FLUID AND ELECTOLYTES Begashaw M (MD). DEFINITIONS Moles or millimoles: number of particles present per unit volume Equivalents or milliequivalents: number.

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 2.5-3 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 deficitmost common fluid volume disorder in the

surgical patientthe 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

hypotensionSevere (more than 15%)-hypotension,

stupor or coma, sunken eye balls, dry oral mucosa and tongue, poor skin turgor and decrease in body temperature

Treatment-ReplacementBlood loss: RL, NS, BloodExtra 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

Monitoringgeneral condition & vital signsurine out put - hourlychest –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 135 - 145

Potassium 3.5 - 4.5

Calcium 4.0 - 5.5

Magnesium 1.5 - 2.5

AnionsChloride 95 - 105

CO2 24 - 30

Phosphate 2.5 - 4.5

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/kgExcretion - kidneys under the control of

aldosterone

Hyponatremia Na < 1301.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

CausesExcessive water loss- burns,sweatingExcess amount of 0.9% saline solution

Clinical feature fluid excess or fluid deficit

Treatment5% D/W can be infused slowly

Potassium (K+)

most abundant intracellular cation98% -intracellular ¾ -in skeletal muscleDaily 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 causeurine 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-7.36-7.44

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

TreatmentRepletion of volume –normal salinepotassium (check urine output )

Respiratory Alkalosis

Causes excessive pulmonary ventilation hyperventilation -severe pain

-hyper pyrexia

-high altitude

Clinical Featurespotassium depletion ventricular arrhythmia and fibrillation

Treatmentbreathing into a plastic baginsufflation 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 diarrheahigh intestinal fistula

Clinical Featuresrapid, deep, noisy breathing urine becomes strongly acidic

TreatmentReperfusionSodium bicarbonate

Respiratory Acidosis

alveolar ventilation is ↓ed, with ↑ing Pco2Occur in upper or lower airway obstruction,

CNS depression & neuromuscular defectshypoxia -restless, tachycardiaCorrect the underlying pathologic condition improve alveolar ventilation- Intubation

and mechanical ventilation

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SUMMARY

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