Principals of fluids and electrolytes management Ram Elazary, MD General Surgery Department Hadassah Hebrew University Medical Center Campus Ein-Kerem, Jerusalem

Total Body Water body weight% Total body water% Total 60 100 Intracellular 40 67 Extracellular 20 33 Intravascuar 5 8 Interstitial 15 25

Composition of Fluids plasma interstitial intracellular Cations Na 140 146 12 K 4 4 150 Ca 5 3 10 Mg 2 1 7 Anions Cl 103 104 3 HCO 24 27 10 SO4 1 1 - HPO4 2 2 116 Protein 16 5 40

Control of Volume Kidneys maintain constant volume and composition of body fluids Filtration and reabsorption of Na Regulation of water excretion in response to ADH Water is freely diffusible Movement of certain ions and proteins between compartments restricted

Control of Volume Effective circulating volume Third space loss Portion of ECF that perfuses organs Usually equates to Intravascular volume Third space loss Abnormal shift of fluid for Intravascular to tissues eg bowel obst, i/o, pancreatitis

Normal Water Exchange Mean daily (ml) Minimal daily (ml) Sensible Urine 800-1500 600 Intestinal up to liters Sweat up to liters 500 Insensible Lungs/Skin 600-900 600-900 ( 10%/1 o rise in Temp)

Normal source of water ~2000ml - 1300 free water intake 700 bound to food additional water from catabolism

Water and Eletrolytes Exchange Surgical patients prone to disruption: NPO anaesthesia Trauma (surgery) sepsis

Fluid and Electrolytes Therapy Surgical patients need: Maintenance volume requirements On going losses Volume excess/deficits Maintenance electrolyte requirements Electrolyte excess/deficits

1. Volume Deficit vital signs changes Blood pressure Heart rate CVP Peripheral temperature and capillary filling time urine output low

1. Volume Deficit Decreased skin turgor Sunken eyes Oliguria Orthostatic hypotension High BUN/Creatine ratio Plasma Na may be normal

Fluids resusitation Adults: 1000 ml Pediatrics: 20 ml/kg Fluids of crystaloids (NS or RL) Repeated dose

2. Maintenance Requirements This includes: insensible loss urinary stool losses Body weight Fluid required 0-10Kg 100ml/kg/d next 10-20Kg 50 ml/kg/d subsequent Kg 20ml/kg/d 15ml/Kg/d for elderly

70 Kg Man Needs 1st 10kg x 100mls = 1000mls 2nd 10kg x 50mls = 500mls Next 50kg x 20mls= 1000mls TOTAL 2500 mls /d

Maintenance Electrolyte Requirements Na 1-2mEq/Kg/d K 0.5 - 1 mEq/Kg/d Usually no K given until urine output is adequate Always give K with care, in an infusion slowly - never bolus (max 0.2% KCL through peripheral IV)

Na 1gr = 17 mEq K 1gr = 13.6 mEq 70 Kg H2O 2500ml Na 70*2 =140 mEq = ~ 9gr K 70*1 =70 mEq = ~ 5gr 2500 0.45NS + 0.2%KCl 100ml/h

fluids composition

3. On Going Losses NGT drains fistulae third space losses

4. Volume Excess Over hydration Mobilization of third space losses Signs weight gain pulmonary edema peripheral edema S3 gallop

Fluid and Electrolyte Therapy Goals normal hemodynamic parameters normal electrolyte concentration Method replace deficits normal maintenance requirements ongoing losses

Fluid and Electrolyte Therapy Normal maintenance requirements use BW formula On going losses measure all losses in I/O chart estimate third space losses Deficits estimate using vital signs estimate using U/O

Fluid and Electrolyte Therapy The best estimate of the volume required is the patients response After therapy started observe vital signs Urine output (0.5mls/Kg/hr) Central venous pressure

Time Frame for Replacement Usually correct over 24 hours For ill patients calculate over shorter period and reassess e.g. 1, 2 hours or 3 hours for e op cases Deficits - correct half the amount over the period and reassess

Postoperative Fluid Therapy Check IV regimen ordered in op form Assess for deficits by checking I/O chart and vital signs Maintenance requirements calculated Usually K not started Monitor carefully vital signs and urine output

Postoperative Fluid Therapy Urine specific gravity may be used (1.010 - 1.012) CVP useful in difficult situations (5-15 cm H20) Body weight measured in special situation e.g. burns

Concentration Changes changes in plasma Na are indicative of abnormal TBW losses in surgery are usually isotonic hypoosmolar condition usually caused by replacement with free water