Journal Club: March 2018
The SALT-EM Study: Balanced Crystalloids Vs Saline in Non-critically Ill Adults
The SALT-ED trial is a pragmatic cluster-randomised multiple-crossover study performed at the Vanderbilt Emergency Department, USA. The default resuscitation fluid was alternated monthly between saline and balanced crystalloids (Lactated Ringer's [LR] or Plasma-Lyte).
This study involved patients being admitted to the hospital ward with a primary outcome of days alive after discharge before the 28th day. A secondary endpoint was adverse kidney events: a composite of death, dialysis, or doubling of the creatinine within one month.
The study included 13,347 patients receiving a median of one litre of fluid. 95% of patients randomised to receive balanced crystalloid were treated with LR, so this was effectively a trial of saline vs LR. Saline increased the risk of death or renal failure (5.6% vs 4.7%, p=0.02), with the difference driven mostly by differences in renal failure. As might be expected, the subgroup of patients with renal injury at admission was more susceptible to harm from saline (37.6% vs 28% adverse kidney events, p<0.001).
The SALT-ED trial confirms that saline increases the risk of renal failure, even at a low dose, in stable patients; and the large number of participants enabled detection of small differences in renal failure. While an effect size of 1% would normally be considered trivial (the number needed to harm from saline is 111), the larger number of patients that receive the intervention would indicate that harm is quite significant at a population-level over time.
“Normal” saline is a hypertonic, acidotic fluid. There is no physiologic rationale for its use as a resuscitative fluid.
There are many potential problems related to saline. These include causing hyperchloremic acidosis, hyperkalaemia, hemodynamic instability, renal malperfusion, systemic inflammation, and hypotension.
Numerous small RCTs have emerged over the past few years which highlight various problems with saline resuscitation.
The SMART and SALT-ED trials are large, multiple-crossover trials which compare saline versus balanced crystalloids among critically ill and non-critical patients. Both studies found a 1% increase in death or renal failure with the use of saline.