Echocardiographic evaluation and comparison of the effects of isoflurane, sevoflurane and desflurane on left ventricular relaxation indices in patients with diastolic dysfunction.

This prospective randomized study aims to evaluate and compare the effects of isoflurane, sevoflurane and desflurane (study drugs) on left ventricular (LV) diastolic function in patients with impaired LV relaxation due to ischemic heart disease using transesophageal Doppler echocardiography. After approval of the local ethics committee and informed consent, 45 patients scheduled for coronary artery bypass grafting surgery were enrolled in the study. Patients were selected by a preoperative Transthoracic Echocardiographic diagnosis of impaired relaxation or Grade 1 Diastolic Dysfunction. They randomly received fentanyl and midazolam anesthesia with 1 MAC of isoflurane (n=16), sevoflurane (n=14) or desflurane (n=15). Hemodynamic parameters and TEE derived ventricular diastolic relaxation indices before and after the study drug administration were compared. LV filling pressures were kept constant throughout the study period to exclude the effect of the loading conditions on diastolic function. Four patients in the sevoflurane group and three in the desflurane group were excluded from the study, after baseline TEE examination revealed normal diastolic filling pattern. All the three study drugs significantly reduced the systemic vascular resistance index with a significant increase in cardiac index. Mean arterial pressure was reduced by all the drugs, although the decrease was not statistically significant. Hemodynamic changes were comparable between all the three groups. In terms of LV relaxation indices, all three agents led to a significant improvement in diastolic function. Transmitral and Tissue Doppler E/A and Em/Am ratios improved significantly Transmitral and Tissue Doppler E/A and Em/Am ratios improved significantly accompanied by a significant decrease in deceleration time and isovolumetric relaxation time. The effect of all three agents on diastolic relaxation parameters was comparable. In conclusion , Isoflurane, sevoflurane and desflurane, do not appear to have a detrimental effect in patients with early diastolic dysfunction. On the contrary, these inhalational agents actually improve the LV relaxation. A significant reduction in afterload produced by these vapors can be a possible reason for these findings. The positive effect of these inhalational agents on LV relaxation can have a profound effect on the perioperative anesthetic management of patients with diastolic dysfunction.

Influence of changes in the pulmonary artery pressure on ventilation requirements in patients undergoing mitral valve replacement.

The study was designed to evaluate the influence of changes in pulmonary artery pressure on the ventilation requirements in patients undergoing mitral valve surgery. Thirty patients with mitral valve disease with significant pulmonary arterial hypertension undergoing mitral valve replacement under cardiopulmonary bypass were included in this prospective study. All patients had a pulmonary artery catheter placed after the anaesthetic induction. The minute ventilation was adjusted to achieve an arterial carbon dioxide tension (PaCO2) of 35-40 mm Hg. After a stabilisation period of 15 minutes, the pulmonary artery pressure and the minute volume needed for maintaining a PaCO2 of 35-40 mm Hg in the precardiopulmonary bypass, post-cardiopulmonary bypass and six hours postoperatively were measured after ensuring stable haemodynamics and normothermia. There was a significant decrease in the mean pulmonary artery pressure from pre-cardiopulmonary bypass value of 41.3+/-15 mm Hg to 29.3+/-8 mm Hg in the postcardiopulmonary bypass period and subsequently to 25.5+/-7 mm Hg in the intensive care unit. There was a corresponding increase in the minute volume requirements from a pre-cardiopulmonary bypass value of 6.8+/-1 L/min to 8.0+/-1 L/min in the post cardiopulmonary bypass period and then to 9.4+/-1.2 L/min in the postoperative period. We conclude that there is a significant decrease in the pulmonary blood volume and a subsequent decrease in the pulmonary artery pressure after a successful mitral valve replacement in patients with pulmonary arterial hypertension. This is associated with a significant increase in the requirement of minute ventilation to maintain normocarbia.