Hemodynamic effects of high dose pentobarbital: studies in elective neurosurgical patients

Comparing the Bispectral Index and Suppression Ratio with Burst Suppression of the Electroencephalogram During Pentobarbital Infusions in Adult Intensive Care Patients

OBJECTIVE

The bispectral index (BIS), a processed variable derived from the raw electroencephalogram (EEG) used to guide sedation in the intensive care unit (ICU), has not been tested during barbiturate therapy for elevated intracranial pressure. We determined the BIS and suppression ratio (SR) values during traditional burst monitoring of the raw EEG during pentobarbital infusions.

DESIGN

Prospective, observational cohort study.

SETTING

A 42-bed multidisciplinary ICU in a tertiary care medical center.

PATIENTS

Twelve consecutive patients with elevated intracranial pressure treated with pentobarbital infusions.

INTERVENTION

All patients were monitored continuously with the Aspect Medical Systems A-1050 bedside EEG monitor using a bilateral referential montage. Pentobarbital doses were titrated based on the raw EEG to attain a burst-suppression pattern with a goal of 3-5 bursts/minute. Drug dosage, intracranial pressure, cerebral perfusion pressure values, EEG bursts/minute, BIS version 3.2, and SR were recorded daily.

MEASUREMENTS AND MAIN RESULTS

The 12 patients were monitored for 62 patient-days. Mean +/- SD age was 32 +/- 15 years, seven (58%) patients were male, mean Acute Physiology and Chronic Heath Evaluation II score was 17.0 +/- 5.0, and hospital mortality was 42%. The mean pentobarbital infusion rate was 124 +/- 49 mg/hour or 2.3 +/- 1.3 mg/kg/hour, and mean pentobarbital serum concentration was 29.7 +/- 13 microg/ml. The mean BIS value was 18 +/- 14, mean SR 56% +/- 36%; BIS correlated well with SR (r=-0.99, p<0.001). For patient-days with a burst-suppression pattern, BIS 3.2 (r=0.90, p<0.001) and SR (r=-0.89, p<0.001) strongly correlated with the number of bursts/minute. The mean BIS value corresponding to 3-5 bursts/minute was 15 (95% confidence interval [CI] 10-20); SR value was 71 (95% CI 61-80).

CONCLUSION

The Aspect A-1050 applied to patients and monitored by nurses and physicians works well as a bedside EEG monitor, providing a raw EEG signal to titrate barbiturate therapy. The continuous data trend and real-time digital output for the BIS and SR quantify the degree of EEG suppression well and may prove helpful in facilitating titration of barbiturate infusions.

Barbiturate coma for intracranial hypertension: clinical observations

PURPOSE

To determine the neurologic outcome of patients with intracranial hypertension treated with barbiturate-induced coma.

MATERIALS AND METHODS

The records of 49 patients who were admitted to a 31-bed medicosurgical intensive care unit over a 5-year period in whom a barbiturate coma was induced to control intracranial hypertension were analyzed retrospectively. Analysis included assessment of the response to barbiturate coma and evaluation of the long-term neurologic outcome according to the Glasgow Outcome Scale (GOS).

RESULTS

Intracranial hypertension was caused by head trauma in 28 patients and subarachnoid hemorrhage in 21 patients. Eight of the head trauma patients and 5 of the patients with subarachnoid hemorrhage survived their hospital stay. The survivors were younger than the nonsurvivors, and had a good neurologic status after 1 year (except for 2 patients who died 1 and 3 months after discharge, respectively). There was no significant difference in the Glasgow Coma Score (GCS) on admission between the survivors and the nonsurvivors. The long-term outcome at 1 year was markedly better in the patients who had experienced a subarachnoid hemorrhage than in the trauma patients.

Recent advances in neuroanaesthesia

In order to provide optimum intracranial operating conditions for neurosurgery, anaesthetists must have a thorough understanding of brain physiology and how this is affected by pathology and anaesthetic drugs and techniques. This article discusses the current understanding of cerebral vascular physiology and how novel neuroanaesthetic drugs and techniques affect it.

Use of hypertonic saline in the treatment of severe refractory posttraumatic intracranial hypertension in pediatric traumatic brain injury

OBJECTIVES

To evaluate the effect of prolonged infusion of 3% hypertonic saline (514 mEq/L) and sustained hypernatremia on refractory intracranial hypertension in pediatric traumatic brain injury patients.

DESIGN

A prospective study.

SETTING

A 24-bed Pediatric Intensive Care Unit (Level III) at Children's Hospital.

PATIENTS

We present ten children with increased intracranial pressure (ICP) resistant to conventional therapy (head elevation at 30 degrees, normothermia, sedation, paralysis and analgesia, osmolar therapy with mannitol, loop diuretic, external ventricular drainage in five patients), controlled hyperventilation (Pco2, 28-35 mm Hg), and barbiturate coma. We continuously monitored ICP, cerebral perfusion pressure (CPP), mean arterial pressure, central venous pressure, serum sodium concentrations, serum osmolarity, and serum creatinine.

INTERVENTIONS

A continuous infusion of 3% saline on a sliding scale was used to achieve a target serum sodium level that would maintain ICP <20 mm Hg once the conventional therapy and barbiturate coma as outlined above failed to control intracranial hypertension.

MEASUREMENTS AND MAIN RESULTS

The mean duration of treatment with 3% saline was 7.6 days (range, 4-18 days). The mean highest serum sodium was 170.7 mEq/L (range, 157-187 mEq/L). The mean highest serum osmolarity was 364.8 mosm/L (range, 330-431 mosm/L). The mean highest serum creatinine was 1.31 mg/dL (range, 0.4-5.0 mg/dL). There was a steady increase in serum sodium versus time zero that reached statistical significance at 24, 48, and 72 hrs (p < .01). There was a statistically significant decrease in ICP spike frequency at 6, 12, 24, 48, and 72 hrs (p < .01). There was a statistically significant increase in CPP versus time zero at 6, 12, 24, 48, and 72 hrs (p < .01). There was a statistically significant increase in serum osmolarity versus time zero at 12 hrs (p < .05) and at 24, 48, and 72 hrs (p < .01). Two patients developed acute renal failure and required continuous veno-venous hemodialysis; these were concurrent with an episode of sepsis and multisystem organ dysfunction. Both recovered full renal function with no electrolyte abnormalities at the time of discharge.

CONCLUSION

An increase in serum sodium concentration significantly decreases ICP and increases CPP. Hypertonic saline is an effective agent to increase serum sodium concentrations. Sustained hypernatremia and hyperosmolarity are safely tolerated in pediatric patients with traumatic brain injury. Controlled trials are needed before recommendation of widespread use.

Intracranial pressure: current status in monitoring and management

One of the most frequently occurring questions in the neurological critical care of children involves the indications for measurement of intracranial pressure (ICP) and the appropriate therapies for abnormally elevated ICP. Advances in monitoring technology have improved the safety and accuracy of ICP measurement. Clinical and basic research into the mechanisms of brain swelling and the efficacy of various therapies, especially in the realm of traumatic brain injury, has allowed the development of rational and specific treatment strategies for elevated ICP. For several diseases, the ability to measure and manage ICP has resulted in marked improvements in outcomes. This article reviews the indications for, and recommended methods of, measuring ICP in children and discusses the status of therapies commonly used to control elevated ICP.

Multimodality treatment of deep periventricular cerebral arteriovenous malformations

The surgical treatment of arteriovenous malformations (AVMs) located in deep periventricular regions such as the basal ganglia is associated with marked morbidity and mortality. Approaches through critical brain regions afford limited exposure of the lesions, while surgical dissection is sometimes complicated by acute severe brain swelling and/or hemorrhage in the surrounding tissues. In our approach to deep AVMs, our regimen has evolved from direct staged microsurgical excision under routine fentanyl-N2O-relaxant anesthesia (first four patients) to the use of elective high-dose barbiturate anesthesia (subsequent 12 patients). In the first group of four patients, 11 operations were performed. Two patients improved, one of whom returned to normal neurologically. There were three episodes of acute brain swelling and/or hemorrhage. One patient died as a result, and another deteriorated. In the second group of 12 patients, all but two lesions were completely excised. Among the 10 patients in whom the AVM was completely excised, seven improved, six of whom achieved a good to excellent outcome, with two regaining full neurologic function. Three patients worsened (one as the result of acute brain swelling and/or hemorrhage). There was no death in this group. Only one incidence of acute brain swelling and/or hemorrhage occurred in 26 operations. Even though the number of patients is too small in the first group for meaningful statistical comparison, our intraoperative observations and postoperative results suggest that our evolved multimodality regimen, such as staged excision and the use of elective high-dose barbiturates, was likely to have contributed to the improved treatment results of these formidable lesions.

Intensive management of severe head injury

Intensive management of patients with severe head injury offers the best hope of minimizing death and functional disability in a young, working population. Secondary neurologic insult can be decreased by cardiorespiratory support and ICP control from the outset. Rapid neurologic assessment, airway management, and support of circulation are the basis of emergency management for head injury. Patients with severe head injury require intensive care management for two major reasons: management of ICP and management of organ system dysfunction. Care should not be withheld because of initially grim (and inaccurate) prognostic assessment. Newer techniques for assessing the adequacy of cerebral circulation may allow refinement of management strategies in the future.

Regional cerebral blood flow in the pig after a localized cerebral contusion treated with barbiturates

Regional cerebral blood flow determined with microsphere technique in anaesthetized pigs was measured before and after a localized cerebral contusion as well as after treatment with pentobarbital. No overall reduction in intracranial pressure or perfusion pressure was observed. Flow reduction due to pentobarbital was different in different regions with a high percentage change in the highly perfused basal structures and cortical grey matter except in the centre of the contusion where the reduction was half compared to the rest of cortical grey matter. Changes in white matter were less than in cortical grey matter but more pronounced than in the very high flow areas (choroid plexus and pineal gland). The accumulated change was greatest in the damaged region. Contralateral to the contusion, where a significant increase in flow was noticed after the contusion, there was a very low accumulated change in flow. In white subcortical matter underlying the contusion a similar low flow change was observed but this was not accompanied by as large an accumulated change as in grey cortical matter. At each fraction of injected pentobarbital a short-lasting increase in intracranial pressure and a reduction in mean arterial blood pressure was observed. The amplitude and the height of the intracranial pressure change was reduced during the pentobarbital injections.