Comparison of crystalloid preloading versus crystalloid coloading to prevent hypotension and bradycardia following spinal anaesthesia

Background: We compared the effect of preloading against coloading with 15 mlkg^-1 of Lactated Ringer solution in preventing hypotension and bradycardia following subarachnoid block. Patients & Methods: Fifty four adult ASA physical status 1 and 2 patients scheduled for elective knee and ankle arthroscopies were randomized into 2 groups after informed consent. Group P received Ringer's lactate 20 minutes before spinal anaesthesia. Group C received equal volume over 20 minutes after spinal block. Baseline heart rate, systolic, diastolic and mean arterial pressures were recorded. The same parameters were then recorded at 2, 4, 6, 8, 10 minutes after spinal anaesthesia and thereafter every 5 minutes for 45 minutes. Decrease in heart rate >20%, mean arterial pressure >30% from baseline was considered significant clinically and number of such episodes recorded. Dosage of mephentermine and atropine used to treat hypotension and bradycardia was recorded in both the groups. Incidence of giddiness and nausea were recorded. Quantitative data were compared with Student's t test and qualitative data with Chi square or Fisher exact test. P<0.05 was considered significant. Results: Patient characteristics, baseline heart rate and arterial pressures were comparable between the two groups. The number of episodes of clinically significant decrease in heart rate and mean arterial pressure were 13 and 5 respectively in group P; 13 and 3 respectively in group C. This was comparable. The dosage of mephentermine and atropine used in both the groups were comparable. There was no significant difference in heart rate and arterial pressures between the groups at all the time intervals. Incidence of nausea and giddiness were comparable. Conclusions: We found that coloading with 15 mlkg^-1 of Ringer's lactate was as effective as preloading to prevent spinal induced hypotension and bradycardia.