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Predicting major hemorrhage in patient with pelvic fracture J Trauma. 2006;61:346~352 Int. 林鼎博
Pelvic fracture can be an important source of major hemorrhage. • No reliable noninvasive method exists for predicting the hemorrhage. • To develop a clinical prediction rule to identify the high risk of major hemorrhage. Abstract • Retrospective cohort study • Collect subject with pelvic fracture from blunt force mechanism at a single level one trauma center during 4.3 year. • Logistic regression was used to formulate a clinical prediction rule. • Eligible subjects 627 of 783 patients • Hct < 30 • HR > 130/min • Displaced obturator ring fracture • Pubic symphyseal wide diastasis Probability of major hemorrhage can be estimated from initial pelvic radiograph, pulse, and hematocrit.
Background (1) • Pelvic fracture is a major source of mortality in high energy trauma. • Mortality rate = 10~26% • May be potentially life threatening arterial hemorrhage in 5~20% of patients. • Angiography with embolization is considered to be an effective treatment for arterial hemorrhage. • Knowing which pelvic fracture patients are likely to have serious arterial hemorrhage is important.
Background (2) • There have been numerous previous investigation ： • Young-Burgess classification scheme： • Classify fracture patterns based on mechanism of injury and direction of causative force • Association have been identified between posterior and shear-force fracture and arterial hemorrhage. • No clinical prediction rule has been proposed.
Background (3) • The objective of this study is to develop a clinical prediction rule to identify subjects at high risk of pelvic arterial hemorrhage. • Rule would be applicable at initial presentation of the trauma patient, before CT and angiography.
Method (1) • Retrospective cohort study • At a single urban Level I trauma center • Consisting of all nonpenetrating trauma victims that sustained fracture of the pelvis. • Fracture was visible on initial resuscitation area AP portable pelvic radiograph. • During the 4.3 year period from January 1, 1997 to April 30, 2001
Method (2) • Exclusion rule： • Initially evaluated at a different medical center and transferred • Subjects who died before performance of pelvic radiography. • Individuals collecting data on potential predictors were blinded to outcomes and individuals assessing outcomes were blinded to potential predictors.
Method (3) • Ascertainment of potential predictors： • Age, gender, mechanism of injury, pulse, and blood pressure, and laboratory values were available at medical record notes. • X-ray was interpreted by a board certified radiologist with extensive experience in emergency radiology • Record location and displacement of fracture and joint diastasis in the pelvis. • Interobserver agreement between radiologists was determined by independent reading of 10% of the images and calculation of the kappa statistic for agreement. ( -1< kappa <1, >0.4 is useful )
Method (4) • Ascertainment of major hemorrhage： • arterial extravasation on angiography • high volume pelvic hematoma on CT scan ( >600ml ) • high transfusion requirement in the absence of other source of major hemorrhage. ( >6U )
Method (5) • Bivariate logistic regression was used to identify those clinical and radiographic factors associated with major pelvic hemorrhage (exclude kappa < 0.4). • Multiple logistic regression models were constructed to determine which potential predictors were important. • Perform modeling with different transformation of the predictive variables and different interaction terms with a predictor variable and with age.
61/% were men • Average age were 37.4 y/o • Most common mechanism was motor vehicle crash (52%) • The Abbreviated Injury Scale were higher in the major pelvic hemorrhage group. • Most pelvic fracture subjects had some evidence of hemodynamic compromise. • tachycardia (HR >100 in 76%) • decreased hematocrit (<30 in 34%) • hypotension (sBP < 90mmHg in 22%)
The most common injury locations were the obturator rings (71%) • Injuries displaced more than 1 cm were present in 256 (41%)
Q：A patient with a displaced (>1cm) obturator ring fracture, Hct = 25% HR = 142 /min
Discussion (1) • A major strength of this prediction rule is reliance on both patient physiology and injury anatomy. • Injury locations are a relatively straight-forward assessment of obturator ring fracture and pubis symphysis diastasis.
Discussion (2) • 3~4分：Angiography and embolization may parallel or supercede other interventions including laparotomy. • 2分： Angiography is the first line intervention in patients without obvious major intra-abdominal or intra-thoracic bleeding. • 1分：Angiography should only be considered after other relevant diagnostic tests have been performed, and only if hemodynamic instability worsens or persists. • 0分：Angiography is not indicated unless other interventions aimed at addressing hemodynamic instability have failed.
Discussion (3) • We found little association between age and pelvic fracture related hemorrhage. This is in contradistinction to a recent article by Kimbrell.
Discussion (4) • Limitation： • Data developed on a specific patient population • retrospective • Need a gold standard test to determine whether they have major pelvic hemorrhage. • Pelvic radiographs were often technically limited by the ongoing resuscitation efforts.
Discussion (5) • Anterior injury locations were more important in predicting major hemorrhage than injuries in the posterior pelvis. • This is counterintuitive, as the major structural integrity in the pelvis is provided by the posterior osseous and ligamentous structures. • To be useful, a clinical decision rule must be both predictive and reliable. • Our data indicate that evaluation of the posterior pelvis on trauma radiographs is not sufficiently reliable.
Discussion (6) • This clinical prediction rule achieves neither perfect sensitivity nor perfect specificity. • High sensitivity, low specificity • 把p’t都抓去做angio • However, there are also potential adverse consequences to the patients with angiography and embolization. • Low sensitivity, high specificity 更不好 • The use of two or more predictors as a criterion provides a compromise between sensitivity (75%) and specificity (83%)
Summary • HR >= 130 • Hct <= 30 • diastasis of the pubic symphysis >= 1 cm • obturator ring fracture displaced >= 1 cm • Number of predictors： 0 1.6% 1 14% 2 46% 3.4 66%