FLUID AND ELECTROLYT

ES

DR. HAYDAR MUNEERB.D.S. , F.I.B.M.S.

TOTAL BODY WATER (TBW)

Water constitutes approximately 50 to 60% of total body weight

muscle and solid organs have higher water content than fat and bone

. The highest percentage of TBW is found in newborns, with approximately 80% of their total body weight comprised of water

FLUID COMPARTMENTS

1. The extracellular: Compromise about 1/3 of total body water(20% of body weight) and is divided between plasma and interstitial fluid2. The intracellular:Compromise about 2/3 of total body water (40% of body weight) with the largest proportion in the skeletal muscle mass

COMPOSITION OF FLUID COMPARTMENTS

The extracellular fluid compartment is balanced between the principal cation—sodium and the principal anions—chloride and bicarbonate.

The intracellular fluid compartment is comprised primarily of the cations, potassium and magnesium, and of the anions, phosphate and proteins.

maintained by ATP-driven sodium-potassium pumps located within the cell membranes.

OSMOTIC PRESSURE

The movement of water across a cell membrane depends primarily upon osmosis. To achieve osmotic equilibrium, water moves across a semipermeable membrane to equalize the concentration on both sides

OSMOTIC PRESSURE

any change in osmotic pressure in one compartment is accompanied by a redistribution of water until the effective osmotic pressure between compartments is equal.

NORMAL EXCHANGE OF FLUID AND ELECTROLYTES

Fluid input1. Exogenous 2 to 3 LIngested water and fluids / Ingested food (5%) 2. Endogenous 500 mlOxidation of food

NORMAL EXCHANGE OF FLUID AND ELECTROLYTES

Fluid output1. Lungs ( 400 ml/24hrs)2. Skin ( 600-1000 ml/24hrs)3. Faeces (60-150 ml /24hrs)4. Urine (1500/24hrs)

ETIOLOGY OF VOLUME DEFICIT IN SURGICAL PATIENTS1. Loss of gastrointestinal

fluids from nasogastric suction,

2. Vomiting, 3. Diarrhea, 4. Fistula. 5. Sequestration secondary to

soft-tissue injuries. 6. Burns.7. Prolonged surgery can also

lead to volume deficits

FLUID REPLACEMENT:

A typical daily maintenance fluid regimen would consist of a combination of 5% dextrose with either Hartmann’s or normal saline to a volume of 2 litres.

FLUID REPLACEMENT:

Young fit patients with normal renal and cardiac function. Atypical regimen might include: 1000 ml 0.9% saline over 2h; further 1000 ml infusion of 0.9% saline over 4h each until corrected.

Elderly patients and patients with renal or cardiac impairment . Atypical regimen include 1000ml 0.9% saline over 4h, 500 ml infusion of 0.9% saline over 3-4h with regular review of vital signs

ELECTROLYTES IMBALANCE:

1. Sodium: 137-147 mmol/LTotal body content 500 mmol (44% EC, 9% IC, 47% bone)Daily requirement:50-90 mM /day

Body System HyponatremiaCentral nervous system

Headache, confusion, seizures, coma, increased intracranial pressure

Musculoskeletal Weakness, fatigue, muscle crampsGastrointestinal Anorexia, nausea, vomiting, watery diarrheaCardiovascular Hypertension and bradycardia Tissue Lacrimation, salivationRenal OliguriaBody System HypernatremiaCentral nervous system

Restlessness, lethargy, irritability, tonic spasms, seizures, coma

Musculoskeletal WeaknessCardiovascular Tachycardia, hypotension, syncopeTissue Dry sticky mucous membranes, red swollen

tongue, decreased saliva and tearsRenal OliguriaMetabolic Fever

2. Potassium : 3.5mmol/L98% intracellular, 75% in skeletal muscles Daily requirement 50 mM/dayBody system Hyperkalemia

Gastrointestinal Nausea/vomiting, colic, diarrhea

Neuromuscular Weakness, paralysis, respiratory failure

Cardiovascular Renal Arrhythmia, arrestBody system Hypokalemia

Gastrointestinal Ileus, constipationNeuromuscular Decreased reflexes,

fatigue, weakness, paralysis

Cardiovascular Arrest

3. Calcium: 2.2-2.5 mmol/LImportant for blood coagulation and neuromuscular activityDaily requirement 5 mM/day

Body system HypercalcemiaGastrointestinal Anorexia, nausea/vomiting,

abdominal painNeuromuscular Weakness, confusion,

coma, bone painCardiovascular Renal Hypertension,

arrhythmia, polyuria Polydipsia

Body system HypocalcemiaGastrointestinal  Neuromuscular Hyperactive reflexes,

paresthesias, seizuresCardiovascular Renal Heart failure

The level of calcium is affected by:

1. Vitamin D 2. Parathyroid hormone 3. Calcitonin  4.Renal and bowel function

ACID – BASE IMBALANCE:

The pH of body fluids is maintained within a narrow range ( normal PH 7.36-7.44) Important buffers include:

1. Intracellular proteins and phosphates

2. Extracellular bicarbonate-carbonic acid

system

COMPENSATION FOR ACID-BASE DERANGEMENTS

1. Respiratory (for metabolic derangements):Changes in ventilation in response to metabolic abnormalities are mediated by hydrogen-sensitive chemoreceptors found in the carotid body and brain stem. Acidosis stimulates the chemoreceptors to increase ventilation while alkalosis decreases the activity of the chemoreceptors and thus decreases ventilation

COMPENSATION FOR ACID-BASE DERANGEMENTS 2. Metabolic (for respiratory derangements):The kidneys provide compensation for respiratory abnormalities by either increasing or decreasing bicarbonate reabsorption for respiratory acidosis or alkalosis, respectivelyCompensation does not begin for at least 6 hours and continues for several days.

ALKALOSIS: MORE THAN 7.44

1. Metabolic alkalosis:Excessive ingestion of alkalisLoss of acid (vomiting)Cortisone excess (Cushing disease)

Compensation by: Retention of CO2Excretion of bicarbonate by the kidney Treatment:Remove the cause Encourage high urine outputCorrect hypokalemia

2. Respiratory alkalosis: Due to excessive pulmonary

ventilationAnesthesiaHigh altitudeHyper pyrexiaHysteriaLesion of hypothalamus

Compensation: By increased excretion of bicarbonate (Slow)Treatment: Respiratory suppression

ACIDOSIS: LESS THAN 7.36

1. Metabolic acidosis: due to: Increased in fixed acids:

Formation of ketone bodies in diabetes or starvation

Retention of metabolites in renal failureAnaerobic metabolism (increase lactic

acid) as in cardiac arrest and shock Loss of base:

DiarrheaUlcerative colitisGastro colic fistula Intestinal aspiration

Compensation: by hyperventilation Treatment: Restoration of adequate tissue

perfusion, Bicarbonate solution

Respiratory acidosisImpaired alveolar ventilation Anesthesia and lung diseases Treatment:Correct the underlying causeBicarbonate solution