Measurement Of Intramucosal pH Research Articles

Volumetric Hemodynamic Changes and Postoperative Complications in Hypothermic Liver Transplanted Patients

Introduction Hepatic diseases decrease the liver's involvement in thermoregulation. Removal of the liver during transplantation increases the incidence of hypothermia during the surgery. The aims of the present study were to analyze the hemodynamic changes among hypothermic liver transplantations and to determine its relationship to postoperative complications. Methods Conventional and volumetric hemodynamic monitoring and intramucosal pH measurements were performed during 54 liver transplantations. According to the core temperature until graft reperfusion, patients were classified into group A, hypothermic patients (temperature < 35°C; n = 25) versus group B, normothermic patients (temperature > 36°C; n = 29). We examined the relationships between central venous pressure (CVP), intrathoracic blood volume index, cardiac index (CI), and oxygen delivery index, oxygen consumption index, as well as the fluctuation of the mean arterial pressure (MAP) and gastric intramucosal pH and activated clotting time. We recorded prolonged ventilation time, vasopressor and hemodialysis requirements, occurrence of infections, and intensive care days. Results There were no significant differences in the MELD scores. More Child–Pugh class C patients ( P < .01) showed significantly higher APACHE II scores ( P < .02) among group A. During hepatectomy and at the same intrathoracic blood volumes, the hypothermic group showed significantly higher CVP levels ( P < .02). During the anhepatic and postreperfusion phases, the decreased CI levels ( P < .05) were associated with increased MAP values ( P < .05). Without differences in oxygen delivery, the oxygen consumption was lower in group A ( P < .05). The intramucosal pH levels were the same in the both groups during the whole examination period. More instances of infection, intensive care, and hemodialysis treatment days, were observed as well as significantly longer vasopressor requirements and coagulopathy among the hypothermic group ( P < .007).

Tonometer pHi Monitoring of Free Jejunal Grafts following Pharyngolaryngoesophagectomy for Hypopharyngeal or Cervical Esophageal Cancer

Background/Aims: Graft failure is a critical complication associated with vascular occlusion in esophageal reconstruction with a free jejunal graft following pharyngolaryngoesophagectomy. In this study, we evaluated the usefulness of intramucosal pH (pH_i) measurement using a tonometer to assess the graft viability. Methods: Two consecutive studies, the early phase study and the late phase study, were performed. Nineteen patients who underwent free jejunal transfer were enrolled in the early phase study before 1999 to determine the critical pH_i value. In the late phase study after 2000 (n = 16), anticoagulant treatment to prevent graft necrosis was performed in the patients having a pH_i value under the critical level. Results: In the early phase study, vascular obstruction was not seen in 16 patients with pH_i >7.10. Of 3 patients with pH_i <7.10, 2 underwent regrafting because of jejunal graft necrosis by vascular obstruction. In the late phase study, reoperation was not required in 3 of 4 patients with pH_i <7.10. Intraoperative vascular occlusion was found in 1 patient with a decline in pH_i value and anticoagulant treatment was effective in 2 others. Conclusion: The pH_i measurement using a tonometer is useful for finding vascular problems in free jejunal grafts.

Early Prediction of Anastomotic Leak in Colorectal Cancer Surgery by Intramucosal pH

Adequate oxygenation is necessary for anastomotic healing, and ischemia has been found to be one of the most important factors in anastomotic leakage. This study was designed to assess the value of early postoperative intramucosal pH measurements for the prediction of anastomotic leakage in patients with colorectal anastomosis. A prospective study of 90 patients with rectal or sigmoid cancer with primary anastomosis was conducted. In all patients intramucosal pH was determined by using tonometry at the anastomotic and gastric levels during the first 24 and 48 hours postoperatively. Seven other variables also were tested by univariate and multivariate analysis for any association with anastomotic leakage. The rate of clinical anastomotic leakage was 6.6 percent. Multivariate analysis showed that only the intramucosal pH at the anastomosis was an independent factor for the development of anastomotic leakage. The risk of leakage was 22 times higher in patients with an anastomotic intramucosal pH < 7.28 in the first 24 hours after surgery. Measurement of anastomotic intramucosal pH in the early postoperative period can more accurately predict the risk of anastomotic leakage and benefit those patients who would need additional measures to improve the viability of the anastomosis.

Effect of Intra-abdominal Pressure Level on Gastric Intramucosal pH During Pneumoperitoneum

The present study was designed to examine the effect of intra-abdominal pressure level on gastric intramucosal pH using gastric tonometry during pneumoperitoneum. One hundred patients were prospectively randomized into 5 equal groups (N = 20 each). Intra-abdominal pressure levels were 8, 10, 12, 14, and 16 mm Hg in groups I, II, III, IV, and V, respectively. Intramucosal pH measurement was done 2 times: 30 minutes following insufflation and 1 hour after the ending of the surgery. In the first and second measurements, intramucosal pH values were found as 7.39 +/- 0.02 and 7.36 +/- 0.03 in group I; 7.41 +/- 0.03 and 7.38 +/- 0.03 in group II; 7.37 +/- 0.03 and 7.37 +/- 0.03 in group III; 7.36 +/- 0.03 and 7.37 +/- 0.03 in group IV; and 7.39 +/- 0.03, 7.36 +/- 0.03 in group V, respectively. Statistical significance was not found in the comparison of these values within the groups and between the groups (P > 0.005, for each). In conclusion, intra-abdominal pressure between 8 and 16 mm Hg did not cause significant difference in gastric intramucosal pH.

Continuous gastric decompression on elimination of intragastric factor influence on gastric intramucosal pHi measurement after operations

目的 观察术后持续胃肠减压是否与口服雷尼替丁一样能消除胃内因素对胃粘膜pH(pHi)测定准确性的影响.方法 14例无胃肠疾病的住院手术患者,在术前首次测胃pHi前12 h、前2 h口服雷尼替丁各150 mg;术后持续经液体分压计(TRIP)鼻胃管胃肠减压,相隔24 h再次测胃pHi.结果首次pHi为7.35±0.03,再次pHi为7.36±0.05(P＞0.20).结论术后持续胃肠减压可消除胃内因素对胃pHi测定准确性的影响。

Accuracy of a point-of-care blood gas analyzer in gastric tonometry measurements of intramucosal pH (pHi) and P(CO2) gap.

We assessed the accuracy of a point-of-care blood gas analyzer in providing data from saline samples obtained by gastrointestinal tonometry (Tonometrics Catheter; Tonometrics Division, Instrumentarium, Helsinki, Finland) for the calculation of intramucosal pH (pHi) and the P(CO)(2) gap (intramucosal P(CO)(2) - Pa(CO)(2)). We compared the point-of-care analyzer (Opti; AVL Medical Instruments, Schaffhausen, Switzerland; "Opt") with a conventional analyzer (Compact 2 AVL Medical Instruments, Schaffhausen; "Elect") in a clinical study (Elect being taking as the standard). In an in vitro study, P(CO)(2) data of tonometer saline (Pr(CO)(2)) from Opt and Elect were compared with P(CO)(2) data from a continuous air tonometer (Tonocap Tonometrics Division, Instrumentarium) for a bottle containing a mixed P(CO)(2) gas. Data were evaluated by the Bland-Altman method. In the clinical study, the bias (B) and precision (P) were: B = 0.223 and P = 0.056 for pHi, B = -14.0 and P = 2.43 (mmHg) for Pr(CO)(2), and B = -16.7 and P = 2.6 (mmHg) for the P(CO)(2) gap ( n = 27). In the in vitro study, the bias between the two values (Pr(CO)(2) and bottle P(CO)(2)) was -1.98 mmHg and precision was 1.23 mmHg for Elect, but for Opt, these values were -22.09 mmHg and 3.15 mmHg, respectively ( n = 18). Opt is not suitable for measuring pHi and the P(CO)(2) gap because it does not provide an accurate P(CO)(2) for tonometry saline.

Intramucosal pH Measurements for Extremely Obese Patients During Laparoscopic Bariatric Surgery

To the Editor: Excessive obesity is defined as a body weight ≥225 % over the ideal weight or body mass index 50 kg · m2(1). As surgical treatment of obesity has developed, interest is renewed in the anesthetic management of these patients (2). Laparoscopic surgical techniques seem beneficial in obese patients (3). The gastric tonometry is a minimally invasive device by which the adequacy of splanchnic blood flow is assessed indirectly (4). We aimed to investigate intramucosal pH (pHi) measurements for excessively obese patients during laparoscopic bariatric surgery. Twelve obese patients with (ASA) class II-III who undergoing laparoscopic gastric banding were included in this study (Table 1). Table 1: The Patients’ Main Characteristics (Number or Mean ± sd)All patients received a low molecular weight heparin and ranitidine 12 h prior to the operation. All anesthetics and other medications were administered according to the corrected weight. Corrected weight was calculated using the following equation. Corrected weight =[0.4 × excess weight] + ideal weight (5). Anesthesia was induced with fentanyl 2 μg · kg−1 and propofol 1 mg · kg−1, a propofol infusion was administered at a rate of 6 mg · kg−1/h−1 until the end of the operation. Atracurium 0.6 mg · kg−1 was given to facilitate orotracheal intubation with a cuffed tube. Throughout the operation, fentanyl 2 μg · kg−1 and atracurium 0.1 mg · kg−1 were given as needed. Controlled ventilation was performed in all patients and ventilator was set to deliver 10 mL · kg−1 tidal volume, 10 min−1 frequency, I:E 1:2, inspiratory pause 20 % of inspiration and a constant inspiratory flow rate. Inspired oxygen content was 50% oxygen-air mixture and fresh gas flow rate was 8 L · min−1. Intra-abdominal pressure was held at 12 mm Hg during laparoscopy and a constant CO2 flow of 2 L · min−1 administered through a laparoscopic insufflator device. After anesthesia induction, arterial catheter was placed into radial artery. Direct arterial pressure measurements and blood gas sampling were performed via arterial catheter. The gastric tonometer (Trip TM, Tonometrics, Helsinki, Finland) was placed into stomach before the surgical incision and its position was verified with fluoroscopy. Mean arterial pressure, heart rate, and pHi values were measured in four periods: after 15 min of anesthesia induction (induction), after 20 min of pneumoperitoneum (pneumoperitoneum), after 10 min of desufflation (desufflation), and after 20 min of extubation (extubation). Atropine 0.01 mg/kg and neostigmine 0.02 mg/kg were administered to antagonize the neuromuscular blockade. At the end of the operation and following emergence from anesthesia, all patients were tracheally extubated and sent to postanesthetic care unit. There is no single anesthetic regimen shown to be superior in obese patients (Table 2). Obesity predisposes to cardiovascular morbidity. Hemodynamic variables could be affected from morbidly obese patients due to many factors (5). In our study, we determined slight changes in mean arterial pressure and heart rate that have no significant statistical result. Table 2: Intramucosal pH and Hemodynamic Values (Mean ± sd)Although there had been many studies evaluating different aspects of physiology during surgery and anesthesia in the obese patients (6–9), our study is the only one that utilized gastric tonometry. There is no clinical evidence or data that report that bariatric surgery operations or gastric band has an effect on stomach or splanchnic circulation. In long-term studies, the gastric band is well tolerated by these patients. Chronic erosion is a common complication due to the gastric band’s local effect, not from stomach nor splanchnic circulation disorder (10). pHi measurements can be used to assess perfusion, and we observed slight decreases in pHi in our patients. There may be many factors responsible for the decrease of splanchnic perfusion from cardiac depression caused by anesthesia to increased intra-abdominal pressure due to pneumoperitoneum. Our study was not designed to evaluate these factors. In conclusion, we found no statistical changes on pHi on the laparoscopic bariatric surgery for excessively obese patients. Ziya Salihoglu, MD Sener Demiroluk, MD Yalim Dikmen, MD Mustafa Taskin, MD

Scanning laser Doppler flowmetry and intraluminal recirculating gas tonometry in the assessment of gastric and jejunal perfusion during oesophageal resection.

The ability of the new techniques of scanning laser Doppler flowmetry and recirculating gas tonometry to measure changes in gastric serosal and mucosal blood flow respectively during oesophageal resection was assessed. Changes in regional and total gastric blood flow were assessed in 16 patients undergoing oesophagectomy at three stages of the procedure. Laser Doppler images were analysed and perfusion expressed as mean perfusion units. Tonometric measurements of gastric and jejunal intramucosal pH (pHi) were made synchronously. There were significant falls in gastric perfusion measured with scanning laser Doppler flowmetry in all subjects between each measurement. Mean perfusion of the stomach fell 41 per cent after mobilization. There was a gradient of reduced perfusion between the antrum (mean fall 25 per cent) and the area used for the anastomosis in the fundus (mean fall 55 per cent). Before mobilization mean gastric and jejunal pHi were 7.37 and 7.46 respectively. These fell to 7.18 and 7.37 respectively after mobilization and to 7.29 and 7.38 after anastomosis. These new techniques could be employed at operation, appear to overcome the limitations of single-point laser Doppler flowmetry and saline tonometry, and have measured significant changes in gastric perfusion. They may have widespread clinical application.

Assessment of splanchnic perfusion with gastric tonometry in the immediate postoperative period of cardiac surgery in children.

OBJECTIVE - A prospective, nonrandomized clinical study to assess splanchnic perfusion based on intramucosal pH in the postoperative period of cardiac surgery and to check the evolution of patients during hospitalization. METHODS - We studied 10 children, during the immediate postoperative period after elective cardiac surgery. Sequential intramucosal pH measurements were taken, without dobutamine (T0) and with 5mcg/kg/min (T1) and 10 (T2) mcg/kg/min. In the pediatric intensive care unit, intramucosal pH measurements were made on admission and 4, 8, 12, and 24 hours thereafter. RESULTS - The patients had an increase in intramucosal pH values with dobutamine 10mcg/kg/min [7.19+/- 0.09 (T0), 7.16+/-0.13(T1), and 7.32+/-0.16(T2)], (p=0.103). During the hospitalization period, the intramucosal pH values were the following: 7.20+/-0.13 (upon admission), 7.27+/-0.16 (after 4 hours), 7.26+/-0.07 (after 8 hours), 7.32+/-0.12 (after 12 hours), and 7.38+/-0.08 (after 24 hours), (p=0.045). No deaths occurred, and none of the patients developed multiple organ and systems dysfunction. CONCLUSION - An increase in and normalization of intramucosal pH was observed after dobutamine use. Measurement of intramucosal pH is a type of monitoring that is easy to perform and free of complications in children during the postoperative period of cardiac surgery.

Evaluation of Splanchnic Perfusion and Oxygenation during Positive End-Expiratory Pressure Ventilation in Relation to Subcutaneous Tissue Gases and pH

Evaluation of splanchnic perfusion and oxygenation was performed by measurements of serosal tissue oxygen tension (PserO₂) and intramucosal pH (pHi) in relation to subcutaneous oxygen tension (PscO₂), subcutaneous carbon dioxide tension (PscCO₂) and subcutaneous pH (pHsc) in pigs subjected to oleic acid-induced lung injury during ventilation with increasing levels of positive end-expiratory pressure (PEEP). Lung injury resulted in a general hypoxia and redistribution of perfusion away from the subcutaneous and splanchnic tissues, illustrated by a decrease in PaO₂ from 93 to 37 mm Hg (p < 0.01), PscO₂ from 45 to 17 mm Hg (p < 0.01), PserO₂ from 80 to 30 mm Hg (p < 0.01) and pHi from 6.84 to 6.74 (p < 0.05) and a decrease of porta flow from 0.77 to 0.57 l/min. Application of PEEP up to 10–15 cm H₂O resulted in an increase of portal vein oxygen tension (PportaO₂) from 21 to 34 mm Hg (p < 0.01), PscO₂ from 17 to 26 mm Hg (p < 0.05) and PserO₂ from 30 to 55 mm Hg (p < 0.05). At PEEP 20 cm H₂O PserO₂ decreased to 47 mm Hg (p < 0.05). Porta flow decreased continuously with increasing levels of PEEP. PserO₂ correlated with PportaO₂ (r = 0.7, p < 0.001). pHi correlated poorly with PportaO₂ (r = 0.2) and porta flow (r = 0.4). PscO₂ and PserO₂ correlated well (r = 0.8, p < 0.001). In summary, splanchnic perfusion and oxygenation was better reflected by serosal oxygen tension than pHi in the colon. Changes in serosal oxygenation of the colon paralleled changes in subcutaneous tissue oxygenation.

Gastric intramucosal pH and intraluminal PCO2 during weaning from mechanical ventilation.

To study the value of gastric intramucosal pH and gastric intraluminal PCO2 measurements to predict weaning outcome from mechanical ventilation. Prospective clinical study. Intensive care medicine department of a university hospital. Nineteen adult critically ill patients who were mechanically ventilated because of acute respiratory failure and were considered ready to be weaned. The patients were weaned with: synchronized intermittent mandatory ventilation plus positive end-expiratory pressure (SIMV+PEEP) or continuous positive airway pressure with pressure support ventilation (CPAP+PSV). A gastric tonometer was placed in all the patients. Tonometric, respiratory, and hemodynamic variables were measured during the weaning process. Hemodynamic variables, respiratory mechanics, pulmonary gas exchange, respiratory muscle force, spontaneous pattern of breathing, and the central control of breathing were recorded. Simultaneously, the intramucosal pH and gastric intraluminal PCO2 were measured. Eleven patients were successfully extubated and eight failed. The patients who failed showed higher values of mouth occlusion pressure, respiratory rate, and effective inspiratory impedance (mouth occlusion pressure/mean inspiratory flow). The intramucosal pH was initially 7.19 +/- 0.22 and decreased to 7.10 +/- 0.16 during the weaning process in patients who failed (p < .05). At the same time, the intramucosal pH showed a nonsignificant change from 7.36 +/- 0.07 to 7.32 +/- 0.07 in the patients who were successfully extubated. The intramucosal pH was statistically different when both groups were compared during the initial and the final evaluations (p < .05). For the initial evaluation, the sensitivity and specificity to predict weaning failure when the intramucosal pH was < or =7.30 were 0.88 (95% confidence interval [CI], 0.66-1) and 0.82 (95% CI, 0.59-1), respectively. The gastric intraluminal PCO2 was higher in patients who failed (p < .05). When gastric intraluminal PCO2 was . or =40 torr during the initial evaluation, weaning failure occurred with a sensitivity of 1 (95% CI, 0.31-1) and a specificity of 0.55 (95% CI, 0.26-0.84). Weaning failure was associated with gastric intramucosal acidosis. The intramucosal pH and gastric intraluminal PCO2 may be helpful to predict weaning outcome. Further controlled clinical trials in a larger group of patients are needed.

In Vivo Application of Intestinal pH Measurement Using 2,7‘‐Bis(carboxyethyl)‐5,6‐carboxyfluorescein (BCECF) Fluorescence Imaging

Measurement of gastrointestinal intramucosal pH (pHim) has been recognized as an important factor in the detection of hypoxia-induced dysfunctions. However, current pH measurement techniques are limited in terms of time and spatial resolutions. A major advance in accurate pH measurement was the development of the ratiometric fluorescent indicator dye, 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF). This study aimed to set up and validate a fluorescence imaging technique to measure in vivo the intramucosal pH (pHim) of the intestine. The intestine was inserted into an optical chamber placed under a microscope. Animals were injected intravenously with the pH-sensitive fluorescent dye BCECF. Fluorescence was visualized by illuminating the intestine alternately at 490 and 470 nm. The emitted fluorescence was directed to an intensified camera. The ratio of emitted fluorescence at excitation wavelengths of 490 and 470 nm was measured, corrected and converted to pHim by constructing a calibration curve. The pHim controls were performed with a pH microelectrode and were correlated with venous blood gas sampling. Results show that pHim is determined with an accuracy of +/- 0.07 pH units and a response time of 1 min. In conclusion pHim mapping of rat intestine can be obtained by fluorescence imaging using BCECF. This technology could be easily adapted for endoscopic pH measurements.

Near-infrared spectroscopy measurement of regional tissue oxyhemoglobin saturation during hemorrhagic shock.

Adequate resuscitation of patients from shock states depends on restoration of oxygen delivery (DO2) to tissues. Direct measurement of systemic DO2 during shock states requires invasive techniques such as pulmonary artery catheterization. These experiments were performed to examine the ability of near-infrared spectroscopy (NIRS), to measure regional tissue oxygenation in a large-animal model of hemorrhagic shock, and to compare these measures to global measures of oxygen delivery. Splenectomized female pigs (n = 11) were anesthetized, instrumented, and monitored. NIRS probes were placed on the leg, in the stomach via nasogastric tube, and on the liver during laparotomy. Hemorrhagic shock was induced by phlebotomy of 28% of blood volume. After 1 hour, resuscitation was with shed blood and crystalloid until cardiac output plateaued. Measurements of physiologic parameters, blood gases, lactate, intramucosal pH, and NIRS values for regional tissue hemoglobin oxygen saturation (StO2), and cytochrome a,a3 redox state were recorded at intervals throughout the experiment. Tissue oxygenation as measured by oxyhemoglobin saturation and cytochrome a,a3 redox (NIRS) correlated with measures of systemic DO2 throughout the experiment. The liver probe demonstrated blunted changes in tissue oxygenation suggesting relatively protected circulation. Intramucosal pH did not correlate well with DO2. Regional tissue oxygenation as measured by NIRS shows excellent correlation with global oxygen delivery. NIRS may allow estimation of systemic oxygen delivery using rapid non-invasive techniques.

Earlier prediction of anastomotic insufficiency after thoracic esophagectomy by intramucosal pH.

To assess the value of using intramucosal pH (pHi) measurements to evaluate the viability of the gastric tube after thoracic esophagectomy, and to determine whether these measurements may be used for early prediction of anastomotic insufficiency. Prospective, observational study. University hospital in Japan. Thirty-nine patients who had undergone thoracic esophagectomy as a treatment for esophageal cancer. The blood flow within the gastric tube was measured using a laser Doppler flowmeter during surgery. Periodic measurement of the pHi within the gastric tube (gastric pHi) began during surgery and continued until the second postoperative day. In 30 patients, the pHi within the rectum (rectal pHi) was measured simultaneously with the gastric pHi. The patients were divided into two groups: those patients who experienced anastomotic insufficiency constituted the leakage(+) group (n = 13); those patients who did not experience these complications were designated the leakage(-) group (n = 26). The gastric pHi values correlated significantly with simultaneous measurements of the blood flow at the anastomotic site (p < .01). The postoperative gastric pHi values increased gradually in the leakage(-) group but stopped increasing after surgery in the leakage(+) group. The rectal pHi values increased gradually after surgery in both groups. Furthermore, there was a significant difference between the two groups when their gastric pHi values were subtracted from their rectal pHi values from the morning of the first postoperative day until the morning of the second postoperative day (p < .05). The gastric pHi values well reflected the viability of the gastric tube, especially when combined with the rectal pHi values. By measuring pHi, we can more accurately predict the risk of anastomotic insufficiency earlier after surgery and therefore give those patients who need it additional care to improve the viability of the gastric tube.

Does splanchnic ischemia occur in isolated neurotrauma? A prospective observational study.

To characterize the incidence and severity of splanchnic ischemia, as defined by gastric tonometry, in patients with isolated severe head injury and to examine the relationship between cerebral hemodynamics and splanchnic ischemia. Prospective observational study. Neurosurgical intensive care unit in a tertiary referral center. Ten patients with severe neurotrauma. None. The mean arterial pressure, intracranial pressure, and gastric mucosal P(CO2) measurements were recorded at 15-min intervals. Intramucosal pH was calculated every 3 hrs. All patients received stress ulcer prophylaxis. Nine patients received noradrenaline infusions to maintain a target cerebral perfusion pressure of 70 mm Hg. The mean baseline gastric mucosal P(CO2) and intramucosal pH were 38+/-10 torr and 7.38+/-0.1 pH units, respectively. Nine patients manifested low intramucosal pH during the study period. Gastric mucosal P(CO2) values ranged from 36 to 132 torr. Intramucosal pH measurements ranged from 6.9 to 7.47. The mucosal gap ranged from -12 to +93 torr (mean +/- SD, 17+/-17 torr). The pH gap ranged from -0.1 to +0.54 pH units (mean +/- SD, 0.14+/-0.11 pH units). There was no statistically significant relationship between cerebral hemodynamics, the use of inotropes, and gastric mucosal P(CO2), or intramucosal pH. Splanchnic ischemia (intramucosal pH, <7.3) occurs commonly in isolated neurotrauma, with a statistically nonsignificant trend toward development of mucosal ischemia with decreased cerebral perfusion.

Measurement of Intramucosal pH in Very Low Birthweight (VLBW) Infants

Measurement of Intramucosal pH in Very Low Birthweight (VLBW) Infants

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.

Continuous intramucosal PCO2 measurement allows the early detection of intestinal malperfusion.

The intestinal metabolic and histologic changes that occur in the gastrointestinal tract with ischemia and that form the basis of intramucosal pH and PCO2 alterations have not been well established. Recent evidence suggests that apart from technical problems with gastric tonometry, some methodologic misconceptions in the interpretation of intramucosal pH and PCO2 exist. The present study was designed to demonstrate the effects of impaired mesenteric perfusion with specific consideration to the induced intramucosal PCO2 changes using a new technique, the continuous fiberoptic CO2 sensor, and a new concept of interpretation. Randomized, controlled intervention trial. University animal laboratory. Twelve anesthetized female pigs, weighing 67+/-6 kg. The pigs were assigned to control and stenosis groups. In the stenosis group, blood flow in the superior mesenteric artery was reduced by 70% from baseline for 180 mins, followed by 120 mins of reperfusion. Serum lactate concentration, pH, PCO2, PO2, and bicarbonate concentration (cHCO3-) were determined in arterial, superior mesenteric venous, portal venous, hepatic venous, and pulmonary arterial blood. In the lumen of the ileum, intramucosal PCO2 was continuously determined by a fiberoptic CO2 sensor. At the end of the experiment, the gut was examined for histologic changes. During mesenterial hypoperfusion, a sudden and significant increase in intramucosal PCO2 was observed. This increase was paralleled by increases in superior mesenteric venous PCO2 and portal venous PCO2 (p < .05) and a concomitant decrease in intramucosal pH, superior mesenteric venous pH, and portal venous pH. Arterial and mixed venous PCO2 and pH did not change. cHCO3- did not change in local or systemic blood samples. Compromised mesenteric blood flow causes significant metabolic and histologic changes. These local changes could not be detected by arterial or mixed venous lactate concentrations, pH, and PCO2 determinations. Under closed-system conditions, mesenteric CO2 accumulation causes an impairment of the CO2-HCO3- buffer, resulting in an unchanged cHCO3-. With impaired mesenteric perfusion, only intramucosal PCO2 alterations occur and an intramucosal pH calculation based on systemic cHCO3-changes is not necessarily correct. Therefore, the only parameter of importance is the intraluminal measurement of intramucosal PCO2 that can reflect isolated mesenteric changes. Thus, we recommended abolishing the terms "intramucosal pH measurement" and "gastric tonometry" and propose using the definition "intramucosal PCO2 measurement."

Detecting gastrointestinal hypoperfusion during cardiac tamponade in pigs: a role for nitric oxide tonometry?

To evaluate different techniques and regional approaches for detecting critical reductions in gastrointestinal (GI) perfusion. Laboratory, animal, controlled study. University animal research laboratory. Thirteen anesthetized, ventilated, juvenile domestic pigs. Dextran was infused into the pericardial sac to achieve cardiac tamponade that reduced cardiac output to 25% of baseline value. Hemodynamics were invasively monitored, and blood gases were sampled in the systemic and portal circulations. Tonometers were placed in the corpus of the stomach and in the jejunum, 50 cm aboral to the ligament of Treitz. We measured cardiac output, portal venous blood flow, mesenteric oxygen delivery and consumption, systemic and portal venous blood gases and acid-base balance, stomach and jejunal transepithelial potential difference, stomach and jejunal intramucosal pH, arterial plasma concentrations of asymmetric dimethylarginine, and jejunal, intraluminal nitric oxide. One hour of cardiac tamponade decreased mesenteric oxygen delivery and consumption in a linear fashion and resulted in mesenteric acidosis, as evidenced by decreases in pH, standard bicarbonate, oxygen saturation, and PO2 and increases in PCO2. The potential difference in the jejunum decreased earlier than in the stomach, whereas stomach intramucosal pH decreased before jejunal intramucosal pH. Intraluminal nitric oxide in the jejunum was markedly reduced soon after cardiac tamponade. This reduction was accompanied by an increase in arterial plasma concentrations of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine. Investigated variables were unchanged in control animals. Both intramucosal pH and potential difference measurements may be used to detect critical reduction in GI perfusion. Regional and temporal differences may reduce the accuracy of these methods. Jejunal tonometry can yield an early nitric oxide measurement that indicates mesenteric low-flow conditions. Jejunal tonometry also yields quantitative information about this modulator of hemodynamic and mucosal barrier function, information that is relevant to GI failure during shock.

Early detection of necrotizing enterocolitis by gastrointestinal tonometry

The diagnosis of necrotizing enterocolitis (NEC) in neonates has traditionally depended on a combination of clinical signs, biochemical parameters and radiological changes. The measurement of intramucosal pH by gastrointestinal tonometry provides a simple means of long‐term monitoring which may detect the development of NEC before conventional techniques. We present our experience of tonometry in two‘at risk’term neonates with Hypoplastic Left Heart Syndrome.