Kah Keow Lee

Cerebral oxygenation, vascular reactivity, and neurochemistry following decompressive craniectomy for severe traumatic brain injury

OBJECT This study addresses the changes in brain oxygenation, cerebrovascular reactivity, and cerebral neurochemistry in patients following decompressive craniectomy for the control of elevated intracranial pressure (ICP) after severe traumatic brain injury (TBI). METHODS Sixteen consecutive patients with isolated TBI and elevated ICP, who were refractory to maximal medical therapy, underwent decompressive craniectomy over a 1-year period. Thirteen patients were male and 3 were female. The mean age of the patients was 38 years and the median Glasgow Coma Scale score on admission was 5. RESULTS Six months following TBI, 11 patients had a poor outcome (Group 1, Glasgow Outcome Scale [GOS] Score 1-3), whereas the remaining 5 patients had a favorable outcome (Group 2, GOS Score 4 or 5). Decompressive craniectomy resulted in a significant reduction (p < 0.001) in the mean ICP and cerebrovascular pressure reactivity index to autoregulatory values (< 0.3) in both groups of patients. There was a significant improvement in brain tissue oxygenation (PbtO(2)) in Group 2 patients from 3 to 17 mm Hg and an 85% reduction in episodes of cerebral ischemia. In addition, the durations of abnormal PbtO(2) and biochemical indices were significantly reduced in Group 2 patients after decompressive craniectomy, but there was no improvement in the biochemical indices in Group 1 patients despite surgery. CONCLUSIONS Decompressive craniectomy, when used appropriately in protocol-driven intensive care regimens for the treatment of recalcitrant elevated ICP, is associated with a return of abnormal metabolic parameters to normal values in patients with eventually favorable outcomes.

Barbiturate therapy for patients with refractory intracranial hypertension following severe traumatic brain injury: Its effects on tissue oxygenation, brain temperature and autoregulation

The aim of this study was to explore the effects of barbiturate coma on cerebral tissue oxygen tension and cerebrovascular pressure reactivity (PRx), as an index of cerebral autoregulation in severe head injury patients. This was a prospective observational clinical study of 12 patients with severe traumatic brain injury, carried out at a tertiary-level neurosurgical intensive care unit between April 2002 and May 2005. All patients received standard neurosurgical intensive care and monitoring. Probes for intracranial pressure (ICP), brain temperature (BT) and brain tissue oxygenation (PTiO2) were inserted into (noncontused) normal-looking white matter. Cerebrovascular PRx was measured as a moving correlation between ICP and arterial blood pressure. Barbiturate coma was instituted when ICP became refractory (ICP>20 mmHg). All data from the multimodal monitoring were digitally extracted and statistically analysed. The mean ICP decreased with barbiturate coma in eight of the 12 patients (75% of the patients), but only four achieved a value below 20 mmHg. Of eight patients with prebarbiturate PTiO2 levels above 10 mmHg, six had a further improvement in oxygenation. Thus, concordant favourable changes in ICP, PRx and PTiO2 with barbiturate coma were seen in those who survived. Effective response to barbiturates can be detected by improved PTiO2 and autoregulation (PRx) in severe head injury patients.

Temporal changes in cerebral tissue oxygenation with cerebrovascular pressure reactivity in severe traumatic brain injury

Objective: To investigate the temporal relationship between cerebrovascular pressure reactivity and brain tissue oxygenation in patients with severe head injury. Methods: In 40 patients, brain tissue oxygenation and intracranial pressure were monitored. Time-averaged values for intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PtiO2) were computed. The pressure reactivity index (PRx) was calculated. The mean values of the variables were obtained at the 6-h and 72-h post-injury time points, and the difference between the two time points for each of the variables was denoted as delta (δ). Results: Of the 40 patients, 32 were survivors and 8 were non-survivors. Statistically significant differences were present between these two groups with regard to δMAP (p = 0.013), ICP at 6 h (p = 0.027), CPP at 72 h (p = 0.018), δCPP (p = 0.033), PRx at 6 h (p = 0.029), PRx at 72 h (p = 0.002), PtiO2 at 72 h (p<0.0005) and δPtiO2 (p = 0.023) values, reflecting an improvement with time in survivors and a deterioration with time in non-survivors. In non-survivors, the magnitude of change in PtiO2 and CPP with time correlated in a negative linear fashion (p = 0.042 and 0.029, respectively) with the change in PRx with time, whereas no such relationship was seen in survivors. Conclusion: The severity of brain tissue oxygenation derangement correlates with increasing cerebrovascular dysautoregulation in patients succumbing to severe head injury, supporting the utility of PRx as a monitoring variable and the rationale for a target-driven approach to head injury management.

Use of programmable versus nonprogrammable shunts in the management of hydrocephalus secondary to aneurysmal subarachnoid hemorrhage: a retrospective study with cost-benefit analysis

OBJECTIVES The choice of programmable or nonprogrammable shunts for the management of hydrocephalus after aneurysmal subarachnoid hemorrhage (SAH) remains undefined. Variable intracranial pressures make optimal management difficult. Programmable shunts have been shown to reduce problems with drainage, but at 3 times the cost of nonprogrammable shunts. METHODS All patients who underwent insertion of a ventriculoperitoneal shunt for hydrocephalus after aneurysmal SAH between 2006 and 2012 were included. Patients were divided into those in whom nonprogrammable shunts and those in whom programmable shunts were inserted. The rates of shunt revisions, the reasons for adjustments of shunt settings in patients with programmable devices, and the effectiveness of the adjustments were analyzed. A cost-benefit analysis was also conducted to determine if the overall cost for programmable shunts was more than for nonprogrammable shunts. RESULTS Ninety-four patients underwent insertion of shunts for hydrocephalus secondary to SAH. In 37 of these patients, nonprogrammable shunts were inserted, whereas in 57 programmable shunts were inserted. Four (7%) of 57 patients with programmable devices underwent shunt revision, whereas 8 (21.6%) of 37 patients with nonprogrammable shunts underwent shunt revision (p = 0.0413), and 4 of these patients had programmable shunts inserted during shunt revision. In 33 of 57 patients with programmable shunts, adjustments were made. The adjustments were for a trial of functional improvement (n = 21), overdrainage (n = 5), underdrainage (n = 6), or overly sunken skull defect (n = 1). Of these 33 patients, 24 showed neurological improvements (p = 0.012). Cost-benefit analysis showed

A randomized, placebo-controlled pilot study of patients with spontaneous intraventricular haemorrhage treated with intraventricular thrombolysis

646.60 savings (US dollars) per patient if programmable shunts were used, because the cost of shunt revision is a lot higher than the cost of the shunt. CONCLUSIONS The rate of shunt revision is lower in patients with programmable devices, and these are therefore more cost-effective. In addition, the shunt adjustments made for patients with programmable devices also resulted in better neurological outcomes.

Post-traumatic hydrocephalus after ventricular shunt placement in a Singaporean neurosurgical unit.

Intraventricular hemorrhage (IVH) occurring after spontaneous intracerebral hemorrhage (ICH) is an independent risk factor for mortality. The use of intraventricular urokinase (Uk) to reduce intraventricular blood clot volume and improve outcome was investigated. Patients with IVH requiring external ventricular drainage were recruited and randomized into a double-blind placebo controlled study. Assessments of collected cerebrospinal fluid (CSF) haemoglobin (Hb) and serial CT scans were performed. The study outcomes were: infection rates, length of stay in the intensive care unit, survival, National Institutes of Health Stroke Scale score; and modified Rankin Scale scores. Our results showed an increase in both the drained CSF Hb concentration in patients treated with Uk compared to placebo and in the rate of resolution clot volume. No differences were found in the other outcome measures but there was a trend towards lowered mortality in the group treated with Uk. Therefore, intraventricular Uk resulted in faster resolution of IVH with no adverse events.

Changes in brain biochemistry and oxygenation in the zone surrounding primary intracerebral hemorrhage

Ventricular enlargement is a common finding after severe head injury and has a poor prognosis if associated with post-traumatic hydrocephalus (PTH). We retrospectively reviewed our head injury database and identified patients who suffered from severe head injury and subsequently had shunt insertion after a diagnosis of PTH. A total of 871 patients with severe head injury were admitted from April 1999 to December 2006. Twenty-three patients (2.6%) were diagnosed with post-traumatic hydrocephalus and had a shunt inserted. Multiple logistic regression analysis showed that age, and unilateral and bilateral decompressive craniectomy, were significant predictors of PTH. The timing of shunt placement was between 2 weeks and 5 months post-head injury with a mean interval of 70 days. Three patients developed complications after shunt insertion. Seventeen patients (74%) achieved improvement after shunt insertion while the remainder had no significant change in neurological status. Eleven patients (48%) had improvements in their Glasgow Coma Scale (GCS) score of ≥2 points, while six patients (26%) had a single-point improvement in their GCS score. At 1 year after shunting, 35% of patients had Glasgow Outcome Scale scores of 3 to 4. PTH is a condition that has an insidious onset with varying clinical and radiological presentations. The incidence is low but there is a significant benefit from ventricular shunt insertion. The use of cerebrospinal fluid dynamic studies, in addition to clinical and radiological findings, has the potential for better diagnosis and management of these patients.

Effects of temperature changes on cerebral biochemistry in spontaneous intracerebral hematoma

BACKGROUND While the management of primary intracerebral hemorrhage (ICH) remains controversial, there remains a subset of patients that undergo clot evacuation. This study aims to characterize brain physiology and biochemistry after surgery for this condition. METHODS Thirty-six consecutive patients requiring ventilation for primary ICH had intracranial pressure (ICP), tissue oxygenation (PbO2) and cerebral microdialysis (CMD) monitoring. 28 patients with a Glasgow Outcome Score (GOS) of 1-3 formed group 1 while 5 patients with a GOS of 4-5 formed group 2. The control group consisted of 3 patients managed conservatively without surgery. FINDINGS The mean PbO2 (24.5 +/- 20.8 mmHg) was higher in the patients in group 1 (poor outcome) compared with those in the control group (13.6 +/- 9.0 mmHg) (p < 0.001). Compared to patients in group 2, the patients in group 1 also had a higher PbO2 (p = 0.02) together with worse levels of lactate/pyruvate (L/P) ratio and glycerol (p < 0.001). In all 3 groups, ICP reduction to < 20 mmHg was achieved together with a return to of pressure reactivity (PRx) to < 0.3. CONCLUSIONS In spontaneous ICH, derangements in the perilesional tissue demonstrated by local techniques of PbO2 monitoring and CMD are not seen in global indices such as the PRx.

Brain tissue oxygenation monitoring in acute brain injury

BACKGROUND Fever worsens outcome in acute brain injury, presumably by accelerating secondary damage. Improved understanding of the pathophysiological processes that occur in spontaneous intracerebral hemorrhage (ICH) may help to determine if controlled normothermia might be of clinical benefit. METHODS In this prospective observational study over a period of 18 months at the National Neuroscience Institute, Singapore, we examined the effects of temperature changes on brain biochemistry and tissue oxygenation in 25 consecutive patients with spontaneous primary putaminal hemorrhage. The patients were divided into 3 groups according to the mean brain temperature over a 72-hour monitoring period following surgery and standard medical measures to control post-operative brain swelling and secondary injury. FINDINGS Patients that become spontaneously hypothermic with a mean brain temperature of less than 36 degrees centigrade (degrees C) had greater impairment in brain biochemistry as reflected by the worst brain lactate/pyruvate (L/P) ratio, glutamate and glucose dialysates. Brain tissue oxygenation, on the other hand, was highest and within normal limits in these spontaneously hypothermic patients. The hyperthemic group had similar L/P ratio, glycerol and glutamate levels when compared to the normothermic group. The glucose levels were found to be significantly different in all 3 groups. CONCLUSIONS Extremes of temperature in spontaneous ICH, in particular--spontaneous hypothermia with a mean brain temperature of less than 36 degrees C, are associated with a poor outcome. Cerebral microdialysis can be used to detect these detrimental changes that occur.

Prediction of early mortality in primary intracerebral hemorrhage in an asian population

Cerebral ischemia is one of the most important causes of secondary insults following acute brain injury. While intracranial pressure monitoring in the intensive care unit constitutes the cornerstone of neurocritical care monitoring, it does not reflect the state of oxygenation of the injured brain. The holy grail of neuromonitoring is a modality that would reflect accurately real time the status of oxygenation in the tissue of interest, is robust, artefact free and that which provides information that can be used for therapeutic interventions and to improve outcome. Such a device could conceivably be used to augment the sensitivity of current multi-modality monitoring systems in the neurocritical management of brain injured patients. This article examines the availability of data in the literature to support clinical use of local tissue oxygen probes in intensive care.