Fill Me Up – An Arguement Using More Balanced Solutions

History of NS vs LR

In the great fluid infusion debate internist have favored normal saline, while surgeons have preferred lactated ringers. It looks like our surgeon friends may have gotten it right. Normal saline was never actually “invented” to be a volume replacement therapy. Wikipedia reports that it was discovered in 1831 by William Brooke O’Shaughnessy, a recent graduate of Edinburgh Medical School. He proposed in an article to The Lancet to inject cholera patients with highly oxygenated salts to treat the “universal stagnation of the venous system and rapid cessation of arterialisation of the blood” seen in severely dehydrated cholera patients. But a 2004 historical review by S. Awad in Clinical Nutrition came to the conclusion that “The currently used 0.9% saline solution is without convincing historical basis. Given that the composition of 0.9% sodium chloride is dissimilar to most solutions used in the past, and is in no way ‘normal’ or ‘physiological’, our current practice may be based on historical fallacy and misconception.” So it looks like normal saline was a future permeation of that original concoction. Interesting enough, Ringer formed a more physiologic solution with an optimal salt concentration which was able to maintain the contractility of frog cardiac muscle. Sadly Ringer’s solution was not widely adopted or used at the time.

Studies supporting Balanced Salt Solutions in the ICU

With the background out of the way let’s look at some recent data:

1.) Aksu, Ugur, et al. “Balanced vs unbalanced crystalloid resuscitation in a near-fatal model of hemorrhagic shock and the effects on renal oxygenation, oxidative stress, and inflammation.” Resuscitation 83.6 (2012): 767-773.

Results:  

1. Both the balanced and unbalanced crystalloid solutions successfully restored the blood pressure, but renal blood flow was only recovered by the balanced solution although this did not lead to improved renal microvascular oxygenation;
2. While unbalanced crystalloid resuscitation induced hyperchloremia and worsened metabolic acidosis in hemorrhaged rats, balanced crystalloid resuscitation prevented hyperchloremia, restored the acid-base balance, and preserved the anion gap and strong ion difference in these animals;
3. In addition balanced crystalloid resuscitation significantly improved renal oxygen consumption (increased VO(2))
4. However neither balanced nor unbalanced crystalloid resuscitation could normalize systemic inflammation or oxidative stress.

2.) Almac, Emre, et al. “The acute effects of acetate-balanced colloid and crystalloid resuscitation on renal oxygenation in a rat model of hemorrhagic shock.” Resuscitation 83.9 (2012): 1166-1172.

Results:

1. Unbalanced solution (NaCl, RA, and HES-NaCl) resuscitation led to hyperchloremic acidosis, while HES-RA (balanced solution) resuscitation did not.
2. Only HES-RA resuscitation could restore renal blood flow back to ∼85% of baseline level (from 1.9±0.1 ml/min during shock to 5.1 ml±0.2 ml/min 60 min after HES-RA resuscitation) which was associated with an improved renal oxygenation albeit not to baseline level.
3. At the end of the protocol, creatinine clearance was decreased in all groups with no differences between the different resuscitation groups.

3.) Bellomo, Rinaldo, et al. “Association between a chloride-liberal vs chloride-restrictive intravenous fluid administration strategy and kidney injury in critically ill adults.” Jama 308.15 (2012): 1566-1572.

Results:

1. Mean serum creatinine level increase while in the ICU was higher for chloride liberal solution than with chloride restrictive solution (P = .03)
2. The incidence of injury and failure class of RIFLE-defined AKI was 14% in control group vs 8.4% in the chloride restrictive group (P = <00.1)
3. The use of RRT was 10% in the control group vs 6.3% chloride restrictive group (P = .005).
4. There were no differences in hospital mortality, hospital or ICU length of stay, or need for RRT after hospital discharge.

There are also some smaller non-randomized prospective cohorts that show an increased mortality in critically ill patients with hyperchloremia.
So in the end what should we take from this? Looks like we should consider starting sicker patients in the ICU on balanced salt solutions when they are in need of volume repletion especially given the fact that AKI in the ICU is associated with an increase in mortality. Per Rivers major study of early goal directed therapy (CVP 8-12, MAP => 65, SvO2 => 70%) within the first 6 hours of patients arrival in the ED. Of note, once patient are no longer fluid responisive to volume expansion aggressive resuscitation should be held as this is associated with worse outcomes. Per the ARDS network data, after shock has resolved a more conservative approach (which we discussed here previously) has been associated with lower ICU days and quicker weaning from the vent.
-Adrian