Gastric mucosal pH and oxygen delivery and oxygen consumption indices in the assessment of adequacy of resuscitation after trauma: a prospective, randomized study

Comparison of heart rate variability, hemodynamic, metabolic and inflammatory parameters in various phases of decompansatory hemorrhagic shock of normal and vagotomized conscious male rats

BACKGROUND

Heart rate variability (HRV) analysis has shown promise as a valuable complementary tool for clinical assessment in trauma cases. This study aims to evaluate the utility of HRV in monitoring different severities of hemorrhagic shock (HS) and its correlation with traditional hemodynamic and metabolic parameters.

METHODS

Male Sprague-Dawley rats were divided into different experimental groups, including those with and without vagotomy, and were exposed to different classes of decompensatory HS. To induce varying severities of HS, volume resuscitation was delayed by gradually returning 0%, 20%, or 50% of the shed blood volume at the end of the compensation phase, referred to as 0% DFR, 20% DFR, and 50% DFR class, respectively. Hemodynamic parameters were monitored, and HRV was calculated. Levels of TNF-α and IL-10 were determined in lung tissue at the end of the experiments. Correlations between HRV, hemodynamic parameters, inflammatory gene expression and arterial blood gas variables were evaluated.

RESULTS

HRV showed increased power of the low-frequency (LF) and respiratory sinus arrhythmia (RSA) in all groups during the hypotension phase of HS (Nadir 1). Subdiaphragmatic vagotomy blunted the increase in the LF component in the Nadir 1. After volume resuscitation, systolic blood pressure (SBP), RSA and LF returned to baseline in the 0% DFR and 20% DFR classes. However, animals in 50% DFR class exhibited a reduced SBP and LF and lower pH. Notably, strong correlations were found between LF and SBP as well as tissue hypoperfusion markers. The expression of TNF-α in the lung was increased in all HS groups, while this gene expression was significantly higher in the vagotomized animals.

CONCLUSION

The alterations in HRV components were found to be significantly correlated with the hemodynamic and metabolic status of the animals, while showing no association with inflammatory responses. Additionally, the intervention of subdiaphragmatic vagotomy significantly impacted both HRV components and inflammatory responses. Collectively, these findings suggest the potential of HRV components for the assessment of the presence and severity of HS.

Real-Time Measurements of Oral Mucosal Carbon Dioxide (POMCO2) Reveals an Inverse Correlation With Blood Pressure in a Porcine Model of Coagulopathic Junctional Hemorrhage

INTRODUCTION

Shock states that occur during, for example, profound hemorrhage can cause global tissue hypoperfusion leading to organ failure. There is an unmet need for a reliable marker of tissue perfusion during hemorrhage that can be followed longitudinally. Herein, we investigated whether longitudinal POMCO2 tracks changes in hemodynamics in a swine model of coagulopathic uncontrolled junctional hemorrhage.

MATERIALS AND METHODS

Female Yorkshire-crossbreed swine (n = 7, 68.1 ± 0.7 kg) were anesthetized and instrumented for continuous measurement of mean arterial pressure (MAP). Coagulopathy was induced by the exchange of 50 to 60% of blood volume with 6% Hetastarch over 30 minutes to target a hematocrit of <15%. A 4.5-mm arteriotomy was made in the right common femoral artery with 30 seconds of free bleeding. POMCO2 was continuously measured from baseline through hemodilution, hemorrhage, and a subsequent 3-h intensive care unit period. Rotational thromboelastometry and blood gases were measured.

RESULTS

POMCO2 and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, POMCO2 increased because of the uncontrolled hemorrhage by 11.3 ± 3.1 mmHg and was inversely correlated with the drop (17.9 ± 5.9 mmHg) in MAP (Y = -0.4122*X + 2.649, P = .02, r2 = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or POMCO2 (P = .37).

CONCLUSIONS

Despite the logical appeal of measuring noninvasive tissue CO2 measurement as a surrogate for gastrointestinal perfusion, prior studies have only reported snapshots of this readout. The present investigation shows real-time longitudinal measurement of POMCO2 to confirm that MAP inversely correlates to POMCO2 in the face of coagulopathy. The simplicity of measuring POMCO2 in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.

Endpoints of Resuscitation for the Victim of Trauma

Useful resuscitation endpoints must serve both to diagnose the need for and to ensure the ongoing adequacy of resuscitation. To this end, traditional measures of organ perfusion are now widely appreciated to be grossly inadequate. Useful endpoints or milestones range from the global, to the regional, to the cellular specific. Understanding the basic principles of perfusion-related dysoxia in trauma and hemorrhage and its potential rapid transition to involve inflammatory and immune responses on cellular oxygen utilization will aid the clinician in choosing and appropriately interpreting endpoint monitoring data. There also appears to be an optimal window of opportunity for monitoring to help mitigate the development of more complicated inflammatory states. This article reviews the underlying need for endpoint selection (both global and regional, biochemical and functional) and monitoring during resuscitation of the polytrauma patient. At this juncture it appears that early use of a blend of global markers such as lactate and base deficit coupled with an available sensitive regional monitor such as gastric tonometry may offer the best combination of current technology to guard against early perfusion-related dysoxia. Future techniques involving optical spectroscopy offer the exciting potential to assess oxygenation at the cellular level. This may aid in ultra-early detection and resolution of perfusion-related dysoxia in addition to recognizing its transition to more complex inflammatory-mediated circulatory and metabolic failure.

Effects of dopamine, norepinephrine and dobutamine on gastric mucosal pH of septic shock patients

The effect of different vasoactive drugs on the pH [intracellular pH (pHi)] of gastric mucosa in patients with septic shock was evaluated in the present study. According to the vasoactive drugs applied, 48 patients with septic shock were divided into 3 groups: A, B and C, with 16 cases each. Cases of group A were treated with dopamine, those of group B with norepinephrine while those of group C were treated with norepinephrine plus dobutamine. The changes of pH of gastric mucosa were observed before treatment (baseline) and 6, 12, 24 and 48 h after treatment, and the hemodynamic indicators were observed before treatment (baseline) and 6 h after administration. The gastric mucosal pH was not significantly different between two of the three groups before treatment (each at P>0.05). The gastric mucosal pH of group A did not change 6, 12, 24 and 48 h after treatment with drugs compared with the baseline (all at P>0.05), while the gastric mucosal pH in groups B and C were each statistically higher at the time points of 6, 12, 24 and 48 h after treatment with drugs compared with the respective baselines (all at P<0.05). Following treatment with drugs, the gastric mucosal pH of group C at all the time points of 6, 12, 24 and 48 h after treatment were significantly higher than those of groups A and B at the same time points after treatment, while there were some statistical differences between groups A and B at these time points (6, 12, 24 and 48 h after treatment; P<0.05). The hemodynamic indicators of the patients before treatment were not significantly different between two of the three groups (all at P>0.05). Compared with the baseline values, the mean arterial pressure and the cardiac index of each group after treatment were significantly increased, the pulmonary capillary wedge pressure and the central venous pressure of groups B and C significantly increased (all at P<0.05) and the heart rate of group A was significantly increased (P<0.05). In conclusion, the gastric mucosal pH of the septic shock patients was increased when treated with norepinephrine or with dobutamine. Additionally, the gastric mucosal pH was significantly higher when the patients were treated with dobutamine and norepinephrine in combination than with norepinephrine or dopamine alone. Dopamine, norepinephrine and dobutamine can improve the systemic hemodynamic conditions in patients with septic shock.

Comparison of fluid types for resuscitation in acute hemorrhagic shock and evaluation of gastric luminal and transcutaneous Pco2 in Leghorn chickens

The objective of this study was to compare the effects of 3 different fluid types for resuscitation after experimentally induced hemorrhagic shock in anesthetized chickens and to evaluate partial pressures of carbon dioxide measured in arterial blood (Paco2), with a transcutaneous monitor (TcPco2), with a gastric intraluminal monitor (GiPco2), and by end tidal measurements (Etco2) under stable conditions and after induced hemorrhagic shock. Hemorrhagic shock was induced in 40 white leghorn chickens by removing 50% of blood volume by phlebotomy under general anesthesia. Birds were divided into 4 groups: untreated (control group) and treated with intravenous hetastarch (haes group), with a hemoglobin-based oxygen carrier (hemospan group), or by autotransfusion (blood group). Respiratory rates, heart rates, and systolic arterial blood pressure (SAP) were compared at 8 time points (baseline [T0]; at the loss of 10% [T10%], 20% [T20%], 30% [T30%], 40% [T40%], and 50% [T50%] of blood volume; at the end of resuscitation [RES]; and at the end of anesthesia [END]). Packed cell volume (PCV) and blood hemoglobin content were compared at 6 time points (T0, T50%, RES, and 1, 3, and 7 days after induced hemorrhagic shock). Measurements of Paco2, TcPco2, GiPco2, and Etco2 were evaluated at 2 time points (T0 and T50%), and venous lactic acid concentrations were evaluated at 3 time points (T0, T50%, and END). No significant differences were found in mortality, respiratory rate, heart rate, PCV, or hemoglobin values among the 4 groups. Birds given fluid resuscitation had significantly higher SAPs after fluid administration than did birds in the control group. In all groups, PCV and hemoglobin concentrations began to rise by day 3 after phlebotomy, and baseline values were reached 7 days after blood removal. At T0, TcPco2 did not differ significantly from Paco2, but GiPco2 and Etco2 differed significantly from Paco2. After hemorrhagic shock, GiPco2 and TcPco2 differed significantly from Paco2. The TcPco2 or GiPco2 values did not differ significantly at any time point in birds that survived or died in any of the groups and across all groups. These results showed no difference in mortality in leghorn chickens treated with fluid resuscitation after hemorrhagic shock and that the PCV and hemoglobin concentrations increased by 3 days after acute hemorrhage with or without treatment. The different CO2 measurements document changes in CO2-values consistent with poor perfusion and may prove useful for serial evaluation of responses to shock and shock treatment.

Gastric Tonometry as a Prognostic Index of Mortality in Sepsis

BACKGROUND

Splanchnic hypoperfusion in sepsis leads to translocation of bacteria from gut and development of multi-organ dysfunction syndrome (MODS), with increased mortality in critically ill patients. Gastric tonometry can detect this hypoperfusion by measuring carbon dioxide tension (PgCO2) and intramucosal pH (pHi) from gastric mucosa. Therapeutic intervention aimed at improving gut perfusion can improve the outcome and prognosticate the mortality in sepsis patients.

METHODS

100 patients with clinical diagnosis of sepsis were included and divided into two groups of 50 each. Group A patients were managed traditionally without gastric tonometry and in Group B gastric tonometry was used for therapeutic intervention. The intramucosal PCO2, pHi, end tidal carbon dioxide tension (EtCO2) and (PgCO2-EtCO2) differences were monitored at 0, 12 and 24 hours interval.

RESULT

Overall mortality in Group A was 64 % and 54 % in Group B. In Group B 45% patients developed MODS and 54 % died with low pHi. As an index of mortality low pHi had a sensitivity of 70% and specificity of 65%.

CONCLUSION

There is a good correlation between mortality prediction on the basis of pHi and PgCO2-EtCO2 difference and actual mortality in critically ill patients. The gastric tonometer should be used to predict mortality and guide resuscitation in septicemia.

Monitoring global volume-related hemodynamic or regional variables after initial resuscitation: What is a better predictor of outcome in critically ill septic patients?

OBJECTIVE

Regional variables of organ dysfunction are thought to be better monitoring variables than global pressure-related hemodynamic variables. Whether a difference exists between regional and global volume-related variables in critically ill patients after resuscitation is unknown.

DESIGN

Prospective diagnostic test evaluation.

SETTING

University-affiliated mixed intensive care unit.

PATIENTS

Twenty-eight critically ill patients.

INTERVENTIONS

Using standardized resuscitation, hemodynamic optimization was targeted at mean arterial pressure, heart rate, occlusion pressure, cardiac output, systemic vascular resistance, and urine output. Primary outcome variable was in-hospital mortality.

MEASUREMENTS AND MAIN RESULTS

During resuscitation, global volume-related hemodynamic variables were measured simultaneously and compared with regional variables. At admission no variable was superior as a predictor of outcome. During resuscitation, significant changes were seen in mean arterial pressure, central venous pressure, oxygen delivery, systemic vascular resistance, total blood volume, right heart and ventricle end-diastolic volume, right ventricle ejection fraction, right and left stroke work index, intramucosal carbon dioxide pressure, gastric mucosal pH, mucosal-end tidal Pco2 gap, indocyanine green blood clearance, indocyanine green plasma clearance, and plasma disappearance rate. Multivariate analysis identified lactate, gastric mucosal pH, mucosal-end tidal Pco2 gap, mucosal-arterial Pco2 gap, indocyanine green plasma clearance, and plasma disappearance rate of dye as nondependent predictors of outcome. Patients who subsequently died had a significantly lower gastric mucosal pH, higher intramucosal carbon dioxide pressure and mucosal-end tidal Pco2 gap, and lower indocyanine green blood clearance, indocyanine green plasma clearance, plasma disappearance rate, and right ventricular end-diastolic volume index, of which gastric mucosal pH, mucosal-end tidal Pco2 gap, and indocyanine green blood clearance were the most important predictors of outcome.

CONCLUSIONS

Initial resuscitation of critically ill patients with shock does not require monitoring of regional variables. After stabilization, however, regional variables are the best predictors of outcome.

Epidemiology of multiple organ dysfunction syndrome in critical surgical illness

Multiple organ dysfunction syndrome (MODS) is a major cause of morbidity and mortality in surgical intensive care units (SICUs). Multiple organ dysfunction syndrome remains the most important factor associated with mortality in the SICU. Illness severity scores such as the Acute Physiology and Chronic Health Evaluation-III (APACHE III) and the magnitude of the systemic inflammatory response syndrome (SIRS) at the time of SICU admission are useful in stratifying patients at risk for MODS and subsequent mortality. Assessment of key organ systems shows that mortality correlates with the overall severity of organ dysfunction and the number of involved organ systems, as well as to individual organs that fail. Despite the prognostic utility of SIRS/MODS, definitions of dysfunction of individual organs have shortcomings. The problem with quantitating MODS lies in the inability to adequately define organ dysfunction, especially of the gastrointestinal tract, liver, and central nervous system. Biological indicators of organ dysfunction may prove to be better markers for MODS in the future.

Use of Near-Infrared Spectroscopy in Early Determination of Irreversible Hemorrhagic Shock

BACKGROUND

In field situations, patient triage may require early determination of patients progressing to irreversible shock. We investigated the utility of near-infrared spectroscopy (NIRS) in early detection of irreversible hemorrhagic shock.

METHODS

Twenty instrumented pigs were treated with a protocol involving 35% blood volume hemorrhage, 90 minutes of shock, and stepwise resuscitation with lactated Ringer's. Hemodynamics and NIRS measurements of skeletal muscle (leg), stomach, and liver tissue oxyhemoglobin saturation (StO2) were measured at baseline, every 30 minutes during shock, and after each resuscitative step. Measurements were compared between animals that expired during resuscitation (unresuscitatable) and animals that survived all resuscitative steps (resuscitatable).

RESULTS

Neither global oxygen delivery, oxygen consumption, nor lactate distinguished resuscitatable from unresuscitatable animals. Invasive measurements of SvO2 did distinguish resuscitatable from unresuscitatable animals. After the first fluid bolus, both stomach and leg StO2 differed significantly between resuscitatable and unresuscitatable animals. Regression analysis revealed skeletal muscle (leg) StO2 obtained after the first resuscitative step was a significant mortality predictor despite resuscitation (r2=0.45) (p = 0.005).

CONCLUSIONS

Non-invasive NIRS monitoring of leg and stomach StO2 differentiates resuscitatable from unresuscitatable animals after the initial resuscitative bolus. Use of this non-invasive tool may guide appropriate use of resuscitative fluids and has possible point-of-care applications.

Bench-to-bedside review: oxygen debt and its metabolic correlates as quantifiers of the severity of hemorrhagic and post-traumatic shock

Evidence is increasing that oxygen debt and its metabolic correlates are important quantifiers of the severity of hemorrhagic and post-traumatic shock and and may serve as useful guides in the treatment of these conditions. The aim of this review is to demonstrate the similarity between experimental oxygen debt in animals and human hemorrhage/post-traumatic conditions, and to examine metabolic oxygen debt correlates, namely base deficit and lactate, as indices of shock severity and adequacy of volume resuscitation. Relevant studies in the medical literature were identified using Medline and Cochrane Library searches. Findings in both experimental animals (dog/pig) and humans suggest that oxygen debt or its metabolic correlates may be more useful quantifiers of hemorrhagic shock than estimates of blood loss, volume replacement, blood pressure, or heart rate. This is evidenced by the oxygen debt/probability of death curves for the animals, and by the consistency of lethal dose (LD)_25,50 points for base deficit across all three species. Quantifying human post-traumatic shock based on base deficit and adjusting for Glasgow Coma Scale score, prothrombin time, Injury Severity Score and age is demonstrated to be superior to anatomic injury severity alone or in combination with Trauma and Injury Severity Score. The data examined in this review indicate that estimates of oxygen debt and its metabolic correlates should be included in studies of experimental shock and in the management of patients suffering from hemorrhagic shock.

A Comparative Evaluation of Inhaled Halothane, Isoflurane, and Sevoflurane During Acute Normovolemic Hemodilution in Dogs

The hemodynamic response to acute normovolemic hemodilution (ANH) can be affected by the anesthetics used. We randomized 18 mongrel dogs to undergo ANH with 3 different inhaled anesthetics: halothane, isoflurane, or sevoflurane. Hemodynamics, oxygen transport, and gastric pH were measured before blood withdrawal, at the end of hemodilution, and 30 and 60 min after the end of hemodilution. The baseline measurements of all hemodynamic variables were similar among groups, with the exception of heart rate, which was more rapid in the sevoflurane group. Thirty minutes after hemodilution, the cardiac index increased 88%, 86%, and 157% in the halothane, isoflurane, and sevoflurane groups, respectively, whereas arterial-venous oxygen differences and oxygen consumption were larger in the halothane group compared with the isoflurane and sevoflurane groups. Gastric pH obtained by tonometry did not change and was not different among groups. Because the hemodynamic response to ANH was not blunted, all three anesthetics may be safely used for the maintenance of anesthesia.

New strategies to improve outcomes in the surgical intensive care unit

BACKGROUND

Over the last half-decade, substantial breakthroughs have taken place in terms of routine therapy of critically ill patients. The combination of these strategies has the potential to result in improvement in the overall outcomes for patients in intensive care units.

METHODS

A focused review was undertaken of trials of interventions in critically ill patients with outcome endpoints.

RESULTS

This review discusses recent results related to transfusion avoidance, new drug therapy of sepsis, low tidal volume ventilation, tight glycemic control, early goal-directed resuscitation in sepsis, and the contribution of intensivists to improved outcomes.

CONCLUSIONS

Appropriate incorporation of these strategies into everyday practice will likely result in improvements in the care of critically ill surgical patients.

Bladder Mucosa pH and Pco2 as a Minimally Invasive Monitor of Hemorrhagic Shock and Resuscitation

BACKGROUND

Continuous monitoring of pH, Pco2, and Po2 using fiberoptic sensor technology has been proposed recently as a clinical monitor of the severity of shock and impaired tissue perfusion. Surrogates of gut tissue perfusion such as gastric tonometry, although cumbersome, have been used to indirectly quantify the degree of gut ischemia. The purpose of this study was to demonstrate the feasibility of monitoring bladder mucosa (BM) and to compare urinary bladder mucosa and proximal jejunum mucosa interstitial pH and Pco2 during hemorrhagic shock and resuscitation.

METHODS

Eleven male miniature swine (25-35 kg) (control, n = 4; shock, n = 7) underwent jejunal tonometry and cystostomy. A multisensor probe was placed adjacent to the BM. Urine was diverted. Normocarbia was maintained. Animals were hemorrhaged and kept at a mean arterial pressure of 40 mm Hg. When a constant infusion was required to maintain the mean arterial pressure at 40 mm Hg (decompensation), animals were resuscitated with shed blood plus two times the shed volume in lactated Ringer's solution (20 minutes) and observed for 2 hours.

RESULTS

During decompensation, BM pH values decreased significantly from 7.33 +/- 0.08 to 7.01 +/- 0.2 (p < 0.01) and recovered to 7.11 +/- 0.19 at 120 minutes after completion of resuscitation. During decompensation, BM Pco2 values increased significantly compared with baseline (from 49 +/- 6 mm Hg to 71 +/- 19 mm Hg, p < 0.05) and returned to baseline with resuscitation. Jejunum mucosa and BM interstitial Pco2 correlated throughout shock and resuscitation (r = 0.49). Bland-Altman analysis demonstrated significant differences between jejunum mucosa (intramucosal pH) and BM interstitial pH.

CONCLUSION

Shock-induced changes in the Pco2 of the BM are comparable to tonometric changes in the gut. These data suggest that continuous fiberoptic multisensor probe monitoring of the BM could potentially provide a minimally invasive method for the assessment of impaired tissue perfusion of the splanchnic circulation during shock and resuscitation.

Tissue capnometry: does the answer lie under the tongue?

Increases in tissue partial pressure of carbon dioxide (PCO(2)) can reflect an abnormal oxygen supply to the cells, so that monitoring tissue PCO(2) may help identify circulatory abnormalities and guide their correction. Gastric tonometry aims at monitoring regional PCO(2) in the stomach, an easily accessible organ that becomes ischemic quite early when the circulatory status is jeopardized. Despite substantial initial enthusiasm, this technique has never been widely implemented due to various technical problems and artifacts during measurement. Experimental studies have suggested that sublingual PCO(2 )(P(sl)CO(2)) is a reliable marker of tissue perfusion. Clinical studies have demonstrated that high P(sl)CO(2) values and, especially, high gradients between P(sl)CO(2) and arterial PCO(2) (DeltaP(sl-a)CO(2)) are associated with impaired microcirculatory blood flow and a worse prognosis in critically ill patients. Although some questions remain to be answered about sublingual capnometry and its utility, this technique could offer new hope for tissue PCO(2) monitoring in clinical practice.

Phosphomonoesters Predict Early Mortality in Porcine Hemorrhagic Shock

BACKGROUND

Hemodynamic, laboratory, and tissue energetics were measured in a porcine model of hemorrhagic shock to evaluate variables as predictors of early mortality from shock. We hypothesized that elevated phosphomonoesters would predict early mortality in hemorrhagic shock.

METHODS

Pigs (n = 36) were subjected to 35% hemorrhage for 90 minutes in a 1.5-T nuclear magnetic resonance (NMR) magnet. Measurements included base deficit (BD); lactate; oxygen consumption/delivery; near-infrared spectroscopy of liver, stomach, and skeletal muscle tissue oxyhemoglobin saturation; and NMR spectroscopic measurements of high-energy phosphates of liver and skeletal muscle. Variables were compared between nonsurvivors and survivors to resuscitation after 90-minute measurements.

RESULTS

Ninety-minute mortality was 25%. Muscle phosphomonoesters (PMEs) and oxygen consumption differed significantly between survivors and nonsurvivors at baseline. Regression analysis identified baseline muscle PME levels, baseline BD, and 30-minute BD as early predictors of mortality before resuscitation (r2 = 0.304).

CONCLUSION

Baseline elevation in muscle PME levels predicts mortality in an animal model of severe hemorrhagic shock.

The esophageal Doppler monitor in mechanically ventilated surgical patients: does it work?

BACKGROUND

Assessment of cardiac volumes and cardiac output (CO) using a pulmonary artery catheter (PAC) in mechanically ventilated patients can be inconsistent and difficult. The esophageal Doppler monitor (EDM) is emerging as a potential alternative to the PAC. This prospective study evaluated the comparative accuracy between the PAC and EDM for preload assessment and CO in mechanically ventilated surgical patients. METHODS The EDM was placed in 15 patients with PACs in place. A total of 187 simultaneously measured EDM and PAC comparative data sets were obtained. The Pearson correlation (r) was used to compare measurements, with significance defined as a value of p < 0.05.

RESULTS

CO measured by EDM and PAC correlated closely (r = 0.97, p < 0.0001). Corrected flow time (FTc), a measure of left ventricular filling, correlated with PAC CO to the same degree as pulmonary capillary wedge pressure (PCWP) when positive end-expiratory pressure (PEEP) was < 10 cm H2O (FTc, r = 0.51; PCWP, r = 0.56). When PEEP was > or = 10 cm H2O, FTc correlated with PAC CO better than PCWP (FTc, r = 0.85; PCWP, r = 0.29).

CONCLUSION

FTc correlates with EDM and PAC CO better than PCWP. On the basis of the current study, it is reasonable to conclude that the EDM is a valuable adjunct technology for CO and preload assessment in surgical patients on mechanical ventilation, regardless of the level of mechanical ventilatory support.

Respiratory Rate as a Prehospital Triage Tool in Rural Trauma

BACKGROUND

Where trauma systems do not exist, such as in low-income countries, the aim of prehospital triage is identification of trauma victims with high priority for forward resuscitation. The present pilot study explored the accuracy of simple prehospital triage tools in the hands of nongraduate trauma care providers in the minefields of North Iraq and Cambodia.

METHODS

Prehospital prediction of trauma death and major trauma victims (Injury Severity Score > 15) was studied in 737 adult patients with penetrating injuries and long evacuation times (mean, 6.1 hours).

RESULTS

Both the respiratory rate and the full Physiologic Severity Score predicted trauma death with high accuracy (area under the curve for receiver-operating characteristic plots at 0.9) and significantly better than other physiologic indicators. The accuracy in major trauma victim identification was moderate for all physiologic indicators (area under the receiver-operating characteristic curve, 0.7-0.8).

CONCLUSION

Respiratory rate > 25 breaths/min may be a useful triage tool for nongraduate trauma care providers where the scene is chaotic and evacuations long. Further studies on larger cohorts are necessary to validate the results.

Gastric mucosal acidosis and cytokine release in patients with septic shock

OBJECTIVE

It has been postulated that in critically ill patients, splanchnic hypoperfusion may lead to cytokine release into the systemic circulation. The presence of cytokines could trigger an inflammatory response and cause multiple organ dysfunction syndrome. Although experimental studies support this hypothesis, humans studies remain controversial. The aim of the study was to determine the relationship between splanchnic hypoperfusion and cytokine release during septic shock.

DESIGN

Human prospective study.

SETTING

Medical intensive care unit at a university hospital.

PATIENTS

A total of 30 patients with mean arterial pressure of <60 mm Hg after volume loading with either oliguria or hyperlactatemia.

MEASUREMENTS

Gastric intramucosal measurements as an indicator of splanchnic hypoperfusion and blood samples were obtained at admission to the medical intensive care unit and repeated during 48 hrs. Cytokine (tumor necrosis factor-alpha and interleukin-6) values were evaluated by enzyme-linked immunoassays at the following periods: at the time of admission and 2, 4, 8, 12, 24, 36, and 48 hrs later.

MAIN RESULTS

High levels of interleukin-6 and tumor necrosis factor-alpha were observed at admission in survivors and nonsurvivors, without significant difference. At 48 hrs, cytokine levels were significantly higher in patients who died compared with the survivors (tumor necrosis factor: 163 +/- 16 for nonsurvivors vs. 34 +/- 9 ng/mL for survivors; interleukin-6: 2814 +/- 485 for nonsurvivors vs. 469 +/- 107 ng/mL for survivors). At 48 hrs, the PCO2 gap was significantly higher in the nonsurvivors compared with survivors (25.87 +/- 2.73 vs. 11.35 +/- 2.25 mm Hg), despite systemic hemodynamic variables in the normal range. A positive relationship was demonstrated between plasma levels of tumor necrosis factor-alpha and interleukin-6 and the PCO2 gap throughout the study. The PCO2 gap was not correlated with hemodynamic variables.

CONCLUSIONS

Our data suggest a relationship between gastric mucosal acidosis, as assessed by PCO2 gap, and cytokine levels in critically ill patients with septic shock. Gut injury may be a contributor of the inflammatory response in patients with septic shock.

Pediatric trauma: beyond the brain

In pediatric trauma care, many long-held tenets of management have been revised. This article reviews the latest advances in pediatric trauma care, particularly in the areas of resuscitation and management of thoracic and abdominal injuries. The final topic is a discussion of what the intensivist and surgeon must know when caring for the pediatric victim of terrorist attacks.

Regional carbon dioxide monitoring: a different look at tissue perfusion

Adequate tissue oxygenation is one of the main therapeutic goals for the critically ill patient. Until recently, the perfusion status of the critically ill and injured has been assessed by global indices such as blood pressure, heart rate, and urine output. However, these global parameters are inadequate in that they fail to demonstrate the actual perfusion status of a patient. Research has shown the splanchnic region to be a pivotal organ bed in response to shock. Because this region shows early signs of hypoperfusion and hypoxia, its monitoring provides for more effective and complete resuscitation. To that end, gastric tonometry offers a noninvasive means by which early symptoms of low flow can be determined, allowing for optimization of tissue perfusion and patient outcome. The most proximal segment of the gastrointestinal tract offers promising information regarding tissue perfusion with the use of sublingual capnography.

Gastric tonometry: the role of mucosal pH measurement in the management of trauma

Effective management of hemorrhagic shock depends on titration of therapies against reliable resuscitation end points. Conventional clinical and laboratory indexes of shock are often slow to respond to progressive circulatory compromise. GI mucosal ischemia resulting from redistribution of blood flow may, however, precede uncompensated shock and may compound the initial hemorrhagic insult by touching off cascades of inflammatory responses. Trauma patients with evidence of subclinical GI ischemia have been shown to have poor outcomes. Gastric tonometry, by detecting the presence of gastric intramucosal acidosis as a proxy of splanchnic hypoperfusion, may facilitate more timely and rational shock resuscitation. This article reviews the development and validation of gastric tonometry and summarizes the clinical studies that have used this modality to guide the management of shock in trauma patients.

Sublingual capnometry: an alternative to gastric tonometry for the management of shock resuscitation

Normal vital signs do not reflect the physiologic aberrations after blood loss. Recognition of hypoperfusion during resuscitation can avoid the development of multiple organ failure. Advances in technology enable the clinician to monitor changes, potentially identifying tissue hypoxia much earlier than previously was possible. Gastric tonometry can be quite helpful in the intensive care unit in identifying gastric hypoperfusion, but has considerable drawbacks. The ability to monitor P(SI)CO(2) via sublingual capnometers overcomes some limitations of gastric tonometry and may be a valuable aid in the prehospital phase, the emergency department, and the intensive care unit in identifying end points of resuscitation.

Tissue oxygen monitoring during hemorrhagic shock and resuscitation: a comparison of lactated Ringer's solution, hypertonic saline dextran, and HBOC-201

BACKGROUND

The ideal resuscitation fluid for the trauma patient would be readily available to prehospital personnel, universally compatible, effective when given in small volumes, and capable of reversing tissue hypoxia in critical organ beds. Recently developed hemoglobin-based oxygen-carrying solutions possess many of these properties, but their ability to restore tissue oxygen after hemorrhagic shock has not been established. We postulated that a small-volume resuscitation with HBOC-201 (Biopure) would be more effective than either lactated Ringer's (LR) solution or hypertonic saline dextran (HSD) in restoring baseline tissue oxygen tension levels in selected tissue beds after hemorrhagic shock. We further hypothesized that changes in tissue oxygen tension measurements in the deltoid muscle would reflect the changes seen in the liver and could thus be used as a monitor of splanchnic resuscitation.

METHODS

This study was a prospective, blinded, randomized resuscitation protocol using anesthetized swine (n = 30), and was modeled to approximate an urban prehospital clinical time course. After instrumentation and splenectomy, polarographic tissue oxygen probes were placed into the liver (liver PO2) and deltoid muscle (muscle PO2) for continuous tissue oxygen monitoring. Swine were hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg over 20 minutes, shock was maintained for another 20 minutes, and then 100% oxygen was administered. Animals were then randomized to receive one of three solutions: LR (12 mL/kg), HSD (4 mL/kg), or HBOC-201 (6 mL/kg). Physiologic variables were monitored continuously during all phases of the experiment and for 2 hours postresuscitation.

RESULTS

At a MAP of 40 mm Hg, tissue PO2 was 20 mm Hg or less in both the liver and muscle beds. There were no significant differences in measured liver or muscle PO2 values after resuscitation with any of the three solutions in this model of hemorrhagic shock. When comparing the hemodynamic effects of resuscitation, the cardiac output was increased from shock values in all three animal groups with resuscitation, but was significantly higher in the animals resuscitated with HSD. Similarly, MAP was increased by all solutions during resuscitation, but remained significantly below baseline except in the group of animals receiving HBOC-201 (p < 0.01). HBOC-201 was most effective in both restoring and sustaining MAP and systolic blood pressure. There was excellent correlation between liver and deltoid muscle tissue oxygen values (r = 0.8, p < 0.0001).

CONCLUSION

HBOC-201 can be administered safely in small doses and compared favorably to resuscitation with HSD and LR solution in this prehospital model of hemorrhagic shock. HBOC-201 is significantly more effective than HSD and LR solution in restoring MAP and systolic blood pressure to normal values. Deltoid muscle PO2 reflects liver PO2 and thus may serve as an index of the adequacy of resuscitation in critical tissue beds.

The role of the intestine in the pathophysiology and management of severe acute pancreatitis

BACKGROUND

The outcome of severe acute pancreatitis has scarcely improved in 10 years. Further impact will require new paradigms in pathophysiology and treatment. There is accumulating evidence to support the concept that the intestine has a key role in the pathophysiology of severe acute pancreatitis which goes beyond the notion of secondary pancreatic infection. Intestinal ischaemia and reperfusion and barrier failure are implicated in the development of multiple organ failure.

DISCUSSION

Conventional management of severe acute pancreatitis has tended to ignore the intestine. More recent attempts to rectify this problem have included 1) resuscitation aimed at restoring intestinal blood flow through the use of appropriate fluids and splanchnic-sparing vasoconstrictors or inotropes; 2) enteral nutrition to help maintain the integrity of the intestinal barrier; 3) selective gut decontamination and prophylactic antibiotics to reduce bacterial translocation and secondary infection. Novel therapies are being developed to limit intestinal injury, and these include antioxidants and anti-cytokine agents. This paper focuses on the role of the intestine in the pathogenesis of severe acute pancreatitis and reviews the implications for management.

The optimal endpoint of resuscitation in trauma patients

Although it has never been prospectively validated, the base excess (BE) is regarded as the standard end-point of resuscitation in trauma patients. In a rat hemorrhage model, in this edition of Critical Care, Totapally and colleagues demonstrate that the BE is an insensitive and slowly responsive indicator of changes in intravascular volume. This contrasts with changes in the esophageal-arterial carbon dioxide gap which more closely followed changes in blood volume. Esophageal or sublingual capnometry may prove to be a useful tool for monitoring the adequacy of resuscitation in trauma victims.

When is the seriously ill patient ready to be fed?

BACKGROUND

After assessing the critically ill patient for risk of aspiration, the clinician still must decide if the patient is ready to be fed. The goal is to identify critically ill patients who are likely to tolerate enteral nutrition and attempt to minimize complications.

METHODS

A synthesis of the both clinical and animal studies to identify factors related to patient readiness for enteral nutrition.

RESULTS

The key issue to be resolved is adequacy of resuscitation and restoration of mesenteric perfusion. Currently, there is no reliable clinical tool to measure gut perfusion. The best indicators currently are stabilization of vital signs, decreasing fluid and blood requirements, normalization of the base deficit, and lactate and removal of inotropic or vasopressor support.

CONCLUSIONS

Most critically ill patients should be ready for enteral nutrition within 24 to 48 hours of intensive care unit admission. Critically ill patients who need catecholamine support, heavy sedation, or therapeutic neuromuscular blockade should probably not receive enteral nutrition until they have been stabilized.

The effect of hypothermia on calculated values using saline and automated air tonometry

OBJECTIVE

To quantify in vitro the effect of hypothermia on results obtained when performing automated air tonometry (Tonocap, Datex-Ohmeda, Instrumentarium Corp, Helsinki, Finland) and saline tonometry.

DESIGN

In vitro validation study.

SETTING

University hospital research laboratory.

INTERVENTIONS

Two TRIP sigmoid catheters, one connected to the Tonocap device and the other instilled with 2.5 mL of 0.9% saline, were placed in a saline bath at 30.3 degrees C (mean) through which 5% carbon dioxide (CO(2)) was bubbled.

MEASUREMENTS AND MAIN RESULTS

A total of 50 paired measurements were taken at 30-minute equilibration times of saline bath CO(2) tension and saline tonometry and air tonometry readings. Saline samples were analyzed at 37 degrees C and corrected for temperature. Bias and precision of each technique as a percentage of predicted CO(2) values were calculated. The Tonocap device had bias and precision values of -2.6% and +/-1.4%. Measurement of CO(2) is in the gaseous phase so that temperature correction is not required. Saline tonometry readings processed at 37 degrees C exhibited a large positive bias of 23.06% (precision +/- 7.02%). Correction for temperature improved bias to -10.98 % with a similar precision profile of +/-5.78%.

CONCLUSION

When using gastrointestinal tonometry during hypothermic cardiopulmonary bypass, saline tonometry samples should be temperature corrected. The Tonocap device proved the most accurate and precise measurement technique independent of the need for temperature correction.

Hypotensive resuscitation during active hemorrhage: impact on in-hospital mortality

BACKGROUND

Traditional fluid resuscitation strategy in the actively hemorrhaging trauma patient emphasizes maintenance of a normal systolic blood pressure (SBP). One human trial has demonstrated improved survival when fluid resuscitation is restricted, whereas numerous laboratory studies have reported improved survival when resuscitation is directed to a lower than normal pressure. We hypothesized that fluid resuscitation titrated to a lower than normal SBP during the period of active hemorrhage would improve survival in trauma patients presenting to the hospital in hemorrhagic shock.

METHODS

Patients presenting in hemorrhagic shock were randomized to one of two fluid resuscitation protocols: target SBP > 100 mm Hg (conventional) or target SBP of 70 mm Hg (low). Fluid therapy was titrated to this endpoint until definitive hemostasis was achieved. In-hospital mortality, injury severity, and probability of survival were determined for each patient.

RESULTS

One hundred ten patients were enrolled over 20 months, 55 in each group. The study cohort had a mean age of 31 years, and consisted of 79% male patients and 51% penetrating trauma victims. There was a significant difference in SBP observed during the study period (114 mm Hg vs. 100 mm Hg, p < 0.001). Injury Severity Score (19.65 +/- 11.8 vs. 23.64 +/- 13.8, p = 0.11) and the duration of active hemorrhage (2.97 +/- 1.75 hours vs. 2.57 +/- 1.46 hours, p = 0.20) were not different between groups. Overall survival was 92.7%, with four deaths in each group.

CONCLUSION

Titration of initial fluid therapy to a lower than normal SBP during active hemorrhage did not affect mortality in this study. Reasons for the decreased overall mortality and the lack of differentiation between groups likely include improvements in diagnostic and therapeutic technology, the heterogeneous nature of human traumatic injuries, and the imprecision of SBP as a marker for tissue oxygen delivery.

Effect of alcohol on the lactate/pyruvate ratio of recently injured adults

OBJECTIVE

To compare the ability of plasma (lactate) and the plasma lactate/pyruvate (L/P) ratio to predict shock-related outcome after injury and also to examine the influence of plasma ethanol on any relationships found.

DESIGN

Prospective observational study.

SETTING

Emergency departments in the UK and the Republic of South Africa.

PATIENTS

Blood samples were taken at presentation from 232 adult patients 1-23 hrs (median, 3.5 hrs) after sustaining an injury or injuries deemed sufficiently severe to require inpatient care.

MEASUREMENTS

Plasma concentrations of lactate, pyruvate, and ethanol, anatomical severity of injury, development of multiple organ failure, and 30-day survival were determined.

RESULTS

At 90% specificity for predicting subsequent mortality and/or multiple organ failure, plasma lactate >or=3.85 mmol/L was 23% (5% to 41%) more sensitive than an L/P ratio of >or=42.76. At 90% sensitivity for ruling out morbidity, plasma lactate <1.6 mmol/L is 6% (-1% to 13%) more specific than an L/P ratio of <14.08. High L/P ratios were noted to be associated with a detectable plasma alcohol level. A post hoc regression analysis showed that alcohol-positive/-negative status was a much stronger predictor of the L/P ratio than was anatomical severity of injury, shock, or time after injury.

CONCLUSIONS

Plasma lactate alone is a better predictor than the L/P ratio of shock-related outcome after injury. The interpretation of L/P ratios after injury is confounded in the presence of elevated plasma ethanol.

Assessment of gut mucosal perfusion and colonic tissue blood flow during abdominal aortic surgery with gastric tonometry and laser Doppler flowmetry

The objective of this study was to investigate the effect of infrarenal aortic cross-clamping and unclamping on gut mucosal perfusion by gastric tonometry and on sigmoid colonic tissue blood flow by laser Doppler flowmetry during abdominal aortic surgery. This was a prospective before-and-after intervention comparison study in a university hospital of 8 male patients, aged 57-87, undergoing elective infrarenal abdominal aortic surgery. Each patient was pretreated with ranitidine. Following general anesthesia, a nasogastric tonometer was inserted into the stomach. The balloon of the tonometer was filled with 2.5 mL of normal saline for gas tension and pH analysis. This process was repeated before and after aortic cross-clamping and unclamping. Gastric mucosal pHi was calculated with the Henderson-Hasselbalch equation from the arterial Hco3- and the tonometrically measured mucosal Pco2. A laser Doppler flow probe was placed in contact with the serosa of the sigmoid colon against the mesentery after the abdomen was opened. Sigmoid colonic tissue blood flow (SCBF) was assessed by the laser Doppler flowmeter. Gastric mucosal pHi by gastric tonometry and colonic tissue blood flow by laser Doppler flowmetry were measured before and after aortic cross-clamping and unclamping. Gastric mucosal pHi decreased significantly 30 minutes after aortic cross-clamping (7.37 +/-0.07) (p < 0.01), 60 minutes after aortic cross-clamping (7.39 +/-0.08) (p < 0.05), and 30 minutes after aortic unclamping (7.37 +/-0.08) (p < 0.01), compared with pHi before aortic cross-clamping (7.50 +/-0.06). Gastric mucosal pHi increased to the original level 60 minutes after aortic unclamping (7.46 +/-0.08). Since a gastric mucosal pH above 7.35 is considered normal, these mean values of pHi were clinically insignificant. However, gastric mucosal pHi decreased below 7.32 in 5 patients during abdominal aortic surgery. Gastric mucosal pHi decreased further to 7.30 in 1 patient following aortic cross-clamping and below 7.30 in 3 patients 30 minutes after aortic unclamping. SCBF decreased significantly after aortic cross-clamping (28.1 +/-4.8 mL/min/100 g) compared with the value before aortic cross-clamping (51.9 +/-11.3 mL/min/100 g) (p < 0.01). Following aortic unclamping, SCBF returned to 41.7 +/-7.4 mL/min/100 g. It is concluded that transient episodes of significant intestinal mucosal ischemia may have been encountered occasionally in patients undergoing abdominal aortic surgery, but a sigmoid colonic tissue blood flow of 41.7 +/-7.4 mL/min/100 g was sufficient to prevent postoperative ischemic colitis regardless of whether there was ligation or no ligation of inferior mesenteric artery among the studied population since none of the patients developed clinically significant ischemic colitis.

End points of resuscitation: choosing the right parameters to monitor

Determining when resuscitation is complete can be challenging, as tissue hypoperfusion can persist despite normal vital signs. This article discusses the limitations of traditional parameters used as resuscitation guidelines and describes new technologies that aid in assessing resuscitation efforts, including advances in hemodynamic monitoring and methods for obtaining global and organ-specific indexes.

The massively bleeding patient

The resuscitation of the massively bleeding patient may seem superficially to be successful once the patient's vital signs have stabilized. The restoration of stable vital signs, however, does not confirm two critical elements of a thorough physiologic resuscitation: that there is truly adequate delivery of oxygen to all tissue beds and that physiologic disturbances that may have occurred because of massive transfusion during the resuscitation process have resolved. With respect to the adequacy of oxygen delivery, the current clinical endpoints, including mixed venous oxygen saturation, cardiac output, and serum lactate, reflect global perfusion and not regional oxygenation. Of these global measures, serum lactate is currently the best indicator as to whether some circulatory beds remain inadequately perfused. Serum lactate should be followed, and, in the event that elevated levels persist, measures to augment oxygen delivery (e.g., increasing cardiac output, hemoglobin concentration, oxygen saturation) should be undertaken. Gastric tonometry provides a method for specific examination of the splanchnic circulation. The current measurement techniques, however, require steady-state conditions and make it impractical in many physiologically dynamic situations. The physiologic disturbances associated with massive resuscitation (e.g., hyperkalemia, hypocalcemia, hypomagnesemia, hypothermia) should be anticipated. Coagulation disturbances occur, especially when massive transfusion is accompanied by hypotension, hypothermia, or acidosis. Coagulation parameters should be measured with the loss of each one half of blood volume or after each 30-minute interval, whichever occurs first. Evaluation at blood volume intervals is relevant to the development of a strictly dilutional coagulopathy. The development of DIC, occurring because of tissue factor exposure or acidosis, however, is related more to the time lapsed than to the absolute volume lost or replaced.

A current concept of trauma-induced multiorgan failure

Trauma deaths continue to show a trimodal distribution: immediately at the scene, within the first 24 hours during initial resuscitation, and in the next 3 to 4 weeks as a result of multiple organ failure.(1) Failure to resuscitate adequately in the emergency department can lead to acidosis, hypothermia, and coagulopathy, which can result in multiple organ failure and cause death in these patients. Our current understanding of the initial response to shock and trauma and the development of the systemic inflammatory response syndrome and progressive organ failure is one of a continuum initiated and perpetuated by inflammation and inflammatory mediators. The pathophysiologic character, diagnosis, prevention, and treatment of traumatic injury-induced multiple organ failure are discussed.

Start with a subjective assessment of skin temperature to identify hypoperfusion in intensive care unit patients

OBJECTIVE

To determine whether physical examination alone or in combination with biochemical markers can accurately diagnose hypoperfusion.

METHODS

Data from 264 consecutive surgical intensive care unit patients were collected by two intensivists and included extremity temperature, vital signs, arterial lactate, arterial blood gases, hemoglobin, and pulmonary artery catheter values with derived indices. Days of data were divided into data collected from patients with cool extremities (cool skin temperature [CST] group) versus warm extremities (warm skin temperature [WST] group). Values are means +/- SD. Comparisons between groups were made by two-tailed unpaired t test; significance was assumed for p < or = 0.05.

RESULTS

There were 328 days of observations in the CST group versus 439 in the WST group. There were no differences (p > 0.05) between CST and WST data with regard to heart rate (107 +/- 14 vs. 99 +/- 19 beats/min), systolic blood pressure (118 +/- 24 vs. 127 +/- 28 mm Hg), diastolic blood pressure (57 +/- 14 vs. 62 +/- 15 mm Hg), pulmonary artery occlusion pressure (14 +/- 6 vs. 16 +/- 5 mm Hg), Fio2 (0.48 +/- 0.7 vs. 0.45 +/- 0.2), hemoglobin (8.8 +/- 1.6 vs. 9.3 +/- 1.3 g/dL), Pco2 (44.3 +/- 11.8 vs. 40.7 +/- 9.2 mm Hg), or Po2 (96.4 +/- 12.6 vs. 103.8 +/- 22.2 mm Hg). However, cardiac output (5.3 +/- 2.2 vs. 8.2 +/- 2.6 L/min), cardiac index (2.9 +/- 1.2 vs. 4.3 +/- 1.2 L/min/m2), pH (7.32 +/- 0.2 vs. 7.39 +/- 0.07), TCO2 (19.5 +/- 3.1 vs. 25.1 +/- 4.8 mEq/L), and Svo2 (60.2 +/- 4.4% vs. 68.2 +/- 7.8%) were all significantly lower (p < 0.05) in CST patients compared with WST patients. By comparison, lactate (4.7 +/- 1.5 vs. 2.2 +/- 1.6 mmol/L, p < 0.05) was significantly elevated in patients with cool extremities.

CONCLUSION

Combining physical examination with serum bicarbonate and arterial lactate identifies patients with hypoperfusion as defined by low Svo2 and cardiac index. Hypoperfusion may occur despite supranormal cardiac indices. Patients with cool extremities and elevated lactate levels may benefit from a pulmonary artery catheter to guide but not initiate therapy.

Intraoperative and Early Postoperative Gastric Intramucosal pH Predicts Morbidity and Mortality after Major Abdominal Surgery

The present study was undertaken to investigate the correlation between the intraoperative and postoperative gastric intramucosal pH (pHi) with important perioperative variables and to explore any potential relationship of the measured pHi with the patients’ postoperative course. A prospective study was carried out in a group of 48 patients who underwent major abdominal operations over an 8-month period at St. John Hospital and Medical Center. An automated air tonometer was used for gastric pHi monitoring. Twenty-eight elective and 20 emergency abdominal operations were performed in 23 men and 25 women. Twenty-six patients (54%) required postoperative hospitalization in the Intensive Care Unit (ICU). Seventeen patients (35%) developed early postoperative complications. The non-ICU and ICU mortality rates were 4.5 and 19.2 per cent respectively. The mean intraoperative pHi (pHiOR) and postoperative pHi (pHiPO) ranged between 7.03 and 7.58 (7.38 ± 0.12) and 6.89 and 7.56 (7.35 ± 0.12) respectively (mean ± standard deviation). There was a significant decrease of the gastric pHi at the first hour intraoperatively compared with the pHi after induction to anesthesia (7.44 vs 7.38 ± 0.14, P < 0.001). Patients who underwent emergent abdominal procedures were characterized by lower pHiOR and pHiPO values (7.43 ± 0.08 vs 7.30 ± 0.13 and 7.39 ± 0.84 vs 7.30 ± 0.15, P < 0.001 and P < 0.05). Similarly patients who required surgical ICU admission had significantly lower pHiOR and pHiPO measurements (7.3 ± 0.12 and 7.28 ± 0.12) compared with the rest (7.46 ± 0.06 and 7.43 ± 0.06; P < 0.001). Overall, lower pHiOR and pHiPO values were associated with the occurrence of postoperative complications ( P < 0.001), the postoperative mortality ( P < 0.001), the requirement for postoperative mechanical ventilator ( P < 0.001) and its duration ( P < 0.001), longer ICU stay ( P < 0.001), and prolonged hospitalization ( P < 0.05). Evidence of intraoperative and early postoperative gastric mucosal ischemia (pHiOR and pHiPO ≤ 7.32) was observed in 12 (25%) and 15 (31%) patients respectively. The incidence of postoperative complications and the mortality rate were higher in this group of patients ( P < 0.001). At a cutoff point of 7.32 gastric pHiOR gave a sensitivity of 69 per cent and specificity of 97 per cent for predicting postoperative complications as well as a sensitivity and specificity of 67 per cent and 81 per cent for predicting death. Intraoperative and early postoperative gastric pHi is a reliable predictor of patient outcome after major abdominal operations. Splanchnic ischemia may play an important role in determining early complications and survival; therapy guided by the gastric pHi might improve outcome.

Fluid resuscitation for the trauma patient

Attempts at prehospital fluid replacement should not delay the patient's transfer to hospital. Before bleeding has been stopped, a strategy of controlled fluid resuscitation should be adopted. Thus, the risk of organ ischaemia is balanced against the possibility of provoking more bleeding with fluids. Once haemorrhage is controlled, normovolaemia should be restored and fluid resuscitation targeted against conventional endpoints, the base deficit, and plasma lactate. Initially, the precise fluid used is probably not important, as long as an appropriate volume is given; anaemia is much better tolerated than hypovolaemia. Colloids vary substantially in their pharmacology and pharmacokinetics and the experimental findings from one cannot be extrapolated reliably to another. We still lack reliable data to prove that any of the colloids reduce mortality in trauma patients. In the presence of SIRS, hydroxyethyl starch may reduce capillary leak. Hypertonic saline solutions may have some benefit in patients with head injuries although this has yet to be proven beyond doubt. It is likely that one or more of the haemoglobin-based oxygen carriers currently under development will prove to be valuable in the treatment of the trauma patient.

Effect of acute hemodilution on intestinal perfusion and intramucosal pH after shock

BACKGROUND

Restoration of oxygen delivery, especially to the splanchnic bed, is of critical importance during trauma resuscitation. Acute normovolemic hemodilution (ANH) has been used to reduce blood transfusion requirement during elective surgery. The effect of hemodilution on the splanchnic circulation during hemorrhagic shock (HS) is not well defined.

METHODS

Swine were instrumented to measure systemic and splanchnic circulation effects of ANH after HS. The adequacy of the splanchnic circulation was assessed by changes in measured mucosal blood flow, mucosal tonometry, as well as by portal venous blood O2 saturation, portal venous CO2 saturation, and lactate.

RESULTS

ANH after HS resulted in a final hematocrit of 18+/-2%. Superior mesenteric artery blood flow was returned to baseline levels; however, mucosal blood flow was still only 64% of baseline levels. However, at the same time mucosal PCO2 and intramucosal pH as well as portal venous O2 and CO2 saturation had normalized.

CONCLUSION

As long as an adequate intravascular volume is maintained, hemodilution is well tolerated by the gut after HS. Concern about the adequacy of gut perfusion should not be a transfusion trigger after HS.

Inducible nitric oxide synthase gene knockout mice have increased resistance to gut injury and bacterial translocation after an intestinal ischemia-reperfusion injury

OBJECTIVE

Intestinal ischemia-reperfusion after severe shock states is often associated with bacterial translocation and intestinal barrier dysfunction. Our previous studies showed that inducible nitric oxide synthase (iNOS) gene knockout mice were resistant to endotoxin-induced bacterial translocation and ileal mucosal damage. The goal of this study was to test whether iNOS mediates bacterial translocation after intestinal ischemia-reperfusion, using iNOS knockout mice (iNOS-/-) and their wild-type littermates (iNOS+/+).

DESIGN

Prospective animal study with concurrent controls.

SETTING

Small animal laboratory.

SUBJECTS

Thirty-eight iNOS knockout mice and 51 wild-type littermates.

INTERVENTIONS

iNOS+/+ mice or iNOS-/- mice were subjected to a sham operation or 30 mins of superior mesenteric artery occlusion followed by reperfusion. Twenty-four hours after reperfusion, bacterial translocation to mesenteric lymph nodes, ileal villous damage, and cecal bacterial population were evaluated.

MEASUREMENTS AND MAIN RESULTS

Sham operation did not induce bacterial translocation, change cecal bacterial population levels, or cause ileal villous damage. Intestinal ischemia-reperfusion caused bacterial translocation in 72% of the iNOS+/+ mice but only 28% of the iNOS-/- mice. Both iNOS+/+ and iNOS-/- mice subjected to superior mesenteric artery occlusion (SMAO) in which bacterial translocation occurred had cecal bacterial population levels that were three logs higher than mice subjected to sham SMAO or mice subjected to SMAO in which bacterial translocation did not occur. The magnitude of villous injury was less in the iNOS-/- mice than the iNOS+/+ mice after SMAO, although the incidence of ileal villous damage was significantly higher in both the iNOS+/+ and iNOS-/- mice in which bacterial translocation occurred after SMAO than in the mice in which bacterial translocation did not occur after SMAO. iNOS+/+ mice subjected to SMAO had increased plasma concentrations of nitrite (NO2-) and nitrate (NO3-), and the plasma concentrations of NO2- and NO3- were highest in the mice in which bacterial translocation had occurred.

CONCLUSION

iNOS knockout mice were more resistant to intestinal ischemia-reperfusion-induced bacterial translocation and mucosal injury than wild-type mice, suggesting that iNOS might play a role in intestinal ischemia-reperfusion-induced loss of gut barrier function.

A comparison of opiate- and epidural-induced alterations in splanchnic blood flow using intra-operative gastric tonometry

Several methods are available to measure splanchnic blood flow and gut ischaemia. Tonometry is most practical for peri-operative use. Epidural blockade from T5 to T11 causes mesenteric arteriovenous vasodilation and may increase splanchnic blood flow. This study assesses the ability of tonometry to measure differential effects of opiate and epidural analgesia on splanchnic blood flow. Forty patients for elective colorectal surgery were randomly allocated to receive epidural infusion or intravenous morphine. Gastric mucosal PCO2, pHi, standard pHi, PCO2 gap and pH gap were measured after induction and on termination of surgery. These parameters were within normal limits at the end in most cases and there was no significant difference between the groups. The complication rate was similar in both groups and was not correlated with low pHi, but was correlated with blood loss. We were unable to demonstrate a difference in splanchnic perfusion, as assessed by gastric tonometry, between the two groups.

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

OBJECTIVES

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.

DESIGN

Prospective, observational study in a cohort of consecutively admitted critically ill burn patients.

SETTING

Intensive care burn unit in a university hospital.

PATIENTS

Forty-two patients with burns covering >20% of body surface area or inhalation injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

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).

CONCLUSIONS

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.