By Eleanor McDermid, Senior medwireNews Reporter
Prehospital intravenous loading with lactated Ringer's (LR) solution may reduce the chances for survival with good neurologic outcome among patients with out-of-hospital cardiac arrest (OHCA), an observational study suggests.
The finding emerges from a prospective study of 531,854 Japanese OHCA patients. In an analysis of 76,293 patients who were given LR solution and 76,293 patients who were matched for propensity to receive the solution but not actually given it, 1-month outcomes were worse in patients given LR solution, despite an increased rate of prehospital return of spontaneous circulation (ROSC).
However, Akihito Hagihara (Kyushu University Graduate School of Medicine, Fukuoka, Japan) and team stress that, unlike randomization, propensity matching only accounts for measured variables. They also note that they lacked data on treatment after patients arrived at hospital.
The rate of prehospital ROSC was 6.3% versus 5.2% among patients given and not given LR solution. "We believe that intravenous LR solution infusion leads to higher hydrostatic pressure and higher blood pressure, which could result in increased ROSC before hospital arrival," write the researchers in PLoS Medicine.
Yet the 1-month survival rate was significantly lower among patients given LR than those not given LR, at 43.30% versus 46.83%. This association disappeared after further adjustment for other variables, but there were significant independent differences for survival with a Cerebral Performance Category of 1 or 2, at corresponding rates of 21.57% versus 28.35%, and for survival with an Overall Performance Category of 1 or 2, at 21.48% versus 28.30%.
The researchers say that, based on previous research, "most patients with OHCA would have developed lactic acidosis by the time of hospital admission." They therefore speculate that "prehospital LR use could worsen advancing acidemia in patients with OHCA, and adverse consequences of acidemia can occur independently of whether the acidemia is of metabolic, respiratory, or mixed origin."
In support of this, previous studies have linked higher lactate concentrations at the time of hospital admission to the likelihood for serious neurologic impairment among patients who survived to 1 month.
In Japan, paramedics are required to use LR solution for prehospital intravenous loading, and this was used in more than 90% of cases. "Future studies will need to determine whether administration of fluids other than LR is associated with beneficial outcomes," say Hagihara et al.
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