Base Excess (BE)

More on the deleterious effect of “(ab)normal” saline

Posted by n6949u on October 11, 2013
Posted in: Base Excess (BE), Fluid resuscitation, Hyperchloremic Acidosis, Iatrogenic Acidosis. Tagged: , , . Leave a comment

An interesting article and an editorial from Anesthesia Analgesia:

It is becoming more clear that the hyperchloremia associated with infusion of normal saline is not benign:

Hyperchloremic metabolic acidosis is not a benign, self-limiting, metabolic disturbance. We found that acute postoperative hyperchloremia in patients undergoing noncardiac surgery was associated with increased mortality, renal dysfunction, and length of hospital stay.

As the editorial points out, several things are clear:

  1. hyperchloremia is more common with 0.9% saline than with balanced crystalloid solutions
  2. hyperchloremia is associated with worse outcomes
  3. there are better alternatives to 0.9% saline in most clinical situations (excluding hypochloremic metabolic alkalosis)
  4. until an adequately powered randomized clinical trial proves us wrong, 0.9% saline will not be our crystalloid of choice for intravascular volume resuscitation in surgical patients.

Clarification of Base Excess and the Need for NaHCO3 Infusion

Posted by n6949u on September 1, 2013
Posted in: Base Excess (BE), Blood gas interpretation, Hyperchloremic Acidosis. Leave a comment

Base Excess (BE) is a calculated value:

BE (mEq/l) = HCO3 (observed) + 10 [pH (observed) -7.40] – 24

The BE has a range of normal of -4 to +4.

The reason for this is that the calculation is based on the pH and the  bicarbonate, each of which has its own normal range.

The normal range for HCO3 is 21-28 mEq/L, and that of  the pH is 7.35-7.45.

Remember that in trauma we deal almost exclusively with metabolic acidosis.

Therefore, we are concerned only with BEs that are MORE NEGATIVE than MINUS FOUR.

A BE less negative than -4 or less, does not need to be treated with sodium bicarbonate.

For example, a 70 Kg patient with a BE of -4 would appear to require ([0.3X70X-4]/50) or 1.7 amps of NaHCO3, when in fact (s)he requires no treatment.

Look also at the chloride and the lactate. When these are more than “mildly” elevated, and there is a BE more negative than -4, then NaHCO3 treatment is indicated.