Michael C. Chang

Prospective evaluation of vacuum-assisted fascial closure after open abdomen: planned ventral hernia rate is substantially reduced.

Objective:The goal of this report is to examine the success of vacuum-assisted fascial closure (VAFC) under a carefully applied protocol in abdominal closure after open abdomen. Summary Background Data:With the development of damage control techniques and the understanding of abdominal compartment syndrome, the open abdomen has become commonplace in trauma patients. If the abdomen is not closed in the early postoperative period, the combination of adhesions and fascial retraction frequently make primary fascial closure impossible and creation of a planned ventral hernia is required. We have previously reported our experience with the development of a technique for VAFC that allowed for closure of the fascia in many such patients long after initial operation. During this previous study, during which the technique was being developed, VAFC was successful in 69% of patients in whom it was applied, and 22 patients were successfully closed at ≥ 9 days after initial surgery (range, 9 to 49 days). A protocol for the use of VAFC in patients with open abdomen was developed on the basis of these data and has been employed since October 2001. The outcome of this protocols use is examined. Methods:This is a prospective evaluation of all trauma patients admitted to Wake Forest University Baptist Medical Center over a 19-month period who required management with an open abdomen. VAFC employs suction applied to a large polyurethane sponge under an occlusive dressing in the wound and allows for constant medial traction of the abdominal fascia. It is attempted in all patients in whom the rectus muscles and fascia are intact. Studied variables include fascial closure rate, time to closure, incidence of wound dehiscence, and hernia development after closure. Results:From November 1, 2001, through May 31, 2003, 212 laparotomies were performed in injured patients; 53 (25%) of these patients required open abdomen management. Mean injury severity score for the group was 34, with an average abdominal abbreviated injury score of 2.9. Forty-five (78%) survived until abdominal closure. Vacuum dressings were used in all 45 but VAFC was not attempted in 2 patients (1 due to development of enterocutaneous fistula, 1 because a rectus flap was used for another wound). Closure rate in those undergoing VAFC was 88% (38), with mean time to closure being 9.5 days. This is significantly higher than the 69% rate of fascial closure during the time in which the technique was developed (P = 0.03). Twenty-one patients (48%) were closed at ≥ 9 days (range, 9 to 21 days). Two patients (4.6%) developed wound dehiscence and underwent successful reclosure. One patient (2.3%) developed a ventral hernia on follow-up, which has since been repaired Conclusions:The use of VAFC under a carefully defined protocol has resulted in significantly higher fascial closure rates, obviating the need for subsequent hernia repair in most patients. The utility of this technique is not limited to the early postoperative period, but it can be successful as much as 3 to 4 weeks after initial operation.

External fixation or arteriogram in bleeding pelvic fracture: initial therapy guided by markers of arterial hemorrhage.

BACKGROUND Bleeding pelvic fractures (BPF) carry mortality as high as 60%, yet controversy remains over optimal initial management. Some base initial intervention on fracture pattern, with immediate external fixation (EX FIX) in amenable fractures aimed at controlling venous bleeding. Others feel ongoing hemodynamic instability indicates arterial bleeding, and prefer early angiography (ANGIO) before EX-FIX. Our aim was to evaluate markers of arterial bleeding in patients with BPF, thus identifying patients requiring early ANGIO regardless of fracture pattern. METHODS Patients with pelvis fracture were identified from a Level I trauma center registry over a 7-year period and records reviewed. From this group, two subsets were analyzed: those with initial hypotension related to pelvic fracture, and those without hypotension who underwent pelvic ANGIO. Data included hemodynamics, response to resuscitation, presence of contrast blush on CT, fracture treatment and outcome. Adequate response to initial resuscitation (R) was defined as a sustained (>2 hours) improvement of systolic blood pressure to >90 mm Hg systolic after the administration of < or = 2 units packed red blood cells. Those with repeated episodes of hypotension despite resuscitation were classified as non-responders (NR) RESULTS: From 1/94-1/01, 1171 patients were admitted with pelvic ring fracture. Thirty-five (0.3%) had hypotension attributable to pelvis fracture. 28 fell into the NR group, and 26 of these underwent ANGIO. Nineteen (73%) showed arterial bleeding while 3 resuscitation response patients underwent ANGIO with none demonstrating bleeding (p = 0.03). Sensitivity and specificity of inadequate response to initial resuscitation for predicting the presence of arterial bleeding on ANGIO were 100% and 30% respectively while negative and positive predictive value were 100% and 73%. In patients with fractures amenable to external fixation (n = 16), 44% had arterial bleeding on ANGIO, and all were in the NR group. An additional 17 patients without hypotension also underwent ANGIO. Contrast blush on admission CT was seen in 4, 3 of which had arterial bleeding seen on ANGIO (75%). Sensitivity and specificity for contrast blush in predicting bleeding on ANGIO were 60% and 92% with positive and negative predictive value being 75% and 85%. CONCLUSIONS In patients with hypotension and pelvic fracture, therapy selection based on initial response to resuscitation in BPF yields a 73% positive ANGIO rate in NR patients. Delay in ANGIO for EX FIX in patients with amenable fractures would have delayed embolization in the face of ongoing arterial bleeding in 44% of patients. In stable patients with pelvic fracture, contrast blush also indicates a high likelihood of arterial injury and ANGIO is indicated. Optimal therapy in the face of BPF requires early determination of the presence of arterial bleeding so that ANGIO can be rapidly obtained, and response to initial resuscitation as well as the presence of contrast blush aid in this decision.

Estimation of intra-abdominal pressure by bladder pressure measurement: validity and methodology.

BACKGROUND Increased intra-abdominal pressure (IAP) is an adverse complication seen in critically ill, injured, and postoperative patients. IAP is estimated via the measurement of bladder pressure. Few studies have been performed to establish the actual relationship between IAP and bladder pressure. The purpose of this study was to confirm the association between intravesicular pressure and IAP and to determine the bladder volume that best approximates IAP. METHODS Thirty-seven patients undergoing laparoscopy had intravesicular pressures measured with bladder volumes of 0, 50, 100, 150, and 200 mL at directly measured intra-abdominal pressures of 0, 5, 10, 15, 20, and 25 mm Hg. Correlation coefficients and differences were then determined. RESULTS Across the IAP range of 0 to 25 mm Hg using all of the tested bladder volumes, the difference between IAP and intravesicular pressures (bias) was -3.8 +/- 0.29 mm Hg (95% confidence interval) and measurements were well correlated (R2 = 0.68). Assessing all IAPs tested, a bladder volume of 0 mL demonstrated the lowest bias (-0.79 +/- 0.73 mm Hg). When considering only elevated IAPs (25 mm Hg), a bladder volume of 50 mL revealed the lowest bias (-1.5 +/- 1.36 mm Hg). A bladder volume of 50 mL in patients with elevated IAP resulted in an intravesicular pressure 1 to 3 mm Hg higher than IAP (95% confidence interval). CONCLUSION Intravesicular pressure closely approximates IAP. Instillation of 50 mL of liquid into the bladder improves the accuracy of the intravesicular pressure in measuring elevated IAPs.

Right ventricular end-diastolic volume index as a predictor of preload status in patients on positive end-expiratory pressure

OBJECTIVE To evaluate the clinical utility of right ventricular end-diastolic volume index (RVEDVI) and pulmonary artery occlusion pressure (PAOP) as measures of preload status in patients with acute respiratory failure receiving treatment with positive end-expiratory pressure. DESIGN Prospective, cohort study. SETTING Surgical intensive care unit in a Level I trauma center/university hospital. PATIENTS Sixty-four critically ill surgical patients with acute respiratory failure. INTERVENTIONS All patients were treated for acute respiratory failure with titrated levels of positive end-expiratory pressure (PEEP) with the goal of increasing arterial oxygen saturation to > or =0.92, reducing FIO2 to <0.5, and reducing intrapulmonary shunt to < or =0.2. Serial determinations of RVEDVI, PAOP, and cardiac index (CI) were recorded. MEASUREMENTS AND MAIN RESULTS Two hundred-fifty sets of hemodynamic variables were measured in 64 patients. The level of PEEP ranged from 5 to 50 cm H2O (mean 12+/-9 [SD] cm H2O). At all levels of PEEP, CI correlated significantly better with RVEDVI than with PAOP. At levels of PEEP > or =15 cm H2O, CI was inversely correlated with PAOP, but remained positively correlated with RVEDVI. CONCLUSIONS CI correlates significantly better with RVEDVI than PAOP at all levels of PEEP up to 50 cm H2O. RVEDVI is a more reliable predictor of volume depletion and preload recruitable increases in CI, especially in patients receiving higher levels of PEEP where PAOP is difficult to interpret.

Gastric tonometry supplements information provided by systemic indicators of oxygen transport.

HYPOTHESIS Assessment of splanchnic perfusion by gastric intramucosal pH (pHi) adds to the information provided by systemic indicators of oxygen transport. SETTING University Hospital level I trauma center. DESIGN Prospective study in 20 critically ill trauma patients comparing pHi with base deficit, lactate, oxygen delivery, and oxygen consumption (indexed to body surface area), mixed venous oxygen saturation (Svo2), oxygen utilization coefficient, and arterial pH. All measurements were obtained at admission, 1, 2, 4, 8, 16, and 24 hours, or at death. MAIN OUTCOME MEASURES Correlation of pHi with the measured systemic variables, prediction of organ dysfunction, development of multiple organ dysfunction syndrome, and mortality. RESULTS There was a poor correlation between pHi and the systemic hemodynamic and oxygen transport variables. Patients with a low pHi (< 7.32) on admission who did not correct within the initial 24 hours had a higher mortality (50% vs. 0.0%, p = 0.03) and incidence of organ dysfunction (2.6 organs/patient vs. 0.62 organs/patient, p = 0.02) than those who did. Using logistic regression analysis, only pHi, base deficit, and Svo2 were significantly associated with mortality during the study period. At 24 hours, only pHi was different between patients who developed multiple organ dysfunction syndrome and those who did not. There was a threshold value for pHi (7.10) which identified those patients who would go on to develop multiple organ dysfunction syndrome. CONCLUSIONS Uncorrected splanchnic malperfusion is associated with a higher incidence of organ dysfunction and mortality. Gastric tonometry supplements information provided by systemic indicators of oxygen transport during resuscitation of critically ill trauma patients.

Videotape review leads to rapid and sustained learning

BACKGROUND Performance review using videotapes is a strategy employed to improve future performance. We postulated that videotape review of trauma resuscitations would improve compliance with a treatment algorithm. METHODS Trauma resuscitations were taped and reviewed during a 6-month period. For 3 months, team members were given verbal feedback regarding performance. During the next 3 months, new teams attended videotape reviews of their performance. Data on targeted behaviors were compared between the two groups. RESULTS Behavior did not change after 3 months of verbal feedback; however, behavior improved after 1 month of videotape feedback (P <0.05) and total time to disposition was reduced by 50% (P <0.01). This response was sustained for the remainder of the study. CONCLUSIONS Videotape review can be an important learning tool as it was more effective than verbal feedback in achieving behavioral changes and algorithm compliance. Videotape review can be an important quality assurance adjunct, as improved algorithm compliance should be associated with improved patient care.

Elevated arterial base deficit in trauma patients: a marker of impaired oxygen utilization

BACKGROUND In trauma patients, the admission value of arterial base deficit stratifies injury severity, predicts complications, and is correlated with arterial lactate concentration. In theory, elevated base deficit and lactate concentrations after shock are related to oxygen transport imbalance at the cellular level. The purpose of this study was to test the hypothesis that an elevated base deficit in trauma patients is indicative of impaired systemic oxygen utilization and portends poor outcomes. METHODS This study was a retrospective analysis of a prospectively collected database. The study population included all patients admitted to the trauma intensive care unit at a Level 1 trauma center during a 12-month period who were monitored with a pulmonary artery catheter and serial measurements of lactate and base deficit, and who achieved a normal arterial lactate concentration (< 2.2 mmol/L) with resuscitation. The patients were divided into those who maintained a persistently high base deficit (> or = 4 mmol/L) and those who achieved a low base deficit (< 4 mmol/L) during resuscitation. RESULTS One-hundred patients (mortality 20%) were monitored with a pulmonary artery catheter and achieved a normal arterial lactate concentration. The mean age+/-SD (SEM) of the group was 37+/-17 years and the Injury Severity Score was 25+/-11. Subgroup analysis revealed that patients with a persistently high base deficit (n=26) had higher rates of multiple organ failure (35% versus 5%, p < 0.001) and death (50% versus 9%, p < 0.00001) compared with patients who achieved a low base deficit. Patients with a persistently high base deficit also had lower oxygen consumption (126+/-40 mL/m2 versus 156+/-30 mL/m2, p=0.01 at 48 hours) and a lower oxygen utilization coefficient (0.20+/-0.05 versus 0.24+/-0.03, p=0.01 at 48 hours) compared with patients with a low base deficit. At 48 hours, both oxygen consumption (r=-0.44, [r, correlation coefficient] p=0.002) and oxygen utilization (r=-0.46, p=0.001) had a significant negative correlation with base deficit. CONCLUSIONS In trauma patients, a persistently high arterial base deficit is associated with altered oxygen utilization and an increased risk of multiple organ failure and mortality. Serial monitoring of base deficit may be useful in assessing the adequacy of oxygen transport and resuscitation.

Effects of Abdominal Decompression on Cardiopulmonary Function and Visceral Perfusion in Patients with Intra-abdominal Hypertension

OBJECTIVE Increased intra-abdominal pressure (IAP) compromises cardiopulmonary function and visceral perfusion. Our goal was to characterize acute changes in these subsystems associated with operative abdominal decompression. PATIENT POPULATION A series of 11 consecutive injured patients monitored with a pulmonary artery catheter and nasogastric tonometer in whom operative decompression was performed. Indications for decompression included oliguria or progressive acidosis despite aggressive resuscitation in the presence of elevated IAP (>25 mm Hg). MAIN OUTCOME MEASURES Studied hemodynamic variables included pulmonary artery occlusion pressure (PAOP), right ventricular end-diastolic volume index (RVEDVI), and cardiac index (CI). Pulmonary variables included shunt fraction (Qs/Qt) and dynamic compliance (Cdyn). Visceral perfusion was assessed using hourly urine output 4 hours before and after decompression (UOP) and gastric intramucosal pH (pHi). Mean values before and after decompression were compared using the paired t test. Linear regression and Fishers z transformation were used to evaluate the relationships between RVEDVI, PAOP, CI, and IAP. IAP was transduced via bladder pressures. Significance was defined as p < 0.05. Data are expressed as means+/-SD. RESULTS IAP decreased with decompression (49+/-11 to 19+/-6.8 mm Hg; p < 0.0001). RVEDVI improved independent of CI and correlated better (p < 0.01) with CI (r =0.49, p=0.04) than PAOP did (r=-0.36, p=0.09). PAOP correlated significantly with IAP (r=0.45, p=0.04). Decompression resulted in significant improvements in Qs/Qt, Cdyn, UOP, and pHi. CONCLUSION Abdominal decompression in patients with increased IAP improves preload, pulmonary function, and visceral perfusion. Elevated IAP has important effects on PAOP, which makes the PAOP an unreliable index of preload in these patients.

The appropriate diagnostic threshold for ventilator-associated pneumonia using quatititative cultures

BACKGROUND The use of quantitative cultures of the bronchoalveolar lavage (BAL) effluent to distinguish between posttraumatic inflammatory response and ventilator-associated pneumonia (VAP) is becoming more common. However, the diagnostic threshold of either 10 or 10 colonies/mL remains debatable. Because mortality from VAP is related to treatment delay, some have chosen a lower diagnostic threshold (>10 colonies/mL). This may result in unnecessary antibiotic use with its sequelae: increased resistant organisms, antibiotic-related complications, and increased costs. The purpose of this study is to determine the optimal diagnostic threshold for VAP diagnosis using quantitative cultures of the BAL effluent. METHODS Data on patients with fiberoptic bronchoscopy with BAL are maintained in a prospectively collected database at our Level I trauma center. This database was reviewed for timing and frequency of BAL and the colony counts of each organism identified. Indication for bronchoscopy was clinical evidence of VAP. VAP was defined as >10 colonies/mL in the BAL effluent. A false-negative BAL was defined as any patient who had <10 colonies/mL and developed VAP with the same organism up to 7 days after the previous culture. RESULTS Over a 46-month period, 526 patients underwent 1,372 fiberoptic bronchoscopy procedures with BAL. Of these, 72% were male patients, 91% followed blunt injury, and mean age and Injury Severity Score were 43 years and 30, respectively. Overall mortality was 14%. There were 1,898 organisms identified (42% were gram-positive and 58% were gram-negative). VAP was diagnosed in 38% of BAL. Overall, there were 43 episodes in 38 patients defined as false-negative (3%). The false-negative rate was 9% in patients with 10 organisms. The most common false-negative organisms were Pseudomonas and Acinetobacter species. CONCLUSION The VAP diagnostic threshold for quantitative BAL in trauma patients should be >10 colonies/mL. One may consider a threshold of >10 colonies/mL in severely injured patients with Pseudomonas or Acinetobacter species.

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.