A study to determine the optimum dose of metaraminol required to increase blood pressure by 25% during subarachnoid anaesthesia

We studied dosage optimization for metaraminol when managing hypotension during subarachnoid anaesthesia, Twenty patients aged 53 to 84 years, were recruited. Non-invasive blood pressure (BP) and heart rate were recorded one-minutely, A series of four IV metaraminol boluses (0.25 to 1.0 mg per 50 kg adult) were administer-ed. From individual patient time plots of BI: predicted dosages for a 25% elevation in BP were estimated. Dose-related elevations in systolic BP [mean (SD)] occurred following dosages of 0.5 mg [25 (11)%] and 1.0 mg [50 (23)%], Similar elevations occurred in mean and diastolic BP. Overall estimated dosage (median) to produce a 25% elevation in systolic BP was 0.5 mg (per 50 kg adult), However; individual patient responses varied (10-90th centiles=0.23 to 0.80 mg), Thus, we now recommend a starting dose of 0.25 mg, increasing to 0.5 mg if necessary, to treat hypotension (25% decrease in systolic BP) during subarachnoid anaesthesia.