The effect of renin-angiotensin system blockade on visceral blood flow during and after thoracic aortic cross-clamping.

Surgical procedures necessitating clamping of the thoracic aorta are associated with a high incidence of postoperative renal dysfunction. Plasma renin activity is elevated during and after thoracic aortic occlusion in animals. The pathophysiology of the renal dysfunction may involve the renin-angiotensin system. Blockade of the renin-angiotensin system was studied in a canine model during occlusion of the thoracic aorta. Saralasin, a competitive blocker of angiotensin II, and the converting enzyme inhibitor MK422 were studied. Sixteen animals were separated into three treatment groups: control (five animals), saralasin (five), and MK422 (six). All dogs underwent clamping of the thoracic aorta for 60 minutes. In control animals, plasma renin activity increased from 0.16 +/- 0.04 to 6.41 +/- 1.57 ng/ml/hr at 30 minutes after thoracic aortic occlusion (p less than 0.05). Thirty minutes after cross-clamp release, plasma renin activity remained 10 times greater than baseline, 1.47 +/- 0.20 ng/ml/hr (p less than 0.05). Renal blood flow was measured with 15 micron microspheres before, during, and after thoracic clamping. In control animals, renal cortical blood flow decreased during cross-clamping and remained below baseline after clamp release: baseline, 7.05 +/- 0.98 ml/gm/min (standard error of the mean); 30 min after clamp release, 3.77 +/- 0.43 ml/gm/min (standard error of the mean) (p less than 0.05). In the MK422 group, renal cortical blood flows returned to baseline after cross-clamp release: baseline, 6.38 +/- 0.49 ml/gm/min; 30 minutes after clamp release, 7.30 +/- 1.6 ml/gm/min. Infusion of MK422 after placement of the thoracic aortic cross-clamp resulted in normal renal blood flow after clamp release. This protective effect was not seen with saralasin. The resumption of normal renal cortical blood flow after the administration of the converting enzyme inhibitor MK422 suggests that elevated plasma renin activity may contribute to renal dysfunction after thoracic aortic occlusion.

A decade of experience with the Model 103 and 104 Beall valve prostheses.

Mitral or tricuspid valve replacement with the Beall Model 103 or 104 prosthesis has been associated with a high incidence of late prosthetic malfunction which has necessitated reoperation. Between 1972 and 1975, 57 patients underwent single valve replacement (55 mitral and two tricuspid) with Beall Model 103 or 104 valvular prostheses and survived at least 2 years. The mean follow-up time was 73.7 months (range 24 to 119 months). Of these patients, 22 required explantation of the prosthesis; there was an operative mortality of 27%. Major prosthetic malfunction occurred in four patients: Two occluders were embolized and two occluders were fixed in the open position. All four patients required urgent operation, and two of them died. The development of symptoms of congestive heart failure, systolic murmur, or hemolysis were the reasons for cardiac catheterizations and possible reoperation. Nineteen patients had cardiac catheterization. Fifteen of these subsequently underwent reoperation, with a mortality of 26%. Three patients were considered inoperable. Cardiac catheterization data revealed significant prosthetic regurgitation in all patients: pulmonary capillary pressure 29.9 mm Hg +/- 6.7 (standard deviation); V wave 31.5 mm Hg +/- 12.0; left ventricular end-diastolic pressure 18.0 mm Hg +/- 7.8. Comparison of hemolysis indicators in this group to those of asymptomatic patients revealed that the former had a significant elevation in lactic dehydrogenase (p = 0.038) and a lowered hematocrit value (p = 0.017). Waiting for severe symptomatic deterioration to justify reoperation risks the development of left ventricular dysfunction and possible emergency reoperation with a high operative mortality.

Results of gastric interposition for reconstruction of the pharyngoesophagus.

BACKGROUND: Free jejunal transfer has become the standard technique for reconstruction of the proximal pharynx and hypopharynx. Gastric tube interposition is an effective alternative when resection extends below the thoracic inlet. This study was done to determine current indications, review morbidity and mortality rates, and to define clinical and pathologic determinants of survival associated with this procedure. METHODS: We reviewed the records of 32 patients who underwent gastric tube interposition for reconstruction of the pharyngoesophagus from 1987 to 1997. RESULTS: The overall complication rate was 50%. Complications were more frequent in the reoperative group (22% vs 66%, P < .05). The overall fistula rate was 31%. The overall mortality rate was 12%. Ultimately, 71% of patients resumed oral feedings. The 5-year actuarial survival rate was 22%. Unfavorable prognostic factors associated with significantly reduced survival (P < . 05) included margin positive resection, positive lymph node involvement, and operations done for recurrent tumor CONCLUSIONS: Reconstruction of the pharyngoesophagus with gastric tube interposition is indicated for primary tumors of the hypopharynx and cervical esophagus with inferior extension below the thoracic inlet and recurrent tumors or benign strictures in which free jejunal transfer is not feasible or has failed. It can be done with acceptable morbidity and mortality and provides reasonable expectations for long-term survival and resumption of oral intake.

Axillary thoracoscopy.

Thoracoscopy can be done safely and effectively through working ports placed in the axilla in patients whose pathology is in the upper half of the thorax. We have used this technique successfully in 37 patients with no complications. Advantages include superior cosmesis, optimal access to the apex of the chest, and, if necessary, easy conversion to axillary thoracotomy.

Acute renal failure in the cardiovascular surgical patient.

Acute renal failure is a known complication of cardiovascular surgery and is associated with a high mortality. Therapy should be aimed at prevention of oliguric renal failure, or at least its conversion to nonoliguric renal failure. Once renal failure is established, early dialysis with nutritional support probably gives the best chance for survival.

Primary malignant melanoma of the esophagus.

Primary malignant melanoma of the esophagus is a rare disease. A case is reported and the newer diagnostic techniques of immunohistologic identification of the tumor by positive reaction to the HMB-45 antigen, as well as immunoscintigraphy with Technetium-99m-labeled melanoma monoclonal antigen for the demonstration of distant metastasis, is presented. A current review of the literature on this uncommon tumor is presented, and treatment options are discussed. A total esophagectomy remains the treatment of choice. Four long-term (> 5 years) survivors after adequate surgical removal have been recorded in the literature.

Clinical experience with portable cardiopulmonary bypass in cardiac arrest patients.

To evaluate the use of portable cardiopulmonary bypass as a resuscitative tool and its impact on long-term survival of patients in cardiac arrest, we reviewed the results of 32 consecutive patients resuscitated by cardiopulmonary bypass for cardiac arrest or severe hemodynamic compromise at Northwestern Memorial Hospital over a 2-year period. Overall survival was 12.5%. Only 1 (3.4%) of the 29 patients who had cardiac arrest survived and left the hospital. All 3 patients who had severe hemodynamic compromise but not cardiac arrest were long-term survivors. Our study suggests that portable cardiopulmonary support systems used as a resuscitative tool do not prolong the survival of most cardiac arrest patients but may be useful for patients with shock due to mechanical causes and for those with profound hemodynamic compromise due to ischemia or myocardial infarction. Portable heart-lung machines can provide patients with excellent hemodynamic support; however, neurological or cardiac recovery is unlikely once cardiac arrest occurs.

Arch vessel injury during pulmonary artery catheter placement.

We have observed seven instances of unintentional cannulation of major arteries with 8F sheaths during preparation for open-heart operation. When the sheath was removed and the operation delayed, there were no complications; in the two instances in which the open-heart operation was performed immediately after arterial cannulation, there was 1 death due to hemorrhage and 1 false aneurysm of the carotid artery. Elective open-heart operations should be delayed if unintentional cannulation of a major artery occurs.

Lymphoepithelioma-like carcinoma of the lung.

Primary lymphoepithelioma-like carcinoma of the lung is rare; only 26 case reports have been identified in the literature. The present report presents a case of a 67-year-old white man with a T1 N1 M0 lymphoepithelioma-like carcinoma of the lung. He presented with severe arthritic complaints that resolved after resection of the tumor. The majority of these tumors have occurred in Asian patients who have shown evidence of previous exposure to the Epstein-Barr virus.

Baffle obstruction following the Mustard operation: cause and treatment.

Baffle obstruction developed in 11 patients after they had undergone the Mustard procedure. Eight of them required operative revision. The cause of the baffle obstruction seemed to be related to patient age (less than 1 year) and to the use of Dacron for the baffle but not to the shape of the baffle. A technique of revision that involves widely opening the previously placed baffle and enlarging it and the atriotomy with polytetrafluoroethylene was employed for the last 6 patients. All 5 survivors of this operation had good long-term results without recurrence.

A new technique for wrapping the injured spleen with polyglactin mesh.

The introduction of absorbable polyglycolic or polyglactin mesh has added a new dimension to splenic repair. Three patients with splenic disruption caused by blunt abdominal trauma underwent splenic wrapping with polyglactin mesh at the University of Virginia. The technique is described in detail. In all three instances, the spleen was saved, and postoperative nuclear medicine scans confirmed continued splenic function.

Blunt esophagectomy and gastric interposition for tumors of the cervical esophagus and hypopharynx.

Between April 1982 and June 1984, 17 patients underwent blunt esophagectomy and gastric interposition for squamous carcinoma of the cervical esophagus or hypopharynx. There was one operative death; no bleeding complications required thoracotomy or re-exploration. In two patients, a previously unknown carcinoma of the resected esophagus was discovered at the time of surgery. Blunt esophagectomy with gastric interposition is a safe technique for cervical esophageal reconstruction, as it has the added benefit of removing the entire esophagus, which has a propensity for later or synchronous carcinoma in patients with head and neck malignancies.

Application of finite-element analysis with optimisation to assess the in vivo non-linear myocardial material properties using echocardiographic imaging.

An application of finite-element analysis with an optimisation technique to assess the myocardial material properties in diastasis in vivo is described. Using the data collected from an animal model, the three-dimensional geometry of the left ventricular chamber, at several times in diastole, was reconstructed. From the measurement of the ventricular chamber pressure during image acquisition, finite-element analysis was performed to predict the expansion during diastasis. Initially, by restricting the motion of the epicardial nodes and computing the reaction forces, an 'equivalent pericardial pressure' was determined and applied in subsequent analysis. The duration of diastasis was divided into three or four intervals and the analysis was performed at each interval to assess the material properties of the myocardium. Using such a step-wise linear approach, the non-linear material properties of the myocardium during passive expansion was determined. Our results demonstrated that the computed 'equivalent pericardial pressure' increased with and was smaller than the corresponding left ventricular chamber pressure. The passive myocardium exhibited a linear tangent modulus against chamber pressure relationship which is equivalent to an exponential stress/strain relationship, similar to those suggested by in vitro studies.

Prolonged ventilatory support after open-heart surgery.

OBJECTIVES: To characterize the course of open-heart surgery patients who require prolonged (greater than 72 hrs) mechanical ventilation and to define the role and timing of tracheostomy. DESIGN: Retrospective review. SETTING: Cardiac surgery ICU and surgery wards at a university hospital. PATIENTS: All open-heart surgery patients during an 18-month period from January 1988 to July 1989 (n = 581). From this group, 58 patients (9.9%) required prolonged mechanical ventilation. INTERVENTIONS: Study patients (n = 58) were followed through the course of intubation and/or tracheostomy until they were extubated, left the hospital on ventilation, or died. MEASUREMENTS AND MAIN RESULTS: End-points for mortality and complications were determined. Overall mortality rate was 43% in the patients who required prolonged mechanical ventilation. Twenty-eight percent of the 58 patients died within the first 14 days. Of those patients who survived, 55% required an endotracheal tube only and were extubated in less than 14 days; 45% of the patients required tracheostomy. Of those patients who required tracheostomy, five (26%) were eventually extubated, seven (37%) remained mechanically ventilated, and seven (37%) died. The complication rate for endotracheal tubes was 65%; the complication rate for tracheostomy was 37%. CONCLUSIONS: Open-heart surgery patients requiring prolonged mechanical ventilation are a desperately ill subset of cardiac surgery patients. Those patients who survive are either extubated in less than 14 days or require prolonged mechanical ventilation beyond that point. In our opinion, patients should be given 1 wk to recover and one trial of weaning from the ventilator. If this approach fails, then they should undergo elective tracheostomy.

Isolated injury of the proximal vertebral artery associated with blunt chest trauma.

A patient who had sustained blunt trauma of the chest was admitted for evaluation and treatment. A thoracic aortogram was obtained to exclude mediastinal vascular injury, and an incomplete intimal disruption of the proximal left vertebral artery was found. Transient visual disturbances developed after admission, and the patient was treated by operation and vein patch angioplasty. He recovered without additional neurologic symptoms. The vertebral artery can be divided descriptively into four sections, and each section is commonly associated with particular types of injuries. This is the first reported case of an isolated injury to the proximal extraosseous portion of the vertebral artery caused by distant blunt trauma.

Effect of left atrial to left femoral artery bypass and renin-angiotensin system blockade on renal blood flow and function during and after thoracic aortic occlusion.

Temporary thoracic aortic occlusion can result in renal insufficiency with or without adjuncts to avoid distal hypoperfusion. In a canine model of thoracic aortic occlusion, left atrial to left femoral bypass was compared with blockade of the renin-angiotensin system. Renin-angiotensin system blockade with the converting enzyme inhibitor, MK422, resulted in restoration of baseline renal blood flow and glomerular filtration 30 minutes after cross-clamp release. Left atrial to left femoral bypass resulted in significant reduction in both renal blood flow and glomerular filtration 30 minutes after cross-clamp release. Stimulation of the renin-angiotensin system plays a significant role in the altered renal hemodynamics and glomerular filtration rates after thoracic aortic occlusion.

Utility of transesophageal echocardiography in the diagnosis of disease of the thoracic aorta.

PURPOSE: Transesophageal echocardiography (TEE) offers a rapid, minimally invasive method for diagnosing thoracic aortic disease. High-resolution images are possible because of the close proximity of the esophagus and vascular structures within the chest. Lung and chest wall components have little influence on the image quality and a virtually unobstructed view of the heart, thoracic aorta, and pulmonary vasculature is seen. The role of TEE in diagnosing diseases of the thoracic aorta is rapidly developing. The purpose of this study is to define the role of TEE in the diagnosis of thoracic aortic disease. METHODS: Between July 1, 1989 and December 31, 1992, 1005 TEEs were performed at our center. Of these, 199 (125 men, 74 women) were entered into our aortic disease registry. Indications for the studies included 37 referrals to rule out aortic dissection, 18 to assess aortic aneurysm, 55 to assess for an intraaortic source of embolus, 9 to rule out intraaortic thrombus, and 13 with familial hyperlipidemia being followed to mark response to low-density lipoprotein apheresis. In 67 cases, subclinical aortic plaquing was found incidentally. No complications from the TEE procedure were encountered. RESULTS: In cases of suspected aortic dissection, TEE was equal to computed tomography (CT) scanning in identifying the type (DeBakey) and extent of thoracic aortic dissection. In addition, TEE provided information regarding functional status of the aortic valve, identified interluminal communications, and assessed blood flow and thrombus burden in the false lumen. TEE correctly identified true aneurysms, intraluminal thrombus, and plaques as possible sources of emboli. One false-positive CT scan result for aortic dissection was seen and was ruled out both by TEE and angiography. CONCLUSION: Biplane TEE can be considered the method of choice in diagnosing disease of the thoracic aorta. Information from TEE can be obtained at the patient's bedside or in the operating suite, to assess surgical results before procedure termination and afterward for follow-up. Adjunctive magnetic resonance imaging, CT scanning, or aortography may be needed to assess extension of the disease process into the abdomen or pelvis or to plan surgical intervention.

The effect of hyperemia on spinal cord function after temporary thoracic aortic occlusion.

Nineteen mongrel dogs had 30 minutes of thoracic aortic occlusion to determine the effects that blockade of the renin-angiotensin system may have on preserving spinal cord blood flow and function during a period of temporary spinal cord ischemia. Cross-clamping of the thoracic aorta causes renal ischemia and activates the renin-angiotensin system with resulting increased production of angiotensin II. Angiotensin II is a potent peripheral constrictor and elevated levels may constrict collateral spinal cord circulation. At the time of aortic cross-clamping, 10 dogs received 100 mg/kg of MK422 (intravenous enalapril maleate), a converting enzyme inhibitor, and nine animals served as controls. The blockade of the renin-angiotensin system had no preserving effects on spinal cord flow as measured by microspheres and on spinal cord function as graded with the Tarlov scale. However, the paraplegic animals all had significantly increased lower thoracic and lumbar spinal cord flows 30 minutes after clamp release when compared with those animals that remained neurologically intact. In conclusion, marked hyperemia occurring after a period of hypoperfusion may lead to spinal cord edema and compartment syndrome with resulting paraplegia.