Gastric Intramucosal PCO2 Research Articles

Acid-base disarrangement and gastric intramucosal acidosis predict outcome from major trauma

This prospective non-interventional study intended to assess the prognostic value of gastric intramucosal acidosis in patients with severe trauma admitted to a medical/surgical ICU. Gastric tonometer catheters were introduced to measure air PCO2 level (Tonocap device) in forty consecutive critically ill trauma patients. Gastric intramucosal pH, air PCO2 gradient, lactate and acid-base parameters were measured at admission and at 6, 12 and 24 h thereafter. The median age, mean APACHE II and SOFA scores were higher in nonsurvivors than in survivors (p<0.05). There were significant differences in the PCO2 gradient between survivors and nonsurvivors at 12 and 24 hours (10+/-7 vs. 24+/-19 mmHg, 13+/-16 vs. 29+/-25 mmHg; p<0.05). Gastric intramucosal pH values were lower in nonsurvivors than in survivors, on admission and after 12 or 24 hours (p<0.05). Arterial pH and bicarbonate were lower, lactate concentration higher, and base excess more negative in nonsurvivors. Prediction of outcome (mortality and MODS) at 24 hours of ICU assessed by their ROC curves was similar (p=NS). At 24 hours, air PCO2 gradient > 18 mmHg carried a relative risk of 4.6 for death, slightly higher than a HCO3 <20 mEq/L (RR=4.29) or base excess of <-2 mmol/L (RR=3.65). Bicarbonate, base deficit, lactate, gastric intramucosal pH and PCO2 gradient discriminate survivors from nonsurvivors of major trauma. A critical air PCO2 gradient carried the greatest relative risk for death at 24 hours of ICU. Inadequate regional blood flow as detected by a critical PCO2 gradient seems to contribute to morbidity and mortality of severe trauma patients.

Effect of Age, Feeding, and Omeprazole Administration on Gastric Tonometry in Healthy Neonatal Foals

Gastric tonometry is commonly used in humans as an assessment of intestinal mucosal perfusion. Values in healthy foals are currently unknown. Age, enteral feeding, and omeprazole administration would significantly alter gastric tonometry measurements in neonatal foals. Nine clinically normal foals were used to assess the effect of age and feeding, and 8 similar foals were used to assess the effect of omeprazole. At 1, 7, and 14 days of age, gastric intramucosal PCO2 (PgCO2) and arterial blood gas samples were obtained at baseline, immediately after feeding milk, and 1 and 2 hours after fasting for calculation of the intramucosal-arterial PCO2 difference (DeltaCO2). To evaluate the effect of omeprazole, foals were evaluated twice as above, 2 hours after fasting, comparing administration of omeprazole to no drug. There was a significant effect of age and feeding on PgCO2 and DeltaCO2, whereas arterial PCO2 was not significantly affected by these factors. Postfeeding DeltaCO2 values were significantly lower than fasted values. Baseline and postfeeding DeltaCO2 increased with age. There was no significant effect of age on data collected after 1 or 2 hours of fasting. The 90% reference interval for DeltaCO2 data collected after fasting was 0-54 mmHg. Foals had a significantly higher mean gastric pH and significantly higher DeltaCO2 and PgCO2 following omeprazole relative to no treatment. Because of the high and variable DeltaCO2, which is exacerbated by omeprazole administration, the reference interval in foals is extremely wide.

Prone positioning, systemic hemodynamics, hepatic indocyanine green kinetics, and gastric intramucosal energy balance in patients with acute lung injury

To investigate the effects of prone positioning on systemic hemodynamics, intra-abdominal pressure (IAP), plasma disappearance rate of indocyanine green (PDR(ICG)), and gastric intramucosal to arterial PCO2 difference (Pi-aCO2). Prospective randomized study in the intensive care unit of a university hospital. 12 mechanically ventilated, hemodynamically stable patients with acute lung injury. Positioning supine and prone for 3 h in random order. Systemic hemodynamics were determined by transpulmonary double-indicator dilution technique using an integrating fiberoptic monitoring system. The same monitoring system was used to measure PDR(ICG). IAP was measured in the urinary bladder and gastric intramucosal PCO2 was evaluated by automated recirculation gas tonometry. IAP increased from 10 +/-3 in the supine to 13+/-4 mmHg in the prone position. Cardiac index increased from 3.8+/-0.9 (supine) to 4.2+/-0.6 l/m(2) per minute (prone), mean arterial pressure from 75+/-10 (supine) to 81+/-11 mmHg (prone), PaO2/FIO2 from 194+/-66 (supine) to 269+/-68 mmHg (prone), and oxygen delivery from 558+/-122 (supine) to 620+/-74 ml/m(2) per minute (prone). No other parameters, including PDR(ICG) and Pi-aCO2, differed between the two positions. Prone positioning in mechanically ventilated patients with acute lung injury, despite a small increase in IAP, does not negatively affect the hepatic capacity to eliminate ICG and gastric intramucosal energy balance when systemic blood flow and oxygenation are improved.

Gastric tonometry after subarachnoid hemorrhage.

To evaluate splanchnic tissue perfusion, assessed by gastric tonometry, in patients with subarachnoid hemorrhage (SAH) and to study the effect of treatment, either surgical or endovascular, and the severity of initial SAH on splanchnic tissue perfusion. Prospective observational substudy, part of a randomised controlled trial of early treatment of ruptured intracranial aneurysms. Intensive care unit (ICU) of a university hospital. A consecutive sample of 26 patients [13 surgical (7/6 Hunt & Hess Grade I-II/H & H Gr IV-V) and 13 endovascular (3/10 H & H Gr I-II/H & H Gr IV-V)] out of 56 SAH patients randomly assigned to either endovascular or surgical treatment during the substudy period between 1 May 1995 and 31 August 1996. All patients were treated within 72 h after SAH. After treatment of a ruptured aneurysm, hemodynamics and gastric intramucosal pCO2 were measured during the first 4 h and between 6 h and 12 h after aneurysm treatment. In the whole sample, neither the gastric intramucosal-arterial pCO2 difference (pCO2 gap) (1.5+/-1.9 kPa and 1.7+/-1.2 kPa, NS) nor gastric intramucosal pH (7.28+/-0.12 and 7.29+/-0.08, NS) changed during the study. There were no differences in pCO2 gap or gastric intramucosal pH between treatment groups or Hunt & Hess grade groups during the study period. Splanchnic tissue perfusion may be insufficient even though there is no systemic hemodynamic disturbance in patients after SAH. Neither the therapeutic treatment nor pre-treatment Hunt & Hess grade is associated with a specific pattern of pCO2 gap.

Sublingual Capnography: A Clinical Validation Study

ObjectiveTo compare sublingual Pco2 (Pslco2) measurements with gastric intramucosal Pco2 (Pimco2) as well as with the traditional indexes of tissue oxygenation in hemodynamically unstable ICU patients. DesignA prospective, validation study. SettingThe medical and coronary ICUs of a community teaching hospital. PatientsConsecutive patients with severe sepsis, septic shock, or cardiogenic shock requiring pulmonary artery catheterization for hemodynamic management. InterventionsDuring the first 24 h of ICU admission, the Pslco2, Pimco2, and blood lactate concentrations as well conventional hemodynamic and oxygenation parameters were recorded every 4 to 6 h. The Pslco2-Paco2 and Pimco2-Paco2 differences were used as indexes of tissue dysoxia. These variables were correlated with each other as well as with the traditional markers of tissue oxygenation. ResultsSeventy-six data sets were obtained on 22 patients. Fifteen patients had severe sepsis/septic shock, and 7 patients did not have sepsis. A patient with ischemic bowel who had a large Pimco2-Pslco2 difference (60.2 mm Hg) was excluded. The initial Pslco2 and Pimco2 measurements were 43.5 ± 10.4 mm Hg and 42.8 ± 10.9 mm Hg, respectively (correlation coefficient [r] of 0.86; p < 0.001). The mean Pslco2 and Pimco2 for the entire data set were 48.0 ± 13.4 mm Hg and 46.1 ± 12.3 mm Hg, respectively (r = 0.78; p < 0.001). Ten patients died. The initial Pslco2-Paco2 difference was 9.2 ± 5.0 mm Hg in the survivors and 17.8 ± 11.5 mm Hg in the nonsurvivors (p = 0.04). The initial Pimco2-Paco2 difference was 8.4 ± 4.8 mm Hg in the survivors and 16.1 ± 13.7 mm Hg in the nonsurvivors (p = 0.08, not significant). The initial Pslco2-Paco2 difference correlated with the initial mixed venous-arterial CO2 gradient (r = 0.66; p = 0.001), but correlated poorly with the initial blood lactate concentration (r = 0.38), mixed venous Po2 (r = 0.05), and systemic oxygen delivery (r = − 0.39). ConclusionIn this study, sublingual capnometry yielded measurements that correlated well with those of gastric tonometry. Pslco2 may serve as a technically simple and noninvasive clinical measurement of tissue dysoxia in critically ill and injured patients.

Effects of perfusion pressure on tissue perfusion in septic shock.

To measure the effects of increasing mean arterial pressure (MAP) on systemic oxygen metabolism and regional tissue perfusion in septic shock. Prospective study. Medical and surgical intensive care units of a tertiary care teaching hospital. Ten patients with the diagnosis of septic shock who required pressor agents to maintain a MAP > or = 60 mm Hg after fluid resuscitation to a pulmonary artery occlusion pressure (PAOP) > or = 12 mm Hg. Norepinephrine was titrated to MAPs of 65, 75, and 85 mm Hg in 10 patients with septic shock. At each level of MAP, hemodynamic parameters (heart rate, PAOP, cardiac index, left ventricular stroke work index, and systemic vascular resistance index), metabolic parameters (oxygen delivery, oxygen consumption, arterial lactate), and regional perfusion parameters (gastric mucosal Pco2, skin capillary blood flow and red blood cell velocity, urine output) were measured. Increasing the MAP from 65 to 85 mm Hg with norepinephrine resulted in increases in cardiac index from 4.7+/-0.5 L/min/m2 to 5.5+/-0.6 L/min/m2 (p < 0.03). Arterial lactate was 3.1+/-0.9 mEq/L at a MAP of 65 mm Hg and 3.0+/-0.9 mEq/L at 85 mm Hg (NS). The gradient between arterial P(CO2) and gastric intramucosal Pco2 was 13+/-3 mm Hg (1.7+/-0.4 kPa) at a MAP of 65 mm Hg and 16+/-3 at 85 mm Hg (2.1+/-0.4 kPa) (NS). Urine output at 65 mm Hg was 49+/-18 mL/hr and was 43+/-13 mL/hr at 85 mm Hg (NS). As the MAP was raised, there were no significant changes in skin capillary blood flow or red blood cell velocity. Increasing the MAP from 65 mm Hg to 85 mm Hg with norepinephrine does not significantly affect systemic oxygen metabolism, skin microcirculatory blood flow, urine output, or splanchnic perfusion.

Systemic hemodynamics, gastric intramucosal PCO2 changes, and outcome in critically ill burn patients.

To define the hemodynamic and gastric intramucosal PCO2 (PiCO2) changes during the first 48 hrs after burn trauma and to analyze their relationship with outcome. Prospective, observational study in a cohort of consecutively admitted critically ill burn patients. Intensive care burn unit in a university hospital. Forty-two patients with burns covering >20% of body surface area or inhalation injury. None. Patients were monitored with an oximetric pulmonary arterial catheter and a gastric tonometer to measure PiCO2. The difference between arterial and gastric mucosal PCO2 (P[i-a]CO2) was considered indicative of gastric mucosal hypoxia. Hemodynamic and PiCO2 measurements were performed during the first 48 hrs after admission. Patients suffered burns covering 36.1% +/- 14.3% (mean +/- SD) and 45.3% +/- 21.9% of body surface area (survivors and nonsurvivors, respectively). All patients were successfully resuscitated by conventional standards. Nonsurvivors (n = 16) died a median of 17 days after admission. In univariate analysis, the presence of shock during the resuscitation phase, age, mixed venous pH, P[i-a]CO2, right atrial pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac index, systemic and pulmonary vascular resistance, left ventricular stroke work index, mixed venous oxygen saturation, and systemic oxygen delivery, consumption, and extraction ratio, measured over the first 12 hrs after admission, were significantly (p < .05) different between survivors and nonsurvivors. These differences disappeared after 12 hrs after admission. Multivariate analysis identified age, percentage body surface area burned, and oxygen delivery index (6 hrs after admission) as factors independently associated with a poor outcome. P[i-a]CO2 (12 hrs after admission) was significantly greater in patients with than in those without inhalation injury (17 +/- 13 torr [2.26 +/- 1.73 kPa] vs. 6 +/- 10 torr [0.79 +/- 1.33 kPa]; p = .005). Patients with a P[i-a]CO2 difference (6 hrs after admission) > or =10 torr (1.33 kPa) had a mortality rate of 56% vs. 25% of those patients with <10 torr (p = .044). Our data indicate that there are hemodynamic and biochemical changes that occur early after burn trauma that are associated with prognosis after an apparently successful resuscitation. Particularly, a hemodynamic profile characterized by systemic acidosis, low systemic blood flow, and systemic and pulmonary vasoconstriction early after trauma is associated with a poor outcome. Additionally, intestinal mucosal acidosis occurs after burn trauma, is influenced by inhalation injury, and is a variable related to outcome.

Monitoring initial volume therapy after coronary bypass surgery by gastric tonometry

Gastric tonometry is a very sensitive, non-invasive method to detect hypovolemia in critical care patients. Several studies document the predictive value of tonometry for patients' outcome. Especially a widened arterial to gastric-intramucosal PCO2 difference (aiDCO2) warns of complications. This study demonstrates the use of tonometry as a monitoring device for actual aspects of volume status and tissue oxygenation in patients after cardiac surgery.

The Effects of Intraoperative Intravenous Clonidine on Gastric Intramucosal PCO2

To investigate the effects of clonidine given as an anesthetic adjunct on splanchnic perfusion, we determined intramucosal gastric PCO2 using gastric tonometry in 60 patients scheduled for large intestine surgery.After induction of anesthesia, patients were randomly assigned to four groups. Patients in Group 1 received an IV infusion of sufentanil (0.2 [micro sign]g [center dot] kg-1 [center dot] h-1); patients in Group 2 received an IV infusion of clonidine (4 [micro sign]g/kg in 20 min followed by 2 [micro sign]g [center dot] kg-1 [center dot] h-1); patients in Group 3 received an IV infusion of ketamine (0.5 mg/kg followed by 0.25 mg [center dot] kg-1 [center dot] h-1); patients in Group 4 received an epidural infusion of bupivacaine (7 mL of 0.5% followed by 5 mL/h of 0.25%). Gastric intramucosal PCO2 was assessed immediately before skin incision and every hour during surgery using a nasogastric tube. A last measurement was taken after skin closure. An arterial sample was collected simultaneously to measure arterial PCO (2). Oxygen consumption (VO2/min) was continuously recorded. Gastric intramucosal PCO2 significantly increased during surgery in all groups independent of the anesthetic technique considered (P < 0.01) and was not related to metabolic changes or blood pressure variations. This increase, however, remains in the physiologic range. In conclusion, our results demonstrate that clonidine given as an anesthetic adjutant at the dose used has no deleterious effect on splanchnic perfusion during colonic surgery. Implications: IV clonidine given as an anesthetic adjunct at a dose of 4 [micro sign]g/kg in 20 min, followed by 2 [micro sign]g [center dot] kg-1 [center dot] h-1, has no deleterious effect on splanchnic perfusion during colonic surgery. (Anesth Analg 1998;87:686-90)

Gastric intramucosal pH in the assessment of adequacy of resuscitation after trauma

Gastric tonometry allows detection of abnormalities of metabolism that cause an elevated pCO2, such as tissue dysoxia or shock states. This may allow greater sensitivity in detecting insufficient resuscitation from known shock states, such as hypovolemic shock, or earlier detection of occult shock states, such as sepsis. This approach has been validated in several patient populations including hypovolemic trauma patients. There remains a population, however, in which the gastric intramucosal pCO2 can not be normalized by increases in global oxygen delivery. This may be due to ischemia-reperfu-sion injury. We developed a resuscitation algorithm to limit both hypovolemia or dysoxia and reperfusion injury. We postulate that a more aggressive approach to limiting reperfusion injury will allow further advances in decreasing morbidity and mortality of the critically injured trauma patient.

Detection of Graft Nonfunction After Liver Transplantation by Assessment of Indocyanine Green Kinetics

Detection of Graft Nonfunction After Liver Transplantation by Assessment of Indocyanine Green Kinetics

Gastric intramucosal PCO 2 as a quantitative indicatorof the degree of acute hemorrhage

Gastric intramucosal PCO2 (PiCO2) is a marker of splanchnic dysoxia and hypoperfusion that is increasingly used in intensive care medicine. We assessed two methods, saline-balloon tonometry versus continuous capnometric recirculating gas tonometry (CRGT), for detecting changes in PiCO2 in animals subjected to various degrees of hemorrhage and examined whether changes in PiCO2 would correlate with the degree of hemorrhage as assessed by blood loss volume. Following a baseline equilibration period, 20 anesthetized dogs were subjected to bleeding of 0, 23, 35, 41, or 47 mL/kg. After 30 minutes, the shed blood was reinfused and the experiments continued for an additional 120 minutes. Aggregate baseline PiCO2 was 43 mm Hg by both methods. PiCO2 did not change significantly over time in the control animals by either method. PiCO2 by CRGT rose significantly in each of the other groups at the end of the hemorrhage period and after resuscitation. Similar trends were observed in PiCO2 measured by saline tonometry but were significant only with the most severe hemorrhage. Strong correlation was observed between the degree of hemorrhage and change in PiCO2 by both methods. PiCO2 serves as a quantitative indicator of the severity of hypovolemic perfusion failure associated with hemorrhage. Compared with standard saline tonometry, CRGT may be a more sensitive method of monitoring the severity of hemorrhage.

Relationship between systemic oxygen supply dependency and gastric intramucosal PCO2 during progressive hemorrhage.

As systemic oxygen delivery (DO2) is reduced, oxygen consumption (VO2) is maintained until a critical level is reached (DO2crit) below which VO2 becomes supply-dependent and anaerobic metabolism ensues. We examined the relationship between gastric intramucosal PCO2 (PiCO2) and the onset of systemic supply dependency. We also compared PiCO2 to mixed venous and portal venous blood PCO2 (PmvCO2 and PpvCO2) to assess their utility as premonitory indicators of supply dependency. Six dogs were subjected to stepwise hemorrhage to effect a progressive decrease in DO2. Inflection points for changes in VO2, PiCO2, PmvCO2, and PpvCO2 versus DO2 were determined. Mean DO2crit was 6.0 +/- 0.7 mL x kg(-1) x min(-1), whereas the DO2 at which inflection points occurred for PiCO2 and PpvCO2 were 13.2 +/- 1.4 and 11.2 +/- 1.5 mL x kg(-1) x min(-1), respectively (p < 0.05 for both). Continuous monitoring of PiCO2 using capnometric recirculating gas tonometry can serve as an early indicator of systemic hypoperfusion before the onset of systemic supply dependency.

Variation in synchronous tonometric measurement of gastric intra-mucosal PCO2, in the critically ill

Variation in synchronous tonometric measurement of gastric intra-mucosal PCO2, in the critically ill

Regional variation in gastric intramucosal pCO2 may confound tonometric measurement: an evaluation using two tonometers and continuously recirculating gas tonometry

Regional variation in gastric intramucosal pCO2 may confound tonometric measurement: an evaluation using two tonometers and continuously recirculating gas tonometry

The Influence of Ischemia-Reperfusion Injury on Plasma Malondialdehyde in Children Undergoing Cardiopulmonary Bypass

Toxic oxygen free radicals (OFRs) are produced after ischemia-reperfusion injury, which can be observed during cardiopulmonary bypass (CPB). In a pilot study conducted in a tertiary care pediatric intensive care unit, we sought to determine plasma malondialdehyde (MDA) levels, a marker of OFR production, in children undergoing CPB, and to relate the findings to gastric intramucosal pH and PCO2 (pHi, PiCO2) and serum lactate. Thirteen nonconsecutive children (age: 56 ± 58 months) were included in the study. After induction of general anesthesia and endotracheal intubation, a tonometer nasogastric tube was positioned in the stomach; gastric pHi and PiCO2, arterial PCO2 (PaCO2), MDA, and lactate were measured 1 hour later (time 0) and 1 to 48 hours after initiation of CPB (times 1, 4, 8, 12, 16, 20, 24, 32, 40, and 48). Data for each variable were compared with baseline values for statistical significance. Free MDA levels increased by more than 50% in 11 patients (85%) and a statistically significant difference was found between the highest and the baseline free MDA concentrations (p &lt; .0025). Low gastric pHi after the first 8 hours post-CPB was significantly associated with a late rise in MDA levels. A stepwise multivariate regression analysis showed that the highest PiCO2:PaCO2 ratio was correlated to the highest MDA level (p &lt; .0001). A low gastric pHi later than 8 hours after CPB or a high PiCO2: PaCO2 ratio, as observed in this study, may indicate secondary splanchnic hypoperfusion with increased OFR production.

Development and validation of a technique for continuous monitoring of gastric intramucosal pH.

A novel method for continuously monitoring gastric intramucosal PCO2 and pH was developed and tested. Gas was continuously circulated through a modified balloon-tipped catheter connected to an external closed system fitted with an infrared CO2 sensor to monitor PCO2. Performance of the capnometric recirculating gas tonometry (CRGT) system was tested in vitro using an equilibration chamber and in vivo in six anesthetized dogs. Serial PCO2 measurements were made using CRGT and compared with intermittent PCO2 values obtained by conventional tonometry catheters. In the animal experiments, gastric intramucosal PCO2 and pH were determined before and after inducing hypoxia by decreasing the Flo2 to 0.08. After initial placement, PCO2 determined by the CRGT reached a near plateau within 45 min, and at that time point values were comparable to those obtained by conventional intermittent tonometry. Significant increases in gastric intramucosal PCO2 were detectable by CRGT within 5 min of inducing systemic hypoxia, and there was a concomitant significant decrease in intramucosal pH. Continuous monitoring of gastric intramucosal PCO2 and pH is feasible, has potential advantages over conventional methods, and can provide significant trending information over intervals as short as 5 min.

Comparison of Gastric Intramucosal pH and Standard Perfusional Measurements in Pediatric Septic Shock

To examine the utility of gastric tonometry as an early indicator of morbidity and mortality in pediatric patients with septic shock. Prospective clinical study. Multidisciplinary pediatric ICU. Eight critically ill pediatric patients with septic shock and with pulmonary artery and gastric tonometry catheters in place. Standard perfusional data including cardiac index, oxygen content (arterial, mixed venous), oxygen delivery, oxygen consumption, urine output, capillary refill, and lactate value were measured every 4 h. Intramucosal pH (pHi) was calculated from simultaneous tonometric measurements of gastric intramucosal PCO2 (PiCO2). Mean pHi values were compared between survivors and nonsurvivors. Tonometric data were compared with standard perfusional data by regression analysis. Low pHi values (< 7.35) were temporally compared with occurrence screens for adverse clinical events, (cardiopulmonary arrest, acute hemorrhage, and significant hypotension or dysrhythmias). Sets (n = 108) of paired data were collected from 8 patients (age 7 to 168 months) representing 4 deaths. The mean pHi in nonsurvivors (7.32 +/- 0.18) was significantly lower than that in survivors (7.48 +/- 0.07). Both pHi and PiCO2 were correlated with urine output by regression analysis. The pHi, but not PiCO2 correlated with extraction ratio and lactate level. There were no other significant correlations noted. Analysis of the ability of pHi values to predict adverse clinical events revealed that pHi less than 7.35 accurately predicted 26 of 39 concurrent or subsequent adverse clinical events. However, 24 of 50 pHi values less than 7.35 showed no association with similar adverse events, either concurrent or subsequent. The pHi had a sensitivity of 67%, a specificity of 74%, a positive predictive value of 52%, and an efficiency of 72% in predicting these adverse events. Use of gastric tonometry in pediatric septic shock patients appears to distinguish survivors from nonsurvivors. However, in general, tonometric assessment of splanchnic perfusion correlates poorly with standard clinical, hemodynamic, oxygen transport, or metabolic measurements of perfusion. Low pHi measurements are not predictive of concurrent or subsequent adverse clinical events.