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pH Testing to confirm Nasogastric Tube Position on ICU. Are we wasting our time?

pH Testing to confirm Nasogastric Tube Position on ICU. Are we wasting our time?. Mr. Samuel George Intensive Therapy Unit, Morriston Hospital Swansea. Background. ESPEN guidelines 2006 All patients not expected to achieve oral diet in 3 days - started on enteral nutrition

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pH Testing to confirm Nasogastric Tube Position on ICU. Are we wasting our time?

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  1. pH Testing to confirm Nasogastric Tube Position on ICU.Are we wasting our time? Mr. Samuel George Intensive Therapy Unit, Morriston Hospital Swansea

  2. Background • ESPEN guidelines 2006 • All patients not expected to achieve oral diet in 3 days - started on enteral nutrition • NG feeding - main route on ICU • NPSA Guidelines 2005 • “Placement of NG tubes together with confirmation of correct placement can carry significant risks. “

  3. Background • NPSA alert 2011 • 21 deaths and 79 cases of harm between 2005 and 2010 • Main causal factor – misinterpretation of X-ray • 7 cases (2 deaths) from feeding despite obtaining aspirate pH of between 6-8 • ‘Whoosh’ tests, litmus paper, or interpretation of the appearance of aspirate should NEVER be used • NPSA guidelines • Measuring pH of aspirate 1stline - “Only reliable method of confirming NG tube position” (safe range - 1 and 5.5) • X-rays 2nd line - when aspirate unattainable or high pH

  4. pH Testing • Colorimetric pH strips • (Blue litmus paper insufficient and unsafe) • 0.5 gradations • Colour change - easily distinguishable (esp. between 5-6) • Aspirate between 0.5-1ml required

  5. Frequency of pH Testing • Position checked: • Following insertion • Before each feed/medication • At least once daily during continuous feed • Suspicion of displacement (vomiting, coughing, etc)

  6. Aims/Objective • To assess usefulness of pH testing of NG aspirate in ICU patients

  7. Materials and Methods • Proforma for data • Medication • Type of tube • Type of feed • Volume of aspirate • pH readings on first insertion • pH readings on daily /routine checks • Any change in management?

  8. Morriston ICU Protocol • All new NG’s – CXR • Daily / routine pH testing - although in protocol – not strictly adhered to…

  9. Results

  10. Results • 168 separate pH readings - 41 ICU patients receiving continuous enteral nutrition • 18 readings from new NG • 150 readings from “old” NG

  11. Results – Type of NG • 141 (84%) had Ryles tubes • 27 (16%) had fine bore feeding tubes.

  12. Volume of Aspirate – Large v’s Fine Bore • 36/141 (25%) of large bore tubes - less than 10mls aspirated • 10/27 (37%) fine bore tubes - less than 10mls aspirated

  13. Results – New NG tubes • 14 / 18 (77%) new tube insertions – on PPI’s • 18 readings were taken after a new NG tube was inserted

  14. Results – Replacement of NG • In 2/85 high pH readings • feed stopped and new NG inserted • pH in these 2 cases - 6 and 7.5 • Remaining 83 high pH readings • feed was continued and no action taken • Despite this - NO adverse events

  15. Discussion • Most ICU patients - continuous feed and PPI’s • Significant numbers have very low aspirate volumes – especially fine bore tubes • Old tubes - 50% have a high pH • New tubes - 28% have a high pH

  16. Discussion • NPSA guidelines – pH 6 or more feed should be stopped for an hour then retested • 50.5% of readings were pH 6 – but in the majority feed was continued • BUT – NO adverse events • i.e. probable falsely high readings • Stopping feed would have caused unnecessary interruption of patients nutrition

  17. Conclusions • High pH readings in ICU patients probably reflects continuous feeding and stress ulcer prophylaxis regimes. • The value of pH testing in these patients is limited.….especially in daily checks • ICU specific guidelines needed…..

  18. Other Welsh ICU’s A Telephone Survey

  19. Other Welsh ICU’s • 13 units contacted • Data obtained from 12 units • 1 unit declined to participate

  20. Other Welsh ICU’s • Initial insertion • All units obtain X-rays

  21. Other Welsh ICU’s • Routine / daily testing. • 4 units confirm NG position routinely by pH testing (1-4 times a day) • 3 units routinely aspirate only to confirm position • 2 units routinely measure tube length at nose • 4 units do not routinely check NG position with patients on continuous feeding

  22. Other Welsh ICU’s • Routine / daily testing (cont.) • All but 1 unit use X-rays as a 2nd line method of confirming NG position • One unit uses litmus paper

  23. Summary of Survey • Wide variation in practice • NPSA Guidelines not being followed • Patients at risk

  24. Possible Guideline for ICU’s • New NG • use pH as 1st line and x-ray as 2nd line • Daily / routine checks - Screeningtool • 1. No reason to suspect displacement i.e. no prolonged coughing or retching etc • 2. NG tapes or fixation devices are secure and have not moved. • 3. Identical insertion length to that recorded on initial placement • Only if all three of above are satisfied -further use of the NG can occur.

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