FLUID MANAGEMENT

I. Fluid requirements

  1. When giving fluid therapy provide for baseline needs, static losses, and dynamic losses
  2. Baseline fluid requirements for adults: 2500cc/d
  1. 1500ml/m2/d (insensible = 400/m2)
  2. 100-50-20 rule (ml for first 3 kg; 20/kg after; also numerically equal to kCal req.)
  3. Na req: 75mEq/d
  4. K req: 60 mEq/d
  1. Static losses
  1. GI
  1. 8-10l secreted daily
  2. Generally high in Na, also contains lots K and either H+ or HCO3-
  1. Skin--sweat is always hypotonic
  2. Renal losses
  1. Dynamic losses-replace with Lactated Ringer's
  1. Obvious extracellular: vom, diarrhea, bile through t-tube, fistulae
  2. Urinary losses
  1. Diuretic phase of ATN
  2. Post-obstructive diuresis
  3. Obligate Na/H2O losses in some CRF patients
  4. Diuretic overuse
  5. Osmotic diuresis
  6. Addisonism
  1. Occult internal: third-spacing; including intradermal plasma sequestration in burns; ascites fluid

II. IVF options

  1. NS: isotonic (300mOsm/l); large Na load; if given in large amounts, can cause acidosis, so give instead Ringer's
  2. 1/2NS: hypotonic; MUST ADD KCl or Kac
  3. LACTATED RINGER'S: isotonic, contains Na, Ca, K, Cl, Lac; 120mEq/l Na, 4/l K
  4. D5W: isotonic, prevents gluconeogenesis
  1. Glu distributed in volume approx 0.3 l/kg--"glu space"
  1. Albumin
    1. A review of randomized trials concluded that albumin is associated with higher mortality than other fluid replacements when used in hypovolemia, burns, and hypoalbumeinemia (BMJ 317:223, 1998--JW)
    2. A subsequent meta-analysis did not show a significant increase in risk of death (Ann. Int. Med. 135:205, 2001--JW)
    3. 4% albumin IV vs. normal saline was ass'd with no sig. diff. in 28d all-cause mortality, ICu length of stay, or incidence of new organ failure in a randomized trial of 7,000 ICU patients who required IV fluids for volume replacement (NEJM 350:2247, 2004--JW)

III. Conditions with special fluid requirements

  1. Cerebral edema: avoid hyponatremia
  2. Burns
  1. <30% add to maint. %burn x 3cc/kg/d
  2. > 30% add to maint. % burn x 4cc/kg/d
  3. RL 1st 24h; D5-1/4NS afterward
  1. Neonates: give less than maintenance
  2. Post-heart surg: need fluid restriction
  3. Anuria: give to replace urine losses + insensible

IV. Fluid management in surgery

  1. "Restricted" intra- and post-operative IV fluid administration compared with "standard" (higher) IV fluids was ass'd with sig. lower incidence of postoperative complications (33% vs. 51%); primarily from lower incidence of cardiopulmonary and tissue-healing complications, in a randomized study of 141 pts (median age 66yo) undergoing elective colectomy under combined general + epidural anesthesia.  Restrictive protocol called for no preloading, no "3rd-space" replacement, maintenance during fasting periods of 500mL of D5W (minus any oral fluid intake during fast), and volume-to-volume replacement of blood loss with hydroxyethyl starch 6% (HAES) in NS; "standard" regimen called for 500mL HAES loading, "3rd space" loss replacement of NS 7mL/kg/h x 1h then 5mL/kg/h x 2h then 3mL/kg/h; maintenance during fasting periods of 500mL NS independent of oral intake; and replacement for blood loss with 1-1.5L of NS if loss < 500mL and for loss > 500mL, additional HAES.   (Ann. Surg 238:641, 2003--JW)