The effect of hypernatraemia on ketamine anaesthesia in male rats

We studied the effects of a single ketamine injection in an experimental model of chronic hypernatraemiain rats. Three groups, each of 20 male Wistar rats were chosen for the experiment; the control group wasgiven water and the test groups were given 1% (group 1) and 2% (group 2) NaCl solutions for two weeks. Allgroups were fed with the same diet, containing about 0.5% salt. Other living conditions for all groups weresimilar. Before using saline in the test groups and before induction of anaesthesia, blood samples were drawnto measure the serum sodium level. A single ketamine injection (125 mg/kg, IP) was used in all groups.Latency times to inhibit the righting reflex and to inhibit the response to painful stimulus, re-appearance timeof response to painful stimulus and recovery time from anaesthesia were measured; mortality rates duringanaesthesia were also recorded. During consumption of salt solutions and before induction of anaesthesia, wehad no animal death. The serum sodium level in group 2 was significantly higher than group 1 and thecontrol group. The required time to inhibit the righting reflex and the response to painful stimulus in group 2was significantly shorter than group 1 and the control group. These parameters in group 1 were alsosignificantly shorter than the control group. The required time for re-appearance of response to painfulstimulus and for recovery from anaesthesia in group 2 was significantly longer than group 1 and the controlgroup. We observed severe pulmonary complications in the test groups during anaesthesia. Mortality rate ingroup 2 was 60% and in group 1 was 20%; the control group had no significant problems during anaesthesia.Hypernatraemia decreased the induction time of anaesthesia. The duration of ketamine anaesthesia increasedand the recovery from anaesthesia was associated with significant delay.