Optimal remifentanil dosage for intubation without muscle relaxants in elderly patients

Remifentanil used in combination with propofol provides adequate conditions for tracheal intubation without muscle relaxants. Delivery of the optimal dose is important to prevent poor intubation conditions and drug-related complications. No previous study has investigated the use of a remifentanil-propofol combination in elderly patients.

The aim of the present study was to determine the dose of remifentanil necessary for rapid tracheal intubation without the use of muscle relaxants in elderly patients.

A total of 24 patients >65 years of age with American Society of Anesthesiologists status I-II who were scheduled to undergo elective surgery under general anaesthesia were enrolled. After premedication with glycopyrrolate and midazolam, anaesthesia was induced with 1 mg/kg propofol, and a blinded dose of remifentanil was then infused over 30 s after confirming the patient's loss of consciousness. The remifentanil dose was determined using Dixon's up-and-down method, starting at 2 µg/kg. Intubation was performed 60 s after the loss of consciousness. Intubation conditions were assessed with the Stockholm score and an assessment of excellent or good condition was regarded as being clinically acceptable. The effective dose needed for acceptable intubation conditions in 50 % of the subjects (ED(50)) was determined by Dixon's up-and-down method, and the ED(50) and the effective dose needed for acceptable intubation conditions in 95 % of the subjects (ED(95)) with 95 % confidence intervals (CIs) were determined by probit analysis.

In total, 24 patients were recruited and the median age (interquartile range) was 70 (66-74) years. The ED(50) of remifentanil for tracheal intubation was 1.15 (standard deviation 0.13) µg/kg. The ED(50) and ED(95) of remifentanil obtained from the probit analyses were 1.16 (95 % CI 1.01, 1.29) µg/kg and 1.39 (95 % CI 1.27, 2.13) µg/kg, respectively. Blood pressure and heart rate decreased significantly after propofol and remifentanil administration, but were within 30 % of baseline values.

Combined with 1 mg/kg propofol, 1.39 (95 % CI 1.27, 2.13) µg/kg remifentanil resulted in acceptable intubation conditions within 60 s in 95 % of elderly patients without major complications.