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

More Terms• Diffusion

– 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

. Transmitting neuromuscular 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 ComponentRenal 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.