LPN-CLPN-C

Unit ThreeFluids and Electrolytes

Why are fluids and Why are fluids and electrolytes important for electrolytes important for the nurse to understand?the nurse to understand?

Fluids and electrolytes are essential to identifying and defining the problem◦What is the relationship to the disease process

◦What intervention is appropriate◦How will the intervention affect the patient◦Safety management of infusion therapy

What is the IV infusion order Why was it ordered

◦Continual assessment and evaluation of patient progress, status of labs, response to treatment

Electrolyte imbalances can occur suddenly◦Must be able to assess changes◦Intervene appropriately and in a timely manner

◦Frequent review of lab values, diagnostic tests, medications, IV fluid orders

Homeostasis = a dynamic process involving a continuous series of self-regulating adjustments to maintain a balance of the internal environment◦Preserved through the intake and output of water

◦Water is the primary chemical component within the body, and an individual can perceive a need for it

FluidsFluids

WaterWaterIndividuals with lean tissue mass have a

higher percentage of body water than those with more fat

The average adult female holds 52% of water by weight

The average adult male holds 63% of water by weight

Water serves as a vehicle for the delivery of electrolytes and nutrients to body cells

Water serves as a vehicle for the excretion of waste products

Water is a medium for biochemical reactions

Water contributes to temperature regulation

Water cushions organs and joints

Water IntakeWater IntakeThe need for water is signaled through the mechanism of thirst◦Osmotic pressure from extracellular fluids

◦Thirst center in the hypothalamusPercentages of daily water intake◦60% water from drinking◦30% water from moist foods◦10% water from metabolism processes

Water OutputWater OutputThere are 4 avenues for daily water loss◦Lungs◦Skin◦Urine◦Feces

The route of water loss depends on◦Temperature

When the temperature outside is high, water loss via the skin and lungs increases

◦Humidity◦Physical exercise

Water BalanceWater BalanceUrine output increases when water intake increases

Urine volume decreases when water intake decreases, or when the body loses excessive water

Water balance occurs when water intake equals water output

Regulation of water balance◦Neurosecretions of the hypothalamus (antidiuretic hormone, or ADH/vasopressin)

◦Mineralocorticoid secreted from the adrenal cortex (Aldosterone)

Antidiuretic Hormone (ADH)Antidiuretic Hormone (ADH)ADH is produced by the

hypothalamusRegulates water output by regulating

extracellular fluid osmolarityActs directly on the collecting ducts

and tubules of the nephrons in the kidneys to bring about water reabsorption

ADH↓

Secreted by the posterior lobe of the pituitary gland

↓Regulates water retention and

excretion

ADH (cont’d)ADH (cont’d)Hypertonic extracellular fluid –

Excess sodium or decreased blood volume

↓Release of ADH

↓Sensation of thirst and

conservation of water in the body through reabsorption

ADH (cont’d)ADH (cont’d)Hypotonic extracellular fluid –

Increased blood volume↓

Pituitary signaled to inhibit the release of ADH

↓Stimulates the excretion of

urine↓

Increases the concentration of extracellular fluid

ADH (cont’d)ADH (cont’d)Release of ADH can be influenced by drugs◦Increase of ADH

Nicotine Morphine Barbiturates

◦Inhibition of ADH Alcohol

Malfunctions of the ADH system◦Diabetes insipidus◦Syndrome of inappropriate ADH (SIADH)

Diabetes Insipidus --Diabetes Insipidus --Pituitary gland is unable to secrete ADH

Not common (only 1 in 25,000 affected)◦Head trauma◦Surgery to the region of the pituitary and/or hypothalamus

Urine is excessive and diluted◦Polyuria (urine output of 3-18 L/day)◦Polydipsia

Hallmark signs include urine specific gravity at ≤ 1.005 and urine osmolality at <200/kg

Treated with synthetic vasopressin PO or intranasal (desmopressin or DDAVP)

Syndrome of Inappropriate Syndrome of Inappropriate ADH (SIADH) --ADH (SIADH) --Continued secretion of ADHUrine is concentrated and diminished

Hyponatremia (<135 mEq/L)Increased urine sodium concentration (>20 mEq/L)

Hypotonicity◦Plasma osmolality at <280/kg

Water retention with increased extracellular fluid

Closely monitor for weight change, fluid imbalance, restlessness, CHF, convulsions

Treated with Lasix to maintain urine output and block secretion of ADH

SIADH (cont’d) --SIADH (cont’d) --Most common cause is idiopathicOther causes include

◦Problems with the brain or head Trauma, hemorrhage Tumor, abscess Hydrocephalus, encephalitis Meningitis

◦Medications Antibiotics, oral hypoglycemics, thiazide

diuretics◦Stroke◦Respiratory issues

Asthma, COPD, pneumonia Neonatal hypoxia Lung cancer, tuberculosis

AldosteroneAldosteroneRegulates extracellular fluid volume

◦Maintains water balance through sodium reabsorption in the nephrons

◦Causes sodium retention (and subsequent water retention) if renal blood flow decreased

Decrease in sodium level or extracellular fluid volume

↓Secretion of Aldosterone

↓Kidney reabsorption of water and

sodium↓

Increase in extracellular fluid

Water DistributionWater DistributionThe total volume of water in the body

is distributed among two large compartments, which are separated by a selectively permeable cell membrane◦Intracellular compartment◦Extracellular compartment

Nurses must understand the differences between these two compartments, and know how various illnesses and diseases can bring about imbalances

Intracellular fluid is fluid that is contained within the cells of the body, and comprises 2/3 of the body’s total fluids

Water Distribution (cont’d)Water Distribution (cont’d)Extracellular fluid is found outside

the cells◦Comprises 1/3 of total body fluids◦High in oxygen and carbon dioxide◦Contains essential substances

Glucose for energy supply Amino acids and fatty acids for growth,

repair, and health maintenance Sodium, calcium, chloride, and bicarbonate

◦Transports cholesterol, urea, lactate, creatinine, and sulfates

◦Constant movement within the systemic circulation

◦Main function is to maintain cell membrane permeability and to serve as a vehicle for movement of life-sustaining substances

Extracellular FluidExtracellular FluidThe extracellular fluid compartment is subdivided in three components◦Intravascular = contained within the blood vessels

◦Interstitial = the solution that exists in the small spaces and gaps between body structures, cells, and tissues

◦Transcellular = smallest amount of solution; includes mucus, ocular fluid, sweat, secretions of the genitourinary system, cerebral spinal fluid, pleural solution, pericardial fluid, and peritoneal secretions; separated from other fluid by the epithelial lining or other membranes

Extracellular Fluid (cont’d)Extracellular Fluid (cont’d)The maintenance of the proportional distribution of the extracellular fluid among these three spaces depends on a variety of factors◦Protein content of the blood

Albumin pulls fluid toward itself

◦Integrity of the vascular endothelium

◦Hydrostatic pressure inside the vessels Tends to force fluid out of the vessels

Composition of Body FluidsComposition of Body FluidsSolvent = able to hold substances and act to dissolve them◦Water is a solvent, and is the main constituent of all body fluids

Solute = a substance that is dissolved in the solvent; two major categories◦Electrolytes◦Nonelectrolytes

Solution = the combination of a solvent and a solute

ElectrolytesElectrolytes

ElectrolytesElectrolytesElectrolytes comprise 95% of the body’s solute molecules

Electrolytes are chemicals that carry an electric charge (ions)

Ions converts a solution into a product capable of conducting electricity

Anions = ions with a negative chargeCations = ions with a positive chargeElectrolytes are expressed in milliequivalents per liter (mEq/L)

Electrolytes are crucial to the distribution and movement of water

Electrolytes (cont’d)Electrolytes (cont’d)Electrolytes are needed for the maintenance of acid-base balance

Electrolytes are needed to carry out cellular reactions

Electrolytes are necessary for the transmission of electrochemical impulses in muscles and nerve fibers

Major AnionsMajor AnionsBicarbonate (HCO3)

◦Most present in the extracellular fluid at 24mEq/L

◦Helps in acid-base balance

Major Anions (cont’d)Major Anions (cont’d)Chloride (Cl-)

◦Most present in the extracellular fluid at 105mEq/L

◦Aids in fluid balance and osmotic pressure

Phosphate (PO4)◦Most present in the intracellular fluid at 149mEq/L

◦Aids in energy storageSulfate (SO4)

◦Most present in the intracellular fluid at variable amounts

◦Assists in protein metabolism

Major CationsMajor CationsSodium (Na+)

◦Most present in the extracellular fluid at 142mEq/L

◦Assists with fluid balance and osmotic pressure

Calcium (Ca+)◦Most present in the intracellular fluid at variable amounts

◦Responsible for bone growth and assists in blood clotting

Magnesium (Mg+)◦Most present in the intracellular fluid at 123mEq/L

◦Assists in enzyme production

Major Cations (cont’d)Major Cations (cont’d)Potassium (K+)

◦Most present in the intracellular fluid at 100mEq/L

◦Responsible for neuromuscular excitability

◦Helps with acid-base balance

Fluid and Electrolyte Fluid and Electrolyte MovementMovementPassive transport = noncarrier-

mediated transportation◦Movement of solutes through membranes without the expenditure of energy

◦Types of passive transport – Passive diffusion Facilitated diffusion Filtration Osmosis

Active transport = the use of energy to move molecules◦Moves substances against the concentration gradient from low to high concentration areas

Passive TransportPassive TransportPassive diffusion = the process in which ions, water, and lipid-soluble molecules move randomly in all directions from an area of high concentration to an area of lower concentration through pores in the membrane resulting in even distribution of particles in the fluid◦Particles must besmall enough to passthrough the pores inthe membrane

Passive Transport (cont’d)Passive Transport (cont’d)Passive diffusion (cont’d) –

◦If molecules become more populous in one area of the solution compared to another, a concentration difference or concentration gradient results, and the particles will redistribute themselves until they reach a state of equilibrium

◦An example of this is a metabolic activity that consumes oxygen Causes the diffusion of oxygen from high

to lower concentration in the alveoli Reduces the concentration of oxygen in

the bloodstream Allows oxygen to be replenished

Passive Transport (cont’d)Passive Transport (cont’d)Facilitated diffusion = diffusion across a membrane that is enhanced by a transport protein in the membrane◦The transport protein is specific to the substance that is being transported

◦Glucose is transported in this way

Passive Transport (cont’d)Passive Transport (cont’d)Filtration = pressure causes water, ions, and molecules to move from an area of higher pressure to an area of lower pressure◦Movement is one-directional◦The size of the openings in the membrane determine the size of the particle that can be filtered

◦Examples include the heart, nephrons in the kidney

Passive Transport (cont’d)Passive Transport (cont’d)Osmosis = the passage of water through a semi-permeable membrane in cells and capillaries; water flows from a dilute solution to a more concentrated solution; once the concentration of solutes are equal on each side of the membrane, the flow of water stops and the solutions are isosmotic to each other◦Water molecules are very small◦A membrane that is semi-permeable is more permeable to water due to its size

Passive Transport (cont’d)Passive Transport (cont’d)Osmosis (cont’d) –

◦An isotonic solution is one in which the salt concentration on either side of the membrane is the same

◦A hypertonic solution is one in which the salt concentration in the solution is higher, causing water to leave the cell

◦A hypotonic solution is one in which the salt concentration in the solution is lower, causing water to enter the cell

◦Osmotic pressure is the amount of hydrostatic pressure needed to draw water across the membrane

Passive Transport (cont’d)Passive Transport (cont’d)Osmosis (cont’d) –

◦A solution with higher osmotic pressure compared to another solution is hypertonic with respect to the other

◦If one solution has a lower osmotic pressure compared to another solution, it is hypotonic with respect to the other

◦If two solutions have the same osmotic pressure, they are isotonic with respect to each other

Tonicity refers to the osmotic pressure, or tension, of a solution (impacts cell shrinking or swelling)

http://www.elmhurst.edu/~chm/vchembook/

OsmolalityOsmolalityOsmolality refers to the concentration of a solute per kilogram of solvent◦Measured in weight (kilograms)◦Determination of the total number of particles present in blood, urine, or other fluids

Osmolality is affected by hydration◦Increases with dehydration◦Decreases with overhydration

Types of osmolality tests◦Urine (tests concentrating ability of the kidney)

◦Plasma (used to test electrolyte imbalances)

◦Stool (used to diagnose the cause of diarrhea)

OsmolarityOsmolarityOsmolarity refers to the concentration

of a solute per liter of solution◦Measured in volume (liters) and expressed in milliosmols of solute per liter of solution (mOsm/L)

Serum osmolarity = 290 – 300 mOsm/L◦Refers to the concentration of particles, like sodium, in plasma

Estimated serum osmolarity is 2 times the serum sodium level◦Sodium is the major solute in plasma◦If the sodium level is 145 mEq/L, estimated serum osmolarity would be 290 mOsm/L

Osmolarity of IV SolutionsOsmolarity of IV SolutionsIsotonic solutions

◦250 – 375 mOsm/L◦Have the same osmolarity as normal plasma, so no osmotic pressure difference is created

◦No fluid movement (fluids stay in the extracellular fluid)

◦Useful in hemorrhagic conditions because isotonic solutions expand vascular volume quickly and replace extracellular fluid losses

◦Intracellular and extracellular fluid are isotonic, so red blood cells maintain their concave shape

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)

Isotonic solutions per IV◦0.9% NaCl (Normal saline – NS)

Sodium and chloride in water has the same osmolarity as normal plasma

No calories or free water (water without solute in it)

◦Ringer’s solution Contains sodium, potassium, and calcium No dextrose, magnesium, or bicarbonate No calories or free water

◦Lactated Ringer’s solution (LR) Contains sodium, chloride, potassium,

calcium, and lactate in concentration similar to normal plasma

No dextrose, magnesium No free water

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)Hypotonic solutions

◦<259 mOsm/L◦Lower osmolarity than normal plasma◦Water moves out of the vessels into the dehydrated cell Decreased vascular volume Increased cell water

◦Useful in preventing and treating cellular dehydration by providing free water to cells

◦Never used in acute brain injuries Cerebral cells are very sensitive to free water Absorbed quickly and leads to cerebral

edema◦Hypotonic extracellular fluid (ion concentration is decreased) causes cells to burst

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)Hypotonic solutions per IV

◦5% dextrose in water (D5W) Isotonic in the bag, but hypotonic in the

body Dextrose is rapidly metabolized once infused Leaves free water to shift by osmosis from the vessels into the cells

For each liter of D5W, 2/3 enters the cells, and 1/3 remains in the extracellular space

◦0.45% saline (1/2 NS) and0.224% saline (1/4 NS) Provide free water and small amounts of

sodium and chloride to the cells Half of each liter moves into the cells,

and half remains in the extracellular space

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)

Hypotonic solutions per IV (cont’d) --◦5% dextrose in 0.45% saline (D5 ½ NS) and5% dextrose in 0.225% saline (D5 ¼ NS) Hypertonic in the bag, but hypotonic in

the body Composed of hypotonic saline solutions Amount of dextrose does not meet

daily nutritional requirements, but is enough to help prevent ketosis and starvation

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)Hypertonic solutions

◦≤ 375 mOsm/L◦Higher osmolarity than plasma◦Water moves out of the edematous cell into the vessels Increased vascular volume Decreased cell water

◦Hypertonic extracellular fluid (ion concentration is increased) causes cells to shrink (crenation)

Osmolarity of IV Solutions Osmolarity of IV Solutions (cont’d)(cont’d)Hypertonic solutions per IV

◦Carefully controlled to avoid vascular volume overload and cell dehydration

◦Used to pull excess fluid from the cells and to promote osmotic diuresis

◦Types of hypertonic IV solutions 3% saline 5% saline 10% dextrose 50% dextrose

◦IV pump should always be used to control infusion of hypertonic solutions

◦Frequent monitoring of vital signs, I&O, lung sounds, LOC, and serum sodium levels to avoid hypernatremia and vascular volume overload

Active TransportActive TransportActive transport is necessary to get potassium ions into the cells◦Diffusion can not occur because the concentration of potassium is highest in the cells

Active transport is necessary anytime there is a concentration differential where a substance must move from lower to higher concentration

Adenosine triphosphate (ATP) provides the energy for active transport

Active Transport (cont’d)Active Transport (cont’d)Sodium-potassium pump

◦Most important pump in the body◦Carrier transports sodium out of the cell and pumps potassium into the cell

◦Maintains higher level of potassium in the intracellular fluid

◦Essential for neuron and muscle membranes Electrical polarity must be maintained

for neurons to generate and conduct electrical impulses

Quick Reference forQuick Reference forElectrolyte ImbalancesElectrolyte Imbalances

Sodium (Na+) helps to balance fluid levels in the body and facilitates neuromuscular functioning

Potassium (K+) helps to regulate neuromuscular functioning and osmotic pressure

Calcium (Ca+) affects neuromuscular performance and contributes to skeletal growth and blood coagulation

Magnesium (Mg+) influences muscle contraction and intracellular activity

Chloride (Cl-) regulates blood pressureHydrogen phosphate (HPO4) impacts

metabolism and regulates acid-base balance and calcium levels

Bicarbonate (HCO3) assists in the regulation of pH levels in the blood

SodiumSodiumSodium is a major cation in the extracellular fluid◦Contains 99% of all of the body’s sodium

Sodium is responsible for water balance and determination of plasma osmolality◦The osmolality of both extracellular fluid and intracellular fluid are isotonic

Sodium remains in the extracellular space because it is pumped out of the cells by the sodium-potassium pump

The normal range of sodium =135 – 145 mEq/L

HyponatremiaHyponatremiaSodium level <135mEq/LIndicates there is a greater concentration of water than of sodium, which is a hypervolemic state

Clients at highest risk for hyponatremia are the very young, the elderly, and women

Causes of hyponatremia –◦Abnormal loss of GI secretions

Vomiting, diarrhea Suction drainage Fistulas Excessive tap water enemas

◦Excessive sweating◦Excessive water consumption◦Burns

Hyponatremia (cont’d)Hyponatremia (cont’d)Causes of hyponatremia (cont’d) –

◦Disease states that add to increased extracellular fluid volume CHF SIADH Prolonged use of hypotonic intravenous

therapySigns and symptoms (related to the shift of water into the cells) –◦Cardiovascular

Bounding pulse Tachycardia Hypotension if extracellular fluid volume is

decreased Hypertension if extracellular fluid volume is

increased◦Gastrointestinal

Vomiting Diarrhea

Hyponatremia (cont’d)Hyponatremia (cont’d)Signs and symptoms (cont’d) –

◦Integumentary Decreased extracellular fluid volume =

pale, dry skin; dry mucus membranes Increased extracellular fluid volume =

edema, weight gain◦Renal

Thirst Renal failure

◦Neuromuscular Weakness Headache Confusion Seizures

Nursing interventions –◦Assess vital signs

Hyponatremia (cont’d)Hyponatremia (cont’d)Nursing interventions (cont’d) –

◦Assess mental status; monitor CNS symptoms

◦Monitor ADH levels◦Monitor labs, electrolytes◦Monitor GI losses; perform accurate I&O

◦Obtain daily weightDiagnostics –

◦Plasma level <135mEq/L◦Serum osmolality <270mOsm/kg◦Serum chloride may be decreased◦Decreased BUN and hematocrit

Treatment –◦Intravenous administration of saline solution

◦Diet therapy

Hyponatremia (cont’d)Hyponatremia (cont’d)Treatment (cont’d) –

◦If client with hyponatremia is hypovolemic, treat with NS or LR to correct the extracellular fluid volume deficit

◦If client with hyponatremia is hypervolemic, administer Mannitol

◦Replace sodium slowly Too rapid of a correction in sodium

further compromises the patient’s condition

Hypernatremia may result in brain shrinking

HypernatremiaHypernatremiaElderly clients at risk due to age-related decline in thirst sensitivity

As sodium increases, water is lost◦Water shifts out of cells to establish osmotic equilibrium, causing the brain cells to shrink

Brain cells are very sensitive to changes in sodium levels

Elevated sodium↓

Hypertonicity (stimulates thirst and release of ADH)

↓Body takes in water, which is retained via ADH mechanism

Hypernatremia (cont’d)Hypernatremia (cont’d)Causes of hypernatremia –

◦Decreased fluid intake◦Increased insensible loss of water

Watery diarrhea Osmotic diarrhea (i.e. enteral tube

feedings)◦High sodium diet◦Infusion of sodium-containing fluids◦Administration of hypertonic IV solution (i.e. sodium bicarbonate or 3% saline)

◦Diabetes insipidus Defect in ADH secretion that may cause

sodium retention and increased secretion of dilute urine

◦Head trauma◦High glucose levels

Osmotic diuresis

Hypernatremia (cont’d)Hypernatremia (cont’d)Causes of hypernatremia (cont’d) –◦Over-the-counter medications with high sodium content Alka-Seltzer Cough syrups Aspirin

◦Other medications Prednisone Certain antibiotics

Signs and symptoms –◦Neurological

Progressive lethargy, coma Intracranial bleeding due to brain tissue

shrinkage◦Gastrointestinal

Watery diarrhea Nausea

Hypernatremia (cont’d)Hypernatremia (cont’d)Signs and symptoms (cont’d) –

◦Cardiovascular Tachycardia Hypertension Decreased cardiac contractility

◦Integumentary Dry, sticky mucus membranes Rough, dry tongue Flushed skin

◦Renal Thirst Increased urine output

◦Neuromuscular Twitching, tremors, seizures,

hyperreflexia Agitation, CNS irritability Coma

Hypernatremia (cont’d)Hypernatremia (cont’d)Diagnostics –

◦Sodium plasma level >145mEq/L◦May see an increase in urine output◦Chloride level may be elevated◦Serum osmolality >290mOsm/kg◦Increased BUN, hematocrit

Nursing interventions –◦Assess mental status◦Monitor for CNS changes◦Assess vital signs; assess blood pressure with bounding pulses if client is hypervolemic

◦Monitor labs◦Obtain accurate I&O, daily weight◦Maintain client on seizure precautions

◦Provide a safe environment

Hypernatremia (cont’d)Hypernatremia (cont’d)Treatment –

◦Administer 0.9% NS at a rate to correct hypernatremia but avoid cerebral edema Correction usually occurs within 36-72

hours◦Once volume deficit is restored, administer fluids with D5W

◦Administer hypotonic intravenous fluids if there is fluid loss

◦Administer isotonic IV fluid if there is fluid and sodium loss

◦Restrict sodium intake◦Decrease sodium level slowly as too rapid of a correction may further compromise the patient’s condition Hyponatremia may result in brain

swelling

PotassiumPotassiumNormal serum potassium level =

3.5 – 5.5 mEq/LPotassium is a major cation in the intracellular fluid

Small changes in potassium level have profound effects

Potassium’s role in acid-base balance –◦In alkalotic states, hydrogen moves out of cells to correct high pH; potassium moves in to cells to maintain an electrically stable state

◦In acidosis, the reverse of the above actions occurs

Potassium (cont’d)Potassium (cont’d)Function of potassium

◦Intracellular Controls cellular metabolism Functions in the regulation of

protein/glycogen synthesis

◦Extracellular Maintains action potential in muscles

and neuron cells Assists in controlling cardiac rate and

rhythm, conduction of nerve impulses, skeletal muscle contraction, and function of smooth muscle and endocrine tissues

The body cannot store potassium◦Daily intake of 40 mEq required

Potassium (cont’d)Potassium (cont’d)The sodium-potassium pump controls the concentration of potassium by removing three 3 sodium ions from the cell for every 2 potassium ions that return to the cell

The kidneys eliminate 90% of potassium

The remaining potassium is eliminated through stool and perspiration

An increased level of aldosterone stimulates and increases excretion of potassium

HypokalemiaHypokalemiaSerum potassium level <3.5mEq/LHypokalemia may lead to cardiac and respiratory arrest if not corrected quickly

Causes of hypokalemia –◦Alkalosis

Potassium migrates into the cells as hydrogen ions move out to correct high pH

◦Water intoxication (dilutes serum potassium)

◦Potassium-wasting diuretics◦Excessive loss in GI tract◦Hemodialysis◦NPO status without sufficient IV replacement therapy

◦Malnutrition

Hypokalemia (cont’d)Hypokalemia (cont’d)Hypokalemia enhances the effects of digoxin◦Toxicity may occur at therapeutic levels

Signs and symptoms –◦Cardiovascular

Weak, thready pulse Pedal pulses that are difficult to palpate PVCs Heart block Orthostatic hypotension ECG changes

S-T segment depression Flattened T wave Appearance of a U wave

◦Polyuria

Hypokalemia (cont’d)Hypokalemia (cont’d)Signs and symptoms (cont’d) –

◦Respiratory Decreased breath sounds Shallow respirations Dyspnea

◦Gastrointestinal Abdominal distention Hypoactive bowel sounds Nausea/vomiting Constipation Paralytic ileus

◦Neurological Anxiety Confusion Lethargy, coma

Hypokalemia (cont’d)Hypokalemia (cont’d)Signs and symptoms (cont’d) –

◦Neuromuscular Decreased deep tendon reflexes Muscle weakness/weak hand grasps Leg cramps

Nursing interventions –◦Monitor vital signs◦Monitor serum potassium levels◦Assess heart rate and rhythm◦Assess ECG changes◦Assess respiratory rate, depth, and pattern

◦Protect patient from injury◦Monitor I&O◦Monitor for signs of metabolic alkalosis

Hypokalemia (cont’d)Hypokalemia (cont’d)Nursing interventions (cont’d) –

◦Administer potassium supplements as ordered

◦Assess mental statusTreated with oral or intravenous potassium replacement◦Never administer potassium by IV push or IM as this can lead to fatal arrhythmias

◦Always use an IV pump for parenteral potassium administration

◦Observe infusion site frequently for infiltration, phlebitis

◦Always verify the dosage of potassium in the intravenous solution before hanging

◦Ensure the diluent is dextrose-free to prevent release of insulin

Hypokalemia (cont’d)Hypokalemia (cont’d)Treatment (cont’d) –

◦Do not exceed safe administration rate Potassium infusion per peripheral IV

should not be infused more quickly than 20mEq/hour

Potassium infusion per central line should not be infused in concentrations greater than 40mEq

◦If more than 20mEq/hour given, perform continuous ECG monitoring and check serum potassium levels every 4 – 6 hours until normal

HyperkalemiaHyperkalemiaSerum potassium level >5.0mEq/LPotassium moves from the extracellular fluid to the intracellular fluid

The myocardium is most sensitive to an increase in potassium levels

Changes in the T wave (tall, peaked, or tented) provides the earliest indication that the patient has a high serum potassium level

Causes of hyperkalemia –◦Rapid infusion of IV potassium◦Renal failure◦Adrenal insufficiency◦Acidosis

Hyperkalemia (cont’d)Hyperkalemia (cont’d)Causes of hyperkalemia (cont’d) –◦Addison’s disease

Decreased aldosterone leads to sodium depletion and potassium retention

◦Medications Potassium-sparing diuretics Ace inhibitors

◦GI bleed◦Trauma or ischemia

Massive cell damage Burns

Signs and symptoms –◦Neuromuscular

Muscle twitching Paralysis of the arms and legs

Hyperkalemia (cont’d)Hyperkalemia (cont’d)Signs and symptoms (cont’d) –

◦Cardiovascular Slow, irregular heart rate Decreased blood pressure ECG changes

◦Gastrointestinal Hypermotility/diarrhea Nausea Abdominal cramping Hyperactive bowel sounds

◦Respiratory Unaffected until serum potassium level

is extremely high Respiratory failure due to muscle

weakness

Hyperkalemia (cont’d)Hyperkalemia (cont’d)Nursing interventions –

◦Monitor potassium levels◦Monitor for ECG changes◦Monitor I&O

Adequate renal function is important for the excretion of potassium

◦Assess for signs of metabolic acidosis◦Monitor ABGs

Hyperkalemia frequently seen with acidotic state, though it often resolves when pH is corrected

◦Monitor labs If dehydration is causing hyperkalemia,

hematocrit, hemoglobin, and sodium should be elevated

If condition is associated with renal failure, creatinine and BUN levels should be affected

Hyperkalemia (cont’d)Hyperkalemia (cont’d)Treatment –

◦Discontinue oral and/or IV potassium ◦Promote potassium excretion

Increase urine output Administer potassium-excreting diuretics,

like lasix◦Administer Kayexalate orally or per rectum Exchanges sodium for potassium in the GI

tract and excretes potassium in the stool◦Administer insulin and dextrose to shift potassium from the extracellular fluid to the intracellular fluid

◦Dialysis if hyperkalemia is severe◦Administer calcium gluconate IV

Does not promote potassium loss, but decreases myocardial irritability

Hyperkalemia (cont’d)Hyperkalemia (cont’d)Treatment (cont’d) –

◦Administer sodium bicarbonate Makes cells more alkaline, which shifts

potassium back into the cells

CalciumCalciumCalcium is a major cation in the

body’s extracellular fluidCalcium is stored in the hard bonesCalcium concentration is

maintained by the calcium pump, which moves calcium in and out of cells

Normal serum calcium levels =8.5 – 10.5 mg/dL

Changes in serum protein (especially albumin) causes changes in calcium level because calcium binds to protein

An increase in calcium causes a decrease in phosphorus

Calcium (cont’d)Calcium (cont’d)Parathyroid hormone

◦Responsible for the transfer of calcium from bone to plasma

◦Aids in intestinal absorption◦Enhances renal calcium reabsorption

Calcium, along with phosphorus, enhances bone strength and durability

Calcium helps to maintain cell membrane structure, function, and permeability

Calcium affects activation, excitation, and contraction of cardiac and skeletal muscle

Calcium helps to activate specific steps in blood coagulation

Calcium (cont’d)Calcium (cont’d)Calcium assists in the regulation of the acid-base balance

Calcium plays a major role in nerve impulse transmission because it determines the speed of ionic refluxes through nerve membranes

HypocalcemiaHypocalcemiaCalcium level < 8.5mg/dLThe most common cause of hypocalcemia is inadequate secretion of parathyroid hormone caused by hypoparathyroidism

Other causes –◦Diarrhea◦Wound exudate◦Acute pancreatitis◦Vitamin D deficiency

Signs and symptoms –◦Cardiovascular

Decreased blood pressure ECG changes with prolonged QT interval Cardiac arrest

Hypocalcemia (cont’d)Hypocalcemia (cont’d)Signs and symptoms (cont’d) –

◦Respiratory Laryngospasm

◦Renal failure◦Gastrointestinal

Hyperactive bowel sounds Diarrhea Intestinal cramps

◦Musculoskeletal Muscle cramps of the face and/or

extremities Bone fractures due to demineralization

and/or osteoporosis◦Neurological

Increased irritability, mental changes Seizures

Hypocalcemia (cont’d)Hypocalcemia (cont’d)Signs and symptoms (cont’d) –

◦Neuromuscular Paresthesias/numbness and tingling in

the hands and feet Hyperactive deep tendon reflexes Tetany

Positive Trousseau’s sign Positive Chvostek’s sign

◦Other signs and symptoms of hypocalcemia Dry, brittle nails Dry hair Bone pain Increased bruising

Nursing interventions –◦Seizure precautions

Hypocalcemia (cont’d)Hypocalcemia (cont’d)Nursing interventions (cont’d) –

◦Assess for Trousseau’s and Chvostek’s signs

◦Assess vital signs, bowel sounds◦Provide foods high in calcium◦Monitor calcium labs, ECG◦Assess for musculoskeletal injury

Treatment –◦Administer calcium gluconate orally or by IV

◦Intravenous calcium is 10% calcium gluconate administered by slow IV push Rapid administration can result in bradycardia

or cardiac arrest Monitor IV site Monitor for signs and symptoms of

hypercalcemia

HypercalcemiaHypercalcemiaHypercalcemia results from excessive release of calcium from the bones

Causes◦Metastatic cancer◦Hyperparathyroidism◦Hyperthyroidism

Excessive bone reabsorption

◦Thiazide diuretics◦Excessive calcium intake◦Immobility◦Vitamin D intoxication◦Hypophosphatemia

Hypercalcemia (cont’d)Hypercalcemia (cont’d)Symptoms appear when serum calcium level >12mg/dL

Signs and symptoms –◦Cardiovascular

Hypertension Decreased S-T segments Shortened QT interval Heart block Cardiac arrest

◦Gastrointestinal Hypoactive bowel sounds Constipation Nausea/vomiting

Hypercalcemia (cont’d)Hypercalcemia (cont’d)Signs and symptoms (cont’d) –

◦Renal Polyuria Polydipsia Renal calculi

◦Musculoskeletal Bone fractures/thinning Deep bone pain Decreased muscle tone

◦Neuromuscular Depressed neuromuscular excitability Decreased deep tendon reflexes Impaired memory Lethargy, confusion, coma

Hypercalcemia (cont’d)Hypercalcemia (cont’d)Nursing interventions –

◦Monitor calcium and phosphorus levels

◦ECG monitoring◦Strict I&O; strain urine◦Monitor neurological status◦Assess heart rate and blood pressure◦Assess vital signs, daily weight◦Assess level of consciousness◦Assess bowel sounds

Treatment –◦Administer 0.9% NS to dilute serum calcium and promote renal excretion Hydration at 3,000 – 4,000 mL/day

Hypercalcemia (cont’d)Hypercalcemia (cont’d)Treatment (cont’d) –

◦Administer phosphate orally or per enema

◦Administer loop diuretics (Lasix) to enhance calcium excretion and prevent fluid overload during saline administration

◦Administer corticosteroids to inhibit calcium absorption in the intestine and increase urinary excretion of calcium

◦Administer calcium binders◦Administer dialysis◦Discontinue oral or intravenous calcium-containing drugs (i.e. antacids)

MagnesiumMagnesiumNormal magnesium levels =

1.4 – 2.1 mEq/LUses for magnesium

◦Enzyme action (needed in at least 300 reactions)

◦Regulation of neuromuscular activity

◦Skeletal muscle relaxation following contraction

◦Powers the sodium/potassium pump

◦Necessary for maintaining normal heart rhythm

◦Relaxes the lung muscles responsible for opening the airways

HypomagnesemiaHypomagnesemiaMagnesium level <1.4mEq/LThe most common cause for hypomagnesemia is alcoholism

Other causes –◦Altered absorption◦Increased renal loss◦Prolonged IV therapy without a magnesium supplement due to magnesium moving into the cells

◦Vomiting◦Diarrhea

Vitamin D intoxication

Hypomagnesemia (cont’d)Hypomagnesemia (cont’d)Signs and symptoms (detectable when levels drop below 1 mEq/L) –◦Muscle twitching, tremors◦Hyperreactive reflexes◦Laryngeal stridor◦Cardiac dysrhythmias

Supraventricular tachycardia (SVT) Premature ventricular contractions (PVCs) Ventricular fibrillation

◦Increased susceptibility to digoxin toxicity

◦Mood changes◦Nausea/vomiting◦Diarrhea◦Positive Chvostek’s sign◦Similar to s/s associated with hypocalcemia

Hypomagnesemia (cont’d)Hypomagnesemia (cont’d)Treatment –

◦Oral replacement of magnesium◦Continuous IV infusion of magnesium chloride Rapid infusion may result in respiratory

or cardiac arrest, flushing and sweatingDiagnostics –

◦Decreased serum levels of magnesium

◦Increased renal excretion of magnesium

◦Increase in serum calcium◦Blood gases indicate respiratory or metabolic acidosis

HypermagnesemiaHypermagnesemiaMagnesium level >2.1mEq/LThe most common cause of hypermagnesemia is renal failure

Other causes –◦Hyperparathyroidism◦Hyperthyroidism◦Ingestion of medications high in magnesium

Requires emergency treatment◦IV calcium gluconate 10%◦IV diuretics

Hypermagnesemia (cont’d)Hypermagnesemia (cont’d)Signs and symptoms –

◦Flushing◦Sense of skin warmth◦Hypoactive deep tendon reflexes◦Depressed respirations ◦Hypotension◦Cardiac involvement

Bradycardia Heart block Cardiac arrest

◦Increased susceptibility to digoxin toxicity

◦Nausea/vomiting◦Seizures

PhosphorusPhosphorusNormal phosphorus levels =

2.5 – 4.5 mg/dLUses for phosphorus –

◦Metabolism of proteins and fats◦Formation of adenosine triphosphate◦Formation of red blood cell enzymes that aid in oxygen delivery

80% of phosphorus in the body is contained in the bones and teeth

20% of phosphorus is found in the intracellular fluid

Phosphorus has an inverse effect on calcium levels (an increase in one will cause a decrease in the other)

HypophosphatemiaHypophosphatemiaSerum phosphate level <2.5mg/dL

Causes –◦Administration of TPN in the absence of a phosphorus malabsorption syndrome

◦Alcohol withdrawal◦Vomiting◦Chronic diarrhea◦Aluminum-containing antacids◦Diuretics◦Corticosteroids◦Treatment of diabetic ketoacidosis (insulin-containing dextrose causes phosphorus to move into the cells)

Hypophosphatemia (cont’d)Hypophosphatemia (cont’d)Signs and symptoms –

◦Anemia due to increased RBC fragility resulting from low adenosine triphosphate (ATP) levels

◦Bruising due to platelet dysfunction◦Slurred speech◦Confusion, coma◦Tremors, tetany, seizures◦Numbness and tingling of the extremities

◦Muscle weakness, paresthesias◦Chest pain, dysrhythmias due to decreased oxygen availability

◦Increased rate and depth of breathing due to hypoxemia

◦Hypoactive bowel sounds◦Vomiting

Hypophosphatemia (cont’d)Hypophosphatemia (cont’d)Treatment –

◦Oral phosphate supplements for mild deficiency

◦IV phosphorus for severe deficiency; watch for hypocalcemia and/or hyperphosphatemia

◦May be added to TPN◦Hypotension may occur if administered too quickly

◦Watch infusion site for infiltration

HyperphosphatemiaHyperphosphatemiaPhosphate level >4.5mg/dLPhosphate shifts into the

extracellular fluidPrimary cause is renal diseaseSigns and symptoms –

◦Tetany◦Mental changes

Sudden hyperphosphatemia (such as in IV administration of phosphates) may result in hypocalcemia

Treated by promoting phosphorus excretion◦Aluminum-containing antacids bind phosphates in the GI tract

ChlorideChlorideNormal chloride levels in the body =

95 – 108 mEq/LThe primary role of chloride is the regulation of serum osmolarity fluid balance

Chloride is a major anion in extracellular fluid

Chloride has a reciprocal relationship with bicarbonate (HCO3)

Chloride binds with other cations (NaCl, HCL, KCL)

Chloride (cont’d)Chloride (cont’d)Chloride plays an important role in acid-base balance◦Chloride shift = an ionic exchange that occurs within the red blood cells

◦Maintains a 1:20 ratio of carbonic acid and bicarbonate that is essential for pH balance in plasma

HypochloremiaHypochloremiaChloride level <95mEq/LResults from vomiting/diarrhea or prolonged use of D5W intravenous solution

Signs and symptoms –◦Increased muscle excitability◦Tetany◦Decreased respirations

HyperchloremiaHyperchloremiaChloride level >106mEq/LResults from severe dehydration or head trauma

Signs and symptoms –◦Drowsiness, lethargy◦Headache◦Weakness◦Tremors◦Cardiac dysrhythmias

Acid-Base Acid-Base BalanceBalance

What is the Acid-Base What is the Acid-Base Balance?Balance?In order for homeostasis to be

maintained, an equalization must exist between the acidity and alkalinity of body fluids

This equalization is known as the acid-base balance

The acid-base balance is measured using arterial blood gases (ABGs)

The greater the concentration of hydrogen ions, the more acidic a solution becomes◦pH is the concentration of hydrogen (H)◦The greater the concentration of H, the lower the number of pH

Normal ABG ValuesNormal ABG ValuespH = acid/base7.35 – 7.45

PO2 = partial pressure of oxygen80 mmHg – 100 mmHg

SaO2 = oxygen saturation93% – 100%

PCO2 = partial pressure of carbon dioxide35 mmHg – 45 mmHg

HCO3 = bicarbonate22mEq/L – 26mEq/L

pH = Potential of HydrogenpH = Potential of HydrogenThe narrow range of pH balance is accomplished by H+ ion balance◦HCO3 is regulated by the kidneys◦PCO2 is regulated by the lungs

pH of body fluids◦Extracellular fluid = 7.35 - 7.45◦Intracellular fluid = 6.9 - 7.2◦Urine = 6.0◦Gastric secretions = 1.0 - 2.0◦Intestinal secretions = 6.6 - 7.6◦Bile = 5.0 - 6.0

pH is always the product of two components: respiratory and metabolic

Acidosis/AlkalosisAcidosis/AlkalosisAcidosis = pH below 7.35Alkalosis = pH above 7.45Respiratory alkalosis = PCO2 <35

Respiratory acidosis = PCO2 >45

Metabolic acidosis = HCO3 <22mEq/L

Metabolic alkalosis = HCO3 >26mEq/L

Respiratory AcidosisRespiratory AcidosisOccurs in response to hypoventilation◦Respiratory depression◦Inadequate chest expansion◦Airway obstruction◦Interference with alveolar-capillary exchange

◦COPD◦Sedative or barbiturate overdose◦Pneumonia

pH decreases while PCO2 increasesRespiratory distressChange in level of consciousnessTreated by opening airway passages

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Nursing assessment –Cardiovascular

◦Hypotension◦ECG shows peaked T waves, prolonged PR intervals, and widened QRS complexes

◦Peripheral vasodilation with warm, flushed skin

◦Thready, weak pulse◦Tachycardia

Respiratory◦Dyspnea◦Hypoventilation◦Hypoxia

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Nursing assessment (cont’d)

CNS◦Headache◦Muscle twitching◦Seizures◦Altered mental status◦Decrease in LOC◦Drowsiness

Diagnostic findings --pH <7.35PCO2 >45 mmHgHyperkalemia

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Compensation (how the body compensates for respiratory acidosis) –

Rate and depth of respirations increased in order to blow off CO2

Kidneys eliminate hydrogen ions and retain bicarbonate

HCO3 rises when the body is compensating for acidosis

HCO3 increase raises pHTreatment –Treat the underlying causeImprove ventilation (may need a ventilator)

Assess respiratory depth and rate

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Treatment (cont’d)

Pulmonary hygiene◦Clear respiratory tract of mucus

Provide adequate fluids to liquefy secretions

Low flow oxygen for carbon dioxide retention in patients with chronic respiratory acidosis

Position patient to facilitate best lung expansion

Assess apical pulse, color of skin, nail beds, mucus membranes, LOC

Assess for tachycardia or arrhythmias

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Treatment (cont’d)

Monitor arterial blood gases, potassium

Administer medications◦Bronchodilators◦Antibiotics◦Mucomyst to decrease viscosity of pulmonary secretions

Oral hygieneProvide a calm atmosphereKeep siderails up and call light within reach

Orient patient frequently if needed

Respiratory Acidosis (cont’d)Respiratory Acidosis (cont’d)Satisfactory Outcomes --ABGs improved to patient’s baseline

Decreased anxietyImproved breathing with less effort

Freedom from injuryNo cardiac arrhythmiasImproved LOCNormal respiratory rate and depth

Respiratory AlkalosisRespiratory AlkalosisOccurs in response to hyperventilation◦Stress◦Fever◦Pain

pH increases while PCO2 decreasesCaused by infection, incorrect ventilator settings, respiratory center stimulation as a result of fever, salicylate intoxication

Signs and symptoms include headache, dizziness, paresthesias, neuromuscular irritability

Respiratory Alkalosis (cont’d)Respiratory Alkalosis (cont’d)Nursing assessment –Cardiovascular

◦Increased myocardial irritability◦Increased heart rate

Respiratory◦Rapid, shallow breathing◦Chest tightness

CNS◦Dizziness, light-headedness, blurred vision

◦Difficulty concentrating, anxiety, panic◦Numbness and tingling in the extremities◦Hyperactive reflexes, tetany, convulsions

Respiratory Alkalosis (cont’d)Respiratory Alkalosis (cont’d)Diagnostic findings --pH >7.45PCO2 <35 mmHgHypokalemiaHypocalcemiaCompensation –Kidneys conserve hydrogen and excrete bicarbonate

Low HCO3 levels indicates that the body is attempting to compensate

Respiratory Alkalosis (cont’d)Respiratory Alkalosis (cont’d)Treatment –Treat the cause of the conditionAssist patient to breathe more slowly

Use rebreather mask or paper bagAdminister oxygen if patient is hypoxic

Administer anxiolytics if neededProvide emotional supportMonitor patient’s vital signsMonitor patient’s arterial blood gases

Protect patient from injury

Respiratory Alkalosis (cont’d)Respiratory Alkalosis (cont’d)Satisfactory Outcomes --Patient will have a decreased respiratory rate

Patient will have absence of numbness or tingling in the extremities

Normal (or baseline) ABGsPatient will experience diminished anxiety

Patient will be free from injury

Metabolic ImbalanceMetabolic ImbalanceBicarbonate (HCO3) is a direct reflection of the renal system’s ability to compensate for pH changes

Normal HCO3 range is 22 – 26 mEq/LHCO3 level <22 indicates acidosisHCO3 level >26 indicates alkalosisBase Excess is an indication of the amount of HCO3 available in the extracellular fluid

Normal base excess range is -3.0 to +3.0A value >3.0 indicates metabolic alkalosis

A value <3.0 indicates metabolic acidosis

Metabolic AcidosisMetabolic AcidosisCauses --Kidney failureDiabetic ketoacidosisHyperthyroidismTrauma, shockIncreased exerciseSevere infection, feverStarvationMalnutritionChronic diarrhea

Metabolic Acidosis (cont’d)Metabolic Acidosis (cont’d)Nursing assessment –Cardiovascular

◦Peripheral vasodilation◦Hypotension◦Dysrhythmias◦Cold, clammy skin

Respiratory◦Deep, rapid breathing (Kussmaul’s respirations)

CNS◦Drowsiness/lethargy that progresses to coma

◦Headache, confusion◦Weakness

Metabolic Acidosis (cont’d)Metabolic Acidosis (cont’d)Nursing assessment (cont’d)

Gastrointestinal◦Nausea/vomiting◦Diarrhea◦Abdominal pain

Diagnostic findings --pH <7.35HCO3 <22Hyperkalemia

Metabolic Acidosis (cont’d)Metabolic Acidosis (cont’d)Compensation (how the body compensates for metabolic acidosis) –

Lungs eliminate carbon dioxideKidneys conserve bicarbonateTreatment –Treat the underlying causeProvide hydrationMonitor arterial blood gasesMonitor I&O and weightAssess vital signsAssess respiratory rate and depth

Metabolic Acidosis (cont’d)Metabolic Acidosis (cont’d)Treatment (cont’d)

Assess level of consciousnessMonitor GI functionAdminister ECGMay need to administer alkalotic IV solution◦NaHCO3◦Must be administered cautiously due to possibility of metabolic alkalosis and hypokalemia

Metabolic Acidosis (cont’d)Metabolic Acidosis (cont’d)Satisfactory Outcomes --Patient will be free from injuryPatient will experience no dysrhythmias

Normalized ABGsPatient will have no fluid deficits

LOC returns to normalRelief of GI symptoms

Metabolic AlkalosisMetabolic AlkalosisOccurs with loss of hydrogen ions

◦Vomiting◦NG suction

Occurs with increase in HCO3 due to ingestion of bicarbonate-based antacids

Nursing assessment –Cardiovascular

◦Tachycardia, dysrhythmias◦Hypertension

Respiratory◦Hypoventilation◦Respiratory failure

Metabolic Alkalosis (cont’d)Metabolic Alkalosis (cont’d)Nursing assessment (cont’d)

CNS◦Dizziness◦Irritability◦Tremors◦Muscle cramps◦Hyperreflexia◦Paresthesias of the fingers and toes

◦Tetany◦Seizures

Metabolic Alkalosis (cont’d)Metabolic Alkalosis (cont’d)Diagnostic findings --pH >7.45HCO3 >26HypokalemiaHypocalcemia (pH increases calcium binding)

Compensation –Lungs retain carbon dioxideKidneys conserve hydrogen and excrete bicarbonate

PCO2 increases with compensation

Metabolic Alkalosis (cont’d)Metabolic Alkalosis (cont’d)Treatment –Treat underlying causeAssess level of consciousnessAssess vital signsAssess respiratory rate and depth

Administer potassium supplement if needed

Administer ranitidine or famotidine to decrease secretion of hydrogen from GI drainage

Assess I&OAssess arterial blood gasesAssess ECG findings

Metabolic Alkalosis (cont’d)Metabolic Alkalosis (cont’d)Satisfactory Outcomes --Hypertension correctedElectrolytes within normal range

Normalized ABGsNormal ECG

Buffer SystemBuffer SystemBicarbonate –

◦Linked to both the respiratory and renal systems

◦Normal bicarbonate (HCO3) to carbonic acid (H2CO3) ratio is 20:1

◦Ratio changes if pH is increased or decreased

◦Once compensation occurs, the ratio stabilizes

Respiratory –◦The lungs control the respiratory carbonic acid buffer system, but fatigue quickly

◦Respiratory rate and depth adjusted in response to carbon dioxide in the extracellular fluid; quick reaction time

Buffer System (cont’d)Buffer System (cont’d)Renal –

◦The kidneys control the metabolic buffer NaHCO3 (sodium bicarbonate)

◦Excretes acidic or alkaline urine◦Reaction is slow (hours to days)◦More effective than the respiratory buffer system

Review of SimpleReview of SimpleAcid-Base Disturbances --Acid-Base Disturbances --

pH <7.35 = acidosispH >7.45 = alkalosisAbnormal PCO2 = respiratoryAbnormal HCO3 = metabolicIf the patient is acidotic with a PCO2 >45mmHg, the problem is respiratory

If the pt is acidotic with an HCO3 <22mEq/L, the problem is metabolic

If the patient is alkalotic with a PCO2 <35mmHg , the problem is respiratory

If the patient is alkalotic with an HCO3 >26mEq/L, the problem is metabolic

Review of Compensation --Review of Compensation --If both HCO3 and PCO2 are above or below their normal ranges and are shifting in the same direction, the patient’s buffering system is functioning and trying to bring the acid-base balance back to normal

Respiratory Acidosis –◦pH <7.35◦PCO2 >45◦HCO3 elevated with compensation (kidneys eliminate hydrogen and retain bicarbonate)

Respiratory Alkalosis –◦PCO2 <35◦HCO3 decreased with compensation (kidneys conserve hydrogen and excrete bicarbonate)