acid base balance fluid balance
TRANSCRIPT
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.