[Effects of obesity on prolonged thiopental surgical anesthesia: Iranian fat tailed type sheep used a new model]

ABSTRACT

Anesthesiologist in human medicine noticed that patients with higher defree of fat deposit need more anesthetics and also recovery period in these patients is longer than normal patients. These indicate the important role of fat deposit that may play in prolonged thiopental anesthesia. Unfortunately, due to lack of clinical model, to the best of our knowledge, no experimental studies has been yet designed to prove the experience that anesthesiologist have obtained during clinical practice. Consequently, we thought that the Iranian fat tailed type sheep could be the best model to be used; since this kind of sheep could deposit a large amount of fat up to 10% of its body weight or more, depending on strain and age, at its tail area. Prolonged surgical anesthesia was induced in Iranian fat tailed type sheep with initial dose of 26.51 +/- 5.82 mg/kg of body weight, and maintained successfully by repeatedly injecting the maintenance dose of 22.97 +/- 5.26 mg/kg, 20.31 +/- 5.67 mg/kg and 14,10 +/- 5.31 mg/kg of thiopental for 1st., 2nd. and 3rd. hour of anesthesia respectively in this study. Maintenance dose in tail amputed animal is decreased respectively from normal sheep 22,97 +/- 5.26 to 21.99+6.34, 20.31 +/- 5.67 to 14.75+4,61 and 14.10 +/- 5,31 to 8.56 +/- 3.20 mg/kg during 1st., 2nd. and 3rd. hour of anesthesia. The differences between maintenance dose in normal and amputated tail sheep in 2nd. and 3rd hour of anesthesia could be attributed to fat removal in amputated tail sheep. Average recovery time in normal animals was 358.10 +/- 65.77 minutes. But, recovery time in tail amputed animal significantly decreased from 358.10 +/- 65.77 to 204.50+88.49 minutes. The differences could be due to higher metabolism and excretion rate in amputated tail sheep; since, there is higher plasma concentration of thiopentail in this group of sheep, due to lack of high fat tissue, consequently, the drug gets metabolized and excreted faster and recovery period becomes shorter. Results obtained in this study could firmly prove the important role of obesity in human and veterinary anesthesia. These data also suggest that anesthesiologist should more seriously consider the obesity at the time of practice. All this experiment proves that sheep is a good model in this kind of research