FLUID AND ELECTOLYTES Begashaw M (MD)

DEFINITIONS Moles or millimoles: number of particles present per unit volume Equivalents or milliequivalents: number of electric charges per unit volume Osmoles or milliosmoles: number of osmotically active particles or ions per unit volume

NORMAL DISTRIBUTION OF BODY FLUIDS Intra- cellular Extra- cellular 2/3 1/3 Inter- stitial Intra-vascular 2/3 1/3 Total body water

NORMAL DISTRIBUTION OF BODY FLUIDS Total body water; constitutes 50 – 85 % of TBW -55% - 60% weight for a 70 Kg adult -Females (45 –60%) -neonates is 80%-85% 1. Intracellular fluid-2/3 2. Extra cellular fluid-1/3 Extra cellular fluid -Intravascular (plasma) 1/3 -Interstitial-2/3 of extra cellular fluid

Distribution of electrolytes

Maintenance Fluid balance Daily maintenance fluid requirement of 70kg man is L Fluid sources Exogenous-drunk fluid or ingested 2-3 liters/day Endogenous –from oxidation of food <500 ml/day Total body water content & requirement of children is larger than that of adults

Daily Intake and Output of Water (ml/day)

Composition of Intravenous Fluids

DISTURBANCES OF FLUID AND ELECTROLYTES CLASSIFICATION - Disturbance in fluid volume - Disturbance in composition - Disturbance in acid base balance

DISTURBANCE IN FLUID VOLUME Volume deficit most common fluid volume disorder in the surgical patient the lost fluid is - water and electrolytes

Causes Losses GI fluids- vomiting, gastric tube, diarrhea and enterocutaneous fistulas Sequestration burn peritonitis, intestinal obstruction

Clinical feature Depends on severity Moderate (5-10%): sleepiness, orthostatic hypotension Severe (more than 15%)-hypotension, stupor or coma, sunken eye balls, dry oral mucosa and tongue, poor skin turgor and decrease in body temperature

Treatment -Replacement Blood loss: RL, NS, Blood Extra cellular fluid: RL, NS -Rate fast until the vital signs are corrected and adequate urine output 1-2 liter over 30 minutes to one hour Monitoring general condition & vital signs urine out put - hourly chest –overload- esp in children & elderly

Volume Excess is generally iatrogenic secondary to ARF,cirrhosis, or CHF C/F edema, basilar rales, distended neck veins, murmurs Children, elderly, pts with cardiac or renal problems are at increased risk Treatment Stop IV fluids (Fluid restriction) Diuretics: e.g. Furosemide

Serum Electrolytes Cations Concentration, mEq/L Sodium Potassium Calcium Magnesium Anions Chloride CO Phosphate

DISTURBANCE IN ELECTROLYTES Sodium (Na+) most abundant cation of ECF After trauma & surgery, period of shut down of sodium excretion for up to 48 hrs Daily requirement 1 millimol/kg Excretion - kidneys under the control of aldosterone

Hyponatremia Na < sodium and water depletion -small intestinal obstruction -high intestinal fistula 2. Water intoxication: over-prescribing excess 5% D/W Clinical feature -either fluid deficit or overload Lab: Serum Na, hematocrit drops Treatment Rl/NS -volume depletion Fluid restriction, sodium sparing diuretics I-fluid excess

Hypernatremia Na+>145 Causes Excessive water loss- burns,sweating Excess amount of 0.9% saline solution Clinical feature fluid excess or fluid deficit Treatment 5% D/W can be infused slowly

Potassium (K+) most abundant intracellular cation 98% -intracellular ¾ -in skeletal muscle Daily requirement is 1mmol/kg

Hypokalemia < 3.5 Causes _ vomiting in GOO or diarrhea _ Intracellular shift-in alkalosis _ k+ loss is primarily renal in origin _ Diuretics (esp. thiazides)

Clinical features Most - asymptomatic listlessness, slurred speech, muscular hypotonia, and depressed reflexes Abdominal distention-paralytic ileus

Treatment Oral -milk, meat extracts, fruit juices, honey, KCl tablets IV- 40 mmol KCl added to 1 liter of fluid run over 6 -8 hours. Never directly IV Correct the underlying cause urine out put must be adequate

Hyperkalemia > 5 Can be due to - ↓ed renal K+ excretion (ARF or CRF) - Mineralocorticoid deficiency or unresponsiveness - K+ release from the ICF severe injury surgery, acidosis catabolic state

Clinical features Nausea, vomiting, intermittent intestinal colic and diarrhea ECG - high peaked T waves, widened QRS complex and depressed ST segment heart block and cardiac arrest

Treatment _ bicarbonate _ glucose with insulin-10 to 20 units of regular insulin and 25 to 50 g of glucose _10 ml of 10% calcium gluconate to suppress the myocardial effect _ Kayexalate _ Dialysis _ Avoid exogenous potassium

ACID – BASE BALABCE Normal PH The control : Blood buffer:-bicarbonate and carbonic acid, phosphates,serum proteins and meth- hemoglobin lung:- excretes acid(CO2 ) Kidney :- excrete both acid and base

Primary Acid-Base Disturbances

Analysis of simple acid-base disorders

Metabolic Alkalosis Causes Loss of acid from the stomach by repeated vomiting or aspiration Excessive ingestion of absorbable alkali Hypokalemic alkalosis - pyloric stenosis

Clinical Features Cheyne-stokes respiration with periods of apnea Tetany Treatment Repletion of volume –normal saline potassium (check urine output )

Respiratory Alkalosis Causes  excessive pulmonary ventilation  hyperventilation -severe pain -hyper pyrexia -high altitude

Clinical Features potassium depletion ventricular arrhythmia and fibrillation Treatment breathing into a plastic bag insufflation of carbon dioxide

Metabolic Acidosis Primary ↓ in serum [HCO3-] & systemic pH Causes _Increase in fixed acids anaerobic metabolism (shock, infection) renal failure ketone bodies in diabetes or starvation _Loss of bases Chronic diarrhea high intestinal fistula

Clinical Features rapid, deep, noisy breathing urine becomes strongly acidic Treatment Reperfusion Sodium bicarbonate

Respiratory Acidosis alveolar ventilation is ↓ed, with ↑ing Pco2 Occur in upper or lower airway obstruction, CNS depression & neuromuscular defects hypoxia -restless, tachycardia Correct the underlying pathologic condition improve alveolar ventilation- Intubation and mechanical ventilation 35

SUMMARY

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