Fluids and Fluids and Electrolytes,Electrolytes,

Acids and BasesAcids and BasesChapter 4

Distribution of Body FluidsTotal body water – all fluids – 60% weight

(kg)Intracellular fluid (ICF) 40% TBW

Extracellular fluid (ECF) 20% TBWInterstitial fluid – between cellsIntravascular fluid – blood plasmaLymph, 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

Distribution of Body FluidsPediatrics

◦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

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 BalanceSodium (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 BalanceBalance 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 cations135 – 145 mEq/L

Hypernatremia - > 145 mEq/L

Hyponatremia - < 135 mEq/L

Hypernatremia-causes• ↑ Na or ↓ H2O• IV therapy – acidosis (NaHCO3)

Cushing's Syndrome - ↑ ACTH → aldosteronefever, respiratory infection - ↓ H2Odiabetes, 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

HypochloremiaResult of hyponatremia or ↑ HCO3

Vomiting – loss HCl

Cystic fibrosis

Potassium (resting potential)Major intracellular electrolyte98% intracellular – Na – K – ATP Pump3.5 – 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 LevelsChange 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 cellGlucocorticoids → 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)

HyperkalemiaK+ > 5.0 mEq/L – rare

↑ shift from ICF (acidosis), ↓ renal excretion, insulin deficiency or cell trauma

HyperkalemiaMild 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 – hydroxyapatiteBone, 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

Acid-Base BalanceAcid-Base BalanceHydrogen ion and pH

pH (0 to 14)Inverse logarithm of the H+ concentration -

0.0000001 mg/L – 1x10 -7

so pH = 7pH = power of hydrogenpH changes by one unit (7 → 6)

[H+] 10 fold

Biological fluidspH < 7.4 = acidic > 7.4 = basic

( 7.35-7.45)

pHAcids 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

pHBody acids exist in two forms

◦Volatile H2CO3 (maybe eliminated as CO2)

◦Nonvolatile – eliminated by kidneys sulfuric, phosphoric

Buffering SystemsBuffer 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 1. Carbonic acid – bicarbonate system2. Hemoglobin (intracellular)

Buffering SystemsH2O + CO2 H2CO3 H+ + HCO3

-

1 20 Lung

Kidney

Phosphate- HPO4Ammonia –

NH3

Compensation◦Respiratory - ↑ or ↓ CO2

◦Renal - ↑ or ↓ acid/alkaline urine

Correction – buffer pairs →

Other Buffering SystemsProteins: - charge, mostly intracellular

Hemoglobin –

H + Hb → HHb + CO2 → HHbCO2 (weak acid)

Buffer Systems Rate of ReactionBuffer Systems Rate of Reaction

Bicarbonate system: instantaneously

Lungs: minutes to hours

Kidneys: hours to days

Acidosis and AlkalosisFour categories

◦Respiratory acidosis - ↑ PaCO2

◦Respiratory alkalosis - ↓ PaCO2

◦Metabolic acidosis - ↓ HCO3- or↑

other acids

◦Metabolic alkalosis - ↑ HCO3- (XS loss

acids)

Normal Values

pH = 7.35 – 7.45pO2 = 80 to 100 mmHgpCO2 = 35 – 45 mmHgHCO3 = 22-26 mEq/LSaO2 = > 92% - here

PatientABG: pH = 7.3

pCO2 = 40 mmHg pO2 = 70 mmHgHCO3 = 20 mEq/L

1. pH = ? → acidosis 2. pCO2 = ? → normal3. HCO3 = ? → low 4. pO2 = ? → low

Must know this…Must know this…

PaCO2: basic <(35-45mmHg) >acidotic

HCO3: acidotic < (22-26mEq/L)

>basic

ABG’s - CompensationABG’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

Big Picture

ACIDOSIS: CNS depression◦Stupor to confusion to coma

ALKYLOSIS: CNS irritability◦Restlessness to seizures

Brittany Murphy

Died : Community acquired pneumonia,Anemia,Drug Intoxication