January 2, 2025

63-year-old woman brought to an ED after being found in a stairwell on Monday morning, last seen Friday afternoon

By Med-Challenger · 2 minute read

A 63-year-old woman is brought to a remote rural emergency department by ambulance after being found in a stairwell on Monday morning. It is not known how long she was there, but she was last seen by her coworkers on Friday afternoon. She is not verbally responsive.

Workup shows an ischemic stroke in the posterior circulation and a hip fracture. The fracture may have been caused by her fall down the stairs from the stroke. Her arterial pH is 7.35 on initial arterial blood gas. The creatinine kinase level is elevated to 475 U/L. The sodium level is 130 mEq/L. Fluid resuscitation is immediately performed wide open upon her arrival because the patient’s initial blood pressure was 85/50 mm Hg.

At 120 minutes after her initial presentation, her blood pressure is 135/72 mm Hg, her heart rate is 68 beats/minute, and she is maintaining spontaneous respirations on 100% oxygen. Her oxygen saturation level is 99%. She is transferred to a larger facility, where a second arterial blood gas is obtained, which shows an arterial pH of 7.28 consistent with metabolic (not respiratory) acidosis. A repeat potassium level is 5.0 mEq/L.

What is a possible iatrogenic cause for this new metabolic acidosis?

Hyponatremia
Normal saline administration
Desaturation of the patient during transfer to computed tomography (CT)
Rhabdomyolysis

The correct answer is:

Normal saline administration

Educational Objective:

Name iatrogenic causes of pH drop during resuscitation from shock.

Key Point:

A possible iatrogenic cause for this new metabolic acidosis is the administration of normal saline. The point of this question is two-fold: (1) In the rush to perform resuscitation, it is not uncommon for healthcare professionals to forget to monitor the ongoing volume of fluid resuscitation, especially in transfer patients. This patient accidentally received 7 L of fluid before a nurse asked how many liters had been hung, and (2) using large amounts of normal saline can cause hyperchloremic metabolic acidosis.

Explanation:

This is a true case, and the reason for the metabolic acidosis was initially puzzling to the receiving facility.

Although the creatine kinase level was elevated, it seemed too small an elevation to create this much of a shift in pH. In addition, the potassium level was not critically elevated, also indicating that something other than rhabdomyolysis was occurring.

Desaturation during transfer to the table for CT imaging would not usually be of sufficient duration to cause acidosis, and, even if it did, respiratory acidosis--not metabolic acidosis--would be expected.

Reference:

Nicks BA, Gaillard JP. "Approach to Nontraumatic Shock." (Chapter 12) Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9e Eds. Judith E. Tintinalli, et al. McGraw-Hill, 2020, https://accessemergencymedicine.mhmedical.com/content.aspx?bookid=2353&sectionid=218079826

Evans, L., Rhodes, A., Alhazzani, W. et al. Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021. Intensive Care Med 47, 1181–1247 (2021). https://doi.org/10.1007/s00134-021-06506-y

This question appears in Med-Challenger Emergency Medicine Review with CME

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