Decompressive Craniectomy for Traumatic Brain Injury: Postoperative TCD Cerebral Hemodynamic Evaluation

Critical Closing Pressure and Cerebrovascular Resistance Responses to Intracranial Pressure Variations in Neurocritical Patients

BACKGROUND

Critical closing pressure (CrCP) and resistance-area product (RAP) have been conceived as compasses to optimize cerebral perfusion pressure (CPP) and monitor cerebrovascular resistance, respectively. However, for patients with acute brain injury (ABI), the impact of intracranial pressure (ICP) variability on these variables is poorly understood. The present study evaluates the effects of a controlled ICP variation on CrCP and RAP among patients with ABI.

METHODS

Consecutive neurocritical patients with ICP monitoring were included along with transcranial Doppler and invasive arterial blood pressure monitoring. Internal jugular veins compression was performed for 60 s for the elevation of intracranial blood volume and ICP. Patients were separated in groups according to previous intracranial hypertension severity, with either no skull opening (Sk1), neurosurgical mass lesions evacuation, or decompressive craniectomy (DC) (patients with DC [Sk3]).

RESULTS

Among 98 included patients, the correlation between change (Δ) in ICP and the corresponding ΔCrCP was strong (group Sk1 r = 0.643 [p = 0.0007], group with neurosurgical mass lesions evacuation r = 0.732 [p < 0.0001], and group Sk3 r = 0.580 [p = 0.003], respectively). Patients from group Sk3 presented a significantly higher ΔRAP (p = 0.005); however, for this group, a higher response in mean arterial pressure (change in mean arterial pressure p = 0.034) was observed. Exclusively, group Sk1 disclosed reduction in ICP before internal jugular veins compression withholding.

CONCLUSIONS

This study elucidates that CrCP reliably changes in accordance with ICP, being useful to indicate ideal CPP in neurocritical settings. In the early days after DC, cerebrovascular resistance seems to remain elevated, despite exacerbated arterial blood pressure responses in efforts to maintain CPP stable. Patients with ABI with no need of surgical procedures appear to remain with more effective ICP compensatory mechanisms when compared with those who underwent neurosurgical interventions.

Vasospasm Surveillance by a Simplified Transcranial Doppler Protocol in Traumatic Brain Injury

OBJECTIVE

To detect post-traumatic vasospasm in patients with traumatic brain injury (TBI), we implemented a simplified transcranial Doppler (TCD) surveillance protocol in a neurointensive care setting. In this study, we evaluate the yield of this protocol.

METHODS

Adult patients with TBI admitted to the neurointensive care unit were examined with TCD by 2 intensive care nurses trained in TCD examinations. Flow velocities of the middle cerebral arteries were recorded. TCD suspected vasospasm was defined as the mean flow velocity >120 cm/s, and when detected, the protocol recommended a supplementary computed tomography angiography. The rate of detection of TCD suspected vasospasm and the subsequent rate of radiological diagnosis of vasospasm were recorded. In multivariate logistic regression analysis, we evaluated age, initial Glasgow Coma Scale, craniotomy, and decompressive craniectomy as potential predictors of developing increased TCD velocity.

RESULTS

A total of 84 patients with TBI with a median initial Glasgow Coma Scale score of 6 were examined by TCD. TCD suspected vasospasm was found in the middle cerebral arteries of 18% of examined patients. Two-thirds of patients with TCD suspected vasospasm were investigated with a subsequent computed tomography angiography, and 80% of these patients received a radiological diagnosis of vasospasm. In logistic regression analysis, decompressive craniectomy was significantly associated with increased risk of developing TCD suspected vasospasm (odds ratio: 11.57, 95% confidence interval: 2.59-51.73, P = 0.001).

CONCLUSIONS

The implementation of a simplified TCD surveillance protocol in a neurointensive care setting yielded an 18% detection rate of TCD suspected vasospasm. In our cohort of patients with TBI, decompressive craniectomy was associated with increased risk of developing TCD suspected vasospasm.

Intracranial Compliance Assessed by Intracranial Pressure Pulse Waveform

BACKGROUND

Morphological alterations in intracranial pressure (ICP) pulse waveform (ICPW) secondary to intracranial hypertension (ICP >20 mmHg) and a reduction in intracranial compliance (ICC) are well known indicators of neurological severity. The exclusive exploration of modifications in ICPW after either the loss of skull integrity or surgical procedures for intracranial hypertension resolution is not a common approach studied. The present study aimed to assess the morphological alterations in ICPW among neurocritical care patients with skull defects and decompressive craniectomy (DC) by comparing the variations in ICPW features according to elevations in mean ICP values.

METHODS

Patients requiring ICP monitoring because of acute brain injury were included. A continuous record of 10 min-length for the beat-by-beat analysis of ICPW was performed, with ICP elevation produced by means of ultrasound-guided manual internal jugular vein compression at the end of the record. ICPW features (peak amplitude ratio (P2/P1), time interval to pulse peak (TTP) and pulse amplitude) were counterweighed between baseline and compression periods. Results were distributed for three groups: intact skull (exclusive burr hole for ICP monitoring), craniotomy/large fractures (group 2) or DC (group 3).

RESULTS

57 patients were analyzed. A total of 21 (36%) presented no skull defects, 21 (36%) belonged to group 2, whereas 15 (26%) had DC. ICP was not significantly different between groups: ±15.11 for intact, 15.33 for group 2 and ±20.81 mmHg for group 3, with ICP-induced elevation also similar between groups (p = 0.56). Significant elevation was observed for the P2/P1 ratio for groups 1 and 2, whereas a reduction was observed in group 3 (elevation of ±0.09 for groups 1 and 2, but a reduction of 0.03 for group 3, p = 0.01), and no significant results were obtained for TTP and pulse amplitudes.

CONCLUSION

In the present study, intracranial pressure pulse waveform analysis indicated that intracranial compliance was significantly more impaired among decompressive craniectomy patients, although ICPW indicated DC to be protective for further influences of ICP elevations over the brain. The analysis of ICPW seems to be an alternative to real-time ICC assessment.

Craniectomy size for subdural haematomas and the impact on brain shift and outcomes

BACKGROUND

Midline shift in trauma relates to the severity of head injury. Large craniectomies are thought to help resolve brain shift but can be associated with higher rates of morbidity. This study explores the relationship between craniectomy size and subtemporal decompression for acute subdural haematomas with the resolution of brain compression and outcomes. No systematic study correlating these measures has been reported.

METHOD

A retrospective study of all adult cases of acute subdural haematomas that presented to a Major Trauma Centre and underwent a primary decompressive craniectomy between June 2008 and August 2013. Data collection included patient demographics and presentation, imaging findings and outcomes. All imaging metrics were measured by two independent trained assessors. Compression was measured as midline shift, brainstem shift and cisternal effacement.

RESULTS

Thirty-six patients with mean age of 36.1 ± 12.5 (range 16-62) were included, with a median follow-up of 23.5 months (range 2.2-109.6). The median craniectomy size was 88.7 cm² and the median subtemporal decompression was 15.0 mm. There was significant post-operative resolution of shift as measured by midline shift, brainstem shift and cisternal effacement score (all p < .00001). There was no mortality, and the majority of patients made a good recovery with 82.8% having a Modified Rankin Score of 2 or less. There was no association between craniectomy size or subtemporal decompression and any markers of brain shift or outcome (all R² < 0.05).

CONCLUSIONS

This study suggests that there is no clear relationship between craniectomy size or extent of subtemporal decompression and resolution of brain shift or outcome. Further studies are needed to assess the relative efficacy of large craniectomies and the role of subtemporal decompression.