Olaf W. Levang

Thoracic epidural analgesia in aortocoronary bypass surgery. II: Effects on the endocrine metabolic response.

Thoracic epidural analgesia (TEA) may offer haemodynamic benefits for patients with coronary heart disease going through major surgery. This may – in part – be secondary to an effect on the endocrine and metabolic response to surgery. We therefore investigated the effect of TEA on the endocrine metabolic response to aortocoronary bypass surgery (ACBS).

Thoracic epidural analgesia in aortocoronary bypass surgery. I: Haemodynamic effects

Tachycardia and hypertension may cause myocardial ischaemia in patients with coronary heart disease going through major surgery. Thoracic epidural analgesia (TEA) has been reported to be beneficial in this situation.

Exercise hemodynamics in small (≤21 mm) aortic valve prostheses assessed by Doppler echocardiography☆

Exercise Doppler echocardiography was used to assess hemodynamics in 25 patients with a < or = 21 mm aortic valve prosthesis (14 with a Medtronic-Hall 21 mm valve, three with a Medtronic-Hall 20 mm valve, three with a Sorin 21 mm valve, one with a Duromedics 21 mm valve, and four with a Carpentier-Edwards 21 mm valve). A symptom-limited upright bicycle exercise test was performed, and Doppler gradients were recorded during exercise. Gradients increased with exercise from 30 +/- 8/16 +/- 4 mm Hg (peak/mean) at rest to 46 +/- 12/24 +/- 7 mm Hg during exercise; both p < 0.001. Mean exercise gradient exceeded 30 mm Hg in five patients, and the highest mean gradient recorded was 37 mm Hg. Within the group of mechanical valves, gradients at exercise were similar for different types of valves. A linear relationship was found between gradients at rest and during exercise (peak r = 0.75, mean r = 0.77; both p < 0.001). Additional findings were midventricular velocities exceeding 1.5 m/sec in late systole in 10 patients (40%) and intraventricular flow (> or = 0.2 m/sec) toward the apex during isovolumic relaxation in 11 patients (44%). The patients with these velocity patterns had significantly smaller left ventricular cavities (end-diastolic diameter 39.8 +/- 4.8 vs 46.5 +/- 4.2 mm, p < 0.01; end-systolic diameter 24.2 +/- 3.0 vs 28.5 +/- 4.5 mm, p = 0.013).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of thoracic epidural analgesia on coronary hemodynamics and myocardial metabolism in coronary artery bypass surgery

OBJECTIVE A possible influence of thoracic epidural analgesia on coronary hemodynamics and myocardial metabolism in coronary artery bypass grafting was investigated. DESIGN The study was prospective and randomized. SETTING The study was performed in a university hospital. PARTICIPANTS Thirty male patients less than 65 years of age and with ejection fraction greater than 0.5 participated. They were randomized into 3 groups: the high fentanyl (HF) group receiving high-dose fentanyl (55 micrograms/kg) anesthesia, the HF + thoracic epidural analgesia (TEA) group receiving the same general anesthesia plus thoracic epidural analgesia, and the low-fentanyl (LF) + TEA group receiving low-dose fentanyl (15 micrograms/kg) anesthesia plus thoracic epidural analgesia. INTERVENTIONS A thoracic epidural catheter, a peripheral and central venous catheter, a radial artery catheter, a thermodilution pulmonary artery catheter, and a coronary sinus reverse thermodilution catheter were inserted. MEASUREMENTS AND MAIN RESULTS Coronary circulatory parameters, myocardial oxygenation, and myocardial substrate utilization were investigated before bypass and for 9 hours after bypass. Before bypass, the most striking finding was a reduction in myocardial lactate extraction in all groups, but also coronary flow and myocardial oxygen consumption decreased compared with baseline. After bypass, the only significant finding was a lower coronary vascular resistance early postoperatively in the epidural groups, but coronary blood flow was adequate in all groups. Myocardial metabolism was essentially unchanged both with and without epidural analgesia after bypass. CONCLUSION With regard to the coronary circulation and myocardial metabolism, no hard data supporting the use of thoracic epidural analgesia in coronary artery bypass grafting were found.

Hemodynamic evaluation by Doppler echocardiography of small (≤21 mm) prostheses and bioprostheses in the aortic valve position

Abstract To assess resting hemodynamics of an unselected group of patients with prostheses or bioprostheses sized ≤21 mm implanted into the aortic valve position during a 7-year period, 46 of 50 eligible patients were examined by Doppler echocardtography. The valves were Carpentier-Edwards (CE) supraannular 21 mm (n = 8), Medtronic-Hall (MH) 20 mm (n = 8) and 21 mm (n = 21), and the rest (n = 9) were other valves with only 1 to 3 patients in each group. Gradients, valve areas and dimensionless obstruction indexes (ratio of subvalvular/valvular velocities and velocity time integrals) were compared. By analysis of variance, gradients did not differ significantly between the CE supraannular 21 mm, the MH 20 and 21 mm prostheses (peak/mean 25 ± 8/14 ± 5, 31 ± 13/16 ± 6 and 25 ± 10/13 ± 5 mm Hg; p = not significant). Only 2 patients had a mean gradient >25 mm Hg. The valve area was slightly larger for the MH 21 mm group compared with the CE supraannular 21 mm group (1.34 ± 0.15 vs 1.16 ± 0.14 cm 2 , p

The influence of thoracic epidural analgesia alone and in combination with general anesthesia on cardiovascular function and myocardial metabolism in patients receiving β-adrenergic blockers

Thoracic epidural analgesia combined with chronic beta-adrenergic blocker medication may cause cardiac depression. We investigated the cardiovascular and myocardial metabolic effects of a T1-T12 epidural block in 18 patients (age < 65 yr, ejection fraction > 0.5), receiving chronic beta-adrenergic blocker medication and scheduled for aortocoronary bypass surgery. After randomization into a light or deeper general anesthetic group, the cardiovascular and myocardial metabolic effects of a subsequent general anesthesia induction were investigated. Thoracic epidural analgesia induced a moderate decrease in mean arterial pressure, coronary perfusion pressure, free fatty acids, and myocardial consumption of free fatty acids. General anesthesia with thiopental (2-4 mg/kg) and a low fentanyl dose (5 micrograms/kg) increased heart rate, coronary perfusion pressure, and coronary vascular resistance, whereas mean pulmonary arterial pressure and pulmonary capillary wedge pressure decreased. After thiopental (2-4 mg/kg) and a high fentanyl dose (30 micrograms/kg), mean arterial pressure and left ventricular stroke work index decreased. We conclude that a T1-T12 epidural block in well sedated, beta-adrenergic blocked patients does not induce clinically significant cardiovascular effects. Induction of general anesthesia was well tolerated, but the light general anesthetic could not prevent an increase in heart rate and coronary vascular resistance, whereas the deeper anesthetic induced slight myocardial depression. No effect on the atrioventricular conduction, as measured by the PQ-time, was noted.

Heparin–coated circuit during cardiopulmonary bypass

A prospective randomized study was performed to investigate the effect of surface coating with covalently endpoint–attached heparin (Carmeda Bio Active Surface) and reduced general heparinization on haematological indices and complement C5 activation. Care was taken to optimize the rheological design of the system using centrifugal pump and a closed system without venting or machine suction. Twenty patients scheduled for aortocoronary bypass grafting (EF > 0.5) participated in the study. Ten patients were randomized to be treated with heparin–coated equipment (CBAS) and reduced i.v. heparin (1.5 mg kg‐1) while 10 patients treated with identical but noncoated equipment and full heparinization (3 mg–kg‐1) served in a Control group. A vacuum suction was used to collect the blood from the operating field and it was autotransfused at weaning from extracorporeal circulation (ECC). Blood samples were obtained from the venous (precircuit) and arterial (postcircuit) side. We used a new and very specific method for detection of C5a based on monoclonal antibodies. The concentration of C5a was low in both groups during the operation but a significant increase was seen on days 1 and 2. In the Control group there was an increase from 10.2 ngml‐1±1.2 to 27.5 ng ml‐1 ± 4.8 on day 2 and in the CBAS group from 10.7 ng ml‐1 ± 1.2 to 35.6 ng ml‐1 ± 11.6 on day 2 (NS between groups). The granulocytes and total leukocyte count increased at the end of ECC and was maintained at the elevated level throughout the study period. The amount of free haemoglobin was high in the autotransfused blood in both groups. The present results confirm the feasibility of reducing general heparin when using heparin–coated systems but the study does not support the superiority of such coating with regard to biocompatibility in short procedures with a Theologically optimized circuit. The potential benefit from reduced heparin and protamine has not been fully evaluated.

Factors Influencing Return to Work after Aortocoronary Bypass Surgery

Factors influencing the effect on employment status were investigated in 250 patients (males: females 224:26) who underwent coronary artery bypass surgery between March 1983 and November 1985. The median age at operation was 57.9 (range 36.6-69.4) years and the median follow-up time 32 (19-52) months. Preoperatively 149 patients (59.6%) were receiving sick pay or disability pension because of their heart disease. Only 64 (25.6%) were gainfully employed, in contrast to 97 (38.8%) at follow-up. Of those who were working at the time of operation, all but eight returned to work postoperatively. At follow-up 183 (80.3%) were free from symptoms or much improved, with degree of improvement somewhat greater in those who were working postoperatively. The period of sick leave and the preoperative waiting time were significantly shorter for patients who were working postoperatively than for those who were awarded disability pension. Age, previous myocardial infarction, duration of preoperative angina and type of work were also found to influence postoperative employment status.

Time-related changes in the starling forces following extracorporeal circulation

SummaryThe intra- and postoperative variations of the transcapillary forces [colloid osmotic pressure of plasma (COPpl), colloid osmotic pressure of interstitial fluid (COPif), average hydrostatic pressure in the interstitium (Pif)] were studied in the subcutaneous tissue as a function of time in 13 patients operated on for coronary artery disease using extracorporeal circulation (ECC). The measurements were performed before operation, during ECC, and during the first 24 hours postoperatively. COPif was measured subcutaneously on the chest both by the wick method and by a noninvasive blister suction method. The latter technique allowed several consecutive measurements in the same individual during the postoperative period. Pif was measured by “wick-in-needle” technique in the same area as the COPif measurements. COPpl was measured in a blood sample collected from a cubital vein. COPpl was reduced about 50% during ECC returned to pre-ECC level within the first 6 hours postoperatively. During ECC COPif was higher than COPpl, reaching its minimum level 4 to 5 hours postoperatively. Measurements performed following ECC showed return of the transcapillary COP-gradient to the normal direction (COPpl > COPif). Pre-ECC level of COPif was not entirely obtained during the first postoperative day. Pif increased gradually during ECC and continued to increase the first 2 to 3 hours following ECC. Pre-ECC level was reached within 24 hours postoperatively. The present investigation has demonstrated major dynamic variations in the transcapillary forces in patients undergoing open heart surgery with ECC. There was an increased net capillary filtration (F) intraoperatively predisposing to interstitial edema formation in subcutaneous tissue until several hours following the termination of ECC.

Aortic Valve Replacement. A Randomized Study Comparing the Björk–Shiley and Lillehei–Kaster Disc Valves. Late Haemodynamics Related to Clinical Results

In this study, 78 randomized patients with either Björk-Shiley (B-S) or Lillehei-Kaster (L-K) aortic disc valve prostheses were re-admitted for clinical and haemodynamic evaluation. The patients were selected that those with narrow aortic roots were over-represented. Cine-aortography was carried out in 75 patients and left ventricular catheterisation via the transseptal approach was performed in 42. The clinical improvement was striking, although the number of patients still incapacitated was relatively large in patients with the small L-K valves (Nos. 14 & 16). Peak-to-peak and mean systolic pressure differences across the valves were significantly lower in the B-S than in the L-K valves, particularly when the small valve sizes were compared. Left ventricular end-diastolic pressure (LVEDP), which was elevated in most patients before operation, decreased significantly to normal levels in the B-S group. In the L-K group, LVEDP did not decrease significantly and was on the average still above the normal level after operation, probably due to the relatively large pressure gradients. The study indicates that the L-K valves Nos. 14 & 16 in particular represents a resistance to flow that is too large to be acceptable in clinical practice.