title: Exaggerated blood pressure response to dynamic exercise despite chronic refractory hypotension: results of a human case study.
abstract: BACKGROUND
  Chronic refractory hypotension is a rare but significant mortality risk in renal failure patients. Such aberrant physiology usually deems patient unfit for renal transplant surgery. Exercise stimulates the mechano-chemoreceptors in the skeletal muscle thereby modulating the sympathetic effects on blood pressure regulation. The haemodynamic response to dynamic exercise in such patients has not been previously investigated. We present a case with severe chronic hypotension who underwent exercise testing before and after renal transplantation, with marked differences in blood pressure response to exercise.
  
  
  METHODS
  A 40-year old haemodialysis-dependent patient with a 2 year history of refractory hypotension (≤80/50 mmHg) was referred for living donor renal transplantation at our tertiary centre. Each dialysis session was often less than 2 h and 30 min due to symptomatic hypotension. As part of the cardiovascular assessment, she underwent haemodynamic evaluation with cardiopulmonary exercise testing. Blood pressure normalized during unloaded pedalling but was exaggerated at maximal workload whereby it rose from 82/50 mmHg to a peak of 201/120 mmHg. Transthoracic echocardiography, tonometric measure of central vascular compliance and myocardial perfusion scan were normal. She subsequently underwent an antibody-incompatible renal transplantation and was vasopressor reliant for 14 days during the post-operative period. Eight weeks following transplant, resting blood pressure was normal and a physiological exercise-haemodynamic response was observed during a repeat cardiopulmonary exercise testing.
  
  
  CONCLUSIONS
  This case highlights the potential therapeutic role of unloaded leg cycling exercise during dialysis session to correct chronic hypotension, allowing patients to have greater tolerance to fluid shift. It also adds to existing evidence that sympathetic dysfunction is reversible with renal transplant. Furthermore chronic hypotension with preserved exercise-haemodynamic response and cardiovascular reserve should not preclude these patients from renal transplant surgery.
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. Alice.rogan@nhs.net.
authors.forename: Alice
authors.initials: A
authors.lastname: Rogan
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. Gordon.mcgregor@uhcw.nhs.uk.|Departments of Cardiac Exercise Physiology, University Hospital Coventry and Warwickshire NHS Trust, Coventry, UK. Gordon.mcgregor@uhcw.nhs.uk.
authors.forename: Gordon
authors.initials: G
authors.lastname: McGregor
authors.affiliation: Department of Nephrology, Dorset County Hospital NHS Foundation Trust, Dorchester, UK. charles.weston@dchft.nhs.uk.
authors.forename: Charles
authors.initials: C
authors.lastname: Weston
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. nithya.krishnan@uhcw.nhs.uk.
authors.forename: Nithya
authors.initials: N
authors.lastname: Krishnan
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. Robert.higgins@uhcw.nhs.uk.
authors.forename: Robert
authors.initials: R
authors.lastname: Higgins
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. d.zehnder@warwick.ac.uk.|Division of Metabolic and Vascular Health, The University of Warwick, Coventry, UK. d.zehnder@warwick.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Zehnder
authors.affiliation: Departments of Renal Medicine and Transplantation, University Hospital Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, CV2 2DX, UK. s.ting@warwick.ac.uk.|Division of Metabolic and Vascular Health, The University of Warwick, Coventry, UK. s.ting@warwick.ac.uk.
authors.forename: Stephen M S
authors.initials: SM
authors.lastname: Ting
mesh_terms: D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology* / Q000628:therapy; D001794:Blood Pressure; D015444:Exercise; D005080:Exercise Test; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D018495:Fluid Shifts; D006801:Humans; D007022:Hypotension / Q000503:physiopathology* / Q000628:therapy; D007676:Kidney Failure, Chronic / Q000503:physiopathology* / Q000628:therapy; D016030:Kidney Transplantation; D006435:Renal Dialysis / Q000379:methods*; D016896:Treatment Outcome; D014655:Vascular Resistance