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Biomedical subjects

A D Shepard

Publications and source records attributed to A D Shepard.

At least 19 recordsLinked to original sources
PubMed2002

Hypothenar hammer syndrome: an uncommon and correctable cause of digital ischemia.

Hypothenar hammer syndrome (HHS) is the rare entity of finger ischemia secondary to embolic occlusion of the digital arteries as a result of repetitive trauma to the palmar ulnar artery. We report the case of a young man found to have digital embolic complications from an ulnar artery aneurysm. This is thought to have developed as a result of palmar trauma experienced during military rifle drill exercises.

Adolescent↗
PubMed2001

Analysis of coagulation changes associated with supraceliac aortic crossclamping using thromboelastography.

INTRODUCTION: The etiology of the coagulation changes seen with supraceliac (SC) aortic crossclamping (AXC) remains controversial; both primary fibrinolysis and clotting factor consumption have been implicated. The cause of these changes was investigated with thromboelastography (TEG), a test that measures the viscoelastic properties of thrombus to dynamically assess coagulation and fibrinolysis. METHODS: Eight pigs underwent SC AXC for 30 min; 5 pigs undergoing 30 min of infrarenal (IR) aortic clamping served as controls. Blood was drawn before AXC, before unclamping, and 5 and 60 min after unclamping. Thromboelastography and standard coagulation tests [prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and platelet count] were performed. Measured TEG parameters included fibrinolytic index (a measure of fibrinolysis), r value (a reflection of intrinsic coagulation cascade activity), and the alpha angle and K values (measures of the speed of solid clot formation). Repeated measures ANOVA and t test were used for statistical analysis. RESULTS: There was no difference in the fibrinolytic index at any time point between the two groups. Increased activity of the intrinsic coagulation cascade during SC clamping was reflected by a lower R value just before unclamping (12.6 +/- 3.0 vs 20.0 +/- 3.0, P = 0.048) compared to IR AXC. Decreased speed of solid clot formation was noted 5 min after unclamping in the SC group but not the IR group [as defined by an increased K value (ANOVA, P = 0.010) and a decreased alpha angle value (ANOVA, P = 0.005)]. Fibrinogen levels were lower in the SC than in the IR group 5 (P = 0.013) and 60 min after unclamping (P = 0.02), but PT, PTT, and platelets did not differ between the groups at any time points. CONCLUSIONS: Thirty minutes of SC AXC does not result in fibrinolysis. There is increased clotting activity during SC clamping followed by decreased speed of clot formation and decreased fibrinogen levels after unclamping. These changes are consistent with clotting factor consumption.

Animals↗
PubMed2001

Factors affecting outcome in proximal abdominal aortic aneurysm repair.

Sixty-five consecutive patients undergoing nonemergent repair of an abdominal aortic aneurysm (AAA) originating above the visceral and/or renal arteries were studied to determine operative results and identify factors influencing outcome of proximal AAA repair. Factors associated with postoperative morbidity were analyzed using multivariate analysis. There were no postoperative deaths, paraplegia/paraparesis, or symptomatic visceral ischemia. Proximal AAA repair can be accomplished with acceptable mortality. If renal artery bypass or reimplantation is anticipated, cold renal perfusion may protect against renal dysfunction. Postoperative pulmonary dysfunction can be reduced by avoiding radial division of the diaphragm.

Adult↗
PubMed2000

Phosphorus 31 nuclear magnetic resonance spectroscopy suggests a mitochondrial defect in claudicating skeletal muscle.

OBJECTIVE: Decreased oxygen supply is generally accepted as the primary cause of muscle dysfunction in patients with peripheral arterial occlusive disease (PAOD) and intermittent claudication, although reported morphologic changes in the mitochondria of claudicating muscle suggest that impaired energy utilization may also play a role. With the measurement of the phosphate-rich compounds of muscle energy metabolism (adenosinetriphosphate [ATP], adenosinediphosphate [ADP], and phosphocreatine [PCr]) and pH, phosphorus P 31 magnetic resonance spectroscopy ((31)P MRS) provides a unique, noninvasive method to investigate this hypothesis further. METHODS: Calf muscle bioenergetics were studied in 12 men with moderate claudication (ankle-brachial index >/=0.5 and </=0.8) and 14 normal control subjects with the use of (31)P MRS and standard treadmill testing. Phosphorus MRS evaluation of the superficial posterior calf muscles was carried out with a 90-second submaximal isometric plantar flexion exercise. This mild exercise was chosen to permit in-magnet testing and to allow study of intrinsic mitochondrial efficiency under conditions of unchallenged blood flow. Phosphocreatine and ADP recovery time constants (t.c.), two very sensitive measures of oxidative mitochondrial function, as well as intracellular pH and ATP production via anaerobic glycolysis were determined during three exercise sessions and the results averaged and compared to known values obtained from a control population. RESULTS: During the (31)P MRS protocol, the end exercise intracellular pH (7.11 +/- 0.01 vs 7.11 +/- 0.01) and ATP production by anaerobic glycolysis (0.13 +/- 0.05 vs 0.14 +/- 0.03 mmol/L per second) were no different in PAOD patients versus control subjects, confirming that the protocol exercise did not significantly reduce oxygen supply. Phosphocreatine and ADP recovery t.c. (137 +/- 41 vs 44 +/- 3 seconds and 60 +/- 10 vs 29 +/- 2 seconds, respectively) were significantly slower than normal (P <.05, t test). There was, however, no correlation between these measures of mitochondrial function and any treadmill parameter (P >.5, Pearson moment correlation). CONCLUSIONS: Phosphorus 31 MRS provides the first direct evidence of defective energy metabolism in the mitochondria of claudicating calf muscle. This defect appears to be independent of both arterial flow and the severity of occlusive disease in patients with mild to moderate claudication. Coupled with documented ultrastructural and DNA abnormalities in the mitochondria of claudicating skeletal muscle, these data provide evidence for a secondary cause of muscle dysfunction in intermittent claudication.

Adenosine Diphosphate↗
PubMed2000

Visceral pseudoaneurysms due to pancreatic pseudocysts: rare but lethal complications of pancreatitis.

OBJECTIVE: Erosion of pancreatic pseudocysts into adjacent vessels is a rare but highly lethal cause of intra-abdominal hemorrhage. Percutaneous angiographic embolization (PAE) of the bleeding artery has recently been advocated as the preferred therapy. This study was undertaken to survey the outcome after treatment of this complication and to make recommendations for its management. METHODS: An 11-year retrospective analysis was performed of all patients treated at a large tertiary care referral center for visceral artery pseudoaneurysms associated with pancreatic pseudocysts. RESULTS: From 1988 to 1998, 256 patients were admitted for complications of pancreatic pseudocysts. Sixteen patients (11 men and 5 women) were identified in whom a pseudocyst had eroded into a major blood vessel with hemorrhage or development of a false aneurysm. The mean age was 45 years (range, 23-67 years). Active bleeding was present in 13 patients, whereas three had evidence of recent hemorrhage. Ten of 16 patients initially underwent operative therapy, four elective and six emergency, whereas six stable patients were initially treated with PAE. Technical failures of the initial treatment or secondary complications required both therapeutic modalities in six patients, which resulted in 13 total surgical interventions and 10 PAEs. The surgical morbidity rate was 62% (8 of 13), whereas that of PAE was 50% (5 of 10). Three deaths occurred after emergency operations, two of which failed to stop the bleeding, accounting for all of the deaths in the series (3 [19%] of 16). A trend was noted toward increased death with necrotizing pancreatitis (P =.07) and emergency surgery (P =.06). Ranson's criteria were not found to be predictive of death in this series. Surgical drainage procedures were required in seven (44%) of 16 patients for infections (n = 3) or mass effect of the pseudoaneurysm (n = 3). The mean size of pseudoaneurysms that required operative intervention for secondary complications was 13.9 cm, compared with 7.7 cm for all others in the series (P =.046). Long-term follow-up was available in all 13 survivors at a mean of 44 months (range, 1-108 months). CONCLUSIONS: The management of pancreatic pseudocyst-associated pseudoaneurysms remains a challenging problem with high morbidity and death rates. Operation and PAE play complementary management roles. PAE is recommended as the initial therapy for hemodynamically stable patients. Surgery should be reserved for actively bleeding, hemodynamically unstable patients; for failed embolization; and for other secondary complications such as infection or extrinsic compression.

Adult↗
PubMed1999

31P MRS studies of exercising human muscle at high temporal resolution.

Methods for measuring mitochondrial activity from 31P magnetic resonance spectroscopy data collected during and after exercise were compared in controls, weight lifters, and peripheral vascular occlusive disease (PVOD) patients. There were trends toward increasing mitochondrial activity during exercise in order from PVOD patients, moderately active controls, highly active controls, to weight lifters. Results from PVOD patients show divergence of some measures due to 1) the non-exponential nature of phosphocreatine recovery, and 2) potential breakdown of [ADP] control of the mitochondria due to lack of oxygen (for Qmax calculation). These results demonstrate the utility of obtaining and directly analyzing high time resolution data rather than assuming monoexponential behavior of metabolite recovery.

Adenosine Diphosphate↗
PubMed1997

Noninvasive venous testing in the diagnosis of pulmonary embolism: the impact on decisionmaking.

PURPOSE: To characterize the use and utility of lower extremity noninvasive venous testing (NIVT) in the diagnosis of pulmonary embolism (PE). METHODS: The study is a retrospective case series of consecutive patients in whom PE was suspected who were referred to a large, urban tertiary care center for NIVT. The main outcome measures of the study were the rate of positive results of NIVT, the amount of new information provided by NIVT, and the frequency of management changes that were attributable to NIVT. RESULTS: Forty-one of 450 patients (9%) had deep venous thrombosis (DVT) by NIVT. The prevalence of DVT by NIVT among patients not evaluated by ventilation/perfusion (V/Q) scanning was 8%. The prevalence of DVT by NIVT among patients with a high-probability V/Q scan result before NIVT was 39%, but no management decisions in this group were based on a positive NIVT result and only two decisions were based on negative NIVT results. The prevalence of DVT according to NIVT among patients who had a negative "diagnostic" (low, or very low probability, or normal) result of V/Q scan before NIVT was 2%. The overall frequency of management changes attributed to NIVT was only 2.5%. In the remaining 97% of patients, management was determined by the result of V/Q scanning or of subsequent pulmonary arteriography. CONCLUSIONS: In patients in whom PE is suspected, results of NIVT are usually negative for acute DVT. Management decisions are almost always based on V/Q scan or results of pulmonary arteriography and not on NIVT. The utility of NIVT to identify DVT in these patients appears limited, and a more selective approach to its application for the diagnosis of PE should be considered.

Acute Disease↗
PubMed1996

Surgical complications of transaxillary arteriography: a case-control study.

PURPOSE: The purpose of this study was to review the complications of transaxillary arteriography (TRAX), determine clinical factors associated with their occurrence, and define optimal treatment methods. METHODS: A retrospective review of 842 consecutive TRAX studies performed in a large, urban, tertiary care, academic medical center was undertaken. Patients with complications were compared with a concurrent randomized control group without complications with the use of a multivariate analysis model. Results of operative therapy for nerve injury were compared with those of nonoperative therapy. RESULTS: Nineteen (2.3%) complications were identified including 14 nerve injuries, four expanding hematomas/pseudoaneurysms without neurologic deficit, and one puncture site thrombosis. Several statistically significant or suggestive findings associated with the occurrence of complications were identified: female sex (odds ratio [OR] = 4.7), systolic blood pressure > or = 150 mm Hg at the conclusion of TRAX (OR = 9.5), periprocedural systemic heparin anticoagulation (OR = 7.9), concomitant use of intraarterial thrombolysis or percutaneous angioplasty (OR = 12.0), and duration of procedure > or = 90 minutes (OR = 4.0). Patients who underwent prompt exploration (< or = 4 hours from symptom onset) for nerve injuries were more likely to have complete resolution of their neurologic deficits (five of six patients) than those who were observed or underwent delayed operation (three of eight patients) (OR = 8.3). CONCLUSIONS: Aggressive treatment of post-TRAX hypertension, limitation of TRAX duration, delay of postprocedure anticoagulation, and use of alternative sites for arterial puncture in female patients or patients undergoing catheter-based intervention may reduce the incidence of TRAX-related complications. In patients who have neurologic deficits prompt surgical exploration of the puncture site with decompression of the involved nerve(s) may reduce the incidence of prolonged deficits.

Aneurysm, False↗
PubMed1994

Acute aortic occlusion. A 40-year experience.

OBJECTIVE: To review a large experience with acute aortic occlusion (AAO) to better define the cause, clinical presentation, treatment, prognostic variables, and outcome. DESIGN: Retrospective review of 46 consecutive patients with AAO during a 40-year period. SETTING: A large urban tertiary care referral center in Detroit, Mich. PATIENTS: Adult patients with arteriographic and/or operative confirmation of acute occlusion of the abdominal aorta plus signs and symptoms of acute ischemia. INTERVENTION: Operative and nonoperative treatment of AAO. MAIN OUTCOME MEASURES: Mortality, morbidity, and long-term survival. Other variables measured included cause, risk factors, and effects of duration and severity of ischemia and treatment methods on outcome. RESULTS: Two primary causes were identified--embolism (65%) and thrombosis (35%). Heart disease and female gender were risk factors for embolism, while smoking and diabetes were risk factors for thrombosis. Severity of ischemia on presentation correlated better with outcome than duration of ischemia. The hospital mortality rate was 35% and morbidity, 74%, with no difference between the two groups. Recurrent arterial embolism occurred in 43% of patients with embolic AAO. Seventy-two percent of AAO survivors were alive 5 years after therapy. CONCLUSIONS: Acute aortic occlusion remains a serious vascular surgical emergency with significant morbidity and mortality, even when recognized promptly and treated appropriately. Nevertheless, survivors have a reasonable long-term outcome. Permanent anticoagulation is suggested in patients with embolic AAO to minimize a high incidence of recurrent arterial embolism.

Acute Disease↗
PubMed1994

Results of lower extremity amputations in patients with end-stage renal disease.

PURPOSE: The purpose of this study was to determine the impact of end-stage renal disease (ESRD) on the outcome of patients undergoing lower extremity (LE) amputation. METHODS: Hospital charts and vascular surgery registry data were reviewed for all patients who underwent LE amputation over a consecutive 56-month period. The results of 84 patients with ESRD (137 amputations) were compared with 375 patients (442 amputations) without ESRD. RESULTS: Hospital mortality rate was significantly greater in patients with ESRD than patients without ESRD, 24% versus 7% (p = 0.001). Patients with ESRD undergoing minor amputations had mortality rates three times greater than patients without ESRD undergoing major LE amputations. In patients with ESRD requiring bilateral or unilateral above-knee amputation hospital mortality rates were 43% and 38%, respectively. In addition, patients with ESRD were seven times more likely to undergo bilateral amputation than patients without ESRD over a mean follow-up period of 17 months. No kidney transplant patients died after amputation. CONCLUSION: ESRD has a profound negative impact on morbidity, mortality, and survival rates after LE amputation. Attempts at prevention of amputation with aggressive foot care and patient education in this high-risk group should be the focus of therapy.

Adult↗
PubMed1994

Groin lymphatic complications after arterial reconstruction.

PURPOSE: The purpose of this study was to better define the associated risks and optimal management of groin lymphatic complications (GLC) after femoral artery reconstructive operations. METHODS: Retrospective review of a vascular surgery registry for the last 15 years identified 2679 arterial operations requiring a groin incision. Forty-one GLC were recognized, 28 lymphocutaneous fistulas (LF) and 13 lymphoceles. RESULTS: The incidence of GLC was 1.5% per patient or 1.2% per incision. The highest incidence of GLC was in patients having an aortobifemoral bypass for aneurysmal disease in a previously operated groin (8.1% per patient) and in those undergoing an isolated femoral procedure in a previously operated groin (5.3%). The lowest frequency of GLC was after femoropopliteal/tibial bypasses (0.5%). Twenty-nine patients (71%) were treated without operation with bedrest, intravenous antibiotics, and aggressive local wound care. Operative therapy with wound reexploration attempted identification and control of the leak site, and meticulous wound closure was used in 12 patients (29%). Lymph fistulas in patients undergoing reoperation (10/28) resolved sooner than in patients treated without operation (18/28) (9 +/- 3 days vs 24 +/- 3 days). Infectious wound complications with one resultant graft infection developed in five of 18 patients with LF who did not undergo reoperation. There were no wound or graft infections in the patients in the LF group treated with operation. Operative exploration of lymphoceles did not reduce hospital stay or infectious wound complications. Repetitive lymphocele aspiration did not affect rapidity of resolution or increase the infectious complications. CONCLUSION: GLC remain a troublesome complication of femoral arterial reconstruction. Early reoperation should be performed once a LF is diagnosed. Treatment for lymphoceles should be individualized, with neither operative nor nonoperative management showing clear superiority.

Aged↗
PubMed1993

Repair of pararenal abdominal aortic aneurysms. An analysis of operative management.

OBJECTIVE: To analyze different operative approaches for repair of pararenal abdominal aortic aneurysm, to define factors associated with perioperative morbidity, particularly renal insufficiency, and to compare the results of pararenal abdominal aortic aneurysm repair with standard infrarenal repair. DESIGN: Case series review of all patients undergoing repair of nonruptured pararenal abdominal aortic aneurysms over 7 consecutive years at a tertiary care teaching hospital. PATIENTS: Fifty-three consecutive patients with nonruptured atherosclerotic pararenal abdominal aortic aneurysms undergoing operative repair. A comparison group of 65 patients randomly selected from a pool of 384 patients undergoing concurrent infrarenal abdominal aortic aneurysm repair. MAIN OUTCOME MEASURES: Operative morbidity and mortality, postoperative renal insufficiency, estimated blood loss, perioperative blood and fluid requirements, and length of hospital stay. RESULTS: Postoperative renal insufficiency was more likely when concomitant renal revascularization was performed (P = .007) or when any major intraoperative complication occurred (P = .008). Retroperitoneal abdominal aortic aneurysm repair was associated with lower estimated blood loss (P = .05) and less fluid requirement within the first 24 hours following operation than transperitoneal repair (P = .03). No differences in outcome measures were identified with regard to site of proximal aortic clamping (supraceliac vs suprarenal). Pararenal abdominal aortic aneurysms were larger and their repair was associated with greater estimated blood loss (P = .007), intraoperative blood replacement (P < .001), and a longer hospital stay (P = .02) than infrarenal abdominal aortic aneurysms. CONCLUSIONS: Pararenal abdominal aortic aneurysm repair is a technically challenging operation associated with significant morbidity. A retroperitoneal approach facilitates repair. The site of proximal aortic cross-clamping should be dictated by technical factors and not by any perceived outcome advantages.

Acute Kidney Injury↗
PubMed1993

Supraceliac aortic cross-clamping: determinants of outcome in elective abdominal aortic reconstruction.

PURPOSE: A 7-year experience in which 43 patients underwent supraceliac aortic cross-clamping (SC-AXC) during elective abdominal aortic reconstruction was reviewed. METHODS: Operation was performed for abdominal aortic aneurysm (AAA) in 29 (68%) patients, aortoiliac occlusive disease in seven (16%), proximal anastomotic AAA in three (7%), "shaggy" aorta syndrome in three (7%), and in situ grafting of a previously ligated aorta in one (2%) patient. The indications for supraceliac control included pararenal AAA origin (25), pararenal aortic atherosclerosis (18), inflammatory AAA (2), and a short infrarenal aortic stump (1). Vital organ ischemic complications (VOICs) were defined as any major ischemic complication involving the liver, kidneys, bowel, or spinal cord. RESULTS: The incidence of VOICs was significantly increased when concomitant renal or visceral revascularization (CRVR) was required (p = 0.002) and correlated with an increasing SC-AXC time (p = 0.015). In patients undergoing CRVR (n = 16) the perioperative mortality rate was 25%; VOICs developed in six patients and included renal failure (3), mesenteric/colonic ischemia (3), hepatic ischemia with coagulopathy (2), and spinal cord ischemia (1). In contrast, in those not requiring CRVR (n = 27), SC-AXC was well tolerated. There were no VOICs and no deaths; morbidity rate was 33%. CONCLUSIONS: The incidence of VOICs associated with the use of SC-AXC is primarily related to the level of preoperative renal or mesenteric insufficiency, the severity of pararenal aortic atherosclerosis, the extent of the operative procedure, and the duration of proximal aortic cross-clamping. In complex abdominal aortic reconstruction in which infrarenal aortic control is either not possible or deemed hazardous, SC-AXC is a safe and valuable technique for achieving proximal control.

Aged↗
PubMed1993

Outpatient duplex scanning for deep vein thrombosis: parameters predictive of a negative study result.

PURPOSE: Although clinical examination has been reported to be unreliable in the diagnosis of deep vein thrombosis (DVT), this conclusion has often been derived from hospitalized patients (HP) and may not be applicable in an outpatient setting. This study was undertaken to define clinical parameters that might predict the diagnostic value of emergency venous duplex scanning (VDS). METHODS: Venous duplex scans performed over a 9-month period (interval I) in 154 outpatients (154 limbs) and 145 HP (145 limbs) with suspected DVT were reviewed. RESULTS: Eighteen percent of scans of outpatients and 31% of scans of HP were interpreted as positive for lower extremity DVT. With stepwise logistic regression analysis, criteria predictive of a negative result of outpatient VDS included (1) duration of symptoms greater than 7 days (p = 0.003), (2) thigh circumference difference relative to the uninvolved side of less than 3 cm (p = 0.001), and (3) no history of neoplasia (p = 0.03). This model, when applied prospectively to 68 outpatients (68 limbs) over the next 5 months (interval II), yielded a negative predictive value (NPV) of 96.7% (sensitivity 90.9%, specificity 50.9%, positive predictive value 26.3%). Of the 222 outpatients examined during intervals I and II, 98 (44%) met these three clinical criteria. Three of these 98 outpatients had DVT on VDS and thus would have been misclassified as having a negative result. With a similar logistic regression analysis for HP, clinical criteria achieved an NPV of only 75% (sensitivity 36%, specificity 90%, positive predictive value 62%). CONCLUSION: Clinical assessment is unreliable in the diagnostic evaluation of HP with suspected DVT. In an outpatient population, however, clinical evaluation with the above criteria achieved an NPV of 96.7% in the diagnosis of DVT. These parameters may be useful as guidelines in determining the appropriateness of emergency outpatient VDS.

Ambulatory Care↗
PubMed1991

Management of infected aortoiliac aneurysms.

A 30-year retrospective review identified 13 patients treated for infected aneurysms of the abdominal aorta or iliac arteries, for an overall incidence of 0.65%. A constellation of clinical findings led to the correct preoperative diagnosis in 11 (85%) of 13 patients. Treatment methods included resection and in situ replacement grafting in seven patients, resection and extra-anatomic bypass in five patients, and resection-ligation in one patient. Four (31%) of 13 patients died within 30 days of operation, three of whom died of rupture. Overall, good results were achieved in five patients (38%), while poor results were noted in the remaining eight patients (62%). The determinants of outcome were aneurysm location or rupture, the presence of established infection, and the virulence of the infecting organism. In 10 (77%) of the 13 aneurysms, Salmonella species, Bacteroides fragilis, Staphylococcus aureus, and Pseudomonas aeruginosa accounted for all deaths, ruptures, and suprarenal aneurysm infections. These data suggest that patients with primary infections of the abdominal aorta or iliac arteries continue to present with advanced infections or aneurysm rupture that result in a high mortality.

Adult↗