Consumption of dopamine hydrochloride by nitroglycerine: Preliminary clinical and experimental observations

Background Hypotension in twenty seven patients following coronary artery bypass graft (CABG) surgery did not respond to increasing doses of dopamine hydrochloride. This was observed when Dopamine was delivered in the same lumen of the central venous catheter alongwith nitroglycerine (NTG). When infused through separate ports of the central venous line dopamine was observed to achieve the optimum blood pressure response in smaller doses while keeping the same concentration and dose of nitroglycerine on flow. Rationale behind this observation was investigated. Methods Twenty seven patients who underwent CABG received Dopamine & Nitroglycerine infusion in the immediate postoperative period formed the clinical study group. Laboratory experiments were done to determine nitric oxide generation under various conditions spectrophotometrically. Nitrous acid was also detected by color reactions. Results (a) Clinical: Dopamine was more effective when it was delivered in a separate line from NTG. (b) Experimental: Experiments revealed that the cause of persistent hypotension when Dopamine hydrochloride and NTG were mixed was due to the consumption of Dopamine by NTG.