Acute effects of passive heat exposure on vascular function and exercise capacity in patients with chronic kidney disease.

Vascular dysfunction and exercise intolerance contribute to chronic kidney disease (CKD)-related cardiovascular disease. Passive heat exposure provides a physiological stimulus for beneficial vascular adaptations and improvements in exercise capacity but has not yet been investigated in CKD. The purpose of this pilot study was to examine the physiological response to an acute bout of passive heat exposure in patients with CKD. In this randomized, crossover trial, 10 participants with Stage G2-G4 CKD were enrolled (means ± SE; age, 41 ± 4 yr; 6 females; estimated glomerular filtration rate, 55 ± 7 mL/min/1.73 m2). After completing a baseline visit, participants completed two experimental visits: passive heat exposure via far-infrared sauna (HT; 25 min, 60°C) and thermoneutral control (CON; 25 min, 22°C). Macrovascular function, assessed by flow-mediated dilation (FMD), and microvascular function, assessed by the blood flow response to passive limb movement, were measured after a 60-min recovery period following exposure on each experimental visit. Exercise capacity was assessed with the 6-min walk test. Urinary markers of kidney function and injury were collected immediately and over 24 h following visits. FMD (3.84 ± 0.61 vs. 6.68 ± 0.76%, P < 0.01) and leg blood flow response to passive limb movement (area under the curve, 179 ± 29 vs. 243 ± 23 arbitrary units, P = 0.01) were greater following HT compared with CON. There was a clinically meaningful difference in 6-min walk distance between CON (632 ± 29 yards) and HT (670 ± 30 yards, P < 0.01). There were no significant changes in kidney function or biomarkers of acute kidney injury following HT. In this pilot study, a single bout of passive heat exposure acutely improved vascular function and exercise capacity in patients with CKD.NEW & NOTEWORTHY This is the first known study to examine the acute vascular, renal, and exercise response to a single bout of passive heat exposure in chronic kidney disease (CKD). Macrovascular function, microvascular function, and exercise capacity were acutely greater after a single session of passive heating, without any effect on kidney function or markers of kidney injury. These preliminary pilot findings could inform future clinical trials of chronic heat therapy for cardiovascular health in CKD.