S. Fehmi Katircioglu

Effect of Mg2SO4 usage on spinal cord ischemia-reperfusion injury: Electron microscopic and functional evaluation

Objectives: To evaluate the effects of intravenous magnesium sulfate (Mg2SO4) administration on ischemia-reperfusion injury of the spinal cord. Material and Methods: Sixteen rabbits were randomly assigned to the control (group I, 8 rabbits) and the study group (group II, 8 rabbits). The abdominal aorta was clamped for a period of 30 min followed by a reperfusion period of 60 min. The animals in group II received 0.25 ml/kg/h Mg2SO4 intravenous infusion (15% Mg2SO4) throughout this procedure. The animals were then observed for 24 h after which their neurological states were evaluated and tissue samples obtained from the spinal cord were examined with electron microscopy. Results: Aortic pressure distal to the cross-clamp during the occlusion period was 9 ± 3 mm Hg in group I and 19 ± 6 mm Hg in group II. All animals in group I were paraplegic at the end of the study. In group II the neurological outcome of 1 animal was poor while the other 7 animals were neurologically in a good condition. Electron microscopic examinations of the spinal cord tissues of group I revealed severe injury but the ultrastructure was well preserved in group II. Conclusions: Intravenous Mg2SO4 administration may have protective effects on the ischemia-reperfusion injury of the spinal cord. We propose that Mg2SO4 may be an additional protective pharmacological agent in thoracal and thoracoabdominal aortic surgery.

On‐Pump Beating Heart Versus Hypothermic Arrested Heart Valve Replacement Surgery

Abstract  Background: Comparison of neurological parameters in patients undergoing prosthetic heart valve replacement with two operating techniques—either cardioplegic arrest of the heart under hypothermic cardiopulmonary bypass (CPB) or the heart beating on normothermic bypass, with or without cross‐clamping the aorta, without cardioplegic arrest. Methods: Fifty valvular surgery patients were randomly assigned into three groups. Sixteen patients underwent beating heart valve replacement with normothermic bypass without cross‐clamping the aorta, 17 patients underwent the same procedure with cross‐clamping the aorta and retrograde coronary sinus perfusion, and the remaining 17 patients had conventional surgery with hypothermic bypass and cardioplegic arrest. Results: Two‐channel electroencephalography (EEG) was recorded to assess changes in cerebral cortical synaptic activity and 95% spectral edge frequency values were recorded continuously. Bispectral monitoring was used to measure the depth of anesthesia. Blood flow rates in middle cerebral artery (MCA) were measured by transcranial Doppler (TCD). Reduction in spectral edge frequency (>50%) or bispectral index (BIS) (<20) or transcranial Doppler flow velocity (>50%) was detected in four patients in Group 1, five patients in Group 2, and three patients in Group 3. BIS or EEG values never reached zero, which indicates isoelectric silence during surgery. Gross neurological examinations were normal in all patients postoperatively. Conclusion: There is no difference regarding neurological monitoring results between on‐pump beating heart and hypothermic arrested heart valve replacement surgery. Also no significant difference was encountered among the groups regarding the clinical outcomes.

Levosimendan Effect on Spinal Cord Ischemia-Reperfusion Injury Following Aortic Clamping

Abstract  Background and aim of the study: The new calcium sensitizer, levosimendan, not only acts as a positive inotropic agent but also, vasodilates both venules and arterioles. The aim of this experimental study was to investigate whether levosimendan has protective effects on spinal cord ischemia‐reperfusion injury. Material and Methods: Twelve New Zealand rabbits were enrolled in this study. In addition to the control group, levosimendan is administered to the experimental group with a loading dose of 12 μg/kg prior to ischemia over a 10‐minute period, followed by an infusion of 0.2 μg/kg/min during the ischemia period (30‐minutes). Following the neurologic evaluation at the 24th hour of reperfusion, lumbar spinal cords were removed in order to perform microscopic examination and malondialdehyde (MDA) and myeloperoxidase (MPO) measurements. Results: The mean Tarlov score of the levosimendan group (3.25) was higher than the control group (0.7) (p< 0.05). MDA level was found significantly lower in the levosimendan group when compared with the control group as 1.6 ± 0.4 nmol/gr and 189.3 ± 43.6 nmol/gr respectively (p < 0.05). MPO level was also found statistically significant when we compared levosimendan group with the control group. It was calculated as 11.3 ± 1.0 μ/gr tissue and 39.1 ± 16.9 μ/gr in the levosimendan and the control groups (p< 0.05). Light microscopic examination was carried out with tissue samples in the 24th hour of the reperfusion. Levosimendan group had better preservation with the microscopic appearance with respect to the control group. Conclusion: Levosimendan exhibits an important protection by means of neurological outcome, histopathological, and biochemical analysis for the ischemia‐reperfusion injury of the spinal cord following the aortic clamping.

Levosimendan and severe pulmonary hypertension during open heart surgery

Weaning from cardiopulmonary bypass is the most important stage during mitral valve surgery, especially in patients with severe pulmonary hypertension. We report two patients with severe pulmonary hypertension who were operated on because of valvular heart disease. To reduce the pulmonary artery pressure, levosimendan was used because of its vasodilatory and cytoprotective effects. All patients tolerated the operation and levosimendan administration. Their postoperative course was uneventful. Levosimendan can be used to treat pulmonary hypertension during operations for heart valve disease. Patients clearly benefit from the vasodilator action of the drug for reducing pulmonary artery pressure.

Acute mechanical valve thrombosis of the St. Jude medical prosthesis.

Abstract From 1986 to 1996, 2585 patients underwent valve replacement with the St. Jude medical prosthesis. Sixty experienced mechanical valve thrombosis. Seventeen of 60 patients (28.3%) had isolated aortic valve replacements, 33 had isolated mitral valve replacements (55%), and 10 had double valve replacements (16.7%) (aortic and mitral valve replacement). All patients who underwent reoperation for mechanical valve thrombosis were functional Class III or IV. Against medical advice, systemic anticoagulation with warfarin sodium had been discontinued or used only intermittently. Thus, anticoagulant activity was not adequate. The diagnosis of thrombosis was made by clinical examination, laboratory findings, and echocardiography and cineradiography. Of the 60 patients, 9 patients died early after surgery or before discharge. Most of the deaths were attributed to low cardiac output. The overall hospital mortality was 15%. The overall 10‐year actuarial survival rate was 82.8 ± 1.6%. In our study, reoperation for thrombosed mechanical prosthesis was not an independent parameter determining mortality. Age was the only statistically important hospital mortality predictor. Of this group, 90% suffered mechanical valve obstruction within the first 5 years after operation. These results suggest that valve re‐replacement appears to be a suitable surgical treatment for thrombosis of mechanical prosthetic valves, especially in the young. In these patients subsequent anticoagulation management is necessary.

Aortic Valve Replacement With the St. Jude Medical Prosthesis and Fixed Dose Anticoagulation

Abstract Over a 10‐year period, between 1986 and 1996, 865 patients underwent primary aortic valve replacement (AVR) with the St. Jude Medical mechanical prosthesis. Patients who had undergone valve replacement with a different type of prosthesis previously were excluded from this study. Patient age ranged from 11 to 79 years. The mean age was 42.9 ± 14.54. The gender distribution was 396 men (45.8%) and 469 women (54.2%). All patients received 2.5 mg/day Coumadin after extubation. A combination of the antiagregant therapy (Dypridamole 3 × 75 mg/day, Asprine 100 mg/day) was added after removal of the chest tubes. The dosage of Coumadin was maintained constant regardless of the prothrombin time (PT) or cardiac rhythm. There were 101 valve‐related complications (4.2% per patient year [ppy]) occurring in the late follow‐up period. Of these complications; 38 were anticoagulant‐related hemorrhage (1.58% ppy), 3 were paravalvular leak (0.12% ppy), and 36 were thromboembolism (1.4% ppy). There were 24 reoperations (0.99% ppy) and 17 late deaths. The linearized late mortality rate was 0.7% ppy. Long‐term survival estimates at 5 and 10 years were 97.14 ± 0.82% and 94.86 ± 1.54%, respectively. We conclude from the data that the St. Jude Medical valve may allow the use of a low level of anticoagulation. This study shows that fixed dose oral anticoagulation does not increase the rate of thromboembolism in patients with the St. Jude aortic valve. This protocol does not result in reduction of bleeding complications, however.

Beating-Heart Mitral Valve Reoperation in a Patient With a Permanent Pacemaker

Abstract  A 60‐year‐old man with a history of a prior double‐valve replacement (DVR) and permanent pacemaker implantation underwent mitral valve reoperation due to a paravalvular leak. Reoperation was performed on a beating heart (BH) on cardiopulmonary bypass, by perfusing the heart continuously with oxygenated noncardioplegic normothermic blood via the coronary sinus. We report the case of a patient who underwent mitral valve reoperation on a beating heart, 10 years after his first double‐valve replacement and permanent pacemaker implantation.

Experimental Inhibition of Protamine Cardiotoxicity by Prostacyclin

Twelve animals (26 ± 5 kg) were subjected to the study. In this experimental study, the authors used prostacyclin to inhibit the toxic metabolite release during protamine admin istration. Animals were divided into two equal groups. Six animals received prostacyclin (the prostacyclin group), and the other six animals did not receive any additional treatment (the control group). All cardiac output and biochemical measurements were evaluated at baseline; before cardiopulmonary bypass; and at 5, 30, and 60 minutes after protamine administration. The measured cardiac index showed that the hearts treated with prostacyclin had satis factory preservation of left ventricular function. Metabolic and biochemical data showed that the tumor necrosis factor level was raised significantly in the control group (20.75 ± 2.2 in the control group and 13.75 ± 2.5 pg/mL in the prostacyclin group). Also, E and P selectin levels were elevated in the control group, but this change was less marked in the prostacyclin group. In addition, the intracellular adhesion molecule-1 (ICAM-1) level was significantly higher in the control group than in the prostacyclin group (9.26 ±2.13 in the control group and 5.13 ± 1.66 ng/mL in the prostacyclin group). The authors observed that prostacyclin inhibited the toxic mediator release during heparin reversal with protamine. This inhibition is one way of protecting the myocardium reserves from protamine cardiotoxicity.

Iloprost added to the cardioplegic solutions improves myocardial performance.

A total of 12 mongrel dogs were divided into two equal groups. Six animals received IIoprost and the other 6 animals did not receive any additional treatment. In the Iloprost group, Iloprost was added to the cardioplegic solution (25 ng). Also, Iloprost was used (10 ng/kg/min.) 5 min. before and after cross-clamping. All cardiac output and biochemical measurements were evaluated before cross-clamp and 15 min., 1 h, and 4 h after cross-clamp. The measured dp/dt shows that the hearts treated with Iloprost preserved left ventricular function. Comparison of contractility indices between the groups revealed that contractile recovery was 59% in the control group and 71% in the Iloprost group (p < 0.05). Tumor necrosis factor (TNF) alpha level was significantly elevated in the control group (p < 0.001). Its level was 22.2 +/- 2.2 pg/mL in the control group and 13.8 +/- 1.0 pg/mL in the Iloprost group. E- and P-selectin levels were elevated in the control group (p < 0.001). ICAM-1 level was also elevated in the control group. ICAM-1 level was 17.7 +/- 1.8 ng/mL in the control group and 8.5 +/- 1.8 ng/mL in the Iloprost group. The Iloprost that was added to the cardioplegic solution and low dose administration during the pre- and post-ischemic period inhibits the toxic mediator release from endothelium-leukocyte interaction and reduces the severity of ischemia-reperfusion injury.

Mitral Valve Replacement with the Beating Heart Technique in a Patient with Previous Bypass Graft from Ascending to Descending Aorta due to Aortic Coarctation

Abstract  Background and Aim: Conventional mitral valve replacement (MVR) is carried out under cardioplegic arrest with cross‐clamping of the ascending aorta during cardiopulmonary bypass. In this case, MVR was performed with on‐pump beating heart technique without cross‐clamping the aorta because of the diffuse adhesion around the ascending aorta, and tube graft presence between ascending and descending aortas. Methods: A 47‐year‐old female patient had aorto‐aortic bypass graft from ascending aorta to descending aorta with median sternotomy and left thoracotomy in single stage because of aortic coarctation 2 years ago in our cardiac center. She was admitted to the hospital with palpitation and dyspnea on mild exertion. Transthoracic echocardiography revealed 4th degree mitral insufficiency. Results: MVR was carried out through remedian sternotomy with on‐pump beating heart technique without cross‐clamping the aorta. Conclusions: MVR with on‐pump beating heart technique offers a safe approach when excessive dissection is required to place cross‐clamp on the ascending aorta.