42 100 60 Total 3.5 8 5 Intravascular 13.5 32 19 Interstitial Extracellular 25 60 36 Intracellular Volume (L) Total Body Water (%) Body weight (%) Compartment Body Fluid compartments (based on average 70 kg male)
Normal Water Balance Normal adult daily water intake 2500ml Normal water loss 2500ml Urine 1500ml Resp tract eva 400ml Skin evaporation 400ml Sweat 100ml Feces 100ml
Total Blood Volume(TBV) = RBC volume + plasma volume 2L + 3L = 5L 7% of body weight ETBV = 4.9L
Hyperosmolarity and Hypernatremia - total body solute increases relative to TBW - Na > 145 meq/L - Loss of water in excess of sodium (hypotonic fluid loss) - Retention of large amounts of sodium - Compute for the water deficit
Ex. A 70kg man is found to have a plasma sodium of 160meq/L What is his water deficit? ( Normal TBW ) ( 140 ) = ( present TBW ) ( plasma Na ) (70) (0.6) ( 140 ) = ( present TBW ) ( 160) Present TBW = 36.7L Water deficit = NormalTBW – Present TBW 42L – 36.7L = 5.3L
Hypertonic solutions are given in cases of hypovolemic shock 3% NSS 5% NSS
Hypo-osmolarity and Hyponatremia - water retention - increase in TBW - loss of sodium in excess of water
Ex. An 80kg woman is lethargic and is found to have a plasma sodium of 118meq/L. How much NaCl must be given to raise her plasma sodium to 130 meq/L. Sodium Deficit = ( TBW ) ( 130 – 118 ) = ( 80 ) ( 0.5 ) ( 12 ) = 480 meq Normal isotonic saline = 154 meq/L = 3.12 L of normal saline
- aqueous solutions of low molecular wt., w/ or w/out glucose.
- Ratio is 3:1
- Maintains intravascular volume
Excessive amounts of fluid will manifest as peripheral edema
before it ges into the lungs.
Types of solutions: maintenance solutions – primarily due to water loss -replaced by hypotonic solutions replacement solutions – losses that involve water and electrolytes - replaced with isotonic electrolye solutions.
Colloids -contains high molecular wt. substances such as proteins or large glucose polymers -5% dextran, starch solutions. -normal ratio is 1:1 when used as a replacement in cases of blood loss -maintains intravascular volume by increasing the oncotic pressure -should be given slowly and in small amounts to prevent pulmonary edema
Estimating Maintenance Fluid Reqiurements Weight Rate For the first 10 kg 4 ml/ kg / hr For the next 10-20 kg add 2ml / kg /hr For each kg above 20 kg add 1 ml /kg /hr
Ex. MFR for a 25 kg child ? 40 + 20 + 5 =65 ml/hr
Fluid Deficits = ( MFR ) (length of fasting )
Surgical fluid losses fully soaked sponge (4*4) = 10 ml of blood soaked lap = 100 – 150ml
Redistributive and Evaporative Surgical Fluid Losses Degree of tissue trauma Additional fluid requirement Minimal (herniorapphy) 2 ml/kg/hr Moderate (cholecystectomy) 4 ml/kg/hr Severe (bowel resection) 6 ml/kg/hr
Average Blood Volumes Age Blood volumes Prematures 95ml/kg Full term 85ml/kg Infants 80ml/kg Adults Men 75ml/kg Women 65ml/kg
blood transfusion, if blood loss is > 20% of the TBV
Allowable Blood Loss Based on hemoglobin level = (EBV) (initial Hgb – targeted Hgb) initial Hgb Ex. Compute for the ABL of a 70 kg male patient with an initial Hgb of 15gms% And a targeted Hgb of 10 gms%. = (75) (70) (15 – 10) 15 = 1750 ml.
Based on hematocrit =Ex. What is the ABL of an 85 kg female patient with a pre-op Hct of 35% and a post Op Hct of 30%. Hct = ( RBCV lost ) ( 3 ) RBCV 35% = ( EBV ) (0.35) = 1934 RBCV 30% = ( 5525 ) (0.30) = - 1657 RBCV lost = 277 ABL = ( 227 ) ( 3 ) = 831 ml