Gastric tonometry
USES
- a method of assessing regional hypoperfusion
DESCRIPTION
- modified NG tube with a silicone balloon 14.4cm from the tip
- gastric mucosal CO2 equilibrates luminal CO2, which equilibrates with fluid or air in the balloon
- CO2 is measured via an infra-red CO2 analyser
- intramucosal pH is then calculated using the Henderson-Hasselbalch equation
- goal was to achieve a intramucosal pH of > 7.3 but this relied on use of arterial HCO3- as a surrogate for mucosal HCO3
- then point of monitoring is now the arterial-mucosal CO2 gap (normally 8-10mmHg)
METHOD OF INSERTION AND/OR USE
- splanchnic hypoperfusion occurs early in circulatory shock -> intramucosal hypercapnia and acidosis.
OTHER INFORMATION
COMPLICATIONS
Flaws
- requires N/G tube
- signal degradation by luminal contents (feed, blood)
- feed must be stopped for 2 hours prior to measurement
- inability to identify a clear hypoxic threshold (empiric goal = a CO2 gap of < 25mmHg)
- a need to suppress luminal CO2 generation by HCl titration of duodenal bicarbonate
- a lack of convincing evidence that tonometry guided therapy improves outcome
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC