Perioperative changes in carbonylhemoglobin and methemoglobin during abdominal surgery: alteration in endogenous generation of carbon monoxide.

Abstract

Carbon monoxide (CO), which is homologous to nitric oxide (NO) as a monoxide, has been recently studied as a novel gaseous mediator for the maintenance of circulatory homeostasis and as a regulator of organ functions. Abdominal surgery is supposed to modulate the gaseous mediator by the reduction of heme oxygenase (HO) activity or transcriptional regulation of inducible HO. Therefore, we investigated perioperative changes in CO generation during abdominal surgery. A total of 397 patients who received abdominal surgery under intubation anesthesia were studied retrospectively by spectrophotometric analysis of carbonylhemoglobin (COHb) and methemoglobin (metHb) in arterial blood obtained at three points: before operation; several hours after return from operation room (0 POD); and next morning (1 POD). Thirty-three splenectomies, 36 hepatectomies and 42 drainages with control of infection focus for peritonitis were compared with 286 controls. The influences of smoking and blood transfusion were disregarded in the analysis, because smoking and blood transfusion were shown to increase exogenous and endogenous CO, respectively. In the non-smoker control group without blood transfusion, COHb did not change during the perioperative period, while metHb increased from the preoperative value of 0.52 +/- 0.03 to 0.72 +/- 0.02 at 0 POD and returned to 0.45 +/- 0.03 mg/dL at 1 POD. In the splenectomy group, COHb decreased from the preoperative value of 1.63 +/- 0.36 to 1.19 +/- 0.20 and 1.13 +/- 0.26 mg/dL at 0 and 1 POD, respectively, as a result of the removal of the organ with high HO activity. In the splenectomy group MetHb remained low: 0.47 +/- 0.09 mg/dL at 0 POD as compared with the control value. In the peritonitis and hepatectomy groups, COHb did not change during the perioperative period, while metHb increased to 0.64 +/- 0.06 and 0.73 +/- 0.10 mg/dL at 1 POD, respectively, as compared with the control value. In the hepatectomy group with or without blood transfusion, however, COHb and metHb were higher at 1 POD than the corresponding control value. Changes in COHb and metHb concentrations in arterial blood occur during abdominal surgery, although these amplitudes are small when compared with CO intoxication and methemoglobulinemia. It is likely that organ perfusion and functions are affected by these monoxide gas mediators during abdominal surgery.