THE EFFECT OF PRIMING WITH VECURONIUM AND ROCURONIUM ON YOUNG AND ELDERLY PATIENTS

The priming principle consists of administering a subparalyzing dose o f nondepolarizing neuromuscular blocking drug 3-6 min before giving a second dose for tracheal intubation. This study was performed to obser ve the effects of priming doses of vecuronium and rocuronium on pulmon ary function tests and muscular weaknesses in young (25-35 yr of age) and elderly (65-73 yr of age) patients. Ten young and 10 elderly patie nts were each placed in vecuronium and rocuronium groups. Oxygen satur ation and train-of-four (TOF) ratio were determined, and pulmonary fun ction tests were performed. Then 20% of the 95% effective dose (ED95) of the muscle relaxants was given intravenously. All tests were perfor med again 4 min after vecuronium and 3 min after rocuronium. Other sig ns of muscular weaknesses were also recorded. Elderly patients showed more signs of muscle weakness in both groups. The TOF ratio was 0.77 a nd 0.79 in the elderly rocuronium and vecuronium groups, respectively, and 0.89 and 0.90 in the young rocuronium and vecuronium groups, resp ectively. Dynamic spirometry revealed decreases in forced expiratory v olume in 1 s and forced vital capacity in both groups, and no signific ant changes in peak expiratory flow rate. The expiratory reserve volum e was reduced more in the elderly groups. Oxygen saturation decreased in both groups. We conclude that oxygen saturation, pulmonary function , and muscle strength decrease more in the elderly than in their young er counterparts from priming doses of vecuronium or rocuronium. Implic ations: The priming principle consists of giving a subparalyzing dose of muscle relaxant 3-6 min before giving a second dose for tracheal in tubation. We found that priming doses of vecuronium and rocuronium pro duced greater decreases in oxygen saturation and pulmonary function in the elderly (aged 65-73 yr) than their younger (aged 25-35 yr) counte rparts. Priming may not be a safe approach in elderly patients.