Critical Care recently published a small study on hemorrhagic shock and fluid replacement using rats entitled Volume replacement with Ringer-lactate is detrimental in severe hemorrhagic shock but protective in moderate hemorrhagic shock: studies in a rat model. The study authors compared fluid resuscitation outcomes for Ringer’s Lactate and Ringer’s Saline in rats with moderate and severe shock. Except for a control group of 6, the rats were divided into groups of 8, put into shock by removing a predetermined amount of blood from them using a syringe, and then treated using either Ringer’s Saline or Ringer’s Lactate.(1)
Of the rats in the study:
- 2 out of 8 rats with moderate shock survived when given Ringer’s Saline.
- 8 out of 8 rats with moderate shock survived when given Ringer’s Lactate.
- 2 out of 8 rats with severe shock survived when given Ringer’s Saline.
- 0 out of 8 rats with severe shock survived when given Ringer’s Lactate.
- 6 out of 6 rats in the control group survived.
The authors did some relatively sophisticated statistical analysis that was also not really completely reported, possibly because the study is still in provisional stage and doesn’t have its graphs yet. They also drew some pretty expansive conclusions from their data, saying:
The present study clearly demonstrates that (Ringer’s Lactate) is toxic in the resuscitation of severe hemorrhagic shock but protective in the treatment of moderate hemorrhagic shock. . .
This is the kind of laboratory-based study that has to be handled with care in a lot of ways. For one thing, it’s tiny: each study group only contained 8 individuals. That’s not large enough to make changes to what we do in the clinical setting on. It’s also an animal model study, and just because something works one way in rats doesn’t mean it works that way in humans. Finally, the study also has some pretty hairy design issues: instead of instead of a moderate shock control group and a severe shock control group which wouldn’t receive any treatment, the authors just kept six rats in a cage and called that their control. We don’t know how many rats would have survived from either group without any fluids being given.
The results they got at the moderate shock level are really intriguing. 8 vs 2 is a big enough difference to suggest a real difference in outcome between Ringer’s Lactate and Ringer’s Saline. That said, we can’t say anything useful about fluid resuscitation in severe shock because this study is just too small and so are the differences in outcome (2 vs 0 out of 8 rats surviving), despite the authors’ statistical analysis and conclusions. Given the huge difference in outcomes for moderate shock, it would be really nice to see some larger, better-designed follow-up research on lactate vs. saline.
Even though this small study reached a negative conclusion about Ringer’s Lactate in severe shock, several previous studies have found Ringer’s Lactate is superior to Normal Saline for fluid resuscitation in both moderate and severe shock,(2–4) In prehospital care, especially at the BLS level, we tend to just say “Normal Saline and Ringer’s Lactate are basically the same thing” and leave it at that, but understanding crystalloid volume replacement is something the NOCP puts within the scope of what BLS providers are expected to understand.(5) Even if the ultimate decision about which fluid we carry is made by our medical directors, it might be time for us as a profession to start paying more attention to the differences.
1. Hussmann B, Lendemans S, Groot H de, Rohrig R. Volume replacement with Ringer-lactate is detrimental in severe hemorrhagic shock but protective in moderate hemorrhagic shock: studies in a rat model. Crit Care. 2014 Jan 6;18(1):R5.
2. Healey MA, Davis RE, Liu FC, Loomis WH, Hoyt DB. Lactated ringer’s is superior to normal saline in a model of massive hemorrhage and resuscitation. J Trauma. 1998 Nov;45(5):894–9.
3. Phillips CR, Vinecore K, Hagg DS, Sawai RS, Differding JA, Watters JM, et al. Resuscitation of haemorrhagic shock with normal saline vs. lactated Ringer’s: effects on oxygenation, extravascular lung water and haemodynamics. Crit Care Lond Engl. 2009;13(2):R30.
4. Todd SR, Malinoski D, Muller PJ, Schreiber MA. Lactated Ringer’s is superior to normal saline in the resuscitation of uncontrolled hemorrhagic shock. J Trauma. 2007 Mar;62(3):636–9.
5. Paramedic Association of Canada. National Occupational Competency Profile [Internet]. 2011. Available from: http://paramedic.ca/nocp/
Last updated: January 8, 2014 at 23:35 pm