A. Graham Fieggen

Transcranial Doppler pulsatility index is not a reliable indicator of intracranial pressure in children with severe traumatic brain injury

BACKGROUND The TCD-derived PI has been associated with ICP in adult studies but has not been well investigated in children. We examined the relationship between PI and ICP and CPP in children with severe TBI. METHODS Data were prospectively collected from consecutive TCD studies in children with severe TBI undergoing ICP monitoring. Ipsilateral ICP and CPP values were examined with Spearman correlation coefficient (mean values and raw observations), with a GEE, and as binary values (1 and 20 mm Hg, respectively). RESULTS Thirty-four children underwent 275 TCD studies. There was a weak relationship between mean values of ICP and PI (P = .04, r = 0.36), but not when raw observations (P = .54) or GEE (P = .23) were used. Pulsatility index was 0.76 when ICP was lower than 20 mm Hg and 0.86 when ICP was 20 mm Hg or higher. When PI was 1 or higher, ICP was lower than 20 mm Hg in 62.5% (25 of 40 studies), and when ICP was 20 mm Hg or higher, PI was lower than 1 in 75% (46 of 61 studies). The sensitivity and specificity of a PI threshold of 1 for examining the ICP threshold of 20 mm Hg were 25% and 88%, respectively. The relationship between CPP and PI was stronger (P = .001, r = -0.41), but there were too few observations below 50 mm Hg to examine PI at this threshold. CONCLUSION The absolute value of the PI is not a reliable noninvasive indicator of ICP in children with severe TBI. Further study is required to examine the relationship between PI and a CPP threshold of 50 mm Hg.

Pressure autoregulation, intracranial pressure, and brain tissue oxygenation in children with severe traumatic brain injury

OBJECT Cerebral pressure autoregulation is an important neuroprotective mechanism that stabilizes cerebral blood flow when blood pressure (BP) changes. In this study the authors examined the association between autoregulation and clinical factors, BP, intracranial pressure (ICP), brain tissue oxygen tension (PbtO(2)), and outcome after pediatric severe traumatic brain injury (TBI). In particular we examined how the status of autoregulation influenced the effect of BP changes on ICP and PbtO(2). METHODS In this prospective observational study, 52 autoregulation tests were performed in 24 patients with severe TBI. The patients had a mean age of 6.3 +/- 3.2 years, and a postresuscitation Glasgow Coma Scale score of 6 (range 3-8). All patients underwent continuous ICP and PbtO(2) monitoring, and transcranial Doppler ultrasonography was used to examine the autoregulatory index (ARI) based on blood flow velocity of the middle cerebral artery after increasing mean arterial pressure by 20% of the baseline value. Impaired autoregulation was defined as an ARI < 0.4 and intact autoregulation as an ARI >or= 0.4. The relationships between autoregulation (measured as both a continuous and dichotomous variable), outcome, and clinical and physiological variables were examined using multiple logistic regression analysis. RESULTS Autoregulation was impaired (ARI < 0.4) in 29% of patients (7 patients). The initial Glasgow Coma Scale score was significantly associated with the ARI (p = 0.02, r = 0.32) but no other clinical factors were associated with autoregulation status. Baseline values at the time of testing for ICP, PbtO(2), the ratio of PbtO(2)/PaO(2), mean arterial pressure, and middle cerebral artery blood flow velocity were similar in the patients with impaired or intact autoregulation. There was an inverse relationship between ARI (continuous and dichotomous) with a change in ICP (continuous ARI, p = 0.005; dichotomous ARI, p = 0.02); that is, ICP increased with the BP increase when ARI was low (weak autoregulation). The ARI (continuous and dichotomous) was also inversely associated with a change in PbtO(2) (continuous ARI, p = 0.002; dichotomous ARI, p = 0.02). The PbtO(2) increased when BP was increased in most patients, even when the ARI was relatively high (stronger autoregulation), but the magnitude of this response was still associated with the ARI. There was no relationship between the ARI and outcome. CONCLUSIONS These data demonstrate the influence of the strength of autoregulation on the response of ICP and PbtO(2) to BP changes and the variability of this response between individuals. The findings suggest that autoregulation testing may assist clinical decision-making in pediatric severe TBI and help better define optimal BP or cerebral perfusion pressure targets for individual patients.

DOES ADHERENCE TO TREATMENT TARGETS IN CHILDREN WITH SEVERE TRAUMATIC BRAIN INJURY AVOID BRAIN HYPOXIA? A BRAIN TISSUE OXYGENATION STUDY

OBJECTIVE Most physicians rely on conventional treatment targets for intracranial pressure, cerebral perfusion pressure, systemic oxygenation, and hemoglobin to direct management of traumatic brain injury (TBI) in children. In this study, we used brain tissue oxygen tension (PbtO2) monitoring to examine the association between PbtO2 values and outcome in pediatric severe TBI and to determine the incidence of compromised PbtO2 in patients for whom acceptable treatment targets had been achieved. METHODS In this prospective observational study, 26 children with severe TBI and a median postresuscitation Glasgow Coma Scale score of 5 were managed with continuous PbtO2 monitoring. The relationships between outcome and the 6-hour period of lowest PbtO2 values and the length of time that PbtO2 was less than 20, 15, 10, and 5 mmHg were examined. The incidence of reduced PbtO2 for each threshold was evaluated where the following targets were met: intracranial pressure less than 20 mmHg, cerebral perfusion pressure greater than 50 mmHg, arterial oxygen tension greater than 60 mmHg (and peripheral oxygen saturation > 90%), and hemoglobin greater than 8 g/dl. RESULTS There was a significant association between poor outcome and the 6-hour period of lowest PbtO2 and length of time that PbtO2 was less than 15 and 10 mmHg. Multiple logistic regression analysis showed that low PbtO2 had an independent association with poor outcome. Despite achieving the management targets described above, 80% of patients experienced one or more episodes of compromised PbtO2 (< 20 mmHg), and almost one-third experienced episodes of brain hypoxia (PbtO2 < 10 mmHg). CONCLUSION Reduced PbtO2 is associated with poor outcome in pediatric severe TBI. In addition, many patients experience episodes of compromised PbtO2 despite achieving acceptable treatment targets.

The neurosurgical and acute care management of tuberculous meningitis: evidence and current practice.

Tuberculous meningitis (TBM) is the most lethal form of tuberculosis; mortality is high and survivors are often left neurologically disabled. Several factors contribute to this poor outcome, including cerebrovascular involvement with ensuing brain ischemia, hydrocephalus and raised intracranial pressure, direct parenchymal injury, hyponatremia, and seizures. However, there is little standardisation of management with respect to these aspects of care across different centers, largely because the evidence base for much of the supportive treatment of patients with TBM is poor, leading to substantial differences in management protocols. This review emphasizes some of the uncertainties and controversies pertinent to the surgical treatment of hydrocephalus in TBM and the medical supportive management of the patient during the acute phase of the illness, with the aims of raising awareness and stimulating debate. The focus is on the management of hyponatremia, cerebral hemodynamics and intracranial pressure, medical and surgical treatment for hydrocephalus, and the intensive care management of patients in the acute severe stage of the illness. Very little data are available to address these issues with good evidence and so institutional preferences are common; this is perhaps most notable for the management of hydrocephalus, and so in this the review highlights our personal practice. The brain needs protection while the source of the illness is addressed. Without attention to these aspects of management there will always be a limit to the effectiveness of antimicrobial therapy in TBM, so there is a strong imperative for the controversies to be resolved and the limitations of our current care to be addressed. Existing protocols should be rigorously examined and novel strategies to protect the brain should be explored. To this end, a prospective, multi-disciplinary and multi-centered approach may yield answers to the questions raised in this review.

The effect of blood transfusion on brain oxygenation in children with severe traumatic brain injury.

Objective: The indications for blood transfusion in traumatic brain injury are controversial. In particular, little is known about the effect of blood transfusion in childhood traumatic brain injury. This study aimed to examine the influence of blood transfusion on brain tissue oxygen tension in children with severe traumatic brain injury. Design: A retrospective analysis of a prospective observational database of children with severe traumatic brain injury who received brain tissue oxygen tension monitoring and a blood transfusion. Setting: University-affiliated pediatric hospital. Patients: Children with severe traumatic brain injury and blood transfusion. Interventions: None. Measurments and Main Results: Brain tissue oxygen tension was measured in normal-appearing white matter with a commercially available polarographic Clarke-type electrode. Brain tissue oxygen tension values after blood transfusion were compared with pre-transfusion values in hemodynamically stable patients. Limited interventions were allowed during the studied period. Brain tissue oxygen tension values were examined for early (1–4 hrs) and late (24 hrs) changes after blood transfusion, controlling for multiple clinical and physiologic variables with regression techniques. Further comparison was made with matched non-transfused controls to examine the influence of time after injury. Nineteen blood transfusions in 17 patients were evaluated. Brain tissue oxygen tension increased significantly in the early period after blood transfusion (p = .0018; 79% increased, 21% decreased) in comparison with baseline values and matched controls, but the overall changes were small and, in part, influenced by accompanying cerebral perfusion pressure changes. Also, this effect was limited to the early period after blood transfusion and was not significant after 24 hrs. In general, the brain tissue oxygen tension increase was larger in patients with higher baseline brain tissue oxygen tension and lower initial hemoglobin; however, no factors associated with the magnitude of the brain tissue oxygen tension change were significant in multivariate analysis. Increased age of blood did not appear to impair brain tissue oxygen tension changes, but most blood transfusion were <14 days old. Conclusions: Brain tissue oxygen tension increased transiently in 79% of blood transfusion in pediatric traumatic brain injury patients, and decreased transiently in 21%. Brain tissue oxygen tension returned to baseline within 24 hrs. Reliable predictors of this brain tissue oxygen tension response to blood transfusion, however, remain elusive.

Gait status 17–26 years after selective dorsal rhizotomy

The purpose of this study was to use three-dimensional gait analysis to describe the gait status of adults with spastic diplegia who underwent selective dorsal rhizotomy (SDR) in childhood. Outcome measures were the gait deviation index (GDI), non-dimensional temporal-distance parameters, and kinematics of the lower limbs. A total of 31 adults with spastic diplegia who had previously undergone SDR were eligible and participated in current study (SDR group). These participants had a median age of 26.8 years (range 21-44 years) with a mean time between surgery and assessment of 21.2±2.9 years (range 17-26 years). For comparison purposes, 43 typically developed adults also participated (CONTROL group), with a median age of 28.3 years (range 21-45 years). More than 17 years after SDR 58% of the SDR group showed improved GMFCS levels, while none of them deteriorated. The participants in the SDR group walked with a mild crouch gait, although there was a loading response, adequate swing-phase knee flexion, adequate swing-phase plantarflexion, reasonable speed and cadence. The gait status of the SDR group more than 17 years after SDR was similar to what has been reported in short-term follow-up studies, as well as our earlier 20 year follow-up study that did not include 3D gait analysis. Appropriate orthopaedic intervention was required in 61% of the study cohort. Whether the types and numbers of orthopaedic interventions are positively affected by SDR remains an open question. Further studies examining this question are warranted. In addition, long-term follow-up studies focused on other interventions would also be of clinical relevance.

Selection criteria for selective dorsal rhizotomy in children with spastic cerebral palsy: a systematic review of the literature

Information regarding the selection procedure for selective dorsal rhizotomy (SDR) in children with spastic cerebral palsy (CP) is scarce. Therefore, the aim of this study was to summarize the selection criteria for SDR in children with spastic CP.

The relationship between intracranial pressure and brain oxygenation in children with severe traumatic brain injury.

BACKGROUND Intracranial pressure (ICP) monitoring is a cornerstone of care for severe traumatic brain injury (TBI). Management of ICP can help ensure adequate cerebral blood flow and oxygenation. However, studies indicate that brain hypoxia may occur despite normal ICP and the relationship between ICP and brain oxygenation is poorly defined. This is particularly important for children in whom less is known about intracranial dynamics. OBJECTIVE To examine the relationship between ICP and partial pressure of brain tissue oxygen (PbtO2) in children with severe TBI (Glasgow Coma Scale score ≤ 8) admitted to Red Cross War Memorial Childrens Hospital, Cape Town. METHODS The relationship between time-linked hourly and high-frequency ICP and PbtO2 data was examined using correlation, regression, and generalized estimating equations. Thresholds for ICP were examined against reduced PbtO2 using age bands and receiver-operating characteristic curves. RESULTS Analysis using more than 8300 hourly (n = 75) and 1 million high-frequency data points (n = 30) demonstrated a weak relationship between ICP and PbtO2 (r = 0.05 and r = 0.04, respectively). No critical ICP threshold for low PbtO2 was identified. Individual patients revealed a strong relationship between ICP and PbtO2 at specific times, but different relationships were evident over longer periods. CONCLUSION The relationship between ICP and PbtO2 appears complex, and several factors likely influence both variables separately and in combination. Although very high ICP is associated with reduced PbtO2, in general, absolute ICP has a poor relationship with PbtO2. Because reduced PbtO2 is independently associated with poor outcome, a better understanding of ICP and PbtO2 management in pediatric TBI seems to be needed.

Acute clinical grading in pediatric severe traumatic brain injury and its association with subsequent intracranial pressure, cerebral perfusion pressure, and brain oxygenation

OBJECT The goal of this paper was to examine the relationship between methods of acute clinical assessment and measures of secondary cerebral insults in severe traumatic brain injury in children. METHODS Patients who underwent intracranial pressure (ICP), cerebral perfusion pressure (CPP), and brain oxygenation (PbtO(2)) monitoring and who had an initial Glasgow Coma Scale score, Pediatric Trauma Score, Pediatric Index of Mortality 2 score, and CT classification were evaluated. The relationship between these acute clinical scores and secondary cerebral insult measures, including ICP, CPP, PbtO(2), and systemic hypoxia were evaluated using univariate and multivariate analysis. RESULTS The authors found significant associations between individual acute clinical scores and select physiological markers of secondary injury. However, there was a large amount of variability in these results, and none of the scores evaluated predicted each and every insult. Furthermore, a number of physiological measures were not predicted by any of the scores. CONCLUSIONS Although they may guide initial treatment, grading systems used to classify initial injury severity appear to have a limited value in predicting who is at risk for secondary cerebral insults.

Continuous monitoring and intervention for cerebral ischemia in tuberculous meningitis.

Objective: Tuberculous meningitis (TBM) is a massive global problem. The mortality and morbidity associated with the severe form of the disease are exceptionally high. Even when increased intracranial pressure is treated and full conventional therapy is commenced, cerebral ischemia can develop and is associated with a particularly poor prognosis. We sought to evaluate our experience with two patients with severe TBM and cerebral oxygenation monitoring. Design: Case report. Setting: Red Cross Children’s Hospital, Cape Town. Patients: Two comatose patients with TBM. Interventions: Targeted interventions against low cerebral oxygenation in one patient. Measurements and Main Results: Cerebral tissue oxygenation (Ptio2) was measured. In both patients, Ptio2 monitoring demonstrated delayed cerebral ischemia despite the institution of full conventional therapy and the control of intracranial pressure. These data confirm that the vascular involvement in TBM is potentially progressive and that failure to diagnose infarction initially is not merely due to a delay in the radiologic appearance. The first patient developed extensive infarction, consistent with Ptio2 readings, and subsequently died after treatment withdrawal. Intervention in the second patient successfully reversed a precipitous decline of the Ptio2 readings and may have prevented infarction in this patient. Conclusions: The development of delayed cerebral ischemia in TBM despite treatment is confirmed in these two patients. The reversal of a decline in Ptio2 readings suggests a possible benefit for cerebral oxygenation monitoring in selected patients with severe TBM.