Prospective study of transcutaneous oxygen tension (TcPO2) measurement in the testing period of spinal cord stimulation in diabetic patients with critical lower limb ischaemia.

BACKGROUND: Spinal cord stimulation improves microcirculatory blood flow, relieves diabetic neuropathic and ischaemic pain and reduces the amputation rate in patients with severe peripheral arterial occlusive disease.

AIM: To evaluate whether transcutaneous oxygen tension (TcPO2) measurements can be used as a specific prognostic parameter in the assessment of suitability for permanent device implantation in a prospective controlled study on diabetic patients with peripheral arterial occlusive disease.

METHODS: Sixty patients (39 men, 21 women; mean age: 60 years; range: 46-75) were submitted to implantation of a spinal cord electrical generator for severe peripheral vascular disease, after failed conservative or surgical treatment. The clinical status was classified as Fontaine's stage III and IV and the main pathology was diabetic vascular disease. Pedal TcPO2 was assessed on the dorsum of the foot and ankle and toe pressure Doppler measurements were performed before, two weeks and four weeks after implantation.

RESULTS: Pain relief of over 75% and limb salvage were achieved in 35 diabetic patients, while in 12 a partial success with pain relief over 50% and limb salvage for at least 6 months was obtained. In 13 patients the method failed and the affected limbs were amputated. Clinical improvement and spinal cord stimulation success were associated with increases of TcPO2, within the first two weeks after implantation (temporary period). Limb salvage was achieved with significant increase of TcPO2 within the first two weeks of the testing period (from 21.4 to 31.5 mmHg in rest pain patients, p=0.030, from 15.1 to 22.0 mmHg, p=0.030 in patients with trophic lesions under 3 cm2 in size and in those with trophic lesions over 3 cm2, from 12.1 to 17.9 mmHg, p=0.025) unrelated to the stage of the disease and the initial TcPO2 value. TcPO2 changes were related to the presence of adequate paraesthesias and warmth in the painful area during the trial period. The systolic ankle/brachial blood pressure index and toe pressure did not change under stimulation.

CONCLUSIONS: A two-week testing period should be performed in all diabetic patients treated with spinal cord stimulation for peripheral arterial occlusive disease to identify the candidates for permanent implantation. Only diabetic patients with significant increases of TcPO2 and clinical improvement, during the test period, should be considered for permanent implantation and not merely all patients with pain relief. TcPO2 changes could be used as a predictive index of the therapy success and should be considered in terms of cost effectiveness before the final decision to permanent implantation.