Cardiovascular Effects of Anesthetic induction with Midazolam for Open Heart Surgery

Lee, Kook Hyun; Kim, Kwang Woo

Abstract

Midazolam, an imidazobenzodiazepine derivative, is utilized as a premedicant, sedative and anesthetic induction agent. Cnmpared to diazepam, midazolam is characterized by better solubility in water, better venous tolerance and a more rapid onset of action. Though the onset of pharmacological action of midazolam takes longer than thiopental, midazolam exerts more gradual effects on circula- tion than thiopental. Because it maintains hemodynamic stability and induces amesthesia smoothly, madazolam is a potential alternative as an induction agent in high-risk patients. To evaluate the safe margin of i. v. midazolam and to investigate the effect of carbon dioxide retention by midazolam, 32 cardiac patients were divided into 4 groups: Group I, midazolam 0.2 mg/ kg with spontaneous respiration: Group II, midazolam 0.2 mg/kg with assist respiration: Group III, midazolam 0.4 mg/kg with assist respiration: Group IV, midazolam 0.4 mg/kg with spontaneons respiration. In each group, systolic blood pressure, diastolic blood pressure, heart rate, respiratory rate, cardiac output and arterial blood gas analysis were checked before and 2,4 and 6 minutes after i. v. injection of midazolam. Systolic blood pressure decreased significantly after injection of midazolam in all four groups. Diastolic blood pressure decreased significantly in group II and IlI. Systolic blood pressure was lower in group III than II 4 and 6 minutes following midazolam administration. The elevation of arterial carbon dioxide tension in group I and IV did not cause any changes in cardiovascular variables. The time from the end of injection of midazolam to spontanous closing of eyes and the time from the end of injection to disappearance of eyelash reflex were measured. But there were no significant differen-ces between all four groups. .On the basis of these data, we could conclude that in unpremedicated patients for open heart surgery midazolam alone allows rapid and smooth induction. In case of using the dose of 0.4 mg/kg, care must be taken in the decrease of systolic blood pressure.