Positive Energy Functional for Massless Scalars in Rotating Black Hole Backgrounds of Maximal Ungauged Supergravity.

We outline a proof of the stability of a massless neutral scalar field ψ in the background of a wide class of four dimensional asymptotically flat rotating and "electrically charged" solutions of supergravity, and the low energy limit of string theory, known as STU metrics. Despite their complexity, we find it possible to circumvent the difficulties presented by the existence of ergo regions and the related phenomenon of superradiance in the original metrics by following a strategy due to Whiting, and passing to an auxiliary metric admitting an everywhere lightlike Killing field and constructing a scalar field ψ (related to a possible unstable mode ψ by a nonlocal transformation) which satisfies the massless wave equation with respect to the auxiliary metric. By contrast with the case for ψ, the associated energy density of ψ is not only conserved but is also non-negative.

Helical phase of chiral nematic liquid crystals as the Bianchi VII0 group manifold.

We show that the optical structure of the helical phase of a chiral nematic is naturally associated with the Bianchi VII(0) group manifold, of which we give a full account. The Joets-Ribotta metric governing propagation of the extraordinary rays is invariant under the simply transitive action of the universal cover E(2) of the three-dimensional Euclidean group of two dimensions. Thus extraordinary light rays are geodesics of a left-invariant metric on this Bianchi type VII(0) group. We are able to solve, by separation of variables, both the wave equation and the Hamilton-Jacobi equation for this metric. The former reduces to Mathieu's equation, and the latter to the quadrantal pendulum equation. We discuss Maxwell's equations for uniaxial optical materials where the configuration is invariant under a group action and develop a formalism to take advantage of these symmetries. The material is not assumed to be impedance matched, thus going beyond the usual scope of transformation optics. We show that for a chiral nematic in its helical phase Maxwell's equations reduce to a generalized Mathieu equation. Our results may also be relevant to helical phases of some magnetic materials and to light propagation in certain cosmological models.

Universal area product formulas for rotating and charged black holes in four and higher dimensions.

We present explicit results for the product of all horizon areas for general rotating multicharge black holes, both in asymptotically flat and asymptotically anti-de Sitter spacetimes in four and higher dimensions. The expressions are universal, and depend only on the quantized charges, quantized angular momenta and the cosmological constant. If the latter is also quantized these universal results may provide a "looking glass" for probing the microscopics of general black holes.

Anti-de Sitter-space/conformal-field-theory Casimir energy for rotating black holes.

We show that, if one chooses the Einstein static universe as the metric on the conformal boundary of Kerr-anti-de Sitter spacetime, then the Casimir energy of the boundary conformal field theory can easily be determined. The result is independent of the rotation parameters, and the total boundary energy then straightforwardly obeys the first law of thermodynamics. Other choices for the metric on the conformal boundary will give different, more complicated, results. As an application, we calculate the Casimir energy for free self-dual tensor multiplets in six dimensions and compare it with that of the seven-dimensional supergravity dual. They differ by a factor of 5/4.

Brane worlds in collision.

We obtain an exact solution of the supergravity equations of motion in which the four-dimensional observed Universe is one of a number of colliding D3 branes in a Calabi-Yau background. The collision results in the ten-dimensional spacetime splitting into disconnected regions, bounded by curvature singularities. However, near the D3 branes the metric remains static during and after the collision. We also obtain a general class of solutions representing p-brane collisions in arbitrary dimensions, including one in which the universe ends with the mutual annihilation of a positive-tension and a negative-tension 3 brane.

Rotating black holes in higher dimensions with a cosmological constant.

We present the metric for a rotating black hole with a cosmological constant and with arbitrary angular momenta in all higher dimensions. The metric is given in both Kerr-Schild and the Boyer-Lindquist form. In the Euclidean-signature case, we also obtain smooth compact Einstein spaces on associated S(D-2) bundles over S2, infinitely many for each odd D>/=5. Applications to string theory and M-theory are indicated.

M-theory conifolds.

Seven manifolds of G2 holonomy provide a bridge between M-theory and string theory, via Kaluza-Klein reduction to Calabi-Yau six manifolds. We find first-order equations for a new family of G2 metrics D7, with S3 x S3 principal orbits. These are related at weak string coupling to the resolved conifold, paralleling earlier examples B7 that are related to the deformed conifold, allowing a deeper study of topology change and mirror symmetry in M-theory. The D7 metrics' nontrivial parameter characterizes the squashing of an S3 bolt, which limits to S2 at weak coupling. In general the D7 metrics are asymptotically locally conical, with a nowhere-singular circle action.

Gender and carotid endarterectomy: does it matter?

OBJECTIVE: Multiple large series have retrospectively identified female gender as a risk factor for perioperative stroke and death after carotid endarterectomy (CEA). METHODS: Data for all patients who underwent CEA at a single institution from January 1990 to December 1998 were entered into a computerized vascular registry and form the basis of this report. RESULTS: A total of 1298 CEA procedures were performed, of which 520 (40%) were in women and 778 (60%) in men. The mean age was 69.8 +/- 8.7 years for men and 71.2 +/- 8.5 years for women (P <.001). Cardiac risk factors significantly varied among the two groups, with women more likely to have diabetes (42% vs 36%) and hypertension (77% vs 66%), whereas tobacco history was higher among men (85% vs 71%) (P <.05 for all). Female patients were more likely to be asymptomatic at presentation (men, 44% vs women, 51%; P =.022). Postoperative myocardial infarction occurred in eight patients (0.6%) with no differences between men (0.4%) and women (1.0%) (P = not significant). For all adverse postoperative cardiac events (myocardial infarction, congestive heart failure, or arrhythmia), the incidence was 1.9% (25 patients), again with no differences between men (1.5%) and women (2. 5%) (P = not significant). There were 25 postoperative neurologic events (19 strokes, six transient ischemic attacks) among the entire cohort (1.9%), of which 16 were in men (2.1%) and nine in women (1. 6%; P = not significant). The overall postoperative stroke rate was 1.5% (13 [1.7%] of 778 men; 6 [1.2%;] of 520 women; P = not significant). Total operative mortality was 0.3% (3 [0.4%] of 778 men; 1 [0.2%] of 778 women; P = not significant). Late recurrent stenosis requiring operation developed in 14 patients (1.1%) during follow-up (6 [0.8%] of 778 men; 8 [1.5%] of 520 women; P =.19). CONCLUSIONS: Although there is significant variability in cardiac risk factors and presentation, female gender is not a risk factor for stroke, death, or cardiac morbidity after CEA. Women are not at higher risk for reoperation for recurrent stenosis.

Arm vein conduit is superior to composite prosthetic-autogenous grafts in lower extremity revascularization.

PURPOSE: Various alternative conduits have been used for lower extremity revascularization when an adequate ipsilateral greater saphenous vein is absent. This study compared the effectiveness of all-autogenous multisegment arm vein bypass grafts with that of composite grafts composed of combined prosthetic and autogenous conduits. METHODS: One hundred fifty-three lower extremity revascularization procedures performed between 1990 and 1998 were followed up prospectively using a computerized vascular registry. The grafts were composed of spliced arm vein segments with venovenostomy in 122 and of composite prosthetic-autogenous conduit in 31. Arm vein conduit was prepared by means of intraoperative angioscopy for valve lysis and identification of luminal abnormalities in 47.7% of cases. RESULTS: Bypass graft configurations were as follows: femoropopliteal (12 arm vein, 2 composite); femorotibial (75 arm vein, 23 composite); femoropedal (14 arm vein, 6 composite), and popliteo-tibial/pedal (21 arm vein, 0 composite). The indication for surgery was limb salvage in 98% and disabling claudication in 2% of cases. The mean follow-up was 25.1 months (range, 1 month to 7.9 years). Overall survival at 4 years was 51%. Overall patency and limb salvage rates were as follows: primary patency, at 1 year-arm vein, 76.9% +/- 4.8%; composite, 59. 5% +/- 9.6% (P =.02); at 3 years-arm vein, 70.0% +/- 8.0%; composite, 43.7% +/- 12.4% (P <.01); and at 5 years-arm vein, 53.8% +/- 8.7%; composite, 0%; secondary patency, at 1 year-arm vein, 77.5% +/- 4. 6%; composite, 59.8% +/- 9.5% (P =.02); at 3 years-arm vein, 70.7% +/- 7.5%, composite, 44.9% +/- 13.1% (P <.01); at 5 years-arm vein, 57.7% +/- 8.0%; composite, 0%; limb salvage, at 1 year-arm vein, 89. 3% +/- 3.7%; composite, 73.9% +/- 8.9% (P <.01); at 3 years-arm vein, 80.5% +/- 7.0%; composite, 49.6% +/- 14.3% (P <.01); at 5 years-arm vein, 76.3% +/- 9.9%; composite, 0%. CONCLUSION: In this study, multisegment autogenous arm vein was used successfully in a wide variety of lower extremity revascularization procedures and achieved good long-term patency and limb salvage rates, well in excess of those achieved with composite prosthetic-autogenous grafts. The use of autogenous conduit appears to offer superior results to composite conduit in lower extremity revascularization. The superior durability of arm vein makes it one of the alternative conduits of choice when an adequate greater saphenous vein is not available.

Lower extremity revascularization in diabetes: late observations.

HYPOTHESIS: Despite the success of infrainguinal arterial bypass in diabetic limb and foot salvage, optimism remains guarded because of purported high late mortality and limb loss in patients with diabetes. DESIGN: Inception cohort, with minimum 5-year follow-up. SETTING: Tertiary referral center. PATIENTS: Eight hundred forty-three consecutive patients undergoing lower extremity arterial reconstruction from July 1, 1990, through July 31, 1993. INTERVENTION: Infrainguinal arterial bypass with vein graft. MAIN OUTCOME MEASURES: Graft patency, limb salvage, and survival. RESULTS: A total of 962 vein grafts (843 patients) were performed; 795 grafts (82.6%) were performed in patients with diabetes (DM group) and 167 (17.4%) in nondiabetic patients (NDM group). Average age was 68.4 years, and was lower in the DM group (66.2 [range, 27-92 years] vs. 70.5 years [range, 37-96 years]) (P = .005). Inhospital 30-day perioperative mortality was 1.4%, lower in the DM group (0.9% vs. 4.2%) (P = .005). The target vessel was more frequently infrageniculate in the DM group (87% vs. 77%; P = .002). Five-year primary and secondary graft patencies were 74.7% (DM group, 75.6%; NDM group, 71.9%; P = .80) and 76.2% (DM group, 77.0%; NDM group, 73.6%; P = .90), respectively. The 5-year overall limb salvage rate was 87.1%, also unaffected by diabetes (DM group, 87.3%; NDM group, 85.4%; P = .80). Survival at 5 years was 58.1% overall and virtually identical in the DM (58.2%) and NDM groups (58.0%). CONCLUSIONS: Diabetes mellitus does not influence late mortality, graft patency, or limb salvage rates after lower extremity arterial reconstruction. Concern for longterm mortality and limb loss in diabetic patients is unwarranted and should not prevent aggressive attempts at limb salvage.

The use of arm vein in lower-extremity revascularization: results of 520 procedures performed in eight years.

PURPOSE: The absence of an adequate ipsilateral saphenous vein in patients requiring lower-extremity revascularization poses a difficult clinical dilemma. This study examined the results of the use of autogenous arm vein bypass grafts in these patients. METHODS: Five hundred twenty lower-extremity revascularization procedures performed between 1990 and 1998 were followed prospectively with a computerized vascular registry. The arm vein conduit was prepared by using intraoperative angioscopy for valve lysis and identification of luminal abnormalities in 44.8% of cases. RESULTS: Seventy-two (13. 8%) femoropopliteal, 174 (33.5%) femorotibial, 29 (5.6%) femoropedal, 101 (19.4%) popliteo-tibial/pedal, and 144 (27.7%) extension "jump" graft bypass procedures were performed for limb salvage (98.2%) or disabling claudication (1.8%). The average age of patients was 68.5 years (range, 32 to 91 years); 63.1% of patients were men, and 36.9% of patients were women. Eighty-five percent of patients had diabetes mellitus, and 77% of patients had a recent history of smoking. The grafts were composed of a single arm vein segment in 363 cases (69. 8%) and of spliced composite vein with venovenostomy in 157 cases (30.2%). The mean follow-up period was 24.9 months (range, 1 month to 7.4 years). Overall patency and limb salvage rates for all graft types were: primary patency, 30-day = 97.0% +/- 0.7%, 1-year = 80.2% +/- 2.1%, 3-year = 68.9% +/- 3.6%, 5-year = 54.5% +/- 6.6%; secondary patency, 30-day = 97.0% +/- 0.7%, 1-year = 80.7% +/- 2.1%, 3-year = 70.3% +/- 3.4%, 5-year = 57.5% +/- 6.2%; limb salvage, 30-day = 97.6% +/- 0.7%, 1-year = 89.8% +/- 1.7%, 3-year = 82.1% +/- 3.3%, 5-year = 71.5% +/- 6.9%. Secondary patency and limb salvage rates were greatest at 5 years for femoropopliteal grafts (69.8% +/- 12.8%, 80.7% +/- 11.8%), as compared with femorotibial (59.6% +/- 10. 3%, 72.7% +/- 10.5%), femoropedal (54.9% +/- 25.7%, 56.8% +/- 26.9%, ) and popliteo-tibial/pedal grafts (39.0% +/- 7.3%, 47.6% +/- 15.4%). The patency rate of composite vein grafts was equal to that of single-vein conduits. The overall survival rate was 54% at 4 years. CONCLUSION: Autogenous arm vein has been used successfully in a wide variety of lower-extremity revascularization procedures and has achieved excellent long- and short-term patency and limb salvage rates, higher than those generally reported for prosthetic or cryopreserved grafts. Its durability and easy accessibility make it an alternative conduit of choice when an adequate saphenous vein is not available.

Efficacy of dorsal pedal artery bypass in limb salvage for ischemic heel ulcers.

PURPOSE: Although pedal artery bypass has been established as an effective and durable limb salvage procedure, the utility of these bypass grafts in limb salvage, specifically for the difficult problem of heel ulceration, remains undefined. METHODS: We retrospectively reviewed 432 pedal bypass grafts placed for indications of ischemic gangrene or ulceration isolated to either the forefoot (n = 336) or heel (n = 96). Lesion-healing rates and life-table analysis of survival, patency, and limb salvage were compared for forefoot versus heel lesions. Preoperative angiograms were reviewed to evaluate the influence of an intact pedal arch on heel lesion healing. RESULTS: Complete healing rates for forefoot and heel lesions were similar (90.5% vs 86.5%, P =.26), with comparable rates of major lower extremity amputation (9.8% vs 9.3%, P =.87). Time to complete healing in the heel lesion group ranged from 13 to 716 days, with a mean of 139 days. Preoperative angiography demonstrated an intact pedal arch in 48.8% of the patients with heel lesions. Healing and graft patency rates in these patients with heel lesions were independent of the presence of an intact arch, with healing rates of 90.2% and 83.7% (P =.38) and 2-year patency rates of 73.4% and 67.0% in complete and incomplete pedal arches, respectively. Comparison of 5-year primary and secondary patency rates between the forefoot and heel lesion groups were essentially identical, with primary rates of 56.9% versus 62.1% (P =.57) and secondary rates of 67.2% versus 60.3% (P =.50), respectively. CONCLUSION: Bypass grafts to the dorsalis pedis artery provide substantial perfusion to the posterior foot such that the resulting limb salvage and healing rates for revascularized heel lesions is excellent and comparable with those observed for ischemic forefoot pathology.

Renal insufficiency and altered postoperative risk in carotid endarterectomy.

PURPOSE: Higher complication rates have been reported in patients with renal insufficiency (RI) undergoing peripheral vascular surgery. Little attention has been paid specifically to carotid endarterectomy (CEA) in patients with RI where the risk/benefit considerations are very sensitive to small increases in postoperative complications. METHODS: One thousand one consecutive CEAs performed since 1990 were reviewed from our vascular registry, and 73 CEAs on patients with RI were identified. For comparison, two groups were established: group I (n = 928), normal renal function (creatinine level, <1.5 mg/dL); and group II (n = 73), RI (creatinine level, >/=1.5 mg/dL). RESULTS: Differences in the nonfatal stroke rates and combined stroke and death rates were statistically significant (P <.02) between the groups: group I (1. 08% and 1.18%) and group II (5.56% and 6.94%) respectively. Both groups were similar in regard to operative indications. In addition with the comparison of group I to group II, there was a statistically significant increase in hematoma rate, 1.61% versus 12. 5% ( P <.001), total cardiac morbidity, 1.72% versus 6.94% (P =.003), and total complications, 6.24% versus 36.1% (P =.001). Multivariate analysis demonstrated pre-existing RI to be the only significant predictor for perioperative stroke and hematoma. CONCLUSION: Patients with preoperative RI are at a higher, but not prohibitive, risk for stroke and death after CEA than patients with normal renal function. They are also at risk for hematoma formation, cardiac morbidity, and overall complications. Care in selection of these patients for CEA must be emphasized.

Perioperative strokes after 1001 consecutive carotid endarterectomy procedures without an electroencephalogram: incidence, mechanism, and recovery.

HYPOTHESIS: That alternative methods of cerebral protection, especially routine shunting of all patients undergoing general anesthesia or shunting on the basis of neurologic assessment with the patient awake under cervical plexus block, result in outcomes of carotid endarterectomy comparable with those reported using electroencephalographic monitoring. DESIGN: Retrospective review of cases from a vascular registry established in 1990. SETTING: Tertiary care center. PATIENTS: Consecutive sample of 1001 patients who underwent carotid endarterectomy. INTERVENTIONS: Carotid endarterectomy procedures were performed without electroencephalographic monitoring, using general anesthesia with routine shunting or using regional anesthesia. MAIN OUTCOME MEASURES: Overall stroke and mortality rates and cause and consequence of the postoperative strokes. RESULTS: There were 14 nonfatal strokes (1.4%) and 2 deaths (0.2%), for a combined stroke and death rate of 1.6%. Nine (64%) of the 14 strokes appeared to result from a technical error during the endarterectomy. Mild deficits were noted after 7 strokes (50%), with the remainder resulting in deficits that required inpatient rehabilitation. Twelve patients with strokes (86%) eventually returned home without need for assistance. CONCLUSIONS: Most postoperative strokes in this series were due to technical errors. Overall, even in patients with strokes initially requiring inpatient rehabilitation, there was good recovery of function. Low stroke and mortality rates can be achieved in carotid endarterectomy without the use of electroencephalographic monitoring.

The burden of diabetic foot ulcers.

Lower extremity ulcers represent a major concern for patients with diabetes and for those who treat them, from both a quality of life and an economic standpoint. Studies to evaluate quality of life have shown that patients with foot ulcers have decreased physical, emotional, and social function. Analyses of economic impact have shown (1) the majority of costs occur in the inpatient setting, (2) a lack of financial benefit when comparing primary amputation with an aggressive approach to limb salvaging including vascular reconstruction, and (3) private insurance provides greater reimbursement for inpatient care than does Medicare. Results of etiologic studies suggest that hyperglycemia induces diabetes-related complications through sorbitol accumulation and protein glycation, and the resultant nerve damage manifests as peripheral neuropathy, which predisposes to ulcer development. Patients with diabetes also have an increased incidence of peripheral vascular disease, impaired wound healing, and decreased ability to fight infection. In light of these factors, it is sometimes difficult to determine the optimal course for patient management. This review is aimed at helping healthcare providers make better decisions about treatment, resource use, and strategies for future foot ulcer prevention.

Lower extremity arterial reconstruction in the very elderly: successful outcome preserves not only the limb but also residential status and ambulatory function.

PURPOSE: The purpose of this study was to evaluate our results with lower extremity arterial reconstruction (LEAR) in patients 80 years of age or older and to assess its impact on ambulatory function and residential status. METHODS: We performed a retrospective review of all patients 80 years of age or older undergoing LEAR at a single institution from January 1990 through December 1995. Preoperative information regarding residential status and ambulatory function was obtained from the hospital record and vascular registry. Telephone interviews with patients or next of kin were undertaken to provide information regarding postoperative residential status and ambulatory function. Residential status and level of ambulatory function were graded by a simple scoring system in which 1 indicates living independently, walking without assistance; 2 indicate living at home with family, walking with an ambulatory assistance device; 3 indicates an extended stay in a rehabilitation facility, using a wheelchair; and 4 indicates permanent nursing home, bedridden. Preoperative and postoperative scores for both residential status and ambulatory function were compared. Kaplan-Meier survival curves were generated for graft patency, limb salvage, and patient survival. RESULTS: Two hundred ninety-nine lower extremity bypass operations were performed in 262 patients 80 years of age or older (45% men, mean age 83.6 years, range 80 to 96 years). Sixty-seven percent of the patients had diabetes mellitus. Limb salvage was the indication for operation in 96%. The preoperative mean residential status and ambulatory function scores were 1.79+/-0.65 and 1.55+/-0.66, respectively. The perioperative mortality rate at 30 days was 2.3%. The median length of hospital stay decreased from 16 days in 1990 to 8 days in 1995 (range 4 to 145 days). Eighty-seven percent of grafts were performed with the autologous vein. The 5-year primary, assisted primary, and secondary graft patency rates for all grafts were 72%, 80%, and 87%, respectively. The limb salvage rate at 5 years was 92%. The patient survival rate at 5 years was 44%. The postoperative residential status and ambulatory function scores were 1.95+/-0.80 and 1.70+/-0.66, respectively. Overall scores remained the same or improved in 88% and 78% of patients, respectively. CONCLUSION: LEAR in octogenarians is safe, with graft patency and limb salvage rates comparable to those reported for younger patients. LEAR preserves the ability to ambulate and reside at home for most patients.

Diabetes mellitus: a risk factor for carotid endarterectomy?

PURPOSE: Symptomatic cerebrovascular disease is more common in patients who have diabetes mellitus than in the nondiabetic population, even when matched for associated risk factors. Although the safety and efficacy of carotid endarterectomy has been established by NASCET and ACAS, several small studies have noted an increased rate of perioperative neurologic morbidity in patients with diabetes. METHODS: Data for all patients who underwent carotid endarterectomy at a single institution from Jan. 1990 to Dec. 1995 were prospectively entered into a computerized vascular registry and form the basis of this report. RESULTS: Of 732 carotid endarterectomy procedures performed, 284 (39%) were performed in patients who had diabetes mellitus. Patients with diabetes and without diabetes were matched for clinical presentation (diabetic patients, 45% asymptomatic; nondiabetic patients, 43%) and internal carotid artery percent stenosis (86.6% +/- 10.6% vs 86.4% +/- 10.6%). Patients with diabetes were younger at presentation than patients without (68.8 +/- 8.5 years vs 70.9 +/- 8.5 years; p < 0.005) and were more likely to have a history of coronary artery disease (53% vs 45%; p = 0.04). The mean total length of stay was 6.1 days for patients with diabetes and 4.8 days among patients without (p = 0.01). An adverse postoperative cardiac event (myocardial infarction, congestive heart failure, or arrhythmia) occurred in nine patients with diabetes (3.2%) and in five nondiabetic patients (1.1%; p < 0.05). By logistic regression analysis, however, diabetes was not an independent risk factor for a postoperative cardiac event (p = 0.28). There were 11 perioperative neurologic events (eight cerebrovascular accidents, three transient ischemic attacks) during the entire period (1.5%), of which six were among diabetic patients (2.1%) and five among nondiabetic patients (1.1%; p = NS). Of the eight cerebrovascular accidents, three occurred in diabetic patients (1.0%) and five in nondiabetic patients (1.1%; p = NS). The total operative mortality rate was 0.3% (diabetic patients, 1 of 284, 0.35%; nondiabetic, 1 of 447, 0.2%). CONCLUSIONS: Patients with diabetes who undergo carotid endarterectomy are more likely to have coexisting cardiac disease, which may contribute to a higher incidence of postoperative cardiac morbidity. Diabetes mellitus alone, however, is not a risk factor for postoperative cardiac morbidity in patients who undergo carotid surgery. In addition, carotid endarterectomy may be safely performed in patients with diabetes with neurologic morbidity and mortality rates that are comparable with those of the nondiabetic population

The effect of arterial reconstruction on the natural history of diabetic neuropathy.

OBJECTIVE: To determine whether reversal of hypoxia slows the progression of neuropathy. DESIGN: Cohort study with a mean follow-up of 19.2 months. SETTING: Institutional and private hospital. PATIENTS: A volunteer sample of 55 patients with diabetes (mean age, 62 years; range, 30-74 years; mean duration of diabetes, 21 years; range, 1-57 years) requiring lower-extremity arterial bypass. Twenty-one successfully treated patients were reexamined at the conclusion of the study. Neuropathy and hypoxia were assessed the day before the operation and during the follow-up visit. INTERVENTION: Lower-extremity arterial reconstruction. MAIN OUTCOME MEASURES: Peroneal nerve conduction velocity and transcutaneous oxygen tension. RESULTS: In the leg operated on, the peroneal nerve conduction velocity remained unchanged during the follow-up period (preoperative, mean [+/- SD] 35.79 +/- 6.02 vs postoperative 35.33 +/- 7.51 m/s; P > .05), but deteriorated in the leg not operated on (36.68 +/- 6.22 vs 33.64 +/- 7.30 m/s; P < .05, Wilcoxon signed rank test). Transcutaneous oxygen tension increased in the revascularized extremity (mean [+/- SD] 40.62 +/- 24.76 vs 66.73 +/- 14.89 mm Hg) but remained unchanged in the leg not operated on (56.76 +/- 17.07 vs 62.00 +/- 15.66 mm Hg; P > .05). Of the entire cohort, 5 patients died during the study period. Graft occlusion occurred in 10 (17%) of 59 extremities. Subset analysis disclosed that the preoperative transcutaneous oxygen tension was significantly higher in the successfully revascularized extremities (41.98 +/- 23.58 vs 24.10 +/- 21.50 mm Hg; P < .001). CONCLUSIONS: Reversal of hypoxia halts the progression of diabetic neuropathy, lending further support to the role of hypoxia in the pathogenesis of nerve destruction in diabetes mellitus. Preoperative transcutaneous oxygen tension is lower in patients with bypass failure, but the severity of neuropathy does not affect the outcome of the operation.

Anesthesia type does not influence early graft patency or limb salvage rates of lower extremity arterial bypass.

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 clinical characteristics 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.