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

An Audit and Comparison of pH, Measured Concentration, and Particulate Matter in Mannitol and Hypertonic Saline Solutions

Background: The preferred hyperosmolar therapy remains controversial. Differences in physical properties such as pH and osmolality may be important considerations in hyperosmolar agent selection. We aimed to characterize important physical properties of commercially available hyperosmolar solutions.

Methods: We measured pH and concentration in 37 commonly-used hyperosmolar solutions, including 20 and 25% mannitol and 3, 5, 14.6, and 23.4% hypertonic saline. pH was determined digitally and with litmus paper. Concentration was determined by freezing point and vapor pressure osmometry. Salinity/specific gravity was measured with portable refractometry. Particulate matter was analyzed with filtration and light microscopy and with dynamic light scattering nephelometry.

Results: pH of all solutions was below physiological range (measured range 4.13–6.80); there was no correlation between pH and solution concentration (R² = 0.005, p = 0.60). Mannitol (mean 5.65, sd 0.94) was less acidic than hypertonic saline (5.16, 0.60). 14/59 (24%) pH measurements and 85/111 concentration measurements were outside manufacturer standards. All 36/36 mannitol concentration measurements were outside standards vs. 48/72 (67%) hypertonic saline (p < 0.0001). All solutions examined on light microscopy contained crystalline and/or non-crystalline particulate matter up to several hundred microns in diameter. From nephelometry, particulate matter was detected in 20/22 (91%) solutions.

Conclusion: We present a novel characterization of mannitol and hypertonic saline. Further research should be undertaken, including research examining development of acidosis following hyperosmolar therapy, the relevance of our findings for dose-response, and the clinical relevance of particulate matter in solution.

Hypernatremia in the neurologic intensive care unit: how high is too high?

Hypernatremia is associated with increased mortality in hospitalized patients and in medical/surgical intensive care units. This relationship has not been studied in neurologic/neurosurgical intensive care units (NNICUs), where hypernatremia is often a component of treatment of cerebral edema. We performed a retrospective analysis of prospectively collected data in patients admitted to the NNICU over a 6.5-year period. Hypernatremia (serum sodium >150 mEq/L) was seen in 339 patients (7.9%) and was more common (24.3%) in patients who were treated with mannitol. Hypernatremic patients had a lower median admission Glasgow Coma Scale score (8 vs 14, P < .001), higher initial Acute Physiology and Chronic Health Evaluation II probability of death (34.9% vs 19.1%, P < .001), higher incidence of mechanical ventilation (80.5% vs 41.1.5%, P < .001), higher mortality (30.1% vs 10.2%, P < .001), and higher incidence of renal failure (10.3% vs 0.9%, P < .001). Mortality increased with increasing hypernatremia; however, only severe hypernatremia (serum sodium >160 mEq/L) was independently associated with increased mortality. Other factors independently associated with mortality were age, mechanical ventilation, initial Acute Physiology and Chronic Health Evaluation II probability of death or low admission Glasgow Coma Scale score, and a diagnosis of cerebrovascular disease. In conclusion, hypernatremia is common in the NNICU, more so in patients treated with mannitol. In this population, severe (but not mild or moderate) hypernatremia is independently associated with increased mortality.

[The preclinical care of polytraumatized patients]

In industrially developed countries, trauma is the major mortality factor for people younger than 40 years. The preclinical management of polytraumatized patients influences the prognosis of mortality and morbidity. In this period, a number of decisions have to be made under unfavourable conditions and with limited time. This situation represents a great challenge for the whole rescue team. Diagnostic overview, protection of the vital functions under the special situation of shock, immobilization of the spine and the treatment of the isolated injuries are part of the preclinical management efforts. Rescue of the polytraumatized patient, organization and announcement of transfer and the protection of the rescue team have to be taken into account.

Calculated Serum Osmolality Can Lead to a Systematic Bias Compared to Direct Measurement

The reference method to measure serum osmolality (Mosm) is the delta cryoscopic method. However, the technology may not be available. Clinicians therefore must calculate osmolality (Cosm) as the sum of concentrations of selected principal solutes such as sodium, potassium, urea, and glucose. To evaluate the validity of Cosm in patients in hyperosmolar state we compared Cosm to Mosm. Twenty-two ICU patients treated by infusion of hypertonic solutes for intracranial hypertension following head injury were prospectively studied. A control group of 10 patients with hypernatremia due to medical causes was also evaluated. Na+, blood urea nitrogen (BUN), and glucose were measured to calculate serum osmolality: Cosm = (2 x Na+) + BUN + glucose (in mOsm/kg). Measurement of serum osmolality was performed using the delta-cryoscopic method. The results of the two methods were compared by correlating the difference (Mosm-Cosm) between each pair of results with the mean of the pairs of results. Cosm underestimated Mosm (3.4 mOsm/kg, P < 0.02) in the control group whereas Cosm overestimated Mosm in patients who received hypertonic fluids (2.3 mOsm/kg, P < 0.03). Calculation of osmolality introduced a systematic bias, overestimating osmolality in the lower ranges and underestimating it in the higher ranges. In the range of hyperosmolality commonly used to manage intracranial hypertension following head trauma, serum osmolality, as determined by sum of principal serum solutes, compares poorly with direct measurement using standard osmometry.

Increases in spinal fluid osmolarity induced by mannitol

OBJECTIVE

Mannitol is widely used in hospitals worldwide to treat patients with high intracranial pressure and/or cerebral edema. One of the mechanisms by which mannitol is thought to affect intracranial pressure is by increasing the patient's serum osmolarity, but not the osmolarity in the brain or cerebrospinal fluid. In this way, mannitol is thought to increase the osmolarity gap between the brain and the blood, which in turn leads to removal of excess water from the brain. However, relatively little is known regarding long-term effects of mannitol on osmolarity of cerebrospinal fluid. We therefore sought to determine the effects of mannitol administration on the osmolarity of cerebrospinal fluid.

DESIGN

Controlled trial.

SETTING

University teaching hospital.

PATIENTS

Patients with severe head injury and patients with subarachnoid bleeding who required insertion of an intracranial probe.

MEASUREMENTS AND MAIN RESULTS

Serum and cerebrospinal fluid osmolarity were measured before and during mannitol administration in ten patients treated with mannitol for >or=72 hrs (group 1), ten patients treated for 24 to 48 hrs (group 2), and ten controls (group 3). Serum osmolarity increased quickly in all patients receiving mannitol (groups 1 and 2), whereas remaining constant in controls. Average cerebrospinal fluid osmolarity slowly increased in all patients receiving mannitol; cerebrospinal fluid osmolarity increased from (mean +/- sd) 291.5 +/- 4.0 to 315.5 +/- 4.5 mOsm/kg after 96 hrs in group 1 (p <.01), and from 288.9 +/- 3.5 to 296.9 +/- 6.2 mOsm/kg after 48 hrs in group 2 (p <.01). Cerebrospinal fluid osmolarity remained constant in controls (p <.01 for group 1 vs. group 3 and for group 2 vs. group 3, respectively). In group 1, the gap between serum and cerebrospinal fluid osmolarity initially increased (which was the desired effect), but later decreased first to baseline values and then to below-normal levels.

CONCLUSIONS

Long-term administration of mannitol can induce significant increases in cerebrospinal fluid osmolarity in patients with subarachnoid hemorrhage or severe head injury. This may be an undesirable and potentially dangerous effect. Therefore, cerebrospinal fluid osmolarity should be measured regularly in all patients receiving mannitol for longer than 24 hrs. If cerebrospinal fluid osmolarity increases, discontinuation or tapering of mannitol therapy should be considered.

[Effects of equiosmolar load of 20% mannitol, 7.5% saline and 0.9% saline on plasma osmolarity, haemodynamics and plasma concentrations of electrolytes]

OBJECTIVES

Mannitol 20% (M) and NaCl 7.5% (H) are hypertonic solutions used in-patient in hypovolaemic shock and in case of increased ICP. To our knowledge no study in humans compared them in an equiosmolar load. The objectives of this study were to compare the pharmacokinetics of both solutions in an equiosmolar load with an isotonic solution (NaCl 0.9% (C)) in terms of osmolarity, electrolytes and haemodynamic parameters over time.

STUDY DESIGN

Prospective, randomized, controlled study.

PATIENTS

Thirty ASA I and II patients undergoing non haemorrhagic surgery under general anesthesia.

METHODS

Three groups were studied (groups M, H and C), each receiving an equiosmolar load (4.95 mOsm kg(-1)) of solutions of mannitol 20%, saline 7.5% and saline 0.9% over ten minutes. Vital parameters (non invasive blood pressure, heart rate, oesophageal temperature) were monitored and blood samples (hemoglobin, hematocrit, K(+), Na(+), Cl(-), urea, creatinine, glucose, mannitolemia, osmolarity) were assessed preoperatively and intraoperatively at times 0, 3, 5, 10, 15, 30, 45, 60, 90, 120, 150 min of perfusion.

RESULTS

In both hypertonic groups, osmolarity was maximal at the end of infusion (group M: 329 +/- 7 mOsm l(-1); group H: 321 +/- 11 mOsm l(-1)); at the same time, Na(+) value was lowest in group M: 129 +/- 3 mmol l(-1) and highest in group H: 151 +/- 5 mmol l(-1), P < 0.001) with normalisation at 60 min. These results were also statistically significant when compared to the isotonic group (group C: osmolarity: 296 +/- 3 mOsm l(-1), P < 0.001; Na(+): 140 +/- 2 mmol l(-1), P < 0.001). Plasma volume expansion was statistically significantly larger in-group C between 10 and 15 min compared to both hypertonic groups (haematocrit: group C: 35 +/- 4%, group M: 39 +/- 5%; group H: 41 +/- 3%, P < 0.004). Haemodynamic parameters were similar in the 3 groups with however a trend towards lowers HR in the mannitol group, particularly at T10. Temperature was lower in the control group because of the volume infused. Cl(-) was higher in the H group.

CONCLUSION

A single infusion of 4.95 mOsm kg(-1) of mannitol 20% or NaCl 7.5% induces a similar osmolar variation over time with a maximal effect after 10 min.

Chronic meningitis presenting with acute obstructive hydrocephalus

A previously healthy 24-year-old woman presented to the Emergency Department unresponsive with a Glasgow Coma Scale score of 4 and evidence of brainstem herniation. She was intubated and hyperventilated. Computed axial tomography scan of the brain demonstrated four-chamber hydrocephalus. Continued hyperventilation and mannitol diuresis were sufficient to arrest the impending herniation while emergent ventriculostomy was arranged. The patient recovered without sequelae and ultimately received a diagnosis of chronic idiopathic meningitis. This case highlights a rarely diagnosed disorder that presented with an acutely life threatening condition.

Sensitive and simple determination of mannitol in human brain tissues by gas chromatography-mass spectrometry

A simple, reliable and sensitive gas chromatographic-mass spectrometric method was devised to determine the level of mannitol in various human brain tissues obtained at autopsy. Mannitol was extracted with 10% trichloroacetic acid solution which effectively precipitated brain tissues. The supernatant was washed with tert.-butyl methyl ether to remove other organic compounds and to neutralize the aqueous solution. Mannitol was then derivatized with 1-butaneboronic acid and subjected to GC-MS. Erythritol was used as an internal standard. For quantitation, selected ion monitoring with m/z 127 and 253 for mannitol and m/z 127 for internal standard were used. Calibration curves were linear in concentration range from 0.2 to 20 microg/0.1 g and correlation coefficients exceeded 0.99. The lower detection limit of mannitol in distilled water was 1 ng/0.1 g. Mannitol was detected in control brain tissues, as a biological compound, at a level of 50 ng/0.1 g. The precision of this method was examined with use of two different concentrations, 2 and 20 microg/0.1 g, and the relative standard deviation ranged from 0.8 to 8.3%. We used this method to determine mannitol in brain tissues from an autopsied individual who had been clinically diagnosed as being brain dead. Cardiac arrest occurred 4 days later.

Emergency management of the head trauma patient. Principles and practice

Management of the severely brain-injured dog or cat can be frustrating, especially considering the lack of proven effective therapies for head trauma patients. A working knowledge of the basic pathophysiology of head trauma and intracranial pressure (ICP) dynamics is essential to the logical treatment of head traumatized patients. Prevention and correction of hypotension and hypoxemia are necessary for preventing progressive increases in ICP. Mannitol is recommended in most cases of severe head trauma, but there is little evidence to support the use of glucocorticoids in acutely brain-injured dogs and cats. The role of surgical intervention for head-traumatized dogs and cats is still uncertain, but may be beneficial in some cases. Aggressive, expedient treatment and attentive patient monitoring are key aspects of successfully managing canine and feline head trauma patients.