Gastric Tonometry and Enteral Nutrition: a Possible Conflict in Critical Care Nursing Practice

Effect of Feeding and Suction on Gastric Impedance Spectroscopy Measurements

A specific device and system has been developed and tested for clinical monitoring of gastric mucosal reactance in the critically ill as an early warning of splanchnic hypoperfusion associated with shock and sepsis. This device has been proven effective in clinical trials and is expected to become commercially available next year. The system uses a combination nasogastric tube and impedance spectroscopy probe as a single catheter. Because this device has a double function, the question is: Does enteral feeding or suction affect the gastric reactance measurements? This study was designed to evaluate the effect of feeding and suction on the measurement of gastric impedance spectroscopy in healthy volunteers. Impedance spectra were obtained from the gastric wall epithelia of 18 subjects. The spectra were measured for each of the following conditions: postinsertion of gastric probe, during active suction, postactive suction, and during enteral feeding (236 ml of nutritional supplement). Impedance spectra were reproducible in all volunteers under all conditions tested. There was a slight increase in impedance parameters after suction, and a decrease in impedance after feeding; however, these observed differences were insignificant compared to patient-to-patient variability, and truly negligible compared with previously observed changes associated with splanchnic ischemia in critically ill patients. Our results demonstrate that suction or feeding when using the impedance spectro-metry probe/nasogastric tube does not significantly interfere with gastric impedance spectrometer measurements.

Gastric feeding intolerance is not caused by mucosal ischemia measured by intragastric air tonometry in the critically ill

BACKGROUND

Gastric mucosal ischemia may be a risk factor for gastrointestinal intolerance to early feeding in the critically ill.

AIMS

To study intragastric PCO2 air tonometry and gastric residual volumes (GRV) before and after the start of gastric feeding.

METHODS

This is a two-center study in intensive care units of a university and teaching hospital. Twenty-nine critically ill, consecutive and consenting patients scheduled to start gastric feeding were studied after insertion of a gastric tonometry catheter and prior to and after start of gastric feeding (500 ml over 1 h), when clinically indicated.

RESULTS

Blood gasometry and intragastric tonometry were performed prior to and 2 h after gastric feeding. The intragastric to arterial PCO2 gap (normal <8 mm Hg) was elevated in 41% of patients prior to feeding and measured (mean ± standard deviation) 13 ± 20 and 16 ± 23 mm Hg in patients with normal (<100 ml, 42 ± 34 ml, n = 19) and elevated GRV (250 ± 141 ml, n = 10, P = 0.75), respectively. After feeding, the gradient did not increase and measured 27 ± 25 and 23 ± 34 mm Hg, respectively (P = 0.80).

CONCLUSION

Gastric mucosal ischemia is not a major risk factor for intolerance to early gastric feeding in the critically ill.

Reliability of measurement techniques for the hepato-splanchnic region in multiple-trauma patients

PURPOSE

Relevant information on the adequacy of intestinal perfusion is needed. The objective of our study was to investigate the relationship between the difference in intra-mucosal and arterial CO2 pressure (pCO2 gap) and the outcome in multiply injured patients and relations between the pCO2 gap and intestinal permeability (IP).

METHODS

Forty consecutive multiply injured patients, admitted to the intensive care unit (ICU) of the University Medical Centre Ljubljana, were studied prospectively. On days 2 and 4, IP was measured using the lactulose-mannitol (L/M) test. For 4 days, the pCO2 gap was measured using air tonometry. Multiple organ failure (MOF) scores were calculated daily.

RESULTS

No significant differences in the MOF scores and length of ICU stay were found between the groups formed with respect to the presumably normal pCO2 gap value of 1.33 kPa. The baseline pCO2 gap difference in patients with abdominal injuries was significantly (p = 0.01) higher in comparison with those without abdominal injuries. There was no correlation between the pCO2 gap values and L/M index measured simultaneously and also between the baseline and average pCO2 gap and L/M index measured on days 2 and 4. We were unable to find any association between the MOF score and pCO2 gap. The MOF score, however, correlated significantly with the L/M value determined on day 4 (r = 0.85, p = 0.02). The average gastric retention volume was inversely correlated with the average pCO2 gap (r = -0.33, p = 0.04).

CONCLUSIONS

The pCO2 gap in trauma patients on intra-gastric enteral nutrition in the phase of present technical solutions has no prognostic value for the development of MOF, but IP correlated with it.

Gastric tonometry and monitoring gastrointestinal perfusion: using research to support nursing practice

The principles and physiological underpinnings of gastric tonometry are reviewed. Tonometric variables, including the PtCO2, pHi and CO2 gap, are described and critiqued as measurements of gastrointestinal perfusion. Increases in gastrointestinal CO2 unrelated to gastrointestinal hypoperfusion are discussed within different clinical contexts. The technical limitations of gastric tonometry, including procedural errors and PtCO2 measurement are discussed in relation to the accuracy of tonometric measurements. Tonometric measurement using semi-continuous air tonometry is introduced as a strategy to minimize technical limitations.