Competitive NMDA receptor antagonists and spinal-cord ischemia

Ischemic neuronal death is associated with excitatory amino acid (EAA) release. Their action is mediated by N-methyl-D-aspartate (NMDA) receptors. Blockade of the receptors before the ischemic insult can decrease neuronal damage. Accordingly, we investigated the protective effect during spinal cord ischemia of two competitive antagonists, 4-(3-phosphonopropyl)-2-piperazine-carboxylic acid (CPP) and cis-4-(phosphonomethyl)-2-piperidine-carboxylic acid (CGS). Male Sprague-Dawley rats underwent intrathecal administration of 10 microL saline, CGS, and CPP 10 mM solutions, in a randomized blinded fashion, and were subjected to balloon occlusion of the thoracic aorta. Proximal aortic pressure was lowered to a mean of 40 mm Hg by partial exsanguination. In the acute protocol, 21 rats divided in 3 groups of 7 (saline, CPP, and CGS) were used to calculate the aortic occlusion time (AOT) resulting in paraplegia in 50% of animals (P50). In the chronic study, 24 rats divided in 4 groups of 6 (saline, CPP, CGS, sham) underwent 12-min occlusion. The chronic animals were scored daily for 28 days and submitted to histology of the cord. In the acute study, the P50 of CGS (10 min 48 s) and CPP (11 min 11 s) was longer than saline (10 min 27 s). In the chronic groups, analysis of variance of neurologic (p = .66) and histologic (p = .66) scores did not disclose differences between CGS, CPP, and saline. In conclusion, blockade of NMDA receptors with CPP or CGS may afford some protection for durations of occlusion around the P50, but it is not beneficial when ischemic injury is more protracted.

Heterotopic pancreas of the esophagus masquerading as Boerhaave's syndrome

Heterotopic pancreas (HP) of the esophagus is rare. We report a patient with HP of the esophagus and review the presentation, treatment, and results of the nine previously reported cases. Two patients had cancer. This high incidence raises concerns that HP of the esophagus may be premalignant. Because surveillance endoscopy is not possible, all known or suspected esophageal HP should be treated surgically.

Catastrophic hemorrhage on sternal reentry: still a dreaded complication?

BACKGROUND

To define the incidence of catastrophic hemorrhage (CH) during reoperations, the experience of the University of New Mexico was reviewed and compared with the practice of surgeons contacted by questionnaire.

METHODS

At the University of New Mexico, 610 reoperations were reviewed and 210 deemed high risk because of multiple reoperation, aneurysm, patent grafts, chamber's enlargement, conduit or previous mediastinitis. In the questionnaire, we asked about reentry technique, occurrence and outcome of CH, and precautions for high-risk patients.

RESULTS

At the University of New Mexico there were 4 CH with 1 death, and in the questionnaire there were 2,046 CH with 392 deaths. Our rate per surgeon was lower than that of the questionnaire. Rate of CH according to the saw was 2.09 for reciprocating, 2.0 for sagittal, and 1.74 for stryker in the questionnaire. Our rate was lower (0.65) with a micro sagittal saw. High-risk category predicted CH during sternotomy (p = 0.01) but only conduit (p = 0.005) was significant by univariate analysis.

CONCLUSIONS

The risk of CH could be as high as 1%. The sagittal micro oscillating saw is the safest reported to date. Presence of a conduit increases the risk by 2.5 fold.

Retrograde perfusion of the spinal cord during aortic crossclamping: initial observations in the swine model

BACKGROUND

Retrograde perfusion has emerged as a useful technique for the preservation of the heart and brain when arterial circulation is interrupted. Herein, this study was designed to test the hypothesis that retrograde perfusion of the azygos vein is sufficient to maintain viability of the spinal cord during aortic occlusion in the swine model.

METHODS

Female swine, 17 to 22 kg, underwent left thoracotomy, creation of a shunt between the aortic arch and the azygos vein, and aortic crossclamping for 60 minutes: the shunt was open in the retrograde perfusion group (n = 5) and closed in the control group (n = 4). The animals were evaluated for neurologic function for 8 days and killed. Spinal cords were processed for histologic examination. Additional animals underwent left thoracotomy and injection of a casting solution in the azygos vein (n = 2), left thoracotomy and angiography of the azygos vein (n = 2), and a compartmentalization procedure to separate the azygos vein from the caval system followed by angiography (n = 2).

RESULTS

Differences in the neurologic (2-sample t test, P =.11) and histologic (2-sample t test, P =.65) scores of retrograde perfusion and control groups were likely due to chance. Casting and angiography groups showed extensive collaterals between azygos and caval systems, only partially interrupted by compartmentalization.

CONCLUSIONS

Retrograde perfusion does not protect the spinal cord from ischemic injury. The collateral network between the azygos and caval systems prevents the oxygenated blood from reaching the cord. Surgical separation between the 2 systems was only partially successful in this study.

Selective protection of gray and white matter during spinal cord ischemic injury

BACKGROUND

Ischemic injury in the gray matter is associated with excitatory amino acid neurotransmitters (EAA) release, and in the white matter is associated with intracellular sodium accumulation. We investigated the protective effect during spinal ischemia of the EAA antagonist, 2-carboxypiperazinyl-propylphosphonic acid (CPP), and the sodium channel blocker (2,6-dimethylphenylcarbamoylmethyl) triethylammonium bromide (QX).

METHODS

Sprague-Dawley rats were randomized in four groups, received intrathecally 10 microL of saline, CPP, QX, or QX/CPP, and underwent balloon occlusion of the aorta. Proximal pressure was lowered by exsanguination. In the acute protocol, 28 rats were used to calculate the length of occlusion, resulting in paraplegia in 50% of animals (P50). In the chronic study, 60 rats underwent 11' occlusion. The chronic animals were scored daily for 28 days and submitted to cord histology.

RESULTS

The P50 of QX (11'22") and QX/CPP (11'54") were longer than saline (10'39"), suggesting a beneficial effect. Neurologic scores of all treatment groups (p = 0.0001) and histologic scores of CPP (p = 0.003) and QX/CPP (p = 0.002) were better than saline.

CONCLUSIONS

Protection of spinal cord during ischemia can be achieved with intrathecal administration of selective agents directed to the gray and white matter.

Posterior ventricular septal rupture: an anatomical reconstruction

Rupture of the ventricular septum following posterior myocardial infarction is an uncommon, but lethal, injury that requires prompt repair. Surgical reconstruction can be complex, demanding, and unfamiliar. Conventional techniques, as described in the literature, are associated with a variety of potential pitfalls. An alternative method we have successfully used in our last four patients is presented in detail. The procedure uses two composite (felt/pericardium) patches: an internal patch to reconstruct the left ventricular geometry and an external patch to repair the subtotal infarctectomy. For maximal security, all suture lines sandwich myocardium between two continuous felt surfaces. Specific transition stitches are described, which reliably anchor the entire repair at the critical, but poorly visualized, areas where the ventricular septum makes its transition to left and right ventricular free walls. This technique offers immediate hemostasis and a more anatomical left ventricular geometry. The method also reduces the risk of systemic thromboembolism, residual VSD, and repair disruption.

Mediastinitis without antecedent surgery

The study evaluates the results of aggressive surgical treatment for mediastinitis without antecedent surgery, after retrospectively reviewing all patients with mediastinitis, excluding patients with prior cardiac, esophageal or mediastinal operations, treated between June 1, 1992 and August 1, 1996. 8 patients were treated. 7 were male, mean age was 58 years. The etiology was Boerhaave's syndrome in 4, iatrogenic injury in 2 and descending necrotizing mediastinitis in 2 patients. The mean number of operations was 2.5. The initial operation was through thoracotomy in 5 patients and sternotomy in 2 patients. 4 patients underwent neck drainage, 1 as primary treatment and 3 combined with transthoracic drainage. 1 patient received laparotomy. Mean hospitalization was 52 days (excluding 1 death). Complications included mechanical ventilation greater than 48 hours in 7 patients, 2 or more operations in 5 patients, multisystem organ failure in 5 patients and other complications in 6 patients. Death occurred in one patients. Mediastinitis without antecedent surgery is associated with significant morbidity, however, with aggressive surgical drainage 87% of patients survived.

Videothoracoscopic treatment of hepatic hydrothorax

Hepatic hydrothorax occurs frequently in ascites arising from communications in the diaphragm between peritoneal and pleural cavities. Numerous treatments have been described but are of limited utility due to invasiveness and poor success rate. We describe a case of hepatic hydrothorax in which the pore in the diaphragm was documented photographically and in which successful resolution was achieved with videothoracoscopic suture ligation and talc pleurodesis.

Head, face, and neck trauma from large animal injury in New Mexico

BACKGROUND

Head, face, and neck injuries (HFNI) occur during animal-related trauma. We compared patients with HFNI and without HFNI after animal-related injuries to determine the significance of these injuries.

METHODS

Retrospective review of admissions for animal injuries between January 1, 1990, and December 31, 1995, by age, gender, mechanism, animal, Glasgow Coma Scale (GCS) score, Injury Severity Score (ISS), Abbreviated Injury Severity score for head and neck (AIS Head/Neck), AIS score for face (AIS Face), intensive care unit stay, hospitalization length, morbidity, and mortality.

RESULTS

There were 153 admissions: 61 HFNI and 92 no HFNI. Significant differences occurred in gender, animal, activity, GCS, and ISS. HFNI had higher AIS Head/Neck, AIS Face, and mortality. HFNI were from horses in 87% and occurred during recreation in 89%; 39% of patients with HFNI were 18 years or younger.

CONCLUSION

HFNI occur in females and young people and produce lower GCS score, higher ISS, higher AIS Head/Neck, higher AIS Face, and higher mortality. Most occur during recreational horseback riding. Protective headgear should be mandated.

Intrapleural fibrinolytics in management of empyema thoracis

STUDY OBJECTIVE

To determine the success and complication rates of fibrinolytic therapy (FL) in the treatment of thoracic empyema.

DESIGN AND PATIENTS

Between December 1992 and November 1994, all patients referred with empyema thoracis (ET) were offered FL. FL consisted of streptokinase (275,000 +/- 170,000 IU) or urokinase (121,000 +/- 57,000 IU) daily for a mean of 6.2 +/- 2.1 days.

SETTING

The University of New Mexico Health Sciences Center and the Albuquerque Veterans Affairs Medical Center.

RESULTS

Twenty-six patients were treated. Sixty-two percent (16/26) had complete resolution (CR) of symptoms, near or complete normalization of chest radiographic findings, and required no surgery or empyema tubes. Eight percent (2/26) had relief of symptoms and partial resolution (PR) of radiographic abnormalities and were discharged from the hospital with empyema tubes in place. All patients with PR had empyema tubes removed within 30 days of hospital discharge. Thirty-one percent (8/26) of patients failed to completely improve clinically or radiographically (nonresponse) and were treated with decortication or empyema tubes for greater than 30 days. Bleeding occurred in a single patient (4%). There was no mortality associated with FL use.

CONCLUSIONS

The use of FL is associated with resolution of ET in 69% (18/26) of patients. This modality is safe, effective, and spares most patients with empyema the morbidity and mortality of thoracotomy.

Multiple polyposis and adenocarcinoma arising in Barrett's esophagus

Adenomatous polyps of the esophagus are rare in comparison with those of the lower gastrointestinal tract. Like adenomatous colon polyps, they have been associated with malignancy. We describe a case of early adenocarcinoma and multiple polyposis of the esophagus arising in a Barrett's epithelium, treated with surgical resection.

Internal fixation of high tracheal stents

A technique for internal fixation of a silicone elastomer tracheal stent is described. This technique allows the use of a short stent in situations where complex stent placement otherwise would be necessary. The procedure was used successfully to manage a postresection stricture in the subglottic trachea.

Bacterial wound colonization after broad-spectrum versus narrow-spectrum antibiotics

Broad-spectrum versus narrow-spectrum antibiotic prophylaxis for patients who undergo cardiac operations is variously advocated to reduce the incidence of all infections or, conversely, to prevent resistant superinfections. Previous studies of prophylaxis have shown a reduction in the incidence of staphylococcal infections with some increased resistance. We studied preoperative and postoperative wound colonization as a surrogate for infection. Among 78 patients undergoing cardiac procedures, the type of prophylaxis was allocated as follows: narrow-spectrum (nafcillin), 24 patients; midspectrum (cephapirin), 26 patients; and broad-spectrum (ceftriaxone), 28 patients. Seventeen patients who underwent other procedures received no antibiotics and served as controls. Cultures of the operative site were done preoperatively, and 3 and 6 days postoperatively. The incidence of preoperative skin colonization with staphylococci was identical (95%) in all groups. Postoperatively, more patients receiving nafcillin (48%) were culture-negative for all organisms than were either of the other groups receiving antibiotics (27% and 22%) (p < 0.05). Gram-negative bacilli were infrequent colonizers and neither did the incidence of infection with these organisms increase nor did resistance develop in any group. The infection rates were not different among the treatment groups. Thus, a narrow-spectrum antistaphylococcal penicillin may offer an advantage in terms of both prophylaxis for cardiac operations and hospital costs.

Selective vulnerability of white matter during spinal cord ischemia

The long-term effects of spinal cord ischemia were studied in 21 rats by lesion scores (LS, n = 21), somatosensory evoked potentials (SEP, n = 16), electromyographic measurements (EMG, n = 12) and histology of the spinal cord (n = 21) 48.5 +/- 57.2 days after 10- to 12-min occlusion of the thoracic aorta and subclavian arteries. All the animals were initially paraplegic with a spastic presentation but seven recovered within 2 days (group A), demonstrating low LS (3.4 +/- 1.05) normal EMGs (n = 3) and unremarkable histology. The 14 paraplegic animals presented relevant findings of the lumbar cord consisting of white matter lesions only (group B, n = 7) or white and gray matter lesions (group C, n = 7). Group B animals showed severe deficit (LS = 11.8 +/- 2.93) without denervation on EMG (n = 5) or muscle atrophy on histology. Group C animals displayed equal impairment (LS = 14.4 +/- 0.71), denervation on EMG (n = 4), and muscle atrophy. Resting motor unit activity of groups B and C were significantly different from group A (p < 0.001), while LS of groups B and C did not differ (p = 0.083). These data underscore the nature and the extent of white matter lesions during spinal cord ischemia, a finding which has generally been eclipsed by emphasis on gray matter lesions in previous studies.

Efficacy, complications, and cost of a comprehensive blood conservation program for cardiac operations

We reviewed blood use in 118 consecutive patients who underwent primary, elective cardiac operations in 1989. In June 1989 we initiated a blood conservation program that included attempts to limit preoperative aspirin use, intraoperative phlebotomy and hemodilution, use of a cell conservation device (Electromedics, Inc., Englewood, Colo.) to concentrate residual oxygenator contents, reinfusion of chest drainage, and acceptance of a minimum hemoglobin level of 8.0 gm/dl in stable patients. Patient characteristics were similar for patients operated on both before (n = 58) and after (n = 60) initiation of the blood conservation program, except for age and preoperative aspirin use (both greater in postconservation patients). Fewer blood products were transfused (5.8 +/- 5.7 units per patient before conservation versus 4.0 +/- 7.4 units per patient after conservation; p = 0.005). More complete data were available for 82 patients (40 patients before conservation and 42 after conservation). In the postconservation patients, 20 of 42 had 575 +/- 140 ml of blood withdrawn before cardiopulmonary bypass and reinfused afterward, 26 of 42 had 806 +/- 376 ml of blood processed with the cell conservation device returned, and 21 of 42 patients had an average of 287 +/- 127 ml of chest drainage reinfused. Chest tube drainage, postoperative hematologic parameters, and the prevalence of complications were not significantly different between groups. Stepwise linear regression analysis identified intraoperative withdrawal of blood before cardiopulmonary bypass, bypass duration, and preoperative hematocrit value as predictors of blood use. Intraoperative withdrawal of blood before cardiopulmonary bypass is an important conservation measure, and its use should be expanded.

Successful repair of left ventricular rupture after redo mitral valve replacement

A patient with an extensive type I left ventricular rupture after a redo mitral valve replacement was successfully treated using a patch of glutaraldehyde-preserved pericardium sutured to the endocardium around the tear.

Arteriovenous and capillary hemangiomas of the interventricular septum

The case of a patient with two extremely unusual types of hemangioma is presented. The arteriovenous and capillary hemangiomas of the interventricular septum were discovered on coronary angiography performed for chest pain. Echocardiography confirmed the diagnosis. Successful surgical excision was performed.

Observations on flow characteristics of passive external aortic shunts

Extraluminal heparin-bonded shunts have been recommended to support the distal circulation and decompress the proximal vascular bed during procedures that require interruption of flow through the thoracic aorta. Shunts that originate in either the left ventricle or the proximal aorta are generally viewed as hemodynamically similar, despite incomplete documentation of their flow characteristics. The present study was conducted to further define these hemodynamic properties. Identical extraluminal shunts were placed from the left ventricular apex and aortic arch to the distal thoracic aorta in mongrel dogs. Simultaneous pressure and Doppler flow velocities were recorded in the carotid and femoral arteries. Computer-enhanced composite waveforms were used to assist data analysis. When compared to ventricular cannulation, aortic cannulation provided improved proximal decompression and increased mean distal flow. In addition, significant diastolic flow reversal was recorded in the distal circulation when ventricular cannulation was employed. On the other hand, ventricular cannulation was associated with the preservation of pulsatile flow, whereas flow generated by aortic cannulation was linear. It is concluded that extraluminal shunts that originate in the left ventricle and the proximal aorta have distinct hemodynamic properties. These differences may be clinically important in specific situations.

Lung cancer--current concepts and controversies

The recent literature contains a variety of controversial management alternatives for patients with pulmonary malignancy that affect all aspects of the lung cancer problem. Revisions in the classification system have been advanced in which the prognostic implications of specific ultrastructural and histochemical information are acknowledged. Computed tomography and, to a lesser extent, nuclide scanning have revolutionized the staging process, but limitations in these procedures are emerging. Improved survival following aggressive surgical treatment has challenged the adequacy of the standard staging system. The palliative role of radiotherapy is becoming more widely appreciated. Results of immunotherapy are equivocal and gains from chemotherapy are modest. Combinations of treatment modalities will require further documentation before they can be recommended with confidence.

Use of a sagittal oscillating saw for repeat sternotomy: a safer and simpler technique

A method of repeat sternotomy using a microsagittal oscillating saw is described. We have found this method to be safer and simpler than previously described techniques. We have used this technique in more than 50 repeat sternotomies without a single complication related to the mediastinal reentry procedure.

Unusual complication of direct left atrial pressure monitoring line

We are here reporting the case of a left atrial pressure monitoring line that caused mechanical interference with the functioning of a Björk-Shiley mitral valve. The catheter wedged the disc into a closed position and caused the patient's death.

Differential inhibition by aspirin of vascular and platelet prostaglandin synthesis in atherosclerotic patients

We studied the ability of a single oral dose of aspirin to inhibit prostacyclin synthesis by human arterial and venous tissue and to inhibit thromboxane A2 synthesis by platelets in 70 patients who were undergoing aortocoronary bypass. A dose of 40, 80, or 325 mg of aspirin was administered 12 to 16 hours before surgery. The generation of thromboxane in serum--which provides an estimate of platelet thromboxane production--was reduced from the control value by 77, 95, and 99 per cent after single doses of 40, 80, and 325 mg of aspirin, respectively. By contrast, prostacyclin production in aortic tissue that was removed at operation was reduced by only 35, 38, and 75 per cent, respectively, in response to these doses. Production of prostacyclin in saphenous-vein tissue (not tested after 40 mg of aspirin) fell only slightly and not significantly after 80 mg but was reduced by 85 per cent after 325 mg. These findings indicate that a low dose of aspirin (40 to 80 mg) can largely inhibit platelet aggregation and thromboxane synthesis but has much less effect on prostacyclin production in arterial and venous endothelium.

Prostacyclin production by arterialized autogenous venous grafts in dogs

Arteries are capable of producing significantly larger quantities of prostacyclin than are veins. To test the hypothesis, whether prostacyclin production by the vessel wall is related to blood pressure and flow, we measured the amounts of PGI2 released and synthesized by venous segments transplanted for 6 weeks into the arterial circulation. These results were compared with the production of prostacyclin by normal veins and arteries. In 20 dogs a segment of jugular vein was interposed into the carotid system; a sham dissection was done on the opposite side. "Arterialized" vein grafts showed prominent intima lined by endothelium, medial smooth muscle cell proliferation and fibrotic proliferation in adventitia. Spontaneous and arachidonic acid-stimulated prostacyclin production (measured by radioimmunoassay for 6-keto-PGF1 alpha) was not significantly different between arterialized venous autografts and jugular veins. Significantly larger amounts of prostacyclin were synthesized by the carotid artery. Thus, histologic changes and rheologic effects occurring in vein grafts transposed to the arterial site do not affect prostacyclin production.

The effects of crystalloid potassium cardioplegic solution on arterialized canine vein grafts. Assessment of chronic prostacyclin production and histopathologic alterations

Efforts to improve myocardial preservation during aortocoronary bypass procedures have led to the perfusion of saphenous vein segments with potassium cardioplegic (KCP) solutions after completion of the distal anastomosis. Recent reports show that the procurement of veins leads to varying degrees of damage, particularly to the endothelial surface, as a result of the dissection itself, the hydrostatic pressure required to distend the veins in obtaining hemostasis and the composition of the solutions used to irrigate the harvested segments. The biologic activity of arterialized vein segments is largely unknown. We tested the hypothesis that the degree of venous injury inherent in vein harvesting may be compounded by perfusion with a potassium-rich solution, a known vascular irritant. The external jugular vein was removed from 18 dogs. Half of the vein was perfused with 300 ml of a KCP solution at 4 degrees C (40 mEq/l KCl, 10 ml sodium bicarbonate, pH 7.6, osmolarity 340 mosmol) and the other half with lactated Ringer's solution (LR). The treated vein was reversed and interposed into the excluded internal carotid circulation. A sham dissection was done on the opposite jugular vein. The veins were harvested after 6 weeks and assayed for spontaneous and arachidonate-stimulated (AS) prostacyclin activity as well as light microscopic analysis of morphologic changes. Spontaneous and AS production of prostacyclin did not differ significantly in the sham, LR and KCP groups: 1539 +/- 709 and 4166 +/- 1802, 1569 +/- 763 and 3767 +/- 2706, 1860 +/- 1233 and 3947 +/- 3347 pg/ml). Light microscopic analysis revealed an intense adventitial fibrotic reaction in the KCP group and the appearance of fibroblast-like cells in the outer layer of the vein wall. The intima was intact in all three groups. We conclude that intimal damage sustained during harvesting is repaired within 6 weeks, and there is no impairment to surface production of prostacyclin. The intense adventitial fibrotic reaction observed in the KCP-treated group has not been previously reported, and its significance remains unexplained.