Effect of Nutritional Status on Neuromuscular Blockade: Vecuronium vs. Atracurium

Abstract

Although there are few available data on the use of muscle relaxants in malnourished patients, we tried in this study to evaluate the response of different grades of malnutrition to the neuromuscular blocking agents; Vecuronium and Atracurium.

This study compared the onset of time, time to no response to TOF stimulation, duration of action of initial dose and supplementary doses, and time of reverse between mild, moderate and severe malnourished patients with both non­ depolarizing neuromuscular blocking agents, Vecuronium and Atracurium.

Eighty patients of both sexes aged between 20 to 60 years scheduled for elective and emergency surgical procedures were included in this study. They were divided into four groups, 20 patients each (control, mild, moderate and severe malnourished patients). Each group is subdivided into two sub­ groups A and B

After premedication, anaesthesia was induced with fentanyl and thiopentone. Then a control response to neuromuscular stimulus was obtained in all groups fowled by injection of the neuromuscular blocking agents to facilitate endotracheal intubation (vecuronium is sub-group A and Atracurium in sub­ group B). Anaesthesia is maintained by 40 % oxygen in nitrous oxide with controlled mechanical ventilation using halothane 0.5 -1.0 %

All grades of malnutrition prolonged the onset time and time to no response to TOF stimulation ofvecuronium induced muscle relaxation. But severe malnutrition only shortens the onset time and time to no response to TOF stimulation of atracurium induced neuromuscular block. While mild and moderate malnutrition have no effect on atracurium induced muscle relaxation.

Also, all grades of malnutrition shorten the duration of action of initial dose and supplementary doses in vecuronium induced neuromuscular block. While severe malnutrition only reduces the duration of initial dose and supplementary doses in atracurium induced bock.

Reversal with neostigmine was easy to all patients without significant difference between malnourished and well­ nourished patients in all groups with both muscle relaxants.

We conclude that malnourished patients are less sensitive to the effect of muscle relaxants. All grades of malnutrition need higher doses of vecuronium while severe malnutrition only needs higher doses of atracurium. So, it is recommended to increase the dose of neuromuscular blockers in malnourished patients or to use the ideal body weight to calculate the intubating and supplementary doses.