Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Ambulatory Anesthesia
It is well known that tracheal extubation is usually associated with hemodynamic changes. This sudden increase in blood pressure (Bl.P) and heart rate (H.R) associated with tracheal extubation will aggravate the already increased Bl.P and H.R which commonly occurs towards the end of anestheia and surgical procedure, with the possibility of increased anesthetic morbidity and mortality. Myocardial ischaemia was reported during both tracheal intubation and extubation . Propofol was found to block catecholamine and hemodynamic responses to endolaryngeal procedures . This study was designed to evaluate the effects of I.V propofol 0.5 mg/kg ideal body weight given 2 min before tracheal extubation, on hemodynamic changes and the quality of emergence from anesthesia.
METHODS: This study was performed, after IRB approval on 80 adult consented patients ASA I&II of both sexes scheduled for elective surgical procedures. Patients were randomly divided into 2 equal groups; propofol (P) and control(C) groups. All patients received midazolam premedication and standard general anesthesia which was induced with fentanyl 1[micro sign]gm/kg, propofol 2 mg/kg and atracurium 5 mg/kg for tracheal intubation. Anesthesia was maintained with 66% N2 O in O2, isoflurane and bolus doses of fentanyl and atracurium as needed. At the end of surgery N2 O and isoflurane were discontinued, residual neuromuscular block was antagonized with neostigmine and glycopyrolate. Trachea was extubated nearly 2 min after injection of the pretreatment solution which was propofol 0.5mg/kg in P group and an equal volume of normal saline in C group. Systolic blood pressure (S Bl.P) and H.R were measured on 3 occasions; at the end of surgery, just before extubation and 1 min after extubation. The quality of tracheal extubation was scored as 0= no cough or strain, 1=moderate coughing, 2= high degree of coughing or straining, 3= poor extubation with laryngeospasm. T-test was used for statistical analysis with P < 0.05 being significant.
RESULTS: Both groups were matched regarding age, sex and weight. Tracheal extubation was associated with a significant increase in S Bl.P & H.R (P<0.05) in C group, while P group showed no significant changes. Propofol significantly attenuated coughing and strain during extubation, 35 patients (88%) had a score of 0 in P group compared to 19 patients (48%) in C group.
DISCUSSION: Propofol single dose (0.5 mg/kg ideal body weight) proved to be very effective in minimizing hemodynamic response to tracheal extubation. The exact mechanism of these hemodynamic changes is not clear but it is believed to be associated with the release of catecholamines leading to increased H.R, myocardial contractility and systemic vascular resistance with increased O2 demands of the heart . The effectiveness of propofol in attenuating these hemodynamic changes is related to its vasodilating effect and negative inotropic properties. While the ability of propofol to obtund laryngeal reflexes accounts for smooth emergence from general anesthesia. The rapid onset of action and the short duration of propofol makes it an ideal drug for attenuating the cardiovascular responses to tracheal extubation.
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