Roderick W. Landymore

A comparison of the myocardial metabolic and haemodynamic changes produced by propofol-sufentanil and enflurane-sufentanil anaesthesia for patients having coronary artery bypass graft surgery

The purpose of this study was to compare propofol-sufentanil with enflurane-sufentanil anaesthesia for patients undergoing elective coronary artery bypass graft (CABG) surgery with respect to changes in (1) haemodynamic variables; (2) myocardial blood flow and metabolism; (3) serum cortisol, triglyceride, lipoprotein concentrations and liver function; and (4) recovery characteristics. Forty-seven patients with preserved ventricular function (ejection fraction > 40%, left ventricular enddiastolic pressure ≤ 16 mmHg) were studied. Patients in Group A (n = 24) received sufentanil 0.2 μg · kg− 1 and propofol 1– 2 mg · kg− 1 for induction of anaesthesia which was maintained with a variable rate propofol (50–200 μg · kg− 1 · min− 1) infusion and supplemental sufentanil (maximum total 5 μg · kg− 1). Patients in Group B (n = 23) received sufentanil 5 μg · kg− 1 for induction of anaesthesia which was maintained with enflurane and supplemental sufentanil (maximum total 7 μg · kg− 1). Haemodynamic and myocardial metabolic profiles were determined at the awake-sedated, post-induction, post-intubation, first skin incision, post-sternotomy, and pre-cardiopulmonary bypass intervals. Induction of anaesthesia produced a larger reduction in systolic blood pressure in Group A (156 ± 22 to 104 ± 20 mmHg vs 152 ± 26 to 124 ± 24 mmHg; P < 0.05). No statistical differences were detected at any other time or in any other variable including myocardial lactate production (n = 13 events in each group), time to tracheal extubation and time to discharge from the ICU. We concluded that, apart from hypotension on induction of anaesthesia, propofol-sufentanil anaesthesia produced anaesthetic conditions equivalent to enflurane-sufentanil anaesthesia for CABG surgery.RésuméAfin de comparer l’anesthésie au propofol-sufentanil avec celle à l’enflurane-sufentanil pour pontage aorto-coronarien électif concernant les variations dans 1) les données hémodynamiques; 2) le flot sanguin myocardique et métabolisme; 3) la concentration serique du cortisol, les triglycérides, les lipoprotéines et la fonction hépatique, 4) les caractéristiques de réveil. Quarantesept patients avec une fonction ventriculaire préservée (fraction d’éjection > 40%, pression diastolique de ventricule gauche à 16 mmHg) ont été étudiés. Les patients du groupe A (n = 24) ont reçu du sufentanil 0,2 μg · kg− 1 et du propofol 1– 2 mg · kg− 1 pour l’induction de l’anesthésie qui fut maintenue avec des taux variables de perfusion de propofol (50–200 μg · kg− 1 · min− 1) et un supplément de sufentanil (maximum total 5 μg · kg− 1). Les patients du groupe B (n = 23) ont reçu du sufentanil 5 μg · kg− 1 pour l’induction de l’anesthésie qui fut maintenu avec l’enflurane et des doses supplémentaires de sufentanil (dose totale maximale 7 μg · kg− 1). Les profils myocardique et hémodynamique ont été déterminé alors que le patient était réveillé sédationné, après l’induction, à l’incision cutanée, après sternotomie, et avant la CEC. L’induction de l’anesthésie a produit une plus grande diminution de la pression artérielle systolique dans le groupe A (156 ± 22 à 104 ± 20 mmHg vs 152 ± 26 à 124 ± 24 mmHg; P < 0,05). Aucune différence statistique significative ne fut détectée en aucun temps ni en aucune des autres variables incluant la production de lactate par le myocarde (n = 13 evénéments dans chaque groupe), el le temps de l’extubation jusqu’ au congé des soins intensifs. On conclut qu’à part l’hypotension lors de l’induction de l’anesthésie, le propofol-sufentanil était similaire à l’enfluranesufentanil pour la chirurgie de pontage aorto-coronarien électif.

Does Pulsatile Flow Influence the Incidence of Postoperative Hypertension

Twenty patients undergoing primary elective aorta--coronary artery bypass were divided into two equal groups, both receiving identical premedication, anesthetic, and pump primes. The control patients received hypothermic nonpulsatile flow and the study patients received hypothermic pulsatile flow. Hypertension, defined as a pressure of 160/100 mm Hg or higher, was observed in 80% of the control patients and 20% of the patients receiving pulsatile flow (p less than 0.05). Serial renin measurements demonstrated maximum values in the intensive care unit and coincided with the onset of postoperative hypertension in the control patients. Those patients who had received pulsatile flow did not demonstrate notable renin stimulation. Catecholamines were markedly elevated during bypass and in the intensive care unit, but there was no significant difference between the two groups. Peripheral vascular resistance was not significantly lower with pulsatile flow, except in the first study performed in the intensive care unit. We conclude that catecholamines and the renin-angiotensin system contribute to the production of postoperative hypertension and that pulsatile flow diminishes renin stimulation. Pulsatile flow results in a decreased incidence of postoperative hypertension.

Comparison of Cod-Liver Oil and Aspirin-Dipyridamole for the Prevention of Intimal Hyperplasia in Autologous Vein Grafts

The combination of aspirin and dipyridamole is currently used to prevent intimal hyperplasia and to improve long-term vein graft patency following myocardial revascularization. Preliminary studies indicate that cod-liver oil, rich in eicosapentaenoic acid, an unsaturated fatty acid, may also be effective in the prevention of intimal hyperplasia. Twenty-four mongrel dogs were used to compare the effectiveness of aspirin-dipyridamole and cod-liver oil on vein graft intimal hyperplasia following arterial bypass. Forty-eight segments of undistended autologous external jugular vein were interposed between bilaterally divided femoral arteries. All animals received a 2% cholesterol diet for 1 week before and 6 weeks after operation. Eight controls received the diet alone. Eight other animals received dipyridamole (2.5 mg per kilogram of body weight) two days before operation and dipyridamole (2.5 mg/kg) and aspirin (30 mg/kg) daily for 6 weeks after operation. Another 8 animals received cod-liver oil containing 1.8 gm of eicosapentaenoic acid daily 1 week before and for 6 weeks following operation. Serum cholesterol increased similarly in all groups; it rose from 4.5 +/- 0.2 mm/L to 8.3 +/- 0.8 mm/L in the controls, to 7.2 +/- 0.5 mm/L in the aspirin-dipyridamole group, and to 7.1 +/- 0.5 mm/L in the cod-liver oil group (p less than 0.01). Prothrombin time, partial thromoboplastin time, total platelet counts, and bleeding times were unchanged. Intimal hyperplasia was measured at 6 weeks with a Zeiss computerized microscope; 376 +/- 25 measurements were made from each graft. The intima increased from 4.5 +/- 0.2 to 83 +/- 10 micron in the control dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Preconditioning prevents myocardial stunning after cardiac transplantation

BACKGROUND Preconditioning has been shown to reduce myocardial stunning after reversible global ischemia. To determine whether preconditioning improves functional recovery after cardiac transplantation, 16 sheep were randomly assigned to a preconditioning protocol or to a control group. METHODS Preconditioning was achieved with 5 minutes of global ischemia followed by 10 minutes of reperfusion. The heart was then arrested with 1 L of crystalloid cardioplegia, explanted, stored in a transport cooler, and then transplanted into recipient sheep. The total ischemia time was 2 hours. Pressure-volume loops were used to calculate preload recruitable stroke work, the maximum elastance, and diastolic compliance. Linear regression analysis was used to determine the preload recruitable stroke work, maximum elastance, and diastolic compliance-and end-diastolic volume relationship. The area under the regression curve for preload recruitable stroke work was defined as the preload recruitable stroke work area. Biopsies were taken for high-energy phosphates. RESULTS Systolic function, represented by preload recruitable stroke work area, was preserved after cardiac transplantation in preconditioned animals. Maximum elastance and diastolic compliance were unaffected by preconditioning or ischemia. High-energy phosphates were better preserved in preconditioned animals. CONCLUSION Preconditioning prevented myocardial stunning and preserved high-energy phosphates after experimental cardiac transplantation.

Anatomical Studies to Support the Expanded Use of the Internal Mammary Artery Graft for Myocardial Revascularization

The internal mammary artery pedicle graft is frequently used for coronary bypass. Five internal mammary artery pedicle grafts, harvested but not utilized for coronary bypass, underwent histological examination. The histological studies demonstrated that the vasa vasorum were confined to the adventitia and did not penetrate the media of the internal mammary artery. These observations indicate that the media is nourished entirely from the lumen and suggest that harvesting the internal mammary artery as a free graft would not subject the wall of the artery to ischemic injury. Subsequent to these studies, we used the right internal mammary artery as a free graft to revascularize the distal circumflex coronary artery in 12 patients. The free graft was anastomosed to marginal branches of the circumflex and was then brought up to the left internal mammary artery pedicle graft and anastomosed end-to-side. This procedure has not resulted in excessive postoperative bleeding or sternal infections, and has relieved the anginal syndrome in all 12 patients.

Effect of intermittent delivery of warm blood cardioplegia on myocardial recovery

Continuous warm blood cardioplegia is often temporarily interrupted during coronary artery operations to provide the surgeon with a bloodless operating field. To determine the effects of intermittent warm ischemia on myocardial recovery, we randomized 15 adult mongrel dogs to receive either multidose cold or warm blood cardioplegia during a 90-minute arrest. Myocardial metabolic and functional recovery was assessed before clamping of the aorta and after 30 and 60 minutes of reperfusion. Systolic function was well preserved, whereas diastolic function decreased slightly in both groups after arrest. Myocardial oxygen consumption increased during reperfusion after cold heart protection but was unchanged after warm blood cardioplegia. High-energy phosphates decreased significantly in both groups during reperfusion. Two conclusions were reached. (1) Myocardial functional recovery was well preserved, whereas metabolic recovery was impaired after either technique of myocardial preservation. (2) Preserved functional recovery after multidose warm blood cardioplegia suggests that repetitive episodes of ischemia may condition the myocardium, thus preventing injury during prolonged aortic cross-clamping.

Effects of Oral Amiodarone on Left Ventricular Function in Dogs: Clinical Implications for Patients with Life-Threatening Ventricular Tachycardia

Twenty-four mongrel dogs were divided into two equal groups to determine the effects of orally administered amiodarone on left ventricular function. Measurements of left ventricular function included left ventricular contractility as denoted by maximum rate of rise of left ventricular pressure (dP/dtmax), cardiac index (CI), left ventricular stroke work index (LVSWI), and peripheral vascular resistance (PVR). Left ventricular function was measured in 6 of the 12 animals in Group 1 before and after 14 days of amiodarone administered orally; the remaining animals served as controls. The dP/dtmax was reduced from 2,855 to 1,291 mm Hg/sec (p less than 0.01), and LVSWI fell from 1.6 to 0.74 gm-m/beat/kg (p less than 0.05) in the 6 animals given amiodarone. The 12 animals in Group 2 underwent 30 minutes of ischemic arrest. Six animals in Group 2 underwent 30 minutes of ischemic arrest. Six animals were given amiodarone orally for 14 days prior to cardiopulmonary bypass and ischemic arrest; the other 6 served as controls. Before cardiopulmonary bypass, the dogs administered amiodarone had significantly greater depression of dP/dtmax (p less than 0.01) and LVSWI (p less than 0.05). Thirty minutes of ischemia produced significant depression of left ventricular function in all animals in Group 2. However, a significantly greater reduction in dP/dtmax and LVSWI occurred in those animals receiving amiodarone. Furthermore, 4 of the 6 dogs receiving amiodarone were unable to sustain sufficient cardiac output following cardiopulmonary bypass to permit long-term survival (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical intervention for drug-resistant ventricular tachycardia

Endocardial resection was required in 26 patients with sustained drug-resistant ventricular tachycardia. The early mortality rate (within 30 days after operation) was 12%. Two deaths were the result of low cardiac output, and the third death was related to recurrent ventricular septal defect after septal endocardial resection. The survivors of endocardial resection were followed up from 6 to 92 months (mean 43). There were no recurrences of ventricular arrhythmias, and patients did not require antiarrhythmic drug therapy. The late mortality rate after endocardial resection was 19%. There were two late cardiac-related deaths (unrelated to arrhythmias) and three late deaths from noncardiac causes. Complete endocardial resection successfully ablates drug-resistant ventricular tachycardia, but is associated with an increased perioperative mortality rate in those patients who have severely depressed left ventricular function without a well defined left ventricular aneurysm.

Randomized trial comparing intermittent antegrade warm blood cardioplegia with multidose cold blood cardioplegia for coronary artery bypass

Forty patients were randomized to receive antegrade multidose warm (WBC) or cold blood cardioplegia (CBC) during coronary artery bypass. Cardioplegia was infused at a predetermined dose every 10 min during cardioplegia arrest and core temperature was maintained at 37 degrees C in both groups during extracorporeal circulation. Patient profiles were similar in the two groups. Cardiac index, left ventricular stroke work index, and myocardial oxygen consumption were measured before bypass and during the first 7 h of reperfusion. There was no significant difference in myocardial metabolic and function recovery, the incidence of myocardial infarction, low cardiac output or death. Our data suggests that similar protection is provided with the two techniques of myocardial protection.

Medtronic intact porcine bioprosthesis: Clinical performance to seven years

The clinical performance of the Medtronic Intact porcine bioprosthesis was evaluated in 1,084 patients (mean age 66.4 years, range 9 to 91 years) who had a total of 1,099 implantations between 1985 and 1992, inclusive. There were 709 aortic valve replacements, 297 mitral valve replacements, and 80 multiple valve replacements. Concomitant procedures were performed in 432 (39.3%). The age group distribution (years) was 35 or younger in 20 patients, 36 to 50 in 64, 51 to 64 in 274, 65 to 69 in 225, 70 or older in 500. The total follow-up time was 2,741 patient-years (mean, 2.5 years) and was 97.5% complete. The early mortality rate was 7.1% and late mortality was 3.9% per patient-year. The overall patient survival at 7 years was 70% +/- 3%. The freedom from major thromboembolism was 94% +/- 1% at 7 years (p = not significant for valve positions). The freedom from reoperation at 7 years was 93% +/- 1%; freedom from valve-related mortality was 89% +/- 2%. The freedom from structural valve deterioration at 7 years was 97% +/- 1% (aortic valve replacement 97% +/- 1%; mitral valve replacement 97% +/- 2%). The freedom from structural valve deterioration among age groups was not different for the overall population, aortic valve replacement, or mitral valve replacement. Hemodynamic assessment revealed obstructive properties for aortic valve replacement sizes of 21 and 23 mm and for mitral valve replacement sizes of 25 and 27 mm.(ABSTRACT TRUNCATED AT 250 WORDS)