Transcutaneous Oxygen and Carbon Dioxide Levels with Iloprost Administration in Diabetic Critical Limb Ischemia

Abstract

Iloprost, a prostacyclin analogue, is a treatment option for surgically unsuitable diabetic chronic critical limb ischemia (CLI), although its outcome is difficult to be anticipated clinically. Whether transcutaneous (tc) oxygen tension (PO₂) predicts the response to iloprost in diabetic CLI is unclear at this point and, in that same context, the prognostic role of tc carbon dioxide tension (PCO₂), another ischemia-sensitive parameter, is unknown. Supine and dependent tcPO₂ and tcPCO₂ were measured at baseline and after 4 weeks of iloprost treatment in 31 limbs of 26 type-2 diabetic arteriopaths with CLI not amenable to surgery. Success was defined as pain relief and significant reduction of analgesics. Clinical outcome was stratified by baseline tcPO₂ and tcPCO₂ tertiles, and likelihood ratios (LR) quantified the increase from pretest chances given a certain result. Iloprost succeeded in 16 (52%) and failed in 15 limbs (48%) and post-treatment tcPO₂ followed a parallel course. Failures increased by ascending baseline tcPCO₂ and descending tcPO₂ tertiles; successes behaved specularly. Predictions of failure based on elevated tcPCO₂ (>53 mm Hg) were more efficient than relying on depressed tcPO₂ (LR 10.7 vs 3.6); success was almost certain when tcPO₂ was >23 mm Hg (LR = 17.8). Dependent determinations were less useful than supine measurements for prognostic use. Elevated tcPCO₂ predicted failure efficiently and high tcPO₂ was a useful prognostic tool for success of iloprost, suggesting that their combined use may allow better prognostic stratification and improve the therapeutic approach to diabetic CLI.