Does anti-emetic dex actually cause post-op hyperglycaemia?

What one does is what counts, not what one had the intention of doing. – Pablo Picasso

Background:

Dexamethasone is frequently used as an anti-emetic for PONV prophylaxis. It has a similar efficacy to ondansetron. There are few data regarding post-operative hyperglycaemia in non-diabetic compared with diabetic patients following PONV prophylaxis with dexamethasone

Hypothesis:

The authors hypothesised that there would be a greater rise in post-operative blood glucose levels following use of dexamethasone compared to ondansetron for PONV prophylaxis.

Methods:

Ethical approval sought from LREC

The study include patients with Type 2 diabetes and patients without diabetes

  • inclusion criteria: English speaking, elective surgery lasting at least 1 hour, must be staying for at least 24 hours post op
  • Exclusion criteria: pregnant, pre-op BM > 11, on steroid treatment
  • Diabetic patients omitted oral hypoglycaemia agents on morning of surgery

 

  • Patients randomly allocated to receive 8mg IV Dexamethasone at induction or 4mg ondansetron at end of procedure
  • An anaesthetist not involved in the study prepared the drugs after opening a sealed envelope containing the randomised assignment
  • Randomisation was stratified by diabetic status and using computer generated software

 

85 patients were included in final analysis (134 recruited, 34 declined others consent withdrawn, screening failure loss to follow up). They were randomised to 4 groups:

  • T2DM patients receiving ondansetron 24
  • T2DM patients receiving dexamethasone 20
  • ND Patients receiving ondansetron 21
  • ND patients receiving dexamethasone 20

 

  • Standard intra operative anaesthetic technique and monitoring
  • Venous blood samples sent to lab pre-op baseline, 2h, 4h, 24h,
  • Diabetic patients had additional measurements (according to protocol) carried out via capillary glucometer.

Results

  • The maximum blood glucose measured post-op was higher in both the non-diabetic and diabetic patients receiving dexamethasone compared with those having ondansetron ( p=0.04 and p= <0.01 )
  • The maximum change in blood glucose levels from baseline to 4h and 24h was significantly greater in diabetic patients receiving dexamethasone compared to those only receiving ondansetron ( not different between dexamethasone and ondansetron groups in non-diabetic patients)
  • In the non-diabetic group, the mean (SD) max glucose was higher in those receiving dexamethasone compared with ondansetron – 9.1 ( 2.2) mmol/l vs 7.8 (1.4) mmol/l
  • In diabetic patients, the mean (SD) max blood glucose was also higher in those who received dexamethasone compared with compared with ondansetron 14.0 (2.5) mmol/l vs 10.7 (2.4) mmol/l
  • Diabetic patients receiving dexamethasone had higher insulin requirements in 24 Hr following surgery and were more likely to need insulin in recovery.

Conclusion 

  • There were increased post op blood glucose levels in both the non-diabetic and diabetic groups receiving dexamethasone compared to ondansetron
  • There was no correlation between dexamethasone administration and diabetic status, but being diabetic is s significant predictor of max change in blood glucose over 24h from baseline

Strengths 

  • prospective RCT
  • Good randomisation
  • Adequate power calculations, equal numbers over 4 groups
  • Attempts to blind
  • addressed the issue ( primary outcomes was post-op glucose levels at 2,4,24 hours)
  • All patients in the trial accounted for
  • Results can be applied to our population

Weaknesses 

  • Diabetics had more frequent measurements because a glucometer was used in these patients as well as the study’s lab blood tests. This was not avoidable, as this was the institution’s standard practices, but these glucometer measurements should perhaps not have been included in the final analysis .
  • This also meant that he peak blood glucose could have been missed in non-diabetic groups because the had their blood sugar measured less frequently
  • Use of hetastarch. Hetastarch is known to increase post-operative blood sugar levels and varying amounts were used in the diabetic patients. Could this have contributed to rise in blood sugar?

 

Take home message: use of dexamethasone increases blood sugar post operatively in diabetic and non-diabetic patients compared to ondansetron – so use cautiously in patients with diabetics.

Summary by Dr Jai Patel

 

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