Management of Acute Intracranial Hypertension: A Review

Optic Nerve Sheath Diameter Ultrasound: A Non-Invasive Approach to Evaluate Increased Intracranial Pressure in Critically Ill Pediatric Patients

Early diagnosis of increased intracranial pressure (ICP) is crucial for prompt diagnosis and treatment of intracranial hypertension in critically ill pediatric patients, preventing secondary brain damage and mortality. Although the placement of an external ventricular drain coupled to an external fluid-filled transducer remains the gold standard for continuous ICP monitoring, other non-invasive approaches are constantly being improved and can provide reliable estimates. The use of point-of-care ultrasound (POCUS) for the assessment of ICP has recently become widespread in pediatric emergency and critical care settings, representing a valuable extension of the physical examination. The aim of this manuscript is to review and discuss the basic principles of ultra-sound measurement of the optic nerve sheath diameter (ONSD) and summarize current evidence on its diagnostic value in pediatric patients with ICP. There is increasing evidence that POCUS measurement of the ONSD correlates with ICP, thus appearing as a useful extension of the physical examination in pediatrics, especially in emergency medicine and critical care settings for the initial non-invasive assessment of patients with suspected raised ICP. Its role could be of value even to assess the response to therapy and in the follow-up of patients with diagnosed intracranial hypertension if invasive ICP monitoring is not available. Further studies on more homogeneous and extensive study populations should be performed to establish ONSD reference ranges in the different pediatric ages and to define cut-off values in predicting elevated ICP compared to invasive ICP measurement.

Accuracy of bedside bidimensional transcranial ultrasound versus tomodensitometric measurement of the third ventricle

BACKGROUND AND PURPOSE

To evaluate the accuracy of transcranial duplex sonography (TCS) for measuring the diameter of the third ventricle (DTV) and the brain midline shift (MLS), as compared to cerebral CT.

METHODS

Single-center retrospective study including 177 patients admitted to the neurological intensive care unit (NICU). We studied the correlation between TCS and CT measurements of DTV and MLS using a Bland-Altman analysis. The best threshold of DTV to diagnose acute hydrocephalus was evaluated with a receiver operating characteristic (ROC) analysis.

RESULTS

We analyzed 177 pairs of CT-TCS measurements for DTV and 165 for MLS. The mean time interval between CT and TCS was 87 ± 73 minutes. Median DTV measurement on CT was 4 ± 3 mm, and 5 ± 3 mm by TCS. Median MLS on CT was 2 ± 3 mm, and 2 ± 4 mm by TCS. The Pearson correlation coefficient (r² ) was .96 between TCS and CT measurements (p < .001). The Bland-Altman analysis found a proportional bias of 0.69 mm for the DTV with a limit of agreement ranging between -3.04 and 2.53 mm. For the MLS, the proportional bias was 0.23 mm with limits of agreements between -3.5 and 3.95. The area under the ROC curve was .97 for the detection of hydrocephalus by DTV on TCS, with a best threshold of 5.72 mm (Sensitivity [Se] = 92% Specificity [Sp] = 92.1%).

CONCLUSIONS

TCS seems to be a reliable and accurate bedside technique for measuring both DTV and MLS, which might allow detection of acute hydrocephalus among NICU patients.

Randomized Clinical Trial of 20% Mannitol Versus 3% Hypertonic Saline in Children With Raised Intracranial Pressure Due to Acute CNS Infections

OBJECTIVES

Mannitol is a commonly used osmotherapy agent in raised intracranial pressure. However, the side effects of mannitol are significant. In traumatic brain injury (adult and pediatric), hypertonic saline (3%) shows varied results in comparison with 20% mannitol. We compared the effect of 3% hypertonic saline versus 20% mannitol (using common dosing strategies) on raised intracranial pressure in pediatric acute CNS infections.

DESIGN

Open-label randomized controlled trial.

SETTING

PICU of a quaternary care academic institute.

PATIENTS

Children 1-12 years old, with raised intracranial pressure and modified-Glasgow Coma Scale scores less than or equal to 8, were enrolled.

INTERVENTIONS

Patients were randomly assigned to 20%-mannitol (n = 28), 0.5 gram/kg/dose versus 3%-hypertonic saline (n = 29), 10 mL/kg loading followed by 0.5-1 mL/kg/hr infusion. An intraparenchymal catheter was used to monitor the intracranial pressure. The primary outcome was the proportion of patients achieved target average intracranial pressure less than 20 mm Hg during 72 hours. Secondary outcomes were interventions, morbidity, and mortality.

MEASUREMENTS AND MAIN RESULTS

The proportion of patients with target average intracranial pressure (< 20 mm Hg) was higher in hypertonic saline-group as compared to mannitol-group (79.3% vs 53.6%; adjusted hazard ratio 2.63; 95% CI: 1.23-5.61). Mean (± SE) reduction of intracranial pressure (-14.3 ± 1.7 vs -5.4 ± 1.7 mm Hg; p ≤ 0.001) and elevation of cerebral perfusion pressure (15.4 ± 2.4 vs 6 ± 2.4 mm Hg; p = 0.007) from baseline were significant in hypertonic saline-group. Mean (± SE) intracranial pressure over 72 hours was lower (14 ± 2 vs 22 ± 2 mm Hg; p = 0.009), and cerebral perfusion pressure was higher (65 ± 2.2 vs 58 ± 2.2; p = 0.032) in hypertonic saline-group. Hypertonic saline-group had higher modified-Glasgow Coma Scale score at 72 hours (median, interquartile range 10; 7-11 vs 7; 3-9; p = 0.003), lower mortality (20.7% vs 35.7%; p = 0.21), shorter duration of mechanical ventilation (5 vs 15 d; p = 0.002), and PICU stay (11 vs 19 d; p = 0.016) and less severe neurodisability at discharge (31% vs 61%; p = 0.049).

CONCLUSIONS

In pediatric acute CNS infections, 3%-hypertonic saline was associated with a greater reduction of intracranial pressure as compared to 20% mannitol.

Pentobarbital Induced Hypokalemia: A Worrying Sequela

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High dose barbiturate use has been linked to life threatening hypokalemia and rebound hyperkalemia.

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Pentobarbital is a barbiturates that is used in high doses to induce a coma state to lower intracranial pressures.

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Through constant monitoring of potassium levels and permissive hypokalemia, avoidance of rebound hyperkalemia is achievable.

Introduction

Intracranial hypertension that is not responsive to other therapies can be managed through the use of a barbiturate induced coma. Although potentially effective, there are known complications associated with this treatment, and as such it is typically reserved for the most severe cases. One such sequela of barbiturate induced coma therapy is refractory hypokalemia and subsequent rebound hyperkalemia.

Presentation of case

This case report discusses a patient who experienced hypokalemia during pentobarbital induced coma for unmanageable elevations in intracranial pressure and was treated conservatively to avoid rebound hyperkalemia depicting successful deployment of permissive hypokalemia.

Discussion

It is vital that clinicians understand the possible adverse effects associated with barbiturate induced coma therapy, and that a careful balance be struck between hypokalemia and potassium supplementation to avoid rebound hyperkalemia.

Conclusion

Given that the risk of rebound hyperkalemia is of significant concern in patients who experience hypokalemia on barbiturate induced coma therapy, permissive hypokalemia can be a viable treatment option achieved by lowering the potassium replacement target threshold in such patients.

Life-Threatening Dyskalaemia after Barbiturate Coma Therapy: The Strategy of Management

Barbiturate coma therapy (BCT) is a treatment option that is used for refractory intracranial hypertension after all other options have been exhausted. Although BCT is a brain protection treatment, it also has several side effects such as hypotension, hepatic dysfunction, renal dysfunction, respiratory complications and electrolyte imbalances. One less concerning but potentially life-threatening complication of BCT is dyskalaemia. This complication could present as severe refractory hypokalaemia during the therapy with subsequent rebound hyperkalaemia after cessation of the therapy. Judicious potassium replacement during severe refractory hypokalaemia and gradual cessation of the therapy to prevent rebound hyperkalaemia are recommended strategies to deal with this complication, based on previous case series and reports. In this case report, we show that these strategies were applicable in improving severe hypokalaemia and preventing sudden, life-threatening rebound hyperkalaemia. However, even with use of these strategies, BCT patients could still present with mild, asymptomatic hyperkalaemia.

Management of Refractory Intracranial Pressure

Patients with refractory intracranial pressure represent a challenge to the multidisciplinary critical care team. Myriad diagnoses: traumatic brain injury, subarachnoid hemorrhage, intracranial hemorrhage, and ischemic stroke, are among the causes commonly seen in patients with elevated intracranial pressure. Clinicians tasked with caring for these patients must be aware of available interventions and management strategies to improve outcomes. Nurses as the bedside clinician most frequently assessing these patients are ideally situated to detect changes and act efficiently to lower refractory intracranial pressure.

Bedside burr hole for intracranial pressure monitoring performed by pediatric intensivists in children with CNS infections in a resource-limited setting: 10-year experience at a single center

OBJECTIVE

Intracranial pressure monitoring can help in early identification of raised intracranial pressure and in setting more informed goals for treatment. We describe our 10-year experience of bedside burr holes performed by pediatric intensivists to establish intracranial pressure monitoring in children with CNS infections in a resource-limited setting and the technical difficulties and complications encountered.

DESIGN

Descriptive study of prospectively recorded data.

SETTING

PICU of a tertiary care academic institute.

PATIENTS

Consecutive comatose patients with raised intracranial pressure who underwent intracranial pressure monitoring from 2004 to 2013.

INTERVENTION

An intraparenchymal (1.2 mm) or an intraventricular transducer (3.4 mm) (Codman) was placed by a pediatric intensivist through a micro burr hole using a standard protocol. Technical difficulties during the procedure and complications were recorded.

MEASUREMENTS AND MAIN RESULTS

Over 10 years, 265 intracranial pressure catheters were placed in 259 patients, mainly for acute CNS infections (n = 242, 93.4%). Median age of patients was 4.8 years, youngest being 6 weeks; 21 patients (8.1%) were younger than 1 year. Intraparenchymal transducer was used in 252 patients (97.3%). Median (interquartile range) duration of intracranial pressure monitoring was 96 hours (72-144 hr). Complications were seen in 3.5% of patients (n = 9/259); the incidence was 0.28 per 1,000 hours of intracranial pressure monitoring. Procedure-related ventriculitis occurred in three of seven patients (42.8%) with intraventricular catheter, in contrast to none in patients with intraparenchymal transducer. Overall mortality was 32.8% (n = 85). On Cox-regression analysis, "blood component therapy" was an independent predictor of poor outcome defined as death or severe neurodisability (adjusted hazard ratio, 1.58; 95% CI, 1.16-2.16; p = 0.004).

CONCLUSIONS

In a resource-limited setting, pediatric intensivists can safely and successfully perform burr holes at bedside for establishing intraparenchymal intracranial pressure monitoring in children with acute CNS infections. However, our data do not support placement of ventriculostomy catheters by pediatric intensivists in similar settings.

Post-traumatic multimodal brain monitoring: response to hypertonic saline

Emerging evidence suggests that hypertonic saline (HTS) is efficient in decreasing intracranial pressure (ICP). However there is no consensus about its interaction with brain hemodynamics and oxygenation. In this study, we investigated brain response to HTS bolus with multimodal monitoring after severe traumatic brain injury (TBI). We included 18 consecutive TBI patients during 10 days after neurocritical care unit admission. Continuous brain monitoring applied included ICP, tissue oxygenation (PtO2) and cerebral blood flow (CBF). Cerebral perfusion pressure (CPP), cerebrovascular resistance (CVR), and reactivity indices related to pressure (PRx) and flow (CBFx) were calculated. ICM+software was used to collect and analyze monitoring data. Eleven of 18 (61%) patients developed 99 episodes of intracranial hypertension (IHT) greater than 20 mm Hg that were managed with 20% HTS bolus. Analysis over time was performed with linear mixed-effects regression modelling. After HTS bolus, ICP and CPP improved over time (p<0.001) following a quadratic model. From baseline to 120 min, ICP had a mean decrease of 6.2 mm Hg and CPP a mean increase of 3.1 mmHg. Mean increase in CBF was 7.8 mL/min/100 g (p<0.001) and mean decrease in CVR reached 0.4 mm Hg*min*100 g/mL (p=0.01). Both changes preceded pressures improvement. PtO2 exhibited a marginal increase and no significant models for time behaviour could be fitted. PRx and CBFx were best described by a linear decreasing model showing autoregulation recover after HTS (p=0.01 and p=0.04 respectively). During evaluation, CO2 remained constant and sodium level did not exhibit significant variation. In conclusion, management of IHT with 20% HTS significantly improves cerebral hemodynamics and cerebrovascular reactivity with recovery of CBF appearing before rise in CPP and decrease in ICP. In spite of cerebral hemodynamic improvement, no significant changes in brain oxygenation were identified.

Impaired consciousness and herniation syndromes

This article reviews alterations in consciousness related to intracranial mass lesions. Such lesions can produce impairment of consciousness by their strategic location within components of the ascending reticular activating system or secondarily by compressing or distorting this system, interfering with its synaptic and neurochemical functions. This review concentrates principally on this secondary mechanism.

Brain-systemic temperature gradient is temperature-dependent in children with severe traumatic brain injury

OBJECTIVES

To understand the gradient between rectal and brain temperature in children after severe traumatic brain injury. We hypothesized that the rectal temperature and brain temperature gradient will be influenced by the child's body surface area and that this relationship will persist over physiologic temperature ranges.

DESIGN

Retrospective review of a prospectively collected pediatric neurotrauma registry.

SETTING

Academic, university-based pediatric neurotrauma program.

PATIENTS

Consecutive children (n = 40) with severe traumatic brain injury (Glasgow coma scale of <8) who underwent brain temperature monitoring (July 2003 to December 2008) were studied after informed consent was obtained. A subset of children (n = 24) were concurrently enrolled in a randomized, controlled clinical trial of early-moderate hypothermia for neuroprotection.

INTERVENTIONS

Data extraction of multiple clinical variables, including demographic data, body surface area, and rectal and brain temperature at recorded at hourly intervals.

MEASUREMENTS AND MAIN RESULTS

Paired brain and rectal temperature measurements (in degrees Celsius, n = 4369) were collected hourly and compared by using Pearson correlations. Patients were stratified according to body surface area (<1.0 m, 1.0-1.99 m, 2.0-2.99 m, and >3.0 m) and based on brain temperature (≤34.0, 34.1-36.0; 36.1-38, ≥38.1). Body surface area and brain temperature were compared between groups by using Pearson correlations with correction for repeated measures. Mean brain temperature-rectal temperature difference was calculated for stratified brain temperature ranges. Overall, brain and rectal temperatures were highly correlated (r = .86, p < .001). During brain hyperthermia, brain temperature-rectal temperature was similar to that reported in previous studies with brain temperature higher than rectal temperature (1.75 ± 0.4; r = .54). Surprisingly, this relationship was reversed during brain hypothermia (brain temperature-rectal temperature = -1.87 ± 0.8; r = .37), indicating a reversal of the brain-systemic temperature gradient. When stratified for body surface area, the correlation between rectal temperature and brain temperature remained strong (r = .78, 0.91, 0.79 and 0.95, respectively, p < .001). However, the correlation between brain temperature and rectal temperature was substantially decreased when stratified for brain temperature (r = .37, 0.58, 0.48, 0.54, p < .001). In particular, during moderate brain hypothermia (brain temperature ≤34), the correlation between brain temperature and rectal temperature was weakest, indicating the greatest variability during this condition which is often targeted for therapeutic trials.

CONCLUSIONS

Brain temperature and rectal temperature are generally well-correlated in children with traumatic brain injury. This relationship is different at the extremes of the physiologic temperature range, with the temperature gradient reversed during brain hypothermia and hyperthermia. Given that studies showing neuroprotection from hypothermia in animal models of brain injury generally target brain temperature, our data suggest the possibility that, if brain temperature were the therapeutic target in clinical trials, this would result in somewhat higher systemic temperature and potentially fewer side effects. This relationship may be exploited in future clinical trials to maintain brain hypothermia (for neurologic protection) at slightly higher systemic temperatures (and potentially fewer systemic side effects).