Nursing Exam Review Lecture 1 Acid Base Balance

Lecture 1 Acid/Base Balance In order to solve acid-base disorders, it is important to know the normal values for pH, CO2 and HCO3 (bicarbonate), which are shown below • pH 7.35 to 7.45 • CO2 35 to 45 • HCO3 22 to 26 The first value to look at in an acid-base disorder is the pH • If pH is <7.35, the acid-base imbalance is acidotic • If pH is <7.45, the acid-base imbalance is alkalotic Now, to determine if the imbalance is metabolic or respiratory, determine whether HCO3 goes in the same or opposite direction with pH • Rule of the Bs: If pH and Bicarb move both in the same direction, then the acid-base imbalance is metabolic … Otherwise, it is respiratory Example #1 • pH 7.3 Acidotic • HCO3 20 Metabolic • This is an example of metabolic acidosis Example #2 • pH 7.58 Alkalotic • HCO3 32 Metabolic • This is an example of metabolic alkalosis Example #3 • pH 7.22 Acidosis • HCO3 35 Respiratory • This is an example of respiratory acidosis As the pH goes, so goes my patient, except for Potassium … That means • If pH is low, everything is low, except potassium • If pH is high, everything is high, except potassium If pH goes over 7.45, this is alkalosis • Therefore everything is up: tachycardia, tachypnea, HTN, seizures, irritability, spastic, diarrhea, borborygmi (increase bowel sounds), hyperreflexia (3+, 4+) • However, potassium is opposite. Therefore, hypokalemia • What is the nursing intervention? o Pt need suctioning because of seizures If pH goes below 7.35, this is acidosis • Therefore, everything is down: bradycardia, constipation, absent bowel sounds, flaccid, obtunded, lethargy, coma hyporeflexia (0, 1+), bradypnea, low BP • However, potassium is high (hyperkalemia) • What is the nursing intervention? o Pt needs to be ventilated with an Ambu bag—respiratory arrest So, remember that “MAC Kussmaul” is the only acid-base imbalance to cause Metabolic ACidosis with Kussmaul respirations Causes of Acid/Base imbalance First ask yourself, “Is it LUNG? … If yes, then it is respiratory • Then ask yourself, “Are they overventilating or underventilating? o If UNDERventilating, then pick acidosis—pH is under 7.35 o If OVERventilating, then it is alkalosis, pH is over 7.45 What type of acid-base derangement is present in the following condition? • In labor? o Respiratory alkalosis … Overventilating—pH increases … Alkalosis) • Drowning? o Respiratory acidosis … Underventilating—pH decreases … Acidosis • Pt is on PCA (patient-controlled anesthesia) pump? o Ventilation is down … Respiratory acidosis If it is not LUNG, then it is metabolic. If the patient has prolonged gastric vomiting or suction (sucking out acid), pick alkalosis • For everything else that isn’t lung, pick metabolic acidosis • So, when you don’t know what to pick, pick metabolic acidosis Tip • Set your default setting to Metabolic Acidosis • Always pay attention to modifying phrase rather than original noun Figure 1. Patientcontrolled anesthesia (PCA) pump. Ventilator A ventilator is a machine designed to move breathable air into and out of the lungs, aids patients who are physically unable to breathe, or breathing insufficiently to breathe … A ventilators is equipped with a high and a low-pressure alarm ts y. co m High pressures alarms are always triggered by increased resistance to air flow. Look for obstructions, i.e., • Kinks in tubing … Solution: unkink the tube • Condensed water in the dependent tube … Solution: empty it • Mucus plugs … Solution: Ask pt to turn, cough, deep breathe; or suction the tubing PRN ng H er o -E What is the appropriate order to address high pressure alarm in a mechanical ventilator? • (1) Unkink. (2) Empty water out of tubing. (3) turn pt, ask pt to cough or deeply breathe, and (4) suction N ur si Low pressures alarms are always triggered by decrease in resistance. This can be caused by • Main tubing disconnection • O2 sensor tube disconnection • In both cases, reconnect the disconnected tubing unless tube is on floor … Bag pt and call Respiratory Therapist The ventilator may be set too high or too low • Setting is too high … Pt is overventilated o Respiratory Alkalosis … Panting • Setting is too low … Pt is underventilated o Respiratory Acidosis … Pt is retaining CO2 Question The physician wants to wean pt off vent in the morning. At 6 am, the ABGs say respiratory acidosis. What would you do next? • Notify the physician that the pt is not ready to be weaned off the respirator o Pt is is respiratory acidosis, which means that he is underventilated … Therefore not ready to be weaned off the ventilator o If pt were in respiratory alkalosis (overventilated), he should be ready to be weaned off