Studying patients of severe traumatic brain injury with severe abdominal injury in Japan.

BACKGROUND: Characteristics of extracranial injury in patients with diffuse axonal injury (DAI) have not been clarified.
MATERIALS AND METHODS: This retrospective study reviewed medical records from January 2003 to December 2007. Subjects comprised 35 patients meeting the following criteria: 1) head injury without mass lesion; 2) Glasgow coma scale (GCS) on arrival <15; and 3) magnetic resonance imaging (MRI) examination including T2*-weighted imaging. Subjects were divided into two groups: severe traumatic brain injury (TBI) group (patients with GCS ≤8, n=19) and moderate TBI group (patients with GCS >8, n=16).
RESULTS: Shock index (heart rate/systolic blood pressure) was significantly higher in the severe TBI group than in the moderate TBI group, while base excess on arrival was significantly lower in the severe TBI group than in the moderate TBI group. The abbreviated injury scale (AIS) for the face, thorax, extremities and external structures showed no significant differences between the severe TBI group, but AIS for the abdomen and the sum of extracranial AIS was greater in the severe TBI group than in the moderate TBI group. Duration of hospitalization was longer and outcomes were worse in the severe TBI group than in the moderate TBI group.
CONCLUSION: Because patients with severe TBI are more likely to have abdominal injury than patients with moderate TBI, physicians should be aware of the potential for such complications when treating severe TBI.

INTRODUCTION

Traumatic brain injury (TBI) caused by motor vehicle accidents, firearms, and falls are recorded as a leading cause of death and lifelong disability among young adults.[1-4] The Glasgow coma scale (GCS) has been extensively studied for its ability to predict outcomes in TBI patients.[3] Lower GCS is associated with worsened outcomes. Representative TBIs that could induce unconsciousness include intracranial hematoma, cerebral contusion and axonal injury.

Patients with severe major injuries in two or more different sites, who require surgical intervention to stabilize vital signs may often experience cardiac arrest in the prehospital arena and thus display poor prognosis.[45] This institute, which is a 15-year-old level 1 urban trauma center in Japan, has no record of any patients with blunt injury who were alive on arrival and required life-saving surgical operations for two different sites of injury, one of which was the head. However, patients have been encountered who showed diffuse axonal injury (DAI) and required insertion of a sensor into the intracranial space to control intracranial pressure,[6] and also underwent a major operation for injuries at other sites. No reports to date appear to have indicated characteristics of extracranial injuries in patients with DAI. The present study therefore retrospectively investigated the characteristics of extracranial injuries in patients with DAI.

MATERIALS AND METHODS

This retrospective study protocol was approved by the institutional review board. The study was conducted by reviewing medical records from January 2003 to December 2007. In this study, DAI was defined as present in a patient who showed no focal lesions and prolonged unconsciousness lasting ≥24 h. Accordingly, to identify DAI, the study included patients meeting the following criteria: 1) head injury without cerebral contusion >1 cm2 on computed tomography (CT), subdural hematoma, or epidural hematoma; 2) GCS on arrival <15; and 3) magnetic resonance imaging (MRI) including T2*-weighted imaging performed during hospitalization. The study excluded patients meeting the following criteria: 1) age >60 years or 2) death due to head injury. Subjects were divided into two groups: severe TBI group (patients with GCS ≤8) and moderate TBI group (patients with GCS >8). In this study, the term TBI was used in place of DAI because some unconscious patients with TBI did not show any traumatic lesions on MRI.

The following variables were analyzed between the severe TBI group: sex, age, mechanism of injury, incidence of skull fracture, GCS on arrival, systolic blood pressure, shock index (i.e., heart rate/systolic blood pressure),[7] status of light reflex, abbreviated injury scale (AIS)[8] of the extracranial regions (face, thorax, abdomen, extremities and external structures), sum of extracranial AIS scores, value of arterial base excess (base excess is defined as the amount of strong acid that must be added to each liter of fully oxygenated blood to return the pH to 7.40 at a temperature of 37°C and a pCO2 of 40 mmHg) as measured by blood gas analysis on arrival; presence of traumatic microbleeds detected by T2*-weighted imaging, duration of hospitalization, and Glasgow outcome score at 3 months after admission. The AIS is an anatomical scoring system in which injuries are ranked on a scale of 1–6 (1, minor; 2, moderate; 3, serious; 4, severe; 5, critical; 6, unsurvivable injury). T2*-weighted imaging was performed in the axial plane using the following parameters: repetition time, 900 ms; echo time, 30 ms; excitations, 2; flip angle, 200°; matrix, 256 Χ 192; section thickness, 5 mm with a 2.5-mm gap, and imaging time, 2 min 56 s. All foci >1 mm in diameter showing signal hypointensity on T2*-weighted imaging were defined as traumatic microbleeds.

Statistical analyses were performed using the unpaired Student's t-test and the χ2 test. Values of P<0.05 were considered indicative of a statistically significant difference.

RESULTS

A total of 469 patients with head injury were admitted during the investigation period. Of these, 138 patients >60 years old, 53 patients with cerebral herniation, and 100 patients with intracranial mass lesions due to cerebral contusion and/or intracranial hematoma were excluded. Of the remaining 178 patients, 113 were alert on arrival and were excluded. Thirty-five of the remaining 65 patients showed persistent disturbance of consciousness for ≥24 h after admission and underwent MRI, and were thus defined as subjects in this study (the severe TBI group, n=19; the moderate TBI group, n=16).

No significant differences were apparent between the two groups with regard to sex, age, mechanism of injury or incidence of skull fracture [Table 1].

Table 1

Subject background data

Shock index was significantly higher in the severe TBI group than in the moderate TBI group, while base excess on arrival was lower in the severe TBI group than in the moderate TBI group [Table 2].

Table 2

Physiological data and AIS on arrival

AIS of the face, thorax, extremities and external structures showed no significant differences between the two groups, but AIS of the abdomen and the sum of extracranial AIS scores were higher in the severe TBI group than in the moderate TBI group [Table 3]. Four patients in the severe TBI group showed abdominal injury requiring surgery (diaphragmatic rupture, n=2; splenic rupture, n=1; bladder rupture, n=1), but the moderate TBI group included no such cases (P=0.1). In addition, the severe TBI group included four patients with pelvic fractures, whereas the moderate TBI group had no such cases (P=0.1).

Table 3

AIS for extracranial injury on arrival

The number of traumatic microbleeds detected by MRI was higher in the severe TBI group than in the moderate TBI group [Table 4].

Table 4

Results of MRI

Duration of hospitalization was longer and outcomes were worse in the severe TBI group than in the moderate TBI group [Table 5]. All subjects in both the severe TBI groups survived.

Table 5

Outcomes

None of the remaining 434 patients with blunt trauma who were excluded from the study and were alive on arrival required life-saving surgery for two different sites of injury, one of which was the head. Only one of the patients excluded from the study showed DAI and acute subdural hematoma requiring surgery, and underwent delayed repair for diaphragmatic rupture.[9]

DISCUSSION

This study demonstrated that patients with severe TBI were more likely to have abdominal injury than patients with moderate TBI, representing the first investigation to report such a relationship. The combination of head and abdominal injuries is usually rare,[1011] maybe because the abdomen is relatively far from the head compared to other regions, and is protected by the bony thorax and pelvis. As a result, the abdomen and head might rarely receive the same high-energy impact at the same time. DAI forms when axons undergo rapid stretching as a result of angular acceleration, damaging the axonal cytoskeleton and resulting in a loss of elasticity and impairment of axoplasmic transport.[12-15] Subsequent swelling of the axon occurs with discrete bulb formations or elongated varicosities that accumulate transported proteins. These swollen axons may become disconnected and contribute to additional neuropathological changes in brain tissue, resulting in the formation of DAI. DAI can occur without direct impact to the head.[15] DAI occurs more frequently with force applied in the coronal plane, rather than in the sagittal or axial planes.[15-18] The severity of DAI depends on the energy of the impact.[19] Two cases in the severe TBI group showed diaphragmatic rupture, induced when the body quickly decelerated while the organs continued to move downward or forward at a much higher velocity, tearing vessels and tissues from the normal points of attachment.[20] Rapid changes in acceleration or deceleration to the head and abdomen, such as moving rapidly and then suddenly hitting the ground in a traffic accident or fall, could be associated with a rare combination of injuries to the head and abdomen.

Shock index was higher in the severe TBI group than in the moderate TBI group in the current series, while base excess on arrival was lower in the severe TBI group than in the moderate TBI group. Generally, isolated head injury without cerebral herniation rarely induces hypotension.[5] In addition, no correlation has been observed between base excess and severity of head injury.[21] Hemorrhaging from extracranial injuries in a patient with severe TBI tends to result in hemorrhagic shock following a reduction in base excess due to hypoperfusion of tissues, as severe TBI is obviously associated with more severe extracranial injuries than moderate TBI.[22] Such hypotension could induce a second brain insult to the head injury,[23] so hypotension may affect the outcomes in severe TBI.

The association seen between the number of traumatic microbleeds detected on MRI and outcomes has also been reported in several previous studies.[624]

TBI itself does not necessarily represent a medical emergency requiring treatment; immediate concerns are amnesia (a mild form of DAI) and damage to the brainstem (a severe form of DAI). Both these possibilities may be excluded in the present case, as we selected surviving patients with prolonged unconsciousness. Clinically, patients with amnesia could still complain of pain induced by any concomitant organ injury, so there is little chance of overlooking hidden injuries. In contrast, severe brainstem injuries can easily prove lethal by causing malfunctions in respiration and circulation. Patients with such injuries tend to present in a deeply comatose state, and thus may be more likely to have abdominal injuries in comparison with patients with severe TBI, as more severe unconsciousness was associated with a greater risk of the presence of abdominal injury according to the present results.

Patients with severe TBI were more likely to have abdominal injuries when compared with patients showing moderate TBI. Hidden organ injuries could be missed because unconscious patients are unable to complain about injuries. From this retrospective study, it appears that physicians should be aware of the possibility of such co-morbidities when treating severe DAI.

CONCLUSION

Patients with severe TBI are more likely to have abdominal injury than patients with moderate TBI. Physicians should thus be aware of the possibility of such complications when treating severe TBI.