Use of sedative and analgesic agents in neurotrauma patients: effects on cerebral physiology

The neurological wake-up test in severe pediatric traumatic brain injury: a long term, single-center experience

Objectives

To describe the use and outcomes of the neurological wake-up test (NWT) in pediatric severe traumatic brain injury (pTBI).

Design

Retrospective single-center observational cohort study.

Setting

Medical-surgical tertiary pediatric intensive care unit (PICU) in a university medical center and Level 1 Trauma Center.

Patients

Children younger than 18 years with severe TBI [i.e., Glasgow Coma Scale (GCS) of ≤8] admitted between January 2010 and December 2020. Subjects with non-traumatic brain injury were excluded.

Measurements and main results

Of 168 TBI patients admitted, 36 (21%) met the inclusion criteria. Median age was 8.5 years [2 months to 16 years], 5 patients were younger than 6 months. Median initial Glasgow Coma Scale (GCS) and Glasgow Motor Scale (GMS) was 6 [3-8] and 3 [1-5]. NWTs were initiated in 14 (39%) patients, with 7 (50%) labelled as successful. Fall from a height was the underlying injury mechanism in those seven. NWT-failure occurred in patients admitted after traffic accidents. Sedation use in both NWT-subgroups (successful vs. failure) was comparable. Cause of NWT-failure was non-arousal (71%) or severe agitation (29%). Subjects with NWT failure subsequently had radiological examination (29%), repeat NWT (43%), continuous interruption of sedation (14%) or intracranial pressure (ICP) monitoring (14%). The primary reason for not doing NWTs was intracranial hypertension in 59%. Compared to the NWT-group, the non-NWT group had a higher PRISM III score (18.9 vs. 10.6), lower GCS/GMS at discharge, more associated trauma, and circulatory support. Nine patients (25%) died during their PICU admission, none of them had an NWT.

Conclusion

We observed limited use of NWTs in pediatric severe TBI. Patients who failed the NWT were indistinguishable from those without NWT. Both groups were more severely affected compared to the NWT successes. Therefore, our results may indicate that only a select group of severe pTBI patients qualify for the NWT.

Neurologic Assessment of the Neurocritical Care Patient

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

Brain Protection in Aortic Arch Surgery: An Evolving Field

Despite advances in cardiac surgery and anesthesia, the rates of brain injury remain high in aortic arch surgery requiring circulatory arrest. The mechanisms of brain injury, including permanent and temporary neurologic dysfunction, are multifactorial, but intraoperative brain ischemia is likely a major contributor. Maintaining optimal cerebral perfusion during cardiopulmonary bypass and circulatory arrest is the key component of intraoperative management for aortic arch surgery. Various brain monitoring modalities provide different information to improve cerebral protection. Electroencephalography gives crucial data to ensure minimal cerebral metabolism during deep hypothermic circulatory arrest, transcranial Doppler directly measures cerebral arterial blood flow, and near-infrared spectroscopy monitors regional cerebral oxygen saturation. Various brain protection techniques, including hypothermia, cerebral perfusion, pharmacologic protection, and blood gas management, have been used during interruption of systemic circulation, but the optimal strategy remains elusive. Although deep hypothermic circulatory arrest and retrograde cerebral perfusion have their merits, there have been increasing reports about the use of antegrade cerebral perfusion, obviating the need for deep hypothermia. With controversy and variability of surgical practices, moderate hypothermia, when combined with unilateral antegrade cerebral perfusion, is considered safe for brain protection in aortic arch surgery performed with circulatory arrest. The neurologic outcomes of brain protection in aortic arch surgery largely depend on the following three major components: cerebral temperature, circulatory arrest time, and cerebral perfusion during circulatory arrest. The optimal brain protection strategy should be individualized based on comprehensive monitoring and stems from well-executed techniques that balance the major components contributing to brain injury.

The Neurological Wake-up Test-A Role in Neurocritical Care Monitoring of Traumatic Brain Injury Patients?

The most fundamental clinical monitoring tool in traumatic brain injury (TBI) patients is the repeated clinical examination. In the severe TBI patient treated by continuous sedation in a neurocritical care (NCC) unit, sedation interruption is required to enable a clinical evaluation (named the neurological wake-up test; NWT) assessing the level of consciousness, pupillary diameter and reactivity to light, and presence of focal neurological deficits. There is a basic conflict regarding the NWT in the NCC setting; can the clinical information obtained by the NWT justify the risk of inducing a stress response in a severe TBI patient? Furthermore, in the presence of advanced multimodal monitoring and neuroimaging, is the NWT necessary to identify important clinical alterations? In studies of severe TBI patients, the NWT was consistently shown to induce a stress reaction including brief increases in intracranial pressure (ICP) and changes in cerebral perfusion pressure (CPP). However, it has not been established whether these short-lived ICP and CPP changes are detrimental to the injured brain. Daily interruption of sedation is associated with a reduced ventilator time, shorter hospital stay and reduced mortality in many studies of general intensive care unit patients, although such clinical benefits have not been firmly established in TBI. To date, there is no consensus on the use of the NWT among NCC units and systematic studies are scarce. Thus, additional studies evaluating the role of the NWT in clinical decision-making are needed. Multimodal NCC monitoring may be an adjunct in assessing in which TBI patients the NWT can be safely performed. At present, the NWT remains the golden standard for clinical monitoring and detection of neurological changes in NCC and could be considered in TBI patients with stable baseline ICP and CPP readings. The focus of the present review is an overview of the existing literature on the role of the NWT as a clinical monitoring tool for severe TBI patients.

Cerebral oxygen metabolism in neonatal hypoxic ischemic encephalopathy during and after therapeutic hypothermia

Pathophysiologic mechanisms involved in neonatal hypoxic ischemic encephalopathy (HIE) are associated with complex changes of blood flow and metabolism. Therapeutic hypothermia (TH) is effective in reducing the extent of brain injury, but it remains uncertain how TH affects cerebral blood flow (CBF) and metabolism. Ten neonates undergoing TH for HIE and seventeen healthy controls were recruited from the NICU and the well baby nursery, respectively. A combination of frequency domain near infrared spectroscopy (FDNIRS) and diffuse correlation spectroscopy (DCS) systems was used to non-invasively measure cerebral hemodynamic and metabolic variables at the bedside. Results showed that cerebral oxygen metabolism (CMRO2i) and CBF indices (CBFi) in neonates with HIE during TH were significantly lower than post-TH and age-matched control values. Also, cerebral blood volume (CBV) and hemoglobin oxygen saturation (SO2) were significantly higher in neonates with HIE during TH compared with age-matched control neonates. Post-TH CBV was significantly decreased compared with values during TH whereas SO2 remained unchanged after the therapy. Thus, FDNIRS-DCS can provide information complimentary to SO2 and can assess individual cerebral metabolic responses to TH. Combined FDNIRS-DCS parameters improve the understanding of the underlying physiology and have the potential to serve as bedside biomarkers of treatment response and optimization.

Sedation in traumatic brain injury

Several different classes of sedative agents are used in the management of patients with traumatic brain injury (TBI). These agents are used at induction of anaesthesia, to maintain sedation, to reduce elevated intracranial pressure, to terminate seizure activity and facilitate ventilation. The intent of their use is to prevent secondary brain injury by facilitating and optimising ventilation, reducing cerebral metabolic rate and reducing intracranial pressure. There is limited evidence available as to the best choice of sedative agents in TBI, with each agent having specific advantages and disadvantages. This review discusses these agents and offers evidence-based guidance as to the appropriate context in which each agent may be used. Propofol, benzodiazepines, narcotics, barbiturates, etomidate, ketamine, and dexmedetomidine are reviewed and compared.

[Experts' recommendations for stroke management in intensive care: intracranial hypertension]

This article aims to describe the arguments underlying the experts' recommendations for management of stroke patients in the intensive unit, focusing on intracranial hypertension. This article describes the pathophysiology, diagnostic methods and therapeutic options for intracranial hypertension after stroke, including medical and surgical management.

The neurological wake-up test increases stress hormone levels in patients with severe traumatic brain injury

OBJECTIVES

The "neurological wake-up test" is needed to evaluate the level of consciousness in patients with severe traumatic brain injury. However, the neurological wake-up test requires interruption of continuous sedation and may induce a stress response and its use in neurocritical care is controversial. We hypothesized that the neurological wake-up test induces an additional biochemical stress response in patients with severe traumatic brain injury.

PATIENTS

Twenty-four patients who received continuous propofol sedation and mechanical ventilation after moderate to severe traumatic brain injury (Glasgow Coma Scale score ≤ 8; patient age 18-71 yrs old) were analyzed. Exclusion criteria were age <18 yrs old, ongoing pentobarbital infusion, or markedly increased intracranial pressure on interruption of continuous sedation.

DESIGN

Single-center prospective study. During postinjury days 1-8, 65 neurological wake-up tests were evaluated. Adrenocorticotrophic hormone, epinephrine, and norepinephrine levels in plasma and cortisol levels in saliva were analyzed at baseline (during continuous intravenous propofol sedation) and during neurological wake-up test. Data are presented using medians and 25th and 75th percentiles.

SETTING

The study was performed in a university hospital neurocritical care unit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

At baseline, adrenocorticotrophic hormone and cortisol levels were 10.6 (6.0-19.4) ng/L and 16.0 (10.7-31.8) nmol/L, respectively. Immediately after the neurological wake-up test, adrenocorticotrophic hormone levels increased to 20.5 (11.1-48.4) ng/L (p < .05) and cortisol levels in saliva increased to 24.0 (12.3-42.5) nmol/L (p < .05). The plasma epinephrine and norepinephrine levels increased from a baseline of 0.3 (0.3-0.6) and 1.6 (0.9-2.3) nmol/L, respectively, to 0.75 (0.3-1.4) and 2.8 (1.28-3.58) nmol/L, respectively (both p < .05).

CONCLUSIONS

The neurological wake-up test induces a biochemical stress response in patients with severe traumatic brain injury. The clinical importance of this stress response remains to be established but should be considered when deciding the frequency and use of the neurological wake-up test during neurocritical care.

Comparative Study of Brain Protection Effect between Thiopental and Etomidate Using Bispectral Index during Temporary Arterial Occlusion

OBJECTIVE

This study was conducted to compare the effect of etomidate with that of thiopental on brain protection during temporary vessel occlusion, which was measured by burst suppression rate (BSR) with the Bispectral Index (BIS) monitor.

METHODS

Temporary parent artery occlusion was performed in forty one patients during cerebral aneurysm surgery. They were randomly assigned to one of two groups. General anesthesia was induced and maintained with 1.5-2.5 vol% sevoflurane and 50% N(2)O. The pharmacological burst suppression (BS) was induced by a bolus injection of thiopental (5 mg/kg, group T) or etomidate (0.3 mg/kg, group E) according to randomization prior to surgery. After administration of drugs, the hemodynamic variables, the onset time of BS, the numerical values of BIS and BSR were recorded at every minutes.

RESULTS

There were no significant differences of the demographics, the BIS numbers and the hemodynamic variables prior to injection of drugs. The durations of burst suppression in group E (11.1±6.8 min) were not statistically different from that of group T (11.1±5.6 min) and nearly same pattern of burst suppression were shown in both groups. More phenylephrine was required to maintain normal blood pressure in the group T.

CONCLUSION

Thiopental and etomidate have same duration and a similar magnitude of burst suppression with conventional doses during temporary arterial occlusion. These findings suggest that additional administration of either drug is needed to ensure the BS when the temporary occlusion time exceed more than 11 minutes. Etomidate can be a safer substitute for thiopental in aneurysm surgery.

Delirium: an emerging frontier in the management of critically ill children

Delirium is a syndrome of acute brain dysfunction that commonly occurs in critically ill adults and most certainly is prevalent in critically ill children all over the world. The dearth of information about the incidence, prevalence, and severity of pediatric delirium stems from the simple fact that there have not been well-validated instruments for routine delirium diagnosis at the bedside. This article reviewed the emerging solutions to this problem, including description of a new pediatric tool called the pCAM-ICU. In adults, delirium is responsible for significant increases in both morbidity and mortality in critically ill patients. The advent of new tools for use in critically ill children will allow the epidemiology of this form of acute brain dysfunction to be studied adequately, will allow clinical management algorithms to be developed and implemented following testing, and will present the necessary incorporation of delirium as an outcome measure for future clinical trials in pediatric critical care medicine.

Intensive care unit management of patients with stroke

Patients admitted with the diagnosis of "stroke" have a variety of different disorders that require specific treatment approaches in the critical care unit. Early thrombolysis for ischemic stroke and improvements in surgical and neurointerventional techniques for the treatment of aneurysms and arteriovenous malformations in patients with subarachnoid hemorrhage have been milestones in the past decade, but the evolvement of general management principles in critical care and the dedication of neurointensivists are equally important for improved outcomes. Strategies, which have been developed in other areas of intensive care medicine (eg, in patients with septic shock, acute respiratory distress syndrome, or trauma), need to be adopted and modified for the stroke patient. Prevention of iatrogenic complications and nosocomial infections is of utmost importance and requires sufficient numbers of trained personnel and high-quality equipment. Although the focus of attention in stroke patients is "brain resuscitation," comorbidities often limit the diagnostic and therapeutic options, and overall cardiopulmonary and metabolic functions need to be optimized in order to prevent secondary injury and allow the brain to recover. As part of a holistic approach to the rehabilitation process, psychologic and spiritual support for the patient must start early on in the intensive care unit, and family members should be involved in the patient's care and provided with special support as well.

Diagnosing delirium in critically ill children: Validity and reliability of the Pediatric Confusion Assessment Method for the Intensive Care Unit

OBJECTIVE

To validate a diagnostic instrument for pediatric delirium in critically ill children, both ventilated and nonventilated, that uses standardized, developmentally appropriate measurements.

DESIGN AND SETTING

A prospective observational cohort study investigating the Pediatric Confusion Assessment Method for Intensive Care Unit (pCAM-ICU) patients in the pediatric medical, surgical, and cardiac intensive care unit of a university-based medical center.

PATIENTS

A total of 68 pediatric critically ill patients, at least 5 years of age, were enrolled from July 1, 2008, to March 30, 2009.

INTERVENTIONS

None.

MEASUREMENTS

Criterion validity including sensitivity and specificity and interrater reliability were determined using daily delirium assessments with the pCAM-ICU by two critical care clinicians compared with delirium diagnosis by pediatric psychiatrists using Diagnostic and Statistical Manual, 4th Edition, Text Revision criteria.

RESULTS

A total of 146 paired assessments were completed among 68 enrolled patients with a mean age of 12.2 yrs. Compared with the reference standard for diagnosing delirium, the pCAM-ICU demonstrated a sensitivity of 83% (95% confidence interval, 66-93%), a specificity of 99% (95% confidence interval, 95-100%), and a high interrater reliability (κ = 0.96; 95% confidence interval, 0.74-1.0).

CONCLUSIONS

The pCAM-ICU is a highly valid reliable instrument for the diagnosis of pediatric delirium in critically ill children chronologically and developmentally at least 5 yrs of age. Use of the pCAM-ICU may expedite diagnosis and consultation with neuropsychiatry specialists for treatment of pediatric delirium. In addition, the pCAM-ICU may provide a means for delirium monitoring in future epidemiologic and interventional studies in critically ill children.

Effect of an analgo-sedation protocol for neurointensive patients: a two-phase interventional non-randomized pilot study

Introduction

Sedation protocols are needed for neurointensive patients. The aim of this pilot study was to describe sedation practice at a neurointensive care unit and to assess the feasibility and efficacy of a new sedation protocol. The primary outcomes were a shift from sedation-based to analgesia-based sedation and improved pain management. The secondary outcomes were a reduction in unplanned extubations and duration of sedation.

Methods

This was a two-phase (before-after), prospective controlled study at a university-affiliated, 14-bed neurointensive care unit in Denmark. The sample included patients requiring mechanical ventilation for at least 48 hours treated with continuous sedative and analgesic infusions or both. During the observation phase the participants (n = 106) were sedated as usual (non-protocolized), and during the intervention phase the participants (n = 109) were managed according to a new sedation protocol.

Results

Our study showed a shift toward analgo-sedation, suggesting feasibility of the protocol. We found a significant reduction in the use of propofol (P < .001) and midazolam (P = .001) and an increase in fentanyl (P < .001) and remifentanil (P = .003). Patients selected for daily sedation interruption woke up faster, and estimates of pain free patients increased from 56.8% to 82.7% (P < .001), suggesting efficacy of the protocol. The duration of sedation and unplanned extubations were unchanged.

Conclusions

Our pilot study showed feasibility and partial efficacy of our protocol. Some neurointensive patients might not benefit from protocolized practice. We recommend an interdisciplinary effort to target patients requiring less sedation, as issues of oversedation and inadequate pain management still need more attention.

Trial registration

ISRCTN80999859.

Effects of the neurological wake-up test on intracranial pressure and cerebral perfusion pressure in brain-injured patients

OBJECTIVE

To evaluate the effects of the neurological "wake-up test" (NWT), defined as interruption of continuous propofol sedation and evaluation of the patient's level of consciousness, on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in patients with severe subarachnoid hemorrhage (SAH) or traumatic brain injury (TBI).

METHODS

A total of 127 NWT procedures in 21 severely brain-injured adult patients with either TBI (n = 12) or SAH (n = 9) were evaluated. ICP and CPP levels prior to, during and after the NWT procedure were recorded.

RESULTS

During the NWT, ICP increased from 13.4 +/- 6 mmHg at baseline to 22.7 +/- 12 (P < 0.05) and the CPP increased from 75.6 +/- 11 to 79.1 +/- 21 mmHg (P < 0.05) in TBI patients. Eight patients showed a reduced CPP during the NWT due to increased ICP. In SAH patients, ICP increased from 10.6 +/- 5 to 16.8 +/- 8 mmHg (P < 0.05) and the CPP increased from 76.9 +/- 13 to 84.6 +/- 15 mmHg (P < 0.05).

CONCLUSION

When continuous propofol sedation was interrupted and NWT was performed in severely brain-injured patients, the mean ICP and CPP levels were modestly increased. A subset of patients showed more pronounced changes. To date, the role of the NWT in the neurointensive care of TBI and SAH patients is unclear. Although the NWT is safe in the majority of patients and may provide useful clinical information about the patient's level of consciousness, alternate monitoring methods are suggested in patients showing marked ICP and/or CPP changes during NWT.

Delirium: an emerging frontier in the management of critically ill children

The objectives of this article are (1) to introduce pediatric delirium and provide understanding of acute brain dysfunction with its classification and clinical presentations (2) to understand how delirium is diagnosed and discuss current modes of delirium diagnosis in the critically ill adult population and translation to pediatrics (3) to understand the prevalence and prognostic significance of delirium in the adult and pediatric critically ill population (4) to discuss the pathophysiology of delirium as currently understood, and (5) to provide general management guidelines for delirium.

Aspects of intracerebral hematomas--an update

BACKGROUND

In Norway, there are approximately 16000 strokes each year and 15% of these are caused by intracerebral hematomas. Intracerebral hemorrhage (ICH) results from the rupture of blood vessels within the brain parenchyma. ICH occurs as a complication of several diseases, the most prevalent of which is chronic hypertension. When hemorrhage develops in the absence of a pre-existing vascular malformation or brain parenchymal lesion, it is denoted primary ICH. Secondary ICH refers to hemorrhage complicating a pre-existing lesion. Primary ICH is the most common type of hemorrhagic stroke, accounting for approximately 10% of all strokes. Despite aggressive management strategies, the 30-day mortality remains high, at almost 50%, with the majority of deaths occurring within the first 2 days. At 6 months, only 20-30% achieve independent status.

MATERIAL AND METHODS

This article is based on clinical experience, modern therapeutic guidelines for the treatment of intracerebral hematomas and up-to-date medical literature found in Medline. The article discusses the pathophysiology, clinical aspects, treatment, and the prognosis of intracerebral hematomas.

RESULTS AND DISCUSSION

Advances in diagnosis, prognosis, pathophysiology, and treatment over the past few decades have significantly advanced our knowledge of ICH; however, much work still needs to be carried out. Future genetic and epidemiologic studies will help identify at-risk populations and hopefully allow for primary prevention. Randomized controlled studies focusing on novel therapeutics should help to minimize secondary injury and hopefully improve morbidity and mortality.

The sedation of critically ill adults: part 2: management

The prevention and treatment of pain, anxiety, and delirium in the ICU are important goals. But achieving a balance between sedation and analgesia, especially in critically ill patients on mechanical ventilation, can be challenging. Both under- and oversedation carry grave risks. Without having an agreed-upon end point for sedation, different providers will likely have disparate treatment goals, increasing the risk of iatrogenic complications and possibly impeding recovery. In 2002 the Society of Critical Care Medicine, along with the American Society of Health-System Pharmacists, updated recommendations in its clinical practice guidelines for the sustained use of sedatives and analgesics in adults. This two-part series examines those recommendations concerning sedation assessment and management, as well as the current literature. Last month, Part 1 reviewed pertinent recommendations concerning pain and delirium and discussed tools for assessing pain, delirium, and sedation. This month, Part 2 explores pharmacologic and nonpharmacologic management of anxiety and agitation in the ICU. The second in a two-part series focuses on the pharmacologic and nonpharmacologic management of anxiety and agitation in the ICU.

Anaesthetic management of neurosurgical patients

Anaesthetic care of neurosurgical patients increasingly involves management issues that apply not only to 'asleep patients', but also to 'awake and waking-up patients' during and after intracranial operations. On one hand, awake brain surgery poses unique anaesthetic challenges for the provision of awake brain mapping, which requires that a part of the procedure is performed under conscious patient sedation. Recent case reports suggest that local infiltration anaesthesia combined with sedative regimens using short-acting drugs and improved monitoring devices have assumed increasing importance. These techniques may optimize rapid adjustments of the narcotic depth, providing analgesia and patient immobility yet permitting a swift return to cooperative patient alertness for functional brain tests. Regional anaesthesia and peripheral nerve blocks were used to prevent uncontrolled movements in special cases of intractable seizures. However, few of these strategies have been evaluated in controlled trials. Awake craniotomy for tumour removal is performed as early discharge surgery. Meticulous consideration of postoperative patient safety is therefore strongly advised. On the other hand, waking-up patients or the emergence from general anaesthesia after brain surgery is still an area with considerable variation in clinical practice. Developments indicate that fast-acting anaesthetic agents and prophylactic strategies to prevent postoperative complications minimize the adverse effects of anaesthesia on the recovery process. Recent data do not advocate a delay in extubating patients when neurological impairment is the only reason for prolonged intubation. An appropriate choice of sedatives and analgesics during mechanical ventilation of neurosurgical patients allows for a narrower range of wake-up time, and weaning protocols incorporating respiratory and neurological measures may improve outcome. In conclusion, despite a lack of key evidence to request 'fast-tracking pathways' for neurosurgical patients, innovative approaches to accelerate recovery after brain surgery are needed.

Using EEG to monitor anesthesia drug effects during surgery

The use of processed electroencephalography (EEG) using a simple frontal lead system has been made available for assessing the impact of anesthetic medications during surgery. This review discusses the basic principles behind these devices. The foundations of anesthesia monitoring rest on the observations of Guedel with ether that the depth of anesthesia relates to the cortical, brainstem and spinal effects of the anesthetic agents. Anesthesiologists strive to have a patient who is immobile, is unconscious, is hemodynamically stable and who has no intraoperative awareness or recall. These anesthetic management principles apply today, despite the absence of ether from the available anesthetic medications. The use of the EEG as a supplement to the usual monitoring techniques rests on the observation that anesthetic medications all alter the synaptic function which produces the EEG. Frontal EEG can be viewed as a surrogate for the drug effects on the entire central nervous system (CNS). Using mathematical processing techniques, commercial EEG devices create an index usually between 0 and 100 to characterize this drug effect. Critical aspects of memory formation occur in the frontal lobes making EEG monitoring in this area a possible method to assess risk of recall. Integration of processed EEG monitoring into anesthetic management is evolving and its ability to characterize all of the anesthetic effects on the CNS (in particular awareness and recall) and improve decision making is under study.

Impact of bispectral index monitoring on sedation and outcomes in critically ill adults: a case series

In situations in which clinical assessment of sedation level is compromised, such as deep sedation/analgesia with and without neuromuscular blockade (NMB), electroencephalogram-based monitoring may potentially assist in achieving balance between inadequate and excessive levels of sedation. To validate the bispectral index (BIS) for use in clinical practice, correlation and possible differences in outcome using clinical assessment versus clinical assessment augmented by electroencephalogram-based monitoring were determined. BIS monitoring was decisive in ICU care in 9 of 15 patients in this series. The most significant potential benefit was obtained in the subset of patients receiving NMB.

Effects of anesthesia on the responses to cortical spreading depression in the rat brain in vivo

OBJECTIVES

The aim of this study was to evaluate the effect of cortical spreading depression (CSD) on the metabolic, hemodynamic, electrical and ionic properties during anesthesia as compared with the awake state.

METHODS

The mitochondrial NADH redox state, reflected light, direct current (DC) potential, electrocorticography (ECoG), cerebral blood flow (CBF) and volume (CBV), and extracellular K(+) concentrations ([K(+)](e)), were measured continuously and simultaneously in real time using two unique monitoring systems that evaluate brain function. Three consecutive CSD waves were initiated using a KCl solution in both awake and anesthetized rats.

RESULTS AND DISCUSSION

CSD caused typical amplitude changes: biphasic waves in reflectance, oxidation cycles in NADH, an increase in CBF, CBV and in [K(+)](e), a negative shift in DC potential and depression in ECoG. Anesthesia by equithesin decreased significantly the baseline levels of CBF and [K(+)](e), showing a reduction in oxygen supply and demand. After anesthesia, CSD significantly decreased [K(+)](e) and NADH oxidation cycles, indicating a reduction in oxygen demand and in oxygen balance, respectively. Furthermore, anesthesia reduced CSD wave frequencies by slowing the recovery period, showing a decline in energy production during brain activation, or by changing electrophysiological properties of the tissue. No changes were found in the propagation rate and in the initiation period of CSD, which may indicate that equithesin does not block CSD initiation. In addition, we found that the whole cerebral cortex reacts homogenously to CSD and that equithesin may reduce oxygen demand and energy production, which may have a protective effect on the brain exposed to pathophysiological conditions.

Cerebral vascular autoregulation assessed by perfusion-CT in severe head trauma patients

PURPOSE

To use perfusion-CT technique in order to characterize cerebral vascular autoregulation in a population of severe head trauma patients with features of cerebral edema either on the admission or on the follow-up conventional noncontrast cerebral CT.

MATERIAL AND METHODS

A total of 80 perfusion-CT examinations were obtained in 42 severe head trauma patients with features of cerebral edema on conventional noncontrast cerebral CT, either on admission or during follow-up. Perfusion-CT results, i.e. the regional cerebral blood volume (rCBV) and flow (rCBF), were correlated with the mean arterial pressure (MAP) measured during each perfusion-CT examination. Ratios were defined to integrate the concept of cerebral vascular autoregulation, and cluster analysis performed, which allowed identification of different subgroups of patients. MAP values and perfusion-CT results in these groups were compared using Kruskal-Wallis and Wilcoxon (Mann-Whitney) tests. Moreover, the functional outcome of the 42 patients was evaluated 3 months after trauma on the basis of the Glasgow Outcome Scale (GOS) score and similarly compared between groups.

RESULTS

Three main groups of patients were identified: 1) 22 perfusion-CT examinations were collected in 13 patients, characterized by high rCBV and rCBF values and by significant dependence of perfusion-CT rCBV and rCBF results on MAP values (p<0.001), 2) 23 perfusion-CT examinations collected in 19 patients showing perfusion-CT results similar to control trauma subjects, and 3) 33 perfusion-CT collected in 16 patients, with low rCBV and rCBF values and near-independence of perfusion-CT results with respect to MAP values. The first group was interpreted as showing impaired cerebral vascular autoregulation, which was preserved in the third group. The second group was associated with the best functional outcome; it was linked to the first group, because eight patients went from one group to the other from admission to follow-up.

CONCLUSION

Perfusion-CT in severe head trauma patients was able to provide direct and quantitative assessment of cerebral vascular autoregulation with a single measurement. It could hence be used as a guide for brain edema therapy, as well as to monitor the treatment efficiency.

Refractory increased intracranial pressure in severe traumatic brain injury: barbiturate coma and bispectral index monitoring

Patients with severe traumatic brain injury resulting in increased intracranial pressure refractory to first-tier interventions challenge the critical care team. After exhausting these initial interventions, critical care practitioners may utilize barbiturate-induced coma in an attempt to reduce the intracranial pressure. Titrating appropriate levels of barbiturate is imperative. Underdosing the drug may fail to control the intracranial pressure, whereas overdosing may lead to untoward effects such as hypotension and cardiac compromise. Monitoring for a therapeutic level of barbiturate coma includes targeting drug levels and using continuous electroencephalogram monitoring, considered the gold standard. New technology, the Bispectral Index monitor, utilizes electroencephalogram principles to monitor the level of sedation and hypnosis in the critical care environment. This technology is now being considered for targeting appropriate levels of barbiturate coma.

Prevention of secondary brain injury: targeting technology

Use of technology in the management of the severely brain-injured patient has increased over the past decade and can be confusing and overwhelming to the critical care nurse clinicians who are new to the field of neurology. This article will describe normal physiology and cerebral dynamics and potential abnormal physiology encountered after brain injury. The technology reviewed will include intracranial pressure monitoring, cerebral blood flow monitoring and autoregulation, cerebral oxygen consumption and tissue oxygen monitoring, metabolism, sedation, and temperature monitoring. Integration of appropriate technology into patient management will be discussed using a case study to explore the utility of information at the bedside. Recognizing the difficult task of trying to control secondary injury in our patients is the first step to better outcomes. Implementing the use of technology to mitigate the situation must be done with careful consideration and a team approach to achieve the greatest benefit for the patient.

Brain injury after head trauma: pathophysiology, diagnosis, and treatment

Brain injury after impact to the head is due to both immediate mechanical effects and delayed responses of neural tissues. In horses, traumatic brain injury occurs in three main settings: (1) poll impact in horses that flip over backwards; (2) frontal/parietal impact in horses that run into a fixed object, and (3) injury to the vestibular apparatus secondary to temporohyoid osteoarthropathy. Distinct forebrain, vestibular, midbrain, hindbrain, or multifocal syndromes may be encountered in horses with traumatic brain injury. The most important components of treatment are those consistent with principles of "evidence-based medicine". Accordingly,secondary brain injury can most effectively be prevented by establishing normal blood pressure, temperature, blood glucose concentration, and tissue oxygenation. Pain must be controlled and brain swelling may be treated with infusions of hypertonic saline or mannitol. Surgical procedures, including unilateral hyoid bone transaction or elevation of skull fracture fragments, are indicated in selected cases. Optional additional treatments include use of anti-oxidants, conventional doses of corticosteroids, magnesium sulfate and drainage of CSE There is no indication for the use of massive doses of methyl prednisolone sodium succinate.

Safety and efficacy of analgesia-based sedation with remifentanil versus standard hypnotic-based regimens in intensive care unit patients with brain injuries: a randomised, controlled trial [ISRCTN50308308]

Introduction

This randomised, open-label, observational, multicentre, parallel group study assessed the safety and efficacy of analgesia-based sedation using remifentanil in the neuro-intensive care unit.

Methods

Patients aged 18–80 years admitted to the intensive care unit within the previous 24 hours, with acute brain injury or after neurosurgery, intubated, expected to require mechanical ventilation for 1–5 days and requiring daily downward titration of sedation for assessment of neurological function were studied. Patients received one of two treatment regimens. Regimen one consisted of analgesia-based sedation, in which remifentanil (initial rate 9 μg kg^-1 h^-1) was titrated before the addition of a hypnotic agent (propofol [0.5 mg kg^-1 h^-1] during days 1–3, midazolam [0.03 mg kg^-1 h^-1] during days 4 and 5) (n = 84). Regimen two consisted of hypnotic-based sedation: hypnotic agent (propofol days 1–3; midazolam days 4 and 5) and fentanyl (n = 37) or morphine (n = 40) according to routine clinical practice. For each regimen, agents were titrated to achieve optimal sedation (Sedation–Agitation Scale score 1–3) and analgesia (Pain Intensity score 1–2).

Results

Overall, between-patient variability around the time of neurological assessment was statistically significantly smaller when using remifentanil (remifentanil 0.44 versus fentanyl 0.86 [P = 0.024] versus morphine 0.98 [P = 0.006]. Overall, mean neurological assessment times were significantly shorter when using remifentanil (remifentanil 0.41 hour versus fentanyl 0.71 hour [P = 0.001] versus morphine 0.82 hour [P < 0.001]). Patients receiving the remifentanil-based regimen were extubated significantly faster than those treated with morphine (1.0 hour versus 1.93 hour, P = 0.001) but there was no difference between remifentanil and fentanyl. Remifentanil was effective, well tolerated and provided comparable haemodynamic stability to that of the hypnotic-based regimen. Over three times as many users rated analgesia-based sedation with remifentanil as very good or excellent in facilitating assessment of neurological function compared with the hypnotic-based regimen.

Conclusions

Analgesia-based sedation with remifentanil permitted significantly faster and more predictable awakening for neurological assessment. Analgesia-based sedation with remifentanil was very effective, well tolerated and had a similar adverse event and haemodynamic profile to those of hypnotic-based regimens when used in critically ill neuro-intensive care unit patients for up to 5 days.

Arrêt de la sédation en neuroréanimation

The reasons for sedation in neurointensive care can be divided into two main groups: (i) general indications, as for other intensive care patients, such as to allow the necessary treatments (therapeutic facilitation), controlling the states of agitations em leader; (ii) specific indications due to the neuro-physiologic effect of the sedatives: facilitation of the control of the intracranial pressure and lowering of the cortical excitability during the epileptic fits and thereby helping the recovery of the cerebral tissue and diminishing the secondary brain insults. It is important to remember that sedation is usually combined with the administration of opioids, which can potentiate the effect of the sedative drugs. The interruption of the sedation can be long- or short-termed. The definitive interruption is possible once the clinical and cerebral state of the patient does not justify any sedation, whereas the brief interruption allows a neurological reassessment. The amount of literature on sedation in intensive care is opposed to the few studies on neurointensive care: in January 2003, the American Society of Intensive Care has published recommendations for this topic without mentioning the interruption of sedation in neurointensive care patients. The aim of this article is to review the literature about the effects of the interruption of the sedation in neurointensive care patients.

Comparative tolerability of sedative agents in head-injured adults

Sedative agents are widely used in the management of patients with head injury. These drugs can facilitate assisted ventilation and may provide useful reductions in cerebral oxygen demand. However, they may compromise cerebral oxygen delivery via their cardiovascular effects. In addition, individual sedative agents have specific and sometimes serious adverse effects. This review focuses on the different classes of sedative agents used in head injury, with a discussion of their role in the context of clinical pathophysiology. While there is no sedative that has all the desirable characteristics for an agent in this clinical setting, careful titration of dose, combination of agents, and a clear understanding of the pathophysiology and pharmacology of these agents will allow safe sedative administration in head injury.

Population pharmacokinetics of clomethiazole and its effect on the natural course of sedation in acute stroke patients

AIMS

This analysis was performed to investigate the population pharmacokinetics of clomethiazole and its effect on the natural course of sedation in acute stroke patients using a nonlinear mixed effects modelling approach.

METHODS

One thousand five hundred and forty-six acute stroke patients (774 on active treatment) from 166 centres were included in three randomized, double-blind, placebo-controlled phase III efficacy and safety studies. A total dose of 68 mg kg(-1) clomethiazole edisilate was given as a three-phase i.v.-infusion over 24 h. Three blood samples were drawn from all patients to characterize the pharmacokinetics. Sedation was monitored throughout the entire treatment period and the degree of sedation was measured on a discrete ordinal scale with six levels. Models were fitted to the data using the software NONMEM.

RESULTS

Clomethiazole was characterized by a two-compartment pharmacokinetic model with interindividual variability in all structural parameters. For a patient weighing 75 kg, the average CL, V1, Q, and V2 was estimated to be 52.7 l h(-1), 82.5 l, 167 l h(-1) and 335 l, respectively. The interindividual variability in CL, V1, Q and V2 was estimated to be 48%, 53%, 42% and 54%, respectively. Increasing body weight and concomitant administration of liver enzyme inducing drugs were found to increase clearance (by 0.5 l h(-1) kg(-1) and 40%, respectively). Increasing weight also increased the volume of distribution (1.1 l kg(-1) for V1 and 4.7 l kg(-1) for V2). A six-category proportional odds model with a component including the natural course of sedation following placebo administration, a drug component (present or absent) and an interindividual variability component described the degree of sedation. Stroke severity as measured on the NIH-stroke scale on admission and drug treatment were the most important predictors of sedation, but a nonlinear increase in sedation with increasing age was also found. Increasing body weight increased the sedative drug effect.

CONCLUSIONS

The pharmacokinetics of clomethiazole were characterized in acute stroke patients and the analysis excluded several possible covariates of interest in drug development. The time course of sedation could be quantitatively described during the first 24 h following an acute stroke in the presence or absence of clomethiazole treatment.

Continuous nervous system monitoring, EEG, the bispectral index, and neuromuscular transmission

In critically ill patients, the central nervous system remains vulnerable to multiple insults including ischemia, hemorrhagic events, and encephalopathy. The peripheral nervous system is vulnerable in the setting of neuro-muscular blockade (NMB), related drug-drug interactions, and drug-clinical state interactions. Optimal assessment of the nervous system is done by means of the clinical neurological examination. In this manner, orientation, arousal, and responsiveness to stimulation provide feedback on focal and global stability of the central nervous system. Where clinical evaluation is compromised, such as with deep sedation and NMB, risk of undetected seizure activity, and/or progression of neurological injury increases dramatically. A patient receiving NMB risks breakthrough awareness and pain. Long-term complications of NMB including prolonged weakness or paralysis as well as post-traumatic stress dramatically increase morbidity and length of stay. Technologies such as electroencephalogram (EEG) and bispectral index (BIS trade mark ) monitoring are effective for assessing cerebral function as well as level of sedation or arousal, respectively, in patients with a compromised neurological assessment. Neuromuscular transmission (NMT) monitoring by means of peripheral nerve stimulation and assessment of the evoked response may be utilized, within the context of clinical assessment, to determine level of chemical paralysis and minimize dosing of NMB agents. This article explores utilization and differentiates technologies such as EEG, BIS, and NMT monitoring. Monitoring parameters are illustrated using a case study approach.

Sedation in neurointensive care: advances in understanding and practice

PURPOSE OF REVIEW

To evaluate the rationale and the pharmacologic options for sedating neurointensive care patients.

RECENT FINDINGS

Sedation is a fundamental element in the neurointensive care unit. Even if the sedative strategy in the neurointensive care unit shares the same general aims with intensive care, the characteristics of the patients in the neurointensive care unit pose other unique challenges and some specific indications. The primary aim of neurointensive care is to maintain adequate cerebral perfusion pressure, to control intracranial pressure, and to maintain an adequate mean arterial pressure. Reducing the brain's metabolic demand is an important treatment strategy, and analgesic and sedative agents are used to prevent undesirable increases in intracranial pressure. There are many different pharmacologic agents available, each with distinct advantages and disadvantages.

SUMMARY

The pharmacokinetic and pharmacologic effects of the available sedatives used in neurointensive care patients are reviewed.

S(+)-ketamine attenuates myogenic motor-evoked potentials at or distal to the spinal alpha-motoneuron

We investigated the effect of S(+)-ketamine on spinal cord evoked potentials (ESCPs) and myogenic motor-evoked potentials after electrical stimulation of the motor cortex in a rabbit model. This study was designed to characterize the relationship between ESCP characteristics and corresponding changes in compound muscle action potentials (CMAPs) derived from fore and hind limbs. Direct (D) and indirect (I) corticospinal volleys (ESCP) from the upper and lower thoracic spinal cord, recorded by two bipolar epidural electrodes, were assessed during IV administration of 0.02, 0.05, 0.1, and 0.2 mg. kg(-1) x min(-1) of S(+)-ketamine, each before and after neuromuscular blockade (0.4 mg/kg of cisatracurium), in 16 New Zealand White rabbits after single-pulse bipolar electrical stimulation of the motor cortex at 50 (threshold), 60, and 70 V. CMAP amplitudes at fore and hind limbs were significantly suppressed (P < 0.01) during infusion at 0.1 and 0.2 mL x kg(-1) x min(-1), whereas neither corresponding D- nor I-waves were altered. Similar findings were obtained during variation of stimulus amplitude (50-70 V). Multivariate regression analysis of CMAP amplitudes and various ESCP characteristics demonstrated no apparent interparametric association. These findings indicate that S(+)-ketamine modulates CMAP independent from corticospinal D- and I-wave-mediated facilitation at or distal to the spinal alpha-motoneuron.

IMPLICATIONS

S(+)-Ketamine combines several anesthetic properties suitable for total IV neuroanesthesia, including minimal effects on neurophysiological monitoring. Recording of neural and myogenic responses after electrical stimulation of the motor cortex indicates that S(+)-ketamine modulates myogenic motor-evoked potentials by a peripheral mechanism at or distal to the spinal alpha-motoneuron.

Critical care issues in stroke and subarachnoid hemorrhage

The outcomes of devastating neurological emergencies such as stroke and subarachnoid hemorrhage may be measurably improved by timely treatment in a neurointensive care unit (NICU). Optimal care requires a multidisciplinary approach, with attention to a wide range of treatment issues. This review examines the key therapeutic concerns in the NICU management of acute ischemic and hemorrhagic stroke and subarachnoid hemorrhage, including mechanical ventilation, blood pressure management, cardiac monitoring, intracranial pressure assessment, vasospasm, seizures, sedation, fluids, electrolytes, and nutrition. The discussion of mechanical ventilation includes rapid sequence induction and intubation, indication for intubation and extubation, and prognostic factors in mechanical ventilation. Differing blood pressure management concerns in hemorrhagic and ischemic events are discussed, and specific target blood pressures and pharmacologic interventions are reviewed. The discussion of cardiac monitoring includes concurrent stroke and cardiac ischemia and arrhythmias, cardiac imaging, anticoagulation, and vasopressor therapy. The importance, monitoring and management of cerebral blood flow and intracranial pressure (ICP) are discussed, and strategies for treatment of elevated ICP are outlined in detail. The discussion of vasospasm includes evaluation, prophylaxis, and treatment with medications, hypervolemic hemodilution, and angioplasty. Management of seizure and status epilepticus in stroke and subarachnoid hemorrhage are reviewed and current algorithms are presented. The management of fluids, electrolytes and enteral nutrition are also reviewed.