The effects of cerebral pressure autoregulation status and CPP levels on cerebral metabolism in pediatric traumatic brain injury

BACKGROUND

Cerebral perfusion pressure (CPP) management in the developing child with traumatic brain injury (TBI) is challenging. The pressure reactivity index (PRx) may serve as marker of cerebral pressure autoregulation (CPA) and optimal CPP (CPPopt) may be assessed by identifying the CPP level with best (lowest) PRx. To evaluate the potential of CPPopt guided management in children with severe TBI, cerebral microdialysis (CMD) monitoring levels of lactate and the lactate/pyruvate ratio (LPR) (indicators of ischemia) were related to actual CPP levels, autoregulatory state (PRx) and deviations from CPPopt (ΔCPPopt).

METHODS

Retrospective study of 21 children ≤ 17 years with severe TBI who had both ICP and CMD monitoring were included. CPP, PRx, CPPopt and ΔCPPopt where calculated, dichotomized and compared with CMD lactate and lactate-pyruvate ratio.

RESULTS

Median age was 16 years (range 8-17) and median Glasgow coma scale motor score 5 (range 2-5). Both lactate (p = 0.010) and LPR (p =  < 0.001) were higher when CPP ≥ 70 mmHg than when CPP < 70. When PRx ≥ 0.1 both lactate and LPR were higher than when PRx < 0.1 (p =  < 0.001). LPR was lower (p = 0.012) when CPPopt ≥ 70 mmHg than when CPPopt < 70, but there were no differences in lactate levels. When ΔCPPopt > 10 both lactate (p = 0.026) and LPR (p = 0.002) were higher than when ΔCPPopt < -10.

CONCLUSIONS

Increased levels of CMD lactate and LPR in children with severe TBI appears to be related to disturbed CPA (PRx). Increased lactate and LPR also seems to be associated with actual CPP levels ≥ 70 mmHg. However, higher lactate and LPR values were also seen when actual CPP was above CPPopt. Higher CPP appears harmful when CPP is above the upper limit of pressure autoregulation. The findings indicate that CPPopt guided CPP management may have potential in pediatric TBI.

Decompressive craniectomy as a second/third-tier intervention in traumatic brain injury: A multicenter observational study

OBJECTIVES

RESCUEicp studied decompressive craniectomy (DC) applied as third-tier option in severe traumatic brain injury (TBI) patients in a randomized controlled setting and demonstrated a decrease in mortality with similar rates of favorable outcome in the DC group compared to the medical management group. In many centers, DC is being used in combination with other second/third-tier therapies. The aim of the present study is to investigate outcomes from DC in a prospective non-RCT context.

METHODS

This is a prospective observational study of 2 patient cohorts: one from the University Hospitals Leuven (2008-2016) and one from the Brain-IT study, a European multicenter database (2003-2005). In thirty-seven patients with refractory elevated intracranial pressure who underwent DC as a second/third-tier intervention, patient, injury and management variables including physiological monitoring data and administration of thiopental were analysed, as well as Extended Glasgow Outcome score (GOSE) at 6 months.

RESULTS

In the current cohorts, patients were older than in the surgical RESCUEicp cohort (mean 39.6 vs. 32.3; p < 0.001), had higher Glasgow Motor Score on admission (GMS < 3 in 24.3% vs. 53.0%; p = 0.003) and 37.8% received thiopental (vs. 9.4%; p < 0.001). Other variables were not significantly different. GOSE distribution was: death 24.3%; vegetative 2.7%; lower severe disability 10.8%; upper severe disability 13.5%; lower moderate disability 5.4%; upper moderate disability 2.7%, lower good recovery 35.1%; and upper good recovery 5.4%. The outcome was unfavorable in 51.4% and favorable in 48.6%, as opposed to 72.6% and 27.4% respectively in RESCUEicp (p = 0.02).

CONCLUSION

Outcomes in DC patients from two prospective cohorts reflecting everyday practice were better than in RESCUEicp surgical patients. Mortality was similar, but fewer patients remained vegetative or severely disabled and more patients had a good recovery. Although patients were older and injury severity was lower, a potential partial explanation may be in the pragmatic use of DC in combination with other second/third-tier therapies in real-life cohorts. The findings underscore that DC maintains an important role in managing severe TBI.

Intracranial pressure elevations in diffuse axonal injury: association with nonhemorrhagic MR lesions in central mesencephalic structures

OBJECTIVE

Increased intracranial pressure (ICP) in patients with severe traumatic brain injury (TBI) with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in patients with DAI.

METHODS

Fifty-two patients with severe TBI (median age 24 years, range 9-61 years), who had undergone ICP monitoring and had DAI on MRI, as determined using T2*-weighted gradient echo, susceptibility-weighted imaging, and diffusion-weighted imaging (DWI) sequences, were enrolled. The proportion of good monitoring time (GMT) with ICP > 20 mm Hg during the first 120 hours postinjury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression.

RESULTS

All patients had episodes of ICP > 20 mm Hg. The mean proportion of GMT with ICP > 20 mm Hg was 5%, and 27% of the patients (14/52) spent more than 5% of GMT with ICP > 20 mm Hg. The Glasgow Coma Scale motor score at admission (p = 0.04) and lesions on DWI sequences in the substantia nigra and mesencephalic tegmentum (SN-T, p = 0.001) were associated with the proportion of GMT with ICP > 20 mm Hg. In multivariable linear regression, lesions on DWI sequences in SN-T (8% of GMT with ICP > 20 mm Hg, 95% CI 3%-13%, p = 0.004) and young age (-0.2% of GMT with ICP > 20 mm Hg, 95% CI -0.07% to -0.3%, p = 0.002) were associated with increased ICP.

CONCLUSIONS

Increased ICP occurs in approximately one-third of patients with severe TBI who have DAI. Age and lesions on DWI sequences in the central mesencephalon (i.e., SN-T) are associated with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in patients with DAI.

Decompressive craniectomy in traumatic brain injury: usage and clinical outcome in a single centre

BACKGROUND

Two randomised controlled trials (RCTs) of decompressive craniectomy (DC) in traumatic brain injury (TBI) have shown poor outcome, but there are considerations of how these protocols relate to real practice. The aims of this study were to evaluate usage and outcome of DC and thiopental in a single centre.

METHOD

The study included all TBI patients treated at the neurointensive care unit, Akademiska sjukhuset, Uppsala, Sweden, between 2008 and 2014. Of 609 patients aged 16 years or older, 35 treated with DC and 23 treated with thiopental only were studied in particular. Background variables, intracranial pressure (ICP) measures and global outcome were analysed.

RESULTS

Of 35 DC patients, 9 were treated stepwise with thiopental before DC, 9 were treated stepwise with no thiopental before DC and 17 were treated primarily with DC. Six patients received thiopental after DC. For 23 patients, no DC was needed after thiopental. Eighty-eight percent of our DC patients would have qualified for the DECRA study and 38% for the Rescue-ICP trial. Favourable outcome was 44% in patients treated with thiopental before DC, 56% in patients treated with DC without prior thiopental, 29% in patients treated primarily with DC and 52% in patients treated with thiopental with no DC.

CONCLUSIONS

The place for DC in TBI management must be evaluated better, and we believe it is important that future RCTs should have clearer and less permissive ICP criteria regarding when thiopental should be followed by DC and DC followed by thiopental.

Bedside Xenon-CT Shows Lower CBF in SAH Patients with Impaired CBF Pressure Autoregulation as Defined by Pressure Reactivity Index (PRx)

BACKGROUND

Subarachnoid hemorrhage (SAH) is a disease with a high rate of unfavorable outcome, often related to delayed cerebral ischemia (DCI), i.e., ischemic injury that develops days-weeks after onset, with a multifactorial etiology. Disturbances in cerebral pressure autoregulation, the ability to maintain a steady cerebral blood flow (CBF), despite fluctuations in systemic blood pressure, have been suggested to play a role in the development of DCI. Pressure reactivity index (PRx) is a well-established measure of cerebral pressure autoregulation that has been used to study traumatic brain injury, but not extensively in SAH.

OBJECTIVE

To study the relation between PRx and CBF in SAH patients, and to examine if PRx can be used to predict DCI.

METHODS

Retrospective analysis of prospectively collected data. PRx was calculated as the correlation coefficient between mean arterial blood pressure (MABP) and intracranial pressure (ICP) in a 5 min moving window. CBF was measured using bedside Xenon-CT (Xe-CT). DCI was diagnosed clinically.

RESULTS

47 poor-grade mechanically ventilated patients were studied. Patients with disturbed pressure autoregulation (high PRx values) had lower CBF, as measured by bedside Xe-CT; both in the early (day 0-3) and late (day 4-14) acute phase of the disease. PRx did not differ significantly between patients who developed DCI or not.

CONCLUSION

In mechanically ventilated and sedated SAH patients, high PRx (more disturbed CBF pressure autoregulation) is associated with low CBF, both day 0-3 and day 4-14 after onset. The role of PRx as a monitoring tool in SAH patients needs further studying.

The influence of hyperthermia on intracranial pressure, cerebral oximetry and cerebral metabolism in traumatic brain injury

BACKGROUND

Hyperthermia is a common secondary insult in traumatic brain injury (TBI). The aim was to evaluate the relationship between hyperthermia and intracranial pressure (ICP), and if intracranial compliance and cerebral blood flow (CBF) pressure autoregulation affected that relationship. The relationships between hyperthermia and cerebral oximetry (B_tipO₂) and cerebral metabolism were also studied.

METHODS

A computerized multimodality monitoring system was used for data collection at the neurointensive care unit. Demographic and monitoring data (temperature, ICP, blood pressure, microdialysis, B_tipO₂) were analyzed from 87 consecutive TBI patients. ICP amplitude was used as measure of compliance, and CBF pressure autoregulation status was calculated using collected blood pressure and ICP values. Mixed models and comparison between groups were used.

RESULTS

The influence of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and B_tipO₂) was small, but individual differences were seen. Linear mixed models showed that hyperthermia raises ICP slightly more when temperature increases in the groups with low compliance and impaired CBF pressure autoregulation. There was also a tendency (not statistically significant) for increased B_tipO₂, and for increased pyruvate and lactate, with higher temperature, while the lactate/pyruvate ratio and glucose were stable.

CONCLUSIONS

The major finding was that the effects of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and B_tipO₂) were not extensive in general, but there were exceptional cases. Hyperthermia treatment has many side effects, so it is desirable to identify cases in which hyperthermia is dangerous. Information from multimodality monitoring may be used to guide treatment in individual patients.

Increased risk of critical CBF levels in SAH patients with actual CPP below calculated optimal CPP

Background

Cerebral pressure autoregulation can be quantified with the pressure reactivity index (PRx), based on the correlation between blood pressure and intracranial pressure. Using PRx optimal cerebral perfusion pressure (CPPopt) can be calculated, i.e., the level of CPP where autoregulation functions best. The relation between cerebral blood flow (CBF) and CPPopt has not been examined. The objective was to assess to which extent CPPopt can be calculated in SAH patients and to investigate CPPopt in relation to CBF.

Methods

Retrospective study of prospectively collected data. CBF was measured bedside with Xenon-enhanced CT (Xe-CT). The difference between actual CPP and CPPopt was calculated (CPP∆). Correlations between CPP∆ and CBF parameters were calculated with Spearman’s rank order correlation coefficient (rho). Separate calculations were done using all patients (day 0–14 after onset) as well as in two subgroups (day 0–3 and day 4–14).

Results

Eighty-two patients with 145 Xe-CT scans were studied. Automated calculation of CPPopt was possible in adjunct to 60% of the Xe-CT scans. Actual CPP < CPPopt was associated with higher numbers of low-flow regions (CBF <10 ml/100 g/min) in both the early phase (day 0–3, n = 39, Spearman’s rho = −0.38, p = 0.02) and late acute phase of the disease (day 4–14, n = 35, Spearman’s rho = −0.39, p = 0.02). CPP level per se was not associated with CBF.

Conclusions

Calculation of CPPopt is possible in a majority of patients with severe SAH. Actual CPP below CPPopt is associated with low CBF.

Extended Anatomical Grading in Diffuse Axonal Injury Using MRI: Hemorrhagic Lesions in the Substantia Nigra and Mesencephalic Tegmentum Indicate Poor Long-Term Outcome

Clinical outcome after traumatic diffuse axonal injury (DAI) is difficult to predict. In this study, three magnetic resonance imaging (MRI) sequences were used to quantify the anatomical distribution of lesions, to grade DAI according to the Adams grading system, and to evaluate the value of lesion localization in combination with clinical prognostic factors to improve outcome prediction. Thirty patients (mean 31.2 years ±14.3 standard deviation) with severe DAI (Glasgow Motor Score [GMS] <6) examined with MRI within 1 week post-injury were included. Diffusion-weighted (DW), T2*-weighted gradient echo and susceptibility-weighted (SWI) sequences were used. Extended Glasgow outcome score was assessed after 6 months. Number of DW lesions in the thalamus, basal ganglia, and internal capsule and number of SWI lesions in the mesencephalon correlated significantly with outcome in univariate analysis. Age, GMS at admission, GMS at discharge, and low proportion of good monitoring time with cerebral perfusion pressure <60 mm Hg correlated significantly with outcome in univariate analysis. Multivariate analysis revealed an independent relation with poor outcome for age (p = 0.005) and lesions in the mesencephalic region corresponding to substantia nigra and tegmentum on SWI (p = 0.008). We conclude that higher age and lesions in substantia nigra and mesencephalic tegmentum indicate poor long-term outcome in DAI. We propose an extended MRI classification system based on four stages (stage I—hemispheric lesions, stage II—corpus callosum lesions, stage III—brainstem lesions, and stage IV—substantia nigra or mesencephalic tegmentum lesions); all are subdivided by age (≥/<30 years).

Brain tissue oxygenation and cerebral metabolic patterns in focal and diffuse traumatic brain injury

INTRODUCTION

Neurointensive care of traumatic brain injury (TBI) patients is currently based on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) targeted protocols. There are reasons to believe that knowledge of brain tissue oxygenation (BtipO2) would add information with the potential of improving patient outcome. The aim of this study was to examine BtipO2 and cerebral metabolism using the Neurovent-PTO probe and cerebral microdialysis (MD) in TBI patients.

METHODS

Twenty-three severe TBI patients with monitoring of physiological parameters, ICP, CPP, BtipO2, and MD for biomarkers of energy metabolism (glucose, lactate, and pyruvate) and cellular distress (glutamate, glycerol) were included. Patients were grouped according to injury type (focal/diffuse) and placement of the Neurovent-PTO probe and MD catheter (injured/non-injured hemisphere).

RESULTS

We observed different patterns in BtipO2 and MD biomarkers in diffuse and focal injury where placement of the probe also influenced the results (ipsilateral/contralateral). In all groups, despite fairly normal levels of ICP and CPP, increased MD levels of glutamate, glycerol, or the L/P ratio were observed at BtipO2 <5 mmHg, indicating increased vulnerability of the brain at this level.

CONCLUSION

Monitoring of BtipO2 adds important information in addition to traditional ICP and CPP surveillance. Because of the different metabolic responses to very low BtipO2 in the individual patient groups we submit that brain tissue oximetry is a complementary tool rather than an alternative to MD monitoring.

An optimal frequency range for assessing the pressure reactivity index in patients with traumatic brain injury

The objective of this study was to identify the optimal frequency range for computing the pressure reactivity index (PRx). PRx is a clinical method for assessing cerebral pressure autoregulation based on the correlation of spontaneous variations of arterial blood pressure (ABP) and intracranial pressure (ICP). Our hypothesis was that optimizing the methodology for computing PRx in this way could produce a more stable, reliable and clinically useful index of autoregulation status. The patients studied were a series of 131 traumatic brain injury patients. Pressure reactivity indices were computed in various frequency bands during the first 4 days following injury using bandpass filtering of the input ABP and ICP signals. Patient outcome was assessed using the extended Glasgow Outcome Scale (GOSe). The optimization criterion was the strength of the correlation with GOSe of the mean index value over the first 4 days following injury. Stability of the indices was measured as the mean absolute deviation of the minute by minute index value from 30-min moving averages. The optimal index frequency range for prediction of outcome was identified as 0.018-0.067 Hz (oscillations with periods from 55 to 15 s). The index based on this frequency range correlated with GOSe with ρ=-0.46 compared to -0.41 for standard PRx, and reduced the 30-min variation by 23%.

Introduction of the Uppsala Traumatic Brain Injury register for regular surveillance of patient characteristics and neurointensive care management including secondary insult quantification and clinical outcome

BACKGROUND

To improve neurointensive care (NIC) and outcome for traumatic brain injury (TBI) patients it is crucial to define and monitor indexes of the quality of patient care. With this purpose we established the web-based Uppsala TBI register in 2008. In this study we will describe and analyze the data collected during the first three years of this project.

METHODS

Data from the medical charts were organized in three columns containing: 1) Admission data; 2) Data from the NIC period including neurosurgery, type of monitoring, treatment, complications, neurological condition at discharge, and the amount of secondary insults; 3) Outcome six months after injury. Indexes of the quality of care implemented include: 1) Index of improvement; 2) Index of change; 3) The percentages of 'Talk and die' and 'Talk and deteriorate' patients.

RESULTS

Altogether 314 patients were included 2008-2010: 66 women and 248 men aged 0-86 years. Automatic reports showed that the proportion of patients improving during NIC varied between 80% and 60%. The percentage of deteriorated patients was less than 10%. The percentage of Talk and die/Talk and deteriorate cases was <1%. The mean Glasgow Coma Score (Motor) improved from 5.04 to 5.68 during the NIC unit stay. The occurrences of secondary insults were less than 5% of good monitoring time for intracranial pressure (ICP) >25 mmHg, cerebral perfusion pressure (CPP) <50 mmHg, and systolic blood pressure <100 mmHg. Favorable outcome was achieved by 64% of adults.

CONCLUSION

The Uppsala TBI register enables the routine monitoring of NIC quality indexes.

The use of nurse checklists in a bedside computer-based information system to focus on avoiding secondary insults in neurointensive care

The feasibility and accuracy of using checklists after every working shift in a bedside computer-based information system for documentation of secondary insults in the neurointensive care unit were evaluated. The ultimate goal was to get maximal attention to avoid secondary insults. Feasibility was investigated by assessing if the checklists were filled in as prescribed. Accuracy was evaluated by comparing the checklists with recorded minute-by-minute monitoring data for intracranial pressure-ICP, cerebral perfusion pressure CPP, systolic blood pressure SBP, and temperature. The total number of checklist assessments was 2,184. In 85% of the shifts, the checklists were filled in. There was significantly longer duration of monitoring time at insult level when Yes was filled in regarding ICP (mean 134 versus 30 min), CPP (mean 125 versus 26 min) and temperature (mean 315 versus 120 min). When a secondary insult was defined as >5% of monitoring time spent at insult level, the sensitivity/specificity for the checklist assessments was 31%/100% for ICP, 38%/99% for CPP, and 66%/88% for temperature. Checklists were feasible and appeared relatively accurate. Checklists may elevate the alertness for avoiding secondary insults and help in the evaluation of the patients. This concept may be the next step towards tomorrow critical care.

Early warning of EUSIG-defined hypotensive events using a Bayesian Artificial Neural Network

BACKGROUND

Hypotension is recognized as a potentially damaging secondary insult after traumatic brain injury. Systems to give clinical teams some early warning of likely hypotensive instability could be added to the range of existing techniques used in the management of this group of patients. By using the Edinburgh University Secondary Insult Grades (EUSIG) definitions for -hypotension (systolic arterial pressure <90 mmHg OR mean arterial -pressure <70 mmHg) we collected a group of ∼2,000 events by analyzing the Brain-IT database. We then constructed a Bayesian Artificial Neural Network (an advanced statistical modeling technique) that is able to provide some early warning when trained on this previously collected demographic and physiological data.

MATERIALS AND METHODS

Using EUSIG defined event data from the Brain-IT database, we identified a Bayesian artificial neural network (BANN) topology and constructed a series of datasets using a group of clinically guided input variables. This allowed us to train a BANN, which was then tested on an unseen set of patients from the Brain-IT database. The initial tests used a particularly harsh assessment criterion whereby a true positive prediction was only allowed if the BANN predicted an upcoming event to the exact minute. We have now developed the system to the point where it is about to be used in a two-stage Phase II clinical trial and we are also researching a more realistic assessment technique.

KEY RESULTS

We have constructed a BANN that is able to provide early warning to the clinicians based on a model that uses information from the physiological inputs; systolic and mean arterial pressure and heart rate; and demographic variables age and gender. We use 15-min SubWindows starting at 15 and 30 min before an event and process mean, slope and standard deviations. Based on 10 simulation runs, our current sensitivity is 36.25% (SE 1.31) with a specificity of 90.82% (SE 0.85). Initial results from a Phase I clinical study shows a model sensitivity of 40.95% (SE 6%) and specificity of 86.46% (SE 3%) Although this figure is low it is considered clinically useful for this dangerous condition, provided the false positive rate can be kept sufficiently low as to be practical in an intensive care environment.

CONCLUSION

We have shown that using advanced statistical modeling techniques can provide clinical teams with useful information that will assist clinical care.

Early warning of EUSIG-defined hypotensive events using a Bayesian Artificial Neural Network

BACKGROUND

Hypotension is recognized as a potentially damaging secondary insult after traumatic brain injury. Systems to give clinical teams some early warning of likely hypotensive instability could be added to the range of existing techniques used in the management of this group of patients. By using the Edinburgh University Secondary Insult Grades (EUSIG) definitions for -hypotension (systolic arterial pressure <90 mmHg OR mean arterial -pressure <70 mmHg) we collected a group of ∼2,000 events by analyzing the Brain-IT database. We then constructed a Bayesian Artificial Neural Network (an advanced statistical modeling technique) that is able to provide some early warning when trained on this previously collected demographic and physiological data.

MATERIALS AND METHODS

Using EUSIG defined event data from the Brain-IT database, we identified a Bayesian artificial neural network (BANN) topology and constructed a series of datasets using a group of clinically guided input variables. This allowed us to train a BANN, which was then tested on an unseen set of patients from the Brain-IT database. The initial tests used a particularly harsh assessment criterion whereby a true positive prediction was only allowed if the BANN predicted an upcoming event to the exact minute. We have now developed the system to the point where it is about to be used in a two-stage Phase II clinical trial and we are also researching a more realistic assessment technique.

KEY RESULTS

We have constructed a BANN that is able to provide early warning to the clinicians based on a model that uses information from the physiological inputs; systolic and mean arterial pressure and heart rate; and demographic variables age and gender. We use 15-min SubWindows starting at 15 and 30 min before an event and process mean, slope and standard deviations. Based on 10 simulation runs, our current sensitivity is 36.25% (SE 1.31) with a specificity of 90.82% (SE 0.85). Initial results from a Phase I clinical study shows a model sensitivity of 40.95% (SE 6%) and specificity of 86.46% (SE 3%) Although this figure is low it is considered clinically useful for this dangerous condition, provided the false positive rate can be kept sufficiently low as to be practical in an intensive care environment.

CONCLUSION

We have shown that using advanced statistical modeling techniques can provide clinical teams with useful information that will assist clinical care.

Trigger characteristics of EUSIG-defined hypotensive events

BACKGROUND

Hypotension is a recognized -secondary insult after traumatic brain injury (TBI). There are many definitions of hypotension, an often cited example being the Brain Trauma Foundation's current (2007) "Guidelines for the Management of Severe Traumatic Brain Injury," which defines hypotension as systolic pressure <90 mmHg. However, this same document declares "The importance of mean arterial pressure, as opposed to systolic pressure should also be stressed, …." Our work shows that when using the Edinburgh University Secondary Insult Grades (EUSIG) definitions, which require monitoring of both systolic and mean arterial pressures, that most hypotensive events are in fact triggered by a breach of the mean arterial level of 70 mmHg. We suggest that close monitoring of mean arterial pressure would enable clinical teams to avoid more potentially damaging hypotensive events.

MATERIALS AND METHODS

An analysis of 100 patients from the Brain-IT database was performed. Using the EUSIG definitions, 2,081 events can be obtained by analyzing the systolic and mean blood pressures on a minute by minute basis. A software program was written to identify and classify the trigger pattern for each event. A categorical analysis of these triggering patterns has been carried out.

KEY RESULTS

Our analysis shows that most events are triggered by a drop in mean arterial pressure. In fact a large number of events (91%) occur where the mean arterial pressure is below the threshold limits whereas the systolic pressure does not cross the 90 mmHg limit at all.

CONCLUSION

We suggest that more emphasis should be placed on closely monitoring mean arterial pressure as well as systolic pressure when trying to guard against hypotensive problems in traumatically brain injured patients. In future work we will study the underlying physiological mechanisms and attempt to further classify concomitant conditions that may be contributing to the onset of a hypotensive event.

Favorable Outcome in Traumatic Brain Injury Patients With Impaired Cerebral Pressure Autoregulation When Treated at Low Cerebral Perfusion Pressure Levels

BACKGROUND:

Cerebral pressure autoregulation (CPA) is defined as the ability of the brain vasculature to maintain a constant blood flow over a range of different systemic blood pressures by means of contraction and dilatation.

OBJECTIVE:

To study CPA in relation to physiological parameters, treatment, and outcome in a series of traumatic brain injury patients.

METHODS:

In this prospective observational study, 44 male and 14 female patients (age, 15–72 years; mean, 38.7 years; Glasgow Coma Scale score, 4-13; median, 7) were analyzed. Patients were divided into groups on the basis of status of CPA (more pressure active vs more pressure passive) and level of cerebral perfusion pressure (CPP; low vs high CPP). The proportions of favorable outcome in the groups were assessed. Differences in physiological variables in the different groups were analyzed.

RESULTS:

Patients with more impaired CPA treated at CPP levels below median had a significantly higher proportion of favorable outcome compared with patients with more impaired CPA treated at CPP levels above median. No significant difference in outcome was seen between patients with more intact CPA when divided by level of CPP. In patients with more impaired CPA, CPP &lt; 50 mm Hg and CPP &lt; 60 mm Hg were associated with favorable outcome, whereas CPP &gt; 70 mm Hg and CPP &gt; 80 mm Hg were associated with unfavorable outcome. In patients with more intact CPA, no difference in physiological variables was seen between patients with favorable and unfavorable outcomes.

CONCLUSION:

Our results support that in traumatic brain injury patients with impaired CPA, CPP should not be elevated.

Neurointensive care is justified in elderly patients with severe subarachnoid hemorrhage--an outcome and secondary insults study

PURPOSE

The aim was to study the outcome and the occurrence of secondary brain insults in elderly patients with severe subarachnoid hemorrhage (SAH) in comparison to younger patients.

METHODS

Ninety-nine patients with severe SAH requiring a ventriculostomy and management at the neurointensive care unit with at least 120 h of multimodality monitoring data during the first 240 h following SAH were included. Data were continuously recorded for intracranial pressure (ICP), cerebral perfusion pressure, blood pressure, oxygen saturation, and temperature. Secondary insult levels were defined and quantified as percent of good monitoring time at insult level. Outcome according to the Glasgow Outcome Scale was evaluated at 6 months after the SAH. Age-dependent differences in occurrence of secondary insults and clinical characteristics were analyzed with multiple regression analysis.

RESULTS

Good recovery or moderate disability was achieved in 24.1% of the elderly and in 42.9% of the younger patients. The frequency of severe disability was 41.4% in the elderly and 37.1% in the younger patients. The occurrence of ICP insults was lower and the occurrence of hypertensive, hypotensive, and hypoxemic insults were higher in the elderly patients.

CONCLUSIONS

An independent outcome was achieved in a substantial proportion of the elderly with severe SAH, and the proportion of severe disability was not greater than among the younger patients, which justifies neurointensive care also in elderly patients. The occurrence of secondary insults was age dependent. Future studies of multimodality monitoring may provide age-specific secondary insult levels necessary for a tailored neurointensive care specific for elderly patients with severe SAH.

Federating distributed clinical data for the prediction of adverse hypotensive events

The ability to predict adverse hypotensive events, where a patient's arterial blood pressure drops to abnormally low (and dangerous) levels, would be of major benefit to the fields of primary and secondary health care, and especially to the traumatic brain injury domain. A wealth of data exist in health care systems providing information on the major health indicators of patients in hospitals (blood pressure, temperature, heart rate, etc.). It is believed that if enough of these data could be drawn together and analysed in a systematic way, then a system could be built that will trigger an alarm predicting the onset of a hypotensive event over a useful time scale, e.g. half an hour in advance. In such circumstances, avoidance measures can be taken to prevent such events arising. This is the basis for the Avert-IT project (http://www.avert-it.org), a collaborative EU-funded project involving the construction of a hypotension alarm system exploiting Bayesian neural networks using techniques of data federation to bring together the relevant information for study and system development.

Temperature disturbances in traumatic brain injury: relationship to secondary insults, barbiturate treatment and outcome

OBJECTIVES

To describe the occurrence of spontaneous hyper- and hypothermia in patients with traumatic brain injury using a computerized data collecting system, to show how temperature correlates with other secondary insults, to describe how temperature affects outcome and to show how barbiturate treatment influences those analyses.

METHODS

Patients with > or = 54 hours of valid monitoring within the first 120 hours after trauma (one value/min) for temperature, intracranial pressure, cerebral perfusion pressure, systolic blood pressure, mean blood pressure and heart rate were included. Correlation analyses were performed between temperature and other secondary insult variables. The non-linear relationship between temperature and outcome (measured by Glasgow outcome scale 6 months post-trauma) was illustrated using a neural network.

RESULTS

Of the 53 patients, 44 experienced hyperthermia (>38 degrees C) and 29 experienced hypothermia (<36 degrees C). Hyperthermia correlated with occurrence of high blood pressure and high CPP. In individuals, hyperthermia also correlated with ICP and tachycardia. There was a trend towards better outcome for patients with normal temperature than those with hyper- or hypothermia (favorable outcome 64% versus 29 and 33% respectively). When patients treated with barbiturates were excluded, 60% showed favorable outcome in the hypothermia group as well. Barbiturate treatment also confounded analyses regarding temperature and other secondary insults.

DISCUSSION

Patients with hyperthermia, hypertension, high CPP and tachycardia may suffer from a hyperdynamic state. This may worsen outcome and hence clinical awareness is important. Barbiturate treatment confounds several analyses which have not been shown before. We recommend those patients to be analysed separately in future studies.

The use of hyperventilation therapy after traumatic brain injury in Europe: an analysis of the BrainIT database

OBJECTIVE

To assess the use of hyperventilation and the adherence to Brain Trauma Foundation-Guidelines (BTF-G) after traumatic brain injury (TBI).

SETTING

Twenty-two European centers are participating in the BrainIT initiative.

DESIGN

Retrospective analysis of monitoring data.

PATIENTS AND PARTICIPANTS

One hundred and fifty-one patients with a known time of trauma and at least one recorded arterial blood-gas (ABG) analysis.

MEASUREMENTS AND RESULTS

A total number of 7,703 ABGs, representing 2,269 ventilation episodes (VE) were included in the analysis. Related minute-by-minute ICP data were taken from a 30 min time window around each ABG collection. Data are given as mean with standard deviation. (1) Patients without elevated intracranial pressure (ICP) (< 20 mmHg) manifested a statistically significant higher P(a)CO(2) (36 +/- 5.7 mmHg) in comparison to patients with elevated ICP (> or = 20 mmHg; P(a)CO(2): 34 +/- 5.4 mmHg, P < 0.001). (2) Intensified forced hyperventilation (P(a)CO(2) < or = 25 mmHg) in the absence of elevated ICP was found in only 49 VE (2%). (3) Early prophylactic hyperventilation (< 24 h after TBI; P(a)CO(2) < or = 35 mmHg, ICP < 20 mmHg) was used in 1,224 VE (54%). (4) During forced hyperventilation (P(a)CO(2) < or = 30 mmHg), simultaneous monitoring of brain tissue pO(2) or S(jv)O(2) was used in only 204 VE (9%).

CONCLUSION

While overall adherence to current BTF-G seems to be the rule, its recommendations on early prophylactic hyperventilation as well as the use of additional cerebral oxygenation monitoring during forced hyperventilation are not followed in this sample of European TBI centers.

DESCRIPTOR

Neurotrauma.

The brain monitoring with Information Technology (BrainIT) collaborative network: data validation results

BACKGROUND

The BrainIT group works collaboratively on developing standards for collection and analyses of data from brain injured patients towards providing a more efficient infrastructure for assessing new health technology.

MATERIALS AND METHODS

Over a 2 year period, core dataset data (grouped by nine categories) were collected from 200 head-injured patients by local nursing staff. Data were uploaded by the BrainIT web and random samples of received data were selected automatically by computer for validation by data validation (DV) research nurse staff against gold standard sources held in the local centre. Validated data was compared with original data sent and percentage error rates calculated by data category.

FINDINGS

Comparisons, 19,461, were made in proportion to the size of the data received with the largest number checked in laboratory data (5,667) and the least in the surgery data (567). Error rates were generally less than or equal to 6%, the exception being the surgery data class where an unacceptably high error rate of 34% was found.

CONCLUSIONS

The BrainIT core dataset (with the exception of the surgery classification) is feasible and accurate to collect. The surgery classification needs to be revised.

Secondary insults in subarachnoid hemorrhage: occurrence and impact on outcome and clinical deterioration

OBJECTIVE

To study the occurrence of secondary insults during neurointensive care of patients with subarachnoid hemorrhage using a computerized multimodality monitoring system and to study the impact of secondary insults on clinical deterioration and functional outcome.

METHODS

Patients with subarachnoid hemorrhage who were admitted to the neurointensive care unit between January 1999 and December 2002 with at least 120 hours of multimodality monitoring data within the first 240 hours of neurointensive care were included. Data were continuously recorded for intracranial pressure (ICP), cerebral perfusion pressure (CPP), mean arterial blood pressure, systolic blood pressure, oxygen saturation, and temperature. Secondary insult levels were defined as ICP of 20 or greater or 25 or greater; CPP of 60 or lower, 55 or lower, greater than 100, or greater than 110; mean arterial blood pressure of 80 or lower, 70 or lower, 120 or greater, or 130 or greater; systolic blood pressure of 110 or lower, 100 or lower, 180 or greater, or 200 or greater; temperature of 38 degrees C or higher or 39 degrees C or higher; and oxygen saturation of less than 95 or less than 90. Secondary insults were quantified as the proportion of good monitoring time at the insult level. Uni- and multivariate logistic regression analyses were performed with admission and secondary insult variables as explanatory variables and clinical deterioration and independent outcome as the dependent variable, respectively.

RESULTS

Ninety-nine patients (67 women; mean age, 57.8 yr) met the inclusion criteria. In the univariate analysis, ICP of 20 or greater, ICP of 25 or greater, CPP of 60 or less, and CPP of 55 or less increased the risk of clinical deterioration, whereas CPP greater than 100 and systolic blood pressure greater than 180 decreased the risk of clinical deterioration. In the multivariate logistic regression, ICP of 25 or greater and CPP of greater than 100 had an independent effect on clinical deterioration. The occurrence of secondary insults had no significant effect on functional outcome.

CONCLUSION

Elevated ICP not responding to treatment is predictive of clinical deterioration, whereas high CPP decreases the risk of clinical deterioration. It may be beneficial to not lower spontaneous high CPP in patients with subarachnoid hemorrhage.

BrainIT: a trans-national head injury monitoring research network

BACKGROUND

Studies of therapeutic interventions and management strategies on head injured patients are difficult to undertake. BrainIT provides validated data for analysis available to centers that contribute data to allow post-hoc analysis and hypothesis testing.

METHODS

Both physiological and intensive care management data are collected. Patient identification is eliminated prior to transfer of data to a central database in Glasgow. Requests for missing/ ambiguous data are sent back to the local center. Country coordinating centers provide advice, training, and assistance to centers and manage the data validation process.

RESULTS

Currently 30 centers participate in the group. Data collection started in January 2004 and 242 patients have been recruited. Data validation tools were developed to ensure data accuracy and all analysis must be undertaken on validated data.

CONCLUSION

BrainIT is an open, collaborative network that has been established with primary objectives of i) creating a core data set of information, ii) standardizing the collection methodology, iii) providing data collection tools, iv) creating and populating a data base for future analysis, and v) establishing data validation methodologies. Improved standards for multi-center data collection should permit the more accurate analysis of monitoring and management studies in head injured patients.

Accurate data collection for head injury monitoring studies: a data validation methodology

BACKGROUND

BrainIT is a multi centre, European project, to collect high quality continuous data from severely head injured patients using a previously defined [6] core data set. This includes minute-by-minute physiological data and simultaneous treatment and management information. It is crucial that the data is correctly collected and validated.

METHODS

Minute-by-minute physiological monitoring data is collected from the bedside monitors. Demographic and clinical information, intensive care management and secondary insult management data, are collected using a handheld computer. Data is transferred from the handheld device to a local computer where it is reviewed and anonymised before being sent electronically, with the physiological data, to the central database in Glasgow. Automated computer tools highlight missing or ambiguous data. A request is then sent to the contributing centre where the data is amended and returned to Glasgow. Of the required data elements 20% are randomly selected for validation against original documentation along with the actual number of specific episodic events during a known period. This will determine accuracy and the percentage of missing data for each record.

CONCLUSION

Advances in patient care require an improved evidence base. For accurate, consistent and repeatable data collection, robust mechanisms are required which should enhance the reliability of clinical trials, assessment of management protocols and equipment evaluations.

Survey of traumatic brain injury management in European Brain-IT centres year 2001

BACKGROUND

The aim of this study was to obtain basic knowledge about the current local conditions and neurointensive care of traumatic brain injury (TBI) in the new multi-centre collaborative BrainIT group.

MATERIALS AND METHODS

The survey comprised a background part on local policies (Part A), and a case study section (Part B). The information was gathered by questionnaire followed by telephone interviews. Twenty-three BrainIT centres participated in the survey and answers from two respondents were available from 18 of the sites.

RESULTS

The average proportion of agreement between duplicate respondents was 0.778 (range 0.415-1.00). All BrainIT centres monitored ICP. The treatment protocols seem to have a pattern concerning escalation of treatment of intracranial hypertension: 1/ evacuation of mass lesions and head elevation; 2/ increased sedation and mannitol; 3/ hyperventilation; 4/ ventricular drainage; 5/ craniectomy and barbituates.

CONCLUSIONS

There seemed to be an agreement on neurointensive care policies within the BrainIT group. The suggested order of treatment was generally in accordance with published guidelines although the suggested order and combinations of different treatments varied. Variation of treatment within the range of prescribed standards provides optimal conditions for an interesting future analysis of treatment and monitoring data in reality using the BrainIT database.

The BrainIT Group: concept and current status 2004

INTRODUCTION

An open collaborative international network has been established which aims to improve inter-centre standards for collection of high-resolution, neurointensive care data on patients with traumatic brain injury. The group is also working towards the creation of an open access, detailed and validated database that will be useful for hypothesis generation. In Part A, we describe the underlying concept of the group and it's aims and in Part B we describe the current status of the groups development.

METHODS

Four group meetings funded by the EEC have enabled definition of a "Core Dataset" to be collected from all centres regardless of specific project aim. A form based feasibility study was conducted and a prospective data collection exercise of core data using PC and hand held computer based methods is in progress.

FINDINGS

A core-dataset was defined and can be downloaded from the BrainIT web-site (go to "Core dataset" link at: www.brainit.org). A form based feasibility study was conducted showing the overall feasibility for collection of the core data elements was high. Software tools for collection of the core dataset have been developed. Currently, 130 patient's data from 16 European centres have been recruited to the joint database as part of an EEC funded proof of concept study.

INTERPRETATION

The BrainIT network provides a more standardised and higher resolution data collection mechanism for research groups, organisations and the device industry to conduct multicentre trials of new health care technology in patients with traumatic brain injury.

Cerebral perfusion pressure between 50 and 60 mm Hg may be beneficial in head-injured patients: a computerized secondary insult monitoring study

OBJECTIVE

To describe the occurrence of secondary insults using a computerized monitoring data collecting system and to investigate their relationship to outcome when the neurointensive care was dedicated to avoiding secondary insults.

METHODS

Patients 16 to 79 years old admitted to the neurointensive care unit between August 1998 and December 2002 with traumatic brain injury and 54 hours or more of valid monitoring within the first 120 hours after trauma (one value/min) were included. Monitoring of intracranial pressure (ICP), cerebral perfusion pressure (CPP), systolic blood pressure (BPs), and mean blood pressure (BPm) was required, and insult levels were defined (ICP >25/>35, BPs <100/<90/>160/>180, BPm <80/<70/>110/>120, and CPP <60/<50/>70/>80 mm Hg). Insults were quantified as proportion of valid monitoring time at the insult level. Logistic regression analyses were performed with admission and secondary insult variables as explanatory variables and favorable outcome as dependent variable.

RESULTS

Eighty-one patients, 63 men and 18 women, with a mean age of 43.0 years, fulfilled the inclusion criteria. Seventy-two patients (89%) had Glasgow Coma Scale scores of 8 or less. Thirty-one patients (38%) had diffuse injury, and 50 (62%) had mass lesions. Mean Injury Severity Score was 26.6. After 6 months, 54% of the patients had achieved a favorable outcome. Most patients spent 5% or less of the monitoring time at the insult level except for CPP greater than 70 mm Hg. Low age, high Glasgow Coma Scale motor score, low Injury Severity Score, and CPP less than 60 mm Hg insults were significant predictors of favorable outcome in the final multiple logistic regression model.

CONCLUSION

Overall, the secondary insults were rare, except for high CPP. The results suggest that patients with traumatic brain injury might benefit from a CPP slightly less than 60 mm Hg.

Pressure reactivity as a guide in the treatment of cerebral perfusion pressure in patients with brain trauma

Object. The aim of this study was to compare the effects of two different treatment protocols on physiological characteristics and outcome in patients with brain trauma. One protocol was primarily oriented toward reducing intracranial pressure (ICP), and the other primarily on maintaining cerebral perfusion pressure (CPP).

Methods. A series of 67 patients in Uppsala were treated according to a protocol aimed at keeping ICP less than 20 mm Hg and, as a secondary target, CPP at approximately 60 mm Hg. Another series of 64 patients in Edinburgh were treated according to a protocol aimed primarily at maintaining CPP greater than 70 mm Hg and, secondarily, ICP less than 25 mm Hg for the first 24 hours and 30 mm Hg subsequently.

The ICP and CPP insults were assessed as the percentage of monitoring time that ICP was greater than or equal to 20 mm Hg and CPP less than 60 mm Hg, respectively. Pressure reactivity in each patient was assessed based on the slope of the regression line relating mean arterial blood pressure (MABP) to ICP. Outcome was analyzed at 6 months according to the Glasgow Outcome Scale (GOS).

The prognostic value of secondary insults and pressure reactivity was determined using linear methods and a neural network. In patients treated according to the CPP-oriented protocol, even short durations of CPP insults were strong predictors of death. In patients treated according to the ICP-oriented protocol, even long durations of CPP insult—mostly in the range of 50 to 60 mm Hg—were significant predictors of favorable outcome (GOS Score 4 or 5). Among those who had undergone ICP-oriented treatment, pressure-passive patients (MABP/ICP slope ≥ 0.13) had a better outcome. Among those who had undergone CPP-oriented treatment, the more pressure-active (MABP/ICP slope < 0.13) patients had a better outcome.

Conclusions. Based on data from this study, the authors concluded that ICP-oriented therapy should be used in patients whose slope of the MABP/ICP regression line is at least 0.13, that is, in pressure-passive patients. If the slope is less than 0.13, then hypertensive CPP therapy is likely to produce a better outcome.

R3-Survey of traumatic brain injury management in European Brain IT centres year 2001

OBJECTIVE

To obtain knowledge about the conditions and management of traumatic brain injury (TBI) in a collaborative network of Brain Information Technology centres.

DESIGN

The Brain IT (Brain monitoring with Information Technology) survey comprised two parts: local conditions and policies (part A), and a case study part (part B). The information was gathered by written questionnaires followed by telephone interviews.

PARTICIPANTS

Twenty-four Brain IT centres participated (two respondents from 18 sites).

RESULTS

The average proportion of agreement between duplicate respondents was 0.79 (range 0.44-1.00). All Brain IT centres monitored ICP. The reported order of treatment for intracranial hypertension was: evacuation of mass-lesions and head elevation (1), increase of sedation and Mannitol scheme (2), hyperventilation (3), ventricular drainage (4), craniectomy and pentothal coma (5), and decompressive lobectomy (6). The respondents were less prone to evacuate expansive contusions in relation to extra cerebral hematomas. The most common suggested interventions (alone or in combination) for treatment of intracranial hypertension without mass lesions was the Mannitol scheme (included in 71% of the suggestions), CSF drainage (included in 56%), hyperventilation (included in 32%), and pentothal coma (included in 22%).

CONCLUSIONS

The suggested management of TBI was mainly in accordance with published guidelines, although a minor proportion of the answers deviated to some extent. The suggested order and combinations of different treatment interventions varied. Variation of treatment within the range of prescribed standards provides optimal conditions for an interesting future analysis of treatment and monitoring data as collected prospectively in a Brain IT database.

The BrainIT group: concept and core dataset definition

INTRODUCTION

An open collaborative international network has been established which aims to improve inter-centre standards for collection of high-resolution, neurointensive care data on patients with traumatic brain injury. The group is also working towards the creation of an open access, detailed and validated database that will be useful for post-hoc hypothesis testing. In Part A, the underlying concept, the group coordination structure, membership guidelines and database access and publication criteria are described. Secondly, in part B, we describe a set of meetings funded by the EEC that allowed us to define a "Core Dataset" and we present the results of a feasibility exercise for collection of this core dataset.

METHODS

Four group meetings funded by the EEC have enabled definition of a "Core Dataset" to be collected from all centres regardless of specific project aim. A paper based pilot collection of data was conducted to determine the feasibility for collection of the core dataset. Specially designed forms to collect the core dataset demographic and clinical information as well as sample the time-series data elements were distributed by both email and standard mail to 22 BrainIT centres. A deadline of two months was set to receive completed forms back from centres. A pilot data collection of minute by minute physiological monitoring data was also performed.

FINDINGS

A core-dataset was defined and can be downloaded from the BrainIT web-site (go to "Core dataset" link at: www.brainit.org). Eighteen centres (82%) returned completed forms by the set deadline. Overall the feasibility for collection of the core data elements was high with only 10 of the 64 questions (16%) showing missing data. Of those 10 fields with missing data, the average number of centres not responding was 12% and the median 6%. An SQL database to hold the data has been designed and is being tested. Software tools for collection of the core dataset have been developed. Ethics approval has been granted for collection of multi-centre data as part of a pilot data collection study.

INTERPRETATION

The BrainIT network provides a more standardised and higher resolution data collection mechanism for research groups, organisations and the device industry to conduct multi-centre trials of new health care technology in patients with traumatic brain injury.

Diverticular rupture during colonoscopy. Fact or fancy?

Uncomplicated colonic diverticula have been regarded as weak points in the bowel wall which have a predisposition to rupture during colonoscopy. We attempted to prove or disprove this assumption. Eleven segments of diverticula-containing sigmoid colon were insufflated via a colonoscope and the rupture pressure manometrically recorded. The mean +/- SEM pressure causing serosal tear was 202 +/- 15 mm Hg and mucosal rupture 226 +/- 14 mm Hg. No diverticular blowouts occurred. Intraluminal sigmoid pressures were measured manometrically in 15 patients with and 15 patients without colonic diverticula during routine colonoscopy. The pressure recordings were read in a blinded fashion, and the values were then grouped and analyzed in those patients with and without sigmoid colon diverticula. Intrarectal, sigmoid, peak sigmoid, peak sigmoid with cough, and peak sigmoid with Valsalva pressures were similar in both groups. Furthermore, the pressure levels generated during colonoscopy were much lower than those required for colonic rupture in the cadaver colons. We conclude that the reason most colonic perforations occur in the sigmoid area is not due to diverticular blowout. Rather, excluding instances where electrocautery is used, we feel it is due to instrument trauma. Less commonly, excessive air insufflation can result in serosal laceration and mucosal rupture, whereas diverticular blowout is probably limited to the setting of acute diverticulitis.