IV Fluids – Study Notes

Peripheral IVs in Medicine 💊 

• Most IVs not used: Only ~17–20% of IVs placed in ED are later used.

• Cost & resource issue → potential to protocolize when IVs are necessary.

• “Safety issue” for admission w/out IV is largely a myth.

• Takeaway: Don’t reflexively place IVs—most patients don’t need them.

Normal Saline vs. Balanced Crystalloids

• Normal saline ≠ plasma:

  • Na⁺ 154 mEq/L, Cl⁻ 154 mEq/L (too much chloride vs. plasma).

  • Hyperchloremia → macula densa interprets as volume depletion → afferent arteriole constriction → ↓ renal perfusion, cortical swelling, kidney injury.

• Face validity: explains why saline can harm kidney perfusion.

Trials

• SPLIT (2015, JAMA):

  • Saline vs Plasma-Lyte in ICU patients.

  • Low fluid volumes (~2 L), not very sick patients.

  • No difference in outcomes.

  • Limit: underpowered for sick patients/high-volume use.

• SMART (2018):

  • Saline vs LR in ICU patients.

  • Primary outcome (mortality) negative.

  • Secondary outcome (MAKE-30: death, dialysis, ↑ creatinine) better with LR.

  • Signal: LR may reduce kidney events, not worse than saline.

• SALT-ED (2018):

  • Saline vs LR in non-ICU admissions.

  • Primary outcome negative, but MAKE-30 improved with LR (driven by ↑ creatinine).

  • Takeaway: LR not worse, possibly better for renal outcomes.

Operational Issues

• Rapid switch to LR can cause:

  • Delays in care (supply chain, availability).

  • Drug incompatibilities (notably ceftriaxone and blood products).

• Must be implemented systematically, not ad hoc.

Sepsis & Large-Volume Resuscitation

• Retrospective data suggest dose-dependent mortality benefit with balanced crystalloids.

• Sickest patients and high-volume resuscitation show clearest signal.

Pediatrics

• Kids often get lower fluid volumes → harder to see benefit.

• Outcomes align with adult data: balanced crystalloids safe, may be better in sick/high-volume cases.

Acute Pancreatitis

• Old teaching: aggressive fluids + NPO.

• Current best practice: early feeding + moderate fluid resuscitation.

• LR preferred:

  • ↓ inflammatory markers (CRP, ESR, procalcitonin).

  • Lower SIRS rates in mild pancreatitis.

  • Some studies: improved clinical outcomes, especially in severe cases.

• NS → more inflammation, metabolic acidosis.

Diabetic Ketoacidosis (DKA)

• Saline vs ½ NS in kids: outcomes the same (fluid rate/type didn’t matter much).

• LR vs NS in kids with DKA:

  • Concern: LR has sodium bicarbonate precursor (theoretical ↑ risk cerebral edema).

  • Trial showed better outcomes with LR (fewer hyperchloremic acidosis complications).

  • Takeaway: LR safe, may be better in DKA too.

Big Picture

1. Most ED patients don’t need IV fluids at all → encourage PO when possible.

2. If starting a new hospital, LR should be stocked as primary crystalloid.

3. LR is safe, possibly superior for:

   • Large-volume resuscitation

   • Sick patients (sepsis, shock)

   • Pancreatitis

   • DKA

4. NS is still acceptable, but risk of hyperchloremic metabolic acidosis and renal hypoperfusion.

5. Evidence-informed practice (not just RCTs) + clinical judgment = best approach.

6. “Dad medicine” mindset → for family/critical patients, use LR when evidence shows even a small benefit.

Summary:

• Most IVs = unnecessary.

• NS is not “normal” → risk kidney harm via hyperchloremia.

• LR is at least as safe, often better—especially in high-volume/sick patients, pancreatitis, and DKA.

• Operational rollout must be thoughtful to avoid new harms.