given either alfentanil 3 microg kg(-1) min(-1) (n = 15); esmolol 1 mg kg(-1) min(-1) (n = 16) or clonidine 3 microg kg(-1) (n = 14) as a 10 min infusion. The infusions of alfentanil and esmolol, but not of clonidine, were maintained during endotracheal intubation. Anaesthesia was induced with midazolam (2 mg) and thiopental as required to suppress the eyelash reflex. Atracurium (0.5 mg kg(-1)) was given to produce neuromuscular block. Mean arterial pressure, heart rate, and bispectral index were recorded on arrival (baseline), after study drug infusion, after injecting midazolam and thiopental, as well as after endotracheal intubation. ANOVA and chi2-test were used for analysis. RESULTS: Blood pressure, heart rate and the bispectral index were unaltered by the study drugs, but thiopental requirements were reduced by alfentanil and clonidine (P < 0.014). Mean arterial pressure values (mean +/- standard error of mean) in the alfentanil, esmolol and clonidine groups were: baseline: 107.8 +/- 3.8; 106.6 +/- 3.9; 103.4 +/- 3.7 mmHg; after thiopental: 74.0 +/- 4.2; 85.6 +/- 4.3; 94.2 +/- 4.1 mmHg and after endotracheal intubation: 91.7 +/- 5.3; 114.1 +/- 6.9; 123.6 +/- 5.6 mmHg, respectively (two-way ANOVA, P < 0.001). Mean arterial pressure changed significantly after intubation from baseline (P < 0.001) after alfentanil (-15%) and clonidine (+20%) but not after esmolol (+7%), while the changes between pre- and postintubation values were similar in all groups (24-33% increase). The bispectral index indicated that all patients had an adequate level of hypnosis, but the variability was higher in the esmolol group (P < 0.002). CONCLUSIONS: None of the study drugs blocked the increase in mean arterial pressure induced by endotracheal intubation, but esmolol provided better overall haemodynamic stability. All groups had an adequate level of hypnosis.

Pharmacy savings generated by preoperative administration of clonidine.

STUDY OBJECTIVE: To evaluate the effects of the preoperative administration of clonidine by the oral, intramuscular (i.m.), or epidural routes, on isoflurane expense during total abdominal hysterectomy. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: University hospital. PATIENTS: 80 ASA physical status I and II patients scheduled for total abdominal hysterectomy. INTERVENTIONS: Patients were distributed into four groups of treatment: oral, i.m., epidural, and control. Each group received 300 microg clonidine according to the treatment group, plus placebo by the other routes. The control group received placebo by all three routes. Depth of anesthesia was evaluated by changes in blood pressure and heart rate over baseline values. Cost evaluation was based on three components: expense of isoflurane, cost of 300 microg of clonidine (tablets or ampoules), and the disposable material required to dispense clonidine to each group. MEASUREMENTS AND MAIN RESULTS: Groups were comparable regarding demographic data, duration of surgery, and time to discharge from recovery room. Postoperatively, none of the patients had recall of intraoperative events. Clonidine reduced isoflurane pharmacy cost by approximately 45%, regardless of the route of administration. However, when cost of clonidine and the disposable equipment used for its administration were taken into account, the cost of the epidural kit surmounted the savings in isoflurane expense. CONCLUSION: In the patient population studied, premedication with 300 microg oral, i.m., or epidural clonidine, similarly and significantly reduced the expense of isoflurane during general anesthesia of an approximate duration of two hours. However, the cost of the epidural kit offsets the savings in isoflurane.

Comparative assessment of the anaesthetic and analgesic effects of intramuscular and epidural clonidine in humans.

PURPOSE: The aim of the study was to assess and compare in analogous controlled experimental conditions, the anaesthetic sparing and analgesic effects of the same dose of clonidine administered by the intramuscular (im) and epidural (ep) routes. METHODS: We used a randomized, double blind and placebo controlled protocol. Sixty patients undergoing abdominal hysterectomy were distributed into three groups who, 30 min before surgical incision, received: 300 micrograms ep clonidine plus im saline; ep saline plus 300 micrograms im clonidine; or ep and im saline (ss). General anaesthesia was maintained with 60% N2O in O2, and isoflurane administered at concentrations to maintain mean arterial pressure (MAP) and heart rate (HR) within 20% of basal values. Isoflurane requirements (mass spectrometry), cardiovascular variables (MAP, HR), and plasma concentrations of glucose, cortisol and prolactin were evaluated at critical time points. In the recovery room (RR), sedation (Ramsay) and pain intensity (VAS) were estimated at the time of analgesia request (TAR). RESULTS: Intramuscular and ep clonidine decreased isoflurane requirements similarly by about 85% (P < 0.001). Patients in the ep group had lower MAP (P < 0.03) and HR (P < 0.001) than in the im group, but im and ep clonidine similarly blunted the plasma prolactin increase induced by intubation. In RR, ep but not im clonidine (P < 0.01) induced postoperative analgesia demonstrated by a prolonged TAR 80.8 +/- 7.3 (ep) 35.9 +/- 3.2 (im) and 44.5 +/- 5.1 (ss) min and a lower VAS (P < 0.05). CONCLUSIONS: Epidural and intramuscular clonidine decreased isoflurane requirements similarly, but only the epidural route provided postoperative analgesia, suggesting a spinal site for the analgesic action.

Anesthesia for angioembolization of brain arteriovenous malformations: a retrospective assessment.

We reviewed the anesthetic management of 55 patients under 18 years of age during angioembolization of arteriovenous malformations. Patients were grouped according to age: less than 1 month (A), 1-11 months (B), 1-5 years (C) and 7-13 years (D). All had general endotracheal anesthesia. In groups A and B, approximately 43% received pure narcotic and 43% balanced while only 14% had pure inhalational anesthesia. In groups C and D, 41 and 52% received pure inhalation and balanced anesthesia, respectively, while only 7% had pure narcotics. Hypotension was induced in 50% (C and D) and in 20% (A and B) of the patients. Intraoperative lasix or phlebotomy was used in 28, 16, 13 and 0% of groups A, B, C and D, respectively. Two arrests occurred immediately after the injection of the embolizing material. From our review, no single type of anesthesia can be advocated over all others. The use of invasive monitoring (arterial and central venous lines), precise fluid management and the avoidance of nitrous oxide will help to decrease the incidence of intraoperative complications during anesthesia.