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 NG feeding - main route on ICU NPSA Guidelines 2005 – “Placement of NG tubes together with confirmation of correct placement can carry significant risks. “

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 1 st line - “Only reliable method of confirming NG tube position” (safe range - 1 and 5.5) – X-rays 2 nd line - when aspirate unattainable or high pH

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

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)

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

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? Materials and Methods

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

Results

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

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

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

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

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

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

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

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…..

Other Welsh ICU’s A Telephone Survey

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

Other Welsh ICU’s Initial insertion – All units obtain X-rays

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

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

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

Possible Guideline for ICU’s New NG – use pH as 1 st line and x-ray as 2 nd line Daily / routine checks - Screening tool – 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.