Acid Base Balance Fluid Balance

Acid Base Balance and Fluid Balance Dr. Kathleen Ethridge Northeast Texas Community College

Homeostasis • A delicate balance of fluids, electrolytes, and acids and bases is required to maintain good health. • This balance is called Homeostasis.

Body Fluids • Intracellular fluid (ICF) – found within the cells of the body – constitutes 2/3 of total body fluid in adults – major cation is potassium

• Extracellular fluid (ECF) – found outside the cells – accounts of 1/3 of total body fluid – major cation is sodium

Terms • Osmosis – movement of water across cell membranes from less concentrated to more concentrated

• Solutes – substances dissolved in a liquid

• Osmolality – the concentration within a fluid

• Diffusion

More Terms

– movement of molecules in liquids from an area of higher concentration to lower concentration

• Filtration – fluid and solutes move together across a membrane from area of higher pressure to one of lower pressure

• Active Transport – substance moves across cell membranes from less concentrated solution to more concentrated - requires a carrier

Routes of Fluid Loss • Urine • Insensible fluid loss • Feces

Electrolytes • • • •

Sodium Potassium Chloride Phosphate

• Magnesium • Calcium • Bicarbonate

Electrolytes are important for: . Maintaining fluid balance . Contributing to acid-base regulation . Facilitating enzyme reactions

Acid-Base Balance

• Acid-Base balance is: – the regulation of HYDROGEN ions.

pH • The acidity or alkalinity of a solution is measured as pH. • The more acidic a solution, the lower the pH. • The more alkaline a solution , the higher the pH. • Water has a pH of 7 and is neutral. • The pH of arterial blood is normally between 7.35 and 7.45

Hydrogen ions • The more Hydrogen ions, the more acidic the solution and the LOWER the pH • The lower Hydrogen concentration, the more alkaline the solution and the HIGHER the pH

pH • Know what is normal.

Buffer Systems • Regulate pH by binding or releasing Hydrogen • Most important buffer system: – Bicarbonate-Carbonic Acid Buffer System • (Blood Buffer systems act instantaneously and thus constitute the body’s first line of defense against acid-base imbalance)

Acid Base Balance

Respiratory Component Renal Component

Respiratory Regulation • Lungs – help regulated acid-base balance by eliminating or retaining carbon dioxide – pH may be regulated by altering the rate and depth of respirations – changes in pH are rapid, » occurring within minutes

– normal CO2 level • 35 to 45 mm Hg

Renal Regulation • Kidneys – the long-term regulator of acid-base balance – slower to respond • may take hours or days to correct pH

– kidneys maintain balance by excreting or conserving bicarbonate and hydrogen ions – normal bicarbonate level • 22 to 26 mEq/L.

Factors Affecting Balance • Age – especially infants and the elderly

• Gender and Body Size – amount of fat

• Environmental Temperature • Lifestyle – stress

Acid-Base Imbalances • • • •

Respiratory Acidosis Respiratory Alkalosis Metabolic Acidosis Metabolic Alkalosis

See Chart

Respiratory Acidosis • Mechanism – Hypoventilation or Excess CO2 Production

• Etiology – – – – – – –

COPD Neuromuscular Disease Respiratory Center Depression Late ARDS Inadequate mechanical ventilation Sepsis or Burns Excess carbohydrate intake

Respiratory Acidosis (cont) • Symptoms – – – –

Dyspnea, Disorientation or coma Dysrhythmias pH < 7.35, PaCO2 > 45mm Hg Hyperkalemia or Hypoxemia

• Treatment – – – –

Treat underlying cause Support ventilation Correct electrolyte imbalance IV Sodium Bicarb

Respiratory Alkalosis • Risk Factors and etiology – Hyperventilation due to » » » » » » »

extreme anxiety, stress, or pain elevated body temperature overventilation with ventilator hypoxia salicylate overdose hypoxemia (emphysema or pneumonia) CNS trauma or tumor

Respiratory Alkalosis (cont) • Symptoms – – – – – – –

Tachypnea or Hyperpnea Complaints of SOB, chest pain Light-headedness, syncope, coma, seizures Numbness and tingling of extremities Difficult concentrating, tremors, blurred vision Weakness, paresthesias, tetany Lab findings – pH above 7.45 – CO2 less than 35

Respiratory Alkalosis (cont) • Treatment • • • • • •

Monitor VS and ABGs Treat underlying disease Assist client to breathe more slowly Help client breathe in a paper bag or apply rebreather mask Sedation

Metabolic Acidosis • Risk Factors/Etiology – Conditions that increase acids in the blood • • • •

Renal Failure DKA Starvation Lactic acidosis

– Prolonged diarrhea – Toxins (antifreeze or aspirin) – Carbonic anhydrase inhibitors - Diamox

Metabolic Acidosis (cont) • Symptoms – Kussmaul’s respiration – Lethargy, confusion, headache, weakness – Nausea and Vomiting

– Lab: • pH below 7.35 • Bicarb less than 22

• Treatment – treat underlying cause – monitor ABG, I&O, VS, LOC

Sodium Bicarb?

Metabolic Alkalosis • Risk Factors/Etiology – Acid loss due to • vomiting • gastric suction

– Loss of potassium due to • steroids • diuresis

– Antacids (overuse of)

Metabolic Alkalosis (cont)

• Symptoms – – – – –

Hypoventilation (compensatory) Dysrhythmias, dizziness Paresthesia, numbness, tingling of extremities Hypertonic muscles, tetany Lab: pH above 7.45, Bicarb above 26 – –

CO2 normal or increased w/comp Hypokalmia, Hypocalcemia

• Treatment – I&O, VS, LOC – give potassium – treat underlying cause

Pneumonic • • • •

Respiratory Opposite Metabolic Equal

Interpreting ABGs

• 1. Look at the pH • is the primary problem acidosis (low) or alkalosis (high)

• 2. Check the CO2 (respiratory indicator) • is it less than 35 (alkalosis) or more than 45 (acidosis)

• 3. Check the HCO3 (metabolic indicator) • is it less than 22 (acidosis) or more than 26 (alkalosis)

• 4. Which is primary disorder (Resp. or Metabolic)? • If the pH is low (acidosis), then look to see if CO2 or HCO3 is acidosis (which ever is acidosis will be primary). • If the pH is high (alkalosis), then look to see if CO2 or HCO3 is alkalosis (which ever is alkalosis is the primary). • The one that matches the pH (acidosis or alkalosis), is the primary disorder.

Compensation

• The Respiratory system and Renal systems compensate for each other – attempt to return the pH to normal • ABG’s show that compensation is present when – the pH returns to normal or near normal • If the nonprimary system is in the normal range (CO2 35 to 45) (HCO3 22-26), then that system is not compensating for the primary. • For example: – In respiratory acidosis (pH<7.35, CO2>45), if the HCO3 is >26, then the kidneys are compensating by retaining bicarbonate. – If HCO3 is normal, then not compensating.