Prevention of haemodynamic response to endotracheal intubation during anaesthesia combining TCI of propofol and a single dose of remifentanil

Saidane G, Ducart A, Schmartz D, Engelman E, Barvais L

Departement of Anesthesiology and Reanimation, CUB ERASME, route de Lennik 808, Brussels, Belgium

Objectives : a relation between the blood concentration of propofol and the level of hypnosis or the bispectral index has been demonstrated (1). However, propofol alone does not block the haemodynamic response to a painful stimulus such as endotracheal intubation (ENT). Remifentanil is a new opioid drug with a very short onset and duration of action. Pharmacokinetic simulation shows that a bolus of 1 µg/kg of remifentanil generates a theoretical concentration of 4 ng/ml at the effect site after 90 seconds in a 40 year old patient (2). This theoretical peak effect concentration decreases below to 0.6 ng/ml after 10 minutes. Our aim was to study the haemodynamic response of ENT during a TIVA technique combining TCI of propofol titrated to maintain the effect site concentration at the level associated with loss of consciousness (LOC) and a bolus dose of 1µg/kg of remifentanil administered 90 seconds before ENT.

Patients and method : 20 ASA I or II patients, 18 to 69 years old, were included in the study. No patient was on beta blocker or antihypertensive therapy or received any other opioid drug the week before. 0.5 mg alprazolam was given orally as premedication. Anaesthesia was induced using a Diprifusor system. The initial plasma target concentration was 4 µg/ml. When loss of consciousness was obtained, 0.2 mg/kg of cisatracurium was given. The theoretical effect concentration of propofol was maintained at the same level and the patient was ventilated by an oxygen/air mixture. A single bolus of 1 µg/kg of remifentanil was given 90 seconds before ENT. No other stimulation was applied during the following 10 minutes. The haemodynamics parameters (SAP, DAP, HR) were measured before anaesthesia (A), at loss of consciousness (LOC), one minute after remifentanil (R+1), at the time of ENT (T0), every minute during a 5 minutes period (T1 to T5) and 10 minutes after intubation (T10). A Friedman variance analysis, followed by a Wilcoxon test was used as statistical test.

Results: LOC has been obtained between 3 and 4 µg/ml of the theoretical effect concentration of propofol in all the 20 patients. Compared with the reference values before the start of anaesthesia (A), LOC has been associated with a significant fall of SAP and DAP. The bolus dose of 1 µg/kg of remifentanil has caused an additional reduction of SAP, DAP and HR at R+1. During ENT and the 10 following minutes, no patient has presented an increase in SAP, DAD or HR higher than the values before the start of anaesthesia (A). Moreover, no patient has required any vasopressive or anticholinergic drug. However, an episode of SAP < 85 mmHg has been recorded in two patients (82/41, 43 years; 84/49, 65 years). One patient has presented an episode of bradycardia (HR = 46 compared to a value of 54 before anaesthesia).

			LOC vs R+1(p<0.01), T0 vs T3,4,5(p<0.01), T0 vs T10 (p<0.05)
	A : Awakening, LOC :Loss of Consciousness R : remifentanil, T0 : intubation A vs LOC ( p<0.01), LOC vs R+1 ( p<0.01)
		Heart Rate
Diastolic Arterial Pressure

Conclusion: In ASA I or II patients, a total intravenous anaesthesia technique combining a stable effect concentration of propofol between 3 and 4 µg/ml (Diprifusor) associated with LOC and a single dose of 1 µg/kg of remifentanil allows to prevent the haemodynamic answer to the strong stimulus of endotracheal intubation without any residual episode of haemodynamic disturbances in the absence of any other surgical stimulus.

References : 1. Sebel P et al. : Anesth Analg, 84: 891-99; 1997.

2. Minto et al. : Anesthesiology 86: 10-23; 1997