1. Phillip Howells, Vikram Anumakonda and Nikhil Bhasin
Hypertonic Saline and Head Injury: Trends of Use in Adult Intensive Care Units in the United Kingdom
Phillip Howells, Vikram Anumakonda and Nikhil Bhasin
Department of Intensive Care, University Hospital, Coventry, UK. Contact
Introduction.
Severe traumatic brain injury is an important cause of mortality, morbidity and intensive care workload, and raised intracranial pressure (ICP) is a significant pathophysiological process contributing to this. Non-pharmacological methods to reduce ICP include nursing with 20˚ head-up, optimising cardiorespiratory parameters, avoidance of head and neck constriction, paralysis and active cooling and glucose and seizure control. For many years, mannitol has been the mainstay of pharmacological interventions for the reduction of raised ICP in head injured adults1. However, hypertonic saline now offers the promise of either an adjunct or alternative therapy2.
Currently, there is an inadequate evidence base to either select one therapy over another, or provide a coherent strategy for use of the two agents together. This survey was conducted to investigate the trends for hypertonic saline use in adult intensive care units in the United Kingdom.
Methods.
A list of British hospitals with neurosurgical services was taken from the Association of British Neurological Surgeons’ website3. The 32 hospitals listed were contacted by telephone between November and December Data from the hospital at which the authors are based were already known. Medical and nursing personnel in intensive care units or neurosurgical high-dependency wards were asked a short standardised questionnaire to ascertain their units’ local practice. Staff at one unit felt their inclusion inappropriate as its neurosurgical service had been withdrawn; at three others, it was not possible to acquire the information required by telephone within the timeframe of the survey.
Results.
Of the 28 units for which data were obtained, 19 units had a standardised protocol for the management of head injuries, whilst nine did not.
As shown in figure 1, 29% of units did not use hypertonic saline at all. Hypertonic saline was used first line in 18% of units, second line after mannitol in 25%, whilst in 14% of units its use was either outside protocol or down to individual consultants’ preferences. Units varied as to whether this was the discretion of neurosurgeons, intensivists or both. Five units used hypertonic saline outside their standardised protocol (figure 2). Several units reported using it only if all other measures bar decompressive craniectomy had been exhausted. One unit reported using hypertonic saline primarily for the management of cerebral salt wasting syndrome, whilst using only occasionally for intractable intracranial hypertension.
Of units using hypertonic saline, 15% of units used hypertonic saline within the first 48 hours only, whilst 65% routinely used it past that time (figure 3). The remaining 20% reported their practice was variable in this regard.
It was difficult to quantitatively assess the endpoints that different units used for therapy, as the majority monitored multiple values specifically when using hypertonic saline, and it appears the majority of protocols did not utilise goal-directed therapy. Units generally reported their intensivists and neurosurgeons were guided by global assessments of physiological parameters and clinical condition rather than any individual measure. One unit reported variable monitoring and action on parameters depending on consultant preference, whilst all others reported serum sodium and haemodynamic monitoring, most cerebral perfusion pressure and osmolalities and two haematocrit.
50% of units reported mandatory use of invasive intracranial pressure monitoring when administering hypertonic saline, whilst 25% reported this was used in the “majority” of their patients, and a further 25% reporting use “sometimes” or “variably” (figure 4). Guidelines for severe traumatic brain injury suggest mannitol should only be used before intracranial pressure monitoring if the clinical picture suggests transtentorial herniation or progressive neurological deterioration without a likely extracranial cause1.
Discussion.
This survey has shown there is a broad variation in use of hypertonic saline across neurosurgical services within the United Kingdom. This may reflects the relative recent availability of this drug4 compared to its main alternative, mannitol, and the current lack of large randomised trials to objectively clarify its role in both raised intracranial pressure and cerebral salt wasting syndrome.
A recent review by Strandvik2 stated that there was sufficient evidence to show that hypertonic saline is effective at reducing intracranial pressure, but this has not translated to improvements in neurological outcome or survival. However, the studies undertaken were regarded as heterogeneous and at risk of bias with small numbers of patients recruited.
Few studies have reported adverse events, but concerns include hyperosmolar states and osmotic demyelination syndrome as well as acute fluid overload from plasma expansion. Hypokalaemia and hyperchloraemic acidosis are potential electrolyte problems. However, studies so far reported have reported no significant side effects or iatrogenic harm. There have been a few studies with safety as a primary outcome; however all of those reviewed were underpowered to detect adverse events2.
We conclude British practice in management of raised intracranial pressure with pharmacological agents in head-injured patients is variable. Randomised control-trials are required to ascertain the optimum use of hypertonic saline for patients with severe traumatic brain injury1,4.
Acknowledgements.
The authors would like to thank all members of staff at the units contacted for taking the time to assist with this project.
References.
1. Brain Trauma Foundation, et al. Guidelines for the Management of Severe Traumatic Brain Injury, Journal of Neurotrauma, Volume 24 Supplement 1 S Strandvik, GF, Hypertonic saline in critical care. Anaesthesia, Association of British Neurological Surgeons [Internet]. [update unknown]. Association of British Neurological Surgeons; [accessed 2010 Dec 28]. Available from 4. Latorre, Julius, and Greer, David (2009). Management of Acute Cranial Hypertension: A Review. The Neurologist, 15(4),