The effects of dextrose infusion and head position on neurologic outcome after complete cerebral ischemia in primates: examination of a model

Iatrogenic air embolism: pathoanatomy, thromboinflammation, endotheliopathy, and therapies

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

Effects of Single Dose of Dexamethasone on Perioperative Blood Glucose Levels in Patients Undergoing Surgery for Supratentorial Tumors - An Observational Study

Introduction:

Dexamethasone is commonly administered in intracranial tumors to reduce the cerebral edema. Its administration may be associated with hyperglycemia. The primary objective of this study was to study the magnitude of rise in blood sugar levels following the administration of a single 10 mg dose of dexamethasone.

Methods:

Seventy patients who underwent various neurosurgical procedures were enrolled in the study. Group D (n = 35 undergoing surgery for intracranial tumors) were administered injection dexamethasone 10 mg while as Group P (n = 35 undergoing surgery for subarachnoid hemorrhage) received placebo. Blood samples were obtained through the arterial line at baseline (before dexamethasone administration), 60, 120, 180, and 240 min after the dexamethasone administration and blood glucose concentrations noted.

Results:

Glucose concentrations were significantly increased in patients who received dexamethasone compared with those who received placebo (P < 0.05). Blood glucose concentrations at different time intervals were greater when compared with the baseline blood sugar levels in both the placebo and dexamethasone group (P < 0.05). The arterial blood glucose concentration in those who received 10 mg dexamethasone (n = 35) increased from 95.29 ± 13.69 mg.dl⁻¹ to 139.97 ± 10.34 mg.dl⁻¹ over 4 h, compared with a change from 94.74 ± 10.05 mg.dl⁻¹ to 122.34 ± 10.68 mg.dl⁻¹ in those who received placebo (n = 35) (P < 0.05).

Conclusion:

The administration of a single intravenous dose of 10-mg dose dexamethasone caused a significant increase in the blood glucose concentrations at different point intervals when compared with the placebo over a 4-h period. We recommend intensive monitoring of the blood sugar levels during the intraoperative period to prevent the development of severe hyperglycemia and its associated complications.

Development of a Stand-Alone Independent Graphical User Interface for Neurological Disease Prediction with Automated Extraction and Segmentation of Gray and White Matter in Brain MRI Images

This research presents an independent stand-alone graphical computational tool which functions as a neurological disease prediction framework for diagnosis of neurological disorders to assist neurologists or researchers in the field to perform automatic segmentation of gray and white matter regions in brain MRI images. The tool was built in collaboration with neurologists and neurosurgeons and many of the features are based on their feedback. This tool provides the user automatized functionality to perform automatic segmentation and extract the gray and white matter regions of patient brain image data using an algorithm called adapted fuzzy c-means (FCM) membership-based clustering with preprocessing using the elliptical Hough transform and postprocessing using connected region analysis. Dice coefficients for several patient brain MRI images were calculated to measure the similarity between the manual tracings by experts and automatic segmentations obtained in this research. The average Dice coefficients are 0.86 for gray matter, 0.88 for white matter, and 0.87 for total cortical matter. Dice coefficients of the proposed algorithm were also the highest when compared with previously published standard state-of-the-art brain MRI segmentation algorithms in terms of accuracy in segmenting the gray matter, white matter, and total cortical matter.

Importance of Perioperative Blood Glucose Management in Cardiac Surgical Patients

Tight blood glucose control has become a therapeutic goal for anesthetic management of patients undergoing cardiovascular surgery. We discuss the evidence for a link between blood glucose levels and rates of morbidity and mortality in cardiac surgical patients in the intensive care unit. Hyperglycemia per se has been associated with higher rates of deep wound infection, neurologic, renal, and cardiac complications following surgery, as well as longer intensive care unit stay. We review the specifics of glucose management in patients undergoing cardiac surgery and hypothermic cardiopulmonary bypass, including the role that insulin may play in regulating blood glucose levels intraoperatively and the relationship between insulin and outcome.

Glucose and the injured brain-monitored in the neurointensive care unit

Brain has a continuous demand for energy that is met by oxidative metabolism of oxygen and glucose. This demand is compromised in the injured brain and if the inadequate supply persists it will lead to permanent tissue damage. Zero values of cerebral glucose have been associated with infarction and poor neurological outcome. Furthermore, hyperglycemia is common in patients with neurological insults and associated with poor outcome. Intensive insulin therapy (IIT) to control blood glucose has been suggested and used in neurointensive care with conflicting results. This review covers the studies reporting on monitoring of cerebral glucose with microdialysis in patients with traumatic brain injury (TBI), subarachnoid hemorrhage (SAH) and ischemic stroke. Studies investigating IIT are also discussed. Available data suggest that low cerebral glucose in patients with TBI and SAH provides valuable information on development of secondary ischemia and has been correlated with worse outcome. There is also indication that the location of the catheter is important for correlation between plasma and brain glucose. In conclusion considering catheter location, monitoring of brain glucose in the neurointensive care not only provides information on imminent secondary ischemia it also reveals the effect of peripheral treatment on the injured brain.

Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association

PURPOSE

The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

A formal literature search of MEDLINE (November 1, 2006, through May 1, 2010) was performed. Data were synthesized with the use of evidence tables. Writing group members met by teleconference to discuss data-derived recommendations. The American Heart Association Stroke Council's Levels of Evidence grading algorithm was used to grade each recommendation. The guideline draft was reviewed by 7 expert peer reviewers and by the members of the Stroke Council Leadership and Manuscript Oversight Committees. It is intended that this guideline be fully updated every 3 years.

RESULTS

Evidence-based guidelines are presented for the care of patients presenting with aSAH. The focus of the guideline was subdivided into incidence, risk factors, prevention, natural history and outcome, diagnosis, prevention of rebleeding, surgical and endovascular repair of ruptured aneurysms, systems of care, anesthetic management during repair, management of vasospasm and delayed cerebral ischemia, management of hydrocephalus, management of seizures, and management of medical complications.

CONCLUSIONS

aSAH is a serious medical condition in which outcome can be dramatically impacted by early, aggressive, expert care. The guidelines offer a framework for goal-directed treatment of the patient with aSAH.

[Managing the post-cardiac arrest syndrome. Directing Committee of the National Cardiopulmonary Resuscitation Plan (PNRCP) of the Spanish Society for Intensive Medicine, Critical Care and Coronary Units (SEMICYUC)]

Since the advent of cardiopulmonary resuscitation more than 40 years ago, we have achieved a return to spontaneous circulation in a growing proportion of patients with cardiac arrest. Nevertheless, most of these patients die in the first few days after admission to the intensive care unit (ICU), and this situation has not improved over the years. Mortality in these patients is mainly associated to brain damage. Perhaps recognizing that cardiopulmonary resuscitation does not end with the return of spontaneous circulation but rather with the return of normal brain function and total stabilization of the patient would help improve the therapeutic management of these patients in the ICU. In this sense, the term cardiocerebral resuscitation proposed by some authors might be more appropriate. The International Liaison Committee on Resuscitation recently published a consensus document on the "Post-Cardiac Arrest Syndrome" and diverse authors have proposed that post-arrest care be integrated as the fifth link in the survival chain, after early warning, early cardiopulmonary resuscitation by witnesses, early defibrillation, and early advanced life support. The therapeutic management of patients that recover spontaneous circulation after cardiopulmonary resuscitation maneuvers based on life support measures and a series of improvised actions based on "clinical judgment" might not be the best way to treat patients with post-cardiac arrest syndrome. Recent studies indicate that using goal-guided protocols to manage these patients including therapeutic measures of proven efficacy, such as inducing mild therapeutic hypothermia and early revascularization, when indicated, can improve the prognosis considerably in these patients. Given that there is no current protocol based on universally accepted evidence, the Steering Committee of the National Cardiopulmonary Resuscitation Plan of the Spanish Society of Intensive Medicine and Cardiac Units has elaborated this document after a thorough review of the literature and an online discussion involving all the members of the committee and a consensus meeting with the aim of providing a platform for the development of local protocols in different ICSs in our country to fit their own means and characteristics.

Hyperglycemia in patients undergoing cerebral aneurysm surgery: its association with long-term gross neurologic and neuropsychological function

OBJECTIVE

To evaluate whether elevated intraoperative blood glucose concentrations are associated with an increased risk of long-term neurologic dysfunction in patients at risk for ischemic brain injury.

PATIENTS AND METHODS

Data from 1000 patients were retrieved from the Intraoperative Hypothermia for Aneurysm Surgery Trial database. All patients were recruited between February 2000 and April 2003, and underwent surgery for aneurysm clipping within 14 days of subarachnoid hemorrhage. Gross neurologic and neuropsychological function was evaluated at 3 months after surgery using certified observers and standardized assessment instruments. Intraoperative blood glucose concentrations, measured once when the aneurysm clip was placed, were correlated with neurologic outcome using both univariable and multivariable logistic regression analyses.

RESULTS

Blood glucose concentrations at the time of aneurysm clipping ranged from 59 to 331 mg/dL. At 3 months after surgery, those with blood glucose concentrations of 129 mg/dL or more (upper 2 quartiles) were more likely to have impaired cognition (P=.03). Those with glucose concentrations of 152 mg/dL or more (upper quartile) were more likely to experience deficits in gross neurologic function assessed by the National Institutes of Health Stroke Scale (P<.05), but not other scoring scales. Length of stay in intensive care units was longer in those with glucose concentrations of 129 mg/dL or more, but there was no difference among glucose groups in the duration of overall hospital stay or the fraction of patients discharged to home.

CONCLUSION

In patients at high risk for ischemic brain injury, intraoperative hyperglycemia, of a magnitude commonly encountered clinically, was associated with long-term changes in cognition and gross neurologic function.

Severe head injury: control of physiological variables, organ failure and complications in the intensive care unit

BACKGROUND

In patients with severe head injury, control of physiological variables is important to avoid intracranial hypertension and secondary injury to the brain. The aims of this retrospective study were to evaluate deviations of physiological variables and the incidence of extracranial complications in patients with severe head injury. We also studied if these deviations could be related to outcome.

PATIENTS AND METHODS

One hundred and thirty-three patients were included during a 5-year period (1998-2002). Deviations from treatment goals for the following physiological variables were studied: blood pressure, haemoglobin, blood sugar, serum sodium, serum albumin and temperature. Extra cerebral organ complications were also recorded as well as outcome at 6 months.

RESULTS

The median age was 32 years (range; 1-88 years). Median Glasgow Coma Scale (GCS) before intubation was 6 (range; 3-14). The frequencies of severe deviations from the desired values of the physiological variables for at least one treatment day were: hypotensive episodes (systolic BP < 90 mmHg) - 20%, anaemia (hgb < 8 g/dL) - 22%, blood glucose > 10 mmol/l - 26%, serum sodium concentration < 130 mmol/l - 10%, serum albumin < 25 g/l(-1)- 31% and hyperthermia > 39 degrees C - 24%. Pneumonia was diagnosed in 71% and Acute Lung Injury (ALI)/Adult Respiratory Distress Syndrome (ARDS) in 26% of the patients. Other complications such as severe sepsis (6%), renal failure (1.5%), a coagulation disorder (6%) and liver failure (one patient) were infrequent. Age, GCS, hypotension during the first day of treatment, elevated blood sugar and low albumin predicted an unfavourable outcome.

CONCLUSIONS

Deviations of key physiological variables and pulmonary complications were frequent in patients suffering from severe head injury. During intensive care treatment, hypotension, elevated blood sugar and hypoalbuminemia are possible independent predictors of an unfavourable outcome.

Anesthetic issues and perioperative blood pressure management in patients who have cerebrovascular diseases undergoing surgical procedures

Patients who have cerebrovascular disease and vascular insufficiency routinely have neurosurgical and nonneurosurgical procedures. Anesthetic priorities must provide a still bloodless operative field while maintaining cardiovascular stability and renal function. Patients who have symptoms or a history of cerebrovascular disease are at increased risk for stroke, cerebral hypoperfusion, and cerebral anoxia. Type of surgery and cardiovascular status are key concerns when considering neuroprotective strategies. Optimization of current condition is important for a good outcome; risks must be weighed against perceived benefits in protecting neurons. Anesthetic use and physiologic manipulations can reduce neurologic injury and assure safe and effective surgical care when cerebral hypoperfusion is a real and significant risk.

Post resuscitation care: what are the therapeutic alternatives and what do we know?

A large proportion of deaths in the Western World are caused by ischaemic heart disease. Among these patients a majority die outside hospital due to sudden cardiac death. The prognosis among these patients is in general, poor. However, a significant proportion are admitted to a hospital ward alive. The proportion of patients who survive the hospital phase of an out of hospital cardiac arrest varies considerably. Several treatment strategies are applicable during the post resuscitation care phase, but the level of evidence is weak for most of them. Four treatments are recommended for selected patients based on relatively good clinical evidence: therapeutic hypothermia, beta-blockers, coronary artery bypass grafting, and an implantable cardioverter defibrillator. The patient's cerebral function might influence implementation of the latter two alternatives. There is some evidence for revascularisation treatment in patients with suspected myocardial infarction. On pathophysiological grounds, an early coronary angiogram is a reasonable alternative. Further randomised clinical trials of other post resuscitation therapies are essential.

The effect of clonidine on cell survival, glutamate, and aspartate release in normo- and hyperglycemic rats after near complete forebrain ischemia

The present study was undertaken to investigate the effects of the alpha2 adrenergic agonist, clonidine, on the near complete cerebral ischemia (NCFI) evoked release of glutamate and aspartate from normo- and hyperglycemic rodent brain tissue using microdialysis tissue techniques. Hemodynamic variables, blood lactate, and glucose levels were monitored throughout the 40 min NCFI occlusion period. After 48 h, rats were killed and the extent of neuronal injury was determined in the cortex, striatum, and hippocampus. Hemodynamic variables recorded during ischemia improved with clonidine treatment in both normo- and hyperglycemic groups. Glutamate and aspartate levels were greatly increased over control values during normo- and hyperglycemic NCFI treatment. Clonidine pretreatment suppressed the release of both glutamate and aspartate during NCFI in normo- and hyperglycemic rodents when compared with NCFI-treated normo- and hyperglycemic rats without the drug. Significant neuroprotection of cells in the cortex, striatum, and hippocampus was also observed in drug-treated animals 48 h postischemia. The combined effects of diminished glutamate release after NCFI and reduced neuronal injury in both normo- and hyperglycemic states suggests that clonidine treatment during NCFI is neuroprotective. The neuroprotective effect of clonidine during ischemia may be ascribed to both a sensitization of central sympathetic activity and a reduced release of glutamate thereby reducing NMDA receptor activation and neuronal damage.

Hyperglycemia in patients administered dexamethasone for craniotomy

Hyperglycemia should be avoided during neurosurgery in order to decrease the risk of neurological injury. Dexamethasone has been associated with increased blood glucose during surgery. In this prospective, nonrandomized study, we documented the blood glucose concentration changes for 12 h in 34 nondiabetic patients undergoing craniotomy and compared patients who received intraoperative dexamethasone (10 mg IV on induction and 4 mg IV 6 h later), with or without preoperative dexamethasone, with patients who did not receive dexamethasone. Blood glucose concentrations increased from the preinduction value in all groups. Patients not taking dexamethasone before surgery, but who were given it intra- and postoperatively, had the largest peak blood glucose concentrations (11.0 +/- 2.0 mmol/L, mean +/- sd; P < 0.01) compared with patients who received no dexamethasone (7.8 +/- 2.1 mmol/L) or those who had been taking dexamethasone before surgery and continued it during surgery (8.5 +/- 1.2 mmol/L). The peak blood glucose concentrations in this group occurred 9 +/- 2 h after the induction of anesthesia. We recommend that the blood glucose concentration be monitored for at least 12 h in nondiabetic patients having neurosurgery who are newly administered dexamethasone.

Hyperglycemia in patients administered dexamethasone for craniotomy

Hyperglycemia should be avoided during neurosurgery in order to decrease the risk of neurological injury. Dexamethasone has been associated with increased blood glucose during surgery. In this prospective, nonrandomized study, we documented the blood glucose concentration changes for 12 h in 34 nondiabetic patients undergoing craniotomy and compared patients who received intraoperative dexamethasone (10 mg IV on induction and 4 mg IV 6 h later), with or without preoperative dexamethasone, with patients who did not receive dexamethasone. Blood glucose concentrations increased from the preinduction value in all groups. Patients not taking dexamethasone before surgery, but who were given it intra- and postoperatively, had the largest peak blood glucose concentrations (11.0 +/- 2.0 mmol/L, mean +/- sd; P < 0.01) compared with patients who received no dexamethasone (7.8 +/- 2.1 mmol/L) or those who had been taking dexamethasone before surgery and continued it during surgery (8.5 +/- 1.2 mmol/L). The peak blood glucose concentrations in this group occurred 9 +/- 2 h after the induction of anesthesia. We recommend that the blood glucose concentration be monitored for at least 12 h in nondiabetic patients having neurosurgery who are newly administered dexamethasone.

Effect of Single-Dose Dexamethasone on Blood Glucose Concentration in Patients Undergoing Craniotomy

Dexamethasone, a corticosteroid used to treat cerebral edema, is known to produce elevations in the blood glucose concentration, but the effect of a single intraoperative dose of dexamethasone on the blood glucose concentration is unknown. Glucose concentrations in response to either a 10-mg intravenous bolus of dexamethasone or a saline placebo were evaluated in nondiabetic patients undergoing elective craniotomy. Both arterial and venous blood glucose concentrations were obtained immediately before and after treatment and hourly for 4 hours intraoperatively. The arterial blood glucose concentration in those who received 10 mg dexamethasone (n = 10) increased from 97 +/-15 mg/dL (mean +/- SD) to 149 +/- 23 mg/dL over the course of the study, compared with a change from 88 +/- 11 mg/dL to 103+/-12 mg/dL in those who received placebo (n = 10) (P < 0.05 for 4-hour sample vs. baseline for both groups; P < 0.05 between groups at 4 hours). Further, venous blood glucose concentrations were highly predictive of arterial glucose values (R = 0.98; P < 0.001). Since elevations in the blood glucose concentration should be avoided in the setting of central nervous system ischemia, findings from this investigation suggest that contemplated corticosteroid use should be reviewed for appropriateness of treatment. If dexamethasone is used, even as a single dose during craniotomy, intraoperative blood glucose concentrations should be carefully monitored and hyperglycemia treated, particularly in patients at risk for glucose-mediated exacerbation of brain injury.

Prise en charge du patient neurochirurgical avec tumeur intracrânienne

1. Neurological state of patient.

PROCEDURES

(low risk of ICP problems or ischemia, little need for brain relaxation). - Volatile-based technique; "high-risk" procedures (anticipated ICP problems, significant risk of intraoperative cerebral ischemia, need for excellent brain relaxation): use total intravenous anaesthesia. EXTRACRANIAL MONITORING: For example, cardiovascular or renal, venous air embolism. Intracranial monitoring. - General environment vs. specific functions-metabolic (jugular venous bulb), neurophysiological (EEG/EP), functional (transcranial Doppler). 4. Induction of anaesthesia.

GOALS

Ventilatory control (early mild hyperventilation; avoid hypercapnia, hypoxemia); blood pressure control (avoid CNS arousal: adequate antinociception, anaesthesia); optimal position on ICP-volume curve. PATIENT POSITIONING: Pin holder application --> maximal nociceptive stimulus, block by deeper anaesthesia or analgesia and local anesthetic pin site infiltration. Alternative: antihypertensives. 5. Maintenance of anaesthesia.

GOALS

Controlling brain tension via control of CMR and CBF: preventing CNS arousal (depth of anaesthesia, antinociception); treating consequences of CNS arousal (sympatholysis, antihypertensives); the "chemical brain retractor concept". NEUROPROTECTION: Maintenance of an optimal intracranial environment (matching cerebral substrate demand and supply). 6. Emergence from anaesthesia.

GOALS

Maintain intra/extracranial homeostasis. Avoid factors --> intracranial bleeding and/or increasing CBF/ICP. The patient should be calm, co-operative and responsive to verbal commands soon after emergence. EARLY VS. LATE EMERGENCE: Ideal: rapid emergence to permit early assessment of surgical results and postoperative neurological follow-up, but there are still some categories of patients where early emergence is not appropriate.

Gas embolism: pathophysiology and treatment

Based on a literature search, an overview is presented of the pathophysiology of venous and arterial gas embolism in the experimental and clinical environment, as well as the relevance and aims of diagnostics and treatment of gas embolism. The review starts with a few historical observations and then addresses venous air embolism by discussing pulmonary vascular filtration, entrapment, and the clinical occurrence of venous air emboli. The section on arterial gas embolism deals with the main mechanisms involved, coronary and cerebral air embolism (CAE), and the effects of bubbles on the blood-brain barrier. The diagnosis of CAE uses various techniques including ultrasound, perioperative monitoring, computed tomography, brain magnetic resonance imaging and other modalities. The section on therapy starts by addressing the primary treatment goals and the roles of adequate oxygenation and ventilation. Then the rationale for hyperbaric oxygen as a therapy for CAE based on its physiological mode of action is discussed, as well as some aspects of adjuvant drug therapy. A few animal studies are presented, which emphasize the importance of the timing of therapy, and the outcome of patients with air embolism (including clinical patients, divers and submariners) is described.

[Treatment of cerebral oedema]

Progress in brain imaging, monitoring and physiopathology allows the identification of brain oedema from brain swelling, determination of its interstitial or intracellular nature, as well as blood-brain barrier permeability and the evaluation of the impact on cerebral haemodynamic. Common treatment of all types of cerebral oedema is based on prevention of self-sustained disorders due to increased intracranial pressure resulting in ischemic cerebral oedema. The specific treatment of each type of cerebral oedema is reviewed. Optimization of conventional anti-oedematous strategies is based on the precise determination of the nature of the cerebral oedema and of the blood-brain barrier status.

The relationship between blood glucose, mean arterial pressure and outcome after severe head injury: an observational study

BACKGROUND AND METHOD

Hypotension and hyperglycaemia occurring in the first 24h after severe head injury are individually associated with poor outcome but a causal effect has not been proven for either. Their combined effect is unknown and is investigated in this observational study of 338 patients with head injury, a Glasgow coma score (GCS) of 8 or less and requiring mechanical ventilation.

RESULTS

Mean arterial pressure (MAP) and blood glucose are linearly related to mortality (P<0.0001). Regression analysis shows that each has an independent effect. Moreover, the relationship between blood glucose and mortality is stronger than the relationship between MAP and mortality. When patients are grouped according to lowest MAP, hyperglycaemia is associated with increasing mortality within each group (P<0.0001).

CONCLUSION

Further studies on the combined effect of hyperglycaemia and hypotension on mortality after head injury are needed because this study suggests, but does not prove, an additive, causal association.

Anesthesia-related cardiac arrest in children. An update

The improvement in mortality rates for anesthetized children over the past 50 years reflects the many improvements that have been made in pediatric perioperative care. The modern pediatric anesthesiologist is better trained than the predecessors of half a century ago, and has a vastly improved arsenal of monitoring devices and anesthetic agents from which to choose. The modern pediatric perioperative environment is better equipped to meet the unique needs of children. Techniques practiced by surgeons, nurses, radiologists, and pharmacologists help create a far more sophisticated infrastructure than existed 50 years ago. Given these changes, it is not surprising that outcomes for patients have improved.

General anaesthesia for supratentorial neurosurgery

Anaesthesia for the surgical treatment of supratentorial tumours requires an understanding of: the pathophysiology of a localised or generalised increase in intracranial pressure (ICP), the regulation and maintenance of intracerebral perfusion, avoidance of secondary systemic insults to the brain, and the effects of anaesthetic drugs on ICP, cerebral perfusion and cerebral metabolism. Knowledge of the therapeutic options available for decreasing ICP, brain bulk and brain tension perioperatively is also essential. Potential complications which may present during supratentorial neurosurgery include massive intraoperative haemorrhage and seizures. The fact that the surgeon is operating on a tensed brain is also a potential source of difficulty. The need to monitor brain function and environment during surgery poses a challenge to the anaesthesiologist, as does the achievement of rapid emergence from anaesthesia with the adequate use of anaesthetic drugs.

Glucose and the ischemic brain: a sour grape or a sweet treat?

The lactic acidosis hypothesis of cerebral ischemia has relied on a single finding to support its main postulate: pre-ischemic hyperglycemia-aggravated ischemic brain damage. Although this finding is by no means the proof that the lactic acidosis hypothesis desperately needs, the premise of the hypothesis has been employed in hospitals around the world. A better understanding of some of the processes involved in elevating blood glucose levels pre-ischemia and their influence on the ischemic brain is now available. This understanding offers a unique opportunity to re-examine old dogmas and propose new ideas, in the form of an alternative hypothesis to explain 'the glucose paradox of cerebral ischemia'.

Pediatric resuscitation in the operating room

The resuscitation of pediatric patients undergoing anesthesia involves appropriate administration of fluid and blood products and stabilization of vital signs. Crystalloid is first-line therapy for fluid resuscitation, and should be given with awareness of its potential dilution of the child's hematocrit. Many alternatives to homologous blood transfusions now exist, however, when necessary for increasing oxygen-carrying capacity or treating coagulopathy benefits likely outweight the risks. The risks for such transfusion include infectious, hemolytic, metabolic, and immunologic effects. When fluid and blood administration does not stabilize the patient, the differential diagnosis of hypotension, arrest, or arrhythmias must include medication errors, anesthetic overdose, electrolyte disturbances, hypoxemia, ventilatory problems, and surgical insults, including medications given in the operative field. Resuscitation should include treatment of hypocalcemia and hyperkalemia, chest compressions, and the administration of epinephrine when necessary.

The effects of intraoperative glucose infusion on portal blood insulin concentration and hepatic mitochondrial redox state during surgery: comparison of short-term and continuous infusions

The relationships between the blood glucose level, portal blood immunoreactive insulin (IRI) concentration, ketogenesis, and hepatic mitochondrial redox state associated with intraoperative glucose administration were evaluated in patients undergoing total gastrectomy. A total of 26 patients were randomly allocated to two groups according to the type of infusion given; group 1 was given a short-term glucose infusion of 25 g in 30 min and group 2 was given a continuous glucose infusion of 10 g/h. The blood glucose concentration peaked 30 min after the glucose infusion was commenced, then decreased in group 1, despite a continuous rise in group 2. A temporary but significantly higher blood glucose level was observed in group 1 than in group 2, 30 and 60 min after the infusion was commenced. The portal blood IRI concentrations and arterial ketone body ratio (AKBR) continued to increase and the blood ketone body concentrations continued to decline after the start of the glucose infusion in both groups; however, after 60 and 120 min, the portal blood IRI and AKBR levels were significantly higher, and the blood ketone body levels significantly lower in group 1 than in group 2. These findings suggest that intraoperative glucose administration is beneficial for insulin secretion, ketogenesis, and the hepatic mitochondrial redox state, and that short-term infusion is superior to continuous infusion.

Long-term mild hypothermia with extracorporeal lung and heart assist improves survival from prolonged cardiac arrest in dogs

BACKGROUND AND PURPOSE

although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hypothermia-mediated brain protection. The present study evaluated the effects of long-term ECLHA with mild to moderate hypothermia (33 degrees C) in a canine model of prolonged cardiac arrest.

METHODS

15 dogs were assigned to either the hypothermic (seven dogs, 33 degrees C) or normothermic group (eight dogs, 37.5 degrees C). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensive care. The hypothermia group maintained core (pulmonary artery) temperature at 33 degrees C for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dose; (3) time to extubation; (4) necrotic myocardial mass (g); and (5) neurological deficits score (NDS).

RESULTS

in the normothermic group five dogs died of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5 +/- 4.9%) with necrotic myocardial mass of 14.5 +/- 3.5 g. In the hypothermic group, one dog died from pulmonary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8 +/- 2.5%), but there was evidence of some brain-protective effect. The mass of necrotic myocardium was 4.2 +/- 1.3 g in the hypothermic group or 3.4 times smaller than in the normothermic group. The survival rate was significantly higher in the hypothermic than in the normothermic group (P < 0.05). The catecholamine requirement was also lower in the hypothermic than in the normothermic dogs (P < 0.05).

CONCLUSIONS

Long-term mild to moderate hypothermia with ECLHA induced immediately after cardiac arrest improved survival as well as cerebral and cardiac outcomes.

[Vascular loading in the first 24 hours following severe head injuries]

The main goal at the acute phase of head injury is to prevent a decrease in blood pressure, which promotes cerebral ischemia. Volume loading is therefore frequently indicated. A normal or increased plasma osmolarity should be maintained. Thus hypotonic fluids should be avoided. Hyperglycaemia is also a risk factor for brain injury and glucose use has to be restricted in the first hours after trauma. Isotonic saline 0.9% is the first solution to be infused. Lactated Ringer solutions are mildly hypotonic as approximately 114 mL of free water is contained in each litre of the solution. Isotonic colloids are indicated to replace blood losses, but have no advantage over cristalloids, concerning the development of cerebral oedema. Fluid restriction minimally affects cerebral edema. Because of the severe consequences of hypovolaemia and hypotension, fluids should not be restricted until haemodynamic stability is achieved. Hypertonic fluids rapidly restore intravascular volume and decrease intracranial pressure. Although they probably have a place in prehospital intensive therapy, the demonstration of their benefit is still lacking. Monitoring of intravascular volume is essential. Continuous arterial pressure and central venous pressure monitoring are mandatory. New monitoring techniques as the measurement of systolic pressure variations or transoesophageal Doppler echocardiography will probably find a place in the management of trauma patients in the near future.

The influence of hyperglycemia on neurological outcome in patients with severe head injury

OBJECTIVE

Traumatic brain injury is associated with a stress response that includes hyperglycemia, which has been shown to worsen neurological outcome during cerebral ischemia and hypoxia. To better examine the relationship between hyperglycemia and outcome after head injury, we studied the clinical course of 267 head-injured patients who were admitted for treatment in the neurosurgical department of Asclepeion Hospital of Athens between January 1993 and November 1997.

METHODS

We prospectively studied 267 patients with moderate or severe craniocerebral injury (Glasgow Coma Scale scores, 3-12) who were treated surgically for evacuation of an intracranial hematoma and/or placement of a device for intracranial pressure monitoring under general anesthesia to determine the relationship between serum glucose levels, severity of injury, and neurological outcome.

RESULTS

Patients with severe head injury had significantly higher serum glucose levels than did those with moderate injury. Patients who subsequently had an unfavorable outcome had significantly higher glucose levels than did those with a better prognosis. Among the patients with more severe head injury, a glucose level greater than 200 mg/dl was associated with a worse outcome. In the same group of patients, a significant relationship was found between postoperative glucose levels, pupillary reaction, and maximum intracranial pressure during the first 24 hours. Multivariate analysis showed that postoperative glucose levels were an independent predictor of outcome.

CONCLUSION

Early hyperglycemia is a frequent component of the stress response to head injury, a significant indicator of its severity, and a reliable predictor of outcome.

The prevention and treatment of cerebral ischemia

Although the major focus of recent cerebral protection research has been aimed at developing receptor-specific drugs, this effort has currently resulted in few improvements in patient outcome. Until advances in pharmacology translate to improvements in humans, the clinician and his patients will be well served by using more traditional techniques to prevent and treat cerebral ischemic events. This approach will involve interventions to a) identify patients who are experiencing or are at risk for developing cerebral ischemia, and b) alter systemic physiology in an attempt to lessen the duration and severity of any ischemic insults. Initial therapy should include interventions to improve cerebral perfusion and the oxygen carrying capacity of the blood. Once this is accomplished, measures should be taken to control blood glucose concentrations and treat fever. In otherwise stable surgical patients, mild reductions in patient temperature also may be of benefit, provided the temperature reductions do not introduce problems in systemic physiology and the patient is rewarmed prior to awakening from general anesthesia. General anesthetic choice may be of importance in controlling intracranial pressure and seizure activity; however, if direct cerebral protection is desired, the anesthetic of choice should be a barbiturate. Finally, in the patient at risk for cerebral vasospasm, nimodipine treatment should be considered. Collectively, these interventions should increase the patient's chance for optimal neurologic recovery following ischemia.

Basic surgical techniques in the resection of malignant gliomas

Although progress is being made in the imaging and medical therapy of malignant gliomas, surgery continues to play a central role in the management of these tumors. Surgery remains necessary for histological diagnosis and relief of mass effect upon adjacent neurological structures. Surgery also achieves cytoreduction of tumor mass, allowing more effective treatment of residual tumor volume. Recent technical advances have made the goal of gross total tumor resection safer and more readily achieved. Surgical techniques and adjuncts that aid the aggressive surgical resection of malignant gliomas will be reviewed.

The selection and administration of perioperative intravenous fluids for the pediatric patient

The perioperative administration of intravenous fluids and the maintenance of fluid homeostasis is essential in the comprehensive care of the pediatric patient. Intravascular fluid balance is influenced by a number of preoperative, intraoperative, and postoperative circumstances. The pediatric patient is not simply a small adult, and therefore cannot be treated as such with respect to intravenous fluid administration. The restoration and maintenance of the smaller pediatric intravascular volume is crucial to optimize cardiac output and ensure tissue oxygen delivery.

Poisoning and drug overdose

Poisoning is a common cause for intensive care unit admission for both children and adults, and most poisoning victims are effectively treated using standard decontamination measures and supportive care. For a small number of poisons, acceleration of toxin removal with hemodialysis or hemofiltration is indicated. Similarly, specific antidotes are indicated in a few selected circumstances. Rarely, patients may benefit from more aggressive supportive techniques such as cardiopulmonary bypass.

Current concepts in cardiopulmonary resuscitation

The "chain of survival" is important in the resuscitation of a patient who has had a cardiac arrest. The provision of Basic Life Support (BLS) and Advanced Cardiac Life Support (ACLS) is essential in this "chain of survival." Both BLS and ACLS have undergone several revisions since their initial inception. This article reviews (1) the current established and investigational issues of cardiopulmonary resuscitation, (2) the incidence and outcomes of anesthesia-related cardiac arrest, (3) the use of cardiopulmonary bypass in resuscitation, and (4) cerebral protection during and after resuscitation.

Therapy of patients with head injuries: key parameters for management

BACKGROUND

Secondary brain injury, presumed secondary to ischemia, increases the mortality and morbidity of traumatic brain injury. Although many mechanisms appear to be involved, many potential ischemic insults results from changes in readily observable physiologic variables.

METHODS

A focused search of scientific articles published in English to determine what data are available to suggest parameters within which key physiologic variables should be maintained.

RESULTS

Few data demonstrate that maintenance of variables within specific ranges alters outcome; however, considerable evidence establishes association with poor outcome and hypotension, intracranial hypertension, and cerebral venous saturation. Key parameters vary somewhat based upon the phase of treatment after injury. Other variables, such as systemic oxygen delivery and brain saturation measured by near-infrared spectroscopy, are less well linked to outcome.

CONCLUSIONS

Further research is necessary to establish that manipulation of physiologic variables to maintain them within preset ranges improves outcome.

Brain edema, hemorrhagic necrosis volume, and neurological status with rapid infusion of 0.45% saline or 5% dextrose in 0.9% saline after closed head trauma in rats

We previously reported that in rats with closed head trauma (CHT), intravenous (IV) administration of 0.25 mL/g of 5% dextrose solution (D5W) increased blood glucose (G), decreased blood sodium (Na), caused no change in blood osmolality (Osm), increased brain edema (BE), and worsened neurological severity score (NSS) and mortality rate (MR). D5W in 0.9% saline (D5NS) is isonatremic and hyperosmolar with respect to blood and may avoid the problems reported with D5W. The present study compared the effects of 0.25 mL/g of D5NS or 0.45% saline (0.45 S) after CHT in rats. In 11 groups of rats, the three experimental variables were CHT (yes or no), IV fluid (none, D5NS, or 0.45 S), and time of death (4 or 24 h). D5NS or 0.45 S was given IV at 1 h after surgical preparation with or without CHT, and experimental values were determined at 1, 2, 4, and 24 h. D5NS decreased BE at 4 h compared with the untreated group, increased Osm (380 +/- 2 mOsm/kg) and G (1278 +/- 199 mg/dL), decreased Na (131 +/- 2 mEq/L) in blood, and caused no significant change in hemorrhagic necrosis volume (HNV), NSS, or MR. 0.45 S increased MR (50%) at 24 h, decreased Osm (270 +/- 5 mOsm/kg) and Na (123 +/- 1 mEq/L) in blood, and caused no significant change in G, BE, HNV, or NSS. We conclude that after CHT in rats, D5NS decreased BE without changing NSS or MR. 0.45 S increased MR and significantly altered blood chemistries.