A bispectral index guided comparison of target-controlled versus manually-controlled infusion of propofol and remifentanil for attenuation of pressor response to laryngoscopy and tracheal intubation in non cardiac surgery

Target-controlled infusion is a new delivery system for intravenous anesthetic agents with which the anesthetist targets a plasma or effect-site drug concentration to achieve a predetermined effect. With this system, the tedious task of calculating the amount of administered drug required to achieve the target concentration is left in charge of a microprocessor which commands the infusion device. In this prospective study we compared alterations in blood pressure and heart rate from initiation of induction of anesthesia until 3 minutes after tracheal intubation in two methods of drug infusion, target-controlled infusion (TCI) and manually controlled infusion (MCI). Total anesthetic drug used until 3 minutes after intubation and level of produced hypnosis also were compared between two methods. METHODS: 40 patients were enrolled in this clinical trial study and were allocated randomly in two groups, each group consisting of 20 patients. In TCI group, patients received propofol and remifentanil with TCI pump to achieve 7 ug/ml and 4 ng/ml as plasmatic target drug levels, respectively. In MCI group, patients received propofol 2 mg/kg and remifentanil 1 ug/kg of body weight with manually controlled infusion. Both groups received succinylcholine as muscle relaxant to facilitate laryngoscopy and tracheal intubation. Bispectral index (BIS) was passively recorded in two groups to compare the level of hypnosis. Blood pressure (BP) and heart rate (HR) were recorded at 5 different times (T-l, TO, Tl, T2 and T3). Independent t-test and paired t-test were used for data analysis. RESULTS: Systolic arterial pressure (SAP) was not different at T-l between two groups but systolic hypotension was seen in MCI group more than TCI group at TO (P 0.05). Systolic hypertension was more common in MCI group after intubation; i.e. SAP showed significant differences in Tl, T2 and T3 between two groups (P 0.05). Mean arterial pressure (MAP) showed significant difference only at TO and Tl between two groups. Also, heart rate in MCI group was higher than that in TCI group at Tl and T2. Mean used propofol was 128.10 ± 11.30 mg in MCI group versus 140.90 ± 16.21 mg in TCI group (P 0.05) and the least BIS value recorded was 31.4 ± 10 in MCI group versus 42.5 ± 12.3 in TCI group (PO.05). CONCLUSIONS: Hypotension in MCI group was seen more frequently than that in TCI group after induction and before laryngoscopy (TO). Hypertension and tachycardia were seen in MCI group more commonly than those in TCI group after laryngoscopy and tracheal intubation. Then, we recommend TCI technique in high risk patients for attenuation of the pressor response to laryngoscopy and tracheal intubation. Also, we recommend further researches in other educational centers to compare the effect-site TCI with plasmatic TCI in controlling pressor response.