BACKGROUND:Generic price inflation has resulted in rising acquisition costs for sodium nitroprusside (SNP), an agent historically described as the drug of choice for the treatment of perioperative hypertension in cardiac surgery.PURPOSE:To describe the implementation and cost avoidance achieved by utilizing clevidipine as an alternative to SNP in cardiac surgery patients at a 520-bed community teaching hospital that performs more than 300 cardiac surgeries each year.METHODS:A multidisciplinary team inclusive of anesthesiologists, intensivists, pharmacists, and surgeons collaborated to develop a therapeutic interchange for SNP in cardiac surgery patients. Consistent with current guidelines for therapeutic interchange, the goal was to encourage a less expensive alternative that was demonstrated to be at least therapeutically equivalent to SNP based on data derived from clinical trials published in peer-reviewed literature. A comprehensive literature review identified clevidipine as an alternative to SNP for perioperative hypertension in cardiac surgery. Nicardipine was considered as well, but was not chosen as a substitute due to lack of strong evidence and comparative data with SNP.RESULTS:Clevidipine was implemented successfully in our cardiac surgery patients and will result in a net cost avoidance of approximately $300,000 in 2016. This is thought to be driven largely by the difference in acquisition cost between clevidipine and SNP. The operating room in our institution no longer keeps SNP stocked in anesthesia trays as a result of the success of our interchange. No requests have been made to return to the SNP standard.CONCLUSION:Through effective communication and multidisciplinary collaboration, our institution was able to develop an evidence-based and effective therapeutic interchange program for SNP.

Background Geographic location is not acknowledged as a stratifying factor that can directly affect drug potency, because drugs are still licensed with the same recommended dose for different geographic regions. The aim of the current study was to compare the potency and duration of action of rocuronium bromide in 54 patients in three countries with different life habits, diet, and ambient conditions, namely white Austrians, white North Americans, and Han Chinese in China. Methods Neuromuscular block of six consecutive 50-microg/kg rocuronium incremental doses followed by 300 microg/kg was evaluated using the Relaxometer mechanomyograph (Groningen University, Groningen, Holland). Dose-response curves were created using log-dose-probit transformation. The authors compared rocuronium bromide ED50, ED90, and ED95 (effective doses required for 50%, 90%, and 95% first twitch depression, respectively) as well as Dur25 and Dur0.8 (times from last incremental dose administration until 25% first twitch and 0.8 train-of-four ratio recovery, respectively) in patients of the three countries. Results Rocuronium ED50, ED90, and ED95 were significantly higher in Austrian patients (258 +/- 68, 530 +/- 159, and 598 +/- 189 microg/kg) and Chinese patients (201 +/- 59, 413 +/- 107, and 475 +/- 155 microg/kg) compared with American patients (148 +/- 48, 316 +/- 116, and 362 +/- 149 microg/kg, respectively). Dur25 and Dur0.8 were significantly shorter in Austrian patients (22.3 +/- 5.5 and 36.9 +/- 12.8 min) and Chinese patients (30.4 +/- 7.5 and 45.7 +/- 15.9 min) compared with American patients (36.7 +/- 8.5 and 56.2 +/- 16.7 min, respectively). Conclusions The authors demonstrated a significant difference in rocuronium potency and duration of action among patients in the three countries. Larger studies are required for determining dosage recommendations for different geographic regions.

BACKGROUND Acute normovolaemic haemodilution (ANH) is an effective strategy for avoiding or reducing allogeneic blood transfusion. We aimed to study its effect on the pharmacological profile of rocuronium. METHODS In two study centres, 28 patients undergoing major surgery with ANH were matched with 28 control patients. In the dose-response groups, using the mechanomyograph, neuromuscular block of six consecutive incremental doses of rocuronium 50 microg kg(-1), followed by 300 microg kg(-1), was evaluated. In the pharmacokinetics groups, serial arterial blood samples were withdrawn for rocuronium assay after a single dose of rocuronium 600 microg kg(-1). RESULTS ANH resulted in a shift to the left of rocuronium dose-response curve. Rocuronium effective dose(95) (ED(95)) was 26% lower (P<0.05) in the ANH group [283.4 (92.0) microg kg(-1)] compared with the control group [383.5 (127.3) microg kg(-1)]. Times from administration of last incremental dose until 25% of first response of train-of-four (TOF) recovery (Dur(25)) and 0.8 TOF ratio recovery (Dur(0.8)) were 28% longer in the ANH group [39.9 (8.4), 66.7 (14.2) min] compared with the control group [31.1 (6.6), 52.1 (15.8) min] (P<0.01, P<0.05), respectively. Volume of distribution was higher (P<0.01), central clearance was lower (P<0.05) and terminal elimination half-life was longer (P<0.0001) in the ANH group [234.97 (47.11) ml kg(-1), 4.70 (0.94) ml kg(-1) min(-1), 77.29 (12.25) min] compared with the control group [181.22 (35.73) ml kg(-1), 5.71 (1.29) ml kg(-1) min(-1), 56.86 (10.05) min, respectively]. CONCLUSION ANH resulted in prolongation of rocuronium time-course of action, thus careful monitoring of neuromuscular block is recommended in patients who undergo ANH.

BackgroundPrevious studies defining perioperative risk factors for allogeneic transfusion requirements in cardiac surgery were limited to highly selected cardiac surgery populations or were associated with high transfusion rates. The purpose of this study was to determine perioperative risk factors and create a formula to predict transfusion requirements for major cardiac surgical procedures in a center that practices a multimodality approach to blood conservation.MethodsWe performed an observational study on 307 consecutive patients undergoing coronary artery bypass grafting, valve, and combined (coronary artery bypass grafting and valve) procedures. An equation was derived to estimate the risk of transfusion based on preoperative risk factors using multivariate analysis. In patients with a calculated probability of transfusion of at least 5%, intraoperative predictors of transfusion were identified by multivariate analysis.ResultsThirty-five patients (11%) required intraoperative or postoperative allogeneic transfusions. Preoperative factors as independent predictors for transfusions included red blood cell mass, type of operation, urgency of operation, number of diseased vessels, serum creatinine of at least 1.3 mg/dL, and preoperative prothrombin time. Intraoperative factors included cardiopulmonary bypass time, three or fewer bypass grafts, lesser volume of acute normovolemic hemodilution removed, and total crystalloid infusion of at least 2,500 mL. The derived formula was applied to a validation cohort of 246 patients, and the observed transfusion rates conformed well to the predicted risks.ConclusionsA multimodality approach to blood conservation in cardiac surgery resulted in a low transfusion rate. Identifying patients' risks for transfusion should alter patient management perioperatively to decrease their transfusion rate and make more efficient use of blood resources.

Thoracic aortic surgery in Jehovah’s Witness (JW) patients presents a unique challenge to the surgeon and anesthesiologist because the patient’s religious-based objection to the use of allogeneic blood products impacts surgical technique and intraoperative fluid management methodology. Successful thoracic aortic repair without the transfusion of allogeneic blood products is especially difficult because the outcome of this type of surgery usually depends on the transfusion of relatively large amounts of allogeneic blood products. 1 Svensson L.G. Crawford E.S. Hess K.R. et al. Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg. 1993; 17: 357-368 Abstract Full Text Full Text PDF PubMed Scopus (1091) Google Scholar To maintain a treatment course congruent with the JW patient’s religious beliefs, alternative methods of blood conservation should be used by the anesthesiologist. 2 Dupuis J.F. Nguyen D.T. Anesthetic management of the patient who refuses blood transfusions. Int Anesthesiol Clin. 1998; 36: 117-131 Crossref PubMed Scopus (2) Google Scholar Two cases are presented in which a JW patient underwent repair of a thoracoabdominal aneurysm (TAA), and a third case of a JW patient who underwent repair of an aortic root and arch aneurysm. All cases used acute normovolemic hemodilution (ANH) and underwent successful surgical repair without the use of allogeneic blood products.

Endovascular aortic repair is a new alternative to conventional surgical techniques. A variety of devices available for endovascular aortic repair are discussed and the outcomes after repair are reviewed. Anesthetic considerations during endovascular repair are dictated by the device being used, as well as the site of device deployment. Requirements for the optimization of hemodynamic states during proximal graft deployment are described, as well as the available options for induction of ventricular asystole. Since arterial rupture is always a risk when using this procedure, appropriate facilities must be present for resuscitation. Patients undergoing repair of thoracic aortic pathology may be candidates for perioperative transesophageal echocardiographic monitoring. Since a subgroup of these patients may be at risk for postoperative paraplegia, aggressive spinal cord protection should be considered. Patients with large aneurysms may be at risk for "post-implantation syndrome," which is characterized by hyperpyrexia, hypotension, and coagulopathy.

Prophylactic optimization of stroke volume during surgery has been thought by some to reduce complications following surgery. Mechanical ventilation has been shown to induce variations in systolic systemic arterial blood pressure. Measuring such variations in systolic pressure (SPV) might serve as an attractive method for guiding fluid therapy intraoperatively. It is unknown if variations in systolic pressure following the rapid intravenous administration of a specific volume of fluid would lead to changes in pressure measurements obtained from a pulmonary artery with sufficient sensitivity to predict or guide the need for expansion of the intravascular volume to optimize stroke volume as an index of cardiac function. The purpose of this study was to determine if such measurements of changes in systolic pressures would be useful in optimizing stroke volume.Nineteen patients undergoing cardiac surgery were enrolled in a prospective cohort study. Following induction of general anesthesia. one or more 250 mL boluses of 6% hetastarch were administered. Stroke volume was calculated from the cardiac output obtained by thermodilution using a pulmonary artery catheter. If the patient's stroke volume increased by less than 10% as a result of a given fluid challenge, the patient was classified as a non-responder. However, if the stroke volume increased by more than 10%. the patient was classified as a responder. The variations in systolic pressure and echocardiographic indices were simultaneously measured before and after the administration of each 250 mL fluid bolus.Pulmonary artery occlusion pressure (PAOP) values were significantly lower in patients who responded to fluid boluses (p=0.0085) than in those who did not. Similarly SPV and SPVdown values (defined as the decrease in systolic pressure with ventilation) were significantly greater in the responders (p<0.05). No significant intergroup differences were observed in SPV up (increase in systolic pressure with ventilation) or echocardiographic-derived left ventricular end diastolic area. A PAOP value less than 10 mm Hg predicted a response (sensitivity 68%, specificity 79%). Although significant intergroup differences in the extent of systolic pressure variations were observed. no appropriate threshold values could be determined that would accurately predict the response to a fluid bolus.There is a relationship between SPV and SPVdown values and intravascular volume status. SPV and echocardiographic-derived values did not predict the response to a fluid bolus as well as values obtained from the pulmonary artery catheter.

ENDOVASCULAR AORTIC REPAIR is a new alternative to conventional surgical repair of aortic pathology.1 This technique of aortic repair was first suggested by Dotter2 in 1969 and reached clinical application with the work of Parodi et al3 in 1990. Since this early work, the technology has been applied to the treatment of peripheral artery aneurysms,4,5 diffuse aortoiliac occlusive disease,6 aortic aneurysms and dissections, and traumatic aortic or arterial injuries.7 Endovascular grafts have the advantage of being a less-invasive technique compared with conventional arterial reconstructions, owing to the unique ability to insert these grafts through small incisions from remote arterial access sites. This minimally invasive approach results in several advantages to the patient compared with conventional aortic repair. Many patients undergoing aortic repair have concomitant cardiac, renal, and pulmonary disease, increasing the complexity of any anesthetic administered. Avoiding laparotomy or thoracotomy eliminates the need for extensive perioperative aortic dissection, which may be complicated by previous aortic surgery. This technique obviates the need for extensive and prolonged aortic occlusion, decreases blood loss, and avoids the significant fluid shifts that occur with visceral manipulation, lowering the risk of significant perioperative hemodynamic changes. Conventional open aortic repair required general anesthesia with or without supplemental regional anesthesia. Repair through the endovascular route is a less-invasive technique compared with an open reconstruction,8 requiring less anesthesia.

Purpose: To assess the safety and efficacy of high-dose adenosine administration to increase the precision of endovascular abdominal aortic aneurysm (AAA) repair using a balloon deployed stent-graft. Methods: From January 1997 to March 1999, 98 AAA patients (79 men; mean age 71 years, range 62–91) were treated with balloon-expandable stent-grafts under an approved protocol. After placing a temporary transvenous ventricular lead or an external transthoracic pacing electrode, adenosine (24 mg initially) was administered in an escalating dose fashion to induce at least 10 seconds of asystole, during which the proximal stent was expanded. Results: Adenosine dosages ranged from 24 to 90 mg (median 24 mg). Nine (9.2%) self-limiting cardiac events were observed: 2 (2.0%) episodes of transient myocardial ischemia, 2 (2.0%) cases of atrial fibrillation requiring cardioversion, 1 (1.0%) transient left bundle branch block lasting <10 seconds, and 4 (4.1%) prolonged periods of asystole requiring temporary pacemaker activation. There were no cases of bronchospasm or worsening obstructive pulmonary disease, and no patients required inotropic support after adenosine-induced asystole. Conclusions: Cardiac events following adenosine-induced asystole are infrequent, mild, and easily treated. The perioperative use of high-dose adenosine to ensure precise stent-graft placement appears to be a safe method of inducing temporary asystole during endovascular aortic repair.

Objective: Examination of overall hemodynamic stability in patients undergoing endovascular aortic repair (EAR) compared with open aortic repair (OAR).Design: Retrospective study.Setting: University hospital setting.Participants: Seventy-two patients undergoing OAR and 17 patients undergoing EAR were studied. Interventions: None.Measurements and Main Results: Physiologic parameters were extracted every 15 seconds from computerized anesthesia records. Median values were calculated for every 2-minute epoch, and the absolute value of the fractional change in median (\FCM\) from epoch to epoch was calculated for a maximum of 5 hours during the intraoperative period. The incidence of extremes in hemodynamic parameters was compared. Data are presented as median and interquartile ranges. The frequency of \FCM\ greater than 0.06 for mean arterial pressure (MAP) was significantly greater in the OAR compared with the EAR group (0.37 [0.30, 0.46] vs 0.14 [0.11, 0.21], p < 0.0001), implying greater stability in MAP during EAR. Similarly, the mean pulmonary artery pressures (MPAPs) were significantly more stable during EAR compared with OAR (frequency of \FCM\ > 0.07: EAR, 0.20 [0.16, 0.27] vs OAR, 0.32 [0.26, 0.39]; p < 0.01). No intergroup differences were detected in heart rate (HR), systolic (SPAP) or diastolic pulmonary artery pressures (DPAP), or central venous pressures (CVPs). With the exception of a greater incidence of low CVP during EAR, there were no significant differences in the frequency of extremes of hemodynamic values between groups.Conclusion: These results show improved hemodynamic stability during EAR compared with OAR. Copyright (C) 1999 by W.B. Saunders Company.

Hestend((R)) (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and physiological levels of glucose. In preclinical studies, its use in shock models was associated with an improvement in outcome compared with alternatives, such as albumin or 6% hetastarch in saline. In a prospective, randomized, two-center study (n = 120), we compared the efficacy and safety of Hextend((R)) versus 6% hetastarch in saline (HES) for the treatment of hypovolemia during major surgery. Patients at one center had a blood sample drawn at the beginning and the end of surgery for thromboelastographic (TEG) analysis. Hextend((R)) was as effective as HES for the treatment of hypovolemia. Patients received an average of 1596 mt of Hestend((R)): 42% received >20 mL/kg up to a total of 5000 mt. No patient received albumin. Hextend((R))-treated patients required less intraoperative calcium (4 vs 220 mg; P < 0.05). In a subset analysis of patients receiving red blood cell transfusions (n = 56; 47%), Hextend((R))-treated patients had a lower mean estimated blood loss (956 mt less; P = 0.02) and were less likely to receive calcium supplementation (P = 0.04). Patients receiving HES demonstrated significant prolongation of time to onset of clot formation (based on TEG) not seen in the Hextend((R)) patients (P < 0.05). No Hextend((R)) patient experienced a related serious adverse event, and there was no difference in the total number of adverse events between the two groups. The results of this study demonstrate that Hextend((R)), with its novel buffered, balanced electrolyte formulation, is as effective as 6% hetastarch in saline for the treatment of hypovolemia and may be a safe alternative even when used in volumes up to 5 L. Implications: Hextend((R)) (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and a physiological level of glucose. It is as effective as 6% hetastarch in saline for the treatment of hypovolemia but has a more favorable side effects profile in volumes of up to 5 L compared with 6% hetastarch in saline.

Introduction: Endovascular stent-graft placement has recently become an alternative to conventional surgical treatment of abdominal aortic aneurysms (AAA). Because of the large surface area of these devices, forward aortic flow may result in significant device migration with resultant malpositioning of the endovascular device. This device malposition may result in either occlusion of major arterial branches or incomplete aneurysm exclusion. In order to assure precise device positioning and to prevent distal migration, high dose adenosine may be used to induce temporary high degree AV block [1]. We present our experience with the use of high dose adenosine for induction of temporary asystole during endovascular aortic repair (EAR) in over 100 patients. Methods: Endovascular repair of AAA were carried out in accordance with investigator sponsored Investigational Device Evaluation protocol from the United States Food Federal Drug Administration, and approval of the Institutional Review Board. After placement of either a temporary transvenous ventricular lead or an external transthoracic pacing electrodes, adenosine was administered in an escalating dose fashion in order to induce at least 10 seconds of asystole during proximal stent-graft deployment. Results: The records of 105 patients undergoing EAR were reviewed. The dose range of adenosine administered was 12-60 mg with a median value of 24 mg. Two patients had transient episodes of myocardial ischemia (diagnosed by ST segment depression), which resolved within 30 seconds after return of the patient's baseline rhythm. Two patients developed atrial fibrillation after adenosine administration, which responded to synchronized direct current cardioversion, and one patient developed a transient bundle branch block, which did not adversely effect hemodynamics. Two patients required temporary activation of their indwelling temporary transvenous pacemakers for prolonged bradycardia or AV block after adenosine. No patients developed bronchospasm, required treatment for worsening obstructive pulmonary disease, or received inotropic support that was not required prior to adenosine administration. Conclusions: EAR is a viable alternative to conventional open surgical aortic reconstruction. The perioperative use of high dose adenosine to ensure precise stent-graft placement appears to be a safe method of inducing temporary asystole during endovascular aortic repair in this high risk surgical population.

OBJECTIVESTo define the utility of intraoperative transeophageal echocardiography (TEE) during endovascular thoracic aortic repair.DESIGNRetrospective study.MATERIALSFive patients underwent six transluminal endovascular stent-graft procedures for repair of thoracic aortic disease.METHODSAfter induction of anaesthesia, a multiplane or biplane TEE probe was placed to obtain views of the diseased aorta. Both transverse and longitudinal planes of the aortic arch and descending thoracic aortic segments were imaged. The aortic pathology was confirmed by TEE and the proximal and distal extents of the intrathoracic lesion were defined. Doppler and colour-flow imaging was used to identify flow patterns through the aorta before and after stent-graft deployment.RESULTSVisualisation and confirmation of the aortic pathology by ultrasonography was accomplished in all patients. TEE was able to confirm proper placement of the endograft relative to the aortic lesion after deployment and was able to confirm exclusion of blood flow into the aneurysm sacs.CONCLUSIONSTEE may facilitate repair by confirming aortic pathology, identifying endograft placement, assessment of the adequacy of aneurysm sack isolation, as well as dynamic intraoperative cardiac assessment.

{image:2} {image:3} One technique used for the deployment of the endovascular aortic device employs large balloon angioplasty catheters to expand and secure the proximal stent portion of the endovascular graft to the underlying vessel wall. (Figure 4) These balloons have a large cross sectional area, predisposing them to distal aortic migration as a result of the forward aortic blood flow. This device malposition may result in either occlusion of major arterial branches or incomplete aneurysm exclusion. Many techniques have been advocated to prevent this distal migration. (Table 3) One of these techniques is the administration of high dose adenosine, which results in temporary high degree AV block (2). In this report, we present our experience with the use of high dose adenosine for induction of temporary asystole during endovascular aortic repair (EAR) in 100 patients. {image:4} Table 2: Pharmacology of Adenosine Adenosine Pharmacology Negative dromotropic and chronotropic effects at SA and AV nodes. No inotropic effects Systemic, pulmonary, & coronary vasodilatation Short half life (t1/2 ‹ 10 seconds)

Background: Whole body hyperthermia induced by radiative systems has been used in therapy of malignant diseases for more than ten years.Von Ardenne and co-workers have developed the 'systemiche Krebs-Mehrschritt-Therapic' (sKMT), a combined regime including whole body hyperthermia of 42°C, induced hyperglycaemia and relative hyperoxaemia with additional application of chemotherapy.This concept has been employed in a phase I/II clinical study for patients with metastatic colorectal carcinoma at the Virchow-Klinikum since January 1997.Methods: The sKMT concept was performed eleven times under intravenous general anaesthesia, avoiding volatile anaesthetics.Core temperatures of up to 42°C were reached stepwise by warming with infrared-A-radiation (IRATHERM 2000®).During the whole procedure blood glucose levels of 380-450 mg/dl were maintained as well as PaO 2 levels above 200 mmHg.Extensive invasive monitoring was performed in all patients including measurements with the REF-Ox-Pulmonary artery catheter with continuous measuring of mixed venous saturation (Baxter Explorer®) and invasive monitoring of arterial blood pressure.Data for calculation of hemodynamic and gas exchange parameters were collected four times, at temperatures of 37°C, 40°C, 41.8-42°C and 39°C, during measurements FiO 2 was 1.0 at all times.Fluids were given in order to keep central-venous and Wedge pressure within normal range during the whole procedure.Statistics were performed using the Wilcoxon Test.Results: Statistically significant differences were found between heart rate, cardiac index and systemic vascular resistance comparing data at 37°C and 42°C.Heart rate and cardiac index increased to a maximum at 42°C (P < 0.0001) whereas systemic vascular resistance had its minimum at 42°C (P < 0.0001).Mean arterial pressure dropped with increasing temperature, differences were not significant.Calculation of stroke volume index and ventricular volumes showed only a slight decrease in endsystolic volumes with increasing temperature, the resulting differences in right ventricular ejection fraction were marginally significant (P = 0.038) comparing 42°C to baseline.Right ventricular stroke work index as well as mean pulmonary arterial pressure increased at 42°C (P = 0.0115 and P = 0.0037), pulmonary vascular resistance only dropped little compared to systemic vascular resistance, left ventricular stroke work index even dropped with increasing temperature, though showing no significant difference.Values for mixed venous oxygen saturation did not vary during therapy, pulmonary right-left shunt showed a temperature associated increase (P = 0.0323) to a maximum at 42°C.Conclusion: Under the procedure of sKMT cardiac function in patients, who do not have any pre-existing cardiac impairment, can be maintained almost unchanged, ie with normal right and left ventricular pressure, despite an increase in right ventricular stroke work

S73 INTRODUCTION: Conventional open abdominal aortic reconstruction (OAR) may be associated with significant hemodynamic instability. Previous work have demonstrated improved hemodynamic stability in patients undergoing endovascular aortic repair (EAR) compared with OAR: however, these studies were limited because a limited number of discrete intervals were examined. [1,2] In this study we examined overall hemodynamic stability in patients undergoing EAR compared with OAR. METHODS: The study was approved by the IRB. Heart rate, mean arterial pressure, and mean pulmonary arterial pressure were extracted (every 15 seconds) from computerized anesthesia records for 72 OAR and 15 EAR procedures for a maximum of 5 hours. The median value of each hemodynamic parameter was calculated for every 2 minute epoch in order to filter for artifact, and the absolute value of the fractional change in median ([vertical bar]FCM[vertical bar]) from epoch to epoch was calculated. The proportion of [vertical bar]FCM[vertical bar]>0.06 was used as an index of lability as previously validated. [3] Additionally, the proportion of the procedure in which the 2-minute median data were outside of specified normal ranges was calculated. The data were compared between groups using the Mann-Whitney U test. A two-tailed p<0.05 was considered significant. RESULTS: EAR cases were significantly more stable hemodynamically than OAR for all three parameters. The data are presented in Table 1. There were no statistically significant intergroup differences in the proportion of each patients' procedure in which hemodynamic parameters were outside of specified normal ranges.Table 1: Intraoperative hemodynamic lability algorithm results-Proportion of [vertical bar]FCM[vertical bar]>0.06.DISCUSSION: EAR is a minimally invasive procedure which offers many advantages over OAR. The need for mesenteric and retroperitoneal dissection are eliminated and no aortic cross clamp is required. The use of epidural anesthesia and the potential for hemorrhage, however, do not eliminate the risk of intraoperative hemodynamic instability. Our results demonstrate improved hemodynamic stability associated with EAR in comparison with OAR, implying that these procedures may be safer for high risk patients.

(Moskowitz) Clinical Assistant Professor, Department of Anesthesiology.(Kahn) Assistant Professor, Department of Anesthesiology.(Camunas) Clinical Associate Professor, Department of Cardiothoracic Surgery.(Marin) Associate Professor, Department of Surgery.(Hollier) Julius H. Jacobson II Professor of Vascular Surgery; Chairman, Department of Surgery.ENDOVASCULAR stent graft placement recently has become an alternative to open laparotomy in the treatment of abdominal aortic aneurysms. [1]During deployment of the aortic stent graft, temporary asystole is induced to prevent distal device migration, which may result in ineffective aneurysm exclusion by the stent graft or possible aortic damage by device embolization. Currently, high-dose adenosine usually is used to induce temporary high-degree atrioventricular block and asystole during deployment of the device. [2,3]Patients with permanent pacemakers present a unique problem. There must exist a temporary way of inhibiting the pacemaker during the action of adenosine. Although newer pacemaker generators can be inhibited temporarily by perioperative reprogramming, older pacemakers may have limited programmability, making this task impossible. In this case report, we describe the perioperative use of external chest wall stimulation for temporary inhibition of a pacemaker during endovascular repair of an abdominal aortic aneurysm in a patient with an older generator with limited programmability.An 86-yr-old man presented for repair of an 8-cm infrarenal abdominal aortic aneurysm with bilateral iliac artery extension. His medical history was significant for atrial fibrillation with a slow ventricular response requiring insertion of a ventricular pacemaker (model number 505; Cardiac Pacemaker Incorporation, St. Paul, MN) 17 yr before admission. CXR showed a pacemaker generator and an intact ventricular lead. The electrocardiogram showed atrial fibrillation with a ventricular response of 55–60 beat/min with intermittent paced ventricular beats with 1:1 capture.Preoperative evaluation of the pacemaker confirmed a normally functioning unipolar VVI pacemaker. Application of a magnet over the generator did not result in an end-of-life signal (a decrease in the ventricular pacing rate), indicating that the generator had an adequate battery charge, obviating the need for generator change. The pacemaker had limited programmability and could only be programmed to a ventricular rate of 30 beat/min. Because of this generator feature, external chest wall stimulation was planned to inhibit the pacemaker temporarily during intraoperative administration of adenosine.After radial and pulmonary arterial catheterization, an epidural catheter was inserted for perioperative anesthesia. Two electrocardiogram monitoring electrodes were placed along the vector between the cathode (negative electrode) and anode (positive electrode) of the pacemaker generator to optimize the ability of the pacemaker generator to detect an externally generated signal (Figure 1). The electrocardiogram monitoring pads were connected to an external temporary transvenous single-chamber demand pulse generator (model 5375; Medtronic [registered sign], Minneapolis, MN) via a temporary pacemaker cable with alligator clip connections (model 5807; Medtronic). The temporary external generator was set to 80 beat/min, which was greater than the rate of the internal pacemaker. The generator output was slowly increased until the internal pacemaker was inhibited (3 milliamperes); at this output, the internal pacemaker sensed the external signals as intrinsic QRS complexes and was inhibited. No discomfort was reported by the patient during electrical stimulation. After confirmation of the ability to inhibit the pacemaker temporarily with external chest wall stimulation, the surgical procedure commenced.After positioning of the aortic stent graft, temporary asystole was induced during deployment of the device. The patient was sedated with etomidate, and the temporary generator was activated (Figure 2). Adenosine (24 mg) was administered via the central venous catheter followed by a bolus dose of normal saline. (In our unpublished experience, 24 mg adenosine given via the central circulation provides an adequate period of asystole [10 - 30 s] for deployment of the stent graft in most patients.)Approximately 7 s after administration of adenosine, the patient became asystolic, the angioplasty balloon was inflated, and the stent graft was deployed. Proper positioning of the stent graft at the aneurysm neck was confirmed by fluoroscopy. Deployment of the device was completed after approximately 45 s. During this period, the patient was asystolic, with occasional atrioventricular nodal or ventricular escape beats. There were no ventricular beats produced by the patient's permanent pacemaker. After deployment of the stent graft, the external demand pulse generator was turned off, and the patient's internal pacemaker immediately began to function at its preset level (Figure 2B). The patient's heart rate returned to its preasystolic rate as the effects of adenosine dissipated. The rest of the procedure was uneventful, and the patient was taken to the postanesthesia care unit in stable condition. The patient had an uneventful recovery and was discharged home on postoperative day 2.Endovascular stent graft placement recently has become an alternative surgical technique to repair abdominal aortic aneurysms. [1]To minimize movement of the device during deployment, temporary asystole is induced using high-dose adenosine.In patients with pacemakers who undergo repair of endovascular aortic stent graft, administration of high-dose adenosine is ineffective in producing the required period of asystole; during the action of adenosine, the pacemaker detects an interruption of ventricular systole and stimulates the ventricle. Preoperatively, patients with pacemakers should be seen by a cardiologist or cardiothoracic surgeon to assess the function of the pacemaker. If the patient is not dependent on the pacemaker and the programming capability of the pacemaker is not limited, the pacemaker may be turned off during the perioperative period. If the patient is dependent on the pacemaker or in the rare case of limited programmability of the pacemaker (e.g., minimal rate of ventricular stimulation by the pacemaker is 30 beat/min), other options include (1) temporary perioperative inhibition of the pacemaker during administration of adenosine (which is not a function of all pacemakers);(2) temporary reprogramming of the pacemaker to a subthreshold output to prevent ventricular capture;(3) external chest wall stimulation by an external single-chamber demand pulse generator; or (4) induction of induced hypotension to avoid the need for reprogramming of the pacemaker.External chest wall stimulation offers a convenient way to temporarily inhibit a VVI pacemaker, obviating the need for pacemaker programming. [4,5]To maximize sensing of the external chest wall stimulation, the pacemaker should be programmed to a unipolar VVI mode, and the sensitivity should be maximized. If a unipolar mode is used, both cutaneous electrodes should be positioned over the generator and lead parallel to the cathode/anode vector to optimize the ability of the generator to sense the external signal (Figure 1). [6,7]If a bipolar lead configuration is used, the sensitivity of external stimulation is decreased. External chest wall stimulation may be possible; however, the external cutaneous electrodes should be positioned over the right ventricular apex. In either case, the position of the cutaneous electrodes may need to be adjusted to optimize sensing of the external signal by the pacemaker generator.Previously, this method of external chest wall inhibition has been used to detect underlying rhythms. [4,5,7]This method has been replaced by direct inhibition of the pacemaker via reprogramming in newer generators. Other pacemakers (i.e., dual-chamber pacemakers) may sense external stimuli as atrial or ventricular activity, depending on the orientation of the external electrodes, thus resulting in rapid ventricular pacing. Although most dual-chamber pacemakers have programmable capabilities, only some can be programmed off or set to subthreshold values to eliminate capture. Other dual-chamber pacemakers may require programming to a unipolar VVI mode with subsequent intraoperative external chest wall stimulation to inhibit the pacemaker.Induction of temporary ventricular fibrillation with a transvenous ventricular electrode attached to an alternating current generator is an alternative to adenosine for producing a period of nonpulsatile blood flow in the aorta. [8]We believed that this alternative was too dangerous vis a vis reprogramming the pacemaker, damaging the pacing leads, and possibly inducing tissue damage secondary to burns at the patient's generator site. Alternatively, the mean arterial pressure could have been decreased temporarily using short-acting vasodilator agents during deployment of the stent to minimize the chance of stent graft embolization.We presented a case of a patient undergoing repair of an endovascular aortic aneurysm with an implanted permanent pacemaker that could not be reprogrammed to a mode that would result in temporary inhibition of the pacemaker. Using equipment commonly found in a cardiac or vascular operating room, we described a straightforward technique of temporary inhibition of a pacemaker without the need for reprogramming of the pacemaker.