Lower Extremity Regional Anesthesia and Infrainguinal Bypass Grafting

Background The post-operative benefits of regional anesthesia have been described in patients undergoing vascular access surgery(1, 2). Some of the benefits that have been identified are improved vascular flow, decreased thrombosis rates, and early maturation of grafts(2). It is speculated that these benefits can be mainly attributed to sympathetic blockade by regional anesthesia. Recent literature review has not identified any prior studies which have attempted to prospectively identify if there are improved surgical outcomes in patients undergoing revascularization surgery when regional anesthesia is utilized. However, Kashyap et al. reported that regional anesthesia may decrease the incidence of perioperative thrombosis in patients who had undergone infra-popliteal revascularization surgery over a 20 year period(3). In this investigation we will attempt to ascertain whether or not there will be improved surgical outcomes namely a reduction in the rates of death, wound infection, graft thrombosis, graft revision, and amputation. As well, we anticipate that patients who have undergone regional anesthesia for infrainguinal bypass grafting will have improved secondary outcomes with respect to a decreased length of stay, narcotic consumption, nausea and vomiting, post-operative cognitive dysfunction, major cardiac events, post-operative pain, and hyperglycemic episodes.

Methods After Investigational Review Board approval, written informed consent will be obtained from 20 patients undergoing fem-popliteal bypass surgery at University of Nebraska Medical Center and enrolled in our prospective cohort registry. Patients will be excluded from the study if age is less than 19 years, allergies to amide anesthetics, inability to undergo general anesthesia, acute limb ischemia, any existence of contraindications to regional anesthesia in the presence of antiplatelet or anticoagulative drugs, or evidence of gross neurological dysfunction of the lower extremity. Baseline health data of the patient will be recorded. Ultrasound will be performed with a linear 10- to 13-Megahertz probe while performing the nerve block. Standard American Society of Anesthesiology monitors will be applied and the patient sedated at the discretion of the anesthetic team. Complications such as vascular puncture, pain on injection, or systemic toxicity will be recorded. A perineural dosing regimen for the regional blocks will be as follows: (femoral block) 20cc of 0.5% ropivicaine and (sub-gluteal posterior sciatic block) 20cc of 0.2% ropivicaine. Epinephrine will be withheld from the local anesthetic in order to prevent the potential of further ischemic complications. The patient will then undergo general anesthesia at the discretion of the anesthetic team. Any anesthetic or surgical complication will be recorded during the OR interval. The type of graft utilized and specific location of arterial intervention will be recorded.

Following surgery, the patient will be monitored and data recorded daily while the patient is recovering in the hospital. Primary outcomes which will be recorded include: death, wound infection, graft thrombosis, graft revision, and amputation. Secondary outcomes which will be recorded are pain scores, nausea and vomiting, 24 hour narcotic consumption, graft failure (defined as any occlusion requiring return to operating room), any related return to the OR for the index procedure, any major adverse cardiac events (MACE), administration of warfarin or antiplatelet medications, average 24 hour blood sugar, creatinine levels, postoperative cognitive dysfunction, and requirement of supplemental oxygen upon discharge from the PACU. As well, the patient will be queried for resumption of tobacco products. The patient's length of hospital stay will be recorded.

On discharge there will be continued surveillance for the following primary outcomes: death, wound infection, graft thrombosis, graft revision, and amputation. The secondary outcomes which will be recorded are as follows: presence of pain at rest, pain on ambulation, continued administration of anticoagulants or antiplatelets, graft failure (defined as any occlusion requiring return to operating room), any related return to the OR for the index procedure, any major adverse cardiac events (MACE), average 24 hour blood sugar, creatinine levels, and all ankle brachial pressure index (ABPI) and doppler ultrasound reports will be recorded. Also, patients will be queried for resumption of tobacco products. These observations will be recorded on post-operative day 7, 31, and 93.

A comparison group of patients (N=20) who have undergone infra-inguinal bypass grafting will be obtained from retrospective chart review. Patients who have undergone regional or neuroaxial anesthesia for their bypass procedure will be excluded. As well, patients will be matched to their cohorts by age, sex, health comorbidities including: Congestive heart failure, smoking, diabetes, and renal dysfunction, and chronic anticoagulants or antiplatelet medication administration. The same primary and secondary outcome data obtained in the prospective portion of this study will be sought and recorded by chart review.

Conclusion Improved vascular surgical outcomes have been described in patients receiving regional anesthesia and neuroaxial anesthesia(2-4). Specifically, we anticipate a decrease in overall rates of death, wound infection, graft thrombosis, graft revision, and amputation in patients receiving regional anesthesia for infra-inguinal bypass grafting. As well, we hypothesize that patients receiving regional anesthestics will have improved secondary outcomes including decreased length of stay, narcotic consumption, nausea and vomiting, post-operative cognitive dysfunction, cardiac events, post-operative pain, and hyperglycemic episodes.