The Influence of Smoking on the Variations in Carboxyhemoglobin and Methemoglobin During Urologic Surgery.

INTRODUCTION: Surgery is supposed to modulate the production of carbon monoxide by the reduction of heme oxygenase activity or transcriptional regulation of inducible heme oxygenase. On the other hand, the inhalation of tobacco smoke can substantially raise the level of carboxyhemoglobin in the blood. Furthermore, methemoglobin is maintained at a constant level. However, excessive production of methemoglobin relative to total methemoglobin reductase activity results in methemoglobin increase. AIM: The aim of our study was to investigate the perioperative variations of carboxyhemoglobin and methemoglobin during urologic surgeries, and at the same time to evaluate the changes in methemoglobin as a possible indicator of nitric oxide generation. Our second aim was to evaluate the effect of preoxygenation on the level of carboxyhemoglobin and methemoglobin and the influence of blood transfusion on their changes. MATERIAL AND METHODS: The study included 30 patients scheduled for urologic surgery under general endotracheal anesthesia, aged 18-60 years without any history of respiratory disease, divided into two groups. The study group comprised patients who were smoking cigarettes or tobacco pipe, while the control group included non-smokers. In both groups carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels were determined preoperatively, after preoxygenation, and postoperatively. RESULTS: COHb levels were decreased postoperatively in both groups. The average values of COHb between the two groups were statistically significantly different (p=0.00). MetHb levels increased postoperatively in the group of smokers and decreased in the group of non-smokers. There were no statistically significant differences in the average postoperative MetHb levels between the two groups. CONCLUSION: Changes in carboxyhemoglobin and methemoglobin concentrations in arterial blood occur during urologic surgery, although these amplitudes are small when compared with carbon monoxide intoxication and methemoglobinemia. It is likely that organ perfusion and functions are affected by these monoxide gas mediators during urologic surgery.

The Role of Levosimendan in Patients with Decreased Left Ventricular Function Undergoing Cardiac Surgery.

The postoperative low cardiac output is one of the most important complications following cardiac surgery and is associated with increased morbidity and mortality. The condition requires inotropic support to achieve adequate hemodynamic status and tissue perfusion. While catecholamines are utilised as a standard therapy in cardiac surgery, their use is limited due to increased oxygen consumption. Levosimendan is calcium sensitising inodilatator expressing positive inotropic effect by binding with cardiac troponin C without increasing oxygen demand. Furthermore, the drug opens potassium ATP (KATP) channels in cardiac mitochondria and in the vascular muscle cells, showing cardioprotective and vasodilator properties, respectively. In the past decade, levosimendan demonstrated promising results in treating patients with reduced left ventricular function when administered in peri- or post- operative settings. In addition, pre-operative use of levosimendan in patients with severely reduced left ventricular ejection fraction may reduce the requirements for postoperative inotropic support, mechanical support, duration of intensive care unit stay as well as hospital stay and a decrease in post-operative mortality. However, larger studies are needed to clarify clinical advantages of levosimendan versus conventional inotropes.