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Renal Association UK Renal Registry . Blood pressure and mortality risk in peritoneal dialysis patients in England and Wales. Udaya P.Udayaraj , R.Steenkamp, F.Caskey, D.Ansell, C.Tomson UK Renal Registry, Bristol, UK www.renalreg.org. Renal Association

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Blood pressure and mortality risk in peritoneal dialysis patients in England and Wales

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Blood pressure and mortality risk in peritoneal dialysis patients in england and wales l.jpg

Renal Association

UK Renal Registry

Blood pressure and mortality risk in peritoneal dialysis patients in England and Wales

Udaya P.Udayaraj, R.Steenkamp, F.Caskey,D.Ansell, C.Tomson

UK Renal Registry, Bristol, UK

www.renalreg.org


Introduction l.jpg

Renal Association

UK Renal Registry

Introduction

  • General population – linear or ‘J’ shaped association of BP with mortality

Lewington et al. Lancet, 2002; 360:1903-13


Introduction3 l.jpg

Renal Association

UK Renal Registry

Introduction

  • ‘Reverse J’ or ‘U’ association well described in hemodialysis (HD) patients

Zager et al. KI,1998;54:561-69

Kalantar-Zadeh. Hypertension, 2005;45:811-17


Introduction4 l.jpg

Renal Association

UK Renal Registry

Introduction

  • Is this ‘reverse’ association related to HD procedure?

    • Creation of AV fistula can predispose to myocardial ischemia‡

    • Hypotension during HD can precipitate myocardial ischemia * and is associated with increased mortality †

  • ‡ Savage et al. AJKD 2002; 40: 753-59

  • * Selby et al. Semin Dial 2007; 20:220-28

    • † Shoji et al. KI 2004; 66:1212-20


  • Introduction5 l.jpg

    Renal Association

    UK Renal Registry

    Introduction

    • Previous studies in peritoneal dialysis (PD) patients – inconsistent results due to small sample size †or short follow up ‡

    • Low BP associated with lower mortality in kidney transplant recipients

    • Association of BP and survival amongst dialysis patients awaiting transplantation is not known

    • † Lynn et al. KI 2002;62:2281-2287

    • Ates et al. Kidney Int 60: 767-776, 2001

    • Jager et al. Kidney Int 55: 1476-1485, 1999

    • ‡ Rumyantazev et al. NDT 2005;20:1693-1701

    • Rocco et al. Perit Dial Int 22: 371-379, 2002


    Slide6 l.jpg

    Renal Association

    UK Renal Registry

    Aim

    To study the association of BP and mortality in

    • a larger cohort of peritoneal dialysis patients

    • a subgroup of patients who are registered on the kidney transplant waiting list


    Methods databases l.jpg

    Renal Association

    UK Renal Registry

    Methods (Databases)

    • UK Renal Registry (UKRR)

      • Established in 1997

      • 100 % coverage of England and Wales expected by 2007

      • Fully electronic data extraction from clinical information system

      • Quarterly biochemical and clinical data on all patients on renal replacement therapy (RRT)

    • UK Transplant (UKT)

      • Maintains national organ donor register

      • Holds data on kidney transplant waiting list


    Study population l.jpg

    Renal Association

    UK Renal Registry

    Study population

    Incident RRT patients 1997-2004 in England and Wales

    • Inclusion criteria

      • From centres with >85% ethnicity data completeness †

      • Age >18 years

      • On Peritoneal dialysis at day 90

    • Exclusion criteria

      • Missing data on age/gender/ cause of renal failure/ethnicity

      • Transplant prior to day 90

      • Missing BP data in 1st or 2nd quarter

        † No difference in survival or baseline characteristics of patients in centres with > 85 % and < 85% data


    Statistical analysis l.jpg

    Renal Association

    UK Renal Registry

    Statistical analysis

    • BP measurements

      • Mean BP value in the 1st/2nd quarter of RRT

      • Systolic, Diastolic, Mean arterial and pulse pressure studied

    • Cox regression model

      • BP as a continuous variable ( linear and non linear terms)

      • Factors adjusted in multivariate model

        • Age, gender, ethnicity, cause of renal failure, haemoglobin, corrected calcium, phosphate, serum albumin

        • Change of RRT modality as time dependent variable ( i.e. patients not censored at modality change)

        • Time to inclusion on Transplant waiting list as surrogate for co-morbidity


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    Renal Association

    UK Renal Registry

    • Outcome

      • All cause mortality after day 90

      • All patients followed until 31.12.05 or death

    • Subgroup analyses

      • Diabetics and non diabetics

      • Transplant waiting list registration status in 1st year of RRT ( all cause mortality from 1 year after start of RRT)

        • Waitlisted within 1st year from start of RRT

        • Not waitlisted within the 1st year from start of RRT


    Results study cohort l.jpg

    Renal Association

    UK Renal Registry

    Results(Study cohort)

    Cohort selection no. of patients

    included

    PD at day 90 ( centres >85 % ethnicity data) 3,991

    With data on ethnicity, cause of renal failure,3,822

    previous transplant

    With SBP/DBP data* 2,061

    With data on lab parameters and date of 2,035

    Transplant waitlisting

    * No difference in baseline characteristics and survival between those included and excluded except % males was more in excluded cohort (62.8% vs 58.2%)


    Baseline characteristics l.jpg

    Renal Association

    UK Renal Registry

    Baseline Characteristics


    Slide13 l.jpg

    Renal Association

    UK Renal Registry

    Cox regression models

    P< 0.0002

    P= 0.01

    †Adjusted for age, gender, cause of renal failure, ethnicity, lab parameters, treatment modality, time to transplant waiting list


    Slide14 l.jpg

    Renal Association

    UK Renal Registry

    Cox Regression models

    P= 0.0007

    P=0.05

    †Adjusted for age, gender, cause of renal failure, ethnicity, lab parameters, treatment modality, time to transplant waiting list


    Subgroup analyses time to transplant waiting list wl l.jpg

    Renal Association

    UK Renal Registry

    Subgroup analyses – Time to transplant waiting list (WL)

    P =0.07

    p =0.01

    P= ns

    P = ns

    WL < 1 year (n=675) HR per 10 mmHg 1.14, 95 % CI 0.99-1.31

    HR per 10 mmHg 1.29, 95 % CI 1.05-1.59

    p =0.01

    HR per 10 mmHg 1.33, 95 % CI 1.07-1.67

    P = ns

    † Survival after 1 year, Adjusted for age, gender, cause of renal failure, ethnicity, lab parameters, treatment modality


    Subgroup analyses diabetes l.jpg

    Renal Association

    UK Renal Registry

    Subgroup analyses - Diabetes

    • Diabetic – no association of any BP component with mortality

    • Non diabetic – U shaped for SBP and reverse J for MAP (as for entire study cohort)

    † Adjusted for age, gender, ethnicity, lab parameters,treatment modality, time to transplant waiting list


    Summary l.jpg

    Renal Association

    UK Renal Registry

    Summary

    Pattern of association of BP and mortality was

    • For the entire study population

      • U shaped for SBP

      • Reverse J for MAP

      • No association for DBP and PP

    • For those registered on the transplant waiting list within first year

      • Linear for SBP, DBP, MAP

      • No association for PP

    • For patients with diabetes

      • No association with any BP components


    Slide18 l.jpg

    Renal Association

    UK Renal Registry

    • Strengths

      • Largest study to date on PD patients

      • First to describe the association of BP and survival in patients on the transplant waiting list

      • Novel analytic strategy of adjusting for modality change allowed extended follow up of patients without censoring

    • Limitations

      • BP measurement not standardised

      • Lack of data on co-morbidity, residual renal function dialysis dose

      • No data on cardiac function or anti HT medications


    Conclusions l.jpg

    Renal Association

    UK Renal Registry

    Conclusions

    • High and low SBP are risk factors for increased mortality in incident PD patients

    • Low SBP was not associated with increased mortality in a subgroup of patients activated early on the transplant waiting list

    • Association of low SBP and mortality seen in entire study cohort could reflect poor cardiac function/ health status

    • The BP associated with best survival may vary for different patient subgroups


    Baseline characteristics21 l.jpg

    Baseline Characteristics


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