Age-Dependent Effects of Haptoglobin Deletion in Neurobehavioral and Anatomical Outcomes Following Traumatic Brain Injury

Cerebral hemorrhages are common features of traumatic brain injury (TBI) and their presence is associated with chronic disabilities. Recent clinical and experimental evidence suggests that haptoglobin (Hp), an endogenous hemoglobin-binding protein most abundant in blood plasma, is involved in the intrinsic molecular defensive mechanism, though its role in TBI is poorly understood. The aim of this study was to investigate the effects of Hp deletion on the anatomical and behavioral outcomes in the controlled cortical impact model using wildtype (WT) C57BL/6 mice and genetically modified mice lacking the Hp gene (Hp(-∕-)) in two age cohorts [2-4 mo-old (young adult) and 7-8 mo-old (older adult)]. The data obtained suggest age-dependent significant effects on behavioral and anatomical TBI outcomes and recovery from injury. Moreover, in the adult cohort, neurological deficits in Hp(-∕-) mice at 24 h were significantly improved compared to WT, whereas there were no significant differences in brain pathology between these genotypes. In contrast, in the older adult cohort, Hp(-∕-) mice had significantly larger lesion volumes compared to WT, but neurological deficits were not significantly different. Immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) revealed significant differences in microglial and astrocytic reactivity between Hp(-∕-) and WT in selected brain regions of the adult but not the older adult-aged cohort. In conclusion, the data obtained in the study provide clarification on the age-dependent aspects of the intrinsic defensive mechanisms involving Hp that might be involved in complex pathways differentially affecting acute brain trauma outcomes.

The epidemiology of vasospasm in children with moderate-to-severe traumatic brain injury

OBJECTIVE

To gain a description of the prevalence and time course of vasospasm in children suffering moderate-to-severe traumatic brain injury.

DESIGN

A prospective, observational study was performed. Children with a diagnosis of traumatic brain injury, a Glasgow Coma Score less than or equal to 12, and abnormal head imaging were enrolled. Transcranial Doppler ultrasound was performed to identify and follow vasospasm. Diagnostic criteria included flow velocity elevation more than or equal to 2 sd above age and gender normal values for the middle cerebral and basilar arteries. Additional criteria required for vasospasm diagnosis in the middle cerebral artery was a ratio of flow in the middle cerebral artery to extracranial internal carotid artery more than or equal to 3.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-nine children were included. The prevalence of middle cerebral artery vasospasm in children with moderate traumatic brain injury (Glasgow Coma Score, 9-12) was 8.5% and was 33.5% in those with severe traumatic brain injury (Glasgow Coma Score, ≤ 8). The prevalence of basilar artery vasospasm in children with moderate traumatic brain injury was 3% and with severe traumatic brain injury was 21%. Mean time to onset of vasospasm was 4 days (± 2 d) in the middle cerebral arteries and 5 days (± 2.5 d) in the basilar artery. Mean duration of vasospasm in the middle cerebral artery was 2 days (± 2 d) and 1.5 days (± 1 d) in the basilar artery. Children in whom vasospasm developed were more likely to have been involved in motor vehicle accidents, had higher Injury Severity Scores, had fever at admission, and had lower Glasgow Coma Score scores. Good neurologic outcome (Glasgow Outcome Score Extended Pediatric version of ≥ 4) at 1 month from injury was seen in 76% of those with moderate traumatic brain injury without vasospasm and in 40% of those with vasospasm. In those with severe traumatic brain injury, good neurologic outcome was seen in 29% of those children without vasospasm and in 15% of those with vasospasm.

CONCLUSIONS

Vasospasm occurs in a sizeable number of children with moderate and severe traumatic brain injury. Children in whom vasospasm developed were more likely to have been involved in a motor vehicle accident, had higher Injury Severity Scores, had fever at admission, and had lower Glasgow Coma scores than in those whom vasospasm did not develop. Based on these findings, we recommend aggressive screening for posttraumatic vasospasm in these patients. Future studies should establish the relationship between vasospasm and long-term functional outcomes and should also evaluate potential preventative or therapeutic options for vasospasm in these children.

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage and traumatic brain injury

OPINION STATEMENT

Cerebral vasospasm (cVSP) consists of the vasoconstriction of large and small intracranial vessels which can lead to cerebral hypoperfusion, and in extreme cases, delayed ischemic deficits with stroke. While most commonly observed after aneurysmal subarachnoid hemorrhage (aSAH), cVSP can also occur after traumatic brain injury (TBI) as we have described in detail in this review. For the past decades, the research attention has focused on cVSP because of its association with delayed cerebral ischemia, which is the largest contributor of morbidity and mortality after aSAH. New discoveries in the cVSP pathophysiology involving multifactorial complex cascades and pathways pose new targets for therapeutic interventions in the prevention and treatment of cVSP. The goal of this review is to demonstrate the commonalities and differences in epidemiology and pathophysiology of both aSAH and TBI-associated cVSP, and highlight the more recently discovered pathways of cVSP. Finally, the latest cVSP surveillance methods and treatment options are illustrated.

Traumatic subarachnoid hemorrhage: our current understanding and its evolution over the past half century

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in the US, especially among the young. Primary injury in TBI is preventable, whereas secondary injury is treatable. As a result, considerable research efforts have been focused on elucidating the pathophysiology of secondary injury and determining various prognosticators in the hopes of improving final outcome by minimizing secondary injury. One such variable, traumatic subarachnoid hemorrhage (tSAH), has been the focus of many discussions over the past half century as numerous clinical studies have shown tSAH to be associated with adverse outcome. Whether the relationship of tSAH with poorer outcome in TBI is merely an epiphenomenon or a result of direct cause and effect is unclear. Some investigators believe that tSAH is merely a marker of severer TBI, while others argue that it directly causes deleterious effects such as vasospasm and ischemia. At the present time, no proven treatment regimen aimed specifically at decreasing the detrimental effects of tSAH exists, although calcium channel blockers traditionally thought to target vasospasm have shown some promises. Given that tSAH may primarily be an early indicator of associated and evolving brain injury, vigilant diagnostic surveillance including serial head CT and prevention of secondary brain damage owing to hypotension, hypoxia and intracranial hypertension may be more cost-effective than attempting to treat potential adverse sequelae associated with tSAH.

Cerebral vasospasm in traumatic brain injury

Vasospasm following traumatic brain injury (TBI) may dramatically affect the neurological and functional recovery of a vulnerable patient population. While the reported incidence of traumatic vasospasm ranges from 19%–68%, the true incidence remains unknown due to variability in protocols for its detection. Only 3.9%–16.6% of patients exhibit clinical deficits. Compared to vasospasm resulting from aneurysmal SAH (aSAH), the onset occurs earlier and the duration is shorter. Overall, the clinical course tends to be milder, although extreme cases may occur. Traumatic vasospasm can occur in the absence of subarachnoid hemorrhage. Surveillance transcranial Doppler ultrasonography (TCD) has been utilized to monitor for radiographic vasospasm following TBI. However, effective treatment modalities remain limited. Hypertension and hypervolemia, the mainstays of treatment of vasospasm associated with aSAH, must be used judiciously in TBI patients, and calcium-channel blockers have offered mixed clinical results. Currently, the paucity of large prospective cohort studies and level-one data limits the ability to form evidence-based recommendations regarding the diagnosis and management of vasospasm associated with TBI.

Risk factors for posttraumatic vasospasm

OBJECT

Posttraumatic vasospasm (PTV) is an underrecognized cause of ischemic damage after severe traumatic brain injury (TBI) that independently predicts poor outcome. There are, however, no guidelines for PTV screening and management, partly due to limited understanding of its pathogenesis and risk factors.

METHODS

A database review of 46 consecutive cases of severe TBI in pediatric and adult patients was conducted to identify risk factors for the development of PTV. Univariate analysis was performed to identify potential risk factors for PTV, which were subsequently analyzed using a multivariate logistic regression model to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Fever on admission was an independent risk factor for development of PTV (OR 22.2, 95% CI 1.9-256.8), and patients with hypothermia on admission did not develop clinically significant vasospasm during their hospital stay. The presence of small parenchymal contusions was also an independent risk factor for PTV (OR 7.8, 95% CI 0.9-69.5), whereas the presence of subarachnoid hemorrhage or other patterns of intracranial injury were not. Other variables, such as age, sex, ethnicity, degree of TBI severity, or admission laboratory values, were not independent predictors for the development of clinically significant PTV.

CONCLUSIONS

Independent risk factors for PTV include parenchymal contusions and fever. These results suggest that diffuse mechanical injury and activation of inflammatory pathways may be underlying mechanisms for the development of PTV, and that a subset of patients with these risk factors may be an appropriate population for aggressive screening. Further studies are needed to determine if treatments targeting fever and inflammation may be effective in reducing the incidence of vasospasm following severe TBI.

Initial predictive factors of outcome in severe non-accidental head trauma in children

OBJECT

The aim of this study is to evaluate the outcome of young children hospitalized for non-accidental head trauma in our PICU, to evaluate PRISM II score in this sub-population of pediatric trauma and to identify factors that might influence the short-term outcome.

MATERIALS AND METHODS

Files of all children less than 2 years old with the diagnosis of non-accidental head trauma over a 10-years period were systematically reviewed. We collected data on demographic information, medical history, clinical status, and management in the PICU. Three severity scores were then calculated: PRISM II, Glasgow Coma Scale (GCS), and Pediatric Trauma Score (PTS). Prognosis value of qualitative variables was tested with a univariate procedure analysis (anemia, diabetes insipidus...). Then, quantitative variables were tested with univariate procedure too (age, weight, PRISM II, GCS, Platelet count, fibrin, prothrombin time (PT)...). Potential association between variables and death was tested using univariate procedure. Variables identified by univariate analysis were then analyzed with multivariate analysis through a forward-stepping logistic regression.

RESULTS

Thirty-six children were included. Mean age was 5.5 months (8 days-21.5 months). Mortality rate was 27.8%. At admission, PTS, PRISM II, GCS, PT, PTT, and diabetes insipidus were significantly altered or more frequent in non survivors. Cutoff value for PRISM II at which risk of mortality increased was 17.5 (sensitivity = 0.8; specificity = 0.88).

CONCLUSION

PRISM II is a reliable and easy performing tool for assessing the prognosis of non-accidental cranial traumatism in young children. GCS and PTS, scores even simpler than PRISM II, showed good accuracy regarding survival prediction.

Time course for autoregulation recovery following severe traumatic brain injury

Object

The aim of the present study was to evaluate the time course for cerebral autoregulation (AR) recovery following severe traumatic brain injury (TBI)

Methods

Thirty-six patients (27 males and 9 females, mean ± SEM age 33 ± 15.1 years) with severe TBI underwent serial dynamic AR studies with leg cuff deflation as a stimulus, until recovery of the AR responses was measured.

Results

The AR was impaired (AR index < 2.8) in 30 (83%) of 36 patients on Days 3–5 after injury, and in 19 individuals (53%) impairments were found on Days 9–11 after the injury. Nine (25%) of 36 patients exhibited a poor AR response (AR index < 1) on postinjury Days 12–14, which eventually recovered on Days 15–23. Fifty-eight percent of the patients with a Glasgow Coma Scale score of 3–5, 50% of those with diffuse brain injury, 54% of those with elevated intracranial pressure, and 40% of those with poor outcome had no AR recovery in the first 11 days after injury.

Conclusions

Autoregulation recovery after severe TBI can be delayed, and failure to recover during the 2nd week after injury occurs mainly in patients with a lower Glasgow Coma Scale score, diffuse brain injury, elevated ICP, or unfavorable outcome. The finding suggests that perfusion pressure management should be considered in some of the patients for a period of at least 2 weeks.

Posttraumatic vasospasm detected by continuous brain tissue oxygen monitoring: treatment with intraarterial verapamil and balloon angioplasty

INTRODUCTION

Posttraumatic vasospasm (PTV) is a relatively common event following traumatic brain injury (TBI) that has been strongly correlated with worse neurological outcome in many studies. However, vasospasm continues to be an under-recognized source of secondary injury following TBI, and currently published guidelines do not address screening or management strategies for PTV. Brain tissue oxygen (P(bt)O(2)) monitoring probes allow for continuous screening for cerebral hypoxia following TBI, but their use as a monitor for PTV has not been previously described.

METHODS

Case report and literature review.

RESULTS

We present a case of PTV identified by persistent low P(bt)O(2) despite aggressive medical therapy. Computed tomography and digital subtraction angiography confirmed severe cerebral arterial vasospasm involving both anterior and posterior circulations. The patient was successfully treated with serial intraarterial therapy including balloon angioplasty and verapamil infusion.

CONCLUSION

Posttraumatic vasospasm should be included in the differential diagnosis of cerebral hypoxia (e.g., low P(bt)O(2)) following TBI. Management strategies for PTV may include early, aggressive intraarterial therapies including drug infusion and balloon angioplasty.

Multimodality monitoring in neurocritical care

Multimodality monitoring of cerebral physiology encompasses the application of different monitoring techniques and integration of several measured physiologic and biochemical variables into assessment of brain metabolism, structure, perfusion, and oxygenation status. Novel monitoring techniques include transcranial Doppler ultrasonography, neuroimaging, intracranial pressure, cerebral perfusion, and cerebral blood flow monitors, brain tissue oxygen tension monitoring, microdialysis, evoked potentials, and continuous electroencephalogram. Multimodality monitoring enables immediate detection and prevention of acute neurologic injury as well as appropriate intervention based on patients' individual disease states in the neurocritical care unit. Real-time analysis of cerebral physiologic, metabolic, and cardiovascular parameters simultaneously has broadened knowledge about complex brain pathophysiology and cerebral hemodynamics. Integration of this information allows for more precise diagnosis and optimization of management of patients with brain injury.

Effect of nimodipine on outcome in patients with traumatic subarachnoid haemorrhage: a systematic review

BACKGROUND

Despite several randomised controlled trials, there is still much debate whether nimodipine improves outcome in patients with traumatic subarachnoid haemorrhage. A 2003 Cochrane review reported improved outcome with nimodipine in these patients; however, because the results of Head Injury Trial (HIT) 4 were only partly presented there is still discussion whether patients with traumatic subarachnoid haemorrhage should be treated with this drug. Here, we present data from all head-injury trials, including previously unpublished results from HIT 4.

METHODS

We systematically searched PubMed and EMBASE databases using the following combinations of variables: "nimodipine" or "calcium antagonist" with "traumatic subarachnoid haemorrhage", "head injury", "head trauma", "brain injury", or "brain trauma". Bayer AG and all principal investigators or corresponding authors of the identified studies were contacted for additional information.

FINDINGS

Five manuscripts were identified, describing the results of four trials. We obtained additional data from HIT 1, 2, and 4. In total, 1074 patients with traumatic subarachnoid haemorrhage were included. The occurrence of poor outcome was similar in patients treated with nimodipine (39%) and those treated with placebo (40%); odds ratio was 0.88 (95% CI 0.51-1.54). Mortality rates did not differ between nimodipine (26%) and placebo (27%) treated patients (odds ratio 0.95; 95% CI 0.71-1.26).

INTERPRETATION

Our results do not lend support to the finding of a beneficial effect of nimodipine on outcome in patients with traumatic subarachnoid haemorrhage as reported in an earlier Cochrane review.

Trans-cranial Doppler in severe head injury: Evaluation of pattern of changes in cerebral blood flow velocity and its impact on outcome

BACKGROUND

Trans-cranial Doppler (TCD) studies after head injury have been done in the first 24 hours after injury and do not specify the exact interval between injury and time of recordings. We have studied cerebral blood flow changes in patients with severe head injury using serial TCD starting within 6 hours after trauma, and present our findings and its correlation with clinical outcome.

METHODS

Thirty-two patients with closed severe brain injuries formed the study group. Six-hourly serial TCD studies were done starting within 6 hours after trauma until 48 hours after trauma or death of the patient, whichever was earlier. Flow velocities of the extracranial internal carotid (V(EC-ICA)) and middle cerebral artery (V(MCA)) were recorded to identify vasospasm, hyperemia, or oligemia. Serial changes in flow velocities were correlated with the clinical outcome of the patients at 12 months' follow-up after injury.

RESULT

Oligemia (n = 30) and vasospasm (n = 2) were the earliest changes observed within 6 hours of trauma. In the oligemia group, persistent oligemia (n = 14), hyperemia (n = 6), normal flow velocity (n = 5), and vasospasm developing within 24 hours (n = 5) were observed. Eight patients developed vasospasm after 24 hours. All patients with persistent oligemia and vasospasm developing within 24 hours had poor outcome.

CONCLUSION

Oligemia is the most common change within 6 hours of head injury. Persistence of oligemia beyond 24 hours is associated with poor outcome. Early (within 24 hours posttrauma) onset of vasospasm is associated with poor outcome; however, delayed (>24 hours after trauma) vasospasm is not associated with poor outcome.

Cerebral autoregulation after hypothermic circulatory arrest in operations on the aortic arch

BACKGROUND

The purpose of this study was to determine whether patients who undergo thoracic aorta repairs with the aid of hypothermic circulatory arrest experience impairments in cerebral autoregulation, and to ascertain the influence of three different techniques of cerebral protection on autoregulatory function.

METHODS

Sixty-seven patients undergoing elective aortic arch procedures with hypothermic circulatory arrest were tested for cerebral dynamic autoregulation using continuous transcranial Doppler velocity and blood pressure recordings. Twenty-three patients were treated using hypothermic circulatory arrest without adjuncts (group 1), 25 using antegrade cerebral perfusion (group 2), and 19 using retrograde cerebral perfusion (group 3).

RESULTS

There were no hospital deaths. Two major strokes occurred in this series; 9 patients experienced temporary neurologic dysfunction: in all these patients severe impairment of cerebral autoregulation was observed. Cerebral autoregulation in the immediate postoperative period was preserved only in patients treated with antegrade cerebral perfusion. Severe impairments were observed in the other two groups in which the degree of autoregulatory response was inversely correlated to the duration of the cerebral protection time during hypothermic circulatory arrest. Postoperative improvement of autoregulatory function was observed in the majority of patients. Our data suggest the exposure to brain damage in the presence of autoregulation impairment, thus indicating that postoperative hypotensive phases may further contribute to neurologic impairment.

CONCLUSIONS

The status of cerebral autoregulation in the postoperative period after hypothermic circulatory arrest procedures is profoundly altered. The degree of impairment is influenced by the cerebral protection technique. This study indicates the beneficial role of antegrade perfusion during hypothermic circulatory arrest for the preservation of this function and suggests that postoperative cerebral autoregulation impairment can be regarded as an expression of central nervous system injury.

Quantitative assessment of cerebral autoregulation from transcranial Doppler pulsatility: a computer simulation study

Transcranial Doppler (TCD) ultrasonography is largely used today to achieve non-invasive assessment of cerebral autoregulation and cerebrovascular reactivity in neurosurgical patients. Recent experimental and clinical studies suggest that not only the pattern of mean velocity, but also velocity pulse amplitude alterations during changes in cerebral perfusion pressure (CPP) contain information on autoregulation status. The aim of this work is to investigate the relationship between cerebral autoregulation and TCD pulsatility by means of a comprehensive mathematical model of intracranial dynamics and cerebrovascular regulation. Simulation results, performed using different values of the most important clinical parameters of the model (autoregulation strength, cerebrospinal fluid (CSF) outflow resistance and intracranial elastance coefficient) show that velocity pulse amplitude increases with a reduction in CPP in patients with intact autoregulation, whereas changes in velocity pulsatility are modest in patients with weak autoregulation. Finally, velocity pulse amplitude decreases during a CPP reduction in patients with impaired autoregulation. Moreover, the relationship between the velocity pulse amplitude changes and autoregulation strength is almost linear in a wide range of CPP values, and is scarcely affected by changes in CSF circulation and intracranial elasticity. Starting from these results, we suggest a new quantitative index to assess autoregulation strength, i.e. G(aut)% = (s-b)/a, where G(aut)% is autoregulation strength (100% means intact autoregulation, 0% means impaired autoregulation), a approximately -0.03; b approximately 1.5 and s is the slope of the relationship ' percentage changes of velocity pulse amplitude to arterial pressure pulse amplitude vs. CPP changes'.

Online monitoring of cerebral hemodynamics during hemodialysis

BACKGROUND

Several factors, including anemia, diabetes, and hypertension, potentially could disturb the cerebral autoregulation mechanism in hemodialysis (HD) patients. This study examined the effect of hemodynamic and rheological changes on mean cerebral blood flow (CBF) velocity (MV) during HD.

METHODS

Continuous online monitoring of MV and pulsatility index in the middle cerebral artery were performed in 18 HD patients by transcranial Doppler ultrasound during the entire HD period (range, 3 to 4 hours). In addition, blood pressure, hematocrit (Hct), and relative decrease in blood volume were continuously monitored. Blood samples were obtained at the beginning and end of HD to measure hemorheological variables.

RESULTS

After HD, Hct increased significantly from 33.6% +/- 5.9% to 41.4% +/- 5.7% (P < 0.001). Blood and plasma viscosity increased significantly from 3.33 +/- 0.77 to 4.36 +/- 1.3 mPa.s (P < 0.001) and from 1.35 +/- 0.29 to 1.54 +/- 0.38 mPa.s (P < 0.001), respectively. The change in MV (DeltaMV) was not significantly different from zero and correlated significantly with change in Hct. During HD, mean arterial pressure (MAP) in 15 patients changed within the normal range (group I), whereas 3 patients developed hypotension (group II) and their MAP decreased from 99 +/- 5 to 60 +/- 8 mm Hg (P < 0.05). In both groups, DeltaMV were not significant.

CONCLUSION

Results of this study suggest that CBF does not appear to be diminished significantly during HD.

[Shaken baby syndrome: improvement of cerebral blood flow velocity after a subdural external derivation in a six-month old infant]

The shaken baby syndrome is a severe form of child abuse. The intracranial injuries are associated with a high morbidity and mortality rates. A 6 month-old healthy infant presented at home a cardiorespiratory arrest. After a cardiopulmonary resuscitation, radiological survey showed sub-dural haematomas and retinal haemorrhages, without a history of trauma. The diagnosis of shaken baby syndrome was made. Despite medical management and a fontanelle tap, clinical signs of intracranial hypertension worsened. Transcranial Doppler examination found the cerebral blood flow velocities to be decreased while the pulsatility index was increased. A sub-dural-external drainage allowed the cerebral blood flow to increase and the pulsatility index to decrease. We conclude that transcranial Doppler examination can be helpful for the clinician caring children presenting a shaken baby syndrome.

Multi-modal monitoring of acute brain injury

OBJECTIVE

To review the scientific basis for and utility of the traditional cerebral monitors used currently in neurointensive care, together with research techniques that are soon likely to become used in managing severe head injury and subarachnoid haemorrhage.

DESIGN AND CONTENT

Firstly, the pathophysiology of acute brain injury including cerebral haemodynamics, oxygen and metabolism and the role of secondary insults are discussed. Secondly, the importance of assessment of cerebrovascular autoregulation and reactivity is reviewed together with methods for its continuous non-invasive measurement using transcranial Doppler and intracranial pressure/arterial pressure recordings. Thirdly, the respective roles of jugular venous oxygen and brain tissue oxygen monitoring are analysed. Fourthly, the use of cerebral microdialysis is described, together with an overview of its utility.

CONCLUSION

Cerebral multimodal monitoring can be helpful for the optimal management of acute brain injury and essential for future exploratory trials of neuroprotective drugs.

Cerebral autoregulation following head injury

OBJECT

The goal of this study was to examine the relationship between cerebral autoregulation, intracranial pressure (ICP), arterial blood pressure (ABP), and cerebral perfusion pressure (CPP) after head injury by using transcranial Doppler (TCD) ultrasonography.

METHODS

Using ICP monitoring and TCD ultrasonography, the authors previously investigated whether the response of flow velocity (FV) in the middle cerebral artery to spontaneous variations in ABP or CPP provides reliable information about cerebral autoregulatory reserve. In the present study, this method was validated in 187 head-injured patients who were sedated and receiving mechanical ventilation. Waveforms of ICP, ABP, and FV were recorded over intervals lasting 20 to 120 minutes. Time-averaged mean FV and CPP were determined. The correlation coefficient index between FV and CPP (the mean index of autoregulation [Mx]) was calculated over 4-minute epochs and averaged for each investigation. The distribution of averaged mean FV values converged with the shape of the autoregulatory curve, indicating lower (CPP < 55 mm Hg) and upper (CPP > 105 mm Hg) thresholds of autoregulation. The relationship between the Mx and either the CPP or ABP was depicted as a U-shaped curve. Autoregulation was disturbed in the presence of intracranial hypertension (ICP > or = 25 mm Hg) and when mean ABP was too low (ABP < 75 mm Hg) or too high (ABP > 125 mm Hg). Disturbed autoregulation (p < 0.005) and higher ICP (p < 0.005) occurred more often in patients with unfavorable outcomes than in those with favorable outcomes.

CONCLUSIONS

Autoregulation not only is impaired when associated with a high ICP or low ABP, but it can also be disturbed by too high a CPP. The Mx can be used to guide intensive care therapy when CPP-oriented protocols are used.

Carbon dioxide reactivity, pressure autoregulation, and metabolic suppression reactivity after head injury: a transcranial Doppler study

OBJECT

Contemporary management of head-injured patients is based on assumptions about CO2 reactivity, pressure autoregulation (PA), and vascular reactivity to pharmacological metabolic suppression. In this study, serial assessments of vasoreactivity of the middle cerebral artery (MCA) were performed using bilateral transcranial Doppler (TCD) ultrasonography.

METHODS

Twenty-eight patients (mean age 33 +/- 13 years, median Glasgow Coma Scale score of 7) underwent a total of 61 testing sessions during postinjury Days 0 to 13. The CO2 reactivity (58 studies in 28 patients), PA (51 studies in 23 patients), and metabolic suppression reactivity (35 studies in 16 patients) were quantified for each cerebral hemisphere by measuring changes in MCA velocity in response to transient hyperventilation, arterial blood pressure elevation, or propofol-induced burst suppression, respectively. One or both hemispheres registered below normal vasoreactivity scores in 40%, 69%, and 97% of study sessions for CO2 reactivity, PA, and metabolic suppression reactivity (p < 0.0001), respectively. Intracranial hypertension, classified as intracranial pressure (ICP) greater than 20 mm Hg at the time of testing, was associated with global impairment of CO2 reactivity, PA, and metabolic suppression reactivity (p < 0.05). A low baseline cerebral perfusion pressure (CPP) was also predictive of impaired CO2 reactivity and PA (p < 0.01). Early postinjury hypotension or hypoxia was also associated with impaired CO2 reactivity (p < 0.05), and hemorrhagic brain lesions in or overlying the MCA territory were predictive of impaired metabolic suppression reactivity (p < 0.01). The 6-month Glasgow Outcome Scale score correlated with the overall degree of impaired vasoreactivity (p < 0.05).

CONCLUSIONS

During the first 2 weeks after moderate or severe head injury, CO2 reactivity remains relatively intact, PA is variably impaired, and metabolic suppression reactivity remains severely impaired. Elevated ICP appears to affect all three components of vasoreactivity that were tested, whereas other clinical factors such as CPP, hypotensive and hypoxic insults, and hemorrhagic brain lesions have distinctly different impacts on the state of vasoreactivity. Incorporation of TCD ultrasonography-derived vasoreactivity data may facilitate more injury- and time-specific therapies for head-injured patients.

Cerebral blood flow velocity and inflammatory response after severe traumatic brain injury

OBJECTIVES

The cerebral blood flow velocity (CBVF) was measured by transcranial Doppler sonography in patients with severe traumatic brain injury (TBI) in order to determine, whether it depends on the posttraumatic inflammatory response.

MATERIAL AND METHODS

CBVF in both middle cerebral arteries (MCA) was recorded in 25 comatous TBI patients (male 20; female five; mean age +/- standard deviation (S.D.), 41 +/- 20 years) and correlated to the levels of interleukine-(IL) 6, IL-8 and IL-10 in corresponding CSF/plasma samples, to PaCO2 and to intracranial (ICP), mean arterial (MAP) and cranial perfusion pressure (CPP).

RESULTS

CSF IL-6 and IL-8 were clearly higher than the corresponding plasma levels (mean CSF/plasma quotient for IL-6: 159 +/- 582; for IL-8: 143 +/- 311). CBVF did not show large side-to-side differences at each examination indicating that CBFV in both MCAs was determined mostly by systemic conditions and not by severe regional abnormalities. Since all other evaluated variables including interleukines represent also systemic conditions we used the mean value (MCBFV) of both CBFVs for analysis. By stepwise regression analysis between MCBVF (mean +/- S.D., 80 +/- 26 cm/s) and the variables PaCO2 (33 +/- 4 mmHg), MAP (86 +/- 12 mmHg), ICP (20 +/- 11 mmHg), CPP (70 +/- 14 mmHg) and CSF or plasma IL-6, IL-8 and IL-10, it turned out that MCBFV correlated significantly with PaCO2 (r = 0.478; P < 0.01) and CSF IL-8 (r = -0.361; P < 0.05).

CONCLUSIONS

When CPP is adequate for brain perfusion, CBFV in large brain supplying arteries depends predominantly on PaCO2 and shows only a slight association to intrathecal IL-8 levels. For clinical interpretation of CBFV data, the inflammatory response seems to be of minor relevance.

Cerebral autoregulation testing after aneurysmal subarachnoid hemorrhage: the phase relationship between arterial blood pressure and cerebral blood flow velocity

OBJECTIVE

Impairment of cerebral autoregulation (CA) appears to be an important cause for secondary ischemia after subarachnoid hemorrhage (SAH). It has been shown that graded CA impairment is predictive of outcome. Little is known about whether such impairment is present, what causes CA impairment, whether it precedes vasospasm, and whether it is predictive of outcome in patients with severe aneurysmal SAH.

DESIGN

Prospective, controlled study.

SETTING

Neurosurgical intensive care unit.

PATIENTS

Twelve patients after aneurysmal subarachnoid hemorrhage, 40 controls.

INTERVENTIONS

Recording of cerebral blood flow velocities and continuous measurement of arterial blood pressure at a controlled ventilatory frequency of six per minute to standardize the influence of intrathoracic pressure changes on blood pressure.

MEASUREMENTS AND MAIN RESULTS

We calculated the phase shift angles (deltaphidegrees) between slow (0.1 Hz) arterial blood pressure and cerebral blood flow velocity waves measured by transcranial Doppler ultrasound in the middle cerebral artery during a) posthemorrhage days (PHD) 1-6 (early or prevasospasm phase), and b) during PHD 7-13 (late or vasospasm phase) using a 6/min ventilation protocol, and in 40 controls spontaneously ventilating at the same rate. deltaphi <30 degrees indicated lost CA. Mean flow velocities >100 cm/sec were considered vasospasm. We combined early and late measurements to assess the CA relationship with low cerebral perfusion pressure (CPP) and/or vasospasm. We assessed the Glasgow Outcome Scale (GOS) score at discharge (1 = worst, 5 = best). The admission Hunt and Hess score was 3.6 +/- 0.7. GOS scores were n = 3 (GOS 1), n = 2 (GOS 2), n = 5 (GOS 3), n = 1 (GOS 4), and n = 1 (GOS 5). In the early phase, deltaphi was 40.4 +/- 19.8 degrees (left), and 40.4 +/- 19.2 degrees (right). CPP was 69.4 +/- 10.9, intracranial pressure (ICP) was 6.7 +/- 2.8 mm Hg. In the late phase, deltaphi worsened in six patients and none improved: 32.1 +/- 21 degrees (left), and 26.9 +/- 17.2 degrees (right); CPP was 68.1 +/- 12.1, ICP was 7.5 +/- 3.7 mm Hg. CA was significantly impaired in both phases when compared with normal subjects (deltaphi: 65.7 +/- 24.5 degrees; p < .01 for early, p < .001 for late phase). In the early phase, seven of eight patients in whom autoregulation was intact had a GOS >2 at discharge and disturbed CA on at least one side was predictive of either vegetative condition at discharge or death (p < .01). In the late phase, deltaphi was no longer predictive of outcome. Spasm was present in 8 of 17 vessels (47%) in which CA was lost; no spasm was found in 25 of 28 vessels (89%) in which CA was intact (p < .01). A low CPP was present in 6 of 17 vessels (35%) in which CA was lost; a normal CPP was found in 21 of 27 vessels (78%) in which CA was intact (p > .05, NS). However, 14 of 17 vessels (82%) with lost CA showed spasm and/or low CPP while only 8 of 27 cases (30%) with intact CA had either spasm or low CPP (p < .001).

CONCLUSIONS

CA can be assessed in a graded fashion in SAH patients. CA impairment precedes vasospasm; ongoing vasospasm worsens CA. CA assessment early after subarachnoid hemorrhage, within PHD 1-6, is predictive of outcome whereas late assessment is not. CA impairment is associated with cerebral vasospasm and low CPP.

Does traumatic subarachnoid hemorrhage caused by diffuse brain injury cause delayed ischemic brain damage? Comparison with subarachnoid hemorrhage caused by ruptured intracranial aneurysms

OBJECTIVE

To examine whether traumatic subarachnoid hemorrhage (TSAH) caused by severe diffuse brain injury leads to delayed ischemic brain damage and secondary deterioration of outcome, as does aneurysmal subarachnoid hemorrhage (ASAH).

METHODS

We examined 99 patients with diffuse brain injury with TSAH and 114 patients with ASAH. Computed tomographic (CT) findings, cerebral blood flow, and neurological outcomes were assessed during the acute and subacute phases and were compared between the two groups.

RESULTS

The distribution of subarachnoid hemorrhage on the CT scans differed between the two groups. Unlike ASAH, TSAH was not limited to cisterns surrounding the circle of Willis but extended to supratentorial regions and interhemispheric fissures. Computed tomography-detected subarachnoid hemorrhage disappeared very early with TSAH and gradually with ASAH. In the ASAH group, mean cerebral blood flow decreased to 75% of normal during the acute phase and decreased a further 10% during the subacute phase. In the TSAH group, mean cerebral blood flow decreased to 85% of normal during the acute phase and increased slightly during the subacute phase. Neurological deterioration and in-hospital death peaked on Day 0 in association with TSAH and showed twin peaks in association with ASAH. The incidence of low-density areas on the CT scans was significantly higher with ASAH than with TSAH. All low-density areas on the CT scans of patients with ASAH corresponded to vascular territories, but low-density areas on the CT scans of patients with TSAH were rarely associated with vascular territories and contained deep-seated or gliding contusion types.

CONCLUSION

The findings suggest that the incidence of vasospasm is low in association with TSAH and that the cause is different compared with ASAH. There is no evidence that the presence of TSAH in cases of diffuse brain injury leads to delayed ischemic brain damage and secondary deterioration of outcome.

Early changes in middle cerebral artery blood flow velocity after head injury

OBJECT

This study was designed to investigate the incidence of early abnormalities in the cerebral circulation after head injury by relating the results of the initial computerized tomography (CT) scan with transcranial Doppler (TCD) ultrasound readings to see if the side of injury and the outcome can be predicted by using these modalities.

METHODS

Transcranial Doppler ultrasound measurements were obtained in the emergency room in 22 head-injured patients less than 3 hours after injury. The middle cerebral artery (MCA) was insonated using a standard technique. The TCD measurements in each MCA were examined individually; of 39 measurements, 22 (56%) showed a low mean blood flow velocity, 27 (69%) demonstrated a high pulsatility index (PI), and 18 (46%) showed both abnormalities. The side of the cerebrovascular abnormality measured by TCD ultrasound did not appear to be an accurate predictor of the side of the injury as determined on the initial CT scan. Of 13 patients in whom either a space-occupying hematoma or signs of swelling were shown on the initial CT scan, 10 (77%) had an increased PI in one or both MCAs, which is an indication of high flow resistance.

CONCLUSIONS

Transcranial Doppler ultrasound examinations performed while patients are in the emergency room may have a role in determining treatment priorities, especially in those with multiple injuries.

Relationships among cerebral perfusion pressure, autoregulation, and transcranial Doppler waveform: a modeling study

OBJECT

The aim of this study was to analyze how the main values extrapolated from the transcranial Doppler (TCD) waveform (systolic, mean, and diastolic velocity; velocity peak-to-peak amplitude; and pulsatility index [PI]) are affected by changes in intracranial pressure (ICP), systemic arterial pressure (SAP), autoregulation, and intracranial compliance.

METHODS

The analysis was performed using a mathematical model of the intracranial dynamics. This model includes a passive middle cerebral artery, the biomechanics of large and small pial arteries subjected to autoregulatory mechanisms, a collapsing venous cerebrovascular bed, the cerebrospinal fluid circulation, and the ICP-volume relationship. The results indicate that there are approximately three distinct zones characterized by different relationships between cerebral perfusion pressure (CPP) and velocity parameters in patients with preserved autoregulation. In the central autoregulatory zone (CPP > 70 mm Hg) the mean velocity does not change with decreasing CPP, whereas the PI and velocity peak-to-peak amplitude increase moderately. In a second zone (CPP between 4045 and 70 mm Hg), in which vasodilation of small pial arteries becomes maximal, the mean velocity starts to decrease, whereas the PI and velocity amplitude continue to increase. In the third zone, in which autoregulation is completely exhausted (CPP < 40 mm Hg), arterioles behave passively, mean velocity and velocity amplitude decline abruptly, and the PI exhibits a disproportionate rise. Moreover, this rise is quite independent of whether CPP is reduced by increasing ICP or reducing mean SAP. In contrast, in patients with defective autoregulation, the mean velocity and velocity amplitude decrease linearly with decreasing CPP, but the PI still increases in a way similar to that observed in patients with preserved autoregulation.

CONCLUSIONS

The information contained in the TCD waveform is affected by many factors, including ICP, SAP, autoregulation. and intracranial compliance. Model results indicate that only a comparative analysis of the concomitant changes in ultrasonographic quantities during multimodality monitoring may permit the assessment of several aspects of intracranial dynamics (cerebral blood flow changes, vascular pulsatility, ICP changes, intracranial compliance, CPP, and autoregulation).

Hemodynamically significant cerebral vasospasm and outcome after head injury: a prospective study

The authors prospectively investigated cerebral hemodynamic changes in 152 patients with head injuries to clarify the relationship between cerebral vasospasm and outcome. They also sought to determine the most clinically meaningful criteria for diagnosing cerebral vasospasm. Patients with varying degrees of moderate-to-severe head injury were monitored using transcranial Doppler (TCD) ultrasonography and intravenous 133Xe-cerebral blood flow (CBF) measurements. Outcome was determined at 6 months. Using TCD ultrasonography, mean flow velocities were determined for the middle cerebral artery (V(MCA), 149 patients) and basilar artery (V(BA), 126 patients). Recordings of the mean extracranial internal carotid artery velocity (V(EC-ICA)) were also performed to determine the hemispheric ratio (V(MCA)/V(EC-ICA), 147 patients). Cerebral blood flow measurements were obtained in 91 patients. Concurrent TCD and CBF data from 85 patients were used to calculate a "spasm index" (the V(MCA) or V(BA), respectively, divided by the hemispheric or global CBF). The authors investigated the clinical significance of elevated flow velocity, hemispheric ratio, and spasm index. Patients diagnosed as having MCA or BA vasospasm on the basis of TCD-derived criteria alone had a significantly worse outcome than patients without vasospasm. When CBF was considered, hemodynamically significant vasospasm, as defined by an elevated spasm index, was even more strongly associated with poor outcome. Stepwise logistic regression analysis confirmed that hemodynamically significant vasospasm was a significant predictor of poor outcome, independent of the effects of admission Glasgow Coma Scale score and age. On the basis of the results of this study, the authors suggest that the important factor impacting on outcome is not vasospasm per se, but hemodynamically significant vasospasm with low CBF. These findings show that vasospasm is a pathophysiologically important posttraumatic secondary insult, which is best diagnosed by the combined use of TCD and CBF measurements.

[Severe trauma in children]

Trauma are responsible for approximately 50% of the deaths of the pediatric population between 1-15 years of age. This high mortality rate, associated with frequent sequelae, leading sometimes to severe handicaps, is a major problem of public health in the developed countries. Pediatric trauma have some particularities, due to anatomical and physiological differences, and to specific injury mechanisms. Management of a patient with severe trauma is best performed by trained physicians, working in a multidisciplinary team with a two steps approach: 1) emergency rapid clinical assessment and resuscitation. 2) a secondary complete clinical evaluation associated with medical imaging, mainly based on CT scan. Head injuries are frequent and represent the main prognosis factor, mass lesions being less frequent and cerebral oedema more frequent in children, than in adult; brain swelling appears to be less frequent than initially reported. Management of head trauma has evolved in recent years, and is now largely directed towards the prevention of secondary ischemic brain injury: new monitoring devices are proposed to pursue that goal: transcranial doppler and continuous jugular vein oxygen saturation monitoring. Spinal cord injuries are rare but may be severe: cervical and spinal cord injuries without radiological abnormality (SC/WORA) appear to be more frequent than in adult. Most often, abdominal plain viscera injuries are treated with a conservative non operative approach. Among chest injuries, pulmonary contusion is the most frequent, with a favorable outcome in most cases within 3-4 days. Child abuse must be suspected in any case where there is no clear injury mechanism or when there is a discrepancy between the severity of the injury and the alleged mechanism.

Transcranial Doppler ultrasonography in the neurocritical care unit

TCD ultrasonography is a noninvasive means to study the cerebral vasculature. By varying the depth and angle of insonation of a pulsed sound wave, the direction and velocity profile of the cerebral arteries can be ascertained. This can be used to identify areas of focal stenosis and increased resistance and to estimate the adequacy of cerebral flow. TCD ultrasonography commonly is used in SAH to detect cerebral vasospasm. Many centers interpret rising velocities as increasing vessel narrowing and initiate medical strategies based on these values. TCD use in head trauma is less clearly defined. TCD ultrasonography is considered an acceptable confirmatory test for the determination of brain death. TCD ultrasonography is capable of studying dynamic cerebrovascular processes. By being able to determine vessel patency, TCD may become a useful adjuvant to thrombolytic therapy. Continuous monitoring of flow velocities and profiles along with testing to cerebrovascular reserve promises to be a future active area of research.

Traumatic subarachnoid hemorrhage and its treatment with nimodipine. German tSAH Study Group

A prospective, randomized, double-blind, placebo-controlled study of nimodipine used to treat traumatic subarachnoid hemorrhage (tSAH) was conducted in 21 German neurosurgical centers between January 1994 and April 1995. One hundred twenty-three patients with tSAH appearing on initial computerized tomography (CT) scanning were entered into the study. Requirements for inclusion included age between 16 and 70 and admission into the study within 12 hours after head injury, regardless of the patient's level of consciousness. Eligible patients received either a sequential course of intravenous and oral nimodipine or placebo treatment for 3 weeks. Patients were closely monitored using clinical neurology, computerized tomography, laboratory, and transcranial Doppler ultrasound parameters. Patients treated with nimodipine had a significantly less unfavorable outcome (death, vegetative survival, or severe disability) at 6 months than placebo-treated patients (25% vs. 46%, p = 0.02). The relative reduction in unfavorable outcome in the nimodipine-treated group was even higher (55%, p = 0.002) when only patients who complied with the protocol were considered.

Elevated transcranial Doppler flow velocities after severe head injury: cerebral vasospasm or hyperemia?

Sixty-seven patients (45 males and 22 females) aged 2 to 70 years (mean 36 years) who had suffered closed head injury were investigated with daily transcranial Doppler (TCD) recordings. A total of 470 TCD recordings (mean 7) were made during Days 1 to 14 after admission. Blood flow velocities were determined in the middle cerebral artery (MCA) and the extracranial internal carotid artery (ICA). Twenty-seven (40%) of the 67 patients demonstrated traumatic subarachnoid hemorrhage (tSAH) on the first computerized tomography (CT) scan after the injury. Flow velocities exceeded 100 cm/second in 22 patients. Eleven (41%) of the 27 patients who showed tSAH on the first CT scan developed velocities greater than 100 cm/second, as compared to 11 (28%) of 40 patients without tSAH on CT. Two patients in whom a thick layer of tSAH was revealed on the first CT scan had MCA flow velocities exceeding 200 cm/second for several days. Measurements of cerebral blood flow (CBF) with single-photon emission CT (SPECT) were performed in six tSAH patients who showed TCD flow velocities exceeding 120 cm/second (uni- or bilaterally) to determine whether the increase in velocity reflected vasospasm or hyperemia. The SPECT studies verified ischemia in five patients but revealed general hyperemia in one. The bilateral increase in MCA flow velocities in the latter case was due to high-volume flow through the MCA secondary to elevated CBF rather than arterial narrowing. In one patient with a thick layer of subarachnoid blood on a CT scan obtained at admission, MCA flow velocities exceeded 220 cm/second bilaterally on Day 8 after the head injury. A SPECT measurement obtained on the same day reflected bilateral ischemia. In this patient flow velocities decreased, with a corresponding normalization of CBF, after 5 days of intravenous nimodipine administration. The MCA/ICA ratio correlated well with the distribution of CBF in the six patients studied using SPECT. This report suggests that vasospasm is an important secondary posttraumatic insult in patients suffering severe head injury and, in some cases, is probably treatable by administration of intravenous calcium channel blockers.

Traumatic subarachnoid hemorrhage as a predictable indicator of delayed ischemic symptoms

This report provides findings of an investigation of the influence of traumatic subarachnoid hemorrhage on the development of delayed cerebral ischemia caused by vasospasm. The authors prospectively studied 130 patients with closed-head trauma, who exhibited subarachnoid blood on admission computerized tomography (CT) scans. Ten (7.7%) of these patients developed delayed ischemic symptoms between Days 4 and 16 after the head injury. They consisted of three (3.0%) of 101 patients with small amounts of subarachnoid blood and seven (24.1%) of 29 patients with massive quantities of subarachnoid blood on admission CT scans. In each of the 10 patients, severe vasospasm was demonstrated by angiography performed soon after development of ischemic symptoms. There was a close correlation between the main site of the subarachnoid blood and the location of severe vasospasm. In seven of the patients, follow-up CT scans showed development of focal ischemic areas in the cerebral territories corresponding to the vasospastic arteries. These results demonstrate that traumatic subarachnoid hemorrhage, especially if massive, is a predictable indicator of delayed ischemic symptoms.