Predicting amputation in severe ischaemia. The value of transcutaneous PO2 measurement

Applicability of Transcutaneous Oxygen Tension Measurement in the Assessment of Chronic Limb-Threatening Ischemia

Transcutaneous oxygen tension measurement (TcPO₂) is widely applied for the evaluation of chronic limb-threatening ischemia (CLTI). Nevertheless, studies that focused on the clinical value of TcPO₂ have shown varying results. We identified factors that potentially play a role in TcPO₂ measurement variation such as probe placement, probe temperature, and the use of a reference probe. In this review of the current literature, we assessed the application of these factors. A systematic search was conducted. Parameters that were assessed were probe placement, probe temperature, and mentioning and/or use of a reference probe. In total, 36 articles were eligible for analysis. In 24 (67%) studies, probes were placed on specific anatomical locations. Seven (19%) studies placed probes, regardless of the location of the ulcer, adjacent to an ischemic lesion or ulcer (perilesion). Selected temperature setting of the probe differed; in 18 (50%), a default probe temperature of 44°C was selected, and in 13 (36%), a different temperature was selected. In 31 (84%) studies, the use of a reference probe was not reported. Transcutaneous oxygen tension measurement is applied diversely in patients with CLTI. Homogeneity in TcPO₂ protocols is warranted for reliable clinical application and to compare future TcPO₂ research.

Clinical efficacy of the pan metatarsal head resection as a curative procedure in patients with diabetes mellitus and neuropathic forefoot wounds

OBJECTIVE

To evaluate the safety and efficacy of the pan metatarsal head resection (PMHR) compared with nonsurgical management of wounds in the forefoot in people with diabetes.

METHODS

The authors evaluated 92 patients with diabetes (66.3% male), with ulcers classified as University of Texas grade 1A or 2A at the plantar aspect of the forefoot using a case-control model. Cases were patients treated with multiple metatarsal head resections for multiple metatarsal head wounds, and controls received standard nonsurgical care. Both groups received standard off-loading and wound care. Outcomes included time to healing, reulceration, infection, and amputation.

RESULTS

Patients in the surgery group (SG) healed significantly faster than those in the standard therapy group (ST; 84.2 ± 39.9 days for the ST vs 60.1 ± 27.9 days for the SG; P = .003) and had fewer recurrent ulcers (39.1% for the ST vs 15.2% for the SG; P = .02; odds ratio [OR] = 3.6; 95% confidence interval [CI] = 1.3-9.7) and infections during 1 year of follow-up (64.5% for the ST vs 35.5% for the SG; P = .047; OR = 2.4; 95% CI = 1.0-6.0). There was no significant difference in the proportion of patients receiving an incident amputation in the follow-up period (13.0% for the ST vs 6.5% for the SG; P = .5).

CONCLUSION

The results of this study suggest that the PMHR may be associated with shorter times to healing and lower morbidity compared with standard care alone in patients without digital gangrene and with multiple plantar forefoot ulcers.

Regions of arterial stenosis and clinical factors determining transcutaneous oxygen tension in patients with peripheral arterial disease

AIMS

Despite the clinical usefulness of transcutaneous oxygen tension (TcPO(2)) to assess the severity of limb ischemia, the factors determining TcPO(2) in patients with peripheral arterial disease (PAD) have not been fully clarified. We therefore examined the regions of arterial stenosis and clinical factors affecting lower-extremity TcPO(2).

METHODS

Resting TcPO(2) (REST-TcPO(2)) and postexercise TcPO(2) (Ex-TcPO(2)) in the calf region and the dorsalis pedis were measured simultaneously in 66 patients (132 limbs) with clinically suspected PAD, in whom angiography was also performed.

RESULTS

The peripheral arteries of the lower extremities were divided into five segments, and the impact of significant stenosis in each segment on ipsilateral TcPO(2) was evaluated by multiple regression analysis. In the calf region, significant stenosis of the proximal arteries (common-external iliac artery) revealed stronger involvement determining Ex-TcPO(2) than the peripheral segment (posterior tibial artery). In the dorsalis pedis, the peripheral segment (anterior tibial artery) more strongly determined Ex-TcPO(2) and REST-TcPO(2) than proximal segments. Age, creatinine, and diabetes were associated with REST-TcPO(2) of the calf region independent of arterial stenoses, while those of the dorsalis pedis were independently associated with age, and creatinine. In contrast, Ex-TcPO(2) in both regions was not independently associated with clinical factors, except for stenosis of the perfusing arteries.

CONCLUSION

The vascular lesions affecting TcPO(2) differ between the calf region (proximal > peripheral) and the dorsalis pedis (proximal < peripheral). In addition postexercise TcPO(2) is solely determined by stenosis of the perfusing arteries, while TcPO(2) at rest is affected by multiple clinical factors.

Using transcutaneous oxygen pressure measurements as selection criteria for activated protein C use

BACKGROUND

Limited resources and the expense of Activated Protein C (APC) (drotrecogin alfa) may contribute to the reluctance to utilize this drug in sepsis. Employing the PROWESS criteria resulted in absolute reduction in 28-day mortality of 6.1%, representing a relative risk reduction of 19.4%. Additional patient categorization and selection may lead to less frequent drug use with the same survival advantage. We used transcutaneous partial pressure of oxygen (PtcO2) as an indicator of microcirculatory perfusion to identify which septic patients may benefit from APC.

METHODS

Nineteen patients consecutively admitted with severe sepsis or septic shock that fulfilled the PROWESS criteria for APC treatment. APC was administered to patients with the PROWESS selection criteria, only if the PtcO2 information demonstrated tissue ischemia.

RESULTS

Nineteen patients met the PROWESS criteria. Ten patients demonstrated poor tissue perfusion using PtcO2 monitors and received APC. Nine patients had adequate tissue perfusion and did not receive APC. There were no differences in age, gender, APACHE II scores, lactate levels, or organ failure between the two groups. The 10 patients who received APC had a mortality of 3 of 10 (30%). The survivors of this group uniformly converted to PtcO2 values consistent with survival within 12 hours to 24 hours of drug administration. The nine patients who did not receive APC had a mortality of 2 of 9 (22%), not statistically significant from those who received the drug (p = 0.89).

CONCLUSION

Withholding APC did not result in an increase in mortality from severe sepsis in those patients who demonstrated adequate PtcO2 values. The transcutaneous oxygen measurement may be a useful adjuvant in addition to the other selection criteria for better identification of patients who may benefit from APC.

Validation of a diabetic foot surgery classification

The purpose of this project was to evaluate associations of increasing diabetic foot surgery stage with postoperative outcome. This project, designed as a retrospective cohort model, was conducted at three large, urban referral-based diabetic foot clinics. The investigators abstracted medical records from 180 patients with diabetes, 76.1% male, aged 57.8 +/- 11.2 years, falling equally into four classes of a previously reported diabetic foot surgery classification system. These classes included class 1 (elective), class 2 (prophylactic), class 3 (curative) and class 4 (emergency). There was a significant trend towards increasing risk of ulceration/reulceration (chi2(trend) = 17.8, P = 0.0001), peri-postoperative infection (chi2(trend) = 96.9, P = 0.0001), all-level amputation (chi2(trend) = 41.7, P = 0.001) and major amputation (chi2(trend) = 8.6, P = 0.003), with increasing class of foot surgery. The results of this study suggest that a non vascular foot surgery classification system including variables such as the presence or absence of neuropathy, an open wound and acute infection may be predictive of peri- and postoperative complications. This may assist the surgeon in better identifying risk when determining a rationale for and type of surgery in persons with diabetes.

Ankle fractures in diabetics

Treatment of the diabetic patient with ankle fracture presents a unique set of challenges to the surgeon. The care of these patients should follow a multidisciplinary approach with a team of orthopedic and vascular surgeons, internists, anesthesiologists, nurses, and diabetic educators. Meticulous preoperative planning, intraoperative technique, and postoperative care can be decrease potential limb-threatening complications; however, complications will occur despite excellent care. Early recognition and treatment of preoperative complications is imperative. These patients require close attention for long periods, and the surgeon should plan on building a strong relationship with these patients.

Non-invasive methods and stimuli for evaluating the skin's microcirculation

Vessels in the skin are arranged into superficial and deep horizontal plexuses and they are involved in thermoregulation, oxygen and nutritional support. The skin has a large number of functions and broad appeal spanning basic mechanistic and clinical research. Indeed, the skin can be used as a marker of normal and impaired vascular control and, owing to its accessibility and frequent involvement, is easy to investigate non-invasively. A large number of non-invasive methods are available for investigating the skin, ranging from those that permit the visualisation of microvessels, to those that monitor blood flow or one of its derivatives (e.g., skin temperature and transcutaneous oxygen). Such methods can be combined with non-invasive, dynamic stimuli (e.g., the use of cold or warm stimuli, activation of the peripheral nervous system or local neuronal systems, and the topical application of vasoactive drugs) and this potentially enables the differentiation of underlying disorders (e.g., primary from secondary Raynaud's phenomenon) and also to quantify changes over time or following intervention. The present article outlines the non-invasive methods and dynamic tests that can be used to investigate the microcirculation of the skin.

‘Pole Test’ Measurements in Critical Leg Ischaemia

BACKGROUND

For the quantification of critical limb ischaemia (CLI) most vascular surgery units use sphygmo-manometric and transcutaneous oxygen pressure (TcPO2) measurements. However, measurements obtained by cuff-manometry can be overestimated especially in diabetic patients because of medial calcification that makes leg arteries less compressible. TcPO2 measurements present a considerable overlap in the values obtained for patients with different degrees of ischaemia and its reproducibility has been questioned. Arterial wall stiffness has less influence on the pole test, based on hydrostatic pressure derived by leg elevation, and this test seems to provide a reliable index of CLI.

OBJECTIVE

The objective of this study was to evaluate the pole pressure test for detection of critical lower limb ischaemia, correlating results with cuff-manometry and transcutaneous oxygen pressure.

DESIGN

University hospital-prospective study.

MATERIALS AND METHODS

Seventy-four patients (83 legs) with rest pain or gangrene were evaluated by four methods: pole test, cuff-manometry, TcPO2 and arteriography. CLI was present if the following criteria were met: (a) important arteriographic lesions+rest pain with an ankle systolic pressure (ASP) < or = 40 mmHg and/or a TcPO2 < or = 30 mmHg, or (b) important arteriographic lesions+tissue loss with an ASP < or = 60 mmHg and/or a TcPO2 < or = 40 mmHg. Fifty-seven lower limbs met the criteria for CLI.

RESULTS

Measurements obtained by cuff-manometry were significantly higher to those obtained by pole test (mean pressure difference: 40 mmHg, p<0.001). The difference between the two methods remained statistically significant for both diabetics (50.73, p<0.001) and non-diabetics (31.46, p<0.001). Mean TcPO2 value was 15.51 mmHg and there was no important difference between patients with and without diabetes. Overall, there was a correlation between sphygmomanometry and pole test (r = 0.481). The correlation persisted for patients without diabetes (r = 0.581), but was not evident in patients with diabetes. Correlation between pole test and TcPO2 was observed only for patients with diabetes (r = 0.444). There was no correlation between cuff-manometry and TcPO2. The pole test offered an accuracy of 88% for the detection of CLI. The sensitivity of this test was 95% and the specificity 73%.

Skin microcirculation in peripheral arterial obliterative disease

The important role of microcirculation in the pathophysiology and symptoms of peripheral arterial obliterative disease (PAOD) has been progressively emphasized during the past twenty years, thanks to the use of different non-invasive methods, such as capillaroscopy, laser Doppler (LD) fluxmetry and transcutaneous measurement of oxygen tension (tcPO2). Basally, in the diseased leg of stage II PAOD patients, leg skin perfusion recorded by means of LD fluxmetry is quantitatively normal. However, spectral analysis of skin LD tracing shows an abnormal flowmotion, with increased amplitude of the flowmotion waves related to endothelial, neurogenic and myogenic activities, suggesting a relatively early skin microcirculatory adaptation in this PAOD stage. Following ischemia, an impaired total skin LD hyperemia and a reduced skin capillary nutritional blood flow at capillaroscopy, concomitantly with a reduced increase of flowmotion waves related to endothelial, myogenic and sympathetic activities, have been observed in the diseased leg of stage II PAOD patients. In critical limb ischemia (CLI), a more advanced cutaneous microcirculatory deterioration has been clarified, with a more severely impaired post-ischemic hyperemia, a reduced tcPO2 and a severely perturbed skin flowmotion in the diseased leg. This integrated skin microcirculatory diagnostic approach can be used for a better management of PAOD patients.

Measurement of critical lower limb tissue hypoxia by coupling chemical and optical techniques

It has been a long-term goal to develop non-invasive methods that can detect critical levels of tissue hypoxia to help in the management of chronic lower limb ischaemia. In the present study, skeletal muscle oxygenation was measured using a new Clark-type TCPO2 [transcutaneous PO2 (partial pressure of O2)]/PCO2 (partial pressure of CO2) monitoring system and optical NIRS (near-infrared spectroscopy) at graded levels of hypoxaemia using a rabbit model (n=6). The TCPO2/PCO2 probe was placed on the shaved hindlimb to record SPO2 (skin PO2) and SPCO2 (skin PCO2) continuously. A pair of NIRS probes were placed on the limb to monitor HbO2 (oxyhaemoglobin) and Hb (deoxyhaemoglobin). Graded hypoxaemia was achieved by stepwise reductions of FiO2 (fraction of inspired O2) from 30% to 6%. Animals were allowed to recover after each episode of hypoxia at an FiO2 of 30% as indicated by normalized arterial blood PO2. There was a significant (P<0.05) decrease in SPO2 with all grades of hypoxaemia and no significant changes in SPCO2. There was a significant (P<0.05) increase in muscle Hb with all grades of hypoxaemia and a significant (P<0.05) decrease in HbO2 when FiO2 was below 15%. A significant correlation was found between the SPO2 and HbO2 (r=0.92, P<0.001) and both were significantly correlated with arterial blood PO2 (P<0.001). The new TCPO2/PCO2 system, in addition to its application for the assessment of conditions such as chronic venous insufficiency where alteration in skin oxygenation occurs solely, also has potential in conditions such as peripheral vascular disease where both skin and muscle oxygenation may be affected.

Clinical efficacy of the first metatarsophalangeal joint arthroplasty as a curative procedure for hallux interphalangeal joint wounds in patients with diabetes

OBJECTIVE

To evaluate the safety and efficacy of first metatarsophalangeal joint arthroplasty compared with standard, nonsurgical management of wounds at the plantar hallux interphalangeal joint in patients with diabetes.

RESEARCH DESIGN AND METHODS

We evaluated 41 patients with ulcers classified as University of Texas Grade 1A or 2A at the plantar aspect of the hallux interphalangeal joint using a case-control model [correction]. Case subjects were patients treated with resectional arthroplasty and control subjects received standard nonsurgical care. Both groups received standard off-loading and wound care. Outcomes included time to healing, reulceration, infection, and amputation.

RESULTS

The surgery group healed significantly faster than patients in the standard therapy group (standard 67.1 +/- 17.1 versus surgery 24.2 +/- 9.9 days, P = 0.0001), and they had fewer recurrent ulcers (standard 35.0 versus surgery 4.8%, P = 0.02, odds ratio 7.6, 95% CI 1.1-261.7) Both groups had similar rates of infection (standard 38.1 versus surgery 40.0%, P = 0.9) and amputation (standard 10.0 versus surgery 4.8%, P = 0.5).

CONCLUSIONS

Results suggest that resectional arthroplasty is a safe and effective procedure to treat wounds of the plantar hallux compared with nonsurgical therapy.

Influence of percutaneous transluminal angioplasty on transcutaneous oxygen pressure in patients with peripheral arterial occlusive disease

PURPOSE

To determine in a prospective controlled trial the effect of percutaneous transluminal angioplasty (PTA) on skin oxygen supply and microcirculation as measured by means of transcutaneous oxygen pressure in patients with disabling lower-limb ischemia compared with that in patients who underwent intraarterial angiography for the assessment of disabling lower-limb ischemia.

MATERIALS AND METHODS

Thirty-four patients (17 men, 17 women; mean age, 68.6 years +/- 9.8 [SD]) with peripheral arterial occlusive disease (PAOD) (claudication, n = 15; critical ischemia, n = 19) underwent transcutaneous oxygen pressure measurement at the dorsum of the foot 1 day before PTA, during PTA, 1 day after PTA, and 6 weeks after PTA. Measurements were obtained with the patient in the supine and erect sitting positions, as well as after exercise. Thirty-one patients (21 men, 10 women; mean age, 68.5 years +/- 9.3) with symptomatic PAOD who were undergoing intraarterial angiography served as the control group.

RESULTS

Mean pressure before PTA was 31.6 mm Hg +/- 24 in the supine position, 50.8 mm Hg +/- 22 in the sitting position, and 22.2 mm Hg +/- 23 after exercise. Immediately after PTA, a significant increase to 34 mm Hg +/- 20 in the supine position was noted (P <.05). One day after PTA, pressure was 37.3 mm Hg +/- 20 for the supine position and 52 mm Hg +/- 20 for the sitting position. Six weeks after treatment, a further significant increase to 43.9 mm Hg +/- 19 in the supine position, 61 mm Hg +/- 15 in the sitting position, and 44.7 mm Hg +/- 24 after exercise was noted (P <.05). In the control group, a significant pressure decrease immediately after and 1 day after angiography was noted (P <.05). Measurements returned to baseline at 6 weeks follow-up.

CONCLUSION

PTA has a positive effect on oxygen supply to the skin in patients with PAOD. Conversely, intraarterial angiography in patients with PAOD deteriorates skin microcirculation temporarily.

Transcutaneous oxygen tension in patients with calciphylaxis

Calciphylaxis is a severe complication of chronic renal failure, confined almost exclusively to patients on dialysis therapy. Histological characteristics of calciphylaxis include small-vessel calcifications of skin, subcutaneous tissue, and visceral organs. These vascular changes promote tissue ischemia that often results in tissue necrosis. In this study, we investigated the extent of skin ischemia in patients with calciphylaxis by means of transcutaneous oxygen tension (TCPO(2)) measurement, a noninvasive test that accurately assesses skin oxygenation. TCPO(2) levels were measured in 21 patients with calciphylaxis and 21 age- and sex-matched patients without evidence of calciphylaxis (controls). TCPO(2) levels were measured bilaterally at the chest, anterior abdomen, and upper thigh while patients breathed room air and after a 30-minute exposure to 100% fraction of inspired oxygen (FIO(2)). Compared with controls, patients with calciphylaxis showed significantly lower TCPO(2) levels at each body region. In both controls and patients with calciphylaxis, lower TCPO(2) levels correlated with increased weight and use of hemodialysis. No correlation with serum parathyroid hormone (PTH), serum calcium, or serum phosphorus values was present, although 39% of the patients with calciphylaxis had markedly elevated PTH values (sixfold greater than normal; >300 pg/dL). Low TCPO(2) levels in patients with calciphylaxis were documented in body regions with and without skin lesions. In patients with calciphylaxis, extremely low TCPO(2) values (</=30 mm Hg while patients breathed room air) were present in 62% of the body regions with skin lesions and 26% of the body regions without lesions. Room-air TCPO(2) levels </=30 mm Hg were present in only 0.8% of the body regions of control patients. TCPO(2) levels obtained while patients breathed 100% FIO(2) remained lower in patients with calciphylaxis than in controls. In conclusion, TCPO(2) levels are abnormally low in patients with calciphylaxis, indicating that severe and diffuse skin ischemia exists, even at areas free of skin lesions. Low TCPO(2) values did not substantially increase with 100% FIO(2) in many patients with calciphylaxis, suggesting a fixed insufficiency of the skin vessels. This study shows that TCPO(2) measurements may allow rapid and noninvasive screening for skin ischemia before the development of skin lesions in patients with calciphylaxis.

Complications of ankle fractures in diabetic patients

Ankle fracture in patients with DM mandates a stepwise protocol to minimize the potential complications of delayed fracture healing, wound complications, and development of Charcot arthropathy. For nondisplaced ankle fracture, a nonoperative approach with increased duration of immobilization seems successful based on experience of the limited series. A displaced ankle fracture in a patient with DM requires a surgical intervention. The authors advocate tight glucose control in both groups to improve the fracture milieu and to ameliorate the potential complications. Appropriate stable fixation with adequate length of immobilization is crucial for successful fracture resolution.

Leg ulcers in peripheral arterial disease (arterial leg ulcers): impaired wound healing above the threshold of chronic critical limb ischemia

BACKGROUND

Peripheral arterial disease is the only identifiable etiology in approximately 10% of leg ulcers. Clinical data on the management of these chronic wounds are scarce.

OBJECTIVE

We attempted to outline the threshold of systolic ankle pressure and ankle-brachial-index (ABI) below which arterial leg ulcers can occur and to outline the indication for revascularization in arterial leg ulcers.

METHODS

Diagnostic and outcome analysis was performed for 26 consecutive patients with arterial leg ulcers. We calculated sensitivities, specificities, and receiver operating characteristic (ROC) curves for the identification of arterial leg ulcers among all 223 consecutive leg ulcer patients within a 3-year period, as well as the ROC curve for patients who required revascularization.

RESULTS

The systolic ankle pressure was 88 (18-130) mm Hg (median; 95% confidence interval) and the ABI was 0.60 (0.15-0.86), respectively. Eighteen patients (69%) were subjected to revascularization. By the end of the study, 24 patients (92%) healed completely, 1 improved (90% wound closure), and 1 patient had to undergo below-knee amputation for chronic osteomyelitis. During this study, the ankle pressure and ABI were poor in distinguishing those patients who required revascularization from those who healed without revascularization.

CONCLUSION

Most arterial leg ulcers do not meet the criteria of chronic critical limb ischemia, but they do not heal under conservative measures, either. A majority of these patients benefit from revascularization and should, therefore, be referred for arterial duplex ultrasound investigation or angiography. In our study, an ankle pressure below 110 mm Hg identified all patients (100%) who were subjected to revascularization procedures. However, controlled clinical studies are required to find the systolic ankle pressure and ABI below which revascularization can be recommended to speed up the healing time.

Skin blood flow level and stump healing in ischemic amputations

Skin blood flow was measured with xenon 133-histamine mixture in 20 lower extremities of 18 patients before performing amputations. The amputation levels were chosen according to clinical criteria; 13 below-knee, 3 distal femoral, 1 midfemoral, 2 transmetatarsal, and 1 Syme's amputations were performed. Fourteen stumps had normal healing, 2 had delayed healing, and 3 had necrosis. All of the stumps with normal healing had a skin blood flow >1.76 ml/100 g tissue/minute. Bleeding from the skin also was a good predictor of healing. Skin blood flow measurement may be helpful for level selection in ischemic amputations.

Prediction of imminent amputation in patients with non-reconstructible leg ischemia by means of microcirculatory investigations

PURPOSE

We investigated the usefulness of skin microcirculatory investigations to predict imminent major amputation in patients with non-reconstructible critical limb ischemia.

METHODS

One hundred eleven patients with non-reconstructible chronic rest pain or small ulcers and an ankle blood pressure of 50 mm Hg or less or an ankle-to-brachial pressure index of 0.35 or less were included. Nailfold capillary microscopy (CM; big toe, sitting), transcutaneous oxygen pressure (TcpO2; forefoot, supine; 44 degrees C), and laser Doppler perfusion measurements (LD; pulp of big toe, supine) were performed at rest and during reactive hyperemia. Patients were classified according to their skin microcirculatory status just before the start of the treatment in three groups: those with a "good," "intermediate," or "poor" microcirculation, according to a combination of predefined cutoff values (Poor: capillary density less than 20/mm2, absent reactive hyperemia in CM and LD, TcpO2 less than 10 mm Hg; good: capillary density of 20/mm2 or more, present reactive hyperemia in CM and LD, TcpO 2 of 30 mm Hg or more). Subsequently, patients received maximum conservative therapy from the surgeon, who was unaware of the microcirculatory results. After a follow-up period of as long as 36 months, limb survival and disposing factors were analyzed and compared with the initial microcirculatory status.

RESULTS

Cox regression analysis showed a significant prognostic value of the microcirculatory classification (hazard ratio = 0.28, P <.0001), but not of the Fontaine stage, ankle blood pressure, or the presence of diabetes mellitus for the occurrence of an amputation. Positive and negative predictive values were 73% and 67%, respectively. The cumulative limb survival at 6 and 12 months was 42% and 17% in the poor microcirculatory group, 80% and 63% in the intermediate microcirculatory group, and 88% and 88% in the good microcirculatory group ( P <.0001, log-rank).

CONCLUSION

Microcirculatory screening and classification is useful in detecting non-reconstructible critical ischemia that requires amputation, which is not detectable by means of the clinical stage or blood pressure parameters. Most of the poor patient group will require amputation. In the intermediate and good groups, nonsurgical treatment appears sufficient for limb salvage.

Effects of oxygen inhalation on skin microcirculation in patients with peripheral arterial occlusive disease

BACKGROUND

Oxygen administration is currently used in clinical medicine to improve peripheral oxygen delivery to tissues threatened by ischemia. However, conflicting results have been reported on the effects of oxygen in ischemic areas. This study was aimed at investigating the effects of 40% oxygen inhalation on the skin microcirculation in the feet of patients with peripheral arterial occlusive disease (PAOD).

METHODS AND RESULTS

Transcutaneous oxygen tension (tc PO2) was measured on the dorsal skin of the foot, and the nailfold microcirculation was investigated by a combination of laser Doppler flowmetry (LDF) and dynamic capillaroscopy (CBV) in the great toes of 17 legs of 11 patients, with 13 legs of eight normal subjects as a control group. Inhalation of oxygen induced a significant decrease of both the total (delta LDF, -307%, p less than 0.02) and nutritional (delta CBV, -17%, p less 0.002) skin microcirculation in normal legs compared with baseline values. A similar response was observed in 10 legs of patients who showed a significant increase of the tc PO2 (greater than or equal to 10 mm Hg) (delta LDF, -14%, NS; delta CBV, -13%, p less than 0.005). By contrast, both the total (+21%, p less than 0.03) and nutritional (+52%, p less than 0.05) circulation significantly increased in the seven legs without significant tc PO2 increase. In addition, the flow motion, which was impaired in the patients, was significantly (p less than 0.05) improved by oxygen inhalation.

CONCLUSIONS

Inhalation of 40% oxygen induces a vasoconstriction in the skin microcirculation of toes of the normal subjects and patients with moderate PAOD but induces an increase of the skin microcirculation in patients with severe PAOD.

Influence of clinical findings, positional manoeuvres, and systolic ankle arterial pressure on transcutaneous oxygen tension in peripheral arterial occlusive disease

The mutual effects of systolic ankle arterial pressures, positional manoeuvres, and calf artery occlusions on transcutaneous oxygen partial pressures (tcpO2) were studied in 388 legs of 258 patients with peripheral arterial occlusive disease (PAOD). The tcpO2-vs-perfusion pressure relationship could be satisfactorily fitted by a non-linear regression model deduced from the tcpO2 theory. Flow-insensitive ranges of tcpO2-vs-flow hyperbolas were reduced by both leg lowering and moving the electrode towards proximal measuring sites. Lower tcpO2 values were found in case of occluded compared to patent calf arteries at ankle arterial pressure indices below 0.4. The tcpO2 positional variability increased with worsening hemodynamic compensation and was most pronounced in critical limb ischaemia (ischaemic rest pain, non-healing ulcerations). According to a retrospective analysis, a critical ischaemia could be assumed if supine and sitting tcpO2-values exceed neither 10 nor 45 mmHg, respectively.

Selection of amputation level: a review

Preservation of the knee joint in a patient undergoing lower limb amputation for critical ischaemia is associated with improved postoperative rehabilitation and mobility. Yet, for most surgeons the below-knee to above-knee amputation ratio remains less than one. Poor wound healing and a high reamputation rate for below knee stumps are important factors mitigating against below-knee amputations. Many tests (Doppler indices, segmental pressures, skin blood flow, skin perfusion pressure, TcpO2, thermography) have been described to predict the likelihood of successful healing of an amputation stump but none appears to have gained widespread acceptance. Clinical judgement alone is insufficient to predict the success or failure of an amputation stump. In this review, we have looked at the evidence in support of these tests, particularly those routinely available to most surgeons.