Although hypertonic saline solution helps control intracranial hypertension and symptomatic hyponatremia in critically ill patients with sub arachnoid hemorrhage (SAH), such treatment appears to come at a cost: Hypertonic saline, or high sodium exposure, significantly increases the odds of developing acute kidney injury (AKI) in this already-fragile patient population.
“When you look at subarachnoid hemorrhage, you see that we’ve gotten a lot better at fixing the actual aneurysm, so now we’re beginning to pay attention to all the other things that make a difference to patient outcomes,” said Avinash B. Kumar, MD, associate professor of clinical anesthesiology at Vanderbilt University, Nashville, Tenn.
“In recent years, hypertonic saline has been shown to be more effective than mannitol in managing intracranial hypertension that often accompanies subarachnoid hemorrhage,” he said. “Nevertheless, we don’t have a lot of data on what this actually does to the non-neurologic aspects of care of these patients.”
With that in mind, Dr. Kumar and his co-investigators retrospectively examined data from a cohort of 736 adults admitted to the institution’s neurosciences ICU between 2006 and 2012. Each patient was at least 18 years of age and had been admitted for at least 72 hours after a SAH. The researchers defined AKI using the Acute Kidney Injury Network serum creatinine criteria between 72 hours and 14 days after admission. Sodium exposure was captured as the running maximum daily serum sodium concentration. Sodium exposure was used as a surrogate for hypertonic saline therapy.
As Dr. Kumar reported at the 2014 annual meeting of the International Anesthesia Research Society (abstract S-138), 64 patients (9%) developed AKI. Not surprisingly, these individuals had longer hospital lengths of stay (15.6±9.4 days) than their counterparts who did not develop AKI (12.5±8.7 days). Furthermore, the chances of dying were more than double in the patients who developed AKI (odds ratio, 2.33).
After adjusting for a number of possible confounding factors, sodium exposure was also found to be significantly associated with the risk for developing AKI. Indeed, for each 1 mEq/L increase beyond 150 mEq/L in the running maximum daily serum sodium, the hazard of developing AKI was increased by 5.4% (95% confidence interval, 1.4-9.7).
“Among all these signals, the one that stood out the most was the maximum daily sodium over a 14-day period,” Dr. Kumar said in an interview with Anesthesiology News. “So if you choose to give someone hypertonic saline as a way to control intracranial pressure, it’s worth bearing in mind that hypernatremia is a significant risk factor for developing AKI.” (Figure.)
Interestingly, after performing regression analysis, the researchers did not find any significant correlation between contrast exposure and kidney injury. “One possible explanation for this may be the way we manage fluids in these patients,” he added. “In most non-neuro[logic] ICU patients, the plan usually is diuresis after the initial resuscitation. But in subarachnoid hemorrhage patients, hypovolemia worsens vasospasm. So these patients tend to have a more liberal fluid strategy.”
Given the relatively low incidence of SAH, conducting a prospective, randomized trial presents significant challenges. “But I think this is new information that’s valuable for intensivists and clinicians who take care of this patient population.”