Acid-Base Balance: Diagnosis, Causes, and Treatment PDF

Acid-Base Balance Acid: H+ is an acid A compound is an acid if readily releases H+ Acids are byproducts of metabolism Base: OH- is a base A compound is a base if readily accepts H+ What is pH? Reflects hydrogen ion (H+ ) concentrations...

Acid-Base Balance Acid: H+ is an acid A compound is an acid if readily releases H+ Acids are byproducts of metabolism Base: OH- is a base A compound is a base if readily accepts H+ What is pH? Reflects hydrogen ion (H+ ) concentrations Normal Blood pH is 7.35-7.45 Anything below 6.8 or above 7.8 is incompatible with life Buffering systems in place to maintain that balance Acid-base balance is maintained through a variety of buffer systems and compensatory mechanisms. Three systems work to maintain the acid-base balance: 1. Buffers 2. Respiratory system 3. Renal system Buffers are the chemicals that combine with an acid or base to change pH. Act immediately to protect tissues and cells Main chemical buffer systems are: Bicarbonate-carbonic acid system Phosphate system Protein system Bicarbonate-carbonic acid system Bicarbonate-carbonic acid system: Most significant in the extracellular fluid Carbonic acid (H2CO3) and bicarbonate (HCO3-) are primary agents Carbonic Anhydrase Causes carbonic acid to separate into hydrogen and bicarbonate In the lungs, allows carbon dioxide excretion In the kidneys, allow for hydrogen excretion Bicarbonate In the lungs the reaction is reversed so the carbon dioxide can be expired along with water This reduces the amount of carbonic acid Phosphate system: Acts a lot like the bicarbonate-carbonic acid system Phosphates are high in the intracellular fluid Phosphates can act as weak acids or weak bases This buffering occurs primarily in the kidneys where hydrogen ions are accepted or donated Protein system: The most abundant buffering system Proteins can act as an acid or a base Proteins exist in intracellular and extracellular fluid but are most abundant inside the cell Hydrogen and carbon dioxide diffuse into the cell and bind to protein Albumin and plasma are the primary buffers in the intravascular (in the vessel) space Potassium and H+ Potassium: Move interchangeably in and out of cell with H+ to balance pH When H+ moves in the cell, K+ moves out When H+ moves out of the cell, K+ moves in Potassium imbalances can lead to pH imbalances How Does the Body Compensate? Lungs -actsfirst Kidneys make take a weep Carbon dioxide functions as an acid Alters the excretion of H+ or retention/ Increased breathing, decreases acidity creation of bicarbonate Decreased breathing, increases acidity More effective (permanently removes H+) Uses central chemoreceptors Responds a bit slower, but longer lasting Responds fast but short-lived Respiratory imbalance compensation Metabolic imbalance compensation Compensation If pH becomes more acidic due to lung disease (ex. COPD) then the lungs obviously cannot compensate so the kidneys must compensate. If the problem exists outside the lungs then the lungs can do the compensation that is needed. This is one reason why it is so important for nurses to know the patient’s health history. Acid-Base Balance FOUR IMBALANCES RESPIRATORY ACIDOSIS RESPIRATORY ALKALOSIS METABOLIC ACIDOSIS METABOLIC ALKALOSIS Respiratory acidosis Respiratory acidosis – results from carbon dioxide retention and increasing carbonic acid pH level decreases below 7.35 Carbon dioxide levels rise and the pH levels fall below the normal Carbon dioxide retention usually occurs from hypoventilation (not breathing fast enough) The clinical manifestations of tachypnea (fast breathing) and/or hyperpnea (deep breathing) are a “response” to acidosis. The body tries to get rid of excess CO2, in the presence of lung disease this difficult. Respiratory Acidosis Causes PULMONARY Impaired Gas Exchange Respiratory disease (COPD, asthma attack, airway obstruction, atelectasis, sleep apnea, pulmonary edema) Impaired Neuromuscular Function Resp. muscle weakness (hypokalemia, obesity, neurological dysfunction) Resp. failure ~ client doesn't control acid base oroz control Chest injury/surgery NONPULMONARY Dysfunction of Brainstem Drug overdose Central nervous system issue: depressed CNS or central sleep apnea Increased CO2 Production Sepsis Fever ** Exercise Burns* Respiratory Acidosis Diagnosis Health history, physical assessment helps look for infection/bacteria by at WBC's Chest x-ray ~ looking ABGs, blood chemistry, complete blood count: pH < 7.35 PCO2 or PaCO2 >45 HCO3 (depends on compensation) Hyperkalemia ~ can have affect on ↓ Hypercalcemia kt is high, Ke moves out while M+ lacid out of moves in , Ca moves bones into the blood to help the body buffer the acid. Respiratory Acidosis Changes in Function to Compensate ~> Kidneys reabsorp bicarb and excrete acids into vrine Signs and Symptoms: level of Increased rate and depth respirations (“blow off CO2”) ↓conse. Neuro: dizziness, syncope, anxiety, confusion followed by decreased LOC Neuromusc: paresthesia, muscle cramps, tetany witching CV: dysrhythmias, palpations, tachycardia, hypotension Pul: adventitious breath sounds, cyanosis (possibly) pathological Anticipated treatment: Oxygen therapy Mechanical ventilation Coughing, deep breathing Bronchodilators linhalers Treating the cause (antibiotics for the pneumonia) Respiratory alkalosis ~ too much CO2 Respiratory alkalosis – results from excess exhalation of carbon dioxide that leads to carbonic acid deficits and pH increases above 7 45. Respiratory alkalosis generally occurs from conditions that cause hyperventilation Respiratory Alkalosis Causes PULMONARY ~ got rid of too much CO2 ? NONPULMONARY Hyperventilation due to hypoxia (pulmonary edema,PE, Acute pain asthma) Anxiety/distress/sobbing Inappropriate ventilator settings Liver failure ~ set too fast Stimulation of brainstem giving too much 02 Central nervous system disorders Sepsis lasprin) - > Salicylate overdose Fever/Infection Respiratory Alkalosis Diagnosis History, Physical Assessment Chest X-ray Labs (ABG, chemistry, CBC): pH > 7.45 PaCO2 7.45 PaCO2 (depends on compensation) HCO3 >26 Hypokalemia Hypocalcemia Clinical manifestations Neuro: confusion, dizziness, agitation, seizures GI: vomiting, diarrhea Systemic: weakness Anticipated treatment: Adequate hydration Correcting electrolyte imbalances such as hypokalemia and hypochloremia Administration of various medications The ABC’s of ABGs ABGs- arterial blood gases Principal diagnostic tool for evaluating acid-base balance Are only one part of your assessment data, must look at the entire clinical picture Three components speak to acid-base balance: pH: 7.35 - 7.45 PaCO2: 35 -45 Bicarbonate: 22 - 26 ABGs Remember: pH – measure of H+ ion concentration in the blood PaCO2 – measure of the carbon dioxide in the blood Indicates the effectiveness of the patient’s breathing Moves the opposite direction of pH levels Bicarbonate – represents the metabolic component of the body’s acid-base balance Moves the same direction of pH levels Interpreting ABGs Learn to follow a consistent sequence: Step 1: check the pH Is it acidotic (below 7.35) Is it alkalotic (above 7.45) Step 2: determine the PaCO2 This gives you information about the respiratory component of acid- base balance Determine if PaCO2 is low (less than 35) or high (greater than 45) Next determine if the abnormal results corresponds to a change in pH if pH is high, you would expect the PaCO2 to be low, indicating that the problem is respiratory alkalosis if pH is low, you would expect the PaCO2 to be high, indicating the problem is respiratory acidosis Step 3: examine the bicarbonate level (HCO3) This provides information about the metabolic aspect of the acid- base balance Determine if HCO3 is low ( less than 22) or high ( greater than 26) Determine how this corresponds to the pH If pH is high you would expect the HCO3 level to be high indicating metabolic alkalosis If pH is low then would expect the HCO3 level to be low indicating metabolic acidosis Step 4: look for compensation Sometimes will see a change in both PaCO2 and the HCO3 levels One indicates the primary source of the pH change and the other the body’s effort to compensate for the disturbance If compensation if complete the pH will fall within the normal range If compensation is partial, then the pH will remain outside the normal range Interpreting abgs Compensation: Involves opposites If results indicate metabolic acidosis, compensation will come in the form of respiratory alkalosis pH – 7.29 PaCO2 – 17 HCO3 – 19 The pH is low: acidosis PaCO2 is low: alkalosis HCO3 is low: normally leads to acidosis So…. Bicarbonate level most closely corresponds to pH, making the primary cause metabolic. Decrease in PaCO2 reflects partial respiratory compensation Step 5: look at PaO2 and O2 saturation PaO2: (80 -100) O2 saturation: 95-100% ROME method: Look at pH. Draw arrows high or low Next look at CO2. Draw arrow for high, low, or normal If CO2 is normal then go to HCO3 and draw and arrow if high, low, or normal Arrows in opposite direction = respiratory Respiratory – opposite Arrows in same direction = metabolic Metabolic – equal ROME