Lecture Notes for Adult Health II 

Topic One: Acid Base Disorders(for help interpreting blood gases, go to ABG review page):

1. Metabolic Acidosis:

a. Definition: Excess of Acid(H+) and Deficit of base(HCO₃)

b. Etiologies:Ketoacidosis, Renal Failure, Shock, Loss of bicarb-->diarrhea

c. Signs & Symptoms: headache, nausea, vomiting, diarrhea, sensorium changes, tremors, convulsions

d. Lab tests: Blood gases: ph < 7.35, HCO₃ < 22, pCO₂ < 35 (see ABGs review notes); Blood Chemistry: serum K elevated and serum CO₂ (bicarb)< 22; anion gap is increased

e. Treatment: Treat underlying cause, e.g., correct DKA with insulin, glucose, fluid and electrolyte replacement; correct azotemia with dialysis and/or I.V. sodium bicarbonate; correct shock using therapies to replace volume; strengthen pump(heart) or restore perfusion depending on cause of shock; administer meds to stop diarrhea

f. Case Example: Miss M, age 19, with Type I Diabetes, came to the hospital in DKA after contracting the G.I. flu two days ago. Her blood sugar was 652, urine was positive for ketones, serum K was 5.6 and serum CO₂ (bicarb) was 14. Vital signs were: Temp=100.8, B/P 90/50, P=126, R=30 with rapid and deep(Kussmaul) pattern. Blood gases were: ph=7.31, pCO₂=27, HCO₃=14; BUN was elevated due to dehydration from vomiting and diarrhea. She had not been eating or taking her insulin since the flu started, and was comatose with flushed skin and fruity breath odor on admission. After treatment with insulin, glucose, fluids and electrolytes, along with antiemetics and anti-diarrheals, her values normalized and she became alert and oriented. Before discharge, teaching was instituted regarding diabetic maintenance regimens during illness and when to call the physician.

2. Respiratory Acidosis:

a. Definition: Excess of carbonic acid(H₂CO₃) due to carbon dioxide(pCO₂) retention (hypercapnia)

b. Etiology: Respiratory Failure, COPD, muscular weakness(spinal cord injury)

c. Signs & Symptoms: hypoventilation, sensorium changes, somnolence, semicomatose to comatose state, tachycardia, dysrhythmias

d. Lab tests: Blood gases: ph< 7.35, pCO2 > 45; HCO₃ >27, serum K elevated and serum CO₂(bicarb) increased; hypoxemia(low pO₂)

e. Treatment: Treat underlying cause and improve ventilation by using whatever modality is appropriate--O₂ therapy, IPPB, updraft treatments with bronchodilators, antibiotics, intubation or tracheostomy and mechanical ventilation, suctioning, chest physiotherapy

f. Case Example: Mr. P was admitted to the hospital with acute exacerbation of COPD following a U.R.I. His family had found him confused and in respiratory distress on the morning following the onset of a cold the day before. He was brought into E.R. with 5L of nasal O₂ via cannula, but O₂ sats were still only 91. A venti mask replaced the cannula and was set at 50% with improvement of sats to 93. Initial blood gases had shown a ph of 7.33, pCO₂ of 58, and HCO₃ of 33; the patient had labored respirations. Vital signs: Temp.=99.2, B/P 104/50, P=110, R=26. I.V. fluids were running at 125cc per hour and antibiotics were started. Updraft treatment with Combivent was also initiated, as well as I.V. Solumedrol and Aminophylline. Lungs exhibited wheezes and rhonchi with diminished breath sounds at the bases. Over the next few days he improves, is stabilized and is discharged on oral theophylline(Theodur), steroids, inhalers, and antibiotics. His ABGs are now compensated but show a chronic pattern of obstructive lung disease: ph=7.36, pCO₂=50, and HCO₃=29.

3. Respiratory Alkalosis:

a. Definition: A Deficit of Carbonic Acid(H₂CO₃)

b. Etiology: Hyperventilation following traumatic brain injuries(TBIs); mechanical ventilator control set to cause hyperventilation as part of therapy to reduce Intracranial Pressure(ICP); acute anxiety or panic attack accompanied by tachypnea; early stages of acute hypoxemia due to pulmonary embolism or respiratory failure

c. Signs & Symptoms: Tachypnea, sensorium changes, numbness and tingling of face and extremities(hypocalcemia); possible seizures

d. Labs: ph >7.45, pCO₂ <35, HCO₃<22, serum K and Ca decreased

e. Treatment: Treat underlying cause, for example, if anxiety-- have patient breathe into a paper bag and give emotional support

f. Case Study: A trauma victim came into E.R. with a blunt chest injury following a M.V.C.(Motor Vehicle Crash). On admission, he was alert, c/o right sided chest pain with shortness of breath, and exhibited increased respiratory effort despite being on 100% O₂ via nonrebreather mask(14L/min.). O₂ sats=91. His ABGs showed respiratory alkalosis with values of: ph=7.51, pCO₂=30 and HCO₃=21. After fluid resuscitation and chest tube insertion to treat a pneumothorax, he improved and was sent to I.C.U.

4. Metabolic Alkalosis:

a. Definition: Deficit of H+ and excess of Base(HCO₃)

b. Etiology: Gastric losses via vomiting, N/G tubes, or lavage and potent diuretics.

c. Signs & Symptoms: Nausea, vomiting, sensorium changes, tremors, convulsions(hypocalcemia)

d. Labs: ph >7.45, HCO₃>27, pCO2>45, serum K and Ca decreased

e. Treatment: Treat underlying cause, treat symptoms(antiemetics), replace fluid and electrolytes, discontinue causative drugs

f. Case Study: In report you are told that an elderly patient with an intestinal obstruction has put out 2000cc during the night shift through her N/G tube. On assessing her, you find that she is c/o weakness, shakiness, tingling in her fingers, and also questioning where she is and why is she "tied down" by tubings. These are changes in her condition over the night shift from the evening before. Her morning labs reveal a serum K of 3.1, a serum Cl of 88 and serum Ca of 7.7. Her ABGs reveal a ph of 7.54, HCO₃ of 35, and pCO₂ of 52. Her respirations are slow and shallow. Immediate treatment includes correcting fluid and electrolyte losses with potassium, chloride and calcium solutions, and preparation for exploratory surgery to correct the obstruction.

5. Metabolic and Respiratory Acidosis :

a. Definition: Both states present at the same time which is more profound than either one alone

b. Etiology: Uncorrected respiratory acidosis leading to anaerobic metabolism by the tissues and resulting lactic acidosis as in Cardiac Arrest

c. Signs & Symptoms: lethargy, restlessness, weakness, EKG changes, low B/P, thready pulses, altered respiratory pattern

d. Labs: ABGs: ph <7.35, pCO₂ >45, HCO₃ <22, serum K elevated, hypoxemia and increased anion gap

d. Treatment: Treat underlying cause and give life support as needed

e. Case Example: A patient in I.C.U. following trauma has multiorgan failure and presents with ARDS(Adult Respiratory Distress Syndrome) and Septic Shock. His blood gases show the following parameters: ph=7.22, pCO₂=65 and HCO₃=12. He has both respiratory and metabolic acidosis due to respiratory failure and shock.

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