Repeated intracerebral microinjections: efficacy in studying brain functions.

Injection of chemicals into the brain has been considered as an important technique to study various functions of the brain. In these studies, as a rule, only one bilateral injection is given in one animal. This study was undertaken to evaluate the quality of the body temperature data obtained after first and second injections of methoxamine and artificial cerebrospinal fluid into the medial preoptic area. Though there was quantitative decrease in the effects produced after the second injection of the drug, there was no significant change in the effects produced by the second injections of artificial cerebrospinal fluid, which was used as a vehicle. Results of this study support the earlier recommendation to perform only one injection in any of the brain sites for evaluating the effect of any drug. But the vehicle can be administered as a second injection, without compromising on the quality of data.

Prevention of spinal anaesthesia-induced hypotension in elderly: methoxamine or ephedrine

Two vasopressors were compared to reduce incidence of hypotension during spinal anaesthesia in elderly patients, methoxamine 10mg i.m. or ephedrine 10mg i.v. plus 20mg I.m, in terms of haemodynamic stability and requirement for additional vasopressors. Forty patients [aged 60-75yr] undergoing surgery of the lower body were allocated randomly into group M [n=20] and group E [n=20] the vasopressors were injected 10 min before induction of spinal anaesthesia. Rescue ephedrine 3-6 mg was given if systolic blood pressure [SAP] or mean arterial blood pressure [MAP] reduced more than 25% of the base line value. Patient and spinal characteristics were similar in the two groups. SAP and MAP increased initially form baseline until induction of spinal anaesthesia and then decreased for 25 min in both groups [not significant between groups]. Heart rate [HR] decreased from the baseline in group M [p<0.05] and was lower than in group E at all time form 4-70 min [p<0.01]. The incidence of hypotension of SAP and MAP was not significant between groups [SAP 25% vs 30% and MAP 20% vs 25%]. Requirements for rescue ephedrine [20% vs 25%] dose of rescue ephedrine given [4.8 vs 5.1mg] and time to onset of hypotension [9.8 vs 11.6 min] were similar in groups M and E. respectively. We conclude that methoxamine 10mg i.m. given 10 min before induction of spinal anaesthesia in normovolaemic elderly insignificantly reduce Incidence of subsequent SAP and MAP hypotension. requirements for rescue vasopressor therapy but has significant reduction of HR compared with ephedrine 10 mg i.v. plus 20mg i.m