Asterios N. Katsamouris

Utility of transcutaneous oxygen tension measurements in peripheral arterial occlusive disease

The use of transcutaneous oxygen tension (TCpO2) measurements to objectively and noninvasively diagnose peripheral arterial occlusive disease (PAOD) and to aid in the planning of vascular surgery was investigated. Thirty-two normal subjects and 100 patients with PAOD were studied. TCpO2 values decreased with age; when normalized by measurements on the chest, they did not. Absolute and normalized values of TCpO2 were equally effective in identifying the presence of PAOD and accurately characterized different degrees of severity (claudication vs. rest pain vs. impending gangrene; p less than 0.001). This was true even in diabetic patients, in whom tests based on hemodynamic function were less reliable. Healing of amputations was observed when TCpO2 greater than or equal to 38 mm Hg either preoperatively or after reconstruction; failure to heal in the absence of infection was associated with TCpO2 less than or equal to 38 mm Hg. The need for revascularization was associated with TCpO2 less than 30 mm Hg. A similar distribution of TCpO2 values was associated with success vs. failure of ulcer healing. TCpO2 is a useful complement to standard hemodynamic tests in the diagnosis and management of PAOD and, in addition, provides some distinct advantages.

Transcutaneous oxygen tension in selection of amputation level

The utility of transcutaneous oxygen tension measurements in selection of a reliable amputation level was evaluated. Measurements were made at the proposed level of amputation in 37 patients, 22 of whom underwent major limb amputation and in 15 amputation was confined to the forefoot or toes. In patients with successful amputation healing, mean transcutaneous oxygen tension on the anterior skin surface was 50 +/- 8 mm Hg (index 0.79 +/- 0.1 mm Hg). In contrast, patients with failure of healing had a mean transcutaneous oxygen tension of 22 +/- 16 mm Hg (index 0.32 +/- 0.19 mm Hg) (p less than 0.001). Measurements on the posterior or plantar skin surface and posteroanterior differences provided even greater separation between success and failure groups, with no overlap of transcutaneous oxygen tension values or index. Transcutaneous oxygen tension measurement is easily obtained and noninvasive, and can be applied to all patients irrespective of Doppler signals, noncompressible vessels, or painful lesions. Transcutaneous oxygen tension appears to predict successful healing with accuracy, and should be a useful addition to clinical judgment in selection of optimal amputation level.

Limb Arterial Injuries Associated with Limb Fractures: Clinical Presentation, Assessment and Management

OBJECTIVES Review of limb arterial injuries associated with limb fractures. DESIGN Retrospective study. SETTING University Hospital. MATERIALS AND METHODS The clinical presentation, assessment and management of 25 patients with upper (seven) and lower (18) limb arterial injuries associated with limb bone fractures has been retrospectively reviewed. MAIN RESULTS Five patients presented with life threatening injuries and classic signs of acute limb ischaemia, 15 patients had an obvious limb arterial injury, and 5 presented with a suspected limb arterial injury. The site of arterial damage was: superficial femoral (4); popliteal (11); tibioperoneal trunk (3); anterior tibial (4); posterior tibial (3); peroneal (2); axillary (1); brachial (5); radial (4); and ulnar artery (4). The types of arterial repair were: autogenous vein interposition or bypass grafting (17); P.T.F.E. (2); end-to-end anastomosis (14); and ligation (8). The popliteal vein was injured in six cases, repaired in four and ligated in two; the superficial femoral vein was injured in four cases, repaired in three and ligated in one; and the axillary vein was injured in one case and was ligated. Primary nerve repair was employed in six out of seven injured nerves. Skeletal fixation preceded vascular repair in 21 patients and in four a Javid shunt was used. Intraoperative fasciotomy was performed in 12 out of 18 patients with lower limb ischaemia. Completion arteriography revealed residual thrombi in the distal foot of four patients, in whom intraarterial thrombolysis was effective. During the follow-up period of 1.5 to 2 years, the upper and lower limb preservation rate was 100 and 89%, respectively. The upper limb function was judged excellent in five patients, good in one and fair in one. In the lower limbs it was excellent in 11 patients, good in three, fair in one and poor in one. CONCLUSIONS To ensure life and functional limb salvage of patients with devastating vascular injuries, a well organised multidisciplinary approach is necessary.

Acute lower limb ischemia as the initial symptom of acute myeloid leukemia

Although coagulatory system disorders are well recognized in patients with acute leukemia, these usually present with either hemorrhagic complications or thrombosis of small vessels. Large vessel thrombosis is a very rare clinical presentation. We present a patient with previously undiagnosed acute myeloid leukemia (M5), who was referred to our hospital with symptoms of acute ischemia of his right lower limb. Occlusion of the right external iliac artery due to a combination of leucostasis and coagulation disorders was noted and successfully treated with urgent leukapheresis, immediate chemotherapy and surgical thromboembolectomy.

Control of Left Ventricular and Proximal Aortic Dimensional Decompensation During Clamping of Descending Thoracic Aorta

The dimensional changes (mea sured by ultrasonic miniaturized transducers) of the left ventricle (LV), and proximal aorta (PAo) that accompanied hemodynamic changes during a forty-minute period of cross-clamping of the descending tho racic aorta without (Group A, 5 dogs) or with (Group B, 5 dogs) controlled vasodilation with sodium nitroprus side (SNP) infusion were evaluated in 10 open-chest anesthetized dogs. In both groups, measurements were re peated for another thirty-minute pe riod after declamping. In Group A, during clamping, systemic vascular resistance (SVR), PAo pressure (PAoP), LV systolic pressure (LVSP), and PAo midwall stress increased sig nificantly (p < 0.001). LV end-diasto lic pressure (LVEDP), stroke volume (SV), cardiac output (CO), and coro nary blood flow (CBF) did not show major variations, whereas systolic and diastolic LV wall thickness were significantly reduced (p < 0.02). A re duction in systolic shortening and thickening was observed also (p > 0.05). In Group B, during the same period, CO and CBF increased substantially (p < 0.02). SVR, PAoP, LVEDP, PAo midwall stess, and SV remained close to baseline values, while systolic and diastolic (p < 0.05) segmental length and systolic short ening and thickening increased (p > 0.05). Furthermore, the velocity of systolic shortening in Group B was significantly higher (p<0.005) than in Group A. In conclusion, the data indicate that significant changes, as detected continuously by sonomicro metry, in LV wall geometry and PAo midwall stress were observed during aortic cross-clamping. SNP infusion appeared to be an effective pharma cologic intervention to control these changes and to preserve cardiovascu lar performance.

Preliminary experience with cutting balloon angioplasty for iliac artery in-stent restenosis.

Purpose: To report our preliminary experience using cutting balloon angioplasty (CBA) in symptomatic iliac artery in-stent restenosis (ISR). Methods: Fourteen cases of hemodynamically significant iliac artery ISR (4 common and 10 external) were treated in 12 men (mean age 64 years, range 55–75). Of the 14 stents involved, 8 were balloon-expandable models and 6 were self-expanding. All patients had symptomatic deterioration of at least 1 clinical category over an average period of 50.2 months (range 6–120) post stenting. The mean length of ISR was 11.9 mm (range 2–48), and the average stenosis was 75.4% (range 52%–98%). Nine ISR lesions were focal (<10 mm), 4 were diffuse (>10 mm), and 1 extended outside the stent margins. Results: CBA was performed after conventional angioplasty failure in 7 lesions and as a primary treatment method in 7 lesions. Single (9 focal lesions) or multiple overlapping (5 diffuse or proliferative lesions) inflations were performed using 6-×10-mm (1 lesion), 7-×10-mm (3 lesions), and 8-×10-mm (10 lesions) devices. There was 1 contained rupture treated with a covered stent. In the remainder of the cases, the cutting balloons allowed successful treatment without further stent implantation. During a mean follow-up of 23.6 months (range 12–60), no patient showed clinical deterioration, and no recurrent ISR was detected with color duplex. Conclusion: CBA shows high immediate technical and midterm clinical success in symptomatic iliac artery ISR.

The study of the thrombin generation mechanism and the effect of low molecular weight heparin as thromboprophylaxis in patients undergoing total knee and hip replacement

INTRODUCTION The recommended duration of post-operative Low-Molecular-Weight-Heparins (LMWHs) thromboprophylaxis in Total-Hip-Replacement (THR) and Total-Knee-Replacement (TKR) surgery is controversial. Our aim is to study the thrombin generation (TG) modifications induced by surgery and to evaluate the effect of LMWH on TG during and after the recommended duration. PATIENTS/METHODS Thirty-one patients received 4000IU anti-Xa/day of enoxaparin, 8-hours post-operatively (15 THR for 30-days and 16 TKR for 15-days). TG assay sensitive to enoxaparin was performed, pre-operatively (D0), 7-hours post-surgery (D1), 8-days post-surgery (D8), and 2-days after thromboprophylaxis withdrawal (D32 and D17), evaluating: lag-time, endogenous thrombin potential (ETP), peak amount of generated thrombin (Peak), time-to-Peak (tt-Peak), and the Mean-Rate-Index [MRI=Peak/(tt-Peak-lag-time)]. RESULTS TKR surgery decreased lag-time and tt-Peak and increased MRI on D1 vs D0 (p<0.05). In contrast, THR did not significantly modify TG. Enoxaparin effectively reduced thrombin generation in both groups. Thromboprophylaxis withdrawal resulted in rebound increase of TG in the TKR patients (ETP, Peak & MRI significantly increased on D17 vs D0; p<0.05, and vs. D1; p<0.05) but not in THR patients. Variability in the response to enoxaparin was observed among patients of the same group. CONCLUSIONS TKR surgery is more thrombogenic than THR surgery. In THR patients TG was efficiently inhibited by 30-day thromboprophylaxis, whereas, in TKR patients treated for 15-days TG was not effectively inhibited. Individual variability of the response to enoxaparin was observed in both groups revealing some form of biological resistance to enoxaparin. TG assay may represent the breakthrough step to efficient antithrombotic strategy in clinical settings with high thrombotic risk.

Effects of Isoflurane Anesthesia on Aortic Compliance and Systemic Hemodynamics in Compliant and Noncompliant Aortas

OBJECTIVES To investigate the effect of general anesthesia on aortic compliance and other cardiovascular hemodynamics in chronically instrumented pigs with compliant and noncompliant (stiff) aortas. DESIGN Experimental study. SETTING University animal laboratory. PARTICIPANTS Twelve adult Yucatan miniature pigs. INTERVENTIONS Chronic instrumentation of a compliant (control; n = 7) and noncompliant (n = 5) group to measure pressure and flow in the ascending aorta. A Teflon prosthesis was wrapped around the aorta (noncompliant group) to limit wall compliance. MEASUREMENTS AND MAIN RESULTS Hemodynamic parameters were recorded on the 15th postoperative day, both awake and after general anesthesia. Banding the aorta caused a significant decrease in arterial compliance (-49%, p<0.001) and increases in systolic blood pressure (SBP: +38%, p = 0.001) and pulse pressure (+107%, p< 0.01). Induction of anesthesia in the control group produced a 15% increase in arterial compliance (p<0.05), resulting in a subtle decrease in SBP (-12%), diastolic blood pressure (DBP; -13%) and mean blood pressure (MBP; -12%). Induction of anesthesia in the noncompliant group also caused a significant increase in arterial compliance (17%, p<0.001), but caused significant decreases in SBP (21%, p<0.01), DBP (23%, p<0.01) and MBP (22%, p<0.01) as compared with controls. CONCLUSIONS Induction of general anesthesia caused a similar increase in total arterial compliance and was associated with a decrease in SBP that was more pronounced in animals with noncompliant aortas. These results indicated that anesthesia caused a greater hemodynamic effect on noncompliant (stiff) aortas and may explain the extensive hemodynamic fluctuation and instability often observed in atherosclerotic, elderly patients with stiff aortas.

Significance of Arteriovenous Shunting in the Pathogenesis of Primary Varicose Veins

This study assesses the hypothesis that arteriovenous shunts constitute an important factor in the develop ment of varicose veins of the lower extremities by analyzing and compar ing venous and arterial blood gases in a homogeneous study population group under standard and physio logic conditions. Twenty-five patients (pts) with primary varicose veins were entered into the study; 14 were men and 11 were women aged twenty-two to sixty-seven (median forty) years. The control group com prised the same number of healthy individuals of similar sex and age. Blood samples were collected from an antecubital vein and a limb varicosity in the pt group, along with an arterial blood sample drawn simultaneously from the radial artery. Blood samples were also drawn from an antecubital vein and a calf vein in the control group, along with an arterial blood sample. Blood sampling was per formed with the subjects in supine position, breathing room air at tem perature 21-23°C. The pH, pO2, total CO2, and hemoglobin saturation (Hbsat) were measured, and oxygen content (Co 2) and arteriovenous Co2 difference were calculated in all blood samples. Statistical compari sons of mean values were made in and between each group by using the t-test. A significant increase in nor mal and diseased limb venous pO2 (pvO2), Hbvsat, and Cvo 2, and de crease in limb arteriovenous Co2 dif ference was demonstrated in each group whereas no significant differ ences were found in those variables between the groups. It seems un likely, therefore, that an arterioven ous shunting is a general causal factor in the pathogenesis of primary varicose veins in the lower extremi ties.

Continuous monitoring of oxygen tension with a transcutaneous sensor during hypotensive anesthesia.

Transcutaneous oxygen tension (TCPo2) is a useful noninvasive technique for monitoring arterial oxygen tension under stable circulatory conditions. This study was undertaken to determine if TCPo2 is also reliable during sodium nitroprusside‐induced hypotension under general anesthesia. Arterial blood gases and TCPo2 were measured prior to inducing hypotension (baseline), at 20‐min intervals during hypotension, and when systemic arterial pressure had returned to within 10% of the control (pre‐hypotension) value. With induced hypotension, Pao2 and TGPo2 decreased significantly (P<0.05), and were well correlated by linear regression (r>0.85); however, regressions were strongly dependent on the individual patient. The mean regression line for all patients as a group was given by TCPo2 = 0.69 Pao2 + 20.7 mmHg (r = 0.93, P<0.01); significantly different regressions were obtained for each patient (P<0.0001). Comparing changes in TCPo2 versus those in Pao2 (relative change from baseline values) did not substantially reduce the variability among patients. It is concluded that TCPo2 reliably reflects changes in arterial oxygen tension during controlled hypotension under general anesthesia, but that a separate calibration of TCPo2 vs. Pao2, obtained prior to inducing hypotension, may be required for each individual patient.