Oxygen uptake and carbon dioxide elimination during controlled hypotension induced by prostaglandin e₁ or nitroglycerin

To compare the effects of prostaglandin E₁ (PGE₁) with those of nitroglycerin (NTG) on whole body metabolism (oxygen uptake (Vo₂) and carbon dioxide elimination (VCO₂)) during induced hypotension, we have studied 16 patients undergoing elective surgery (radical mastectomy or tympanoplasty). The patients were allocated randomly in a non-blinded manner to two groups. Baseline characteristics were similar in the two groups. Arterial pressure was controlled at about 70% of the baseline value using PGE₁ or NTG. VO₂, VCO₂, gas exchange ratio (RQ) and deadspace ventilation ratio (VD/VT) were measured continuously with mass spectrometry. The values for all variables were measured for 10 min at five times (1 = start of surgery (baseline value); 2 = start of drug infusion; 3 = 60 min after start of drug infusion; 4 = drug infusion stopped; 5 = surgery finished). VO₂, VCO₂, RQ and VD/VT values were relatively constant in both groups during surgery. The balance between oxygen supply and oxygen demand was maintained during induced hypotension with PGE₁ or NTG. (Br. J. Anaesth. 1994; 72: 439-442)