Arterial Blood Gases (ABGs) and Acid-Base Balance

Flashcards covering key vocabulary, chemical buffer equations, diagnostic ranges, clinical manifestations, and the ROME mnemonic for Arterial Blood Gas (ABG) analysis based on lecture notes.

Normal SpO2 Range

$SpO_2 = 94\%$ to $99\%$ measured via pulse oximetry.

Arterial Blood Gas (ABG)

A diagnostic study evaluating oxygenation and acid-base balance, providing information on $PaO_2$, $PaCO_2$, $pH$, $HCO_3^-$, and $SaO_2$.

Nursing Pre-ABG Sample Requirement

Ensure no changes are made to $\text{O}_2$ for $15\text{ minutes}$ before drawing an arterial blood gas sample.

Syringe Requirement for ABG

Use a heparinized syringe when collecting an arterial blood gas sample.

Post-ABG Sampling Nursing Action

Apply pressure to the site following the arterial blood gas draw.

Acid-Base Homeostasis

Maintaining a steady balance between acids and bases to achieve homeostasis in the body.

Conditions Causing Acid-Base Imbalances

Diabetes mellitus, Chronic obstructive pulmonary disease (COPD), and Kidney disease.

Normal Blood pH

$7.35$ to $7.45$.

Acidosis Lethal pH Limit

A $pH$ below $6.8$ leads to death.

Alkalosis Lethal pH Limit

A $pH$ above $7.8$ leads to death.

Normal Carbonic Acid to Base Bicarbonate Ratio

$1$ part Carbonic acid to $20$ parts Base bicarbonate ($1:20$ ratio).

Three Regulatory Mechanisms of Acid-Base Balance

Buffers, Respiratory system, and Renal system.

Buffer System

Regulatory mechanism that acts chemically to change strong acids to weak acids or bind acids.

Primary Chemical Buffers

Carbonic acid–bicarbonate, phosphate, protein, and hemoglobin buffers, along with shifting of hydrogen in and out of cells.

Carbonic Acid–Bicarbonate Buffer Reaction

$HCl + NaH_2CO_3 \rightarrow NaCl + H_2CO_3$ (Strong acid + strong base is buffered into salt and weak acid).

Respiratory Buffer Reaction Equation

$$CO_2 + H_2O \rightarrow H_2CO_3 \rightarrow H^+ + HCO_3^-$$

Respiratory Control Center

The medulla controls breathing to regulate $\text{CO}_2$ levels.

Effect of Increased Respirations on CO2

Leads to increased $\text{CO}_2$ elimination and decreased $\text{CO}_2$ in the blood.

Effect of Decreased Respirations on CO2

Leads to $\text{CO}_2$ retention in the blood.

Renal Acid Elimination Mechanisms

Conserves bicarbonate and excretes acid by secreting free hydrogen, combining $H^+$ with ammonia ($NH_3$), and excreting weak acids.

Acid-Base Imbalance Classification Criteria

Respiratory ($CO_2$) or metabolic ($HCO_3^-$), Acidosis or alkalosis, Acute or chronic.

Carbonic Acid Excess

Respiratory Acidosis ($pH < 7.35$ due to excessive carbonic acid/$\text{CO}_2$).

Carbonic Acid Deficit

Respiratory Alkalosis ($pH > 7.45$ due to deficient carbonic acid/$\text{CO}_2$).

Base Bicarbonate Deficit

Metabolic Acidosis ($pH < 7.35$ due to deficit in base bicarbonate/$HCO_3^-$).

Base Bicarbonate Excess

Metabolic Alkalosis ($pH > 7.45$ due to excess base bicarbonate/$HCO_3^-$).

Causes of Respiratory Acidosis

COPD, Pneumonia, and Respiratory failure.

Causes of Respiratory Alkalosis

Hyperventilation, Anxiety, and Pain.

Causes of Metabolic Acidosis

DKA, Renal Failure, and Diarrhea.

Causes of Metabolic Alkalosis

Vomiting, NG Suction, and Diuretics.

Clinical Manifestations of Acidosis

Central nervous system (CNS) depression and Kussmaul respirations.

Clinical Manifestations of Alkalosis

CNS irritability and Hypocalcemia.

Source vs pH in Clinical Manifestations

Manifestations are based on $pH$, not the source of the imbalance.

Normal PaCO2 Range

$35-45\,mmHg$.

Normal HCO3 Range

$22-26\,mEq/L$.

Definition of Acidosis (ABG Simple)

$pH < 7.35$; characterized by too much acid and a sluggish body.

Definition of Alkalosis (ABG Simple)

$pH > 7.45$; characterized by too much base and a twitchy body.

Neurological Effect of Acidosis

Confused and Drowsy brain manifestation.

Neurological Effect of Alkalosis

Anxious and Restless brain manifestation.

Cardiac Effect of Acidosis

Weak and Slow heart manifestation.

Cardiac Effect of Alkalosis

Fast and Racing heart manifestation.

Muscular Effect of Acidosis

Weak and Fatigued muscle manifestation.

Muscular Effect of Alkalosis

Twitchy and Crampy muscle manifestation.

Potassium Alteration in Acidosis

Increased potassium level causing Hyperkalemia ($\uparrow K^+$).

Potassium Alteration in Alkalosis

Decreased potassium level causing Hypokalemia ($\downarrow K^+$).

Respiratory Effect of Acidosis

Slow, Shallow Breathing.

Respiratory Effect of Alkalosis

Fast, Deep Breathing.

ACID vs. BASE Body Mnemonic

ACID = DOWN (Depressed, Weak, Hyperkalemia) | BASE = BOOSTED (Anxious, Twitchy, Hypokalemia).

Steps for ABG Interpretation

1. Evaluate $pH$, 2. Analyze $PaCO_2$, 3. Analyze $HCO_3^-$, 4. Determine if $CO_2$ or $HCO_3^-$ matches alteration, 5. Decide if body is attempting to compensate.

ROME Mnemonic - Respiratory

Respiratory Opposite: Alkalosis = $\uparrow pH$ $\downarrow PaCO_2$; Acidosis = $\downarrow pH$ $\uparrow PaCO_2$.

ROME Mnemonic - Metabolic

Metabolic Equal: Acidosis = $\downarrow pH$ $\downarrow HCO_3^-$; Alkalosis = $\uparrow pH$ $\uparrow HCO_3^-$.