Meredith Jw

Threshold values of intramucosal pH and mucosal-arterial CO2 gap during shock resuscitation.

BACKGROUND The gastric intramucosal pH (pHi) and gastric mucosal-arterial CO2 gap (GAP) estimate visceral perfusion and predict outcome. Threshold values of these variables for use during resuscitation, however, remain poorly defined. The purpose of this study was to develop clinically derived cutoffs for both pHi and GAP for predicting death and multiple organ failure (MOF) in trauma patients. METHODS This was a cohort study of 114 consecutive trauma patients who had pHi determined at 24 hours after intensive care unit admission. The corresponding GAP for each of these values of pHi was obtained through chart review. Receiver operating characteristic curves were constructed for both pHi and GAP with respect to death and MOF. These curves were used to determine the value of each variable that maximized the sum of sensitivity and specificity in predicting outcome. chi2 tests and odds ratios were used to determine if significant differences in outcome occurred above and below these cutoff values. RESULTS Of 114 patients who had pHi determined at 24 hours after admission, 108 had corresponding GAP values available. The values of pHi and GAP that maximized sensitivity and specificity were 7.25 and 18 mm Hg, respectively. The odds ratio for pHi versus death was 4.6 and for pHi versus MOF was 4.3. The odds ratios for GAP versus death and MOF were 2.9 and 3.3, respectively. CONCLUSION In trauma patients, the ability to predict death and MOF is maximized at values of pHi less than 7.25 and GAP greater than 18 mm Hg. These values represent clinically derived cutoffs that should be useful for evaluating the adequacy of intestinal perfusion during resuscitation.

Cardiac preload, splanchnic perfusion, and their relationship during resuscitation in trauma patients.

INTRODUCTION Low gastric intramucosal pH (pHi) after shock resuscitation is associated with organ dysfunction and death in trauma patients. However, the relationship between hemodynamic performance, global oxygen transport, and pHi is unclear. Our purpose was to evaluate the relationship between intravascular volume status, splanchnic hypoperfusion, and outcome after shock resuscitation in trauma patients. DESIGN/SETTING Cohort study of 79 consecutive critically ill patients at a Level I trauma center stratified by normal (NORM, > or = 7.32) or low (LOW, < 7.32) pHi when lactate normalized (< 2.2 mmol/L). MAIN OUTCOME MEASURES Differences during resuscitation in mean values of right ventricular end-diastolic volume index (RVEDVI), pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, and oxygen consumption index. The incidence of multiple organ failure and death in the NORM and LOW groups were analyzed via odds ratio and chi 2. RESULTS Patients in the NORM group (n = 45) had a lower incidence of multiple organ failure (4 of 45 vs. 11 of 34, odds ratio 5.0, p < 0.01) and death (5 of 45 vs. 11 of 34, odds ratio 3.8, p < 0.05) than patients in the LOW group (n = 34). NORM patients had a higher initial RVEDVI (116 +/- 31 vs. 95 +/- 25 mL/m2, p < 0.001) and maintained a significantly higher RVEDVI (114 +/- 27 vs. 97 +/- 17 mL/m2, p = 0.003) throughout resuscitation than the LOW group did. There were no differences in the other studied variables. CONCLUSIONS Supranormal levels of preload during shock resuscitation are associated with better outcome. Maintaining a RVEDVI higher than 100 mL/m2 during shock resuscitation may be of benefit in critically injured patients.

Systemic inflammatory response syndrome in the trauma intensive care unit: who is infected?

BACKGROUND Systemic inflammatory response syndrome (SIRS) is common in trauma patients, and infection represents an important and treatable source of SIRS. C-Reactive protein (CRP), an acute phase protein, is elevated in infection and discriminates between infected and uninfected patients in other patient populations. Our goal was to examine the ability of CRP and other commonly used markers of infection (maximum temperature [Tmax], and white blood cell count [WBC]) to distinguish between infectious and noninfectious causes of SIRS. METHODS This was a prospective study of a consecutive series of trauma patients who spent greater than 48 hours in the intensive care unit. Studied variables included CRP, Tmax, WBC, and culture-proven infection compared with standard definitions of infection and the presence of SIRS. The ability of these variables to correctly classify patients as infected (INF) or not infected was examined by using receiver operating characteristic curves. Values on the day of infection diagnosis in the INF group and on postadmission day 5 (the mean day of onset of infection in the INF group) in the not infected group were used. Multivariate discriminant analysis was used to examine the relative contributions of Tmax and CRP in predicting infection. Significance was defined as p < 0.05. RESULTS Fifty-nine patients were admitted over a 4-month period. Of these, 35 patients (59%) had SIRS at the time of comparison (29 INF, 6 not infected). Thirty-three patients (56%) developed an infection. Both CRP and Tmax discriminated between patients with and without infection whereas WBC did not (areas under receiver operating characteristic curve: 0.86, 0.81, and 0.47, respectively). In patients with SIRS, cutoff values of 17 mg/dL for CRP (specificity 100%) and 102 degrees F for Tmax (specificity 83%) were identified. CRP added significant discriminatory power to Tmax in determining presence of infection in patients with SIRS (p = 0.003). CONCLUSION Infection must be presumed to be the source of SIRS in patients with CRP more than 17 mg/dL and Tmax more than 102 degrees F after postinjury day 4. WBC is not useful in determining the presence of infection.

Randomized, prospective comparison of increased preload versus inotropes in the resuscitation of trauma patients: effects on cardiopulmonary function and visceral perfusion.

OBJECTIVE To evaluate the effects of maintaining increased levels of preload on cardiopulmonary function and visceral perfusion during resuscitation. METHODS Randomized, prospective study of 39 consecutive trauma patients with a low right ventricular ejection fraction (<40%) admitted to a university Level I trauma center during a 10-month period. Patients were randomized to one of two groups: increased preload (PL), or normal preload with inotropes (INO). The PL group received fluid administration to maintain a target right ventricular end-diastolic volume index (RVEDVI) > or = 120 mL/m2 during resuscitation. The INO group had inotropes added according to a prospectively determined protocol and was maintained at a RVEDVI of 90 to 100 mL/m2. Systemic perfusion was assessed using oxygen transport and acid-base parameters, and pulmonary function was evaluated with PaO2/FiO2 ratio, dynamic compliance, ventilator days, and incidence of adult respiratory distress syndrome. Gut perfusion was assessed by measuring gastric intramucosal pH (pHi). Data are expressed as means +/- SD. RESULTS The mean RVEDVI was significantly higher in the PL group (n = 19) than in the INO group (n = 20) during resuscitation (119+/-18 vs. 103+/-22 mL/m2, p = 0.01). There was no difference in oxygen delivery, mixed venous oxygen saturation, lactate, PaO2/FiO2 ratio, dynamic compliance, or ventilator days between the groups. The incidence of adult respiratory distress syndrome was not significantly different (PL 31% vs. INO 50%, p > 0.1). In the patients who had pHi measured sequentially during resuscitation (PL = 13, INO = 17), the final pHi was significantly higher in the PL group (7.31+/-0.1 vs. 7.16+/-0.2, p = 0.03). CONCLUSION Patients resuscitated at higher levels of preload have significantly better visceral perfusion than those resuscitated at normal preload with addition of inotropes. This higher preload does not adversely affect pulmonary function.

Enalaprilat improves gut perfusion in critically injured patients

Inadequate splanchnic perfusnin, detected as a low gastric intramucosal pH (pHi), in the face of normal systemic perfusion predicts an increased risk for multiple organ failure after trauma. Although the exact etiology of this low pHi is unknown, angiotensin II is thought to be an important regulator of gut perfusion during and after resuscitation from shock. The purpose of this study is to determine whether enalaprilat, an angiotensin-converting enzyme inhibitor, improves gut perfusion in critically injured patients. To test this hypothesis, 18 trauma patients monitored with a nasogastric tonometer and a pulmonary artery catheter were enrolled in a prospective study. A single dose of enalaprilat, .625 mg, was given as an i.v. bolus or a 4 h infusion following systemic resuscitation. Pre- and postdrug tonometric and hemodynamic data, including cardiac index, mean arterial pressure, right ventricular end-diastolic volume index, systemic vascular resistance index, and oxygen transport variables were compared using the paired t test. Results demonstrate that pHi was significantly improved after 4 h (7.13 ± .04 to 7.19 ± .03, p = .03) and after 24 h compared with baseline (7.14 ± .04 to 7.25 ± .04, p = .04). Overall, pHi increased in 12 of 18 patients. No significant differences were observed in any of the studied hemodynamic or systemic perfusion variables including mean arterial pressure (92 ± 4 to 87 ± 4, p = .24) and oxygen delivery (669 ± 33 to 675 ± 32, p = .82). In examining the determinants of pHi, the intramucosal-arterial Pco2 difference was improved after enalaprilat administration (27 ± 6 to 17 ± 3 mmHg, p = .04) while no difference was observed in arterial bicarbonate (19.5 ± .7 to 19.7 ± .8, p = .90). Additionally, the change in pHi observed with enalaprilat correlated with predrug intramucosal-arterial Pco2 difference (r = .74, r2 = .55, p = .0005). These results demonstrate that enalaprilat improves gut perfusion as measured by gastric tonometry in critically injured patients, and that this effect appears to be independent of changes in systemic perfusion.

VOLUMETRIC ASSESSMENT OF PRELOAD IN TRAUMA PATIENTS: ADDRESSING THE PROBLEM OF MATHEMATICAL COUPLING

The availability of the volumetric thermodilution pulmonary artery catheter allows preload assessment based on ventricular volume rather than pressure. This technique has been shown clinically to be a better measure of preload than the pulmonary artery occlusion pressure (PAOP). Critics of the technique argue that the use of thermodilution to measure cardiac output (CO) accounts for the better correlation between right ventricular end-diastolic volume (RVEDV) and CO than PAOP and CO, since stroke volume derived from the CO is a common term to both RVEDV and CO. Previous studies have attempted mathematical corrections for this coupling effect, but direct comparisons using a nonthermodi-lution measure of CO have not been reported. Our objective was to evaluate the importance of mathematical coupling between RVEDV and CO by assessing the ability of RVEDV to predict CO measured by thermodilution (COTH) compared with CO simultaneously determined by the Fick principle (COFICK). We performed a prospective study of 53 consecutive trauma patients admitted to a Level I trauma center between 10/1/94 and 6/1/95 who received a volumetric pulmonary artery catheter. Using linear regression analysis, RVEDV and PAOP were correlated with simultaneous measurements of both CORCK determined via indirect calorimetry and COTH. Fishers z-transformation was used to evaluate the correlation coefficients for significant differences (p < .05). The correlation coefficients for RVEDV vs. COTH and RVEDV vs. COFICK were similar (.48 vs. 0.45, p = .76). There was a significant correlation between COTH and CORCK (r = .74, p < .001). RVEDV was significantly better than PAOP at predicting both COTH (p < .001) and COFICK (p = .04). Multivariate regression analysis confirmed that RVEDV was the only estimate of preload which was significantly related to CO. We conclude that mathematical coupling does not have a significant clinical effect on the relationship between RVEDV and CO.

Redefining cardiovascular performance during resuscitation: ventricular stroke work, power, and the pressure-volume diagram.

OBJECTIVES (1) To compare left ventricular stroke work index (SW) and left ventricular power output (LVP), hemodynamic variables that encompass blood pressure as well as blood flow, with the purely flow-derived hemodynamic and oxygen transport variables as markers of perfusion and outcome in critically injured patients during resuscitation. (2) To use the ventricular pressure-volume diagram to define characteristic hemodynamic patterns in the determinants of SW and LVP that are associated with survival. METHODS This was a cohort study at a university Level I trauma center during the course of 1 year. A consecutive series of patients was monitored with a volumetric pulmonary artery catheter during the initial 48 hours of resuscitation. Heart rate, SW, LVP, cardiac index, and oxygen delivery and consumption during resuscitation were compared using multivariate logistic regression analysis with regard to the ability to clear lactate in less than 24 hours and survival. Receiver operating characteristic curves were constructed to determine threshold values for SW and LVP. Ventricular pressure-volume diagrams were used to describe characteristic patterns in the determinants of SW and LVP in survivors and nonsurvivors. Preload was expressed as left ventricular end-diastolic volume index, afterload as aortic input impedance (Ea), and contractility as ventricular end-systolic elastance (Ees). The ratio of Ea/Ees (RATIO) was used as a measure of ventricular-arterial coupling, which describes the efficacy of energy transfer from the heart to the vascular system. RESULTS One hundred eleven patients (87 survivors, 24 nonsurvivors) met study criteria. Survivors had a significantly higher SW (4,510 +/- 1,070 vs. 3,440 +/- 980 mm Hg x mL x m(-2); p < 0.0001) and LVP (370 +/- 94 vs. 270 +/- 81 mm Hg x L x min(-2) x m(-2); p < 0.0001) than nonsurvivors. Heart rate, SW, and LVP were the only studied variables that were significantly related to lactate clearance and survival by logistic regression. Threshold values determined by the receiver operating characteristic curves were 4,000 mm Hg x mL x m(-2) for SW and 320 mm Hg x L x min(-1) x m(-2) for LVP. Survivors had better ventricular-arterial coupling than nonsurvivors, indicated by a lower RATIO (0.32 +/- 0.22 vs. 0.54 +/- 0.38; p = 0.003). This lower RATIO was attributable to lower levels of Ea (2.7 +/- 0.7 vs. 3.4 +/- 0.8 mm Hg x mL(-1) x m(-2); p = 0.0003) and a trend toward higher levels of Ees (13 +/- 11 vs. 9.9 +/- 7.3 mm Hg x mL(-1) x m(-2); p = 0.12). CONCLUSION Thermodynamic perfusion variables that encompass both pressure and flow, such as SW and LVP, are more closely related to perfusion and outcome than the purely flow-derived variables. The higher SW and LVP in survivors is related to better ventricular-arterial coupling, and therefore more efficient cardiac function. Cutoff values for LVP of 320 mm Hg x L x min(-1) x m(-2) and for SW of 4,000 mm Hg x mL x m(-2) may be useful thresholds for evaluating hemodynamic performance during resuscitation.

Systemic inflammation worsens outcomes in emergency surgical patients.

BACKGROUND: Acute care surgeons are uniquely aware of the importance of systemic inflammatory response and its influence on postoperative outcomes; concepts like damage control have evolved from this experience. For surgeons whose practice is mostly elective, the significance of such systemic inflammation may be underappreciated. This study sought to determine the influence of preoperative systemic inflammation on postoperative outcome in patients requiring emergent colon surgery. METHODS: Emergent colorectal operations were identified in the American College of Surgeons National Surgical Quality Improvement Program 2008 dataset. Four groups were defined by the presence and magnitude of the inflammatory response before operation: no inflammation, systemic inflammatory response syndrome (SIRS), sepsis, or severe sepsis/septic shock. Thirty-day survival was analyzed by Kaplan-Meier method. RESULTS: A total of 3,305 patients were identified. Thirty-day survival was significantly different (p < 0.0001) among the four groups; increasing magnitudes of preoperative inflammation had increasing probability of mortality (p < 0.0001). Hazard ratios indicated that, compared with patients without preoperative systemic inflammation, the relative risk of death from SIRS was 1.9 (p < 0.0001), from sepsis was 2.5 (p < 0.0001), and from severe sepsis/septic shock was 6.7 (p < 0.0001). Operative time of <150 minutes was associated with decreased risk of morbidity (odds ratio = 0.64; p < 0.0001). CONCLUSIONS: Upregulation of the systemic inflammatory response is the primary contributor to death in emergency surgical patients. In SIRS or sepsis patients, operations <2.5 hours are associated with fewer postoperative complications. These results further reinforce the concept of timely surgical intervention and suggest a potential role for damage control operations in emergency general surgery. LEVEL OF EVIDENCE: II, prognostic study.