Dhiraj M. Shah

Resurrection of the in situ saphenous vein bypass. 1000 cases later.

Distal bypasses for the terminal stages of atherosclerotic occlusive disease manifest by chronic limb-threatening ischemia are among the most challenging arterial reconstructive procedures of surgeons today. The length and low flow rates of distal bypasses often exceed the functional limits of synthetic and even free vein grafts. However, the saphenous vein, when used in situ, provides a unique, viable, physiologically active, and hence antithrombogenic endothelial flow surface that is ideally suited for such bypasses. This paper presents the experience of the Albany Medical Center Hospital with the first 1000 in situ bypasses performed by the valve incision method over a 12-year period. Limb-threatening ischemia was the most common indication for surgery (91%). An in situ bypass was attempted in over 95% of unselected limbs and were completed in situ and in toto in 94%. 66% of the bypasses were carried out to the infrapopliteal level, and in more than 50% of the limbs, the distal vein diameter was <3.5 mm. The 30-day patency rate was 95%, and the cumulative patency rates, by life table analysis at 1, 2, 3, 4, and 5 years, were 90%, 86%, 84%, 80%, and 76%, respectively. The vein diameter, specific outflow vessel, level of distal anastomosis (length of bypass), inguinal inflow source used, and instrumental evolution had no significant effect on immediate or long-term bypass performance.

Transfemoral placement of intraluminal polyurethane prosthesis for abdominal aortic aneurysm

Because of the significant mortality associated with the conventional surgical approach to abdominal aortic aneurysms (AAA) in the high risk patients and in those with ruptured aneurysms, we have developed a new approach to this problem, intraluminal aneurysm exclusion. This was achieved by an intraluminal prosthesis which approximated the diameter of the aorta above and below the aneurysm and is inserted through the femoral artery. The prosthesis consisted of biomedical grade elastomeric polyurethane with a NITINOL and/or stainless steel frame and was designed in such a configuration that it could be compressed inside a 15 F catheter and then regain its original shape after being discharged inside the aorta. The polyurethane prosthesis tolerated static pressures in excess of 300 Torr. Aneurysmal aortas were created in three adult sheep using large knitted Dacron pathches (6 X 9 cm) sewn onto a longitudinal aortotomy. After 4-6 weeks, an intraluminal prosthesis was passed transfemorally to the location of the aortic aneurysm. Following satisfactory placement and expansion of the prosthesis, a laceration was produced in the aneurysmal wall. No bleeding developed, which confirmed the integrity of the prosthesis in excluding the aneurysm from the aorta proper. Pulsation in the iliac arteries indicated the presence of aortic blood flow through the prosthesis. Autopsy examination demonstrated directly that the prosthesis was open and that its two ends were fixed in the aorta above and below the aneurysm. The study has demonstrated that intraluminal AAA exclusion could be achieved with an intraluminal polyurethane prosthesis inserted through the femoral artery.

Relationship Between Provider Volume and Mortality for Carotid Endarterectomies in New York State

BACKGROUND AND PURPOSE The objective of this study was to assess the relationship between each of 2 provider volume measures for carotid endarterectomies (CEs) (annual hospital volume and annual surgeon volume) and in-hospital mortality. New Yorks Statewide Planning and Research (SPARCS) administrative database was used to identify all 28 207 patients for whom carotid endarterectomy was the principal procedure performed in New York State hospitals between January 1, 1990, and December 31, 1995. METHODS A statistical model was developed to predict in-hospital mortality using age, admission status, and several conditions found to be associated with higher-than-average mortality. This model was then used to calculate risk-adjusted mortality rates for various intersections of hospital and surgeon volume ranges. RESULTS Risk-adjusted in-hospital mortality ranged from 1.96% (95% confidence interval, 1.47 to 2.57) for patients having surgeons with annual CE volumes of <5 in hospitals with annual CE volumes of </=100 to 0.94% (95% confidence interval, 0.73 to 1.19) for patients having surgeons with annual volumes of >/=5 in hospitals with annual CE volumes of >100. These 2 rates were statistically different. CONCLUSIONS We conclude that the in-hospital mortality rates for carotid endarterectomies performed by surgeons with extremely low annual volumes (<5) and for hospitals with low volumes (</=100) are significantly higher than the in-hospital rates of higher-volume surgeons and hospitals, even after taking preprocedural patient severity of illness into account.

Fish-oil dietary supplementation in patients with Raynaud's phenomenon: A double-blind, controlled, prospective study

PURPOSE The ingestion of omega-3 fatty acids could benefit patients with Raynauds phenomenon because, among other effects, these fatty acids induce a favorable vascular response to ischemia. The aim of our study was to investigate, in a double-blind, placebo-controlled manner, the effects of fish-oil fatty-acid dietary therapy in patients with rheumatic disease. PATIENTS AND METHODS Thirty-two patients with primary or secondary Raynauds phenomenon were randomly assigned to olive-oil placebo or fish-oil groups. Patients ingested 12 fish-oil capsules daily containing a total of 3.96 g eicosapentaenoic acid and 2.64 g docosahexaenoic acid or 12 olive-oil capsules and were evaluated at baseline and after six, 12, and 17 weeks. All patients ingested olive oil between Weeks 12 to 17. Digital systolic blood pressures and blood flow were measured at room air and water baths of 40 degrees C, 25 degrees C, 15 degrees C, and 10 degrees C using strain gauge plethysmography. Onset of Raynauds phenomenon was timed with a stop watch and defined as plethysmographic evidence of cessation of blood flow and blood pressure in the study finger. RESULTS In the fish-oil group, the median time interval before the onset of Raynauds phenomenon increased from 31.3 +/- 1.3 minutes baseline to 46.5 +/- 2.1 minutes at six weeks (p = 0.04). Patients with primary Raynauds phenomenon ingesting fish oil had the greatest increase in the time interval before the onset of the condition. Five of 11 patients (45.5 percent) with primary Raynauds phenomenon ingesting fish oil in whom the phenomenon was induced at baseline could not be induced to develop Raynauds at the six- or 12-week visit compared with one of nine patients (11 percent) with primary Raynauds ingesting olive oil (p = 0.05). The mean digital systolic pressures were higher in the patients with primary Raynauds phenomenon ingesting fish oil than in patients with primary Raynauds ingesting olive oil in the 10 degrees C water bath (+32 mm Hg, p = 0.02). CONCLUSION We conclude that the ingestion of fish oil improves tolerance to cold exposure and delays the onset of vasospasm in patients with primary, but not secondary, Raynauds phenomenon. These improvements are associated with significantly increased digital systolic blood pressures in cold temperatures.

Carotid endarterectomy in awake patients: Its safety, acceptability, and outcome

PURPOSE The purpose of this study was to determine the safety and efficacy of performing carotid endarterectomy procedures with the patient receiving cervical block anesthetic. METHODS Over the last 14 years, 654 carotid endarterectomy procedures were performed with patients receiving regional anesthetic. Intraluminal shunts were placed on demand, if neurologic changes with clamping of the carotid artery developed in the patient. During the same period, 419 cases were done with the patients receiving general anesthetic. Choice of anesthetic was based on surgeon and patient preference. RESULTS In the regional anesthetic group the indications for operation included transient ischemic attack (311), asymptomatic hemodynamically significant stenosis (146), amaurosis fugax (106), stroke (86), restenosis (3), and aneurysm (2). Shunts were used in 46 of 654 cases (7%). Conversion from regional to general anesthetic was required in seven patients (1.1%). The operative mortality rate was 0.76% (5 of 654). Permanent nonfatal neurologic deficits occurred in 0.76% (5 of 654), and temporary neurologic deficits occurred in 1.07% (7 of 654). CONCLUSIONS On the basis of these results, we believe regional cervical block anesthetic is an acceptable option to the routine use of shunts performed with the patient receiving general anesthetic during carotid endarterectomy. In addition, the ability to continuously assess the awake patient receiving cervical block may contribute to a decrease in perioperative stroke and mortality rates while simplifying functional cerebral monitoring during carotid endarterectomy.

Influence of hematocrit on cardiopulmonary function after acute hemorrhage.

The ‘optimal’ hematocrit to which patients should be resuscitated after shock and trauma is controversial. To test the hypothesis that sufficient oxygen delivery can be provided at a lower hematocrit without impairing oxygen consumption or hemodynamic function, 25 patients were prospectively studied

Strategies to improve spinal cord ischemia in endovascular thoracic aortic repair: Outcomes of a prospective cerebrospinal fluid drainage protocol

PURPOSE Although endovascular repair of thoracic aortic aneurysm has been shown to reduce the morbidity and mortality rates, spinal cord ischemia remains a persistent problem. We evaluated our experience with spinal cord protective measures using a standardized cerebrospinal fluid (CSF) drainage protocol in patients undergoing endovascular thoracic aortic repair. METHODS From 2004 to 2006, 121 patients underwent elective (n = 52, 43%) and emergent (n = 69, 57%) endovascular thoracic aortic stent graft placement for thoracic aortic aneurysm (TAA) (n = 94, 78%), symptomatic penetrating ulceration (n = 11, 9%), pseudoaneurysms (n = 5, 4%) and traumatic aortic transactions (n = 11, 9%). In 2005, routine use of a CSF drainage protocol was established to minimize the risks of spinal cord ischemia. The CSF was actively drained to maintain pressures <15 mm Hg and the mean arterial blood pressures were maintained at >/=90 mm Hg. Data was prospectively collected in our vascular registry for elective and emergent endovascular thoracic aortic repair and the patients were divided into 2 groups (+CSF drainage protocol, -CSF drainage protocol). A chi(2) statistical analysis was performed and significance was assumed for P < .05. RESULTS Of the 121 patients with thoracic stent graft placement, the mean age was 72 years, 62 (51%) were male, and 56 (46%) underwent preoperative placement of a CSF drain, while 65 (54%) did not. Both groups had similar comorbidities of coronary artery disease (24 [43%] vs 27 [41%]), hypertension (44 [79%] vs 50 [77%]), chronic obstructive pulmonary disease (18 [32%] vs 22 [34%]), and chronic renal insufficiency (10 [17%] vs 12 [18%]). None of the patients with CSF drainage developed spinal cord ischemia (SCI), and 5 (8%) of the patients without CSF drainage developed SCI within 24 hours of endovascular repair (P< .05). All patients with clinical symptoms of SCI had CSF drain placement and augmentation of systemic blood pressures to >/=90 mm Hg, and 60% (3 of 5 patients) demonstrated marked clinical improvement. CONCLUSION Perioperative CSF drainage with augmentation of systemic blood pressures may have a beneficial role in reducing the risk of paraplegia in patients undergoing endovascular thoracic aortic stent graft placement. However, selective CSF drainage may offer the same benefit as mandatory drainage.

Instrumental evolution of the valve incision method of in situ saphenous vein bypass

The previously stated advantages of the valve incision method of in situ saphenous vein arterial bypass have now been confirmed by others. However, this method has been limited by its time-consuming technical demands. Considerable experience with this bypass in conjunction with retrograde serial valve disruption with instruments of similar design principle (by Hall and Cartier) has been accumulated in Europe. However, the combination of the trauma of blunt valvular fracture and the sensitivity of endothelium to frictional shear has precluded use of these instruments in veins less than 4 mm in size, and the results have not been significantly better than those obtained with reversed vein bypass. An instrument (valve cutter) that achieves serial valve incision safely and consistently without mandatory exposure of each valve site has now been developed. Of the last 166 consecutive bypasses, the saphenous vein was suitable for use of this instrument in 116 instances (70%). The patency of these bypasses as determined by life-table analysis has shown no significant difference when compared with bypasses performed under similar conditions in which the cutter was not used. On the basis of this investigative and clinical experience, the majority of in situ saphenous vein arterial bypasses can be safely facilitated and simplified by use of this instrument.

Failure of red blood cell transfusion to increase oxygen transport or mixed venous PO2 in injured patients.

Post-trauma patients have an oxygen consumption which is proportional to oxygen delivery, suggesting that tissue oxygen consumption is limited by diffusion. Transfusion of packed red blood cells (RBC), which increases the oxygen-carrying capacity of blood, would be expected to increase mixed venous PO2, thereby improving tissue oxygenation. However, the low P50 of stored blood may increase the affinity of hemoglobin for oxygen and reduce oxygen consumption. To evaluate the net effect of these mechanisms, we studied hemodynamic and oxygen transport parameters before and after RBC transfusion in eight critically ill patients. Mixed venous O2 content was measured directly by fuel cell O2 analyzer, and standard P50 was calculated. Following transfusion of one unit of packed RBC which increased mean hemoglobin from 9.2 +/- 0.3 gm/dl to 10.1 +/- 0.3 gm/dl (p less than 0.01), there were no changes in oxygen delivery (490 +/- 80 ml/min/m2), oxygen consumption (210 +/- 30 ml/min/m2), or mixed venous PO/ (37 +/- 2 Torr). Cardiac index (4.1 +/- 0.71 L/min) decreased by 0.4 L/min/m2 (p less than 0.05). Standard P50 decreased by 4.2 +/- 2.4 Torr following transfusion of two units of RBC (p less than 0.05). Red blood cell transfusion thus failed to increase oxygen consumption in these patients, despite an increase in oxygen content. Thus, RBC transfusion may not improve tissue oxygenation.

The anatomy of the greater saphenous venous system

To define surgical anatomy, a prospective study of the greater saphenous venous system in 385 instances in 331 patients was carried out with the use of prebypass phlebography (either pre- or intraoperative). The phlebographic interpretations were confirmed during the operative procedures and from the completion angiogram. These details were recorded and analyzed by a specific computer program. These data consisted of a number of superficial branches, perforators, the identification of valve leaflets, sinuses, and the size and position of the main venous trunk both in the thigh and in the calf. The study showed that a single trunk was present in the thigh in 65% of patients and in the calf in 45%. The remainder were variants of double systems. In two thirds of patients who had complete double systems, the larger system was used for in situ bypass but the rest required the use of parts of both systems. Phlebography was accurate in the depiction of the anatomic variations (93%), double systems, cross connections, and perforator branches (87%). However, the number of competent valves could not be accurately determined (accuracy, 68%). The diameter of the vein was frequently underestimated (in 80% by 1.1 +/- 0.4 mm) and hence could not be used as an index of vein adequacy. After phlebography, four patients had transient rises in serum creatinine levels and one had an iatrogenic thrombosis of a distal segment. This study suggests that the precise anatomy of the greater saphenous venous system should be determined preoperatively by phlebography since this information is valuable for proper surgical planning before vein is used as a graft or for in situ bypass in the lower extremity.