Measurement Of Gastric Intramucosal pH Research Articles

Perfusion of the gastric conduit during esophagectomy.

In esophageal cancer surgery, perfusion of the gastric conduit is a critical issue. Measurement of gastric intramucosal pH (pHi) is a method to identify anaerobic metabolism as a sign of impaired perfusion. In this study we aimed to monitor changes in the perfusion of the gastric conduit at key steps during and after esophagectomy. pHi was measured per- and postoperatively using intermittent gastric tonometry in 32 patients undergoing open, 65%, or video-assisted thoracoscopic esophagectomy for esophageal cancer. Measurements focused on the surgical steps when the vascular supply to the gastric conduit was altered. A tonometry catheter was successfully placed in all patients and a decrease in pHi (mean±SD) was observed from baseline to after the division of the short gastric vessels (7.33±0.07 to 7.29± 0.07, P =0.005). A further reduction after the ligation of the left gastric artery (7.26±0.08, P <0.001) and after final linear stapling the gastric conduit (7.15±0.13, P <0.001) was observed. Two hours after surgery, pHi increased (7.24±0.09, P =0.002). In contrast to open surgery, a trend towards less reduction in pHi was seen in thoracoscopic surgery. Patients with anastomotic leaks had lower pHi on the first postoperative day (7.12±0.05 vs. 7.27±0.08, P =0.040). It can be concluded that each surgical step altering the vascular supply to the gastric conduit resulted in detectable changes, however transient, in pHi. Patients with low pHi on the first postoperative day were more prone to have clinically relevant anastomotic leaks.

Validity of gastric intramucosal pH (pHi) for circulatory evaluation in pediatric patients.

To determine if the measurement of gastric intramucosal pH (pHi) is useful for evaluation of circulatory status of critically ill pediatric patients. Prospective clinical study. General intensive care unit in a university hospital. Seven pediatric patients (mean age: 2 y.o.); six post-cardiac surgery, one receiving barbiturate therapy. Tonometric catheters were placed via nasogastric approach. pHi was measured after confirmation of the catheter position by X-ray. Saturation of venous blood oxygen (SvO2), arterial keton body ratio (AKBR), serum lactate level and pHi were evaluated simultaneously. No patients survived with pHi below 7.22; pHi above 7.11 significantly correlated with SvO2 values (r = 0.814, p < 0.001); pHi below 7.11 did not show any significant correlation with SvO2. Whereas SvO2 values of under 40% were distributed in the pHi range from 7.11 to 7.19, pHi below 7.11 occurred when SvO2 values were more than 40%. AKBR and serum lactate level did not correlate with pHi. pHi can be a useful parameter for evaluating the circulatory status of critically ill pediatric patients; it allows reliable evaluation of splanchnic and peripheral perfusion.

Measurement of Gastric PCO2 as an Index of Tissue Hypoxia during Obstructive Sleep Apnea

Background: Gastric mucosal ischemia develops in critically ill patients in a number of clinical settings due to diversion of blood flow from the splanchnic bed to more vital organs, and can be detected by the measurement of gastric intramucosal pH (pHi). Study Objective: We hypothesized that similar changes would occur during obstructive sleep apnea (OSA) due to increased respiratory work during the periods of apnea. Methods: Gastric P_co2, pHi and arterial blood gases were measured during 3 conditions in 8 patients with severe OSA: at baseline awake, while asleep with ≧30 obstructive apneas or hypopneas per hour, and asleep after elimination of apneas with continuous positive airway pressure (CPAP). Results: Significant changes between the baseline and apnea conditions were detected using ANOVA for repeated measures for gastric P_CO2, 40.2 ± 5.3 vs. 85.4 ± 34.0 (p < 0.001), pHi, 7.41 ± 0.06 vs. 7.11 ± 0.17 (p < 0.005), and the gastric-arterial P_CO2 difference (D_CO2), –2.3 ± 5.5 vs. 44.3 ± 36.21 (p < 0.006). Nasal CPAP returned all measures back to baseline values. Conclusions: Gastric tissue hypoxia develops in patients with severe OSA and may be a marker of disease severity. Treatment of OSA with CPAP eliminates the regional tissue hypoxia.

Tonometric measurement of gastric intramucosal pH following oesophagectomy predicts postoperative complications

Abstract Background Gastric mucosal hypoperfusion can be assessed tonometrically by measuring the gastric intramucosal pH (pHi); its ability to predict outcome in the critically ill has been demonstrated previously. This study employed the new technique of recirculating gas tonometry to measure gastric pHi following oesophagectomy; its ability to predict anastomotic complications was tested, since ischaemia at the oesophagogastric anastomosis is thought to be an important factor in their aetiology. Methods A gastric tonometer was placed in the gastric tube of 28 consecutive patients undergoing oesophageal resection. They were connected to a Tonacap analyser (Datex-Engstrom Division, Instrumentarium Corporation, Helsinki, Finland) which automatically samples gas from the intragastric tonometer balloon and measures the carbon dioxide concentration within it. In conjunction with simultaneously taken arterial blood samples, gastric pHi was calculated at the end of the operation and then at 12-h intervals for up to 48 h after operation. Patients who survived were followed for 3 months and all postoperative complications were recorded. Statistical comparison was made using the independent samples t test. Results Eight patients suffered an anastomotic leak or benign stricture after operation; five others had a life-threatening complication not thought to be related to the anastomosis, of whom two survived. Over the first 24 h after operation median gastric pHi was lower at all three measurement points in the complication group than in the no complication group (P &amp;gt; 0·05 in all cases). However, at 36 and 48 h there were significant differences (in both cases P &amp;lt; 0·01); at these times median (range) pHi in the complication group was 7·19 (7·00–7·24) and 7·20 (7·03–7·49) respectively, and in the no complication group 7·28 (7·12–7·39) and 7·32 (7·25–7·44). A mean pHi at 36 and 48 h after operation of 7·25, with both measurements less than this value as a discriminating coefficient, was employed. This had a sensitivity of 92 per cent and a specificity of 92 per cent for predicting all complications. Applied specifically to anastomotic complications the sensitivity was 100 per cent and specificity 92 per cent. Conclusion Gastric pHi is easily measured after operation using recirculating gas tonometry. By taking measurements at 36 and 48 h, it appears possible to predict postoperative complications following oesophagectomy and the technique may provide a useful adjunct to the monitoring of these patients.

A Randomized and Controlled Trial of the Effect of Treatment Aimed at Maximizing Oxygen Delivery in Patients With Severe Sepsis or Septic Shock

To evaluate the effects of increased oxygen delivery on mortality and morbidity. Randomized, controlled trial. Medical-surgical ICU of a tertiary care hospital. Sixty-three patients classified according to predetermined criteria as having severe sepsis or septic shock. The patients were randomly assigned to one of two groups: the control group (n = 32) received conventional therapy with a normal targeted value of oxygen delivery, and the treatment group (n = 31) received therapy with a targeted oxygen delivery index (DO2I) value of > 600 mL/min/m2. The therapeutic approach to maintain BP, arterial saturation, hemoglobin concentration, and pulmonary artery occlusion pressure was similar in both groups. The hemodynamic, oxygen transport, and gastric intramucosal pH measurements were recorded at the time of admission to the study and every 6 h for the next 96 h. The outcome measures were the rate of patient mortality and the number of organ dysfunctions occurring during the ICU stay. The study groups were similar with respect to demographics and admission hemodynamic variables, but the percentage of patients with positive blood cultures was significantly higher in the control group than in the treatment group, respectively: 34 vs 13% (p = 0.04). The average cardiac index was significantly higher in the treatment group than in the control group, respectively: 3.96 vs 3.05 L/min/m2 (p = 0.01). This factor did not significantly affect the DO2I. Nine of the 31 treatment group patients reached an average DO2I value of > 600 mL/min/m2. The rate of mortality in the control group patients up to the time of ICU discharge (66%) was similar to that seen in the treatment group (74%), respectively: 21 of 32 vs 23 of 31 (p = 0.46). The number of dysfunctional organs per patient was also similar in the control and treatment groups, respectively: 2.1+/-1.1 vs 2.6+/-1.2 (p = 0.12). Treatment aimed at maximizing oxygen delivery in patients with severe sepsis or septic shock does not reduce mortality or morbidity.

Gastric tonometry: in vivo comparison of saline and air tonometry in patients with cardiogenic shock

Measurement of gastric intramucosal pH (pHi) has been advocated to assess gastric perfusion. Regional PCO2 (rPCO2) values are measured using saline tonometry (rsPCO2) and more recently using air tonometry (raPCO2). We compared 237 measurements of saline and air tonometry in 19 consecutive, severely ill patients (mean age 59 (range 31-76) yr, 19 males, APACHE II 22 +/- 7) with cardiogenic shock. Equilibration period was set to 90 min. Nineteen independent paired samples of mean raPCO2 and mean rsPCO2 of each patient showed good correlation (r = 0.93, P < 0.001). Mean raPCO2 was 6.5 (1.8) kPa and mean rsPCO2 6.8 (2.4) kPa. PCO2 measured by saline was significantly higher than that measured by air (P < 0.05). Bland and Altman analysis showed a bias (mean rsPCO2-mean raPCO2) of 0.3 kPa and a precision of 1.2 kPa. Agreement between the two methods decreased with increasing rPCO2 concentrations. Although air tonometry of rPCO2 is a promising technique, a systematic disagreement with saline tonometry at high rPCO2 values requires further investigation and cautious interpretation of these values.

Gastric intramucosal pH: A predictor of survival in cardiac surgery patients with low cardiac output?

Objective: To assess the value of gastric intramucosal pH measurement in patients with low output after cardiac surgery. Design: Prospective clinical study. Setting: University hospital. Participants: Fifteen patients with low output after cardiac surgery were included. Those who survived the first postoperative day ( n = 14) remained in the study. Interventions: Gastric intramucosal pH and arterial lactate concentrations were measured 6, 12, and 24 hours after admission to the intensive care unit. Intravenous infusion of buffer solutions was strictly avoided during the equilibration period and in the half hour before injection of saline into the gastric balloon of the tonometer. Measurements and Main Results: Eight patients survived during the 28-day observation period, and six patients died. On admission to the intensive care unit, no difference in cardiac index (1.56 v 1.54 L/min/m 2) or pulmonary capillary wedge pressure (17.3 v 17.7 mmHg) was found between survivors and nonsurvivors. During the first 24 hours after surgery, arterial lactate was significantly higher in the nonsurvivor group (61 v 23 mg/dL), but there was no difference between the gastric intramucosal pH of survivors and nonsurvivors (7.41 v 7.42 on admission). Conclusions: Calculated gastric mucosal pH is not an early predictor of survival in cardiac surgery patients with postoperative low cardiac output syndrome. Further studies are required to assess whether the gradient between arterial and intramucosal partial pressure of carbon dioxide (Pco 2) might be a more useful predictive value.

Equipment review: Gastric intramucosal pH measurement

IntroductionGastric tonometry has emerged as an attractive, rela-tively noninvasive technology for assessing gastrointest-inal perfusion and oxygenation by detecting acidosis inthe gut wall. Several clinical studies have shown thatgastric intramucosal acidosis detected by this procedurepredicts increased mortality of critcally ill adults in med-ical and surgical intensive care unit (ICU) settings [1-3],and that it is a better predictor of mortality from criticalillness than other mesures of global oxygen delivery andsystemic hemodynamics [4]. It has also been suggestedthat correcting intramucosal acidosis may increase survi-val in selected critically ill patients [5].The purpose of this review is to discuss factors influ-encing in vivo reliability and variability of gastric tono-metry, and to analyze the causes of the occasionalmisinterpretation of its results.The gastric tonometry technique — causes ofmisinterpretation of the resultsThe measurement of gastric mucosal acidosis by gastrictonometry is based on the principle that the fluid in ahollow viscus can be used to estimate gas tensions inthe surrounding tissues. The main assumption is that,after a given equilibration time, luminal and mucosalCO

Gastric Tonometry

Because tissue hypoxia plays a major role in the morbidity and mortality of critically ill patients, achieving adequate tissue oxygenation is considered the main goal in the intensive care unit during initial management of patients with shock, severe sepsis, trauma, and the multiorgan dysfunction syndrome. Unfortunately, systemic parameters of tissue oxygenation are not reliable enough to represent “true” tissue oxygenation status. Methods developed to monitor oxygen tissue metabolism, such as phos-phorus-31 nuclear magnetic resonance, near-infrared spectroscopy, and tissue Po2 electrodes are still far from clinical application. A new approach to this problem is the measurement of gastric intramucosal pH (pHi) with a gastric tonometer. This device consists of a modified nasogastric tube attached to a silicone balloon that is filled with saline. After an equilibration period, saline solution can be sampled and its Pco2 measured in a blood-gas analyzer. Arterial bicarbonate is simultaneously measured. Gastric pHi is then easily calculated using the Henderson-Hasselbalch equation. Its value has been experimentally validated, comparing it with direct electrode tissue pH measurements. A growing body of evidence supports its clinical value at the present time. Several clinical investigations show that pHi is a sensitive and specific prognostic marker. Gastric pHi behavior is able to predict multiorgan dysfunction and mortality in different groups of critically ill patients. Its use to guide resuscitation maneuvers could contribute to mortality reduction. From the few years of basic and clinical research in which this technique has been used, it appears to be a useful tool to assess tissue oxygenation status.

Gastric intramucosal pH: an indicator of weaning outcome from mechanical ventilation in COPD patients.

The aim of this study was to determine whether gastric intramucosal pH (pHim) and/or gastric intramucosal carbon dioxide tension (PCO2,im) measured by tonometry can be used to predict the success of weaning in chronic obstructive pulmonary disease (COPD) patients. Twenty six consecutive COPD patients, undergoing mechanical ventilation for acute respiratory failure and satisfying the criteria of weaning from mechanical ventilation with nasogastric tonometer in place, were studied. Arterial blood gas values and PCO2,im were measured 24 h before (H-24), just before (H0), and after 20 min of a weaning trial on T-piece (H20min). Weaning failure was defined as the development of respiratory distress and/or arterial blood gas impairments during the first 2 h of spontaneous breathing on T-piece, or reintubation within 24 h after extubation. Between the weaning failure (n = 6) and weaning success (n = 20) groups, there were no differences in blood gas analysis readings at H-24 and H0 before the weaning period, age, Simplified Acute Physiology Score (SAPS) on admission, SAPS on the day of weaning trial, and duration of ventilation. Clinical status, tonometric and arterial gasometric data were similar at H-24 and H0 in all patients. During mechanical ventilation, pHim was < or = 7.30 in patients who failed weaning and > 7.30 in patients who were successfully weaned (p < 0.001; 100% sensitivity and specificity). The threshold value for PCO2,im of 8.0 kPa (60 mmHg) represents a clear demarcation with respect to outcome before the weaning trial. PCO2,im values during mechanical ventilation are significantly different (p < 0.001) between patients who were successfully weaned and those who were not (6.9 +/- 0.9 vs 9.9 +/- 1.1 kPa (51.9 +/- 6.7 vs 74.3 +/- 8.0 mmHg, respectively)). At H20min, pHim and PCO2,im were still statistically different between the weaning failure and the weaning success group. We conclude that measurement of gastric intramucosal pH (or gastric intramucosal carbon dioxide tension) represents a simple and accurate index to predict weaning outcome in chronic obstructive pulmonary disease patients before attempting weaning.

Evaluation of gastric intramucosal pH measurements with tissue oxygenation indices in patients with severe sepsis

In this study tonometric measurements of gastric intramucosal pH (pHi) were compared with oxygen delivery (DO2), oxygen consumption (VO2) and arterial lactate as systemic indices of tissue oxygenation in patients with severe sepsis. Dobutamine was infused at increasing doses of 5-10 μg/kg/min at 60-minute intervals in 24 patients. DO2 was calculated as the product of cardiac index (CI) and arterial oxygen content. VO2 was determined directly from expired gas analysis (mVO2) and, indirectly, by calculating the product of cardiac index (CI) and arteriovenous oxygen content difference (cVO2). pHi was obtained by gastric tonometry. After each dose administration of dobutamine mVO2, cVO2, DO2, lactate levels and pHi were determined. The phenomenon of oxygen supply dependency (OSD), as characterised by a linear relationship, was found when the pooled data of both measured and calculated oxygen consumption were plotted against the corresponding level of oxygen delivery (DO2 to cVO2: y=0.34x-106.4, r=0.05 (p<0...

Evaluation of gastric intramucosal pH measurements with tissue oxygenation indices in patients with severe sepsis

Evaluation of gastric intramucosal pH measurements with tissue oxygenation indices in patients with severe sepsis

Increasing Splanchnic Blood Flow in the Critically III

To assess the effect of low dose dopexamine and dopamine on splanchnic blood flow as measured by gastric intramucosal pH, hepatic metabolism of lidocaine (lignocaine) to monoethylglycinexy-lidide (MEGX), and plasma disappearance rate of indocyanine green (ICG). Single-blind randomization of patients with a gastric intramucosal acidosis to receive dopexamine (ten patients), dopamine (ten patients), or saline solution (five control patients) for 2 h. All 25 patients were in the ICU of Guys' Hospital. All patients met the criteria for the diagnosis of the systemic inflammatory response syndrome, were mechanically ventilated, and had pulmonary artery catheters placed. All had a low gastric intramucosal pH and had a median first 24-h acute physiology and chronic health evaluation (II) score of 22 (range, 7 to 40). Baseline measurements of gastric intramucosal pH, MEGX formation from lidocaine, ICG plasma disappearance rate, heart rate, mean arterial pressure, pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, oxygen uptake index, systemic vascular resistance, and arterial pH were taken. Dopexamine (1 mg.kg-1.min-1), dopamine (2.5 mg.kg-1.min-1), or 0.9% saline solution was then infused for 2 h, after which a repeated set of the measurements was taken. Dopexamine at a low dose had no effect on any of the systemic measurements. The median intramucosal pH rose from 7.23 to 7.35 (p < 0.005), the median ICG plasma disappearance rate from 7.6 to 11.3%.min-1 (p < 0.02), and the median MEGX concentration from 4 to 10.2 ng.mL-1 (p < 0.005). Dopamine had no effect on any of the measured variables. There were no changes in the control group. Low-dose dopexamine increases splanchnic blood flow as measured by gastric intramucosal pH, MEGX formation from lidocaine, and ICG clearance. The lack of any change in the systemic measurements suggests that these effects are the result of a selective vasodilatation of the splanchnic vessels. At the dose used in this study, dopamine had no effect on splanchnic blood flow. Dopexamine may be useful in the management of splanchnic ischemia in the critically ill.

Improved P CO2 measurement in six standard blood gas analysers using a phosphate‐buffered solution for gastric tonometry

The measurement of gastric intramucosal pH serves as a non-invasive technique for early detection of gastrointestinal ischaemia in critically ill patients. The method is based on the determination of the partial pressure of carbon dioxide in a 0.9% saline solution using a standard blood gas analyser. However, the use of standard blood gas analysers leads to an underestimation of carbon dioxide partial pressure in saline. Instrumental biases of six blood gas analysers were investigated using either a saline or a phosphate-buffered solution. Both test solutions were equilibrated with five defined carbon dioxide concentrations. Each blood gas analyser underestimated this defined partial pressure of carbon dioxide with a bias between -3.7% and -57.5% if saline was used. The phosphate-buffered solution considerably improved instrumental precision, resulting in biases between +2.7% and -17.6% Thus, a phosphate-buffered solution increases the accuracy of gastric intramucosal pH measurement.

Measurement of gastric intramucosal pH as a metabolic marker during infrarenal abdominal aortic surgery

Measurement of gastric intramucosal pH as a metabolic marker during infrarenal abdominal aortic surgery

Comparison of clinical information gained from routine blood-gas analysis and from gastric tonometry for intramural pH

The measurement of gastric intramucosal pH (pH i) has been advocated to assist in decision-making for critically ill patients. To assess whether the information obtained from the measurement of pH i can be obtained from other measurements of metabolic acidosis, we studied 20 consecutive patients admitted to the intensive care unit. A mean of eight (range two to fourteen) data sets per patient were obtained, comprising measurement of arterial pH, pO 2, pCO 2, and oxygen saturation, tonometer balloon fluid pCO 2, arterial pressures, and cardiac output. Bicarbonate concentration, base deficit or excess in blood and extracellular fluid, and pH i were calculated from these measurements. Relations between the variables and pH i were assessed by within-subject correlation comparisons. There were significant correlations ( r>0·6, p<0·001) between markers of metabolic acidosis (base deficit in blood and extracellular fluid and bicarbonate concentration) and pH i. A blood base deficit of -4·65 or less and an extracellular-fluid base deficit of -6·13 or less could estimate pH i below 7·32 (lower limit of normal range) with sensitivity of at least 77% and specificity of at least 96%. There was no patient in whom either pH i or blood base deficit consistently reflected acidosis when the other variable did not. We conclude that the information that is obtained by gastric tonometry for pH i can be obtained more simply from measurements of metabolic acidosis; these variables can be calculated from routinely available blood-gas measurements.

Gastric tonometry and venous oximetry in cardiac surgery patients

To determine the relationship between gastric intramucosal pH and several other indices of splanchnic perfusion in patients undergoing cardiopulmonary bypass. Prospective, single-arm study. University Hospital. Elective cardiac surgery patients (n = 8), free of hepatic disease, were studied. Before anesthetic induction, a triple-lumen, heparin-bonded fiberoptic catheter was inserted into the hepatic vein under fluoroscopic guidance. An identical catheter was inserted into the pulmonary artery. After endotracheal intubation, a nasogastric tube modified to permit measurement of gastric intramucosal pH was inserted into the stomach. Systemic oxygen delivery (DO2), and arterial, mixed venous, hepatic venous, and femoral venous blood gases and lactate concentrations were recorded at the following times: immediately before induction of anesthesia (time 1); during atrial cannulation (time 2); after 30 mins of hypothermic cardiopulmonary bypass (time 3); 15 mins after termination of cardiopulmonary bypass (time 4); and 1 hr after arrival in the ICU (time 5). Hepatic venous hemoglobin saturation (SO2) and mixed venous hemoglobin saturation (SvO2) were monitored continuously from times 1 to 5. Gastric intramucosal pH was recorded at times 2, 3, 4, and 5. The hepatic catheter was removed as soon as the last samples were collected in the ICU. The square of the weighted mean correlation coefficients (rw)2 for gastric intramucosal pH vs. hepatic venous lactate concentrations, gastric intramucosal pH vs. hepatic venous PO2, and gastric intramucosal pH vs. hepatic venous pH were (rw)2 = .50, (rw)2 = .58, and (rw)2 = .32, respectively. Systemic DO2, hepatic venous lactate concentrations, hepatic venous PO2, and hepatic venous pH were significant determinants in the multiple regression model for gastric intramucosal pH (r2 = .89). There were significant differences between SvO2 and hepatic venous SO2 at times 4 and 5. Gastric intramucosal pH may provide a minimally invasive way to monitor the adequacy of splanchnic DO2 in patients undergoing cardiopulmonary bypass. Additional data are necessary to determine whether low gastric intramucosal pH is truly a marker of supply-dependent oxygen uptake across the hepatosplanchnic vascular bed under these conditions.

Gastric mucosal pH as a prognostic index of mortality in critically ill patients

To determine if measurements of gastric intramucosal pH have prognostic implications regarding ICU mortality. Prospective comparison of outcome. General adult ICUs in two teaching hospitals. Eighty consecutive patients age 18 to 84 yrs (mean 63.4), 50 men and 30 women, 55% in the medical and 45% in the surgical services. Gastric intramucosal pH was measured on ICU admission and again 12 hrs later. A value of greater than or equal to 7.35 was used to differentiate between normal and low gastric intramucosal pH. Fifty-four patients had a normal gastric intramucosal pH and 26 patients had a low gastric intramucosal pH on ICU admission. The mortality rate was greater in the low gastric intramucosal pH group (65.4% vs. 43.6%; p less than .04). The frequency of sepsis and the presence of multisystem organ failure also were greater in the low gastric intramucosal pH group (p less than .01). Further stratification of patients according to gastric intramucosal pH measured 12 hrs after admission showed a greater mortality rate in patients with persistently low gastric intramucosal pH when compared with patients with normal gastric intramucosal pH during the first 12 hrs (86.7% vs. 26.8%; p less than .001). Measurements of gastric intramucosal pH on ICU admission, and again 12 hrs later, have a high specificity for predicting patient survival in this ICU patient population (77.8% to 80.6%). Furthermore, given its relative noninvasive nature, tonometrically measured gastric intramucosal pH may be a useful addition to patient monitoring in the ICU.