SGEM#326: The SALSA Study: Hypertonic Saline to Treat Hyponatremia

Date: April 6th, 2021 Guest Skeptic: Dr. Casey Parker is a Rural Generalist from the NW of Australia. He is a GP by training but works in Emergency Department, Anaesthesia, Internal Medicine and Paediatrics. Dr. Parker is currently studying to become a Sonologist. He has a wonderful #FOAMed blog and podcast called Broomedocs and also work with me on the Primary Care RAP team. Reference: Risk of Overcorrection in Rapid Intermittent Bolus vs Slow Continuous Infusion Therapies of Hypertonic Saline for Patients With Symptomatic Hyponatremia: The SALSA Randomized Clinical Trial. JAMA Intern Med 2021 Case: A 60-year-old man presents to the emergency department (ED) after his wife found him to be drowsy and confused at home. He had been vomiting that morning. He had a background of hypertension treated with a thiazide diuretic. His wife reports that he had experienced diarrhoea in the week prior to this presentation.  On arrival to the ED his vitals are normal aside from a decreased level of consciousness and he is found to have a serum sodium concentration of 118 mmol/L.  You are unsure as to the best way to correct his sodium and are aware that rapid overcorrection may lead to an osmotic demyelination syndrome.  However, he is also at risk of a seizure and further harm at this level. Background: The most common electrolyte abnormality in clinical practice is a low sodium level (hyponatremia). This imbalance occurs in 14% to 42% of admitted patients. There is a high mortality associated with hyponatremia [1-3].  Symptomatic hyponatremia has traditionally been treated with a careful slow continuous infusion of hypertonic saline. This has been to prevent the horrible adverse event called osmotic demyelination syndrome (ODS). ODS includes both central pontine myelinolysis and extrapontine myelinolysis. In recent times several expert consensus guidelines have recommended the use of rapid, intermittent boluses of hypertonic saline  instead of a slow continuous infusion [3,4].   There is very little randomized data to prove the superiority of either strategy prior to the SALSA trial.  Most of the trials were done in marathon and ultra-marathon runners whom we do not see very often in the ED [5-7]. Using a fixed bolus has a number of potential benefits [8-9]:  Efficacy: Ability to reach rapid partial correction hyponatremia Safety: It can limit the risk of overcorrection that can commonly occur with continuous infusion of hypertonic saline No Math: It omits need for calculations Clinical Question: When treating symptomatic hyponatremia what are the risks of overcorrection in patients using either a slow continuous infusion vs. a rapid intermittent bolus of hypertonic saline strategy? Reference: Risk of Overcorrection in Rapid Intermittent Bolus vs Slow Continuous Infusion Therapies of Hypertonic Saline for Patients With Symptomatic Hyponatremia: The SALSA Randomized Clinical Trial. JAMA Intern Med 2021 Population: Patients 18 years of age and older with moderate or severe symptomatic hyponatremia (corrected serum sodium [sNa] of 125 mmol/l or less). Moderate symptoms include nausea, headache, drowsiness, general weakness and malaise. Severe symptoms include vomiting, stupor, seizure, and coma (Glasgow Coma Scale [GCS] score ≤8).  Exclusions: Primary polydipsia; pregnant or breastfeeding; anuria, arterial hypotension, liver disease, uncontrolled diabetes mellitus; or had a history of cardiac surgery, acute myocardial infarction, sustained ventricular tachycardia, ventricular fibrillation, acute coronary syndrome, cerebral trauma, and increased intracranial pressure within 3 months prior to randomization.  Intervention: Rapid intermittent bolus (RIB) groups received 2ml/kg of 3% saline over 20 minutes. Patients were dichotomized into moderate or severe hyponatremia. The severely symptomatic patients had 2 separate boluses delivered initially.