Comprehensive Notes on Acid-Base and Electrolyte Regulation

Understanding Acid-Base Imbalances

• ROME Mnemonic: Respiratory Opposite ($pH$ and $PaCO_2$ move in opposite directions), Metabolic Equal ($pH$ and $HCO_3^-$ move in the same direction).

• Respiratory Acidosis: $pH \downarrow$, $PaCO_2 \uparrow$. Caused by $CO_2$ retention (e.g., COPD, sedation, pneumonia).

• Respiratory Alkalosis: $pH \uparrow$, $PaCO_2 \downarrow$. Caused by $CO_2$ loss (e.g., anxiety, fever).

• Metabolic Acidosis: $pH \downarrow$, $HCO_3^- \downarrow$. Caused by acid gain (e.g., DKA, shock) or base loss (e.g., diarrhea). Compensation involves deep, rapid Kussmaul respirations.

• Metabolic Alkalosis: $pH \uparrow$, $HCO_3^- \uparrow$. Caused by acid loss (e.g., vomiting, suction) or base gain (e.g., antacids).

Primary Manifestations and Nursing Care

• Acidosis Manifestations: CNS depression (lethargy, confusion, coma), ventricular fibrillation, and warm, flushed skin.

• Alkalosis Manifestations: CNS irritability (dizziness, seizures) and neuromuscular excitability (tetany, hyperreflexia).

• Nursing Goals:     - Acidosis: Restore ventilation and correct underlying acid accumulation.     - Alkalosis: Decrease acid loss or correct base excess.     - Safety: Implement fall precautions for weakness/confusion and monitor respiratory status/ABGs.

Serum Electrolyte Reference Intervals

• Sodium ($Na^+$): $136-145\,mEq/L$.

• Potassium ($K^+$): $3.5-5.0\,mEq/L$.

• Bicarbonate ($HCO_3^-$): $22-26\,mEq/L$.

• Total Calcium ($Ca^{2+}$): $9.0-10.5\,mg/dL$.

• Magnesium ($Mg^{2+}$): $1.3-2.1\,mEq/L$.

• Phosphate ($PO_4^{3-}$): $3.0-4.5\,mg/dL$.

• Chloride ($Cl^-$): $98-106\,mEq/L$.

Electrolyte Imbalances and ECG Patterns

• Hyperkalemia: Peaked T waves, loss of P waves, and widening QRS.

• Hypokalemia: Flattened T waves and presence of a U wave.

• Hypocalcemia: Positive Chvostek sign (facial twitching) and Trousseau sign (carpal spasm).

• Magnesium Imbalances: Hypermagnesemia causes decreased deep tendon reflexes (DTRs); hypomagnesemia causes hyperactive DTRs, tremors, and seizures.

Intravenous Solution Classifications

• Isotonic Solutions ($0.9\% NaCl$, Lactated Ringer’s): Osmolarity $275-295\,mOsm/L$. No net fluid shift; used for volume replacement and resuscitation.

• Hypotonic Solutions ($0.45\% NaCl$, $D_5W$): Osmolarity $<250\,mOsm/L$. Fluid moves into cells; used for cellular dehydration. Avoid in patients with increased ICP (risk of cerebral edema).

• Hypertonic Solutions ($3\% NaCl$, $D_5NS$): Osmolarity $>295\,mOsm/L$. Fluid moves from cells into the vasculature; used for symptomatic hyponatremia and cerebral edema.

• Colloids (Albumin, Dextran): Large molecules increase oncotic pressure to expand plasma volume.

• IV Additives: Including KCl (never given IV push; must be diluted) and magnesium sulfate.

Central Venous Access Devices (CVADs)

• PICC (Peripherally Inserted Central Catheter): For long-term use (weeks to months). Flush every $8-12$ hours and avoid BP measurements in the same arm.

• Central Catheter (CVC): Short-term use; tip placement must be confirmed in the SVC via X-ray.

• Implanted Port: Long-term use; access requires a non-coring Huber needle.

• Removal Safety: Use the Valsalva maneuver during removal and apply an occlusive dressing to prevent air embolism.