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Hyperchloremic acidosis caused by large 0.9% saline infusions seems to be benign, unless it is confused with hypoperfusion. The pH values greater than 7.20 do not seem to have major pathophysiologic implications in the clinical setting we describe. Nevertheless, we believe that hyperchloremic acidosis caused by a 0.9% saline infusion should be treated to provide a BE close to zero at the end of surgery (or, alternatively, lactated Ringer’s solution should be used). In our experience in the early postoperative period, metabolic acidosis caused by hyperchloremia and respiratory acidosis caused by opiate analgesics may become additive and result in pH values much less than 7.20. A systematic analysis of this topic might provide valuable information. Scheingraber, et al
In trauma patients who respond to bolus crystalloid administration, hyperchloremic acidosis, is the most common cause of metabolic acidosis and it is often confused with an acidosis owing to hypoperfusion. It is obviously important to differentiate between the two, because hyperchloremic acidosis is relatively benign and that owing to hypoperfuison dangerous. These two types of acidosis are easily distinguished.
Hyperchloremic acidosis: Base Excess is negative, bicarbonate is low, chloride is elevated, lactic acid is normal.
Acidosis due to hypoperfusion: Base Excess is negative, bicarbonate is low, chloride is normal, lactic acid is elevated.
So don’t just look at the bicarbonate and assume that if it is low, the cause is hypoperfusion and lactic acidosis. Our ABG lab reports the Base Excess, bicarbonate, chloride, and lactic acid (if you ask for it). Look at them all to determine the cause of the acidosis. In the majority of cases an elevated chloride +/- an elevated lactate will account for nearly all of the negative Base Excess.
Hyperchloremic acidosis stems from giving too much 0.9% NaCl. Normal Saline is the solution given to trauma patients by paramedics and emergency room physicians. By the time these patients arrive in the operation room, they have been “flooded” with Normal Saline and already have a hyperchloremic acidosis.
Hyperchloremic acidosis can be mitigated/avoided by stopping all Normal Saline infusions and switching to Plasmalyte as soon as possible. Unlike Lactated Ringers, Plasmalyte contains no calcium and it is compatible with blood and blood product transfusions.
Hyperchloremic acidosis is also referred to as “dilutional acidosis.” I suspect this refers to dilution of plasma bicarbonate by volume administration. However the decline in the bicarbonate occurs only with volume administration of Normal Saline and not with Lactated Ringers or Plasmalyte. (see Figure 1 and Table 2, Scheingraber, et al)
The reader who wants more detail is referred to this treatise (Yearbook of Intensive Care and Emergency Medicine 2009, pp 221-232): hyperchloremic acidosis.
Briefly, strong cations predominate in the body leading to a net positive plasma charge that is described as the Strong Ion Difference (SID) by the following formula: SID (+40) = [Na+ + K+ + Ca2+ + Mg2+] – [Cl- + lactate-].
This net positive charge must be counterbalanced with an equal negative charge to satisfy the Law of Electrical Neutrality.
The balancing negative charge derives from nonvolatile weak acids is accounted for
as Atot (total weak acids). In plasma, these weak acids include albumin and inorganic phosphates.
Here is a simple question. If NS is so useful in the field and Emergency Room, why don’t we use it routinely in the operating room? Why do we use LR instead?
Values are mEq/L
Values are mg/100mL
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