Initial experience with the Nikkiso centrifugal pump during thoracoabdominal aortic aneurysm repair

Transcription

1 TECHNICAL NOTE Initial experience with the Nikkiso centrifugal pump during thoracoabdominal aortic aneurysm repair Joseph S. Coselli, MD, Scott A. LeMaire, MD, Dwayne F. Ledesma, MD, Satoshi Ohtsubo, MD, Eiki Tayama, MD, PhD, and Yukihiko Nosé, MD, PhDJ Houston, Tex. Purpose: Several centers use atriodistal bypass (ADB) as a protective adjunct against distal ischemia during extensive thoracoabdominal aortic aneurysm (TAAA) repair. Most current ADB circuits use indirect-drive centrifugal pumps. The purpose of this report is to describe our initial clinical experience with the Nikkiso pump, a more compact directdrive centrifugal pump recently developed at Baylor, for ADB during TAAA repair. Methods: The Nikkiso pump was used for ADB perfusion in 10 consecutive patients during graft repair of TAAAs (six Crawford extent I and four extent II). Two patients had aortic dissection. In the four patients who had extent II repairs, selective renal and visceral perfusion was also performed with the Nikkiso pump. Results: No mechanical pump malfunctions or adverse events related to the device occurred. All 10 patients survived and were discharged from the hospital. No patient had paraplegia after surgery. Two patients had delayed lower extremity weakness after undergoing extent I repairs; both recovered and were ambulating at the time of discharge. No complications were associated with bleeding or cerebral, respiratory, renal, or hepatic function. Conclusions: Our initial experience with the Nikkiso centrifugal pump during TAAA repair demonstrated excellent pump function that provided sufficient flow for both distal aortic and selective organ perfusion. The prevention of permanent spinal cord injury and distal organ failure was successful in this group. (J Vasc Surg 1998;27: ) The prevention of postoperative paraplegia and paraparesis after the repair of thoracoabdominal aortic aneurysms (TAAAs) remains a major focus of investigation. Recent clinical data 1-3 support the use of distal aortic perfusion by bypass from the left atrium to the femoral artery or distal aorta as an adjunct to prevent spinal cord ischemia and subsequent neurologic deficits during graft replacement of extensive TAAAs (Crawford 4 extents I and II). Previously, we and others 3,5-8 have reported using an indirect-drive centrifugal pump (Bio-Medicus BP-80, Eden Prairie, Minn.) for atriodistal bypass (ADB) during TAAA repair. From the Department of Surgery, Baylor College of Medicine. Reprint requests: Joseph S. Coselli, MD, Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, TX Copyright 1998 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter /98/$ /4/86255 The Nikkiso HMS-12 pump (HIMEX Production Co., Inc., Houston, Tex.) is a compact, atraumatic, direct-drive centrifugal pump developed in our department and recently approved for clinical use. 9 Excellent results have been described with the Nikkiso pump for cardiopulmonary bypass procedures The use of this new pump for ADB during TAAA surgery, however, has not yet been reported. The purpose of this report is to describe our initial clinical experience with the Nikkiso pump for ADB during repair of extensive TAAAs. PATIENTS AND METHODS Between December 21, 1995, and February 6, 1996, the Nikkiso HMS-12 centrifugal pump was used for ADB perfusion during graft repair of extensive TAAAs in 10 consecutive patients. The median age was 70.5 years (range, 51 to 74 years). Seven men and three women were evaluated. Six patients had extent I TAAAs, and four had extent II TAAAs. Two patients had aortic dissection (one chronic and 378

2 Volume 27, Number 2 Coselli et al. 379 Fig. 1. Nikkiso centrifugal pumphead. Fig. 2. Atriodistal bypass circuit including Nikkiso centrifugal pumphead, inflow and outflow cannulas, and visceral/renal perfusion catheters. one acute with progressive symptoms), and eight patients had chronic nonspecific aneurysms without dissection. No patient had a ruptured aneurysm. Significant preoperative risk factors included hypertension in five patients, chronic obstructive pulmonary disease in four patients, ischemic heart disease in four patients, history of smoking in four patients, renal stenosis documented with angiography in two patients, and evidence of cerebral vascular occlusive disease in two patients. One patient with chronic ischemic cardiomyopathy had extremely poor left ventricular function with an ejection fraction of 18% determined by preoperative echocardiography. Previous operations included abdominal aortic aneurysm repair in one patient, coronary artery bypass and abdominal aortic aneurysm repair in one patient, and replacement of the aortic valve and ascending aorta with coronary artery bypass in one patient. The bypass circuit consisted of inflow and outflow cannulas, 3/8-inch polyvinylchloride tubing, and the Nikkiso centrifugal pump. The pumphead (Fig. 1) has an impeller diameter of 50 mm, a priming volume of 25 ml, and a weight of 145 gm. Six small holes in the impeller prevent stagnation of blood to help reduce thrombosis. The pump was placed remotely from the driver console with a flexible shaft that allowed placement of the pump close to the surgical field. No blood reservoir, heat exchanger, or oxygenator was incorporated in the circuit. The total priming volume of the circuit was 720 ml. For selective visceral or renal perfusion, balloon perfusion catheters were connected to the outflow limb with a three-way stopcock (Fig. 2). By clamping the outflow tube, selective visceral or renal bypass from the left atrium was achieved. The surgical technique, standardized by the author performing all operations (J. S. C.), has been recently described in detail All patients underwent intubation with a double-lumen endotracheal tube to permit deflation of the left lung. The patients were placed in an oblique, lateral decubitus position with the pelvis rotated to the left to allow access to the femoral arteries. Exposure of the aorta was achieved with a left thoracoabdominal incision through the sixth intercostal space and a transperitoneal approach with medial visceral rotation. The inflow cannula, a no. 26 USCI aortic cannula (C.R. Bard, Inc., Tewksberry, Mass.), was inserted into the left atrium and secured with a purse string suture. An 18F to 22F outflow cannula was inserted into the aneurysmal mid-descending thoracic aorta in nine cases and the left common femoral artery in one case; we currently favor the former insertion site because it eliminates the complications associated with femoral artery cannulation. After mild systemic heparinization (1 mg/kg) was performed, ADB was initiated at 500 ml/min, and the proximal aorta was clamped. Flow rates were adjusted to maintain mean distal aortic pressures near 70 mm Hg and mean pulmonary arterial pressures near 20 mm Hg; these parameters are generally achieved at flow rates between 1500 and 2500 ml/min. Sodium nitroprusside was used in conjunction with ADP to maintain normal proximal arterial pressures. The descending aorta was then clamped at a level above the critical intercostal arteries, and the proximal portion of the aneurysm was opened (Fig. 3, A). A cellsaving blood collection system was used to return shed blood to the patient. A woven Dacron tube was used for graft replacement in all cases. After the proximal anastomosis was completed, ADB was discontinued, and the distal aortic clamp was removed. The remainder of the aneurysm was then opened to its distal extent. In the four patients who had aneurysms involving the entire thoracoabdominal

3 380 Coselli et al. February 1998 Fig. 3. Technique of distal perfusion during extent II thoracoabdominal aortic aneurysm repair. Atriodistal bypass is used during initial aortic clamping (A) and performance of proximal anastomosis. Selective visceral and renal perfusion with balloon cannulas is used during reattachment of critical intercostal arteries (B). During reattachment of visceral vessels (C), selective visceral and renal perfusion continues while intercostal arteries, now proximal to distal clamp, receive antegrade perfusion.

4 Volume 27, Number 2 Coselli et al. 381 aorta (extent II), balloon cannulas were inserted into the origins of the celiac axis, superior mesenteric artery, and both renal arteries; selective renal and visceral perfusion was then performed by occluding the outflow tubing and resuming pump flow (Fig. 3, B). Critical intercostal arteries were then attached to the graft as an island in nine patients. The visceral and renal arteries were reattached with either a beveled distal anastomosis (extent I) or Carrel patch (extent II, Fig. 3, C). After the visceral and renal vessels were reattached in extent II repairs, the balloon cannulas were removed, the graft was flushed, and the distal clamp was moved below the visceral arteries, thereby resuming antegrade perfusion during completion of the distal anastomosis. RESULTS All patients underwent ADB without mechanical pump malfunction or adverse events related to the device. The mean total aortic clamp time was 49.6 ± 8.0 minutes, and mean spinal ischemic and visceral/renal ischemic times were 24.3 ± 4.8 minutes and 18.4 ± 5.8 minutes, respectively. The average flow rates for distal aortic perfusion and selective visceral or renal perfusion were 2.4 ± 0.6 L/min and 330 ± 30 ml/min, respectively. No perioperative deaths occurred. No patient had paraplegia after surgery. Two patients had temporary delayed lower extremity weakness after undergoing extent I TAAA repairs; one patient had transient left leg weakness with associated urinary retention on postoperative day 1 and was walking without assistance at the time of discharge, and the second patient had paraparesis on postoperative day 2, responded to treatment that included mannitol and steroids, and was also ambulatory at the time of discharge. Postoperative renal function was maintained within normal range in all patients; the average maximum postoperative serum creatinine level was 1.2 ± 0.3 mg/dl. No patient had coagulopathy or required reexploration because of bleeding. Two patients had left vocal cord paralysis and were successfully treated with type I thyroplasty. 16 Two patients had bradyarrythmias and required pacemaker implants. No complications were associated with cerebral, respiratory, or hepatic function. All patients were discharged from the hospital; the average duration of hospital stay was 14.7 ± 3.1 days. DISCUSSION Patients with extensive TAAAs (extents I and II) are at greatest risk for having ischemic complications of the spinal cord caused by inherently prolonged aortic cross-clamp times. 17,18 Although several investigators advocate various adjunctive methods such as cerebrospinal fluid drainage, 3,19 epidural cooling, 20 profound hypothermic circulatory arrest, 21,22 and intraoperative monitoring of spinal evoked potentials, 23 the effectiveness of these methods remains controversial Our current approach to spinal cord protection includes moderate heparinization, permissive hypothermia, selective use of ADB, and aggressive reattachment of critical intercostal arteries (T8 to L1). We do not use cerebrospinal fluid drainage. As previously reported, the use of ADB during extensive TAAA repairs reduces intercostal arterial ischemic time and reduces the incidence of spinal cord injury. 1-3,5,27 The two cases of delayed lower extremity weakness that occurred in this series were most likely caused by transient postoperative hypoperfusion of the spinal cord rather than intraoperative ischemia. 28 Recent data suggest that ADB may also provide renal protection during TAAA repair. A 1989 retrospective appraisal of Crawford s series, by Svensson et al., 29 did not show such a benefit. Although univariate analysis of their complete experience with 1509 patients undergoing TAAA repair demonstrated a 13% incidence of renal failure when distal perfusion was used compared with 19% without ADB (p = 0.032), multivariate analysis did not identify ADB as a protective factor. 17 The recent report from Safi et al., 30 however, demonstrated that the use of ADB, when used without selective visceral perfusion, was associated with a decreased incidence of acute renal failure after descending thoracic and TAAA repair, whereas the use of simple clamping without perfusion adjuncts was an independent predictor of postoperative renal complications. Their finding that selective visceral or renal perfusion had a detrimental effect on renal function is difficult to explain but may be related to endothelial damage of the renal arteries during catheter placement or balloon inflation. Mesenteric perfusion with ADB and selective perfusion may have several beneficial effects. Mediators released during intestinal ischemia and reperfusion have been implicated in the subsequent development of multiple organ failure. 31 Intestinal ischemia and reperfusion injury may also adversely affect renal perfusion and function. 32 Furthermore, animal studies by Cohen et al and clinical data from Illig et al. 36 have demonstrated an association between visceral ischemia and coagulopathy after supraceliac aortic cross-clamping. Therefore the

5 382 Coselli et al. February 1998 reduced visceral ischemic times provided by ADB may reduce the risks of organ failure and bleeding complications. Additional studies are required to further evaluate these potential benefits of ADB. By unloading the proximal circulation, ADB may also provide cardiac and cerebral protection during aortic cross-clamping. 37 Our patient with a left ventricular ejection fraction of 18% tolerated repair of an extent II TAAA without perioperative cardiac complications, and no patient had perioperative cerebrovascular complications. The original ADB circuits used roller pumps. 38 Centrifugal pumps, introduced 20 years ago, offer several improvements over the roller pumps: less setup time, lower priming volumes, decreased hemolysis, and reduced risk of air embolism. 10,39 Most current reports on ADB describe the use of the Bio-Medicus centrifugal pump, which uses an indirect-drive system with a magnetically coupled impeller-rotor. 2,5-8,37,40,41 The perfusion system introduced in this study is simple and small, with a compact centrifugal pump. The Nikkiso pump, with a priming volume of 25 ml (vs 80 ml, Bio-Medicus) and weight of 145 gm (vs 280 gm, Bio-Medicus), is the smallest and lightest commercially available centrifugal pump. 11,12,39 The use of a flexible shaft permits placement of the Nikkiso pumphead close to the surgical table, thereby further decreasing the total system priming volume. The lack of a heat exchanger in the circuit allows permissive mild hypothermia, providing additional spinal cord protection. 13,21,22,24 We do not use an oxygenator during ADB, as described by Aomi et al. 8 Although the Nikkiso ADB system does not require heparin at flow rates greater than 1.5 L/min, we use moderate heparinization to prevent thrombosis of vessels supplying the spinal cord. In terms of hemolysis, in vitro and in vivo studies 11,39,42,43 have demonstrated that the Nikkiso pump compares favorably and may be superior to both roller pumps and other commercially available centrifugal pumps including the Bio-Medicus model. The antithrombogenic nature of the Nikkiso pump has also been confirmed. 9,42 ADP is also being used for spinal cord protection during repair of traumatic descending thoracic aortic rupture. 44 The characteristics of the Nikkiso ADB circuit such as the ease of air removal and low priming volume, which allow it to be primed quickly, 11 make this system ideal for these often urgent trauma cases. In summary, our initial experience with the Nikkiso centrifugal pump during TAAA repair demonstrated excellent pump function without adverse mechanical events. Despite its small design, the Nikkiso pump provided sufficient flow for both distal aortic and selective organ perfusion. The prevention of permanent spinal cord injury and distal organ failure was successful in this small group. A larger prospective trial comparing the Nikkiso pump with currently accepted devices (i.e., the Bio- Medicus pump) is a logical next step in confirming the safety and effectiveness of this newer pump in the setting of TAAA surgery. REFERENCES 1. Coselli JS. Thoracoabdominal aortic aneurysms: experience with 372 patients. J Cardiovasc Surg 1994;9: Safi HJ, Bartoli S, Hess KR, Shenaq SS, Viets JR, Butt GR, et al. Neurologic deficit in patients at high risk with thoracoabdominal aortic aneurysms: the role of cerebrospinal fluid drainage and distal aortic perfusion. J Vasc Surg 1994;20: Safi HJ, Hess KR, Randel M, Iliopoulos DC, Baldwin JC, Mootha RK, et al. Cerebrospinal fluid drainage and distal aortic perfusion: reducing neurologic complications in repair of thoracoabdominal aortic aneurysm types I and II. J Vasc Surg 1996;23: Crawford ES, Crawford JL, Safi HJ, Coselli JS, Hess KR, Brooks B, et al. 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