PRINCIPLES OF FLUIDS AND ELECTROLYTES

Fluid Compartments Example: 70-kg male Total Body Water: 42,000 mol(60% of BW) Intracellular: 28,000 mL(40% of BW) Extracellular: 14,000 mL(20% of BW) Plasma: 3500 mL(5% of BW) Interstitial: 10,500 mL(15% of BW)

DO2 = Cardiac Index x CaO2 x 10 = SV x HR x {(Hb x SaO2 x 1.34) + (0.003 x PaO2) }

Clinical Signs of Adequacy of Perfusion Urine output Mental status Capillary refill Skin color Temperature Pulse rate Acid-base status Lactate Levels Oxygen consumption Mixed Venous Oxygen Saturation

Perioperative Fluid Therapy ● Normal Daily fluid Requirements : 30-35 ml/kg/day for adult + 1 mmol/kg/day Na+ + 1 mmol/kg/day K+

I Normal perioperative maintenance: - 1st 10 kg BW  4ml/kg/hr - 2nd 10 kg BW  2ml/kg/hr - each remaining kg  1ml/kg/hr Types : D5 ¼ NS , DS ½ NS , LR eg. 70kg man maintenance  40+20+50 =110ml/hr II Pre-existing Deficits : (a) Fasting : Maintenance /hr x Fasting hrs. 50% in 1st hr , 25% in 2nd hr , 25% in 3rd hr (b) Preoperative deficits : vomiting- diarrheoa- ascites - bleeding

III Replacement Requirement : (1) Bood loss - 10-20% Blood volume - HB 7-10gm/dL - Hct falls by>30% Allowable Blood loss  volume of lost RBCs x 3 Each one unit of RBCs increase HB 1gm/dl & Hct 2-3% (2) Evaporation and 3rd space loses : -Minimal (eg. herniorhapy) 2ml/kg/hr - Moderate (eg. cholecystomy) 2-4 ml/kg/hr - Severe (eg. bowel resection) 4-8 ml/kg/hr by lactate Ringer solution (3) Abnormal fluid loss : - GIT:nasogastic suction, sequestered fluid in gut - urine - Insensible loss (from skin or lung) = 0.5ml/kg/hr increase 10 C increases insensible loss, about 12 %

Intravenous fluids Crystalloid solutions: Low molecular weight Intravascular half life 20-30 minutes Hypotonic solutions: D5 W For replacement of pure water deficits As maintenance fluids for patient on Na restriction Isotonic solutions (Replacement-type solutions) For replacement of losses that involve water or electrolytes (eg intraoperative losses) eg LR , NS Hypertonic solutions: Given via a central venous line 3% saline, 7.5% saline used in hyponatremia , in hypovolemic shock

Isotonic Crystalloids : ●Normal Saline (0.9%) (Na 154 meq/L, Cl 154 meq/L) ●Lactate Ringer’s (Hartman’s solution) (Na 130 meq/L, Cl 109 meq/L, K 4 meq/L, Lactate 28 meq/L, Ca 3 meq/L) ● Ringer’s solutions Na 147.5 meq /L, Cl 156 meq/L, k 4 meq/L, Ca 2 meq/L Hypotonic solutions D5W (containing glucose 50gm/L) Hypertonic solutions D5 ¼ Ns ,(Na 77meq/L, Cl 77 meq/L, glucose 50gm/L) D5 ½ NS , (Na 154 meq/L, Cl 154 meq/L, glucose 50 gm/L) NHCo3 8.4%, (Na 1000 meq/L, HCO3 1000 meq/L)

Colloid Solutions . They are solutions containing high molecular weight substances, intravascular half-life 4-6 hrs . Used in : - hemorrhagic shock (severe intravascular deficits) - severe hypoalbumenimia (or large protein loss eg. burns) . Types: 1- blood derived human albumin 5,25%, plasma protein fraction 5% 2- synthetic colloid  a) starch eg. Dextran 70 or 40 b) Gelatines eg. Gelofusine, polygeline 3- Hestastarch eg. 6 % Hydroxyethyl starch