Ephedrine for Reducing Onset Time of Rocurinium in Elderly Patients

Numbers of elderly patients requiring anesthesia and surgery are increasing, and as a group, elderly patients are at high risk of postoperative complications. Aging leads to a progressive impairment of organ function and a decline in physiologic reserve and in the elderly patient population, pharmacodynamics and pharmacokinetics of medications administered during anesthesia may be influenced by the age-related reduction in cardiac output, liver function and renal function. Also, the body composition changes with age and elderly have lower total body water and an increase in body fat.

Neuromuscular blocking agents (NMBAs) are administered during anesthesia to facilitate tracheal intubation. However, in elderly patients onset time of standard doses of NMBAs are prolonged, and for 0.6 mg/kg of rocuronium it is prolonged by 50% when comparing elderly with younger adults (median 135 seconds vs 90 seconds). A prolonged onset time of rocuronium may result in prolonged time to tracheal intubation which aims to secure the patients airway and breathing during anesthesia and thereby prevents pulmonary aspiration and hypoxia. It is therefore relevant to investigate measures to reduce onset time of rocuronium in the elderly.

Ephedrine administered in younger adults undergoing general anesthesia has reduced the onset time of rocuronium 0.6 mg/kg. The mechanism behind this is speculated to be an increase in cardiac output.

It is possible to detect onset time of NMBAs with objective neuromuscular monitoring perioperatively by train-of-four (TOF) stimulation at the ulnar nerve. The effect of ephedrine on onset time of rocuronium has not been assessed in elderly patients above 80 years of age.

The possible benefit of this trial is to investigate whether ephedrine 0.15 mg/kg reduces onset time of rocuronium 0.6 mg/kg in the elderly. This may result in a shorter time to tracheal intubation and also establish better intubating conditions. The results may help to detect the optimal method for administering rocuronium to facilitate tracheal intubation in elderly patients.

The investigators hypothesize that ephedrine 0.15 mg/kg will provide a shorter onset time of rocuronium compared to placebo (saline).

Inclusion criteria

• Age ≥ 80
• Scheduled for elective operations under general anesthesia with intubation
• American Society of Anesthesiologists physical status classification (ASA) I to III
• Informed consent
• Read and understand Danish

Exclusion criteria

• Known allergy to rocuronium or ephedrine
• Neuromuscular disease that may interfere with neuromuscular data
• Indication for rapid sequence induction
• Daily use of beta-blocking agents
• Known cardiac arrythmia (atrial fibrillation, supraventricular or ventricular)