How bad is the weekend break?

Sunday, September 25, 2011
How bad is the long break for dialysis patients?

In this week’s NEJM, Foley and colleagues published a retrospective analysis of the End-Stage Renal Disease Clinical Performance Measures Project (CPM) cohort examining the association of the long interdialytic break (i.e. Friday to Monday for MWF patients and Saturday to Tuesday for TTS patients) and clinical outcomes. The study is already receiving plenty of press (Forbes.com, LA Times) and should be read by all.

Before diving into the study mechanics and results, a review of existing data on the “long break” is warranted. Bleyer and colleagues published 2 prior studies examining the timing of hemodialysis (HD) and patient deaths. The first demonstrated a higher rate of cardiac death on Mondays and Tuesdays. In a subsequent analysis, they found that HD patients had a 3-fold increased risk of sudden cardiac death (SCD) in the 12 hours prior to the 1st HD session of the week. In a later study, Karnik and colleagues examined patient and HD-specific factors associated with a higher risk of cardiac arrest and SCD during dialysis. They corroborated Bleyer’s finding of increased deaths on Mondays (but, interestingly, not on Tuesdays) and identified low dialysate potassium, older age, diabetes, catheter use, and intradialytic hypotension as factors associated with sudden death. Similar findings have also been reported in Europe.

With growing evidence that alternative dialysis schedules (daily, nocturnal, quotidian, etc) improve outcomes (specifically LV mass, QOL), the authors of this new study hypothesized that the long interdialytic interval is associated with increased morbidity and mortality.

Study Basics:

-Design: retrospective cohort
-Population: 32,065 thrice-weekly HD patients from the ESRD CPM from 2004-2007
-Aim: compare rates of death and hospital admission on the day following the “long break” to rates on other days
-Outcomes: mortality (all-cause and cause-specific: cardiac, vascular, infectious, other) and hospital admission rates

Study Findings:
Mean age 62.2y, 45.1% women, 36.3% black, 43.7% w/ DM as ESRD primary dx, 27.7% w/ catheter use, mean vintage of 3.8y (24.2% had been on HD <1y), and mean DSL of 217min

Mean follow-up time: 2.2

Mortality rate: 41.1%

o Cardiac cause: 17.4%
o Vascular cause: 2.7%
o Infectious cause: 4.8%

Event (selected)
Event on Day after Long Break (Rate per 100 Person-Yr)

Yes
No
P-value

All-cause Mortality
22.1
18
<0.001

Cardiac Mortality
10.2
7.5
<0.001

Infectious Mortality
2.5
2.1
0.007

Cardiac Arrest
1.3
1.0
0.004

Myocardial Infarction
6.3
4.4
<0.001

Septicemia
1.2
1.0
0.06

Hospitalization- MI
6.3
3.9
<0.001

Hospitalization- CHF
29.9
16.9
<0.001

Hospitalization- Dysrhythmia
20.9
11.0
<0.001

Limitations:

· Retrospective nature (potential residual confounding)

· Misclassification due to limitations in outcome adjudication (ICD-9 codes, CMS death forms)

· Study suggests association but not causation and provides little data to suggest the mechanism

Conclusion:
The long 72 hour interdialytic interval is associated with higher all-cause, cardiovascular, and infectious mortality as well as with higher rates of cardiovascular related hospitalizations

Potential Mechanisms: (almost all of which deserve further study)

· Elevated potassium levels and associated membrane destabilization

· Potassium shifts (high serum K+ against a low, and often unadjusted dialysate K+)

· High fluid burden and associated cardiac myofiber stretch and stress to the conduction system

· High ultrafiltration rates and associated cardiac stunning

· Catecholamine and cortisol surges and enhanced sympathetic nervous activation

Now What?
There is no doubt that a randomized trial of session timing, length, and schedule is needed. This new study provides further justification (and “clinical equipoise” as noted by the authors) for such. In the meantime, we are mired in a delivery system driven by strict schedules and tight budgets. What do we tell our patients? How do we alter practice now within the confines of the current system? Here are some thoughts:

· Potassium-directed (for patients w high pre-dialysis K+)

o More frequent monitoring of pre-HD K+ and subsequent tailoring of dialysate K+
o Avoidance of 0-1meq K+ dialysate baths
o K+ profiling to maintain a constant K+ gradient
o Target colonic excretion (bisacodyl for ex) of K+ over the long break

 · Fluid-directed (for patients with high inter-dialytic weigh gain)
o Strict fluid and salt restrictions
o Extended dialysis session length to minimize ultrafiltration rates
 · Alternative schedules
o Additional weekly session
§ Justified under current Medicare policy for patients w large weight gain, intolerance to ultrafiltration, and intradialytic hypotension
o Encourage home HD and PD for appropriate patients

What's next?: Further research is NEEDED before wide-spread practice alteration is warranted particularly given the profound policy implications, but our patients deserve this now. Specifically, we must determine:

o Optimal dialysis scheduling
o Patient preferences regarding frequency and duration (i.e.... will they come??)
o Cost-effectivness analyses (will more frequent HD reduce morbidity and thus cost?)

Posted by Jenny Flythe

(I'm not really good at copying and pasting stuff, particularly when there are graphs and statistics involved, so you might want to go to the Renal Fellow Network's site and read this article there. The comments are interesting, too.

http://renalfellow.blogspot.com/2011/09/how-bad-is-long-break-for-dialysis.html )