Objective determination of the optimal red blood cell count in diagnostic peritoneal lavage done for abdominal stab wounds

Diagnostic peritoneal lavage: is 100,000 RBCs a valid figure for penetrating abdominal trauma?

BACKGROUND

Controversy exists regarding the interpretation of diagnostic peritoneal lavage results. This is especially true in the evaluation of patients sustaining penetrating trauma, specifically stab wounds to the lower chest and abdomen. Ideally one wants to avoid missed injuries and minimize unnecessary operations.

METHODS

This is a retrospective review of 195 patients sustaining stab wounds to the anterior lower chest and abdomen at Parkland Memorial Hospital between 1993 and 2005, looking at missed injuries and false positive rates using red cell counts of 100,000, 10,000, and the standard criteria for blunt trauma including >500 white blood cells (WBCs), amylase, and/or bile.

RESULTS

The first analysis used >100,000 red blood cells (RBCs)/mm3 as a positive value. The false positive rate was 12.2%. The second analysis used >10,000 RBCs/mm3 as a positive value with a false positive rate of 44%. When considering the entire study population (195 patients), the false positive rate increased when using the lower number (>10,000) from 2.5% to 15.8% (p < 0.001). There were no missed injuries when using >100,000 red cells and/or >500 white cells, the presence of bile or amylase.

CONCLUSION

Decreasing the red blood cell count from >100,000 to >10,000 as the criteria for operating on patients with stab wounds to the anterior lower chest and/or abdomen will significantly increase the number of nontherapeutic procedures. Based on this study, >100,000 RBCs/mm3 appears to be a valid and safe number to use when evaluating these patients, particularly when used with other positive criteria such as increased white cells, bile, and amylase.

Abdominal stab wounds: diagnostic peritoneal lavage criteria for emergency room discharge

OBJECTIVE

To prospectively evaluate a method for management of abdominal stab wounds that allows for immediate emergency room discharge.

METHODS

Anterior abdominal stab wound patients were prospectively placed in a study trial during a 48-month period. Consent was obtained for all patients before study entry. Anatomic boundaries for abdominal stab wounds were costal margins, inguinal ligaments, and anterior axillary lines. Hemodynamically stable patients with negative physical examinations were entered in the study and evaluated with closed diagnostic peritoneal lavage (DPL). Patients with DPL results less than 1000 RBCs/mm3 were sent home. Patients with DPL results greater than 1000 RBCs/mm3 (including gross blood) were admitted for observation. Hemodynamically stable patients with evisceration and no abdominal tenderness had the viscera replaced in the emergency room. Eviscerated patients did not undergo DPL and were admitted for observation. Patients that presented with hemodynamic instability or peritonitis were not entered in the study and underwent immediate surgical intervention.

RESULTS

Ninety hemodynamically stable patients were entered in the study. Forty-four (49%) patients had DPL < 1000 RBCs/mm3, 34 of which were discharged home. Of the 10 admissions that qualified for discharge, 4 were admitted due to elevated ethanol levels and no family assistance, 3 were admitted to psychiatry, and 3 required other surgical procedures. No patient with DPL < 1000 RBCs/mm3 required laparotomy or had complications associated with their stab wounds. Thirty-eight (42%) patients were observed because DPL counts were greater than 1000 RBCs/mm3. Eight (21%) of these patients developed positive physical examinations that prompted exploratory laparotomy, of which five (63%) were therapeutic. There were no complications associated with delayed laparotomy. Four (4%) patients had DPL results greater than 500 WBCs/mm3, all of which underwent immediate exploratory laparotomy. Four (4%) patients presented with evisceration, one of which underwent therapeutic laparotomy.

CONCLUSION

Abdominal stab wound patients that are hemodynamically stable can be safely sent home from the emergency room when DPL counts are less than 1000 RBCs/mm3. Observation of hemodynamically stable patients allows for low laparotomy rates with minimal morbidity.

The routine use of sonography in penetrating torso injury is beneficial

BACKGROUND

Torso sonography (focused assessment with sonography for trauma [FAST]) has been added to our protocols for the evaluation of penetrating torso injury. The purpose of this study was to evaluate our recent experience and determine whether the use of FAST is beneficial.

METHODS

From January 1999 to January 2000, patients with penetrating torso injury and no clinical indication for surgery were evaluated by sonography with a selective use of other investigations. FAST consisted of sonographic views of the peritoneum and/or pericardium to determine the presence or absence of fluid.

RESULTS

During the study period, there were 238 victims of penetrating injury assessed by our trauma service, and sonography was performed in 72 (30%) patients as per our protocols. There were 31 stab, 37 gunshot/shotgun and, and 4 puncture wounds. Thirty-eight patients had peritoneal views, 6 patients had pericardial views, and 28 patients had both pericardial and peritoneal views obtained. Thirteen of 66 patients had free fluid in the peritoneal cavity and 12 of the 13 patients had a therapeutic laparotomy. No peritoneal fluid was seen in 53 of 66 patients, of whom 6 had abdominal injuries, 5 requiring surgery for diaphragm or bowel injuries. The sensitivity of FAST alone for abdominal injury was 67%, specificity was 98%, positive predictive value was 92%, and negative predictive value was 89%. Pericardial fluid was seen in 3 of 34 patients; one had a heart wound and two had negative pericardial windows. All 31 patients without pericardial fluid recovered without surgery.

CONCLUSION

The routine use of sonography in penetrating torso injury is beneficial. The detection of pericardial or peritoneal fluid is clinically useful. However, a negative FAST examination does not exclude abdominal injury, such as a diaphragm or hollow viscus wound, and further investigation or close follow-up is required.

Incremental analysis of diagnostic peritoneal lavage fluid in adult abdominal trauma

It is uncertain how much diagnostic peritoneal lavage (DPL) fluid must be recovered from abdominal trauma patients to avoid falsely low red blood cell (RBC) counts. A study was carried out to investigate this controversy. A convenience sample of adult abdominal trauma patients in a Level 1 university trauma center who were undergoing DPL with 1 L crystalloid was enrolled. Subjects with grossly positive or colorless effluent were excluded. A blinded prospective experimental design was used. Differences were evaluated among RBC counts collected at 200, 400, 600, and 800 mL of returned fluid using repeated-measures analysis of variance. In 11 patients, mean RBC counts collected at 200 and 400 mL were 24,600 (95% confidence interval [CI], 20,700 to 29,100) and 39,700 (95% CI, 33,200 to 47,100) cells/microL. These were substantially lower than the final mean count of 95,800 (95% CI, 80,000 to 115,800), measured at 800 mL (F = 23.7, P < .0001). Mean counts at 600 mL were less than those obtained at 800 mL but were not statistically different (P = .08). Two of the 11 subjects would have been misclassified (as not requiring surgery) had "early" sampling been used. In abdominal trauma patients, the RBC count of DPL fluid regularly increases as more fluid is recovered. It is important to collect >600 mL of effluent to avoid misleading, low RBC counts and misclassification of patients.

Computation of multifactorial receiver operator and predictive accuracy characteristics

The computation of the so-called receiver operator characteristics (i.e. functions that assign the maximum specificity to each value of sensitivity) is simple when the characteristics are based on univariate data. On the contrary, multivariate characteristics are difficult to compute, as the complexity of their calculation increases exponentially with the dimension of the data. This paper describes an algorithm for computation of multivariate receiver operator characteristics and derived functions (namely positive and negative predictive characteristics). The algorithm is based on several concepts that increase its computational efficiency. The most important of them is a pre-sorting of the data in each dimension and the division of each dimension into groups in which the positive and negative cases are 100% stratified. The paper also presents a risk stratification study that utilised this algorithm. The study was aimed at identifying those survivors of acute myocardial infarction who are at risk of early death. A cohort of 539 patients was stratified based on time-domain (three variables) and spectral turbulence (six variables) indices of signal-averaged electrocardiogram. The computing times of the algorithm in this study are presented in the text, and the efficiency of the computation is discussed in detail.