The Use of Temporary Vascular Shunts as a Damage Control Adjunct in the Management of Wartime Vascular Injury

BACKGROUND

While the use of vascular shunts as a damage control adjunct has been described in series from civilian institutions no contemporary military experience has been reported. The objective of this study is to examine patterns of use and effectiveness of temporary vascular shunts in the contemporary management of wartime vascular injury.

MATERIALS

From September 1, 2004 to August 31, 2005, 2,473 combat injuries were treated at the central echelon III surgical facility in Iraq. Vascular injuries were entered into a registry and reviewed. Location of shunts was divided into proximal and distal, and shunt patency, complications and limb viability were examined.

RESULTS

There were 126 extremity vascular injuries treated. Fifty-three (42%) had been operated on at forward locations and 30 of 53 (57%) had temporary shunts in place upon arrival to our facility. The patency for shunts in proximal vascular injuries was 86% (n = 22) compared with 12% (n = 8) for distal shunts (p < 0.05). All shunts placed in proximal venous injuries were patent (n = 4). Systemic heparin was not used and there were no shunt complications. All shunted injuries were reconstructed with vein in theater and early viability for extremities in which shunts were used was 92%.

CONCLUSIONS

Temporary vascular shunts are common in the management of wartime vascular injury. Shunts in proximal injuries including veins have high patency rates compared with those placed in distal injuries. This vascular adjunct represents a safe and effective damage control technique and is preferable to attempted reconstruction in austere conditions.

Upper extremity vascular injury: a current in-theater wartime report from Operation Iraqi Freedom

Past wartime experience and recent civilian reports indicate upper extremity (UE) vascular injury occurs less often and with less limb loss than lower extremity (LE) injury. Given advances in critical care, damage control techniques, and military armor technology, the objective of this evaluation was to define contemporary patterns of UE injury and effectiveness of vascular surgical management in UE vascular injury during Operation Iraqi Freedom (OIF). From 1 September 2004 through 31 August 2005, 2,473 combat-related injuries were treated at the central echelon III surgical facility in Iraq. Patients with UE vascular injuries upon arrival were reviewed. Vessels injured were delineated. Therapeutic interventions, early limb viability, and complication rates following vascular repair were recorded. Of casualties treated during the study period, 43 (1.7%) UE and 83 (3.3%) LE vascular injuries were identified. Of the UE injuries, 11 (26%) had been operated on at forward locations and six (14%) had temporary shunts in place upon arrival at our facility. Injury levels included 10 (23%) subclavian-axillary, 25 (58%) brachial, and 10 (23%) distal to the brachial bifurcation. Two patients had multilevel injury. Twenty-eight grafts were placed, and 10 vessel repairs and eight ligations were performed. Two (4.7%) brachial interposition grafts required removal due to infection. Four (9.3%) subacute brachial graft thromboses occurred. Four (9.3%) patients underwent early UE amputation. In this most recent U.S. military evaluation of wartime UE vascular injury, UE injury appears rare, with LE injury twice as frequent. Yet, UE limb loss appears more substantial than noted previously. These findings are likely related to significant tissue destruction occurring with the combined mechanisms of injury sustained in OIF.

Echelons of Care and the Management of Wartime Vascular Injury: A Report From the 332nd EMDG/Air Force Theater Hospital, Balad Air Base, Iraq

The objective of this report is to provide a contemporary in-theater account on the systematic management of wartime vascular injury. Included are strategies at each echelon of care that affect the treatment of these injuries. In addition, the aim of this report is to present a modern wartime vascular registry describing rates and distribution of injury in what is now a mature military conflict. A 15-month review (September 1, 2004 through December 1, 2005) from the central level III echelon facility in Iraq (332nd EMDG/Air Force Theater Hospital) presented by the in-theater Consultants for Vascular Surgery. During this period 13 460 casualties were treated at or evacuated through our location, 3096 (23%) with battle-related injuries. Vascular injuries comprised 6.6% (N = 209) of battle-related trauma in the following distribution: extremity 79% (n = 166), neck 13% (n = 27), thoracoabdominal 8% (n = 16). Three levels (formerly echelons) of care are active in theater each with strategies that affect vascular injury management: Level 1: use of commercial tourniquets; level 2: use of temporary vascular shunts as damage control adjuncts; and level 3: definitive repair of arterial and venous injuries in theater using autologous vein. Evacuation patterns and the position of the Air Force Theater Hospital have allowed the formation of a contemporary wartime vascular registry. The rate of vascular injury appears increased compared to that of Vietnam with extremity injuries most prevalent. Effective strategies are in place at each of 3 levels of care that affect the management of vascular injury.

Endothelial Dysfunction After Lactated Ringerʼs Solution Resuscitation for Hemorrhagic Shock

BACKGROUND

Endothelial dysfunction is presumed to occur after hemorrhagic shock and resuscitation. This study uses a novel large-animal model to evaluate the effects of diverse resuscitation regimens on endothelial function.

METHODS

Twenty-seven adult domestic pigs (Sus scrofa) were used in this study. Control pigs (n = 3) underwent instrumentation alone. The remaining pigs experienced controlled hemorrhagic shock to a mean arterial blood pressure of 30 +/- 5 mm Hg for 45 minutes. Pigs were resuscitated to their baseline mean arterial blood pressure +/-5 mm Hg with either shed blood (SB; n = 8), lactated Ringers solution (40 mL/kg) followed by shed blood (LRSB; n = 8), or lactated Ringers solution alone (LR; n = 8). At baseline, 1 and 4 hours after resuscitation, acetylcholine (5, 10, and 15 microg/min) was infused into the proximal iliac artery to measure endothelial dependent relaxation (EDR). Sodium nitroprusside was infused to determine endothelial independent relaxation at the end of the study to insure smooth muscle vasomotor integrity. External iliac artery luminal diameter was measured using motion-mode ultrasonography. Statistical analysis was performed using repeated-measures analysis of variance with Tukey's post-hoc analysis.

RESULTS

All pigs survived the experiment. Pigs required ninefold more resuscitation with LR (370.58 +/- 29 mL/kg) versus SB (41.45 +/- 3.5 mL/kg) or LRSB (76.4 +/- 1.1 mL/kg) (p < 0.05). EDR for LR pigs 1 hour after initiation of resuscitation (R1) was 70.4 +/- 14.4% compared with 94.2 +/- 13.4% for SB and 106.1 +/- 8.2% for LRSB (p < 0.05). At 4 hours after resuscitation (R4), systolic luminal diameters were larger in the SB (0.45 +/- 0.01 cm) and LRSB (0.51 +/- 0.02 cm) groups compared with LR (0.41 +/- 0.03 cm) (LRSB versus LR; p = 0.01). At R4, EDR for the LR group was 78.3 +/- 10.7% compared with SB (101.4 +/- 8.3%) and LRSB (106.4 +/- 7.4%) (p < 0.05). Infusion of sodium nitroprusside confirmed integrity of smooth muscle vasorelaxation. Analysis of serum nitric oxide levels revealed decreased values after resuscitation with LR (9.44 +/- 0.76 mol/L) compared with SB (26.3 +/- 7.8 mol/L) and LRSB (16.3 +/- 1.0 mol/L) (p = not significant).

CONCLUSION

This is the first description of a large-animal model to evaluate EDR after hemorrhagic shock. Resuscitation with LR requires significantly larger volumes than SB or LRSB. LR resuscitation leads to endothelial dysfunction, as determined by decreased EDR, versus SB or LRSB. Resuscitation with blood products may preserve nitric oxide bioactivity when compared with crystalloid resuscitation in the setting of hemorrhagic shock.

Resuscitation with a blood substitute causes vasoconstriction without nitric oxide scavenging in a model of arterial hemorrhage

BACKGROUND

The purpose of this study was to determine if a hemoglobin-based oxygen carrier, HBOC-201 (Hemopure, Biopure Corp), alters endothelial function and nitric oxide physiology when used for hemorrhagic shock.

STUDY DESIGN

Female swine (Sus scrofa) underwent catheterization of the femoral, circumflex iliac, and pulmonary arteries. Control animals (n = 3) underwent instrumentation only. Study animals underwent hemorrhage to mean arterial pressure of 30 +/- 5 mmHg, were maintained for 45 minutes, and resuscitated to the baseline mean arterial pressure for 4 hours. Resuscitation fluids included: shed blood (SB) (n = 8), lactated Ringers plus shed blood (LRSB) (n = 8), and HBOC (n = 8). At baseline, 1, and 4 hours after resuscitation, acetylcholine was infused into the proximal iliac artery and endothelial-dependent relaxation was measured with M-mode ultrasonography. Nitric oxide levels were determined using a chemiluminescent assay.

RESULTS

HBOC, SB, and LRSB provided equivalent survival and resuscitation as measured by mean arterial pressures (65.3 +/- 2.48 mmHg); pulmonary artery mean pressures (15.8 +/- 0.84 mmHg); and lactate levels (1.22 +/- 0.19 mmol/L). HBOC group animals required the lowest resuscitation volume (SB, 41.5 +/- 3.5 mL/kg; LRSB, 76.4 +/- 1.1 mL/kg, HBOC, 14.6 +/- 2.1 mL/kg, p < 0.001). Response to acetylcholine was normal in the SB and LRSB groups, but the HBOC group had diminished acetylcholine response (29.5% endothelial-dependent relaxation end resuscitation, p < 0.001). Arterial nitric oxide levels did not differ between study groups (p = 0.69).

CONCLUSIONS

HBOC might be an alternative resuscitation agent in patients with hemorrhagic shock. Resuscitation with HBOC requires less volume than blood or crystalloid. These data suggest HBOC-201 has a vasoconstrictive effect that cannot be attributed soley to nitric oxide scavenging.

Preservation of renal function with surgical revascularization in patients with atherosclerotic renovascular disease

OBJECTIVE

Clinical and anatomic factors predictive of a favorable response to renal revascularization performed for renal function salvage remain poorly defined. To clarify decision making in such patients we reviewed a contemporary experience of surgical renal artery revascularization (RAR) performed primarily for preservation of renal function.

METHODS

Between June 1990 and March 2001 (ensuring 1 year minimum follow-up), 96 patients with renal insufficiency (serum creatinine [Cr] concentration >or=1.5 mg/dL) and hypertension underwent RAR for preservation of renal function. Study end points included early and late renal function response, progression to dialysis dependence, and long-term survival. Variables potentially associated with these end points were assessed with univariate analysis, Cox regression analysis, and logistic regression analysis, and survival was assessed with the Kaplan-Meier method.

RESULTS

Perioperative failure of RAR occurred in 3 patients (3%), with perioperative mortality in 4 patients (4.1%); thus 92 patients were available for long-term follow-up (mean, 39 months). Mean patient age was 70 +/- 9 years with a mean baseline Cr of 2.6 mg/dL (range, 1.5-7.8 mg/dL). Operative management consisted of aortorenal bypass in 38% of patients, extraanatomic bypass in 38% of patients, and endarterectomy in 24% of patients; 32% of patients required combined aortic revascularization and RAR, and 27% underwent bilateral RAR. At hospital discharge renal function had improved (20% decrement in Cr) in 41 (43%) patients, including 7 patients who were removed from dialysis; remained unchanged in 40 (41%) patients; and declined (20% increase in Cr) in 15 (16%) patients. At last follow-up renal function was either improved or unchanged in 72% of patients. Predictors of a favorable response to RAR at last follow-up included stable Cr at hospital discharge (odds ratio [OR], 7.1; 95% confidence interval [CI], 2.5-21.8; P =.0004) and decreased Cr at hospital discharge (OR, 16; 95% CI, 1.6-307.8; P <.0001); bilateral renal artery repair (OR, 3.1; 95% CI, 0.9-10.6; P =.07) approached clinical significance. Predictors of worsened excretory function at last follow-up included decline of renal function at hospital discharge (OR, 28.9; 95% CI, 5.0-165.4; P =.0002), intervention to treat unilateral renal artery stenosis (OR, 3.8; 95% CI, 0.8-16.6; P =.05), and level of baseline Cr (OR, 3.0; 95% CI, 1.0-4.0; P =.04). Progression to dialysis occurred in 16 (17%) patients. Dialysis-free survival at 5 years was 50%, and overall actuarial survival at 5 years was 59%. Predictors of progression to dialysis during follow-up included treatment of complete renal artery occlusion (OR, 6.2; 95% CI, 1.3-29.5; P =.02), early failure of RAR (OR, 3.1; 95% CI, 0.7-14.2; P =.04) and baseline Cr (OR, 2.9; 95% CI, 1.3-6.1; P =.006).

CONCLUSION

Long-term clinical success in the preservation of renal function, noted in 70% of patients, can be predicted by the initial response to RAR and by anatomic factors, in particular, bilateral repair. While extreme (mean Cr >or=3.2 mg/dL) renal dysfunction generally is predictive of poor long-term outcome, a subset of patients will experience favorable results, even to the extent of rescue from dialysis. These results may facilitate clinical decision making in the application of RAR for renal function salvage.

Acute aortic dissection: population-based incidence compared with degenerative aortic aneurysm rupture

OBJECTIVES

To ascertain whether acute aortic dissection (AAD) remains the most common aortic catastrophe, as generally believed, and to detect any improvement in outcomes compared with previously reported population-based data.

PATIENTS AND METHODS

We determined the incidence, operative intervention rate, and long-term survival rate of Olmsted County, Minnesota, residents with a clinical diagnosis of AAD initially made between 1980 and 1994. The incidence of degenerative thoracic aortic aneurysm (TAA) rupture was also delineated. We compared these results with other population-based studies of AAD, degenerative TAA, and abdominal aortic aneurysm (AAA) rupture.

RESULTS

During a 15-year period, we identified 177 patients with thoracic aortic disease. We focused on 39 patients with AAD (22% of the entire cohort) and 28 with TAA rupture (16%). The annual age- and sex-adjusted incidences were 3.5 per 100,000 persons (95% confidence interval, 2.4-4.6) for AAD and 3.5 per 100,000 persons (95% confidence interval, 2.2-4.9) for TAA rupture. Thirty-three dissections (85%) involved the ascending aorta, whereas 6 (15%) involved only the descending aorta. Nineteen patients (49%) underwent 22 operations for AAD, with a 30-day case fatality rate of 9%. Among all 39 patients with AAD, median survival was only 3 days. Overall 5-year survival for those with AAD improved to 32% compared with only 5% in this community between 1951 and 1980.

CONCLUSIONS

In other studies, the annual incidences of TAA rupture and AAA rupture are estimated at approximately 3 and 9 per 100,000 persons, respectively. This study indicates that AAD and ruptured degenerative TAA occur with similar frequency but less commonly than ruptured AAA. Although timely recognition and management remain problematic, these new data suggest that recent diagnostic and operative advances are improving long-term survival in AAD.

Durability of aortouniiliac endografting with femorofemoral crossover: 4-year experience in the Evt/Guidant trials

OBJECTIVES

We evaluated mid-term results of the multicenter EVT/Guidant aortouniiliac endograft (AI) trial and ascertained the durability of this endovascular technique in patients unable to undergo standard bifurcated endografting.

METHODS

From November 1996 to December 1998, 121 patients were enrolled to receive the AI device on the basis of complex iliac artery anatomy contraindicating bifurcated endografting. Clinical data were centrally collected, and radiographic data were evaluated by core facility.

RESULTS

AI placement was technically successful in 113 of 121 patients. At operation, patients who underwent AI had significantly more arrhythmias, congestive heart failure, and peripheral occlusive disease (P <.05) compared with patients who underwent open aneurysmorrhaphy in the EVT/Guidant trials, indicating comorbid features in this anatomic cohort. Distal AI attachment was performed to the external iliac artery in 40 (36%) patients. Median follow-up was 38 months. In the AI group, overall aneurysm diameter decreased over the duration of study from 54.4 +/- 9.6 mm to 44.4 +/- 16.4 mm (P =.004). At 24 and 36 months after repair, reduction in aneurysm size was associated with absence of endoleak (P =.003 and P =.008, respectively). Aneurysms shrunk or remained stable in 109 (96.5%) patients. Endoleak was identified in 52.3% of patients at discharge, and at follow-up in 30.9% at 1 year, 34.8% at 2 years, 28.6% at 3 years, and 30.4% at 4 years. Type II endoleak predominated. Leak from failure to completely occlude contralateral iliac flow accounted for 8 of 58 endoleaks (13.8%) at discharge. Sixteen patients (14.2%) underwent postoperative endoleak treatment; in one of these patients open conversion was necessary at 20 months. Post-procedure thigh or buttock claudication developed in 16 patients (14.2%). Thirteen patients (81.3%) had either distal attachment in the external iliac artery or contralateral type IIA occlusion. Fifteen patients (13.3%) required intervention because of reduced limb flow; one of these patients underwent open conversion at 27 months, and another underwent axillofemoral grafting at 28 months. Device migration was confirmed in 2 (1.8%) patients, without current clinical sequelae. Whereas no femorofemoral graft thromboses occurred, graft infection developed in 3 patients (2.6%). During follow-up, aneurysm in 2 patients ruptured. Late death occurred in 41 patients (36.3%). Twenty-four patients (58.5%) died of cardiopulmonary disease; one death was endograft-related after aneurysm rupture; and one death was related to femorofemoral bypass infection. Actuarial survival was 78.4% (95% confidence interval [CI], 71%-86%) at 2 years and 63.4% (95% CI, 54%-73%) at 4 years.

CONCLUSIONS

In patients with significant comorbid conditions and complex iliac anatomy unfavorable for bifurcated endografting, AI with femorofemoral bypass grafting is safe and effective. In most patients this endovascular option provides satisfactory mid-term results.

Rapidly enlarging iliac aneurysm secondary to listeria monocytogenes infection: a case report

Infected aneurysms caused by Listeria monocytogenes are rare. Worldwide, 16 cases have been reported, none in the iliac system. The authors report the case of an 80-year-old man being followed for small aortic and right common iliac artery (RCIA) aneurysms who presented with progressive gastrointestinal symptoms. Serial computed tomography demonstrated a 200% increase in RCIA diameter with development of infection over 1 month. Right axillobifemoral bypass and aneurysm resection were performed. The authors believe this case represents the first description of bacteremic seeding of an iliac degenerative aneurysm by Listeria monocytogenes. The natural history and aggressive course of vascular infection with this organism are documented.

Late aortic and graft-related events after thoracoabdominal aneurysm repair

PURPOSE

Unlike abdominal aortic aneurysm repair, little information exists regarding aortic-related morbidity (synchronous/metachronous aneurysm or graft-related complications) after thoracoabdominal aneurysm (TAA) repair. This study was performed to define such events and identify factors related to their development.

METHODS

Over a 15-year interval, 333 patients underwent TAA repair (type I, n = 90; 27%; type II, n = 59; 18%; type III, n = 118; 35%; and type IV, n = 66; 20%). Late aortic events were defined as aortic disease causing death or necessitating further intervention or graft-related complications (infection, pseudoaneurysm, branch occlusion) after hospital discharge. Variables were assessed for their association with aortic events with Cox proportional hazards regression.

RESULTS

In-hospital mortality occurred in 28 patients (8.4%), which left 305 available for follow-up (mean length of follow-up, 26 months; interquartile range, 2.7 to 38.4 months). After TAA repair, aneurysm remained in 60 patients (19.7%; ascending/arch, n = 41; 68.3%; discontinuous infrarenal, n = 12; 20%; contiguous descending, n = 7; 11.7%; contiguous abdominal, n = 4; 6.7%). Events occurred in 33 individuals (10.8%) at 30 +/- 27 months after surgery. Twenty-four patients (73% of events; 7.9% of cohort) had aortic-related events, including another elective aneurysm repair (n = 16), urgent/emergent aneurysm operation (n = 5), acute dissection (n = 2), and atherothrombotic embolization (n = 1). Nine patients (27% of events; 2.9% of cohort) had graft-related incidents, including renovisceral occlusion (n = 5), visceral patch pseudoaneurysm (n = 2), graft infection (n = 2), and graft-esophageal fistula (n = 1). Variables independently predictive of events were female gender (odds ratio [OR], 2.3; P =.03), initial aneurysm rupture (OR, 4.8; P =.04), partial disease resection (OR, 4.2; P =.0008), and expansion of remaining aortic segments on imaging surveillance (OR, 2.5; P =.03). The event-free survival rates were 96% (95% CI, 93% to 98%) and 71% (95% CI, 60% to 83%) at 1 and 5 years.

CONCLUSION

Late aortic events occur in at least 10% of patients after TAA repair and are usually the result of native aortic disease in remote (or noncontiguous) aortic segments. Graft-related complications, in particular, degeneration of inclusion anastamoses, are rare. Female gender, original presentation with rupture, and unresected disease identify those at highest risk. These findings verify the anatomic durability of TAA repair and suggest indefinite aortic surveillance is indicated for those at risk of events.

Thoracoabdominal aneurysm repair: results with 337 operations performed over a 15-year interval

OBJECTIVE

To review perioperative results and late survival after thoracoabdominal aneurysm repair (TAA), in particular to assess the impact over time of epidural cooling (EC) on spinal cord ischemic complications (SCI).

SUMMARY BACKGROUND DATA

A variety of operative approaches and protective adjuncts have been used in TAA to minimize the major complications of perioperative death and SCI. There is no consensus with respect to the optimal approach.

METHODS

From January 1987 to November 2001, 337 consecutive TAA repairs were performed by a single surgeon. Clinical features included prior aortic grafts in 97 (28.8%) and emergent operation in 82 (24.6%), including rupture in 46 (13.6%) and dissection in 63 (19%). Operative management consisted of a clamp/sew technique with adjuncts in 93%. EC (since July 1993) to prevent SCI was used in 194 (57.6%) repairs. Variables associated with the end points of operative mortality and postoperative SCI were assessed with the Fisher exact test and logistic regression; late survival was estimated with the Kaplan-Meier method.

RESULTS

Operative mortality was 8.3% and was associated with nonelective operation, intraoperative hypotension, total transfusion requirement, and the postoperative complications of paraplegia, renal failure, and pulmonary insufficiency. Postoperative renal failure and transfusion requirement were independent correlates of mortality. SCI of any severity occurred in 38 of 334 (11.4%) operative survivors, with 22/38 (6.6% of cohort) sustaining total paraplegia. EC reduced the risk of SCI in patients with types I-III TAA (10.6% vs. 19.8%, =.04). Independent correlates of SCI over the entire study interval included types I/II TAA, rupture, cross-clamp duration, sacrifice of T9-L1 intercostal vessels, and intraoperative hypotension. Late survival rates at 2 and 5 years were 81.2 +/- 3% and 67.2 +/- 5%.

CONCLUSIONS

EC has decreased the risk of SCI after TAA repair. Decreasing the substantial proportion (nearly 25%) of patients requiring nonelective operation will improve results. Late survival is equal to that after routine AAA repair, indicating that the considerable resource expenditure required for TAA repair is worthwhile.

Evolving experience with thoracic aortic stent graft repair

PURPOSE

We reviewed our initial thoracic aorta (TA) stent graft experience in 28 patients from the perspective of treatment with homemade devices (Dacron over Gianturco Z stents; 14 cases) and a commercial device (Excluder; W.L. Gore Co, Flagstaff, Ariz; 14 cases).

METHODS

From November 1996 to August 2001, 28 patients with a spectrum of disease (degenerative aneurysm, n = 18; chronic dissection, n = 4; pseudoaneurysm, n = 3, with 1 trauma and 2 anastomotic; intramural hematoma, n = 2; and coarctation, n = 1) underwent TA stent grafting. Clinical parameters included a mean age of 71 years, 12 female (43%) and 16 male (57%) patients, 14 of 28 patients (50%) with major comorbidities that prohibited open repair, and nine of 28 patients (32%) with urgent or ruptured conditions. Seven patients (25%) needed open surgical access to the aorta or iliac artery for either concomitant abdominal aortic aneurysm repair (n = 3) or device deployment (n = 4), and six of 28 patients (21%) needed left subclavian-carotid transposition to provide for an adequate proximal fixation site. Focal (<15 cm) grafts were used in 19 patients, and the remaining patients had at least two thirds of their descending aorta excluded.

RESULTS

The procedural mortality rate was 3.5% (1/28 patients); three additional deaths, (1 device-related) occurred during the mean follow-up period of 17 months. Access artery complications occurred in six of 28 patients (21%), with one fatal. No immediate or late open conversions were performed. One patient needed urgent dilation and stenting of a collapsed stent graft 3 weeks after deployment. Serious systemic complications included temporary dialysis (n = 1), congestive heart failure (n = 1), and unstable angina (n = 1). Complete exclusion of the TA lesion was noted in 27 of 28 cases (96%). No cases of spinal cord ischemia were noted. Ease and accuracy of deployment was superior for the second generation (commercial) device.

CONCLUSION

TA stent graft repair, although in evolution, appears to be a safe and effective alternative to open repair for many patients with a spectrum of TA disease. Prospective trials for individual diseases will be necessary to define its ultimate role.

Extracranial cerebrovascular revascularization for chronic ocular ischemia

We investigated the demographics, presentation, and outcome of patients undergoing cerebrovascular reconstruction for chronic ocular ischemia (COI) at a single institution through a review of 17 patients over a 9-year period. A total of 558 extracranial cerebrovascular reconstructions were performed during the period of study. Seventeen patients (3%) suffered symptoms of COI. There were 19 symptomatic eyes and 15 asymptomatic eyes. Two patients suffered bilateral symptoms. Eighteen (95%) symptomatic eyes experienced rapidly degenerating global visual acuity, and one suffered bright-light amaurosis. Concomitant ocular pathology was present in 10 (59%) patients, consisting of glaucoma (n = 4), cataracts (n = 4), diabetic retinopathy (n = 3), and macular degeneration (n = 1). Symptomatic eyes were found to have significantly worse ipsilateral internal carotid artery (p = 0.004), external carotid artery (p = 0.002), aortic arch branch disease (p = 0.04), and vertebral artery disease (p = 0.04). All 17 reconstructions treated ipsilateral disease. Twelve patients (70.6%) had significant bilateral disease at the time of operation. Three patients underwent staged contralateral reconstruction. Following revascularization, subjective visual improvement or stabilization occurred in 16 patients (94%). A single patient worsened after developing acute narrow angle glaucoma in the perioperative period. Worse cerebrovascular disease is present ipsilateral to symptomatic eyes. When revascularization is performed, arrest of progression or improvement of symptoms occurs in most patients.

Short-term treatment with transdermal nicotine affects the function of canine saphenous veins

Experiments were designed to determine the effects of nicotine treatment on the functions of saphenous veins used for coronary artery bypass grafts in dogs. Dogs received either no treatment or transdermal nicotine for 5 weeks at doses of 11 mg, 22 mg or 44 mg/day. Saphenous veins were removed and suspended for the measurement of isometric force in organ chambers. Endothelium was removed mechanically from some rings. N(G)-mono-methyl-L-arginine (L-NMMA; 10(-4) M) was used to inhibit the production of nitric oxide. Contractions to alpha2-adrenergic stimulation were decreased in veins from dogs treated with a 22-mg/day dose of transdermal nicotine. In addition, endothelium-dependent relaxations to adenosine-diphosphate (10(-8)-10(-4) M) and the calcium ionophore A23,187 (10(-8)-10(-6) M) were decreased in veins from dogs with a 22-mg/day dose and increased in veins from dogs treated with a 44-mg/day dose. These relaxations were inhibited by L-NMMA. Plasma concentrations of oxidized products of nitric oxide were decreased only in dogs treated with 22 mg/day of nicotine. The relaxation of rings without endothelium (direct response on the smooth muscle) to nitric oxide were not altered by nicotine treatment. These results suggest that the short-term treatment of dogs with intermediate (22 mg/day) but not low (11 mg/day) or high (44 mg/day) doses of transdermal nicotine decreases the endothelial function of veins used for coronary artery bypass grafts. Therefore, changes in plasma products of nitric oxide and endothelium-dependent relaxations mediated by nitric oxide are related to the dose of nicotine treatment.

Time and dose effect of transdermal nicotine on endothelial function

Nicotine patches are available as an over-the-counter medication for aid in smoking cessation. This study was designed to determine how nicotine patch therapy over time and dose ranges used in smoking cessation programs in humans affects endothelium-dependent relaxations. Dogs were treated with nicotine patches (11, 22, or 44 mg/day) for 2 and 5 wk. Circulating nicotine and oxidized products of nitric oxide (NOx) were measured. Coronary arteries were prepared for measurement of isometric force and aortic endothelial cells were prepared for measurement of mRNA or NO synthase (NOS) activity. Circulating nicotine increased with increasing concentrations of nicotine patches. After 5 wk of treatment with 22 mg/day patches, circulating NOx was reduced but NOS activity was increased. NOS mRNA was similar among groups. Only after 5 wk of treatment with 22 mg/day patches were endothelium-dependent relaxations reduced to alpha(2)-adrenergic agonists, ADP, and the calcium ionophore A-23187. These results suggest a time and biphasic dose effect of nicotine treatment on endothelium-dependent responses that may be related to bioavailability of NO. This complex relationship of duration and dose of nicotine treatment may explain, in part, discrepancies in effects of nicotine on endothelium-dependent responses.

Effects of transdermal nicotine treatment on structure and function of coronary artery bypass grafts

Smoking is a major risk factor for failure of coronary artery bypass grafts (CABG). Experiments were designed to determine effects of transdermal nicotine, independent of smoking, on structure and function of CABG. Saphenous veins were placed as CABG in untreated dogs (control) or in dogs treated with transdermal nicotine (one 11-mg or two 22-mg patches/day) for 5 wk. Serum nicotine and plasma nitric oxide were measured. Grafts were removed and prepared for organ chamber studies and histology. Serum nicotine averaged 12.1 and 118.7 ng/ml in the 11 mg/day and 44 mg/day groups, respectively. Plasma nitric oxide was higher in dogs treated with 11 mg/day doses compared with controls. In organ chamber studies, endothelium-dependent relaxations to thrombin and A-23187 and endothelium-independent relaxations to nitric oxide were greatest in grafts from dogs treated with 11 mg/day doses. Intimal thickness of the grafts were similar among groups. However, staining for bone sialoprotein was increased in the media of grafts from the 11 mg/day treatment group. These data suggest that transdermal nicotine in doses comparable and double to those used for conventional smoking cessation treatment in humans does not adversely affect early patency of canine CABG up to 4 wk postoperatively. Transdermal nicotine, however, may increase production of and response to nitric oxide in bypass grafts.

Improved prognosis of thoracic aortic aneurysms: a population-based study

CONTEXT

Managing thoracic aortic aneurysms identified incidentally by increased use of computed tomography, echocardiography, and magnetic resonance imaging is problematic, especially in the elderly.

OBJECTIVE

To ascertain whether the previously reported poor prognosis for individuals with thoracic aortic aneurysms has changed with better medical therapies and improved surgical techniques that can now be applied to aneurysm management.

DESIGN

Population-based cohort study.

SETTING AND PATIENTS

All 133 patients with the diagnosis of degenerative thoracic aortic aneurysms among Olmsted County, Minnesota, residents between 1980 and 1994 compared with a previously reported cohort of similar patients between 1951 and 1980.

MAIN OUTCOME MEASURES

The primary clinical end points were incidence, cumulative rupture risk, rupture risk as a function of aneurysm size, and survival.

RESULTS

In contrast to abdominal aortic aneurysms, for which men are affected predominately, 51% of thoracic aortic aneurysms were identified in women who were considerably older at recognition than men (mean age, 75.9 vs 62.8 years, respectively; P= .01). The overall incidence rate of 10.4 per 100000 person-years (95% confidence interval [CI], 8.6-12.2) between 1980 and 1994 was more than 3-fold higher than the rate from 1951 to 1980. The cumulative risk of rupture was 20% after 5 years. Seventy-nine percent of ruptures occurred in women (P= .01). The 5-year risk of rupture as a function of aneurysm size at recognition was 0% for aneurysms less than 4 cm in diameter, 16% (95% CI, 4%-28%) for those 4 to 5.9 cm, and 31% (95% CI, 5%-56%) for aneurysms 6 cm or more. Overall 5-year survival improved to 56% (95% CI, 48%-66%) between 1980 and 1994 compared with only 19% between 1951 and 1980 (P<.01).

CONCLUSIONS

In this population, elderly women represent an increasing portion of all patients with clinically recognized thoracic aortic aneurysms and constitute the majority of patients whose aneurysm eventually ruptures. Overall survival for thoracic aortic aneurysms has improved significantly in the past 15 years.