Biomarkers of free radical injury during spinal cord ischemia.

Plasma and urinary levels of 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha) were analysed at baseline and during the ischemia-reperfusion period in experimental spinal cord ischemia. A significant and immediate increase of 8-iso-PGF(2alpha) in plasma at the start and up to 60 min, and in the urine at 90-150 min following ischemia indicate an association of oxidative injury. The inflammatory response indicator 15-keto-dihydro-PGF(2alpha) in plasma increased significantly at the start and up to 60 min after ischemia. No such increase was seen in animals with no spinal cord ischemia. Thus, free radical mediated and cyclooxygenase catalysed products of arachidonic acid are increased during spinal cord ischemia as a consequence of oxidative injury and inflammation.

Monitoring of intrathecal oxygen tension during experimental aortic occlusion predicts ultrastructural changes in the spinal cord.

OBJECTIVE: To study the correlation between intrathecal PO2 and ultrastructural changes in the spinal cord during thoracic aortic occlusion in pigs. MATERIAL AND METHODS: In 18 pigs, online intrathecal oxygenation was monitored by a multiparameter Paratrend catheter (Biomedical Sensors, High Wycombe, United Kingdom) during 60 minutes' clamping of the proximal and distal descending thoracic aorta. The animals were randomly divided into 2 groups (A and B) depending on the level of distal aortic clamping. Distal aortic perfusion was restored through an aorto-iliac shunt, which also maintained low thoracic segmental perfusion of the spinal cord in group B. Perfusion-fixation technique was used before harvesting the spinal cord specimens, which later were evaluated with light and electron microscopy by an independent observer. Intrathecal parameters were interpreted as normal if PO2 was more than 0.8 kPa and PCO2 was less than 12 kPa, as intermediate ischemia if PO2 was 0.8 or less or PCO (2) was more than 12 kPa, and as absolute ischemia if PO2 was 0.8 or less and PCO2 was more than 12 kPa. RESULTS: Among 6 animals with ultrastructural changes of absolute spinal cord ischemia-reperfusion injury, 5 also had absolute ischemia according to variables derived by the Paratrend catheter. The 2 methods were in agreement in 3 of 5 animals with intermediate ischemia-reperfusion changes and in 5 of 6 animals with normal findings. The accuracy of cerebrospinal fluid PO2 and PCO2 to predict electron microscopy-verified intermediate or absolute ischemia-reperfusion injury was 94%. CONCLUSIONS: Monitoring of intrathecal PO2 after clamping of the descending aorta correlated with ultrastructural changes in the spinal cord in this pig model.

Aspects of the spinal cord circulation as assessed by intrathecal oxygen tension monitoring during various arterial interruptions in the pig.

OBJECTIVE: We sought to study the effect of various modes of interruption of the spinal cord blood supply on intrathecal oxygenation. METHODS: In 24 pigs intrathecal PO (2), PCO (2), and pH were continuously monitored with a multiparameter catheter (Paratrend 7, Biomedical Sensors; Diametrics Medical, Inc, St Paul, Minn) during and after aortic crossclamping or selective interruption of segmental arteries and proximal collateral circulation. RESULTS: Proximal aortic clamping (n = 6) produced complete ischemia, whereas a second clamp close to the celiac trunk (n = 4) partly protected against spinal cord ischemia. This is explained by prevention of the steal phenomenon in the excluded part of the aorta. Adding clamps to the subclavian arteries (n = 6) created complete spinal ischemia as the collateral circulation was interrupted. In another group (n = 4) all segmental arteries below T5 were occluded with no reaction in the intrathecal variables. Additional selective clamping of supreme intercostal arteries (n = 4) showed the relative importance of the subclavian and vertebral collateral pathways. CONCLUSIONS: Continuous intrathecal PO (2) was monitored during various modes of interruption of the spinal cord blood supply. This provided insight into the ischemia mechanisms and relative importance of the segmental contribution and proximal collateral pathways of the spinal cord circulation in pigs. A short literature review is given, and aspects of comparative anatomy are discussed.

A simple infusion method for measurement of intraoperative peripheral vascular runoff resistance.

A simple infusion system to assess the status of distal runoff was investigated on both hindlimbs of five mongrel dogs. Infusion catheters were placed in the superficial femoral arteries and the origin of the lower leg arteries was exposed for anatomic manipulation of the distal runoff. Saline solution was infused through the superficial femoral arteries at 64, 129, and 193 cm levels to calculate volume flow and index of resistance to flow. The in vitro part of the study was undertaken to analyze the effect of different-size catheters on flow rates in a rigid undistensible model. In the hindlimb study the flow differed significantly between two- and one-vessel runoff status at 50 and 100 mm Hg infusion pressures. In the in vitro study, in contrast to the hindlimb study, index of resistance to flow values for different-size catheters remained almost unchanged as the infusion pressure increased, demonstrating the distensibility of the runoff bed in dogs. A preliminary clinical study in 13 patients undergoing infrainguinal bypass surgery demonstrated a good correlation between angiographic runoff evaluation and intraoperative flow values. Valuable information can be obtained about the status of the distal runoff by this simple infusion method, which might be used to improve the prediction of outcome of infrainguinal bypass surgery.

A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs.

BACKGROUND: Impaired spinal cord circulation during thoracic aortic clamping may result in paraplegia. Reliable and fast responding methods for intraoperative monitoring are needed to facilitate the evaluation of protective measures and efficiency of revascularization. METHODS: In 11 pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during thoracic aortic cross-clamping (AXC) distal to the left subclavian artery. A laser-Doppler probe was inserted into the epidural space for simultaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and 60 minutes after declamping. The same measuring points were used for systemic hemodynamic and metabolic data acquisition. RESULTS: The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decreased within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both methods indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH. CONCLUSIONS: In this experimental model of spinal ischemia by AXC, online monitoring of intrathecal PO2, PCO2, and pH showed significant changes and correlated well with epidural laser-Doppler flowmetry (P < .01).

A new method of angiographic runoff evaluation in femorodistal reconstructions. Significant correlation with early graft patency.

In 62 patients undergoing femorodistal bypass surgery, the foot vessel runoff was analyzed with a new grading system based on intraoperative postreconstruction serial angiography. The patients were divided into two groups according to the level of the distal anastomosis (proximal or low). Good runoff was defined as integrity of the anterior and/or posterior foot arch in proximal femorodistal grafts and integrity of both arches in low bypasses. In the proximal group, runoff was classified as poor when the arches were deficient or occluded, and in the low group, when only one arch was intact. The patency rate after 6 months was 81% in the good runoff group, whereas all grafts in patients with poor runoff were occluded. The new method allowed better prediction of the early outcome than does the primary and secondary pedal arch integrity concept.

Bypass grafting to the popliteal artery in limbs with occluded crural arteries.

Intraoperative completion angiograms of 47 femoropopliteal bypasses in limbs with occluded crural arteries were reviewed to identify the angiographic determinants of early outcome. Of 28 limbs in which the foot vessels were available for analysis, only 2 (7%) had an intact pedal circulation, and 18 limbs demonstrated no crural arteries suitable for distal reconstruction. The overall cumulative patency rate was 51% with a 76% limb salvage rate at 12 months. All seven grafts performed onto a popliteal artery segment of less than 8 cm occluded in the early period. The status of crural and foot arteries and the number of collaterals did not correlate well with early patency. Limbs with no patent crural artery that were analyzed in the poor angiographic runoff group, according to our previously reported classification, demonstrated relatively higher patency rates than the other subgroups with poor runoff. In cases where angiography demonstrates a poor runoff for distal revascularization, popliteal bypass with occluded crural arteries might achieve acceptable patency rates.

Influence of twist on vein and PTFE graft hemodynamics: an ex vivo experimental study.

OBJECTIVE: In an ex vivo infusion model, the effect of different factors affecting the critical level of twist in vein and PTFE grafts was analysed. SETTING: University Hospital, Department of Surgery. EXPERIMENTAL DESIGN: Saline perfusion of grafts with various diameter and length under constant high (90 ml/min) and low (50 ml/min) flow rates against various peripheral resistance was performed. MEASURES: The pressure changes in the grafts were measured at increasing increments of twisting. RESULTS: The critical level of twist appears to be dependent on the diameter, length, stretching, status of peripheral resistance, amount of volume flow and the type of graft material, varying between 90 to more than 360 degrees. In vein grafts critical twisting appeared earlier with a decrease in diameter, shortening in length, high peripheral resistance, high flow rate and stretching. PTFE grafts especially with external spiral support were resistant to twist. CONCLUSIONS: These data suggest that the critical level of graft twist is dependent upon multiple factors and moderate or even high grade twist with especially externally supported PTFE grafts regardless of length and long mobilized vein grafts do not lead to hemodynamic changes. On the other hand total cessation of flow occurs at lower degrees of twist in stretched, short vein grafts.

Floating nonocclusive thrombus in the common femoral artery detected by duplex scanning after removal of the arterial catheter: a case report.

A 5-year-old girl is reported in whom duplex scanning showed a nonocclusive thrombus in the common femoral artery that was removed successfully by surgical intervention. Noninvasive examination with duplex scanning in patients with signs of acute arterial insufficiency during or after removal of femoral artery catheter is recommended.

Influence of low proximal aortic pressure on spinal cord oxygenation in experimental thoracic aortic occlusion.

BACKGROUND: To evaluate the effect of low proximal aortic pressure on cerebrospinal fluid (CSF) oxygenation in an experimental thoracic occlusion model. METHODS: In nine pigs, continuous intrathecal pO(2), pCO(2) and pH monitoring was used during double descending thoracic aortic clamping following insertion of an aorto-aortic shunt. In five pigs, the shunt was connected to a citrated bag adjusted at approximately 40-45 cm above the heart for partial exsanguination in order to decrease mean proximal aortic pressure (MPAP) to below 50 mmHg. In four animals, sodium nitroprusside infusion was used for this purpose. RESULTS: Intrathecal pO(2) demonstrated a significant decrease from 4.9+/-2.1 to 2.9+/-2.4 kPa after 10 minutes of aortic cross-clamping. Lowering proximal aortic pressure caused a further significant decrease to 1.2+/-1.7 kPa (p<0.05). In seven pigs (5 in the exsanguination and 2 in the vasodilator group), restoration of mean proximal aortic pressure to 94.0+/-27.7 caused a recovery of CSF pO(2) from 1.2+/-1.9 to 2.8+/-3.0 (p<0.05). CONCLUSIONS: The results of this study demonstrate that MPAP which provides spinal cord perfusion through subclavian-vertebral arteries are crucial for maintenance of spinal cord oxygenation during thoracic aortic occlusion in this pig model.

Patterns of atherosclerotic occlusive disease of lower leg and pedal arteries in hypertensive patients undergoing infrainguinal bypass procedures.

OBJECTIVE: To analyse the atherosclerotic involvement of lower leg and foot arteries in patients undergoing infrainguinal bypass grafting. SETTING: Department of Surgery, University Hospital. PATIENTS: Among 282 limbs (267 patients), fifty limbs belonged to hypertensive nondiabetics (Group A), 39 to hypertensive diabetics (Group B), 129 to normotensive nondiabetics (Group C) and 64 to normotensive diabetics (Group D). INTERVENTIONS: Femoropopliteal or femorodistal bypass procedures. MEASURES: Intraoperative postreconstruction serial angiography of the lower leg and foot arteries. RESULTS: Occlusion rate of two or three lower leg arteries was significantly higher among diabetics (Group B 77% and Group D 73%, respectively) compared to nondiabetics (Group A 56% and Group D 51%, respectively). It was similar in diabetic patients with or without hypertension. The incidence of having both foot arches (dorsal and plantar arch) intact was significantly higher in nondiabetic patients with hypertension (Group A). Only 5.8% of these patients demonstrated both deficient or occluded foot arches compared to 18% in Group B and 31% in Group C and 20% in Group D. CONCLUSION: Hypertension does not seem to contribute to the extent and severity of lower leg and foot vessel involvement in patients undergoing infrainguinal bypass surgery.

Surgical treatment of pararenal abdominal aortic aneurysms.

Thirty patients with juxtarenal infrarenal and 16 patients with suprarenal abdominal aortic aneurysms underwent elective (58%) or urgent (42%) repair. Twenty-three patients were hypertensive and 20 had impaired renal function preoperatively. Nineteen patients required combined aortic and renal artery reconstruction, in which reimplantation was the most common technique used. The perioperative mortality rate was 7.4% in the elective group and 36.8% in the urgent group. Rupture of the aneurysm and a preoperative high serum creatinine level were risk factors correlating to early mortality. Among survivors, 61% showed a rise in serum creatinine in the early postoperative period. In all but one the transient renal insufficiency was resolved within one month. Of the hypertensive patients 64% were cured or under control with medication following combined reconstruction. These results demonstrate that surgical repair of pararenal abdominal aortic aneurysms can be performed with an acceptable mortality and morbidity.

Spontaneous internal carotid artery dissection. Review.

Spontaneous ICA dissection is an increasingly recognized cause of stroke especially in young adults. The most frequently reported site of involvement is the cervical part of the internal carotid artery (ICA). Although several primary arteriopathies have been related to the development of spontaneous ICA dissection the cause is not clear in most cases. The clinical picture varies from mild cerebral and/or cranial nerve dysfunction to a completed stroke. Angiography has been considered as gold standard in establishing diagnosis. Recently, duplex scanning has emerged as a powerful noninvasive diagnostic tool only in the initial assessment but in the serial follow-up of patients. Early diagnosis is essential as these lesions require anticoagulant treatment. Immediate heparinization is instituted after diagnosis, followed by oral anti-coagulation for at least six months. Surgical treatment is warranted in only few cases. Complete resolutions of the dissection is seen in at least 50% of cases. The risk of recurrent stroke remains low in patients discharged alive after spontaneous ICA dissection.

Long-term follow-up of autologous vein grafts. 40 years after reconstruction for cystic adventitial disease.

Long term follow-up (38-41 years postoperatively) has been undertaken in three patients who were initially operated on with autologous reversed vein grafts due to cystic adventitial disease of the popliteal artery. The patients were evaluated clinically as well as with colour coded ultrasonography and phase-locked echo-tracking ultrasonography. One vein graft was occluded, the others were patent, without dilatation and with a compliance similar to that in the femoral artery. Autologous vein grafts below the groin are very durable.

A multivariate analysis of factors affecting patency of femoropopliteal and femorodistal bypass grafting.

BACKGROUND: The most important factors that determine the outcome after femoropopliteal and femorodistal arterial reconstruction are still controversial. This report analysis the factors that determine the early and late patency of distal arterial reconstruction. PATIENTS AND METHODS: A retrospective analysis of patency after femorodistal arterial reconstruction with a new method for evaluation of angiographic runoff was performed for 336 arterial reconstructions. The different pre-, per- and postoperative risk factors were analysed in a Cox proportional hazards model. RESULT: The patency was significantly better for vein grafts in comparison to composite grafts and prosthetic grafts. It was 74% for vein, 46% for composite and 43% for prosthetic reconstructions, respectively, at 12 months after arterial reconstruction. The cumulative life table patency rate in extremities with good, intermediate and poor runoff was 62, 30 and 10%, respectively at 36 months. The patency rates for extremities operated on for claudication was significantly better than for extremities operated on for critical ischaemia. The multivariate analysis of different factors in a Cox analysis revealed that only the status of distal runoff, the graft material and the site of the distal anastomosis independently and significantly influenced the patency rates. CONCLUSIONS: A new model for evaluation of distal runoff proved to predict the patency rate of femoropopliteal and femorodistal arterial reconstructions reasonably well in this retrospective analysis.

Duplex ultrasound scanning for diagnosis of aortoiliac and femoropopliteal arterial disease.

Forty patients with symptomatic aortoiliac and/or femoropopliteal occlusive arterial disease subjected to angiography were studied with duplex ultrasonography. The duplex scanning of the aortic, iliac, femoral and popliteal segments had a sensitivity of 93% in detecting significant stenoses and a specificity of 91%. The positive and negative predictive values were 75% and 98%, respectively. The sensitivity was relatively low in low-flow segments distal to total occlusions especially in patients with severe iliac disease and multiple distal femoropopliteal lesions. The results demonstrate the reliability of duplex scanning in detecting aortoiliac and femoropopliteal lesions.

Anastomotic rupture at the site of polytetrafluoroethylene (PTFE) and distal vein cuff of femoropopliteal bypass. Two case reports.

Two female patients, 63 and 78 years of age, underwent femoropopliteal bypass with polytetrafluoroethylene (PTFE) graft and distal vein cuff. They developed graft occlusion due to false aneurysm at the site of vein cuff during one and eight weeks after surgery, respectively. Improper suture technique or weak vein wall might lead to suture disruption leading to false aneurysm as presented in this article.

A modified technique of ultrasonic triplex scanning of the lower extremity arteries.

This study was undertaken to evaluate the utility of a modified technique of triplex scanning of the lower extremity arteries in 20 subjects without any clinical signs of arterial disease. The distal aorta and iliac arteries were examined with the subject in supine position and lying slightly on the opposite side. By moderate compression of the probe towards the psoas muscle and directing it over the iliac arteries with slight medial retraction of the abdomen, satisfactory visualization of the common and external arteries with 7.5 MHz high resolution imaging and a 5.6 MHz doppler probe were obtained in 56 of 80 segments (70%). In obese individuals it was necessary to use 5 MHz probe for satisfactory scanning of the aortic bifurcation and common iliac arteries. The distal superficial femoral, popliteal and tibioperoneal trunk segments were examined with the patient prone and the knee slightly flexed. Peak systolic, early diastolic reverse and late diastolic forward flow velocities were studied together with measurement of the arterial diemeters, which demonstrated wide variations. This study suggests that satisfactory scanning of the iliac and femoropopliteal arteries with the described technique can be achieved in the majority of subjects with a superficial high resolution probe. The combination of 7.5 MHz two-dimensional imaging with a 5.6 MHz pulsed wave Doppler probe offers optimal information of these arteries in nonobese individuals.

[Clinical assessment of critical ischemia is always to be done prior to amputation]. / Klinisk värdering av kritisk ischemi ska alltid göras före amputation.

Patients with critical limb ischemia (rest pain and/or ulcer/gangrene, together with low ankle pressure) are at risk of amputation, and should therefore undergo arterial reconstruction if that is at all technically possible. Thorough clinical investigation will usually distinguish patients in need of further evaluation by a vascular surgeon. No amputation should be undertaken without such evaluation. Diabetic patients belong to a special category, in that neuropathy makes it difficult to evaluate pain, and ankle pressure is often falsely high due to medial arterios sclerosis.