N271 Exam 1 Review

What are the normal ABG values?

pH: 7.35-7.45, PaCO₂: 35-45 mmHg, HCO₃⁻: 22-26 mEq/L, PaO₂: 80-100 mmHg, SaO₂: 95-100%

What does pH measure?

The amount of hydrogen ions (acidity) in the blood.

What does PaCO₂ represent?

Respiratory function; amount of carbon dioxide in the blood.

What does HCO₃⁻ represent?

Metabolic efficiency and kidney function.

Which body system primarily regulates CO₂?

Respiratory system.

Which body system primarily regulates bicarbonate (HCO₃⁻)?

Kidneys (renal system).

What are the three lines of defense against acid-base imbalances?

1. Chemical buffers 2. Respiratory system 3. Renal system

Which line of defense acts the fastest?

Chemical buffers.

Which line of defense is best for short-term compensation?

Respiratory system.

Which line of defense provides long-term compensation?

Renal system.

What is respiratory acidosis?

pH <7.35, PaCO₂ >45, CO₂ retention due to hypoventilation.

What causes respiratory acidosis?

Opiate overdose, morbid obesity/sleep apnea, chest trauma, foreign body aspiration.

What are the signs and symptoms of respiratory acidosis?

Headache, altered LOC, restlessness, decreased respirations, can progress to cardiac arrest.

What is the priority nursing intervention for respiratory acidosis?

Improve ventilation and clear the airway (ABCs first).

What is hypercapnia?

Excess CO₂ in the blood.

What is respiratory alkalosis?

pH >7.45, PaCO₂ <35, hyperventilation causes excessive CO₂ loss.

What causes respiratory alkalosis?

Anxiety, hyperventilation, psychological stress, fever, sepsis.

Why do patients become anxious or restless during respiratory alkalosis?

Hyperventilation causes cerebral vasoconstriction, decreasing blood flow to the brain.

What ECG change may occur with respiratory alkalosis?

Prolonged PR interval.

What is the priority treatment for respiratory alkalosis?

Treat the underlying cause (anxiety, fever, sepsis).

What is metabolic acidosis?

pH <7.35, HCO₃⁻ <22, increased hydrogen ions.

What are common causes of metabolic acidosis?

DKA, kidney failure, chronic alcoholism, diarrhea.

Why does diarrhea cause metabolic acidosis?

Bicarbonate is lost in stool.

Why does DKA cause metabolic acidosis?

Fat breakdown produces acidic ketones.

Why does metabolic acidosis cause hyperkalemia?

Excess H⁺ moves into cells, pushing K⁺ out into the bloodstream (relative hyperkalemia).

What are Kussmaul respirations?

Deep, rapid respirations used to compensate for metabolic acidosis.

What causes fruity breath in metabolic acidosis from DKA?

Ketone production from fat metabolism.

What cardiovascular changes occur with metabolic acidosis?

Decreased myocardial function, hypotension, arrhythmia risk.

What is the priority treatment for metabolic acidosis caused by DKA?

1. Fluids 2. Regular insulin 3. Monitor potassium 4. Monitor CNS status.

When is sodium bicarbonate given for metabolic acidosis?

When pH <7.1.

What is metabolic alkalosis?

pH >7.45, HCO₃⁻ >26, decreased hydrogen ions.

What are common causes of metabolic alkalosis?

Vomiting, NG suction, loop diuretics (Lasix), hypokalemia.

Why does vomiting cause metabolic alkalosis?

Loss of hydrochloric acid (HCl).

What electrolyte imbalances commonly occur with metabolic alkalosis?

Hypokalemia, hypocalcemia.

What are the signs and symptoms of metabolic alkalosis?

Slow, shallow respirations, muscle spasms/tetany, tremors, ventricular tachycardia or ventricular fibrillation.

Why does tetany occur in metabolic alkalosis?

Hypocalcemia increases neuromuscular excitability.

What is the priority treatment for metabolic alkalosis?

Stop NG suction if possible, stop loop/thiazide diuretics, administer potassium-sparing diuretic (Aldactone), treat vomiting.

Which acid-base imbalance is caused by hypoventilation?

Respiratory acidosis.

Which acid-base imbalance is caused by hyperventilation?

Respiratory alkalosis.

Which acid-base imbalance is associated with DKA?

Metabolic acidosis.

Which acid-base imbalance is associated with prolonged vomiting?

Metabolic alkalosis.

A patient's ABGs are: pH 7.30, PaCO₂ 52, HCO₃⁻ 24. What disorder is present?

Respiratory acidosis.

A patient's ABGs are: pH 7.49, PaCO₂ 30, HCO₃⁻ 24. What disorder is present?

Respiratory alkalosis.

A patient's ABGs are: pH 7.28, HCO₃⁻ 18, PaCO₂ 38. What disorder is present?

Metabolic acidosis.

A patient's ABGs are: pH 7.50, HCO₃⁻ 30, PaCO₂ 40. What disorder is present?

Metabolic alkalosis.

What is a sensible fluid loss?

Fluid loss that can be measured, such as urine output.

What is an insensible fluid loss?

Fluid loss that cannot be accurately measured, such as through the skin and lungs.

Why are neonates at high risk for dehydration?

About 80% of their body weight is water, so they become dehydrated quickly.

When the body is dehydrated, what happens to laboratory values?

Labs become more concentrated and appear elevated.

What is ADH?

Antidiuretic hormone (vasopressin), a water-retaining hormone.

Where is ADH produced and where is it released?

Produced in the hypothalamus, stored and released by the posterior pituitary.

When is ADH released?

When blood volume is low or serum sodium/osmolality is high.

What does ADH do in the kidneys?

Increases water reabsorption, concentrates urine, decreases urine output.

What effect does ADH have on blood pressure?

Increases blood pressure through vasoconstriction and increased blood volume.

What activates the RAAS?

Decreased blood pressure or decreased renal perfusion.

What is the purpose of the RAAS?

Increase blood pressure, blood volume, and kidney perfusion.

Which hormone causes sodium and water reabsorption in the RAAS?

Aldosterone.

Which IV fluid is isotonic?

0.9% Normal Saline and Lactated Ringer's.

What is the main use of isotonic fluids?

Hypovolemia, burns, maintaining intravascular volume.

Which IV fluid is hypotonic?

0.45% Normal Saline.

What happens to cells when hypotonic fluids are administered?

Cells swell because water moves into them.

Which IV fluid is hypertonic?

3% Normal Saline.

What happens to cells when hypertonic fluids are administered?

Cells shrink because water moves out of them.

What type of fluid is D5W?

Starts isotonic, becomes hypotonic after dextrose is metabolized.

What type of fluid is D5 ½ NS?

Starts hypertonic, becomes hypotonic after dextrose is metabolized.

What is the normal sodium level?

135-145 mEq/L.

What is hyponatremia?

Sodium <135 mEq/L.

Severe hyponatremia is defined as what sodium level?

≤120 mEq/L.

What happens to cells during hyponatremia?

Cells swell because water shifts into the cells.

What are common causes of hyponatremia?

Diuretics, osmotic diuresis, GI losses, wound drainage.

What are the neurologic manifestations of hyponatremia?

Confusion, decreased LOC, headache, seizures.

What GI findings occur with hyponatremia?

Hyperactive bowel sounds, cramping, diarrhea.

Why do patients develop muscle weakness with hyponatremia?

Sodium is needed for nerve impulse transmission.

What is the priority treatment for severe hyponatremia?

3% hypertonic saline given slowly.

Why is 3% saline given slowly?

To prevent fluid overload and pulmonary edema.

What medication antagonizes ADH to treat hyponatremia?

Tolvaptan (Samsca).

What is hypernatremia?

Sodium >145 mEq/L.

What happens to cells during hypernatremia?

Cells shrink because water leaves the cells.

What are common causes of hypernatremia?

Renal failure, prednisone, excessive sodium intake, sodium-containing IV fluids.

What are the signs of hypernatremia?

Thirst, dry mucous membranes, agitation, lethargy, muscle twitching.

Why are hypotonic fluids given slowly for hypernatremia?

To prevent cerebral edema.

What is the normal potassium level?

3.5-5.0 mEq/L.

What is hypokalemia?

Potassium <3.5 mEq/L.

What are common causes of hypokalemia?

Diuretics, vomiting, diarrhea, NG suction, excessive sweating.

What respiratory finding occurs with hypokalemia?

Weak diaphragm and shallow respirations.

What GI findings occur with hypokalemia?

Hypoactive bowel sounds, ileus, constipation.

What ECG findings are seen in hypokalemia?

Flattened T waves, U waves, atrial fibrillation.

What is the biggest danger of hypokalemia?

Fatal cardiac arrhythmias.

How should IV potassium be administered?

Never IV push; administer slowly by IV piggyback or central line.

What is hyperkalemia?

Potassium >5.0 mEq/L.

What are common causes of hyperkalemia?

Renal failure, dehydration, acidosis, tissue damage, potassium supplements, blood transfusions, potassium-sparing diuretics.

What ECG findings occur with hyperkalemia?

Peaked T waves and wide QRS complex.

Why is hyperkalemia a medical emergency?

It can cause heart block, bradycardia, and cardiac arrest.

What medication shifts potassium into cells?

Regular insulin with D50.

What medication removes potassium from the body?

Kayexalate.

What medication protects the heart during severe hyperkalemia?

Calcium gluconate.

What is the normal calcium level?

8.5-10.5 mg/dL.

What is hypocalcemia?

Calcium <8.5 mg/dL.

What is the most common cause of hypocalcemia?

Hypoalbuminemia.

What are two hallmark signs of hypocalcemia?

Chvostek's sign and Trousseau's sign.