Strategies to Manage Paraplegia Risk After Endovascular Stent Repair of Descending Thoracic Aortic Aneurysms

BACKGROUND

Paraplegia is a recognized complication after endovascular stent repair of descending thoracic aortic aneurysms. A management algorithm employing neurologic assessment, somatosensory evoked potential monitoring, arterial pressure augmentation, and cerebrospinal fluid drainage evolved to decrease the risk of postoperative paraplegia.

METHODS

Patients in thoracic aortic aneurysm stent trials from 1999 to 2004 were analyzed for paraplegic complications. Lower extremity strength was assessed after anesthesia and in the intensive care unit. A loss of lower extremity somatosensory evoked potential or lower extremity strength was treated emergently to maintain a mean arterial pressure 90 mmHg or greater and a cerebrospinal fluid pressure 10 mm Hg or less.

RESULTS

Seventy-five patients (male = 49, female = 26, age = 75 +/- 7.4 years) had descending thoracic aortic aneurysms repaired with endovascular stenting. Lumbar cerebrospinal fluid drainage (n = 23) and somatosensory evoked potential monitoring (n = 15) were performed selectively in patients with significant aneurysm extent or with prior abdominal aortic aneurysm repair (n = 17). Spinal cord ischemia occurred in 5 patients (6.6%); two had lower extremity somatosensory evoked potential loss after stent deployment and 4 developed delayed-onset paraplegia. Two had full recovery in response to arterial pressure augmentation alone. Two had full recovery and one had near-complete recovery in response to arterial pressure augmentation and cerebrospinal fluid drainage. Spinal cord ischemia was associated with retroperitoneal bleed (n = 1), prior abdominal aortic aneurysm repair (n = 2), iliac artery injury (n = 1), and atheroembolism (n = 1).

CONCLUSIONS

Early detection and intervention to augment spinal cord perfusion pressure was effective for decreasing the magnitude of injury or preventing permanent paraplegia from spinal cord ischemia after endovascular stent repair of descending thoracic aortic aneurysm. Routine somatosensory evoked potential monitoring, serial neurologic assessment, arterial pressure augmentation, and cerebrospinal fluid drainage may benefit patients at risk for paraplegia.

Major Clinical Outcomes in Adults Undergoing Thoracic Aortic Surgery Requiring Deep Hypothermic Circulatory Arrest: Quantification of Organ-Based Perioperative Outcome and Detection of Opportunities for Perioperative Intervention

OBJECTIVE

The purpose of this study was to describe clinical outcome after adult thoracic aortic surgery requiring standardized deep hypothermic circulatory arrest (DHCA), to determine mortality and length of stay, neurologic outcome, cardiorespiratory outcome, and hemostatic and renal outcome after DHCA.

DESIGN

Retrospective and observational.

SETTING

Cardiothoracic operating rooms and intensive care unit (ICU).

PARTICIPANTS

All adults requiring thoracic aortic repair with DHCA.

INTERVENTIONS

None. The study was observational.

MAIN RESULTS

The cohort size was 110. All patients received an antifibrinolytic. The mortality rate was 8.2%. The mean length of stay was 6.8 days (ICU) and 14.0 days (hospital). The incidence of stroke was 8.1% and postoperative delirium was 10.9%. The rate of postoperative atrial fibrillation was 43.6%; 19.1% required postoperative mechanical ventilation longer than 72 hours. Chest tube drainage was 931 mL for the first 24 hours. Postoperative dialysis was required in 1.8% of patients. Renal dysfunction occurred in 40% to 50% of patients, depending on the definition.

CONCLUSIONS

The protocol for DHCA at the authors' institution is associated with superior or equivalent perioperative outcomes to those reported in the literature. This study identified the need for further quantification of the clinical outcomes after DHCA in order to prioritize outcome-based hypothesis-driven prospective intervention in DHCA.

Bleeding and blood product utilization in adults undergoing elective aortic root replacement: the impact of antifibrinolytic exposure and aortic root prosthesis

A retrospective observational study was carried out to test the hypothesis that bleeding and blood component utilization are significantly associated with aortic root replacement (ARR). The aims of the study were as follows. (1) To determine antifibrinolytic exposure (AFE) in ARR; (2) To determine mediastinal drainage within the first 24 hours after ARR; (3) To determine blood component transfusion within the first 24 hours after ARR; (4) To determine whether AFE affects bleeding and blood component transfusion for ARR; and, (5) To determine whether type of aortic root prosthesis affects bleeding and/or blood component transfusion after ARR. All adults undergoing elective ARR from 1996-2001 at the Hospital of the University of Pennsylvania were included in the study. Cohort size was 61. Average age was 49.1 years. AFE was 52%: 23.0% aminocaproic acid, and 29% aprotinin. Mediastinal drainage averaged 384 ml for the first 24 hours. Transfusion in the first 24 hours averaged <1 unit red cells, <1 unit plasma, and <16-pack of platelets. Mediastinal drainage and blood component transfusion were not significantly related to AFE or type of surgical prosthesis. Based on these findings the hypothesis is rejected. The protocol for ARR at our institution is associated with excellent haemostatic outcome, regardless of AFE or type of aortic root prosthesis. Further clinical research in haemostatic outcome after thoracic aortic surgery should be directed at more extensive aortic procedures such as aortic arch repair with deep hypothermic circulatory arrest.

St. Jude Medical Toronto biologic aortic root prosthesis: Early FDA phase II IDE study results

BACKGROUND

Several biological aortic root replacement techniques have distinct advantages over mechanical composite root replacement including better valvular hemodynamic characteristics and the lack of need for anticoagulation. Current biological root replacement options lack proven long-term durability or are limited by technical or practical concerns. We report the early results from a phase II multicenter clinical trial of the porcine St. Jude Toronto Bioprosthesis with BiLinx (Toronto root).

METHODS

176 Toronto roots were implanted as total aortic root replacement from August 2001 through August 2003. Concomitant cardiac procedures including coronary artery bypass grafting (31%) and ascending aortic replacement (55%) were performed in 74%. Patients were followed clinically and were examined with an echocardiogram at discharge, 6 months, 12 months, and yearly thereafter. Root sizes implanted included 29 mm in 38%, 27 mm in 30%, 25 mm in 20%, 23 mm in 10%, and 21 mm in 2.2%.

RESULTS

There are 205 patient years of follow-up through October 2003. Operative mortality was 3.9% (none were valve related) and late mortality was 4%. Operative stroke rate was 1.1% and late stroke rate was 0.6%. Endocarditis developed in 1 patient. Freedom from aortic regurgitation is to date 100% at discharge, 6 months, and 1 year postimplant. Reoperation of the aortic valve/root was not required in any patient. Six-month mean transvalvular gradients for 21-29 mm valves were 12.8, 8.8, 5.3, 4.9, and 4.7 mm Hg, respectively.

CONCLUSIONS

Aortic root replacement with the Toronto root is safe and provides superb transvalvular hemodynamics with freedom from anticoagulation. The Toronto root seems widely applicable for all types of aortic root pathology and these early data offer very encouraging results. Long-term follow-up is required.

Initial experience with the Toronto Root bioprosthesis

BACKGROUND AND AIM OF THE STUDY

The study aim was to assess the safety and efficacy of the Toronto Root bioprosthesis for aortic root or valve replacement during the early postoperative stages.

METHODS

Between November 2000 and December 2002, the Toronto Root was implanted in 191 patients in 17 institutions. The patients' mean age was 65 years (range: 25 to 87 years) and 70% were males. The bioprosthesis was implanted as a full aortic root in 76% of patients, as a root inclusion in 9%, and in the subcoronary position in 15%. The sizes used in decreasing frequency were 27, 29, 25, 23 and 21 mm. Coronary artery bypass was performed in 25% of patients. Echocardiography was performed before hospital discharge and at six months postoperatively. Serum aluminum levels were monitored pre- and postoperatively as this metal is used in anticalcification treatment of the arterial wall of the porcine root. For the purpose of this study, follow up was closed at six months in all patients, and was complete.

RESULTS

Eight patients died, though none of the deaths was valve-related. Two patients required reoperation because of technical errors during implantation. Two patients developed endocarditis, one patient required surgical intervention, and two patients suffered cerebral transient ischemic attacks. All survivors experienced symptomatic improvement, and 97% were in NYHA functional classes I and II at six months postoperatively. Blood levels of aluminum were unchanged at follow up. The mean effective orifice area of all valves studied was 2.0 +/- 0.8 cm2, and the mean systolic gradient 7.0 +/- 3.9 mmHg at six months postoperatively. No patient had more than trace aortic insufficiency.

CONCLUSION

Early experience with the Toronto Root bioprosthesis has shown it to be a safe and effective valve for aortic valve or aortic root replacement, with excellent hemodynamic characteristics, a low transvalvular gradient and a large effective orifice area.

Perioperative changes in cerebral blood flow after cardiac surgery: influence of anemia and aging

BACKGROUND

Stroke occurs in 2% to 5% and cognitive dysfunction occurs acutely in 60% to 80% of patients early after cardiac surgery. Both may have long-term consequences. Research into mechanisms behind these sequelae has been focused intraoperatively, although there is little reason to believe that injury is limited to this period. Aging prominently increases the incidence of these sequelae. Anemia with cardiac surgery is acute and severe, should cause an increase in cerebral blood flow (CBF), and may impact stroke and cognitive function in this setting. To better understand changes in perioperative CBF physiology we have measured changes in CBF and the influence of anemia and aging on these changes.

METHODS

Cerebral blood flow was measured using the noninvasive continuous arterial spin labeling perfusion magnetic resonance imaging method. Cerebral blood flow, mean arterial pressure, hemoglobin, hemoglobin oxygen saturation, and cardiopulmonary bypass time were recorded in 12 subjects before and 6 +/- 2 days after cardiac surgery.

RESULTS

Cerebral blood flow increased from 44.6 +/- 15.6 mL100 g(-1)min(-1) to 64.4 +/- 20.1 mL100 g(-1)min(-1) after cardiac surgery, or 49.1% +/- 26.7%, (p < 0.0001). The absolute change in CBF (DeltaCBF) was predicted by the following regression model: DeltaCBF = -55 + 0.64(Age) + 0.53(CBF(Pre)) -3.3(DeltaHgb); R(2) = 0.81; p = 0.003, where CBF(Pre) is the baseline preoperative CBF and DeltaHgb is the change in hemoglobin from preoperative to postoperative periods.

CONCLUSIONS

Cerebral blood flow increases after cardiac surgery, and anemia appears to be an important cause. Age appears also to be an important covariate, with advancing age further increasing the magnitude of this hyperemia. The interrelationship of aging and anemia, in determining perioperative changes in CBF, and potentially cerebral oxygenation, may have important implications for the understanding of perioperative stroke and cognitive dysfunction after cardiac surgery.

Thoracoabdominal aortic aneurysm repair after prior aortic surgery

PURPOSE

The purpose of this study was to determine whether the morbidity and mortality of surgery for thoracoabdominal aortic aneurysm (TAAA) in patients with prior aortic surgery are increased.

METHODS

The results for all patients undergoing operation for TAAA at a single institution were reviewed.

RESULTS

Over a 10-year interval, 279 patients (136 women and 143 men) underwent aortic replacement for TAAA. The mean patient age was 68 years (range, 34-90). The extent of aortic replacement was relatively evenly distributed: type I (91), type II (54), type III (78), or type IV (56). Of these 279 patients, 76 (27%) had undergone prior aortic surgery. Prior infrarenal AAA was the most common prior procedure (56, 20%). Reoperation for prior failed TAAA repair was performed in 20 (7%) patients. A history of Marfan syndrome was highly associated with the need for remedial TAAA procedures (P <.0001). Overall 30-day mortality was 11.4% (32). Mortality was independent of prior aortic surgery (P =.98), prior AAA (P =.84), prior TAAA (P =.61), and gender (P =.18). Postoperative complications were seen in 67 (24%) patients and were more likely in patients who had undergone prior AAA surgery (P =.008). TAAA repair in patients with recurrent TAAA was not associated with higher morbidity (P =.33). Paraplegia (10) occurred in type I (3), type II (2), and type III (5) aneurysms but not in type IV (0), and its development was associated with higher mortality (P =.01). Prior aortic surgery was not found to be predictive of paraplegia (P =.90), although 30% of patients who developed paraplegia had a history of prior AAA repair.

CONCLUSIONS

Aortic reoperation for TAAA is required in a significant number of patients, particularly those with Marfan syndrome. Therefore, ongoing surveillance of the residual aorta is mandatory. Postoperative complications are more likely to occur in patients after prior infrarenal aortic replacement, but mortality is not significantly increased. Special technical considerations exist for remedial procedures after failed TAAA repair to provide protection for the spinal cord, kidneys, and viscera. Patients with failed TAAA procedures or progression of aneurysmal extent should be offered reoperation when indicated.

Safety of lumbar drains in thoracic aortic operations performed with extracorporeal circulation

BACKGROUND

The safety of cerebrospinal fluid (CSF) drainage in thoracic aortic surgery using extracorporeal circulation (ECC) with systemic heparinization has not been established.

METHODS

Four hundred thirty-two patients had descending thoracic or thoracoabdominal aortic repair between 1993 and 2002. One hundred sixty-two of those patients (age range, 67 +/- 13 years) had repairs performed with ECC, systemic anticoagulation, and lumbar CSF drainage. Repairs performed without CSF drainage, without ECC, or by stent graft (n = 53) were excluded. The CSF catheters were inserted at L3 to L5. Cerebrospinal fluid was drained to maintain pressures of 10 to 12 mm Hg. In the absence of neurologic deficit or coagulopathy, the catheters were capped at 24 hours and removed at 48 hours. Cerebrospinal fluid drainage was continued beyond 24 hours for delayed onset paraparesis.

RESULTS

Cerebrospinal fluid drains were used in 135 thoracoabdominal aortic aneurysms (extent I, n = 63; extent II, n = 25; extent III, n = 39; extent IV, n = 8) and 27 descending thoracic aortic repairs (aneurysm, n = 24; traumatic aortic injury, n = 2; aortic coarctation, n = 1). Partial left heart bypass was used in 132 patients, full cardiopulmonary bypass without deep hypothermic circulatory arrest in 5, and cardiopulmonary bypass with adjunctive deep hypothermic circulatory arrest in 25. Time between catheter insertion and anticoagulation was 153 +/- 60 minutes. Heparin achieved an average maximum activated clotting time of 528 +/- 192 seconds. Average ECC time was 114 +/- 77 minutes. Average deep hypothermic circulatory arrest time was 40 +/- 12 minutes. Mortality was 14.1% (23 of 162), and permanent paraplegia was 4.9% (8 of 162). No epidural or spinal hematoma was observed. Six (3.7%) patients had catheter-related complications (temporary abducens nerve palsy [n = 1]; retained catheter fragments [n = 2]; retained catheter fragment and meningitis [n = 1]; isolated meningitis [n = 1]; and spinal headache [n = 1]).

CONCLUSIONS

The CSF drainage in thoracic aortic surgery using ECC with full anticoagulation did not result in hemorrhagic complications. The permanent paraplegia rate in this complex patient population consisting of combined distal arch, thoracoabdominal aortic procedures were low, and lumbar CSF catheter-related complications had no permanent sequelae.

Prospective randomized study of a protein-based tissue adhesive used as a hemostatic and structural adjunct in cardiac and vascular anastomotic repair procedures

BACKGROUND

The purpose of this study was to determine whether adjunctive use of the bovine serum albumin and glutaraldehyde tissue adhesive BioGlue (BioGlue Surgical Adhesive; CryoLife, Inc) could reduce the rate of anastomotic bleeding in patients undergoing cardiac and vascular repair procedures when compared with a standard repair control. This was a prospective multicenter, randomized, controlled clinical trial conducted in accordance with the IRB at each participating institution.

STUDY DESIGN

A total of 151 patients consented to participation and were randomly assigned to standard repair plus BioGlue (n = 76) or standard repair alone (n = 75). These two groups were statistically homogeneous for age, gender, race, procedure, and number of anastomoses. Patients underwent cardiac procedures (n = 49), aortic procedures (n = 105), or peripheral vascular procedures (n = 48).

RESULTS

Anastomotic bleeding was significantly reduced in the BioGlue group (18.8% of anastomoses) compared with the control group (42.9% of anastomoses, p < 0.001). Pledget use was reduced in the BioGlue group (26.2%) compared with the control group (35.9%, p = 0.047). Days in the ICU and total days in the hospital were slightly higher in the control group. Adverse event profiles were equivalent between the two groups except for occurrence of neurological defects, which were threefold less in the BioGlue group (p = 0.009).

CONCLUSIONS

This study demonstrates that using BioGlue as an adjunct to standard repair methods is safe and significantly reduces the occurrence of intraoperative anastomotic site bleeding in cardiac and vascular repair patients. Using BioGlue along suture lines reinforces anastomoses, thus minimizing pledget use.

Advances in the treatment of acute type A dissection: an integrated approach

BACKGROUND

Acute type A dissections require surgery to prevent death from proximal aortic rupture or malperfusion. Most series over the past decade have reported a death rate in the range of 15% to 30%. The objective of this study is to examine the effect of an integrated surgical approach on the treatment of acute type A dissections.

METHODS

From January 1994 to April 2002, 163 consecutive patients underwent repair of acute type A dissection. All had an integrated operative management as follows: intraoperative transesophageal echocardiography; hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion to replace the aortic arch; HCA established after 3 minutes of electroencephalographic silence in neuromonitored patients (60%) or after 45 minutes of cooling in patients who were not neuromonitored (40%); reinforcement of the residual arch tissue with a Teflon felt "neo-media;" cannulation of the arch graft to reestablish cardiopulmonary bypass at the completion of HCA (antegrade graft perfusion); and remodeling of the sinus of Valsalva segments with Teflon felt "neo-media" and aortic valve resuspension or replacement with a biological or mechanical valved conduit. When HCA times were greater than 50 minutes, antegrade cerebral perfusion is used. Since Februay 1999, BioGlue has been used as an anastomotic adjunct in the repair of type A dissections.

RESULTS

Mean age was 62 +/- 14 years, with 68% men and 15% with previous cardiac surgery. Seven percent of patients presented with a preoperative neurologic deficit, and 3% developed a new cerebrovascular accident after dissection repair. The in-hospital death rate was 9.8%. Excluding the patients with preoperative strokes (7%) and those with postoperative stroke (3%), the in-hospital death rate was 6.6%. In 6 patients, prompt changes in circulatory management consisting of switching cannulation sites or cross-clamp release with direct temporary aortic arch fenestration occurred when there were sudden changes in electroencephalogram during cooling.

CONCLUSIONS

A standardized approach to the treatment of acute type A dissections has improved outcomes. Our 55% mortality in patients with preoperative cerebral vascular accident (CVA) suggests that this group may be candidates for medical or delayed surgical treatment. Conversely, our 6.6% mortality rate for neurologically intact patients warrants aggressive and expeditious surgical intervention.

Cardiopulmonary bypass for bilateral sequential lung transplantation in patients with chronic obstructive pulmonary disease without adverse effect on lung function or clinical outcome

OBJECTIVE

The use of cardiopulmonary bypass in lung transplantation remains controversial. Previous studies have concluded that cardiopulmonary bypass is deleterious, but these studies were confounded by the inclusion of patients with different diagnoses undergoing single- and double-lung transplantation with elective or emergency use of bypass. The goal of this study was to determine whether cardiopulmonary bypass has deleterious effects on lung function or clinical outcome by analyzing the cases of patients with a single disease entity and elective use of bypass for bilateral sequential lung transplantation.

METHODS

A retrospective review of 50 patients with chronic obstructive pulmonary disease who underwent bilateral sequential lung transplantation was performed. Fourteen patients who underwent elective cardiopulmonary bypass for 218.3 +/- 75.4 minutes were compared to 36 control patients.

RESULTS

After the operation, the bypass and nonbypass groups were not significantly different with respect to median duration of mechanical ventilation (1 day vs 1 day, P =.76), median stay in the intensive care unit (4 days vs 4 days, P =.44), median hospital stay (15.5 days vs 16 days, P =.74), mean increase in serum creatinine level (1.4 +/- 1.9 mg/dL vs 0.9 +/- 1.0 mg/dL, P =.33), and mean ratio of Pao(2) to fraction of inspired oxygen at 1 hour (376.6 +/- 123 vs 357.0 +/- 218, P =.75), at 24 hours (309.9 +/- 92 vs 350.6 +/- 122, P =.26), and at 48 hours (335.0 +/- 144 vs 316.2 +/- 120, P =.64). Late outcome markers compared between the bypass and nonbypass groups were the following: 1-year percentage predicted forced expiratory volume in 1 second (76.1% +/- 17.0% vs 85.3% +/- 21.7%, P =.24), 30-day mortality (7.1% vs 8.3%, P >.999), 1-year survival (85.7% vs 80.1%, P =.66), 3-year survival (64.3% vs 58.3%, P =.70), and the prevalence of bronchiolitis obliterans syndrome (0% vs 36.1%, P =.01).

CONCLUSION

Cardiopulmonary bypass appears to have no deleterious effect on early lung function or clinical outcome. We hope that this pilot study removes some of the unwarranted fear of the use of bypass in lung transplantation for chronic obstructive pulmonary disease.

Interventions for reversing delayed-onset postoperative paraplegia after thoracic aortic reconstruction

BACKGROUND

Delayed postoperative paraplegia is a recognized complication of thoracic (TAA) or thoracoabdominal aortic aneurysm (TAAA) repair. The purpose of this study was to evaluate the effectiveness of interventions to treat delayed-onset paraplegia.

METHODS

Between January 1, 2000 and August 31, 2001, 99 patients underwent surgical repair of TAA, Crawford type I, II, or III TAAA. Standard intraoperative management included distal aortic perfusion and cerebrospinal fluid (CSF) drainage unless contraindicated. Therapeutic interventions to treat delayed paraplegia included lumbar CSF drainage and vasopressor therapy.

RESULTS

Three of the 99 patients had paraplegia upon awakening. Delayed-onset paraplegia occurred in 8 patients, 2 of whom had recurrent episodes. In those 8 patients, the initial episode occurred at a median of 21.6 hours (range 6.4 to 110.0 hours) after surgery and the second episode averaged 176 hours after surgery. At the onset of paraplegia, the average mean arterial pressure was 74 mm Hg and CSF pressure was 14 mm Hg. Three of the 8 patients had a functioning CSF catheter at the onset and the other 5 patients had catheters subsequently placed. Therapeutic interventions increased blood pressure to a mean arterial pressure of 95 mm Hg and decreased CSF pressure to 10 mm Hg. Five of the 8 patients with delayed-onset paraplegia made a full neurologic recovery and 3 had partial recovery.

CONCLUSIONS

Patients with delayed-onset paraplegia had an increased chance of recovery as compared with those patients in whom paraplegia was diagnosed upon emergence from anesthesia. Acute interventions directed to increase spinal cord perfusion by increasing systemic blood pressure and decreasing CSF pressure were effective for the reversal of delayed onset of paraplegia after TAA or TAAA repair, resulting in an overall 3% incidence of permanent paraplegia and 3% incidence of residual paraparesis.

Homograft aortic root replacement during pregnancy

Operative cardiac interventions have been performed on pregnant women with varying degrees of success since the late 1950s. Currently, reported maternal mortality for cardiac operations is similar to the mortality rate for nonpregnant female patients. However, fetal mortality remains high, at approximately 20%. Aortic root replacement with an aortic homograft in a 34-year-old pregnant woman with bacterial endocarditis at 18 weeks gestation is presented. Fetal echocardiography during and after bypass was employed.

CD3 monitoring of antithymocyte globulin therapy in thoracic organ transplantation

BACKGROUND

Antithymocyte globulin is frequently used as a component of induction therapy in thoracic organ transplantation. This study evaluates the utility of monitoring peripheral CD3 lymphocytes to rationally adjust antithymocyte globulin therapy in this patient population.

METHODS

A total of 17 heart and 19 lung transplant recipients received antithymocyte globulin (ATGAM or thymoglobulin) as induction therapy or to treat steroid-resistant acute or chronic rejection. Absolute CD3 counts were maintained between 50 and 100 cells/microl.

RESULTS

With CD3 monitoring, the doses of antithymocyte globulin were reduced from 10-15 mg/kg to 1-5 mg/kg during the course of therapy. The total amount of antithymocyte globulin given to each CD3 monitored patient was reduced by 48%. Dose reduction did not alter the number of acute rejection or infectious episodes, and hematological side effects were infrequent.

CONCLUSION

CD3 monitoring of antithymocyte globulin therapy in thoracic organ recipients reduced the amount of drug received by each patient, while maintaining CD3 counts less than 100 cells/microl.

Effects of acute hypoxemia/ischemia on EEG and evoked responses at normothermia and hypothermia in humans

BACKGROUND

Hypothermia is used clinically to prevent neurologic injury but the degree of protection which it affords at various levels of the nervous system in humans is difficult to establish.

MATERIAL/METHODS

The temporal changes in EEG amplitude and somatosensory evoked potential (SEP) amplitudes in a patient experiencing acute normothermic hypoxemia, a patient experiencing acute circulatory arrest at moderate hypothermia and a collection of patients undergoing deep hypothermic circulatory arrest were analyzed to determine the rate at which changes occur during acute lack of oxygen delivery at various temperatures.

RESULTS

In each case, it was found that more rostrally generated potentials disappeared more quickly than more peripheral potentials. All potentials decayed more slowly during acute normothermic hypoxemia than during circulatory arrest. During circulatory arrest at 14.4 degrees C, the amplitude of the Erb's point, N13 and N18 potentials in the SEP took 5 times longer to drop to 50% of their value at the onset of ischemia than with circulatory arrest at 30.9 degrees C.

CONCLUSIONS

The longer times to disappearance of the SEP potentials during deep hypothermia compared to moderate hypothermia was consistent with the predicted 3.5-6.5 fold reduction in metabolic activity at deep hypothermia compared to moderate hypothermia. The prolonged time to disappearance of the SEP during normothermic hypoxemia demonstrates that even with reduced oxygen delivery the continued delivery of metabolic substrate can be critical to neural function.

Bronchogenic carcinoma complicating lung transplantation

BACKGROUND

Malignancy is a well-recognized complication of solid-organ transplantation. Although a variety of malignancies have been reported in lung transplant recipients, a paucity of information exists regarding the incidence and clinical course of bronchogenic carcinoma in this patient population.

METHODS

We conducted a retrospective cohort study of our lung transplant experience at the University of Pennsylvania.

RESULTS

We identified 6 patients with bronchogenic carcinoma detected at the time of, or developing after, transplantation. The incidence of bronchogenic carcinoma was 2.4%. All patients with lung cancer had a history of smoking, with an average of 79 +/- 39 pack-years. A total of 5 patients had chronic obstructive pulmonary disease, and 1 had idiopathic pulmonary fibrosis. Lung cancers were all of non-small-cell histology and first developed in native lungs. Three patients had bronchogenic carcinoma at the time of surgery. The remaining 3 patients were diagnosed between 280 and 1,982 days post-transplantation. Of the 6 patients, 4 presented with a rapid course suggestive of an infectious process. The 1- and 2-year survival rates after diagnosis were 33% and 17%, respectively.

CONCLUSION

Lung transplant recipients are at risk for harboring or developing bronchogenic carcinoma in their native lungs. Rapid progression to locally advanced or metastatic disease commonly occurs, at times mimicking an infection. Bronchogenic carcinoma should be considered in the differential diagnosis of pleuroparenchymal processes involving the native lung.

Characteristics and outcomes of patients with sarcoidosis listed for lung transplantation

STUDY OBJECTIVES

To characterize the course of patients with advanced sarcoidosis who have been listed for lung transplantation and to identify prognostic factors for death while they are on the waiting list.

DESIGN

Retrospective cohort study.

SETTING

Tertiary-care university hospital.

PATIENTS

Forty-three patients with sarcoidosis who have been listed for lung transplantation at the University of Pennsylvania Medical Center.

METHODS

A multivariable explanatory analysis using a Cox proportional hazards model was performed to determine risk factors that are independently associated with mortality while patients await transplantation.

RESULTS

Twenty-three of the 43 patients (53%) died while awaiting transplantation. The survival rate of listed patients (as determined by the Kaplan-Meier method) was 66% at 1 year, 40% at 2 years, and 31% at 3 years. In a univariate analysis, the following factors were significantly associated with death on the waiting list: PaO(2) < or = 60 mm Hg (relative risk [RR], 3.4; 95% confidence interval [CI], 1.2 to 9.3); mean pulmonary artery pressure > or = 35 mm Hg (RR, 3.2; 95% CI, 1.1 to 9.5); cardiac index < or = 2 L/min/m(2) (RR, 2.8; 95% CI, 1.2 to 6.6), and right atrial pressure (RAP) > or = 15 mm Hg (RR, 7.6; 95% CI, 3.0 to 19.3). Multivariable analysis revealed that RAP > or = 15 mm Hg was the only independent prognostic variable (RR, 5.2; 95% CI, 1.6 to 16.7; p = 0.006). Twelve patients underwent lung transplantation. Survival after transplantation determined by the Kaplan-Meier method was 62% at both 1 and 2 years, and 50% at 3 years.

CONCLUSIONS

Patients with advanced sarcoidosis awaiting lung transplantation have a high mortality rate with a median survival of < 2 years. Mortality is most closely linked to elevated RAP. While earlier referral may diminish the mortality rate of patients on the waiting list for transplantation, further improvements in posttransplantation outcomes will be necessary to ensure that this procedure truly bestows a survival benefit.

New paradigms and improved results for the surgical treatment of acute type A dissection

OBJECTIVE

To examine the effect of an integrated surgical approach to the treatment of acute type A dissections.

SUMMARY BACKGROUND DATA

Acute type A dissection requires surgery to prevent death from proximal aortic rupture or malperfusion. Most series of the past decade have reported a death rate in the range of 15% to 30%.

METHODS

From January 1994 to March 2001, 104 consecutive patients underwent repair of acute type A dissection. All had an integrated operative management as follows: intraoperative transesophageal echocardiography; hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion (RCP) to replace the aortic arch; HCA established after 5 minutes of electroencephalographic (EEG) silence in neuromonitored patients (66%) or after 45 minutes of cooling in patients who were not neuromonitored (34%); reinforcement of the residual arch tissue with a Teflon felt "neo-media"; cannulation of the arch graft to reestablish cardiopulmonary bypass at the completion of HCA (antegrade graft perfusion); and remodeling of the sinus of Valsalva segments with Teflon felt "neo-media" and aortic valve resuspension (78%) or replacement with a biologic or mechanical valved conduit (22%).

RESULTS

Mean age was 59 +/- 15 (range 22-86) years, with 71% men and 13% redo sternotomy after a previous cardiac procedure. Mean cardiopulmonary bypass time was 196 +/- 50 minutes. Mean HCA with RCP time was 42 +/- 12 minutes (range 19-84). Mean cardiac ischemic time was 140 +/- 45 minutes. Eleven percent of patients presented with a preoperative neurologic deficit, and 5% developed a new cerebrovascular accident after dissection repair. The in-hospital death rate was 9%. Excluding the patients who presented neurologically unresponsive or with ongoing cardiopulmonary resuscitation (n = 5), the death rate was 4%. In six patients adverse cerebral outcomes were potentially avoided when immediate surgical fenestration was prompted by a sudden change in the EEG during cooling. Forty-five percent of neuromonitored patients required greater than 30 minutes to achieve EEG silence.

CONCLUSION

The authors have shown that the surgical integration of sinus segment repair or aortic root replacement, the use of EEG monitoring, partial or total arch replacement using RCP, routine antegrade graft perfusion, and the uniform use of transesophageal echocardiography substantially decrease the death and complication rates of acute type A dissection repair.

Deep hypothermic circulatory arrest: II. Changes in electroencephalogram and evoked potentials during rewarming

BACKGROUND

Electrophysiologic studies during rewarming after deep hypothermic circulatory arrest probe the state of the brain during this critical period and may provide insight into the neurological effects of circulatory arrest and the neurologic outcome.

METHODS

Electroencephalogram (EEG) and evoked potentials were monitored during rewarming in 109 patients undergoing aortic surgery with hypothermic circulatory arrest.

RESULTS

The sequence of neurophysiologic events during rewarming did not mirror the events during cooling. The evoked potentials recovered first followed by EEG burst-suppression and then continuous EEG. The time to recovery of the evoked potentials N20-P22 complex was significantly correlated with the time of circulatory arrest even in patients without postoperative neurologic deficits (r = 0.37, (p = 0.002). The nasopharyngeal temperatures at which continuous EEG activity and the N20-P22 complex returned were strongly correlated (r = 0.44, p = 0.0002; r = 0.41, p = 0.00003) with postoperative neurologic impairment. Specifically, the relative risk for postoperative neurologic impairment increased by a factor of 1.56 (95% CI 1.1 to 2.2) for every degree increase in temperature at which the EEG first became continuous.

CONCLUSIONS

No trend toward shortened recovery times or improved neurologic outcome was noted with lower temperatures at circulatory arrest, indicating that the process of cooling to electrocerebral silence produced a relatively uniform degree of cerebral protection, independent of the actual nasopharyngeal temperature.

Deep hypothermic circulatory arrest: I. Effects of cooling on electroencephalogram and evoked potentials

BACKGROUND

Deep hypothermia is an important cerebral protectant and is critical in procedures requiring circulatory arrest. The purpose of this study was to determine the factors that influence the neurophysiologic changes during cooling before circulatory arrest, in particular the occurrence of electrocerebral silence.

METHODS

In 109 patients undergoing hypothermic circulatory arrest with neurophysiologic monitoring, five electrophysiologic events were selected for detailed study.

RESULTS

The mean nasopharyngeal temperature when periodic complexes appeared in the electroencephalogram after cooling was 29.6 degrees C +/- 3 degrees C, electroencephalogram burst-suppression appeared at 24.4 degrees C +/- 4 degrees C, and electrocerebral silence appeared at 17.8 degrees C +/- 4 degrees C. The N20-P22 complex of the somatosensory evoked response disappeared at 21.4 degrees C +/- 4 degrees C, and the somatosensory evoked response N13 wave disappeared at 17.3 degrees C +/- 4 degrees C. The temperatures of these various events were not significantly affected by any patient-specific or surgical variables, although the time to cool to electrocerebral silence was prolonged by high hemoglobin concentrations, low arterial partial pressure of carbon dioxide, and by slow cooling rates. Only 60% of patients demonstrated electrocerebral silence by either a nasopharyngeal temperature of 18 degrees C or a cooling time of 30 minutes.

CONCLUSIONS

With the high degree of interpatient variability in these neurophysiologic measures, the only absolute predictors of electrocerebral silence were nasopharyngeal temperature below 12.5 degrees C and cooling longer than 50 minutes.