Hypotension is frequently encountered during the use of these commonly used intravenous anaesthetic agents (thiopental and propofol). This is thought to be a consequence of their effects on the sympathetic nervous system, myocardial contractility or vascular tone. However, propofol causes a greater fall in systemic arterial blood pressure than any other drug used for induction of anaesthesia. Propofol causes profound vasodilation, whereas its myocardial depressant effect is not clear. The vasodilatation occurs in both arterial and venous systems. The decrease in systemic arterial blood pressure after thiopental induction is mainly due to peripheral vasodilatation caused by depression of the medullary vasomotor centre and inhibition of the sympathetic nervous system. However, how this peripheral vasodilator effect occurs after both drugs and which mediators accompany it have not yet been fully elucidated. In previous studies, it has been emphasised that systemic vasodilation may be related with increased formation of nitric oxide (NO), a small gaseous and lipophilic molecule which plays an important role in the regulation of vascular homeostasis and haemoregulation. It is important to elucidate the mechanisms that may mediate thiopental- and propofol-mediated vasodilatation in future studies in order to help the methods and treatments that can be developed to prevent hypotension caused by these drugs, which are widely used in clinical practice. Therefore, the aim of this study was to investigate the effects of thiopental and profol on erythrocyte NO synthase activity and erythrocyte-mediated NO release.

Male patients aged 18-45 years with ASA (American Society of Anaesthesiologists) class I (normal, healthy person without any disease or systemic problem other than surgical pathology that does not cause a systemic disorder) who applied to the anaesthesiology and reanimation clinic outpatient clinic for preoperative preparation were planned to be included in the study. Women, patients with ASA class >1, patients with known thiopental/propofol allergy and patients outside the age range of 18-45 years were excluded from the study. Venous blood samples will be taken from the patients included in the study and incubated with thiopental and propofol (dose: 100, 250, 500 and 1000µM) after appropriate procedures in the laboratory environment. . After incubation, all resuspensions will be subjected to flow cytometric analysis to evaluate erythrocyte NO synthase activity and erythrocyte-mediated NO release.All patients included in the study will be informed and their written and verbal consent will be obtained.

Inclusion Criteria:

• Male patients
• Aged 18-45 years
• ASA (American Society of Anaesthesiologists) class I (normal, healthy person without any disease or systemic problem other than surgical pathology that does not cause a systemic disorder)

Exclusion Criteria:

• Women patients
• ASA class >1
• Patients with known thiopental/propofol allergy
• Patients outside the age range of 18-45 years