Reduction of spinal cord injury with pentobarbital and hypothermia in a rabbit model.

OBJECTIVES: to evaluate the effects of hypothermia and pentobarbital on spinal cord ischaemia induced in a rabbit model. MATERIALS AND METHODS: thirty-two rabbits, allocated into four equal groups, had the infrarenal aorta clamped distal to the left renal artery and above the iliac bifurcation for 40 min. Groups 3 and 4 had infusion of 15 mg/kg of pentobarbital intravenously for 5 min, 15 min before the cross-clamping. Groups 2 and 4 had infusion of 20 ml of Ringer's lactate (LR) solution at 3 degrees C for 3 min during aortic cross clamp into the isolated aortic segment. Group 1 was untreated and served as control. Postoperative functions of spinal cord were assessed. RESULTS: paraplegia occurred in all rabbits in Group 1, in one in each of Groups 2 and 3, whereas no paraplegia was observed in Group 4. In addition 2 and 3 animals of Groups 2 and 3, respectively revealed varying degree of neurological disturbances, whereas all animals of Group 4 had normal function. This difference between Groups 2, 3, and 4 vs Group 1 was significant (p<0.002). So was the difference between Groups 2 and 4 (p=0.03), whereas the difference between Groups 3 and 4 was not significant. CONCLUSIONS: hypothermia and pentobarbital was more effective than hypothermia alone for prevention of spinal cord ischaemia in a rabbit model.

The effects of L-carnitine on spinal cord ischemia/reperfusion injury in rabbits.

BACKGROUND: Paraplegia after distal aortic aneurysm repair remains a persistent clinical problem. We hypothesized that the tolerance of the spinal cord to an ischemic period could be improved with hypothermic Ringer's Lactate containing L-Carnitine. MATERIALS AND METHODS: Twenty-eight New Zealand white rabbits were used as spinal cord ischemia models. We separated rabbits into four equal groups and clamped each animal's abdominal aorta distal to the left renal artery. We occluded the aortas above the iliac bifurcation for 30 minutes. In group I, the infrarenal aorta was clamped without infusing any solution. In group II, Ringer's Lactate solution was infused at + 25degrees C for 3 minutes at a rate of 5 ml/min into the isolated aortic segments immediately after cross-clamping and the last 3 minutes of ischemia. In group III, Ringer's Lactate solution at +3 degrees C was given in the same method as that of group II. In group IV, Ringer's Lactate solution at +3 degrees C plus 100 mg/kg of L-carnitine was infused using the same technique. We assessed the neurological status of the hind limbs 24 and 48 hours after operation according to Tarlov's criteria. All animals were sacrificed and spinal cords were harvested for histological analyses. RESULTS: The neurological status in groups III and IV was significantly superior to that of groups I and II. All the animals in group I had complete hind-limb paraplegia. Complete hind-limb paraplegia occurred in 5 rabbits in group II. Two of the 7 animals in group III had spastic paraplegia, and none at all in group IV. Histological analysis of the cross-clamped segments of the rabbits with paraplegia in group I, II and III revealed changes consistent with ischemic injury, while findings were normal for the normal animals in group III and IV. CONCLUSIONS: In this model, the infusion of hypothermic Ringer's Lactate contained L-carnitine provided sufficient spinal cord protection against ischemia. Clinically, this may be a useful adjunct for prevention of paraplegia during surgery of the descending aorta.

Desmopressin usage in elective cardiac surgery.

BACKGROUND: Desmopressin acetate (DDAVP) has been implicated as a promising agent to reduce blood loss in patients undergoing cardiopulmonary bypass. METHODS: The effects of intraoperative desmopressin were studied in 66 patients undergoing coronary artery bypass grafting, randomized equally into desmopressin and control groups. The desmopressin group received 0.3 microg/kg desmopressin at the end of cardiopulmonary bypass. RESULTS: Fibrinogen level of both groups significantly reduced at postoperative 2nd hr, whereas a significant rise was observed at postoperative 24th hr with an intergroup difference favoring the control group (p=0.0307). In the desmopressin group, the activation time of factor VIII shortened during the whole postoperative period being significant (p=0.0127) at postoperative 24th hr. Postoperative von Willebrand factor (vWF) levels of the desmopressin group were significantly higher than the preoperative ones. The control group did not show such important changes in factor VIII and vWF measurements. Platelet aggregation times of both groups prolonged at postoperative 2nd hr. The control group showed significant elevation in ADP induced aggregation time at 2nd hr and significant reductions of platelet activation percentage in response to ADP, epinephrine, collagen and ristocetin at 2nd hr. Postoperative blood loss as well as blood transfusion need did not differ between the two groups. CONCLUSIONS: Despite the improved platelet functions, desmopressin does not seem to have obvious beneficial effects on postoperative hemostasis in patients without any bleeding disorder and undergoing elective cardiac surgery.

An intraaortic solution trial to prevent spinal cord injury in a rabbit model.

OBJECTIVES: to evaluate the effectiveness of an intraaortic delivered solution on preventing spinal cord injury. DESIGN: forty rabbits were allocated into five equal groups. MATERIALS AND METHODS: one clamp was placed just distal to the left renal artery, and another was placed just above the iliac bifurcation for 40 min. Group 1 was not infused (control group). Through a 24G vascular catheter inserted into the isolated aortic segment, 20 ml of LR solution at room temperature (Group 2) 20 ml of LR solution at 3 degrees C (Group 3), and 20 ml of LR solution at 3 degrees C containing 30 mg/kg of methylprednisolone (Group 4) were infused over 3 min. In Group 5, 10 mg/kg of vitamins E and C were delivered two days before the experiment, and 20 ml of LR solution at 3 degrees C containing 30 mg/kg of methylprednisolone, and 10 mg/kg of vitamins E and C was infused at the operation. Postoperative spinal cord function was assessed using Tarlov's criteria. RESULTS: the neurologic status of Groups 3, 4, and 5 was significantly superior to that of Groups 1 and 2. No paraplegia was observed in Groups 4 and 5. Spastic paraplegia occurred in all rabbits of Groups 1 and 2, and in 20% of Group 3. In the electron microscopic evaluation of spinal cord specimens, normal histologic structure was observed in Groups 4 and 5, whereas, some derangements were observed in all others. CONCLUSIONS: intraaortic infusion of a hypothermic blended solution containing methylprednisolone, vitamins C and E provided best protection against postischaemic spinal cord dysfunction.

Acute intraoperative arterial elongation: an experimental study.

OBJECTIVES: small arterial defects resulting from either trauma or resection of an aneurysm often present difficult problems to the vascular surgeon. DESIGN: to demonstrate that certain arterial gaps as a result of traumatic injury or aneurysm resection could be closed with acute intraoperative arterial elongation. MATERIALS: fifteen mongrel dogs underwent acute intraoperative arterial elongation of the right superficial femoral artery, with the left side used for a control vessel. METHODS: arterial defects created surgically (median 50 (range 25 to 60 mm) mm). Appropriate length of artery was then undermined. A Foley catheter was placed proximally and distally directly beneath this undermined portion of vessel. The vessel is lengthened following 3 expansion/relaxation cycle of Foley catheter. Arterial gaps were closed by end to end anastomosis. Arterial pressure study was performed in all vessels. RESULTS: acutely, arterial pressure differences proximal and distal to the anastomosis were seen only when arterial gaps were exceeded 55 mm. There was no occlusion either acutely or after 4 weeks follow-up period. Light microscopic examination of arterial specimens revealed partial disruption of internal elastic lamina. At the end of the follow-up period, formation of neointima with regeneration of the internal elastic lamina was demonstrated. Scanning electron microscopy revealed minimal endothelial denudation. CONCLUSIONS: we believe that, acute intraoperative elongation can be used as an alternative technique to vein grafting for the repair of small traumatic arterial defects in selected cases.

Allograft aortic root replacement for aortic valve endocarditis with aortopulmonary fistula.

Acute infective endocarditis affecting the aortic root and valve associated with development of a fistulous communication between the aorta and pulmonary artery was presented in a young Turkish girl. Emergency surgery was required. Operation consisted initially of closure of the defect on the main pulmonary artery with a pericardial patch. This was followed by allograft aortic root replacement.

Effectiveness of endothelial cell seeding on patency of damaged vascular surfaces in a canine model.

The effects of endothelial cell seeding, which is assumed to be an effective technique to improve patency rates of denuded vascular surfaces, were investigated in an experimental model. In this study, after anesthetic induction, jugular veins of 16 dogs were harvested bilaterally. Endothelial cells were extracted enzymatically by collagenase from these veins and were passaged into a culture medium until they grew to a reasonable number. After 3 weeks, dogs were anesthetized again in a similar fashion and bilateral femoral veins were exposed and experimental intimal denudation was performed. Subsequently, one femoral artery was injected with cell solution and the other with saline solution as a control. Two weeks after the injections, arteriographic studies of femoral arteries were performed and arterial specimens were taken for histological evaluation. Our results suggest that endothelial seeding might improve the patency rate in elective but urgent cases in which endarterectomy, percutaneous transluminal angioplasty, or similar vascular procedures are considered.

Multiple coronary artery aneurysms combined with abdominal aortic aneurysm.

Coronary artery aneurysm (CAA) is defined as coronary dilatation which exceeds the diameter of a normal adjacent segment or the diameter of the patients's largest coronary vessel by as much as 1.5 times. It is an uncommon pathology with a frequency of 1-4% in routine autopsies or coronary angiographies. Atherosclerosis plays an important role in the development of CAA, and it may be a predominant cause in the majority of patients. However, the timing of surgical intervention and the treatment options for CAA are still controversial. In this report, we present a patient who had multiple CAAs of all main coronary arteries and abdominal aortic aneurysm. Different treatment modalities and indications are also discussed.

Cerebral perfusion through separate grafts for repair of acute aortic dissection with torn arch.

We have modified the technique of cerebral perfusion through anastomosed grafts for repair of acute arch dissections that require total arch replacement. We have performed this operation on a 71-year-old man with an acute type-A dissection and an arch tear between the orifices of the brachiocephalic arteries. We used 2 separate grafts for the brachiocephalic arteries and minimized brain ischemia by initiating antegrade selective cerebral perfusion after the 1st anastomosis. The patient had an excellent outcome. This method is simple and provides effective protection. Cerebral ischemic time can be kept under 30 minutes without need of a sophisticated pump setup or a multibranched graft. This affords extra time in case the surgeon encounters an unexpected lesion in the arch.

Comparative analysis of left ventricular hemodynamics and hypertrophy after aortic valve replacement with homografts or mechanical valves.

BACKGROUND AND AIM OF THE STUDY: The study aim was to examine comparatively the effects of prosthetic and homograft valves in the aortic position on ventricular hemodynamics and structure. METHODS: Hemodynamic evaluations were performed at rest and during exercise in 38 patients who had undergone aortic valve replacement (AVR) with either a homograft (n = 19) or prosthetic valve (19-23 mm; n = 19). Using echocardiographic, electrocardiographic and hematologic methods, the pressure gradient (PG); aortic valve area; diameters of left anterior wall, posterior wall (PW) and interventricular septum (IVS); ejection fraction (EF); left ventricular mass (LVM) and mass index (LVMI); electrocardiographic data of LV hypertrophy; hemoglobin; hematocrit and lactate dehydrogenase (LDH) levels were measured. RESULTS: LVM and LVMI decreased significantly after surgery in both groups (p<0.001), but the decrease was significantly greater in the homograft group (p<0.05). The IVS and PW diameters in the homograft group decreased significantly postoperatively (p<0.05); the inter-group difference was also significant (p<0.01). In the homograft group there was a significant improvement in EF (p<0.05), and the exercise PG was significantly less. Both groups showed improved LV hypertrophy and correlation between V1S >24 mm criteria and LVMI measurements. Postoperative LDH levels in the homograft group were significantly lower than preoperative levels (p<0.05); the intergroup difference was also significant (p<0.001). CONCLUSIONS: Our data suggest that homografts, as compared to mechanical prostheses, provide significantly better hemodynamics in the aortic position.

Diagnosis and treatment of concomitant aortic and coronary disease: a retrospective study and brief review.

Coronary arteriosclerosis seriously complicates the surgical treatment of aortic diseases. The aim of our retrospective study was to determine the incidence of coronary artery disease among our surgical patients in treatment for aortic dissection or aneurysm, and to determine whether coronary intervention before aortic surgery appears to affect outcomes. Between 1 January 1993 and 1 March 1998, our center treated 253 patients for aortic dissection or aneurysm. We examined these cases retrospectively for information on diagnostic and treatment methods, both for the aortic lesions and for concomitant coronary arteriosclerosis. Aortic dissection had been detected in 86 (33.9%) patients and aortic aneurysm in 167 (66.1%). Coronary angiography was performed to search for concomitant coronary artery disease in 29 (33.8%) patients with dissection and in 112 (67.1%) patients with aneurysm; of these, 11 (12. 7%) and 54 (32.3%), respectively, were found to have coronary disease. Among 43 patients with abdominal aortic aneurysm in whom coronary angiography was performed, concomitant coronary disease was detected in 36 (83.7%). Coronary artery bypass surgery was performed in 10 patients who had dissection and in 30 patients who had aneurysm; percutaneous transluminal coronary angioplasty was performed in 7 patients who had aneurysm. Perioperative mortality rates in the dissection and aneurysm groups, overall, were 23.2% and 13.8%, respectively Unfortunately, the prospective, random clinical study that would be necessary to prove the case for or against preoperative coronary angiography among subsets of patients in need of aortic repair would raise ethical questions, given the strength of the information already in our possession, gathered by less formal methods. Our study reinforces existing evidence that preoperative angiography can reduce mortality and morbidity in the elective repair of aortic aneurysm, especially thoracic or abdominal aneurysm. However, angiography should not be performed routinely in cases of aortic dissection and should be withheld in cases of type A dissection.

Proximal clamping levels in abdominal aortic aneurysm surgery.

In the surgical treatment of abdominal aortic aneurysm, the single proximal cross-clamp can be placed at 3 alternative aortic levels: infrarenal, hiatal, and thoracic. We performed this retrospective study to evaluate the advantages and disadvantages of the 3 main aortic clamping locations. Eighty patients presented at our institution with abdominal aortic aneurysms from March 1993 through May 1998. Fifty of these patients had intact aneurysms and underwent elective surgery, and 30 had ruptured aneurysms that necessitated emergency surgery. Proximal aortic clamping was applied at the infrarenal level in 24 patients (22 from the intact aneurysm group, 2 from the ruptured group), at the hiatal level in 34 patients (22 intact, 12 ruptured), and at the thoracic level (descending aorta) via a limited left lateral thoracotomy in 22 patients (6 intact, 16 ruptured). Early mortality rates (within 30 days) were 4% (2 of 50 patients) among patients with intact aneurysms and 40% (12 of 30 patients) among those with ruptured aneurysms. In the 2 patients from the intact aneurysm group, proximal aortic clamps were applied at the hiatal level. In the ruptured aneurysm group, proximal aortic clamps were placed at the thoracic level in 10 patients, the infrarenal level in 1, and the hiatal level in 1. According to our study, the clinical status of the patient and the degree of operative urgency--as determined by the extent of the aneurysm--generally dictate the proximal clamp location. Patients who present with aneurysmal rupture or hypovolemic shock benefit from thoracic clamping, because it restores the blood pressure and allows time to replace the volume deficit. Infrarenal placement is advantageous in patients with intact aneurysms if there is sufficient space for the clamp between the renal arteries and the aortic aneurysm. In patients with juxtarenal aneurysms, hiatal clamping enables safe and easy anastomosis to the healthy aorta. Clamping at this level also helps prevent late anastomotic aneurysm formation, which is frequently encountered after inadvertent anastomosis of the graft to a diseased portion of the aorta. Further studies are needed in order to confirm these results.