Period Of Aortic Cross-clamping Research Articles

Reply to Toumpoulis

We appreciate the comments of Ioannis K. Toumpoulis about our paper concerning the use of immediate ischemic preconditioning based on somatosensory evoked potentials to prevent spinal cord injury [1]. In that study, it was shown that ischemic tolerance could be immediately achieved in the spinal cord against a clinically relevant ischemic insult, since ischemic preconditioning was based on the proper selection of induction times and intervals in dogs. This observation was obtained without significant differences between the groups with regard to proximal and distal aortic pressures at baseline, during the aortic crossclamping and at the reperfusion period, as mentioned. During the aortic cross-clamping period, low doses of sodium nitroprusside were used to reduce the arterial blood pressure, explaining the described results. Nevertheless, no important hypotension was observed during the reperfusion interval in all the experiments of the three groups and it was not possible to detect any correlation between neurologic or histopathologic outcome with differences in arterial pressure during reperfusion or aortic cross-clamping time intervals. We agree with Toumpoulis and coworkers [2,3] that hypotension episodes during the reperfusion period may influence the neurologic outcome in these experimental models of spinal cord ischemia after aortic cross-clamping. However, this finding does not appear to have influenced our data.

Correlations of Cerebrospinal Fluid Pressure with Hemodynamic Parameters During Thoracoabdominal Aortic Aneurysm Repair

Central venous pressure (CVP) has long been thought to correlate with cerebrospinal fluid (CSF) pressure during thoracoabdominal aortic aneurysm repair. We examined hemodynamic factors during thoracoabdominal aortic aneurysm surgery to determine their relationship with CSF pressure and aortic cross-clamping. Hemodynamic parameters and CSF pressure were measured in 124 patients at six different stages during repair of descending thoracic or thoracoabdominal aortic aneurysms: skin incision, left lung collapse, pump on, aortic clamp on, aortic clamp off, and pump off. Stepwise multiple regression analysis was used for statistical analysis. CVP was a weak predictor for CSF pressure at the beginning of surgery and when the pump was initiated. At the onset of left lung collapse, cardiac output correlated with CSF pressure. There were no predictors during aortic cross-clamping. Model r2 values were low, ranging 0.03-0.15. We found no hemodynamic predictors of CSF pressure throughout the period of aortic cross-clamping during descending thoracic or thoracoabdominal aortic aneurysm surgery. Model r2 values were low, indicating generally poor prediction of CSF pressure.

Case 3—2005 Risk and Benefits of Cerebrospinal Fluid Drainage During Thoracoabdominal Aortic Aneurysm Surgery

Repair of descending thoracic and thoracoabdominal aortic aneurysms (TAAAs) is associated with a substantial risk of perioperative spinal cord ischemia that may or may not lead to permanent postoperative paralysis. Several techniques that aim to increase the ischemia tolerance time of the spinal cord during the period of aortic cross-clamping have been described in the literature. 1 Afifi S. Cerebrospinal fluid drainage protects the spinal cord during thoracoabdominal aortic reconstruction surgery. J Cardiothorac Vasc Anesth. 2002; 16: 643-649 Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar Hypothermia, left heart bypass, various shunts, myriad drugs, and cerebrospinal fluid (CSF) drainage have all been used alone or in combination to potentially improve neurologic outcome after surgery. CSF drainage and distal aortic perfusion have been shown to lower the incidence of neurologic complications after repair of type I and type II TAAAs. 2 Coselli J. Cerebrospinal fluid drainage reduces paraplegia after thoracoabdominal aortic aneurysm repair Results of a randomized clinical trial. J Vasc Surg. 2002; 35: 631-639 Abstract Full Text Full Text PDF PubMed Scopus (527) Google Scholar Distal aortic perfusion increases distal aortic pressure, and CSF drainage decreases CSF pressure. These techniques potentially lead to an augmentation of spinal cord perfusion pressure during the period of aortic cross-clamping. However, CSF drainage can be associated with potentially serious complications, including fracture of the catheter during removal, catheter-associated meningitis, and/or temporary abducens nerve palsy, among others. 3 Cheung A.T. Pochettino A. Guvakov D.V. et al. Safety of lumbar drains in thoracic aortic operations performed with extracorporeal circulation. Ann Thorac Surg. 2003; 76: 1190-1197 Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar Also, epidural hematoma at the catheter insertion site can complicate the clinical assessment of postoperative spinal ischemic injury. 4 Weaver K. Weisman D.B. Farber M. et al. Complications of lumbar drainage after thoracoabdominal aortic aneurysm repair. J Vasc Surg. 2001; 34: 623-627 Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar Intracranial subdural hematomas, with excessive CSF drainage, have also been reported and are associated with significant morbidity and mortality. 5 Dardik A. Perler B.A. Roseborough G.S. et al. Subdural hematoma after thoracoabdominal aortic aneurysm repair An underreported complication of spinal fluid drainage?. J Vasc Surg. 2002; 36: 47-50 Abstract Full Text PDF PubMed Scopus (122) Google Scholar Subsequently, some authors have challenged the efficacy of CSF drainage and question the acceptable risk:benefit ratio of the technique. 6 Wallace L. Cerebrospinal fluid drainage does not protect the spinal cord during thoracoabdominal aortic reconstruction surgery. J Cardiothorac Vasc Anesth. 2002; 16: 650-652 Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar , 7 Ling E. Arellano R. Systematic overview of the evidence supporting the use of cerebrospinal fluid drainage in thoracoabdominal aneurysm surgery for prevention of paraplegia. Anesthesiology. 2000; 93: 1115-1122 Crossref PubMed Scopus (48) Google Scholar

Intraoperative regional myocardial acidosis and reduction in long-term survival after cardiac surgery

Regional myocardial acidosis, as measured with tissue pH electrodes during cardiac surgery, has been shown to be reflective of regional myocardial ischemia. This study examined the relationship between intraoperative regional myocardial acidosis and long-term survival of patients undergoing cardiac surgery with cardiopulmonary bypass. A total of 496 adult patients who underwent valve replacement, coronary artery revascularization, or both with intraoperative myocardial pH monitoring in the anterior and posterior left ventricular walls were followed up for 3 to 17 years (average 10.2 +/- 4.9 years) for all cause mortality. Regional myocardial acidosis in each patient was defined by the lower of the anterior and posterior wall pH values. A bivariate automatic interaction detection analysis identified three significant regional myocardial acidosis thresholds that affected long-term mortality: pH 37C less than 6.63 before aortic crossclamping, integrated mean pH 37C less than 6.34 during the period of aortic crossclamping, and pH 37C less than 6.73 at discontinuation of cardiopulmonary bypass. Cox proportional hazard regression analysis identified each of these thresholds to be independently determinant of survival, with pH 37C during aortic crossclamping having the highest risk ratio (risk ratio 2.15, 95% confidence interval 1.37-3.37). Raising pH 37C from lower than threshold before aortic crossclamping to higher than threshold during clamping increased the median survival by 40.2%. In adult patients undergoing cardiac surgery with cardiopulmonary bypass, regional myocardial ischemic acidosis before aortic crossclamping, during aortic crossclamping, and at discontinuation of cardiopulmonary bypass are independently associated with reduced long-term postoperative survival. Reversing or avoiding myocardial acidosis during cardiac surgery improves long-term patient survival.

Effect of perfusionist technique on cerebral embolization during cardiopulmonary bypass

To determine the association between high-intensity transient signals (HITS) and perfusionist interventions, purging techniques, pump flows and venous reservoir blood volume levels during cardiopulmonary bypass. Transcranial Doppler was used to detect HITS in the middle cerebral artery during the period of aortic crossclamping in patients undergoing coronary artery bypass grafting. Perfusionist-related interventions were recorded and included blood sampling (including the number of times that the oxygenator sampling manifold was purged), drug bolus injections and infusions (vasopressors, crystalloid and mannitol). Pump flows and venous reservoir volume levels were also documented. There were 534 interventions in 90 patients [median number of interventions per patient: 6 (quartiles: 4, 8)]. The median total HITS count from all interventions was 17 (5, 37). This represented 38% of the total HITS counts during aortic crossclamping. Factors contributing to differences in the HITS count included type of intervention (p <0.0001) and perfusionist (p =0.0012). Blood sampling (p<0.001) and drug bolus injections (p=0.06) had higher HITS counts per patient than infusions. Repetitive purging significantly increased HITS counts (r=0.74; p <0.001). Purging perfusionists (purging: 1-10 times) had higher HITS counts per patient [5 HITS (1, 15) than nonpurgers [0 HITS (0, 1) p <0.0001]. HITS counts were significantly correlated with reservoir volumes (r= -0.20, p=0.017) and pump flow rates (r=0.21, p =0.008). Reservoir volume levels < or =800 mL were associated with higher HITS counts per intervention [11 HITS (2, 27)] during blood sampling compared with higher volume levels [3 HITS (1, 10), p =0.001]. Cerebral emboli associated with perfusionist interventions can be minimized by not purging the sampling manifold, using continuous infusions rather than bolus injections, and maintaining high blood-volume levels (>800mL) in the venous reservoir.

Total laparoscopically and robotically assisted aortic aneurysm surgery: a critical evaluation

Background Laparoscopically assisted aortic aneurysm resection requiring a minilaparotomy can be performed as a routine procedure. It was the purpose of our study to evaluate whether a total laparoscopic operation can be offered to aneurysm patients as a minimally invasive alternative. We also wanted to test whether a master-slave robot could facilitate the total laparoscopic procedure. Methods A prospective, consecutive number of 50 patients was evaluated. A transperitoneal left retrocolic access was used to expose the aorta. If possible, a tube graft repair was performed. The aortic anastomosis was sutured totally laparoscopically, with the surgeon standing on the right side of the operating table. In 10 consecutive patients, the anastomosis was sutured with the help of the Zeus robot. Results After excluding 3 cases that required suprarenal cross-clamping, 47 patients were operated using a total laparoscopic approach. A totally laparoscopic operation could be performed successfully in 39 patients with aneurysms. In 8 patients (17%), conversion to a laparoscopic hand-assisted operation with a 7-cm minilaparotomy was required. The robot was used to perform the aortic anastomosis in 10 patients. In 8 patients, a tube graft repair could successfully be performed totally laparoscopically. In the remaining patients, a bifurcated graft was implanted laparoscopically. The mean operating time was 227 minutes in the laparoscopy group and was 242 minutes in those patients in whom the anastomosis was sutured with the help of the Zeus Robot. Mean cross-clamping time, ± SD, was 81.4 + 31 minutes. None of the patients died perioperatively. Major complications occurred in three patients (6.3%). The overall morbidity was 14.8%, including one patient who required temporary hemodialysis postoperatively. The time to suture the aortic anastomosis was significantly shorter in the robotic-assistance group (40.8 ± 4 minutes), yet total operating time was longer in this group because of the technical complexity of the robotic device. Patients with a total laparoscopic procedure asked for significantly fewer analgesics and could regain full mobility earlier compared with those patients for whom a minilaparotomy after conversion to the laparoscopic hand-assist procedure was required. Conclusions Total laparoscopic aneurysm resection can be offered to the majority of patients in our institution. The robot still requires further refinements to reduce operating times and the aortic cross-clamping period. We now have the technique and the instrumentation to offer laparoscopic aneurysm surgery as a minimally invasive alternative for patients whose conditions are unsuitable for endovascular aneurysm repair.

Predictors of cerebrovascular events in patients subjected to isolated coronary surgery. The importance of aortic cross-clamping.

Stroke is a major complication after coronary surgery, occurring in 1-4% of the patients. In this study, we evaluate the incidence and pre- and intraoperative risk factors for the development of a cerebrovascular accident (CVA) and the impact of such an event on perioperative mortality and on hospital length of stay. Data from 4567 patients submitted to isolated coronary artery bypass grafting (CABG) with hypothermic ventricular fibrillation between 1992 and 2001 were entered prospectively into a dedicated computerized database and analyzed retrospectively at this time. Univariate and multivariate analyses were performed where appropriate. The incidence of postoperative CVA was 2.5% (116 patients). Multivariable logistic regression identified the following variables to be independent predictors of a postoperative CVA: cerebrovascular disease (P<0.001; odds ratio (OR), 2.66), peripheral vascular disease (P<0.001; OR, 2.33), number of periods of aortic cross-clamping (P=0.019; OR, 1.31 per each period of aortic cross-clamping), LV dysfunction (P=0.012; OR, 1.82) and age (P=0.008; OR, 1.28 per each 10 years). Non-elective surgery showed a marginal significance (P=0.08; OR 1.83). The 30-day mortality for patients who experienced a CVA was 16.4% versus 0.6% for patients who did not (P<0.001). Postoperative CVA increased the length of hospital stay threefold to 20.3+/-28.3 days as compared with patients who did not have a postoperative CVA (7.6+/-4.2 days; P<0.001). Postoperative CVA dramatically increases the mortality and length of stay after CABG. Identification of predisposing factors permits preoperative risk stratification and may facilitate improved patient selection or optimization. Our study adds evidence to the superiority of the fibrillation technique over intermittent cross-clamping of the aorta, among non-cardioplegic techniques, in terms of neurological protection.

Serum Myoglobin/Carbonic Anhydrase III Ratio in the Diagnosis of Perioperative Myocardial Infarction During Coronary Bypass Surgery

Objective- The purpose of the present study was to evaluate the usefulness of the myoglobin/carboanhydrase III (Myo/CAIII) ratio in the diagnosis of peri operative myocardial infarction during coronary artery bypass surgery.Design- Thirty patients undergoing elective coronary artery bypass grafting (CABG) were included in the series. The patients were randomized in two groups: One received conventional normothermic retrograde blood cardioplegia, while the other was subjected to a 5-min period of ischemic preconditioning before cardioplegia. Biochemical markers for myocardial and skeletal muscle injury were measured in serial blood samples taken postoperatively from 4 h after aortic declamp.Results- Three patients were diagnosed to have suffered from peri operative myocardial infarction on the basis of significant elevations of troponin T and creatine kinase MB-isoenzyme (CK-MB) concentrations. In these particular patients the Myo/CAIII ratio Increased rapidly after aortic declamping. In uncomplicated patients, the median value of the Myo/CAIII ratio remained within normal limits. There was a Positive correlation between the net output of lactate during the aortic cross-clamping period and post-perative Myo/CAIII ratio. The Myo/CAIII ratio proved to be a more specific indicator for myocardial damage than myoglobin alone. The Myo/CAIII ratio was higher in the preconditioning group than in the Control group.Conclusion- Myo/CAIII ratio is a sensitive and specific marker for perioperative myocardial infarction Increasing rapidly after aortic declamping. This ratio could also be used when assessing the extent of ischemic myocardial injury and comparing different Surgical and cardioprotective techniques.

Global and regional cerebral blood flow in neonatal piglets undergoing pulsatile cardiopulmonary bypass with continuous perfusion at 25 degrees C and circulatory arrest at 18 degrees C.

To investigate the influence of hypothermic cardiopulmonary bypass (HCPB) at 25 degrees C and circulatory arrest at 18 degrees C on the global and regional cerebral blood flow (CBF) during pulsatile perfusion, we performed the following studies in a neonatal piglet model. Using a pediatric physiologic pulsatile pump, we subjected six piglets to deep hypothermic circulatory arrest (DHCA) and six other piglets to HCPB. The DHCA group underwent hypothermia for 25 min, DHCA for 60min, cold reperfusion for 10 min, and rewarming for 40 min. The HCPB group underwent 15 min of cooling, followed by 60 min of HCPB, 10min of cold reperfusion, and 30 min of rewarming. The following variables remained constant in both groups: pump flow (150 ml/kg/min), pump rate (150 bpm), and stroke volume (1 ml/kg). During the 60-min aortic crossclamp period, the temperature was kept at 18 degrees C for DHCA and at 25 degrees C for HCPB. The global and regional CBF (ml/100g/min) was assessed with radiolabeled microspheres. The CBF was 48% lower during deep hypothermia at 18degrees C (before DHCA) than during hypothermia at 25 degrees C (55.2 +/- 14.3ml/100g/min vs 106.4 +/- 19.7 ml/100 g/min; p < 0.05). After rewarming, the global CBF was 45% lower in the DHCA group than in the HCPB group 48.3 +/- 18.1 ml/100g/min vs (87 +/- 35.9ml/100g/min; p < 0.05). Fifteen minutes after the termination of CPB, the global CBF was only 25% lower in the DHCA group than in the HCPB group (42.2 +/- 20.7 ml/100 g/min vs 56.4 +/- 25.8ml/100g/min; p = NS). In the right and left hemispheres, cerebellum, basal ganglia, and brain stem, blood flow resembled the global CBF. In conclusion, both HCPB and DHCA significantly decrease the regional and global CBF during CPB. Unlike HCPB, DHCA has a continued negative impact on the CBF after rewarming. However, 15 min after the end of CPB, there are no significant intergroup differences in the CBF.

Does isoflurane optimize myocardial protection during cardiopulmonary bypass?

Objective: To investigate the possible myocardial protective effect of isoflurane during aortic cross-clamp and cardioplegic cardiac arrest in patients undergoing conventional coronary artery bypass graft surgery. Design: Prospective, randomized. Setting: University medical center. Participants: Forty-nine patients undergoing elective coronary artery bypass graft surgery divided into 2 groups: control group (n = 21) and isoflurane group (n = 28). Intervention: Isoflurane was administered in the pre-cardiopulmonary bypass (CPB) period to the isoflurane group. Measurements And Main Results: Hemodynamics and ST- segment variations were monitored in the pre-CPB period and after weaning from CPB in both groups. Incidence of reperfusion arrhythmias after release of aortic cross-clamp was compared. In the isoflurane group, the mean cardiac index after CPB was significantly higher than the pre-CPB value, whereas no difference between the 2 values was found in the control group. The higher cardiac index in the isoflurane group was associated with a lesser degree of ST- segment changes than in the control group. There was no significant difference between the 2 groups in the incidence of reperfusion arrhythmias after release of aortic cross-clamp. Conclusion: The present report suggests that administration of isoflurane before aortic cross-clamping in patients undergoing coronary artery bypass graft surgery may optimize the myocardial protective effect of cardioplegia. Isoflurane may be particularly advantageous whenever prolonged periods of aortic cross-clamping or inadequate delivery of cardioplegia is expected. Copyright © 2001 by W.B. Saunders Company

INFLUENCE OF TEMPERATURE AND CIRCULATORY ARREST ON CEREBRAL BLOOD FLOW IN NEONATAL PIGLETS UNDERGOING PULSATILE CARDIOPULMONARY BYPASS

Purpose: To investigate the influence of temperature and circulatory arrest on global and regional cerebral blood flow (CBF) during pulsatile perfusion, we performed the following studies in a neonatal piglet model. Methods: Using a pediatric physiologic pulsatile pump, we subjected six piglets to deep hypothermic circulatory arrest (DHCA) and six other piglets to hypothermic cardiopulmonary bypass (HCPB). The DHCA group underwent hypothermia for 20 minutes, DHCA for 60 minutes, cold reperfusion for 10 minutes, and rewarming for 40 minutes. The HCPB group underwent 15 minutes of cooling, followed by 60 minutes of HCPB, 10 minutes of cold reperfusion, and 30 minutes of rewarming. The following variables remained constant in both groups: pump flow (150 ml/kg/min), pump rate (150 bpm), and stroke volume (1 ml/kg). During the 60-minute aortic cross-clamp period, the temperature was kept at 18°C for DHCA and at 25°C for HCPB. Global and regional CBF (ml/100g/min) was assessed with radiolabeled microspheres. Results: The CBF was 48% lower during deep hypothermia at 18°C (before DHCA) than during hypothermia at 25°C (55±6 vs. 106±8; P<0.05). After rewarming, the global CBF was 45% lower in the DHCA group than in the HCPB group (48±7 vs. 87±15; P<0.05). Fifteen minutes after the termination of CPB, the global CBF was only 25% lower in the DHCA group than in the HCPB group (42±8 vs. 56±11; P=NS). In the right and left hemispheres, cerebellum, basal ganglia, and brainstem, blood flow resembled the global CBF. Conclusions: Both HCPB and DHCA significantly decrease the CBF during CPB. Unlike HCPB, DHCA has a continued negative impact on the CBF after rewarming. However, 15 minutes after the end of CPB, there is no statistical intragroup difference in the CBF. This may be due to the faster recovery in CBF after DHCA with pulsatile flow.

Single aortic cross-clamp technique reduces S-100 release after coronary artery surgery

Background. Neurologic impairment after coronary artery bypass grafting is associated with cerebral embolization. An important cause of embolism is aortic manipulation. Constructing both distal and proximal anastomoses during a single period of aortic cross-clamping avoids this source of embolism and may reduce neurologic injury after coronary artery bypass grafting. Methods. Fifty consecutive patients undergoing coronary artery bypass grafting were prospectively randomized to group 1, in which a single aortic cross-clamping was used to construct distal and proximal anastomoses, or to group 2, in which the proximal anastomoses were each constructed with a partial occluding aortic clamp. Levels of S-100 and troponin-T release were measured preoperatively and postoperatively. Results. Aortic cross-clamp time was significantly longer in group 1, but other preoperative and intraoperative variables were equally represented in both groups. Control group levels of S-100 and troponin-T were similar. Postoperative S-100 levels were significantly higher in group 2 than in group 1 ( p < 0.015). No significant difference was found between the groups in postoperative troponin-T levels. Conclusions. The results of this trial suggest improved cerebral protection is associated with the single aortic cross-clamp technique for coronary artery bypass grafting with no increase in myocardial damage. The single aortic cross-clamp technique is simple and inexpensive. We recommend its wider use.

Invited commentary

The reappraisal of the off-pump technique in coronary artery bypass grafting (CABG) has renewed interest in looking into myocardial protection. There is now a growing body of evidence to suggest that avoidance of the use of cardiopulmonary bypass (CPB) during CABG could limit myocardial injury. Penttilä and colleagues should be congratulated for attempting to address this issue further by studying cellular metabolites and myocardial injury in patients undergoing CABG with or without CPB (and cardioplegia). The authors found that off-pump CABG is associated with better myocardial energy preservation and less myocardial damage compared with the conventional approach. In the light of this and other previous clinical observations, can we now conclude that the avoidance of CPB and cardioplegia means better myocardial protection? On close scrutiny, however, the answer to this question is not straightforward. Any clinical study of myocardial revascularization with or without CPB is in reality, a comparison of two entirely different surgical approaches, of which CPB is only a part. Besides CPB and cardioplegia, there are many other differences in the two groups of patients. These include different pharmacological management such as the heparin-protamine dosage; normothermia versus hypothermia; the use of intracoronary shunt or the blower during off-pump procedures (and their effects on endothelial function) and, most importantly, regional versus global ischemia. In fact, myocardial ischemia-reperfusion injury is now believed by many to be an acute inflammatory process in which all the above factors play a role. It would be difficult, therefore, if not impossible, to discern the relative contribution of each of these factors in a clinical study, even though it may be prospective, randomized in nature. Current myocardial protection techniques, using different variations of cardioplegia protocols, are based on the principle of decreasing myocardial energy demand by reducing electromechanical activity, cardiac wall tension, and temperature. None of these are significantly changed in off-pump CABG. Although it is now known that the off-pump approach is associated with a reduced inflammatory response, some important questions remain unanswered. For example, is global ischemia under CPB better or worse for the patient than regional ischemia in a beating, unsupported heart? The patients in the CPB group in the current study had a single period of aortic crossclamping. Whether the significantly higher intraoperative lactate levels detected simply reflect accumulation of the metabolite that cannot be continuously washed out is unclear. Also of note is that the biochemical differences observed between the two groups in this study were not translated into clinical benefits for the patients. The postoperative course in both groups was almost identical, which may again simply reflect the fact that all the patients in this study were relatively young with good left ventricular function. Hence, any potential subtle advantages conferred by one particular technique would not be clinically apparent. Scientific knowledge is built up by small additive increments. The observations made by Penttilä and colleagues in this study are provocative and stimulating. However, more basic scientific investigations would be required to further elucidate the exact mechanisms behind these observations.

Use of near-infrared spectroscopy to measure the effects of infrarenal aortic cross-clamping on regional cerebral oxygen saturation in a piglet model

Introduction. Although the hemodynamic changes associated with infrarenal aortic clamping have been well described, the effects on cerebral perfusion are unknown. The purpose of this study was to characterize these effects by monitoring regional cerebral oxygen saturation (rSO2) using near-infrared spectroscopy (NIRS) during a period of infrarenal aortic cross-clamping. NIRS has the advantages of being noninvasive and continuous.

Emergency reinstitution of cardiopulmonary bypass following cardiac surgery: outcome justifies the cost

Crash back on bypass (crash-BOB) is occasionally required in the resuscitation of patients developing life-threatening complications following cardiac surgery. This study aims to determine the incidence, aetiology and cost-effectiveness of such intervention. Retrospective review of all crash-BOB patients over 5.5 years at one hospital. The incidence of crash-BOB was 0.8% and occurred at a mean of 7 h post-operatively (range 1 h-20 days). Pre-operative Parsonnet scores were similar to the overall population of patients undergoing surgery in our institution (mean score 10; range 0-45). The original cardiac operations were coronary revascularization (39), valve surgery (12) and others (4). Indications for crash-BOB were cardiac arrest (23), bleeding (20), hypotension (7), ischaemia (1) and others (4). Of the 55 patients, 20 died on the operating table. Of the remaining 35, a further 12 died in hospital. Overall survival was therefore 42%. Where crash-BOB was for bleeding, 17 of 20 patients (85%) survived to leave theatre, of whom 11 patients (55%) left hospital alive. In the 35 non-bleeders, only 18 (51%) survived crash-BOB and 12 (34%) left hospital alive. Sixteen patients required a second period of aortic cross-clamping of whom 13 (81%) survived to leave theatre, and 11 (69%) left hospital alive. Conversely, of nine patients in whom no specific diagnosis was found during crash-BOB, only two (22%) survived the procedure and none survived to hospital discharge. Multiple logistic regression identified pre-operative Parsonnet score (P=0.045) and the need for aortic cross-clamping to deal with an identified surgical problem (P=0.03) as significant predictors of hospital survival. Indication for crash-BOB (bleeder/non-bleeder) failed to reach significance (P=0.08). Age, sex, intra-aortic balloon pump use at the primary procedure, and time following the primary procedure to crash-BOB were not identified as predictors of hospital survival. Of the 23 hospital survivors, three patients suffered a stroke post-operatively and made a good functional recovery prior to discharge. Two patients developed sternal wound dehiscence requiring surgical rewiring. At follow-up (mean 3 years, range 1-6 years), 19 patients were in NYHA class I and four were in class II. Crash-BOB patients required an average of 8 extra intensive care days and 2 extra ward days. The total cost of these resources was pound164900 (including theatre time, cardiopulmonary bypass and intra-aortic balloon pump use). This was equivalent to pound7170 per life saved. Crash-BOB occurred in 0.8% of cases and was associated with a survival to discharge of 42%, and a justifiable cost of only pound7170 per life saved. Establishing an accurate diagnosis for the cause of clinical deterioration resulting in crash-BOB intervention was important, and the need for a further period of aortic cross-clamping did not preclude a favourable outcome.

Simultaneous carotid endarterectomy and coronary revascularization

Background. Combined cardiac operation and carotid endarterectomy using our technique is an acceptable approach to simultaneous correction of both carotid and cardiac disease.Methods. From August 1989 to March 1998, 121 consecutive patients underwent combined operations. Of these patients, 112 had coronary artery bypass grafting and carotid endarterectomy, and 9 had coronary artery bypass grafting, carotid endarterectomy, and valve repair or replacement. All patients had a critical stenosis of 85% or more of the carotid artery. Mean age of the patients was 69.2 years; 80 patients were 65 years old or older. There were 88 men and 33 women. Notable risk factors included chronic obstructive pulmonary disease (19.8%), congestive heart failure (28%), preoperative myocardial infarction and unstable angina (66.9%). Of the patients, 20.7% had a stenosis of greater than 50% of the left main coronary artery. The technique used was correction of both the carotid and coronary lesions during a single aortic cross-clamp period using retrograde continuous blood cardioplegia for myocardial protection. Systemic hypothermia to 25°C was used for cerebral protection.Results. Mean cross-clamp time was 118 minutes. Seven patients (5.8%) sustained perioperative cerebrovascular accidents. Two patients had transient ischemic attacks. The procedure-related mortality rate was 5.8%.Conclusions. The described technique is a good method for simultaneous repair of coronary and carotid lesions in a high-risk group of patients with concomitant disease. We will continue to use it.

Antegrade/retrograde cardioplegia for valve replacement: a prospective study

Background. From 1994 to 1996, 75 patients undergoing valve replacement were randomized to antegrade (36 patients, group 1) or antegrade/retrograde (39 patients, group 2) administration of cold blood cardioplegia.Methods. Groups were comparable for age, sex, valve disease, and ventricular dysfunction. The aortic valve was replaced in 27 patients from group 1 and 24 patients from group 2, the mitral valve in 8 and 15 patients, and 1 patient in group 1 underwent double valve replacement (p = not significant).Results. Lengths of cardiopulmonary bypass and aortic cross-clamp averaged, respectively, 10 minutes (p = not significant) and 12 minutes (p = < 0.05) shorter in group 2. Total amount of cardioplegia solution infused averaged 1,279 ± 406 mL and 1,341 ± 379 mL (p = not significant), respectively, in groups 1 and 2, and the period of infusion averaged 44% and 72% (p = < 0.01) of the total period of aortic cross-clamping. No death occurred in group 1 compared to two in group 2 (p = not significant). The perioperative myocardial infarction and stroke rates were comparable in both groups. Peak enzyme release at 24 hours was similar both for creatine kinase-MB fraction (26 versus 37 IU/L) and for troponin T (2.1 versus 2.5 IU/L).Conclusions. Our study shows no significant advantage of the antegrade/retrograde administration of cardioplegia over the antegrade route in routine valvular replacement, other than a slightly shorter aortic cross-clamping time.

Within patient variability of lower extremity muscle responses to transcranial electrical stimulation with pulse trains in aortic surgery

Intraoperative recording of myogenic motor responses evoked by transcranial electrical stimulation is a method of controlling the integrity of the motor pathways during clamping of the aorta. It is important to know the within patient variability of the transcranial motor evoked potential (tcMEP), before changes within the variability range are interpreted as abnormal during the period of aortic cross clamping. Lower limb muscle responses were obtained in 11 patients, following transcranial electrical stimulation with pulse trains, of 4, 6 and 8 pulses. Under the conditions of partial neuromuscular blockade and a stable low dose propofol/fentanyl/nitrous oxide anaesthetic state, this study shows that multipulse transcranial electrical stimulation reliably produces muscle responses of the lower limb in all patients tested with a coefficient of variation (CV) of around 20%. Eight pulses in the stimulation train produce neurophysiological facilitation that exceeds a 4 pulse train in terms of area under the curve (AUC) and response duration. The use of multipulse stimulation rather than double or single pulse stimulation is recommended in order to increase the clinical efficacy of tcMEP monitoring in aortic surgery.

Ultrastructural assessment of the myocardium receiving intermittent antegrade warm blood cardioplegia

Ultrastructural changes in the myocardium during intermittent warm blood cardioplegia were studied in 12 dogs. During cardiopulmonary bypass, dogs received three 5-minute periods of warm blood cardioplegia, interrupted by three 10-minute episodes of ischemia in group A or three 20-minute episodes of ischemia in group B. Biopsy specimens were taken from the right ventricle before each cardioplegic infusion and at the end of the aortic cross-clamp period to analyze ultrastructural changes. Functional recovery was measured after cardiopulmonary bypass. Mild and principally reversible ultrastructural changes were observed in group A. In group B, moderate ultrastructural changes were observed, and these changes suggested cumulative ischemic injury. Functional recovery was good in group A, but significantly deteriorated in group B. We concluded that three 10-minute interruptions of warm blood cardioplegia cause mild ultrastructural changes and seem to be safe, but three 20-minute interruptions cause cumulative ischemic injury in normal dog hearts.

Severe Hypercarbia During Cardiopulmonary Bypass

Severe Hypercarbia During Cardiopulmonary Bypass