Fluids and Electrolytes, Acids and Bases Chapter 4

Distribution of Body Fluids Total body water – all fluids – 60% weight (kg) Intracellular fluid (ICF) 40% TBW Extracellular fluid (ECF) 20% TBW Interstitial fluid – between cells Intravascular fluid – blood plasma Lymph, synovial, intestinal, CSF, sweat, urine, pleural, peritoneal, pericardial and intraocular fluid

“cells live in a fluid environment with electrolytes and acid base concentrations maintained within a narrow range” changes or shifts → radically alter metabolism → life threatening

Pediatrics Aging Distribution of Body Fluids 75% to 80% body weight Susceptible to significant changes in body fluids - dehydration Aging ↓ % of total body water adipose and muscle mass ↓ renal function ↓ thirst perception

Water Movement Between ICF and ECF “water, nutrients and waste products” capillary interstitial space 1.Capillary hydrostatic pressure – blood pressure “fluid out” 2.Capillary oncotic pressure – water attraction “fluid in”(Plasma Proteins) Interstitial hydrostatic pressure – fluid towards capillary Interstitial oncotic pressure – water attraction “fluid in”

water movement

Edema: 4 Major Causes “excessive accumulation of fluids within the interstitial space” 1.↑ hydrostatic pressure Venous obstruction – DVT, hepatic obstruction Salt and water retention – heart, renal failure 2.↓ plasma oncotic pressure ↓ albumin – liver disease, malnutrition, kidney disease, burns, hemorrhage

Edema ↑ capillary permeability – trauma, burns, neoplastic and allergic reactions Lymph obstruction – removal nodes (surgery) inflammation or tumors

Water : ADH – hypothalamus – posterior pituitary Na+ and Cl- Sodium, Chloride & Water Balance “kidneys and hormones” – central role Water : ADH – hypothalamus – posterior pituitary Na+ and Cl- aldosterone – adrenal gland Natriuretic hormones– atrial muscle

Sodium, Chloride Balance Sodium (Na+) Primary ECF cation Regulates osmotic forces Role Neuromuscular irritability, acid-base balance, cellular reactions, and membrane transport Chloride (Cl-) Primary ECF anion Provides electroneutrality

Sodium and Water Balance Balance between Na+ and H2O - ↑ or ↓ of salt ↑ or ↓ water Tonicity – change in concentration of solutes (salt) with relation to solvent (water)

Tonicity (280 – 294m Osm) Isotonic – 0.9% NaCl – iso osmolar imbalance no cells Hypertonic – ECF > 0.9% NaCl – (↓ H2O or ↑ salt) cells shrink Hypotonic – ECF < 0.9% NaCl (↑ H2O or ↓ salt) cells swell “Extracellular Fluid”- interstitial space

Sodium (Na+) 90% ECF cations 135 – 145 mEq/L Hypernatremia - > 145 mEq/L Hyponatremia - < 135 mEq/L

Hypernatremia-causes ↑ Na or ↓ H2O IV therapy – acidosis (NaHCO3) Cushing's Syndrome - ↑ ACTH → aldosterone fever, respiratory infection - ↓ H2O diabetes, diarrhea - ↓ H2O ↓ H2O intake - coma H2O movement ICF → ECF(interstitial) Manifestations Intracellular dehydration: convulsions, thirst, fever, muscle twitching, hyperreflexia

Hyponatremia ↓ Na or ↑ H2O Vomiting, diarrhea, GI suction, burns, diuretics, D5W replacement (isotonic sol’n) Manifestations Lethargy, confusion, depressed reflexes, seizures, coma, hypotension, tachycardia, ↓ urine output

Hypochloremia Result of hyponatremia or ↑ HCO3 Vomiting – loss HCl Cystic fibrosis

Potassium (resting potential) Major intracellular electrolyte 98% intracellular – Na – K – ATP Pump 3.5 – 5.0 mEq/L Transmission and conduction of nerve impulses, normal cardiac rhythm, skeletal and smooth muscle contractions: “action potentials” “BAD BOY of ELECTROLYTES”

Potassium Levels Change in pH affects K+ balance – acidosis – ↑ ICF H+ → K+ moves out to ECF maintains + ion balance Aldosterone; insulin, epinephrine, alkolosis, K+ → into cell Glucagon # entry into cell Glucocorticoids → K+ excretion

Hypokalemia K+ < 3.5 mEq/L ↓ intake, ↑ loss, ↑ entry into cells Manifestations: membrane hyperpolorizations ↓ excitability – weakness, smooth muscle, atrophy, cardiac dysrhythmias (bradycardia…asystole)

Hyperkalemia K+ > 5.0 mEq/L – rare ↑ shift from ICF (acidosis), ↓ renal excretion, insulin deficiency or cell trauma

Hyperkalemia Mild attacks Severe attacks ↑ neuromuscular irritability – tingling of lips & fingers, restlessness, intestinal cramps – diarrhea Severe attacks No repolarization → muscle weakness, ↓ tone, flaccid paralysis Cardiac dysrhythmias:”funky chicken” SeeTable 4-6 Clinical Manifestations

Calcium (threshold potential) 99% located in bone – hydroxyapatite Bone, teeth, blood clotting, hormone secretion, cell receptor function Hypo - ↓ block of Na into cell ↑ neuromuscular excitability (muscle cramps) Hyper - ↑ block Na - ↓ neuromuscular excitability (muscle weakness, cardiac arrest, kidney stones, constipation)

Big Picture… Low SERUM K...decreased excitability Nerves & muscles…bradycardia---asystole High SERUM K …increased excitability Cardiac dysrhythmias Low SERUM Ca… increased excitability “Chvostek & Trousseau’s Signs” High SERUM Ca… decreased excitability Big Picture…

Acid-Base Balance Hydrogen ion and pH

pH (0 to 14) Inverse logarithm of the H+ concentration -0.0000001 mg/L – 1x10 -7 so pH = 7 pH = power of hydrogen pH changes by one unit (7 → 6) [H+] 10 fold Biological fluids pH < 7.4 = acidic > 7.4 = basic ( 7.35-7.45)

pH Acids are formed as end products of protein, carbohydrate and fat metabolism Narrow “life range” – 7.35 – 7.45 Bone – lung – kidneys – major regulatory organs “Absolute Range of Life:6.8-7.8” see Table 4-8 pH of body fluids

Volatile H2CO3 (maybe eliminated as CO2) pH Body acids exist in two forms Volatile H2CO3 (maybe eliminated as CO2) Nonvolatile – eliminated by kidneys sulfuric, phosphoric

Consists of a PAIR of a weak acid and its conjugate base Buffering Systems Buffer is a chemical that binds XS H+ or OH- without a significant change in pH Consists of a PAIR of a weak acid and its conjugate base Most important plasma buffering system Carbonic acid – bicarbonate system Hemoglobin (intracellular)

Correction – buffer pairs → Buffering Systems H2O + CO2 H2CO3 H+ + HCO3- 1 20 Lung Kidney Phosphate- HPO4 Ammonia – NH3 Compensation Respiratory - ↑ or ↓ CO2 Renal - ↑ or ↓ acid/alkaline urine Correction – buffer pairs →

Other Buffering Systems Proteins: - charge, mostly intracellular Hemoglobin – H + Hb → HHb + CO2 → HHbCO2 (weak acid)

Buffer Systems Rate of Reaction Bicarbonate system: instantaneously Lungs: minutes to hours Kidneys: hours to days Buffer Systems Rate of Reaction

Respiratory acidosis - ↑ PaCO2 Respiratory alkalosis - ↓ PaCO2 Acidosis and Alkalosis Four categories Respiratory acidosis - ↑ PaCO2 Respiratory alkalosis - ↓ PaCO2 Metabolic acidosis - ↓ HCO3- or↑ other acids Metabolic alkalosis - ↑ HCO3- (XS loss acids)

Normal Values pO2 = 80 to 100 mmHg pCO2 = 35 – 45 mmHg pH = 7.35 – 7.45 pO2 = 80 to 100 mmHg pCO2 = 35 – 45 mmHg HCO3 = 22-26 mEq/L SaO2 = > 92% - here

Patient ABG: pH = 7. 3 pCO2 = 40 mmHg pO2 = 70 mmHg HCO3 = 20 mEq/L 1 Patient ABG: pH = 7.3 pCO2 = 40 mmHg pO2 = 70 mmHg HCO3 = 20 mEq/L 1. pH = ? → acidosis 2. pCO2 = ? → normal 3. HCO3 = ? → low 4. pO2 = ? → low

Must know this… PaCO2: basic <(35-45mmHg) >acidotic HCO3: acidotic < (22-26mEq/L) >basic Must know this…

ABG’s - Compensation Patient pH = 7.30 1. pH = acidotic PCO2 = 30mm Hg 2. PCO2 = alkalotic PO2 = 68mm Hg 3. PO2 = hypoxic HCO3 = 14mEq/L 4. HCO3 = acidotic O2 sat. = 92% 5. O2 sat = low “same directions = compensation” Metabolic acidosis with partial respiratory compensation ABG’s - Compensation

Big Picture ACIDOSIS: CNS depression ALKYLOSIS: CNS irritability Stupor to confusion to coma ALKYLOSIS: CNS irritability Restlessness to seizures Big Picture

Brittany Murphy Died : Community acquired pneumonia, Anemia, Drug Intoxication Brittany Murphy