Treatment of intracranial hypertension. Analysis of 105 consecutive, continuous recordings of intracranial pressure

Improved Pressure Equalization Ratio Following Mannitol Administration in Patients With Severe TBI: A Preliminary Study of a Potential Bedside Marker for Response to Therapy

BACKGROUND

Performing a cerebrospinal fluid (CSF) drainage challenge can be used to measure the pressure equalization (PE) ratio, which describes the extent to which CSF drainage can equalize pressure to the height of the external ventricular drain and may serve as a correlate of cerebral edema. We sought to assess whether treatment with mannitol improves PE ratio in patients with severe traumatic brain injury (TBI) with elevated intracranial pressure (ICP).

METHODS

We studied consecutive patients with TBI and brain edema on computed tomography scan and an external ventricular drain (EVD), admitted to the neurointensive care unit. PE ratio, defined as ICP prior to CSF drainage minus ICP after CSF drainage divided by ICP prior to CSF drainage minus EVD height, was measured as previously described. Patients were treated with mannitol for raised ICP based on clinical indication and PE ratio measured before and after mannitol administration.

RESULTS

We studied 20 patients with severe TBI with raised ICP. Mean ICP prior to mannitol treatment was 29 ± 7 mm Hg. PE ratio rose substantially after mannitol treatment (0.62 ± 0.24 vs. 0.29 ± 0.20, p < 0.0001), indicating an improved ability to drain CSF and equalize ICP with the preset height of the EVD. The combination of mannitol and CSF drainage led to an improved reduction in ICP compared with that seen before mannitol therapy (11 ± 2 mm Hg vs. 6 ± 2 mm Hg, p < 0.01), and led to a decrease in ICP below the 20 mm Hg threshold in 77% of cases.

CONCLUSIONS

Treatment with mannitol leads to a substantial improvement in PE ratio that reflects the ability to achieve a greater decrease in ICP when CSF drainage is performed after mannitol administration. This preliminary study raises the possibility that PE ratio may be useful to follow response to therapy in patients with cerebral edema and raised ICP. Further studies to determine whether PE ratio may serve as an easily obtained and clinically useful surrogate marker for the extent of brain edema are warranted.

Perioperative Management of Severe Traumatic Brain Injury: What Is New?

PURPOSE OF THE REVIEW

Severe traumatic brain injury (TBI) continues to represent a global public health issue, and mortality and morbidity in TBI patients remain substantial. There are ongoing international collaborations to provide guidelines for perioperative care and management of severe TBI patients. In addition, new pharmacologic agents are being tested along with cognitive rehabilitation to improve functional independence and outcome in TBI patients. This review will discuss the current updates in the guidelines for the perioperative management of TBI patients and describe potential new therapies to improve functional outcomes.

RECENT FINDINGS

In the most recent guidelines published by The Brain Trauma Foundation, therapeutic options were reviewed based on new and revised evidence or lack of evidence. For example, changes and/or updates were made to the recommendations for the use of sedation and hypothermia in TBI patients, and new evidence was provided for the use of cerebrospinal fluid drainage as a first-line treatment for increased intracranial pressure (ICP). In addition to the guidelines, new 'multi-potential' agents that can target several mechanisms are being tested along with cognitive rehabilitation.

SUMMARY

The major goal of perioperative management of TBI patients is to prevent secondary damage. Therapeutic measures based on established guidelines and recommendations must be instituted promptly throughout the perioperative course to reduce morbidity and mortality.

Therapeutic Hypothermia Reduces Intracranial Pressure and Partial Brain Oxygen Tension in Patients with Severe Traumatic Brain Injury: Preliminary Data from the Eurotherm3235 Trial

Traumatic brain injury (TBI) is a significant cause of disability and death and a huge economic burden throughout the world. Much of the morbidity associated with TBI is attributed to secondary brain injuries resulting in hypoxia and ischemia after the initial trauma. Intracranial hypertension and decreased partial brain oxygen tension (PbtO2) are targeted as potentially avoidable causes of morbidity. Therapeutic hypothermia (TH) may be an effective intervention to reduce intracranial pressure (ICP), but could also affect cerebral blood flow (CBF). This is a retrospective analysis of prospectively collected data from 17 patients admitted to the Western General Hospital, Edinburgh. Patients with an ICP >20 mmHg refractory to initial therapy were randomized to standard care or standard care and TH (intervention group) titrated between 32°C and 35°C to reduce ICP. ICP and PbtO2 were measured using the Licox system and core temperature was recorded through rectal thermometer. Data were analyzed at the hour before cooling, the first hour at target temperature, 2 consecutive hours at target temperature, and after 6 hours of hypothermia. There was a mean decrease in ICP of 4.3±1.6 mmHg (p<0.04) from 15.7 to 11.4 mmHg, from precooling to the first epoch of hypothermia in the intervention group (n=9) that was not seen in the control group (n=8). A decrease in ICP was maintained throughout all time periods. There was a mean decrease in PbtO2 of 7.8±3.1 mmHg (p<0.05) from 30.2 to 22.4 mmHg, from precooling to stable hypothermia, which was not seen in the control group. This research supports others in demonstrating a decrease in ICP with temperature, which could facilitate a reduction in the use of hyperosmolar agents or other stage II interventions. The decrease in PbtO2 is not below the suggested treatment threshold of 20 mmHg, but might indicate a decrease in CBF.

Mannitol-enhanced delivery of stem cells and their growth factors across the blood-brain barrier

Ischemic brain injury in adults and neonates is a significant clinical problem with limited therapeutic interventions. Currently, clinicians have only tPA available for stroke treatment and hypothermia for cerebral palsy. Owing to the lack of treatment options, there is a need for novel treatments such as stem cell therapy. Various stem cells including cells from embryo, fetus, perinatal, and adult tissues have proved effective in preclinical and small clinical trials. However, a limiting factor in the success of these treatments is the delivery of the cells and their by-products (neurotrophic factors) into the injured brain. We have demonstrated that mannitol, a drug with the potential to transiently open the blood-brain barrier and facilitate the entry of stem cells and trophic factors, as a solution to the delivery problem. The combination of stem cell therapy and mannitol may improve therapeutic outcomes in adult stroke and neonatal cerebral palsy.

Hyperosmolar therapy for intracranial hypertension

The use of hyperosmolar agents for intracranial hypertension was introduced in the early 20th century and remains a mainstay of therapy for patients with cerebral edema. Both animal and human studies have demonstrated the efficacy of two hyperosmolar agents, mannitol and hypertonic saline, in reducing intracranial pressure via volume redistribution, plasma expansion, rheologic modifications, and anti-inflammatory effects. However, because of physician and institutional variation in therapeutic practices, lack of standardized protocols for initiation and administration of therapy, patient heterogeneity, and a paucity of randomized controlled trials have yielded little class I evidence on which clinical decisions can be based, most current evidence regarding the use of hyperosmolar therapy is derived from retrospective analyses (class III) and case series (class IV). In this review, we summarize the available evidence regarding the use of hyperosmolar therapy with mannitol or hypertonic saline for the medical management of intracranial hypertension and present a comprehensive discussion of the evidence associated with various theoretical and practical concerns related to initiation, dosage, and monitoring of therapy.

The role for osmotic agents in children with acute encephalopathies: a systematic review

BACKGROUND

Raised intracranial pressure (ICP) is known to complicate both traumatic and non-traumatic encephalopathies. It impairs cerebral perfusion and may cause death due to global ischaemia and intracranial herniation. Osmotic agents are widely used to control ICP. In children, guidelines for their use are mainly guided by adult studies. We conducted this review to determine the current evidence of the effectiveness of osmotic agents and their effect on resolution of coma and outcome in children with acute encephalopathy.

METHODS

We searched several databases for published and unpublished studies in English and French languages, between January 1966 and March 2009. We considered studies on the use of osmotic agents in children aged between 0 and 16 years with acute encephalopathies. We examined reduction in intracranial pressure, time to resolution of coma, and occurrence of neurological sequelae and death.

RESULTS

We identified four randomized controlled trials, three prospective studies, two retrospective studies and one case report. Hypertonic saline (HS) achieved greater reduction in intracranial pressure (ICP) compared to mannitol and other fluids; normal saline or ringer's lactate. This effect was sustained for longer when it was given as continuous infusion. Boluses of glycerol and mannitol achieved transient reduction in ICP. Oral glycerol was associated with lower mortality and neurological sequelae when compared to placebo in children with acute bacterial meningitis. HS was associated with lower mortality when compared to mannitol in children with non-traumatic encephalopathies.

CONCLUSION

HS appears to achieve a greater reduction in ICP than other osmotic agents. Oral glycerol seems to improve outcome among children with acute bacterial meningitis. A sustained reduction in ICP is desirable and could be achieved by modifying the modes and rates of administration of these osmotic agents, but these factors need further investigation.

The Role for Osmotic Agents in Children with Acute Encephalopathies: A Systematic Review

BACKGROUND

Raised intracranial pressure (ICP) is a common complication in children with acute encephalopathies. It compromises cerebral perfusion leading to ischaemia and may cause death when the brainstem is compressed during trans-tentorial herniation. Osmotic agents are widely used to control raised ICP. Their use in children is mainly guided by studies in adults.

OBJECTIVE

We carried out this review to determine the best available evidence of the effectiveness of various osmotic agents and their effect on resolution of coma and outcome (neurological sequelae and mortality) in children with acute encephalopathies.

SELECTION CRITERIA

We searched literature published between January 1966 and January 2008 on the use of osmotic agents in children aged between 0 and 16 years with acute encephalopathies.

SEARCH STRATEGY

We searched Medline, Cochrane Library, EMBASE, Cumulative Index to Nursing and Allied Health Literature and other databases for both published and unpublished literature.

RESULTS

We identified four randomized controlled trials (RCTs), three prospective observational studies, two retrospective studies and one case report. The use of hypertonic saline appeared to achieve greater reduction in ICP compared to mannitol, normal saline and ringer's lactate. This effect was sustained when it was given as a continuous infusion. Boluses of glycerol and mannitol achieved transient reduction in ICP. Use of repeated doses of oral glycerol was associated with lower mortality and neurological sequelae when compared to placebo in children with acute bacterial meningitis. Hypertonic saline was associated with lower mortality when compared to mannitol in children with non-traumatic encephalopathies.

DISCUSSION

All agents resulted in reduction of ICP, albeit transient in a number of occasions. A sustained reduction in ICP is desirable and could be achieved by modifying the modes and rates of administration, factors that need further investigation. Hypertonic saline appears to boost cerebral perfusion pressure, an important determinant of outcome in acute encephalopathies.

CONCLUSION

Hypertonic saline appears to achieve greater reduction in ICP than other osmotic agents. Oral glycerol seems to improve outcome among children with acute bacterial meningitis. However, the evidence is not sufficient to guide change of practice. More studies are needed to examine the safest and most efficacious concentrations of the various agents and the most effective routes and rates of administration of these agents.

Characterizing the dose-response relationship between mannitol and intracranial pressure in traumatic brain injury patients using a high-frequency physiological data collection system

Despite the widespread use of mannitol to treat elevated intracranial pressure (ICP), there is no consensus regarding the optimal dosage. The objective of this study was to retrospectively characterize the dose-response relationship between mannitol and ICP using data collected with a continuous high-frequency physiological data collection system. To this end, we measured ICP continuously in 28 patients with traumatic brain injury (TBI) who were given at least one dose of mannitol. Twenty TBI patients were given a total of 85 doses of 50 g of mannitol, and 18 patients were given 50 doses of 100 g. Some patients received both amounts. Cerebral perfusion pressure was maintained above 60 mm Hg. The average ICP was 22.0 +/- 10.6 mm Hg when mannitol was administered, fell immediately after dosing, and continued falling for approximately 30 min to 15.7 +/- 8.1 mm Hg across all patients. After 30 min, ICP was equal in the 100-g group (15.6 +/- 10.9) versus the 50-g group (15.7 +/- 6.3). However, at 100 min, ICP had increased in the 50-g group to nearly its initial value but was still lower in the 100-g group (18.6 +/- 7.6 vs. 14.2 +/- 6.7 mm Hg; p = 0.001). Osmotic agents such as mannitol have been used for decades to treat cerebral edema, but there has been no definitive quantitative information regarding the dosing of mannitol. In a large, retrospective study of high-frequency ICP data, we have quantitatively shown that mannitol's effect on ICP is dose-dependent and that higher doses provide a more durable reduction in ICP.

Management of complicated shunt infections: a clinical report

OBJECTIVES

The authors present their experience with a protocol for the treatment of patients with complicated shunt infections.

METHODS

Complicated shunt infections are defined for the purpose of this protocol as multiple compartment hydrocephalus, multiple organism shunt infection, severe peritonitis, or infections in other sites of the body. The initial treatment protocol for these patients was 3 weeks of intravenous antibiotic therapy and 2 weeks of twice daily intraventricular/intrashunt antibiotic therapy. Cerebrospinal fluid (CSF) cultures were monitored during therapy and obtained again 48 hours after completion. The shunt was completely replaced. Additionally, follow-up cultures were obtained in all patients 3-6 months after therapy was completed.

RESULTS

A cure of the infection was achieved in all patients as defined by negative cultures obtained at completion of antibiotic therapy and in follow-up studies. The follow-up period was 2-11 years (mean 4.4 +/- 2.5 years). The treatment protocol was modified in the patients treated after 1991, and 18 patients were treated with this modified treatment regime. In these patients, intraventricular antibiotics were administered only once daily for 14 days, and the CSF was cultured 24 hours after antibiotic therapy had been stopped instead of after 48 hours. The results were similar to those obtained with the initial protocol.

CONCLUSIONS

Based on their prospective nonrandomized series, the authors believe that patients with complicated shunt infections can be successfully treated with 2 weeks of intraventricular antibiotic therapy administered once daily, concurrent with 3 weeks of intravenous antibiotic therapy. This protocol reduces length of treatment and hospital stay, and avoids recurrence of infection.

Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial

BACKGROUND

Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia.

METHODS

Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, PaCO2 = 25 +/- 2 mm Hg) followed by normoventilation (PaCO2 = 37 +/- 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale.

RESULTS

Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (+/-SD) ICP during hyperventilation, 12.3 +/- 8.1 mm Hg, was lower than that during normoventilation, 16.2 +/- 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP.

CONCLUSIONS

In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.

Dose-response relationship of mannitol and intracranial pressure: a metaanalysis

OBJECTIVE

Brain edema can increase intracranial pressure (ICP), potentially leading to ischemia, herniation, and death. Edema and elevated ICP are often treated with osmotic agents to remove water from brain tissue. Mannitol is the osmotic diuretic most commonly used in the intensive care unit; however, despite its clinical importance, treatment protocols vary from center to center, and the dose-response relationship is not understood. The goal of this metaanalysis was to aggregate and analyze data from studies in which authors have described the dose-response relationship between mannitol and ICP.

METHODS

The authors identified 18 studies that quantitatively characterized the dose-response relationship of mannitol and ICP. We also examined study designs and mannitol administration protocols.

RESULTS

Meta-regression found a weak linear relationship between change in ICP (delta ICP) and dose (delta ICP = 6.6 x dose - 1.1; p = 0.27, R(2) = 0.05). The lack of statistical significance could reflect the variation in protocols among studies and the variation in patients both within and among studies. However, the authors found a highly significant difference (p < 0.001) in decrease in ICP when the initial ICP was higher or lower than 30 mm Hg. Nonlinear regression suggested that ICP decrease is greatest shortly after mannitol is given (R(2) = 0.63). Finally, the authors found that recent studies tend to include fewer patients and set a lower ICP threshold for mannitol administration but report more parameters of interest; the duration of mannitol's effect was the most frequently unreported parameter.

CONCLUSIONS

Despite its clinical importance, the determination of the mannitol dose-response curve continues to be challenging for many reasons. This metaanalysis highlights the need for a consensus of methods and results required to determine this important relationship.

Aggressive management of shunt infection: combined intravenous and intraventricular antibiotic therapy for twelve or less days

OBJECTIVE

This report is limited to patients with a single cerebrospinal fluid (CSF) shunt infected by a single organism, and compares two treatment protocols.

METHODS

In the initial protocol (1975-1991), patients underwent removal of the shunt system and received intravenous and intraventricular antibiotics. Intraventricular antibiotics were administered twice daily to those with external ventricular drainage. When CSF was cultured 48 h off all antibiotics and found to be sterile at 24 h of incubation, a new shunt was inserted. Follow-up CSF cultures were obtained in all patients between 1-6 months following placement of the new shunt.

RESULTS

There were 25 patients (ages 1 month to 16 years; mean +/- SD: 23 +/- 4.0 months). CSF obtained from the shunt yielded the following: Staphylococcus epidermidis (19), Staphylococcus aureus (2), Streptococcus species (2), Serratia marcescens (1), and Propionebacterium species (1). The duration of intravenous antibiotics was 7-12 days (mean +/- SD: 9.7 +/- 1.3 days), and intraventricular antibiotic therapy was 6.2 +/- 1.7 days. Total hospital stay was 15.2 +/- 2.3 days. The follow-up period was 7.7 +/- 3.6 years. Following the initial protocol in another 15 patients (1992-2004), the treatment regime was modified in that intraventricular antibiotics were administered once daily in patients with external ventricular drainage, and the CSF was cultured at 24 h off antibiotics, instead of 48 h. Results were similar to the initial protocol with respect to days of antibiotic therapy and hospital stay.

CONCLUSION

Based on our retrospective nonrandomized series, we believe patients with a single shunt and noncompartmentalized hydrocephalus can be successfully treated without a prolonged antibiotic course and lengthy hospital stay.

Osmotherapy in neurocritical care

Osmotherapy is the mainstay in the medical management of cerebral edema with or without elevations in intracranial pressure. Several osmotic agents have been utilized in clinical practice over the past five decades in a variety of brain injury paradigms. The over-riding premise for their beneficial effects has been via egress of water from the brain into the vascular compartment. In addition, many of these agents have beneficial extraosmotic properties that portend their use in cerebral resuscitation and treatment of cerebral edema. Although there is a paucity of large, randomized clinical trials that compare various osmotic agents, data are emerging from prospective clinical case series. This article provides a historical perspective of osmotherapy, examines characteristics of osmotic agents, and discusses caveats in their use in the clinical setting. Furthermore, this review highlights the utility of osmotic agents as tools to understand emerging mechanistic concepts in the evolution of brain edema, which are yielding important data of translational significance from laboratory-based research.

Mannitol for acute stroke

BACKGROUND

Mannitol is an osmotic agent and a free radical scavenger which might decrease oedema and tissue damage in stroke.

OBJECTIVES

To test whether treatment with mannitol reduces short and long-term case fatality and dependency after acute ischaemic stroke or intracerebral haemorrhage (ICH).

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (searched December 2006), MEDLINE (1966 to January 2007), the Chinese Stroke Trials Register (searched November 2006), the China Biological Medicine Database (searched December 2006) and the Latin-American database LILACS (1982 to December 2006). We also searched the database of Masters and PhD degree theses at Sao Paulo University (searched January 2007), and neurology and neurosurgery conference proceedings in Brazil from 1965 to 2006. In an effort to identify further published, ongoing and unpublished studies we searched reference lists and contacted authors of published trials.

SELECTION CRITERIA

We included randomised controlled trials comparing mannitol with placebo or open control in patients with acute ischaemic stroke or non-traumatic intracerebral haemorrhage.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed quality, extracted data, and performed the data analysis.

MAIN RESULTS

Three small trials, involving 226 participants, were included. One trial included patients with presumed ischaemic stroke without computerised tomography (CT) verification, and the other two trials included patients with CT-verified ICH. Data on the primary outcome measure (death and dependency) were not available in any of the trials. Death and disability could be calculated in the larger ICH trial without differences between the mannitol and control groups. Case fatality was not reported in the trial of ischaemic stroke. Case fatality did not differ between the mannitol and control groups in the ICH trials. Adverse events were either not found or not reported. The change in clinical condition was reported in two trials, and the proportion of those with worsening or not improving condition did not differ significantly between mannitol-treated patients and controls. Based on these three trials neither beneficial nor harmful effects of mannitol could be proved. Although no statistically significant differences were found between the mannitol-treated and control groups, the confidence intervals for the treatment effect estimates were wide and included both clinically significant benefits and clinically significant harms as possibilities.

AUTHORS' CONCLUSIONS

There is currently not enough evidence to support the routine use of mannitol in acute stroke patients. Further trials are needed to confirm or refute whether mannitol is beneficial in acute stroke.

Expression of the Water Channel Protein Aquaporin-9 in Malignant Brain Tumors

Recently, many studies seen concerning the expression and distribution of aquaporins and K channels in the central nervous system, and their physiological and pathophysiologic roles in water and ion homeostasis. Whereas most data were collected on aquaporin-4 (AQP4) in astrocytes, only little attention was paid to AQP9 which is a water channel transporting glycerol, mannitol, and urea as well. This is the first study describing AQP9 in human brain and human brain tumors. For comparison, we also investigated the immunohistochemical distribution of AQP9 in the rat glioma RG2. Whereas in the normal rat brain AQP9 is only weakly expressed by astrocytes, the anti-AQP9 immunoreactivity was found to be increased at the tumor border, but not within the tumor. In contrast, in human glioblastoma, most glioma cells throughout the tumor revealed a strong anti-AQP9 immunoreactivity across the whole surface of the cell. In the discussion, the increase of the anti-AQP9 immunoreactivity in glioma cells is suggested to reflect an upregulation and to counteract the glioma-associated lactic acidosis by clearance of glycerol and lactate from the extracellular space. In addition, the increased level of AQP9 immunoreactivity could be involved in the energy metabolism of the glioma and/or surrounding neuronal cells.

Medical management of cerebral edema

✓Cerebral edema is frequently encountered in clinical practice in critically ill patients with acute brain injury from diverse origins and is a major cause of increased morbidity and death in this subset of patients. The consequences of cerebral edema can be lethal and include cerebral ischemia from compromised regional or global cerebral blood flow (CBF) and intracranial compartmental shifts due to intracranial pressure gradients that result in compression of vital brain structures. The overall goal of medical management of cerebral edema is to maintain regional and global CBF to meet the metabolic requirements of the brain and prevent secondary neuronal injury from cerebral ischemia. Medical management of cerebral edema involves using a systematic and algorithmic approach, from general measures (optimal head and neck positioning for facilitating intracranial venous outflow, avoidance of dehydration and systemic hypotension, and maintenance of normothermia) to specific therapeutic interventions (controlled hyperventilation, administration of corticosteroids and diuretics, osmotherapy, and pharmacological cerebral metabolic suppression). This article reviews and highlights the medical management of cerebral edema based on pathophysiological principles in acute brain injury.

The effect of intravenous fluid replacement on the response to mannitol in experimental cerebral edema: an analysis of intracranial pressure, serum osmolality, serum electrolytes, and brain water content

Albino rabbits that had undergone a cryogenic insult over the left parieto-occipital cortex were analyzed for serum osmolality, serum electrolytes, brain water content, and intracranial pressure (ICP) following either a baseline infusion of intravenous (i.v.) fluid (45 mL total) for 3 hours or above-maintenance isotonic saline (73.5 +/- 12 mL or 90.5 +/- 1.5 mL) and mannitol therapy. The subgroups were compared amongst themselves and to sham-operated controls. Serum osmolality was elevated in the higher-dose mannitol subgroup compared with maintenance i.v. fluids subgroup (1 g/kg/h vs 1 g/kg/3 h; p < 0.05), accompanied by an insignificant reduction of serum sodium. A significant reduction in brain water in the injured left hemisphere was seen following high-dose mannitol in the subgroup that received less i.v. (maintenance) fluids than the group that received above-maintenance i.v. fluids (p < 0.025). No reduction in brain water was seen in the subgroup that received above-maintenance i.v. fluids (non-treated groups). Reduction of ICP was not found in the lower mannitol dose group. We conclude that the ability of mannitol to reduce cerebral edema is related to the total amount of i.v. fluid replacement. This implies that the amount of i.v. crystalloid fluid that is administered to patients with cerebral edema and raised ICP requiring mannitol for control needs to be carefully monitored.

Sugar Solutions Used In Resuscitation

Although recent studies have shown that the timing of volume replacement deserves careful consideration (56), which fluid to use is less clear, with the perennial debate of crystalloid v colloid and now colloid v colloid still unresolved. This review has examined three sugar solutions, two colloids and one crystalloid. In general, all three agents are unhelpful in the immediate resuscitation of hypovolaemic trauma by virtue of a combination of pathophysiology and side effects. Dextran solutions and mannitol are useful in specific situations.

Cerebral pathophysiology and critical care neurology: basic hemodynamic principles, cerebral perfusion, and intracranial pressure

Pediatric neurologic intensive care differs from standard pediatric intensive care in two important respects. First, the diagnosis, monitoring, and management of problems related to disorders of cerebral perfusion and intracranial pressure (ICP) are central to nearly all of pediatric neurologic and neurosurgical intensive care. Second, various clinical problems normally encountered in the intensive care unit (ICU) have additional implications when associated with neurologic disease. Regardless of the cause, treatment should be undertaken as expeditiously as possible and should be based on the principles of resuscitation, reducing the volume of the intracranial contents, and reassessment. This chapter aims to outline some basic principles underlying the diagnosis and management of elevated ICP in children.

Post-emergency department management of stroke

All stroke patients ideally should be admitted to a stroke unit in which personnel are familiar with strategies for taking care of stroke patients. Prevention of worsening cerebral ischemia by appropriate blood pressure and serum glucose management, fever control, and supplemental oxygen for hypoxemic patients is recommended. Recognition of common complications, such as aspiration pneumonia and deep venous thrombosis, highlights the need for swallowing evaluation and the use of pneumatic compression devices or subcutaneous heparin. Patients should be monitored closely for deterioration in their neurologic status and should have complications appropriately addressed. After evaluation of stroke etiology, appropriate secondary stroke prophylaxis should be selected and initiated before hospital discharge.

Management of head trauma

Traumatic brain injury (TBI) is a major cause of disability and death in most Western nations and consumes an estimated $100 billion annually in the United States alone. In the last 2 decades, the management of TBI has evolved dramatically, as a result of a more thorough understanding of the physiologic events leading to secondary neuronal injury as well as advances in the care of critically ill patients. However, it is likely that many patients with TBI are not treated according to current treatment principles. This article presents an overview of the current management of patients with TBI.

Mannitol for acute stroke

BACKGROUND

Mannitol is an osmotic agent and a free radical scavenger so it might decrease oedema and tissue damage in stroke.

OBJECTIVES

To test whether treatment with mannitol reduces short and long-term case fatality and dependency after acute ischaemic stroke or cerebral parenchymal haemorrhage.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Specialised Trials Register. In addition to this, supplementary MEDLINE searches were performed. The Chinese Stroke Trials Register was checked and the Latin-American databank LILACS was searched with the search term MANNITOL and its variations in the Portuguese and Spanish languages. A search was performed of Masters and Ph.D. degree theses in the databank of Sao Paulo University, and in abstracts of medical congresses on neurology and neurosurgery from 1965 to 1997 in Brazil.

SELECTION CRITERIA

Truly randomised unconfounded clinical trials comparing the effect of mannitol with placebo or open control in patients with acute ischaemic stroke or parenchymal haemorrhage were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected the trials to be included in the review. After reaching an agreement on which trials to include, two of the reviewers extracted data from the trials and performed the data analysis. Accuracy of data extraction was checked by comparing the results. Included trials were tabulated for methodological quality including the method of randomisation and blinding, and stating if CT was performed, if patients were lost to follow-up and if intention-to-treat analysis was performed. Data synthesis and analysis was performed using the Cochrane Review Manager software.

MAIN RESULTS

Only one trial fulfilled the inclusion criteria. The number of included patients was small (36 treated and 41 controls) and the follow up was short. Neither beneficial nor harmful effects of mannitol could be proved. Case fatality, the proportion of dependent patients at the end of the follow up and side effects were not reported and were not available from the investigators. The planned outcome analyses and sensitivity analyses could not be performed due to lack of appropriate trials.

REVIEWER'S CONCLUSIONS

There is currently not enough evidence to decide whether the routine use of mannitol in acute stroke would result in any beneficial or harmful effect. The routine use of mannitol in all patients with acute stroke is not supported by any evidence from randomised controlled clinical trials. Further trials are needed to confirm or refute the routine use of mannitol in acute stroke.

Cochrane report: A systematic review of mannitol therapy for acute ischemic stroke and cerebral parenchymal hemorrhage

BACKGROUND

Mannitol was reported to decrease cerebral edema associated with tissue damage and is used to treat acute stroke in many countries.

SUMMARY OF REVIEW

We tested whether there is any evidence from unconfounded randomized clinical trials that treatment with mannitol reduces short- and long-term case fatality and dependency if administered after ischemic stroke or cerebral parenchymal hemorrhage. Trials were identified by the standard search strategy of the Cochrane Collaboration Stroke Review Group. A supplementary MEDLINE search was performed, and the Chinese Stroke Trials Register and the Latin-American databank LILACS were checked. A search was performed of master's and PhD degree theses in the databank of Sao Paulo University and in abstracts of medical congresses on neurology and neurosurgery during 1965-1997 in Brazil. Investigators were contacted for unpublished information. Only truly randomized unconfounded clinical trials were eligible for inclusion. Two of the reviewers independently extracted data from the trials. Data synthesis and analysis was performed with the use of the Cochrane Review Manager software (RevMan version 4.0.4).

CONCLUSIONS

Only 1 trial fulfilled the inclusion criteria. The number of included patients was small, and the follow-up was short. Case fatality, the proportion of dependent patients, and side effects were not reported and were not available from the investigators. As a result of lack of appropriate randomized trials, currently no conclusion can be drawn on the effects of mannitol in acute stroke. The routine use of mannitol in all patients with acute stroke is not supported by evidence from randomized controlled clinical trials.

The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Use of mannitol

There are two "class 1" studies, and one "class 2" study, and a large body of "Class 3" data, which can be used to support mannitol. The evidence supporting use of mannitol for ICP control is sufficiently strong to warrant guideline status. Mannitol is effective in reducing ICP, and its use is recommended as a guideline in the management of traumatic intracranial hypertension. Serum osmolalities >320 mOsm and hypovolemia should be avoided. There is some data to suggest that bolus administration is preferable to continuous infusion.

Cerebral Edema: Hypertonic Saline Solutions

Our experience, and that of others, suggests that hypertonic saline solution therapy reduces intracranial pressure and lateral displacement of the brain in patients with cerebral edema. This therapy appears most promising in patients who have head trauma or postoperative cerebral edema. Studies comparing hypertonic saline therapy with conventional therapies are limited. Additional randomized studies are needed to determine its safety and optimum duration of benefit and to determine the lesions most likely to be improved. To date, the cost effectiveness of hypertonic saline therapy is unknown. Caution is advised regarding its use until the results of more definitive trials investigating its efficacy and safety are known.

The use of mannitol in severe head injury. Brain Trauma Foundation

Mannitol is effective in reducing ICP, and we recommend its use in the management of traumatic intracranial hypertension. Serum osmolalities greater than 320 mOSsm/L and hypovolemia should be avoided. Some data suggest that bolus administration is preferable to continuous infusion.

Induced hypothermia in intensive care medicine

Induced hypothermia as adjunctive therapy has been the subject of considerable research interest and debate for over fifty years. Recently the first prospective randomized controlled trials were undertaken in humans with severe traumatic brain injury, with supportive results. Another prospective controlled study of induced hypothermia in severe septic adult respiratory distress syndrome also suggested improved outcome. Other studies in patients with anoxic brain injury have been suggested following promising findings in animal models. There have been anecdotal reports of the use of induced hypothermia in a wide range of other neurological injuries. There are significant physiological changes during induced hypothermia, particularly affecting the cardiovascular system. In addition, hypokalaemia, prolonged clotting times and neutropenia may occur. The evidence that induced hypothermia may be hazardous is mostly drawn from the literature on accidental hypothermia occurring in trauma, or patients with sepsis. It is likely that further trials will be conducted and if benefit is confirmed, induced hypothermia may become more widely used in selected patients in the intensive care unit.

Urgent laparotomy versus emergency craniotomy for multiple trauma with head injury patients

In blunt multiple trauma (MT) with head injury (HI) patients, it is difficult to decide whether to proceed with immediate laparotomy or craniotomy. In August 1989, abdominal ultrasonography (US) using a simple US scoring system was introduced for MT and HI patients as an initial rapid screening procedure. In MT and HI patients with a US score > or = 3 (n = 14), urgent laparotomy was the procedure of first choice. However, immediate head CT scan, then emergency craniotomy, may be justified in hemodynamically stable MT and HI patients with a US score < 3 (n = 98). Appropriate decision making can be applied to decide which procedure is most exigent.

Hypothermia in acute blunt head injury

Mild to moderate hypothermia has been employed since the 1940s in the treatment of acute blunt head trauma. The utility of hypothermia in ischemic injury has been confirmed, by both animal studies and clinical experience, in cardiovascular and neurological surgery. In blunt injury, though, only one prospective, randomized study has shown a statistically significant improvement in long term outcome. Clinical experience, animal data, proposed mechanisms, technical considerations, and potential risks are reviewed. Hypothermia remains controversial in the setting of blunt head injury but may prove to be a useful treatment modality.

Relative risks of ventriculostomy infection and morbidity

Ventricular catheter placement is a common procedure for the management of increased intracranial pressure. Hypotheses regarding the etiology of infection of catheters center on two alternative assumptions: 1) contamination leading to infection occurs at the time of catheter insertion, implying that catheter duration has minimal effect on infection risk; and 2) infection of catheters derives from catheter contamination after insertion, suggesting that duration of catheter use may significantly affect infection risk. We have studied the relative complication rate of ventricular catheter insertions using a retrospective approach (n = 161 patients and 253 catheter insertion procedures). The overall infection rate was 4.1%, but the daily infection hazard increased exponentially with time, to a maximum daily rate of 10.3% by day 6 of catheter insertion. This increasing risk appears most consistent with the second hypothesis. The risk of non-infectious complications was 5.6%, including hemorrhagic occurrences and misplacement severe enough to require a new catheter insertion. The daily hazard of infection approximately equalled the non-infectious risk of routine catheter replacement by day 5. Additional prospective data on the daily risk of CSF infection and the appropriateness of antibiotic prophylaxis either at the time of ventricular catheter insertion or continued through the catheter's presence may be required to both definitively identify which hypothesis of infection risk is correct and whether antibiotics can significantly ameliorate this risk.

Sterilisation of implantable devices

The pathogenesis and rates of infection associated with the use of a wide variety of implantable devices are described. The multi-factorial nature of post-operative periprosthetic infection is outlined and the role of sterilisation of devices is explained. The resistance of bacterial spores is highlighted as a problem and a full description is given of the processes of sterilisation by heat, steam, ethylene oxide, low temperature steam and formaldehyde, ionising radiation and liquid glutaraldehyde. Sterility assurance and validation are discussed in the context of biological indicators and physical/chemical indicators. Adverse effects upon the material composition of devices and problems of process control are listed. Finally, possible optimisations of the ethylene oxide process and their potential significance to the field of sterilisation of implants is explored.

Acute subdural haematoma in adults: an analysis of outcome in comatose patients

The authors analysed a series of 200 adult patients admitted to the Department of Neurosurgery, Medical University of Lódź with a diagnosis of acute subdural haematoma (ASDH). 63% of them were surgically treated within the first 4 hours after head injury, the others were operated on 4 to 16 hours after trauma. All patients had GCS below 10 for the whole time period from trauma to surgery. Younger patients 18-30 year old had lower mortality-25%, while patients above 50 revealed 75% mortality. Analysis of operative timing and outcome, no benefit revealed when surgery was performed within first 4 hours. However, the patients operated on later than 4 hours after trauma had smaller midline shift and less pronounced brain contusion. It must be taken into account that some patients who could benefit from early surgery-those with quickly developing haematomas and intracranial hypertension-had no chance to arrive and died in peripheral hospitals. Despite our results we advocate an urgent evacuation of haematoma, as early as possible after trauma. Significant correlation was found between midline shift, cerebral contusion on CT scans and results of surgery. Patients with bigger midline shift or presence of focal cerebral contusion revealed higher mortality and worse outcome than patients with smaller shift and no cerebral contusion visible on CT pictures.

Effects of acute isotonic saline administration on serum osmolality, serum electrolytes, brain water content and intracranial pressure

Albino rabbits who had undergone a cryogenic insult over the left parieto-occipital cortex 24 hours previously were analyzed for serum osmolality, serum electrolytes, brain water content, intracranial pressure (ICP), following a 3 hour baseline intravenous infusion of above maintenance isotonic saline, and compared to sham operated controls. In the acute setting there was no difference in the serum osmolality and electrolytes between the subgroups. There was a significant increase in the water content of the white matter of the left hemisphere in the cold lesion group when compared to sham operated controls. Despite the intravenous fluid challenge, the ICP did not rise during the 3 hour experimental trial when compared to pre-trial values. It is concluded that in the acute setting an isotonic fluid load is compensated without significant disturbances of the above measured parameters, and should not alter therefore intracranial dynamics per se, in acute resuscitation measures following brain insults.

Management of intracranial hypertension

Intracranial hypertension is the final common denominator of morbidity and mortality for diverse neurologic problems, and its proper treatment requires the heuristic application of the available therapeutic alternatives when the clinical situation and patient's prognosis warrants treatment. The initial therapeutic focus for ICP reduction should be control of factors that may aggravate intracranial hypertension such as inappropriate head and body position, elevated body temperature, pain, noxious stimuli, elevated airway pressure, elevated blood pressure, seizures, and hypotonic intravenous fluids. The appropriate conventional therapies (e.g., hyperventilation, osmotic agents, sedatives, barbiturates, and cerebrospinal fluid removal) should be selected based on the details of each individual case. Surgical removal of intracranial mass lesions may be indicated in some circumstances, particularly for intractable intracranial hypertension and progressive, severe brain tissue shifts.

Aggravation of vasogenic cerebral edema by multiple-dose mannitol

The authors investigated the pharmacokinetics of mannitol administered for treatment of vasogenic cerebral edema. A cortical cold injury was produced in 23 cats maintained under general anesthesia for 5 or 21 hours. Control animals received no mannitol, while treatment groups received either a single dose or five doses administered at 4-hour intervals of 0.33 gm/kg radiolabeled mannitol. Liquid scintillation counting was carried out to determine the concentrations of mannitol in the cerebral tissue, cerebrospinal fluid, plasma, and urine. Cerebral water content and linear progression of edema were also measured. Rapid plasma clearance prevented accumulation of mannitol after multiple intravenous injections, as 84% +/- 2% (mean +/- standard error of the mean) of the infused mannitol was excreted through the urine. However, there was progressive accumulation of mannitol within the cerebral tissue, especially in the edematous white matter where it reached a level of 0.33 +/- 0.03 mg/gm after five doses, exceeding the trough plasma concentrations by a ratio of 2.69:1. Water content measurement showed that a single dose of mannitol failed to reduce cerebral water content or edema progression at 4 hours postinjection, while multiple doses produced a 3% increase in water content in edematous regions (p greater than 0.0003). The results of this study demonstrated a reversal of the osmotic concentration gradient between edematous brain and plasma following multiple mannitol injections, associated with exacerbation of vasogenic cerebral edema.

Resuscitation fluid for a patient with head injury and hypovolemic shock

The resuscitation of a patient with severe closed head injury and hypovolemic shock is a commonly encountered clinical scenario. The optimal resuscitation formula remains controversial. Aggressive use of crystalloid solutions may worsen brain injury. Early use of mannitol or hypertonic agents may worsen hemorrhage and shock. The optimal approach to the resuscitation of a patient with head trauma and hypovolemic shock is reviewed and discussed. Recent experimental evidence suggests that the early inclusion of an agent such as mannitol in the resuscitation formula may be appropriate despite the evidence of shock. However, the controversy remains unresolved.

Use of mannitol during neurosurgery: interpatient variability in the plasma and CSF levels

An i.v. infusion of mannitol was given over 15 min to 12 patients before they underwent intracranial surgery under general anesthesia. Samples of blood, CSF and urine were taken over 4 h. Mannitol disappeared from plasma in a bi-exponential manner. The mean maximal plasma concentration was 4.08 mg/ml at 15 min, and at 4 h it had declined to 0.53 mg/ml. The mean distribution rate constant was 11.2 h-1, corresponding to a plasma distribution half-life of 0.11 h. The mean elimination rate constant was 0.41 h-1, the plasma half-life was 2.2 h, the central distribution volume was 16.3 l, and total plasma clearance was 100.4 ml/min. The mean concentration of mannitol in CSF during the 4 h period increased up to 0.10 mg/ml. There were marked interindividual differences in the concentration ratio blood/CSF, and the CSF concentration varied 7.5 fold between patients. Optimal use of mannitol during neurosurgery requires further prolonged study of its pharmacokinetics.

Complications due to prolonged ventricular fluid pressure recording

All complications in a consecutive series of 648 patients subjected to prolonged recording of the ventricular fluid pressure (VFP) during 1982-1986 were registered and analysed. The procedure did not cause permanent symptoms or deficits in any case except for one haemorrhagic complication. Definite infections caused by the VFP recording were found in 4.3% of the 540 patients (83%) surviving their disease or lesion, and in 1.9% in non-survivors. These infections were almost exclusively registered in patients treated with prolonged drainage of hemorrhagic ventricular fluid, while definite infections in other patients were found in only 1.3%. Most infections were caused by Staphylococcus epidermidis and all infections could be treated successfully. Infection did not cause or contribute to the lethal outcome in any case. In 60% of the cases with infectious complications laboratory signs of ventriculitis occurred after a surgical revision of the ventriculostomy. The duration of VFP recording was of subordinate importance for the development of infection. In 13 patients (1.9%) during the studied period a reliable VFP recording was not obtained, a fact that points to the need for alternative methods in a minority of patients with elevated intracranial pressure. It is concluded that complications caused by VFP recording can be kept at an acceptably low frequency in patients without haemorrhagic cerebrospinal fluid demanding long-term drainage.

Effect of mannitol on cerebral blood flow and cerebral perfusion pressure in human head injury

Patients with severe head injury frequently have evidence of elevated intracranial pressure (ICP) and ischemic neuronal damage at autopsy. Mannitol has been used clinically to reduce ICP with varying success, and it is possible that it is more effective in some types of head injury than in others. The aim of the present study was to determine the effect of mannitol on ICP, cerebral perfusion pressure (CPP), and cerebral blood flow (CBF) in patients with severe head injury, and to discover if these effects differed in different types of injury. Measurements of CPP, ICP, and CBF were made in 55 patients with severe head injury. In general, the resting level of CBF was higher in patients with diffuse injury (mean 50.2 ml/100 gm/min) than in those with focal injury (mean 39.8 ml/100 gm/min). Mannitol consistently reduced ICP and increased CPP and CBF by 10 to 20 minutes after infusion. The lowest flows (31.8 ml/100 gm/min) were recorded from the most damaged hemispheres of patients with focal injuries and elevated ICP. The baseline levels of flow did not correlate with ICP, CPP, Glasgow Coma Scale score, or outcome. Only four of the 55 patients had a CBF of less than 20 ml/100 gm/min in either or both hemispheres. The few low CBF's in this and other studies may reflect the steady-state conditions under which measurements are made in intensive care units, and that these patients have entered a phase of reperfusion.