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CHRISTMAS BMJ 2010 Urine output on an intensive care unit: case-control study

CHRISTMAS BMJ 2010 Urine output on an intensive care unit: case-control study. Dr Yvette Ruddock F2. Background. Increasing numbers of patients Staffing Increasing workloads Overworked juniors! Are we so overworked that we cannot maintain an adequate fluid intake?!. Patients in ITU.

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CHRISTMAS BMJ 2010 Urine output on an intensive care unit: case-control study

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  1. CHRISTMAS BMJ 2010Urine output on an intensive care unit: case-control study Dr Yvette Ruddock F2

  2. Background • Increasing numbers of patients • Staffing • Increasing workloads • Overworked juniors! • Are we so overworked that we cannot maintain an adequate fluid intake?!

  3. Patients in ITU • Multiple risk factors for AKI • RIFLE criteria • “At risk” 17% • “In injury” 11%

  4. Study Details • Aim- To compare UO between junior dr’s + pt’s in an intensive care unit • Setting-General ICU tertiary referral hospital • Design-Case control study

  5. Methods • Cases- dr’s (volunteers) Controls-Pt’s • Ex criteria-pregnancy -gfr<15 ml/min/1.73m2 -RRT • Over 22 consecutive weekdays • Cases/controls matching→acc to clerking • 19 dr’s, 87 cases days • 195 control days

  6. Methods • Pts→catheterised→continuous UO • Dr’s →Void on arrival at work, if needed during their shift, then compulsory voiding at end of shift. • Each voiding of urine by dr’s measured and recorded • Control data →0800-2000 • Dr Shifts →0800 upto 1800 • Stratum →logistic regression, sandwich estimator

  7. Outcome Measures 1) Oliguria mean UO <0.5ml/kg for each of six consecutive hrs 2) Is urine output(as a continuous variable) lower in cases than controls?

  8. Results • Case days • Mean UO 0.77 ml/kg/hr • Median UO 0.68 ml/kg/hr • Cases →Oliguric and “risk of aki” in 19(22%) case days, in “injury” 1 day • Controls →Oliguric 29(15%) control days

  9. Results • Odds ratio (in the presence of oliguria) for being a case not a control 1.99 (p=0.03 95% CI 1.08-3.68) • For each additional 1ml/kg/hr of UO the odds ratio of being a case not a control was 0.27 (p=0.001 95%CI 0.12-0.58)

  10. Strengths • Interesting study • Clearly defined objective and outcome measures • CI and P values stated • CI and p <0.05

  11. Weaknesses • Small study-power? • Bias-recruitment • -data collection • -non blinded • Weak matching of cases and controls • Comparing two completely different groups • What is the exposure? • Is this the correct study design?

  12. Weaknesses • Ended early • Missing data-forgetting to measure • Accuracy of UO when not measured as a continuous variable • What about creatinine? • Stats • Cause?

  13. Relevance • Does this matter? (i.e. who cares!) • No mortality in the ‘cases’

  14. Conclusion • Interesting study highlighting that juniors may neglect (reasons not specified) to maintain adequate hydration so much that they are fluid depleted which is detected physiologically with a reduced UO.

  15. Summary • Lighthearted • Small study • Multiple sources of bias • Cases and controls not comparable

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