Intravenous Fluids¶

Chandler Montgomery

Indications for intravenous fluid¶

Osmolarity: osmoles of solute per L of solution
Tonicity: ability to induce movement of water across a membrane
Buffer: anions such as lactate, acetate, gluconate which are metabolized to bicarbonate in vivo with the goal of sustaining normal plasma pH

Isotonic fluids used for volume resuscitation
After ~ 30 mins, redistribute such that only 25% remains w/in intravascular space
Balanced solutions (ex: Lactated Ringer’s, Plasma-Lyte)= have electrolytes concentrations similar to plasma
NS may lead to renal vasoconstriction, AKI, hemodynamic instability, increased mortality
- SMART and SALT-ED: balanced solutions had lower rates of death, new renal replacement therapy, or persistent renal dysfunction compared to NS
Situations where NS may be preferred:
- Cerebral edema/traumatic brain injury
- Hypovolemic hyponatremia
- Pre-existing hypochloremic metabolic alkalosis (e.g. after vomiting or over diuresis)
Notes on LR
- The small amount of K in LR (~4 mEq/L) is unlikely to significantly exacerbate hyperkalemia
- Lactate in LR is sodium lactate. No hydrogen ions are being added to plasma

Fluid	Na	Cl	K	Ca	Mg	Glucose	Buffer	Osmolarity	Tonicity
Plasma	~140	~100	~4	~2.4	1.0	~0.85	Bicarb ~24	~290	NA
Normal 0.9% saline	154	154	0	0	0	0	0	308	Isotonic
Lactated Ringer’s	130	109	4.0	2.7	0	0	Lactate 28	273	Isotonic
Plasma-Lyte/ Normosol	140	98	5.0	0	3.0	0	Gluconate 23 Acetate 27	295	Isotonic
D5W + 150 mEq HCO3-	150	0	0	0	0	50	Bicarb 150	300	Isotonic
3% Saline	513	513	0	0	0	0	0	1026	Hypertonic
D5W	0	0	0	0	0	50	0	252	Hypotonic

Albumin: extracted from human plasma
5% - Used after plasma exchange
25% - raises oncotic pressure and restore intravascular volume
- Uses: Post-LVP, diagnosis and treatment of hepatorenal syndrome, SBP (see Hepatology)
- Evidence base for use outside of above indications is poor (SAFE trial)
Blood Products: Packed RBCs, FFP, cryoprecipitate, etc