MS ACID BASE IMBALANCE

WHAT IS ACID BASE BALANCE

• Body's ability to keep pH between $7.35$ and $7.45$ by producing and eliminating H+.

• Essential for cell function, oxygen delivery, and enzyme activity.

Definitions

• Acids: Unbind H+, increasing H+ in water solution.

• Bases: Bind with H+, lowering H+ in water solution.

• Buffers: Can react as either an acid or a base.

ACID BASE REGULATORY ACTIONS AND MECHANISMS

• H+ is constantly produced from normal metabolism:

  • Carbs → CO2

  • Proteins ^→ Sulfuric acids

  • Lipids → Fatty acids → Ketoacids

• Bases (HCO3) produced mainly in pancreas, kidney, and RBCs; HCO3 can be reabsorbed by kidneys.

• Diseased states (shock, sepsis, hypoxia, burns) can lead to excess acid production.

• Breathing regulates CO2:

  • Excess exhalation (hyperventilation) →lose CO2 → alkalotic.

  • Insufficient exhalation (hypoventilation) → retain CO2 → acidic.

CHEMICAL ACID-BASE CONTROL ACTIONS

• Homeostasis requires consistent H+ production and balanced CO2 loss.

• Buffers = 1st line of defense:

  • Neutralize excess H+ to prevent dangerous pH shifts.

  • Act immediately before lungs and kidneys respond.

  • Common buffer systems:

    • Phosphate buffer system (mainly in kidneys).

    • Proteins (albumin, globulins, hemoglobin) → act like sponges, donating H+ as needed.

ACID-BASE CONTROL ACTIONS AND MECHANISMS: RESPIRATORY

• Respiratory system = 2nd line of defense (activated when buffers are overwhelmed).

  • Lungs respond quickly (within minutes) to pH changes by regulating CO2.

• Hyperventilation:

  • Blows off CO2 → decreased CO2 = decreased H+ → pH elevation (alkaline).

  • Causes: Anxiety, fever, pain, early sepsis, high altitude.

• Hypoventilation:

  • Retains CO2 → increased CO2 = increased H+ →pH decrease (acidic).

  • Causes: Respiratory depression, drug overdose, COPD.

ACID-BASE CONTROL ACTIONS AND MECHANISMS: KIDNEYS

• Renal system = 3rd line of defense (when respiratory system is insufficient).

  • Slower to respond (takes $24-48$ hours) but stronger and longer-lasting.

  • Too acidic blood: Kidneys reabsorb bicarb.

  • Too alkaline blood: Kidneys excrete bicarb.

  • Kidneys remove acids by forming phosphoric acid (phosphate + H+) and ammonium (ammonia + H+), excreted in urine.

  • Most diseased states → retain more H+.

COMPENSATION

• Body's attempt to normalize abnormal pH.

• Life-threatening pH: below $6.9$ or above $7.8$.

• Respiratory Compensation:

  • Fast response: seconds to minutes.

  • Fixes metabolic problems by adjusting CO2 exhalation (faster/deeper breathing = more CO2 removal).

• Kidney Compensation:

  • Slower: hours to days.

  • Fixes respiratory problems by eliminating H+ or producing more HCO3.

• Metabolic problem → Respiratory compensation.

• Respiratory problem → Kidney (Metabolic) compensation.

ACID-BASE IMBALANCES

• Occur when pH is too acidic or alkalotic due to overwhelmed regulatory mechanisms.

• Not diseases themselves, but conditions that impair organ function and can be life-threatening.

• Treatment focuses on correcting the root cause.

ACIDOSIS - pH <7.35

• Actual Acidosis: Too much acid production/improper acid elimination.

  • Examples: DKA, seizures, lung problems, kidney failure.

• Relative Acidosis: Not enough base, even if acid levels are normal.

  • Examples: Diarrhea, pancreatitis, dehydration.

• Dangers:

  • Excess H+ affects other salts (e.g., K+).

  • Small pH changes can shut down enzymes/hormones and affect nerves/muscles.

  • Cardiac dysrhythmias are common.

METABOLIC ACIDOSIS

• H+ ions:

  • Overproduction: Excess fatty acid breakdown (DKA, starvation), anaerobic glucose metabolism (seizures), excessive toxin intake (ETOH, aspirin).

  • Under-elimination: Acid made normally, but body can't remove it (lung problems → can't exhale CO2, kidney failure → can't remove H+).

• HCO3 ions:

  • Underproduction: Kidneys, pancreas, or liver dysfunction (kidney failure, pancreatic/liver disease).

  • Over-elimination: Lost from body (e.g., diarrhea).

RESPIRATORY ACIDOSIS

• Cause: CO2 retention due to ineffective breathing → increased free H+ → acidic blood.

• Causes of CO2 retention:

  • Slow/shallow breathing (head injury, opioids).

  • Inadequate chest expansion (rib fractures).

  • Airway obstruction (asthma, mucous plug).

  • Reduced alveolar capillary diffusion (pneumonia).

ACIDOSIS ASSESSMENT

• Neurological Signs: Cognitive changes (awareness, time, place, person) due to retained H+.

• Cardiovascular Signs: Hypotension, tachycardia, dysrhythmias (reduced O2 carrying capacity due to vasodilation).

• Respiratory Signs: Kussmaul respirations (deep, rapid breathing in metabolic acidosis), shallow/slow breathing (respiratory acidosis), cyanosis (severe hypotension).

• Integumentary: Warm, flushed skin (respiratory acidosis); cool, clammy skin (metabolic acidosis from shock).

ACIDOSIS - DIAGNOSTIC ABG’S

• ABGs measure lung/kidney efficacy in acid-base and O2 balance.

• Metabolic Acidosis:

  • pH <7.35

  • PaO2 normal

  • PaCO2 normal or slightly decreased

  • HCO3 low (<22 mEq/L)

  • Serum potassium high (H+ kicks K+ out of cells)

• Respiratory Acidosis:

  • pH <7.35

  • PaO2 low

  • PaCO2 high

  • HCO3 variable

  • Serum potassium may be high

ACIDOSIS - CARE

• Metabolic Acidosis:

  • Goal: Treat underlying problem.

  • DKA → insulin.

  • Diarrhea → rehydration, antidiarrheals.

  • Restore fluid balance and monitor electrolytes.

• Respiratory Acidosis:

  • Goal: Improve gas exchange.

  • Drug therapy (bronchodilators, steroids, reversal agents).

  • O2 therapy.

  • Ventilatory support if needed.

  • Prevent worsening respiratory failure (caution with COPD pts).

ALKALOSIS - pH >7.45

• Actual Alkalosis: Body makes too much base (bicarb) or can't get rid of it.

  • Example: Antacid overuse.

• Relative Alkalosis: Amount of acids decreases, even if bases don't increase.

  • Examples: Prolonged vomiting, diuretic overuse.

• Dangers:

  • K+ shifts into cells → hypokalemia.

  • Can lead to hypoventilation and hypoxia.

• Acidosis is generally more life-threatening, but alkalosis is also dangerous.

METABOLIC ALKALOSIS (less common than metabolic acidosis)

• Caused by either increase of bases (base excess) or decrease of acids (acid deficit).

• Base excess: Excessive intake alkaline substances.

  • Bicarbs, acetates, citrates (e.g., from preserved blood).

• Acid deficit: Loss of acids from disease or treatments.

  • NG suctioning, loop/thiazide diuretics (loss of H+ ions), excess vomiting, Cushings/Hyperaldosteronism (bicarb retention, H+ loss).

RESPIRATORY ALKALOSIS

• Cause: Excessive loss of CO2 through hyperventilation.

• Causes of hyperventilation:

  • Anxiety/panic attacks, fever, pain, sepsis, high altitude.

  • Brain injury affecting respiratory control.

• Hallmark sign: ABG result with elevated pH and low CO2.

ALKALOSIS ASSESSMENT

• Neurological Signs: Confusion, dizziness, lightheadedness, possible seizure.

• Cardiovascular Signs: Possible hypotension, dysrhythmias (due to low K+).

• Respiratory Signs: Shallow breathing, hypoventilation.

• Neuromuscular Signs: Muscle twitching/cramping, numbness, tingling (especially around mouth and fingers), Trousseau's/Chvostek's signs (due to hypocalcemia).

ALKALOSIS - DIAGNOSTIC ABG’S

• Metabolic Alkalosis:

  • pH >7.45

  • PaO2 normal

  • PaCO2 increased or normal

  • HCO3 high (>28)

• Respiratory Alkalosis:

  • pH >7.45

  • PaO2 low or normal

  • PaCO2 low (<35)

  • HCO3 low or normal

• Hypocalcemia and hypokalemia often occur with alkalosis.

• O2 is low when cause is respiratory in nature.

ALKALOSIS - CARE

• Prevent further losses of H+, K+, Ca2+, Cl-.

• Stop or adjust causative treatment.

• Drug therapy:

  • Antiemetics for vomiting.

  • Electrolyte replacement.

  • Fluids.

• Examples: Stop bicarb antacids, change diuretics.