Detection of microcirculatory impairment by transcutaneous oxymetry monitoring during hemodialysis: an observational study.

BACKGROUND: Little is known about the effects of intermittent hemodialysis on microcirculatory perfusion. The aim of this study is to assess the effects of hemodialysis on microvascular perfusion using transcutaneous oxymetry (TCPO2). METHODS: In this observational study, hourly TCPO2 measurements were performed during hemodialysis sessions. Ankle brachial index (ABI) was carried out to classify patients according their vascular condition. RESULTS: 50 patients (mean age 70 ± 8 years old) were enrolled. Mean TCPO2 decreased significantly on average 23.9% between start and finish of hemodialysis. Severe ischemia (TCPO2 < 30 mmHg) and critical ischemia (TCPO2 < 10 mmHg) occurred during dialysis in 47.1% and 15.5% respectively. Critical ischemia occurred only in limbs with ABI < 0.9 (8.3%) or > 1.3 (28%). Patients with critical ischemia experienced a significantly larger decline in mean blood pressure (32.4 ± 26.1 mmHg vs 12.7 ± 10.7 mmHg; P = 0.007) and a more pronounced ultrafiltration (45.55 ± 16.9 ml/kg vs 35.17 ± 18.2 ml/kg; P = 0.04) compared to patients without ischemia. Clinical outcomes (death or vascular procedures) were five times more frequent in patients who had developed critical ischemia (55.7% vs 10.1% P = 0.01). The elevated age of patients, the low basal value of TCPO2, and the occurrence of critical ischemia were more frequently associated with clinical outcome (P = 0.03, P = 0.048, P = 0.01 respectively). CONCLUSIONS: This study demonstrates that hemodialysis induces microcirculatory injury, dependent on blood pressure reduction, peripheral vascular state and ultrafiltration. The occurrence of critical ischemia is associated to pejorative patient outcome and therefore, TCPO2 seems to be useful to avoid potential distal tissue damage during hemodialysis.

Transcutaneous oxymetry as predictive test of peripheral vascular revascularization in haemodialysis population.

BACKGROUND: Peripheral arterial disease (PAD) occurs frequently among haemodialysis patients but it is underestimated. Vascular treatment and amputations are more frequent in end stage renal disease (ESRD) population compared to the general population possibly because of a diagnosis of PAD delayed. Transcutaneous oxymetry (TcPO2) is commonly used in vascular medicine to reflect local arterial blood flow and skin oxygenation.The aim of this study was to assess the accuracy of the TcPO2 measurements to screen PAD and to predict vascular outcomes in haemodialysis population. METHODS: In a 1-year prospective study, the value of TcPO2 was assessed in a cohort of 48 patients when starting haemodialysis. RESULTS: Twenty one patients had at least one vascular stenosis (42%) on Doppler examination and were considered as affected by PAD. At inclusion a pathologic resting TcPO2 (<40mmHg) was found in 13 patients (29%). A severe ischemia (TcPO2 <30mmHg) was noted in 8 patients (16.7%) and a critical limb ischemia (TcPO2 <10mmHg) in 3 patients.(6%). Eleven (25.5%) and 6 patients (15%) had a TcPO2 <40mmHg at 6 and 12 months respectively. During the follow-up, death was seven times more frequent in patients with abnormal TcPO2 at T0 compared to patients with normal TcPO2 (38% vs 5.7%; p = 0.04). Revascularization (n = 6) or amputation (n = 5) were required for 5 patients. TcPO2 was pathologic in all patients and legs requiring a vascular treatment. The sensitivity, specificity, positive predictive value and negative predictive value were 100%, 85.2%, 38% and 100% respectively. CONCLUSIONS: This study confirms the underestimated PAD diagnosis and the severity of PAD in haemodialysis population. A TcPO2 less than 40mmHg at the onset of the haemodialysis could identify patients at high risk of death and patients requiring vascular treatment. Moreover, since haemodialysis seems to be an accelerating factor of atherosclerosis, TcPO2 might be perform as a complement to traditional vascular explorations to assess the distal vascular conditions of limbs of haemodialysis patients.