February 1998

Anesthesia Type Does Not Influence Early Graft Patency or Limb Salvage Rates of Lower Extremity Arterial Bypass
Pierce ET, Pomposelli FB, Stanley GD, Lewis KP, Cass JL, LoGerfo FW, Gibbons GW, Campbell DR, Freeman DV, Halpern EF, Bode RH;
J Vasc Surg 1997;25:226-233
[ see abstract below ]

Dr. Robert H. Bode, Jr et al, in a 1996 Anesthesiology article*, presented an analysis of cardiac morbidity and mortality using general vs. spinal versus epidural. Now, in the J Vasc Surg 1997, he is senior author of a paper which reanalyzes that same population looking for evidence of anesthesia choice affecting graft thrombosis. Only about half of the original 423 patient study population had the additional data required for analysis.

In brief, there was no obvious difference. Graft thrombosis rates were low in all groups, and the power to detect a significant difference would have required many thousands of patients. All groups had 30 day graft patency approaching 90-95%. The ability of anesthetic technique to affect thrombosis rates when surgical outcome is excellent is limited. Even if a statistical difference could be shown, it would be small at best.

This paper deserves comment as we routinely offer vascular surgery patients epidural anesthesia as the first choice anesthetic given previous publications suggesting that regional anesthesia affects thrombosis. These articles found that epidural anesthesia was superior to general.

Why are the results different here? There are many possible reasons.

First, this paper is retrospective in nature, so its conclusions are suspect, especially since half the patients were not included. But the lost patients seem to be evenly divided among the groups. Still, the retrospective nature weakens the conclusions

All of these patients received prophylactic low dose subcutaneous heparin postoperatively followed by warfarin. That was not necessarily true in the other studies. All of these patients received PA catheters and were monitored in the ICU for 48 hours (which isn't done anywhere in the world for fem pops as a routine). The closer monitoring, more appropriate fluid management guided by PA catheters might have also played a part.

The surgeon could have been different (i.e. better). We all know all surgeons are not alike in technical expertise. Finally, the previous studies did not account for surgical considerations (i.e. who was at highest risk of occlusion) based on surgical diagnostic factors. This paper did and showed their groups were alike, and claim that this was insufficiently addressed in the anesthesiology papers.

Uncertainty in medical practice, variability in outcome, and the difficulty in deciding exactly what is the right approach for any given patient , continues to plague our efforts to define the best clinical care pathways for common procedures.

* Bode Rh Jr, Lewis KP, Zarich SW, Pierce ET, Roberts M, Kowalchuk GJ, et al. Cardiac outcome of general and regional anesthesia: comparison of general and regional anesthesia. Anesthesiology 1996;84:3-13.

Return to the Current Literature Review Front Page , or read the abstract:

ABSTRACT

PURPOSE: The effect of anesthesia type on 30-day graft patency and limb salvage rates was evaluated in patients who underwent femoral to distal artery bypass.

METHODS: Of 423 patients randomly assigned to receive general, spinal, or epidural anesthetic, 76 did not meet protocol standards and 32 had inadequate anesthesia. A chart review of the remaining 315 patients was undertaken to obtain surgical information not recorded in the original study. All patients were monitored with radial and pulmonary artery catheters. After surgery, patients were in a monitored setting for 48 to 72 hours and had graft function assessments hourly during the first 24 hours and then every 8 hours until discharge.

RESULTS: Fifty-one patients were lost to follow-up (15 general, 22 spinal, 14 epidural). Baseline clinicalcharacteristics were similar for the three groups except prior carotid artery surgery, which was more common in the spinal group. Indications for surgery were also similar except for a higher incidence of nonhealing ulcer in the epidural group. There were no differences among groups for 30-day graft patency with or without reoperation, 30-day graft occlusion, death, amputation, or length of hospital stay.

CONCLUSION: These results suggest that the type of anesthetic given for femoral to distal artery bypass does not significantly affect 30-day occlusion rate, limb salvage rate, or hospital length of stay.