Hypertonic saline (HTS) solutions have been shown to reliably and safely reduce raised intracranial pressure (ICP) in patients with acute traumatic brain injury (TBI) (Fisher 1992; Härtl 1997). HTS solutions even lowered ICP in patients who were refractory to standard therapeutic approaches (Horn 1999; Kerwin 2009; Khanna 2000; Worthley 1988). Whether HTS solutions may be superior to other ICP-lowering agents for individuals with acute TBI remains a controversial issue.
Description of the condition
TBI is a major cause of death and disability worldwide (Corrigan 2010). Intracranial hypertension secondary to TBI is well known to have a profound influence on outcome, and severe intracranial hypertension was associated with higher morbidity in patients with TBI (Miller 1977). In a review of studies of the value of ICP in predicting outcomes in TBI, the rate of death was 18.4% for participants with ICP less than 20 mmHg and 24.8% for participants with ICP between 20 mmHg and 40 mmHg but 55.6% for those with ICP greater than 40 mmHg (Treggiari 2007). Achieving a sustained reduction in ICP remains a focus of neurocritical care.
Description of the intervention
Currently available medical treatments for raised ICP include hyperosmolar therapy, sedation and paralysis, hyperventilation, barbiturate coma, hypothermia, steroids and surgical intervention (Rangel-Castillo 2008). Hyperosmolar therapy is the cornerstone of pharmaceutical treatment for intracranial hypertension. Hyperosmolar therapy can be defined broadly as the use of hypertonic solutions to reduce accumulated fluid in the brain. Reported concentrations of HTS for clinical use range from 2% to 23.5%. HTS solutions are often used when elevated ICP is resistant to other intracranial pressure–lowering agents, especially in patients with head trauma or postoperative cerebral oedema (Ziai 2007).
How the intervention might work
The ICP-lowering mechanisms of HTS solutions are believed to be due to their effects on microcirculation and osmotic action (Ziai 2007). HTS solutions decrease serum viscosity and hematocrit, leading to an increase in cerebral perfusion and causing cerebral arteriole vasoconstriction that reduces cerebral blood volume (CBV) and ICP. Water always flows from body compartments with low osmolality to those with higher osmolality. HTS solutions increase plasma osmolarity after administration, thus promoting gradual movement of water from tissues into the circulation. As fluid moves into the vascular space and is carried away by the blood, the brain shrinks and ICP is reduced.
Why it is important to do this review
Increasing evidence shows that HTS solutions should be considered gold standard medical therapy for ICP (Marko 2012). This review will be undertaken to enable improved understanding of the efficacy and potential side effects of HTS solutions for people with acute TBI.