Scott A. Seidel

Noninvasive detection of ischemic bowel

PURPOSE Acute mesenteric arterial occlusion is an abdominal catastrophe that carries high morbidity and mortality rates. Current diagnostic methods, however, lack sensitivity and specificity and do not provide information about the viability of the affected bowel. Early diagnosis and intervention would improve patient outcomes and survival rates. The basic electrical rhythm (BER) is the omnipresent electrical slow wave of the gastrointestinal tract that characterizes the underlying electrical activity of the bowel. BER frequency is known to fall with ischemia. Superconducting quantum interference devices (SQUIDs) can detect BER by measuring the magnetic fields generated by the electrical activity of the smooth muscle of the small bowel. The purpose of this study was to determine the ability of a SQUID to detect mesenteric ischemia in a free-lying section of small bowel in an animal model of acute superior mesenteric artery occlusion. METHODS Seven adult male rabbits (six experimental and one control) were studied with transabdominal SQUID and electrode recordings during baseline and after the induction of mesenteric ischemia with balloon occlusion of the superior mesenteric artery. Continuous recordings were taken for 120 minutes of ischemia and analyzed with autoregressive spectral analysis to determine the BER frequency during specific time points of the study. Two independent investigators blinded to the experimental preparation examined the results to determine whether there was decreased BER frequency and thus ischemia. The results are expressed as mean +/- SEM, and paired t tests were used to determine statistical significance. RESULTS BER was detected in all seven animals and fell from 10.7 +/- 0.5 cpm to 7.0 +/- 1.8 cpm after 30 minutes of ischemia in the magnetic channels (P <.05, with t test). The fall in BER was detected by the SQUID in all six experimental animals. The blinded observers correctly identified healthy and ischemic magnetic data recording, with a sensitivity of 94% and specificity of 100%. CONCLUSION SQUIDs can noninvasively detect bowel ischemia early in a free-lying segment of small bowel in this animal model with a high degree of sensitivity and specificity.

Intestinal tachyarrhythmias during small bowel ischemia

The electrical control activity (ECA) of the bowel is the omnipresent slow electrical wave of the intestinal tract. Characterization of small bowel electrical activity during ischemia may be used as a measure of intestinal viability. With the use of an animal model of mesenteric ischemia, serosal electrodes and a digital recording apparatus utilizing autoregressive spectral analysis were used to monitor the ECA of 20 New Zealand White rabbits during various lengths of ischemia. ECA frequency fell from 18.2 +/- 0.5 cycles per minute (cpm) at baseline to 12.2 +/- 0.9 cpm (P < 0.05) after 30 min of ischemia and was undetectable by 90 min of ischemia in all animals. Tachyarrhythmias of the ECA were recorded in 55% of the animals as early as 25 min after ischemia was induced and lasted from 1 to 48 min. Frequencies ranged from 25 to 50 cpm. These tachyarrhythmias were seen only during ischemia, suggesting that they are pathognomonic for intestinal ischemia. The use of the detection of ECA changes during intestinal ischemia may allow earlier diagnosis of mesenteric ischemia.

The Superficial Femoral-Popliteal Vein Graft: A Reliable Conduit for Large-Caliber Arterial and Venous Reconstructions

Vascular surgeons are increasingly called upon to perform arterial reconstructions in patients who have unusable or absent saphenous veins forcing consideration of alternative conduits. Although prosthetic grafts have excellent performance when used as bypasses involving the aorta and its branches, there are clearly circumstances in which autogenous conduits are preferable. The superficial femoral popliteal vein (SFPV) has proven to be an outstanding alternative in these situations. Although the SFPV was originally used at our institution for the treatment of aortic graft infections, the success of reconstructions for this indication has led us to utilize the SFPV conduit in many other situations. The SFPV has proven to be superior to prosthetic grafts for infrainguinal limb salvage procedures and for hemodialysis access in certain situations. In addition, the SFPV appears to be the conduit of choice for use in infected fields of all types and for large caliber venous reconstructions. The purpose of this article is to review the use of the SFPV conduit in creation of the neoaortoiliac system (NAIS), update our results, and survey alternative uses for this versatile conduit. We also address the technical details of its harvest and implantation technique.