Effect of Intravenous Ketamine Administration on Blood Glucose Levels in Conscious Rabbits

Problem statement: The intravenous general anaesthetic ketamine has been shown to produce changes in blood glucose levels. It is important to study the pharmacological basis of such an effect. Approach: The influence of varying doses of ketamine administered intravenously was studied in conscious rabbits. Serum glucose was determined by blood glucose method using an enzymatic PAP250 kit. Results: Low doses of ketamine (166.6 mg kg^-1) produced hyperglycaemia while higher doses (1 and 2 mg kg^-1) produced hypoglycaemia. However, at even a higher dose, ketamine (4 mg kg^-1) did not influence blood glucose levels. The dual effect of ketamine was resistant to α₁-adrenoceptor blockade by WB-4101. On the other hand, the opioid antagonist naloxone blocked the hypoglycaemic and potentiated the hyperglycaemic effects of ketamine. Blockade of α₂-adrenoceptors by yohimbine, abolished hyperglycaemia by ketamine and reversed its hypoglycaemic effect into hyperglycaemia that was sensitive to blockade by propranolol. Conclusion: Ketamine had a dual effect on blood glucose level. Its hyperglycaemic effect seemed to be mediated through α₂-adrenoceptors while the hypoglycaemic effect is possibly mediated through opioid receptors with an involvement of β-adrenoceptors that only become evident after blockade of α₂-adrenoceptors. Similar mechanisms may operate during ketamine anaesthesia. Plans were under preparations for future investigations on blood glucose levels of patients undergoing dental surgical procedures under ketamine anaesthesia, the results of which may prove clinically important.