QW33-April 2025

Question: Select each option to validate with explanations

Clinical Case Scenario

A 60-year-old woman presents to the emergency department with persistent vomiting for 5 days. She has a history of hypertension, dyslipidaemia, chronic knee osteoarthritis, and pyloric stenosis due to long-term NSAID use. In the ED, she develops hypotension (BP 80/54 mmHg) and tachycardia (HR 115 bpm). On bedside POCUS assessment, her IVC diameter is 0.5 cm, which is collapsing to 30%. Lab results show:

Na⁺: 132 mmol/L
K⁺ : 2.8 mmol/L
Cl⁻ : 82 mmol/L
HCO₃⁻ : 38 mmol/L
pH: 7.52
Lactate: 4 mmol/L
Urea: 20 mmoL/L
Creatinine: 155 micromol/L (Baseline creatinine 95 micromol/L)

The ICU team advises aggressive resuscitation with 0.9% normal saline. After four litres of fluid administration along with 40 mmol of IV potassium chloride, BP improves to 102/64 mmHg, and follow-up labs are as follows:
Na⁺ : 135
K⁺ : 3.1 mmol/L
Cl⁻ : 97 mmol/L
HCO₃⁻ : 33 mmol/L
pH: 7.47
Lactate : 2.5 mmoL/L

Question: Which one of the following is the correct statement regarding fluid resuscitation in this patient?

A) 0.9% Normal Saline is preferred over Ringer's lactate because it corrects chloride depletion, facilitating renal excretion of excess bicarbonate and resolving metabolic alkalosis.

B) Ringer's lactate might be preferable to 0.9% normal saline, as large-volume saline resuscitation can worsen kidney injury.

C) Ringer lactate contains potassium; therefore, it is more suitable compared to 0.9 % Normal saline in this patient.

D) Hypertonic saline is needed to restore serum sodium levels

Right Answer: A) 0.9% Normal Saline is preferred over Ringer's lactate because it corrects chloride depletion, facilitating renal excretion of excess bicarbonate and resolving metabolic alkalosis.

Justification This patient has hypochloremic metabolic alkalosis (due to gastric losses) along with contraction metabolic alkalosis, which is a chloride-responsive type of metabolic alkalosis; therefore, it will be very responsive to 0.9 % Normal saline infusion. In fact, this is one of the few clinical indications where large-volume 0.9 % Normal saline is preferred over any other crystalloid solution.
0.9% Normal Saline replenishes chloride ions, allowing the kidney to excrete excess bicarbonate (via Cl⁻-HCO₃⁻ exchange in the collecting duct). Moreover, it restores intravascular volume, reducing aldosterone-driven K⁺ and H⁺ losses (which perpetuate alkalosis).
Option B is incorrect, as in states of hypochloremia, saline is preferred over Ringer’s lactate, which contains low chloride (109 mmol/L). Moreover, it has lactate, which will metabolise in the liver to generate more HCO₃, only to worsen metabolic alkalosis. And worsening metabolic alkalosis further reduces serum potassium. Hence, despite having “insufficient” potassium content (4 mmol/L) in RL, it may exacerbate hypokalaemia in our patient. Hence, option C is also incorrect. Hypertonic saline is unnecessary here because of two reasons. One patient does not have any neurological disturbance (symptomatic severe hyponatremia), and secondly, this mild hyponatremia is secondary to volume depletion; hence, mere volume resuscitation will reverse it.

Clinical pearl
Saline in large amounts has been harmful because it can lead to hyperchloremic (normal anion gap ) metabolic acidosis and renal dysfunction. The SMART trial in ED patients and the PLUS study in ICU patients show renal injury attributed to saline use. Still, there are very few indications of large-volume saline resuscitation in critical care and anesthesia, which should be remembered by all clinicians. (see table below.)

Wrong Answer: B) Ringer's lactate might be preferable to 0.9% normal saline, as large-volume saline resuscitation can worsen kidney injury.

Wrong Answer: C) Ringer lactate contains potassium; therefore, it is more suitable compared to 0.9 % Normal saline in this patient.

Wrong Answer: D) Hypertonic saline is needed to restore serum sodium levels

Reference:

1. Semler MW, Self WH, Wanderer JP, Ehrenfeld JM, Wang L, Byrne DW, Stollings JL, Kumar AB, Hughes CG, Hernandez A, Guillamondegui OD. Balanced crystalloids versus saline in critically ill adults. New England Journal of Medicine. 2018 Mar 1;378(9):829-39.
2. Finfer S, Micallef S, Hammond N, Navarra L, Bellomo R, Billot L, Delaney A, Gallagher M, Gattas D, Li Q, Mackle D. Balanced multielectrolyte solution versus saline in critically ill adults. New England Journal of Medicine. 2022 Mar 3;386(9):815-26.