Chapter 6: Intravenous Fluids and Transfusion Medicine
What is the daily maintenance fluid requirement for a 80-kg patient?
The answer is C. Using the “4/2/1” rule the patient will require: 4 mL/kg/hr for the first 10 kg; 2 mL/kg/hr for the next 10 kg; and 1 mL/kg/hr for the remaining weight greater than 20 kg. Total hourly fluid requirements = 40 mL + 20 mL + 60 mL = 120 mL/hr. Daily requirements = 120 mL/hr × 24 hours = 2880 mL.
Ref: Miller RD. Miller's Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2015.
When transfusing packed red blood cells (PRBCs) it is often recommended to Avoid which of the following crystalloids?
(A) normal saline (0.9% NS)
(B) lactated Ringer's solution (LR)
(D) 5% Dextrose in water (D5W)
(E) D5W + 1/2 NS (0.45% NS)
The answer is B. Lactated Ringer's (LR) contains 130 mEq/L sodium, 4 mEq/L potassium, 3 mEq/L calcium, and 109 mEq/L chloride. It is recommended to avoid LR with citrated blood products, as theoretically the calcium in the LR can chelate the citrate anticoagulant and lead to clot formation. (However, it should be noted that this common recommendation is in contrast to many research studies that show LR may be used safely in the rapid transfusion of PRBCs.) Normal saline, Plasmalyte, and D5W do not contain calcium. Another common recommendation is to avoid the use of potassium containing crystalloids (LR or Plasmalyte) in patients with hyperkalemia. This recommendation does not take into account the volume of NS administered. If a large volume of NS is administered (>20 cc/kg), a patient is at risk of developing a hyperchloremic metabolic acidosis which can lead to hyperkalemia (despite the absence of potassium in NS!). With this is mind, large volume fluid resuscitation with isotonic, balanced crystalloids (Lactated Ringer's or Plasmalyte) is recommended.
Refs: Miller RD. Miller's Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2015.
Levac B, Parlow JL, van Vlymen J, et al. Ringer's lactate is compatible with saline- adenine-glucose-mannitol preserved packed red blood cells for rapid transfusion. Can J Anaesth. 2010; 57(12):1071– 1077.
O'Malley CM, Frumento RJ, Hardy MA, et al. A randomized, double-blind comparison of lactated Ringer's solution ...