Selection of lower limb amputation level not aided by transcutaneous pO2 measurements

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.

A multidisciplinary approach and surgical tips in major amputations of diabetic patients

We aim to describe the results obtained in major amputations (transtibial and transfemoral) of diabetic patients followed with a close combined approach (medical and surgical). We evaluated 37 cases with an average age of 73.55 years. All were admitted in our Diabetology Department where they were monitored and treated in order to reach a new balance concerning cardiac failure, anemia, and other pathologies. Then, the orthopedic surgeons operate choosing an adequate level for amputation and pointing about adequate stump covering, accurate vessel, perineural and periosteal hemostasis, and nerve thermoablation. Reading literature we discovered in our series an improvement concerning perioperative mortality, considering the high average age and the bad general conditions of our patients; at the same time, we obtained an improvement about neuromas and ghost limb syndrome versus literature. About walking capabilities we had similar results compared to previous papers, obtaining the worst results for thigh amputations.

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.

Simultaneous measurement of digital artery and skin perfusion pressure by the laser Doppler technique in healthy controls and patients with peripheral arterial occlusive disease

OBJECTIVE

To assess feasibility of a new technique for simultaneous measurement of digital artery and skin perfusion pressure at the same digit using the laser Doppler method and to measure the pressure gradient between the two vessel compartments in controls and patients with peripheral arterial occlusive disease.

DESIGN

A pressure cuff wrapped around the basis of the toe and connected to a Statham transducer is covered by a special plastic capsule. A hole at the distal end of the capsule permits positioning of a laser Doppler probe at the pulp. A second laser Doppler probe is placed on the skin beneath the pressure cuff. Reappearance of pulsatile flux during cuff pressure release detected by the two laser Doppler probes indicated digital artery pressure and skin perfusion pressure on the corresponding pressure curve. Results in patients with intermittent claudication were compared to results of a group of normal controls.

SETTING

University Hospital, Zürich, Switzerland.

MATERIALS

Eleven healthy volunteers and 14 patients with intermittent claudication due to peripheral arterial occlusive disease were studied.

CHIEF OUTCOME MEASURES

Digital artery pressure (DAP), skin perfusion pressure (SPP) and pressure gradient between DAP and SPP.

MAIN RESULTS

Significantly lower mean DAP (95.8 +/- 23.2 mmHg vs. 49.8 +/- 20.4 mmHg; p < 0.01) and mean SPP (81.4 +/- 18.8 mmHg vs. 38.4 +/- 21.7 mmHg; p < 0.01) were observed in the patients. Mean pressure gradients and ratios between DAP and SPP did not differ significantly between the two groups. There was a linear correlation between DAP and SPP (r = 0.82, p < 0.01).

CONCLUSION

The laser Doppler method provides the possibility to measure digital artery and skin perfusion pressure simultaneously at the same digit in an easy and non-invasive way. Pressure gradients between DAP and SPP are similar in controls and patients with claudication.

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.