Korean J Anesthesiol.  1995 Nov;29(5):583-593. 10.4097/kjae.1995.29.5.583.

The Effects of Thoracic Epidural Anesthesia on Myocardial and Systemic Circulation after Coronary Artery Occlusion in Dogs

• Chang SH
• Lim HJ
• Yoon HD
• Kim YH
• Kim YK

• KMID: 2299218
• DOI: http://doi.org/10.4097/kjae.1995.29.5.583

Abstract

Thoracic epidural combined with general anesthesia is used for thoracic and upper abdominal surgery and postoperative pain control. This technique has advantages of reducing the hemodynamic demand on the heart because of cardiac sympathetic block and stable intraoperative hemodynamics, but it may have a potential hazard of reducing coronary perfusion pressure due to hypotension. Decreased coronary perfusion pressure may be critical hazard to coronary insufficiency patients, but coronary vascular resistance may be decreased also due to blockade of sympathetic coronary constriction. This study was done to investigate the effect of thoracic epidural anesthesia on myocardial and systemic circulation during coronary occlusion limiting flow to 50% of preocclusive value. Comnary occlusion of left circumflex coronary artery was achieved with hydraulic vascular occluder with blood flow meter distal to occluder in 20 dogs. Five of them were dead during preparation. Coronary stenosis was maintained for 30 minutes, then epidural anesthesia was done with 0.5% bupivacaine (bupiva group) or saline (saline group) 5 ml through the surgically introduced epidural catheter. Arterial, mixed venous and coronary sinus blood was collected for the measurement of metabolites and myocardial and systemic oxygen comsumption and extraction ratio. Hemodynamic parameters and blood samples were obtained before(control), 30 minutes after stenosis(stenosis), 15, 30, 60, 90 and 120 minutes after epidural blockade. The results were as follows; The thoracic epidural block caused decrease in blood pressure, heart rate, cardiac index, level of free fatty acid and glucose, and increase in lactic acid level of mixed veous and coronary sinus blood, myocardial oxygen extraction ratio, arterio-venous oxygen content difference, and systemic oxygen extraction ratio. In conclusion the high thoracic epidural block may cause hypotension thus decrease oxygen supply to myocardium but the degree of which is less than that of total body, in the dogs with acute coronary stenosis. The reason is that the high thoracic epidural block decrease myocardial oxygen consumption, and make effective distribution of blood flow in ischemic myocardium, but the normal myocardium has the highest oxygen extraction in the body, so the high thoracic epidural block in coronary stenosis may cause ill effect on myocardial oxygen equlibrium.

Keyword

Thoracic epidural anesthesia(TEA); Coronary artery stenosis; Myocardial oxygen consumption; Myocardial oxygen extraction ratio; Hemodynamic parameters

MeSH Terms

Anesthesia, Epidural*
Anesthesia, General
Animals
Blood Pressure
Bupivacaine
Catheters
Constriction
Coronary Occlusion
Coronary Sinus
Coronary Stenosis
Coronary Vessels*
Dogs*
Glucose
Heart
Heart Rate
Hemodynamics
Humans
Hypotension
Lactic Acid
Myocardium
Oxygen
Oxygen Consumption
Pain, Postoperative
Perfusion
Vascular Resistance
Bupivacaine
Glucose
Lactic Acid
Oxygen