Ch 6: Fluid, Electrolyte, Acid-Base Homeostasis Pt 2

Chloride Function

Assists in fluid distribution by attaching to water or sodium

Found in gastric secretions, pancreatic juices, bile, and cerebrospinal fluid

Excreted through the kidneys

Chloride

Mineral electrolyte and major extracellular anion

Normal range: 98-108 mEq/L

Phosphorus

Mostly found in the bones; small amounts are in the bloodstream

Plays a role in bone and tooth mineralization, cellular metabolism, acid-base balance, and cell membrane formation

Main source is dietary intake

Excreted through the kidneys

Normal range: 2.5-4.5 mg/dL

pH

⚬balance is vital in keeping the body optimally functioning

Our bodies have compensatory mechanisms to keep

homeostasis

⚬you will be able to identify acid-base imbalances and implement nursing interventions to improve the imbalance

Acid-Base Balance

Measured by pH

Normal serum pH: 7.35-7.45)

Body fluids, kidneys, and lungs help maintain balance

Subtle changes can cause serious effects

pH regulation

reflects hydrogen concentrations

￭Hydrogen is an acid

￭The more hydrogen, the lower the pH

PH Acid

by-products of metabolism

￭Volatile acids (example- carbonic acid)

￭Volatile gases (example- carbon dioxide)

￭Nonvolatile acids

Buffers

Chemicals that combine with an acid or base to change pH

Immediate reaction to counteract pH variations until compensation is initiated

Four Buffer Mechanisms

The bicarbonate-carbonic acid system, phosphate system, hemoglobin system, and protein system

Potassium Hydrogen Buffers

Potassium and hydrogen move interchangeably into and out of the cell to balance pH

With extracellular excess, hydrogen moves inside the cell for buffering; in exchange, potassium moves out

Potassium imbalances can lead to pH imbalances

Respiratory Regulation

Manages pH by altering carbon dioxide excretion

Uses chemoreceptors

Responds quickly, but is short lived

Speeding up respirations

excrete more carbon dioxide, decreasing acidity

Slowing down Respirations

excrete less carbon dioxide, increasing acidity

Renal Regulation

Alters the excretion or retention of hydrogen or bicarbonate

More effective because it is permanently removing hydrogen

Responds the slowest, but lasts the longest

Acid-Base Imbalances Respiratory System

compensates by increasing or decreasing ventilation

PaCO₂ is acidic

Normal arterial PaCO2 35-45 mmHg

Acid-Base Imbalances Renal System

compensates by producing acidic or alkaline urine

HCO₃- (bicarbonate) is basic

Normal HCO3 22-26 mEq/L

Acidosis cause

Ketones are produced too quickly and build up in the blood

Respiratory Opposite, Metabolic Equal

ROME (acronym)

Normal Values

pH: 7.35-7.45

PCO2: 35-45 mm Hg

HCO3: 22-26 mEq/L

Metabolic Acidosis

Low pH

Normal PCO2

Low HCO3

Metabolic Alkalosis

High pH

Normal PCO2

High HCO3

Respiratory Acidosis

Low pH

High PCO2

Normal HCO3

Respiratory Alkalosis

High pH

Low PCO2

Normal HCO3

Acid Base Balance Compensation

￭If the problem causing the pH imbalance originates in the lungs, the kidneys initiate efforts to correct it

￭If the problem causing the pH imbalance originates outside the lungs, the lungs initiate efforts to correct it

Metabolic Acidosis Causes

￭Bicarbonate deficit: intestinal and renal losses

￭Acid excess: tissue hypoxia resulting in lactic acid accumulation, ketoacidosis, drugs, toxins, and renal retention

Metabolic Acidosis Manifestations

￭Appear as regulatory systems fail to maintain pH within normal range

￭Include headache, malaise, weakness, fatigue, lethargy, coma, warm and flushed skin, nausea, vomiting, anorexia, hypotension, dysrhythmias, shock, Kussmaul's respirations, and hyperkalemia

Metabolic Alkalosis Causes

￭Excess bicarbonate: excessive antacid use, use of bicarbonate-containing fluids, hypochloremia

￭Deficient acid: gastrointestinal loss, hypokalemia, renal loss, hypovolemia, hyperaldosteronism

Metabolic Alkalosis Manifestations

￭Appear as regulatory systems fail to maintain pH within normal range

￭Include mental confusion, hyperactive reflexes, paresthesia, tetany, seizures, respiratory depression, dysrhythmias, and coma

Respiratory Acidosis Causes

Results from carbon dioxide retention, which increases carbonic acid

Caused by conditions that result in hypoventilation or decreased gas exchange

Include acute asthma exacerbations, chronic obstructive pulmonary disease, airway obstructions, pulmonary edema, pneumonia, drug overdose, respiratory failure, and central nervous system depression

Respiratory Acidosis Manifestations

￭Appear as regulatory systems fail to maintain pH within normal range

￭Include headache, blurred vision, tremors, muscle twitching, vertigo, irritability, disorientation, lethargy, coma, tachycardia leading to bradycardia, blood pressure fluctuations, diaphoresis

Respiratory Alkalosis Causes

Results from excess exhalation of carbon dioxide, which leads to carbonic acid deficits

Caused by conditions that result in hyperventilation

￭Include acute anxiety, pain, fever, hypoxia, gram-negative septicemia, aspirin overdose, excessive mechanical ventilation, and hypermetabolic states

Respiratory Alkalosis Manifestations

￭Appear as regulatory systems fail to maintain pH within normal range

￭Include paresthesia, dizziness, vertigo, syncope, muscle irritability and twitching, tetany, inability to concentrate, seizures, tachycardia, dysrhythmias, dry mouth, anxiety, excessive diaphoresis, and coma

ARTERIAL BLOOD GAS (ABG) INTERPRETATION

⚬Uncompensated

⚬Partially compensated

Fully compensated

⚬pH ABG

serum hydrogen concentration

￭Indicates acid-base status

⚬PaCO₂ ABG

partial pressure of carbon dioxide

￭Indicates the adequacy of pulmonary ventilation

⚬HCO₃ ABG

bicarbonate

￭Indicates the activity in the kidneys to retain or excrete bicarbonate

⚬PaO₂ ABG

partial pressure of oxygen

￭Indicates serum oxygen concentration

ABG Base Excess/Deficit

￭Indicates serum buffer concentration, particularly bicarbonate

￭Positive values indicate an excess of base or a deficit of acid

￭Negative values indicate a deficit of base or an excess of acid

First step ABG

Is the pH basic (>7.4), acidic (

Second step ABG

Is the PaCO₂ basic (

Third step ABG

Is the HCO₃ basic (>26 mEq/L), acidic (

Fourth step in ABG (Look for Patterns)

￭Two As mean acidosis, two Bs mean alkalosis

￭If one of the As or Bs is CO₂, it suggests respiratory disorder

￭If one of the As or Bs is HCO₃, it suggests metabolic disorder

￭Three As or Bs indicate a mixed disorder; 3 As indicate acidosis and 3 Bs indicate alkalosis

ABG Steps

For each step, note "B" if basic, "A" if acidic, or normal if within normal limits

Fifth step ABG Determine compensation

￭Uncompensated if the unpaired result is within normal range

￭Partially compensated if the unpaired result is the opposite letter of the pairs, but pH is still abnormal

￭Fully compensated if the unpaired result is the opposite letter and the pH has returned to normal range

Uncompensated

if the unpaired result is within normal range

Partially compensated

if the unpaired result is the opposite letter of the pairs, but pH is still abnormal

Fully compensated

if the unpaired result is the opposite letter and the pH has returned to normal range

Acid Base Balance (ABG)

⚬If all three are normal, the ABGs are normal

⚬If CO2 and HCO3 are abnormal, ABGs are fully compensated when pH has returned to normal and uncompensated when two values are abnormal

⚬If three are abnormal, ABGs are partially compensated, or combined disorder is happening

⚬Lungs (regulates CO2) and kidneys (retains or excretes HCO3) are the main players in acid-base balance/ imbalance