Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
Introduction: New surgical techniques for AAA repair involve transfemoral endovascular placement of an aortic graft [1,2] and require specific anesthetic considerations which have not been previously described. We report our experience from a study comparing conventional surgical repair of a AAA with this new minimally invasive technique to alert anesthesia providers to potential problems and considerations.
Methods: A review of data from 12 patients in an ongoing prospective IRB approved study revealed important information regarding anesthetic requirements and complications. The surgical technique involves femoral arterial exposure under regional anesthesia (epidural or continuous spinal). A device is used to deploy a graft into the aneurysmal aortic segment. For successful deployment, a decrease in mean arterial pressure (MAP) to 60-70 mmHg is necessary. After the graft is appropriately positioned under fluoroscopic guidance inside the aneurysmal lumen, it is secured in place by inflating a balloon within the graft, projecting hooks into the aortic wall. Anesthetic management consisted of 2 large bore intravenous (IV) lines, neuraxial blockade with sedation, and backup plans for general anesthesia. Arterial, central venous and occasionally pulmonary arterial pressures were monitored. MAP was brought to the "target" level through the combined effects of sedation, regional sympathectomy and IV nitroglycerin (NTG). MAP, heart rate, estimated blood loss (EBL), hemodynamic perturbations, complications, recovery period and duration of hospital stay were analyzed.
Results: Of 12 patients, one required an open procedure to complete graft placement and one was transferred to the SICU due to a large concealed groin hemorrhage, requiring multiple blood transfusions. He subsequently required surgical drainage of a retroperitoneal hematoma from the arterial groin bleed, unrelated to the graft system. Average preoperative MAP was 113 +/- 11 mmHg, necessitating a projected average decrease of 53 mmHg to obtain a target MAP of 60 mmHg for device deployment (-47%). The average MAP achieved during graft deployment was 73 +/- 7 mmHg (-40 mmHg or -35%). In 3 of 12 patients (25%), arterial manipulation and endovascular balloon inflation caused a marked and unexpected bradycardia requiring urgent treatment. Two of these patients had a profound decrease of 30 and 38 beats per minute (bpm), and one patient had a 15 bpm drop to 48 bpm. The median EBL was 200 ml (range = 100-1600 ml), the median post-anesthesia care unit (PACU) stay was 6 hours, and the median hospitalization was 3 days.
Discussion: Patients with AAA frequently have associated hypertension and coronary artery disease.  Due to technical aspects of the procedure, patients must be able to tolerate a significant reduction in MAP. The resulting organ perfusion pressures may exclude some patients from being appropriate candidates for this technique. In 25% of patients a profound bradycardia, probably reflex in nature, occurred unexpectedly during arterial manipulation or intravascular balloon inflation. Although this response is familiar to endovascular surgeons, the mechanism for this reflex is unknown. Prior reports of this procedure indicate predominant use of general anesthesia. Regional neuraxial blockade is an acceptable analgesic technique and aids in decreasing MAP for graft deployment, but one must be ready to treat sudden hemodynamic changes, occult blood loss, and convert to general anesthesia for open repair if necessary. PACU and hospital length of stay are favorable for this new minimally invasive technique.
1. N Engl J Med 1997;336:13-20
2. J Vasc Surg 1996;23:543-53
3. Ann Vasc Surg 1986;1:36-42