Title: 
Comparison of opioid free anaesthesia with opioid anaesthesia on postoperative shivering in morbidly obese patients scheduled for bariatric surgery. 
 
Author(s): Persyn J. 
Institute(s): UGent, Dept of Anaesthesiology, Gent, Belgium 
Text:

Introduction 
Post-anaesthetic shivering (PAS) occurs frequently. The primary cause is believed to be peri-operative hypothermia caused by anaesthetic induced vasodilatation and inhibition of thermoregulation while exposed to a cold environment. Research has shown that several drugs including the opioids meperidine and tramadol, clondine, dexmedetomidine, ondansetron and ketamine treat and prevent shivering by reducing the shivering threshold temperature. In addition, several studies concluded that patients had significant less shivering and less discomfort of feeling cold when given opioid free anaesthesia. This trial tries to verify whether opioid free anaesthesia (OFA) has a significant impact on loss in core temperature and subsequent shivering, as compared to opioid anaesthesia (OA).  

Method 
50 patients undergoing bariatric surgery were randomly assigned to either the OFA group (n=25) or the  OA group (n=25). Core body temperature was registered with the Spot On system with an interval of 15 minutes. The period and intensity of shivering was documented by specified members in the recovery room.  

Results 
No differences were observed between OFA and OA in terms of mean temperature decrease (temperature pre-induction minus temperature extubation divided by length of procedure –T-test – equal variances: p>0.05). However differences were seen in the occurrence of post-operative shivering. In the OA group 12 out of 25 patients shivered, as compared to 1 out of 25 in the OFA group. Binary logistic regression showed opioid-use as a predictor of shivering (p=0.005). The odds ratio of shivering in the OA group was 22.154. Other variables, as the mean core body temperature decrease, length of procedure, age and weight did not have an influence on PAS (p>0.05) .

Conclusion 
A significant (p< 0,005) difference in post-anaesthetic shivering was found between OFA and OA groups  (1/25 versus 12/25 resp),  which could not be related to the intra- and peri-operative drop in core body temperature. No other variables were statistically linked to provoke shivering in this study.

Comparison of opioid free anaesthesia with opioid anesthesia on postoperative shivering in morbidly obese patients scheduled for bariatric surgery