Fluids and Electrolytes

MEDICAL-SURGICAL MEDICAL-SURGICAL NURSINGNURSING

Arni A. Magdamo, MD, MHA, MBA, FPCPArni A. Magdamo, MD, MHA, MBA, FPCPHarvard University School of MedicineHarvard University School of Medicine

Massachusetts General Hospital Institute of Health SciencesMassachusetts General Hospital Institute of Health Sciences

Fluids and ElectrolytesFluids and Electrolytes

Water, water everywhere… but not a drop to drink…

WALT WHITMAN

FLUID BALANCEFLUID BALANCE

Water and its electrolytes are distributed in two Water and its electrolytes are distributed in two major compartments:major compartments: 63% of the total body water is found within cells 63% of the total body water is found within cells

across the age groups.across the age groups. 37% of the total body water is found outside the cells, 37% of the total body water is found outside the cells,

mainly in tissue spaces, plasma of blood, and lymph.mainly in tissue spaces, plasma of blood, and lymph.

The intracellular and extracellular fluid The intracellular and extracellular fluid compartments are maintained in a steady state compartments are maintained in a steady state to ensure proper physiologic functioning.to ensure proper physiologic functioning.

FLUID BALANCEFLUID BALANCE

TOTAL BODY WATER (AS PERCENTAGE OF BODY WEIGHT) IN TOTAL BODY WATER (AS PERCENTAGE OF BODY WEIGHT) IN RELATION TO AGE AND SEXRELATION TO AGE AND SEX

AGEAGE MALEMALE FEMALEFEMALE

UNDER 18UNDER 18 65%65% 55%55%

18-4018-40 60%60% 50%50%

40-6040-60 50-60%50-60% 40-50%40-50%

OVER 60OVER 60 50%50% 40%40%

Intracellular Fluid CompartmentIntracellular Fluid Compartment

Includes all the water and electrolytes inside the Includes all the water and electrolytes inside the cells of the body.cells of the body.

Approximately 63% of the total body water is Approximately 63% of the total body water is contained within cell membranes.contained within cell membranes.

Contains high concentrations of potassium, Contains high concentrations of potassium, phosphate, magnesium and sulfate ions, along phosphate, magnesium and sulfate ions, along with most of the proteins in the body.with most of the proteins in the body.


EXAMPLE: How much water is in the intracellular EXAMPLE: How much water is in the intracellular fluid compartment of a 25-year old male patient fluid compartment of a 25-year old male patient who weighs 60 kg?who weighs 60 kg?

Step #1: Compute the total body water (TBW) Step #1: Compute the total body water (TBW) based on age and sex.based on age and sex.

TBW = (60 kg) (0.6)TBW = (60 kg) (0.6)= 36 kg = 36 kg weight of water weight of water= 36 liters = 36 liters volume of water volume of water


Step #2: Compute for the intracellular fluid volume Step #2: Compute for the intracellular fluid volume (usually 63% of the total body water is (usually 63% of the total body water is intracellular fluid)intracellular fluid)

ICF = (36 liters) (0.63)ICF = (36 liters) (0.63)

= 22.7 liters= 22.7 liters

Extracellular Fluid CompartmentExtracellular Fluid Compartment

Includes all the fluid outside the cells: interstitial Includes all the fluid outside the cells: interstitial fluid, plasma, lymph, secretions of glands, fluid fluid, plasma, lymph, secretions of glands, fluid within subcompartments separated by epithelial within subcompartments separated by epithelial membranes.membranes.

Constitutes approximately 37% of the total body Constitutes approximately 37% of the total body water.water.

Contains high concentrations of sodium, chloride Contains high concentrations of sodium, chloride and bicarbonate.and bicarbonate.

One-third of the ECF is in plasma.One-third of the ECF is in plasma.


EXAMPLE: How much water is in the circulatory EXAMPLE: How much water is in the circulatory system of a 32-year old female patient who system of a 32-year old female patient who weighs 52 kg?weighs 52 kg?

Step #1: Compute for the total body water based Step #1: Compute for the total body water based on age and sex.on age and sex.

TBW = (52 kg) (0.5)TBW = (52 kg) (0.5)= 26 kg = 26 kg weight of water weight of water= 26 liters = 26 liters volume of water volume of water


Step #2: Compute for the extracellular fluid Step #2: Compute for the extracellular fluid volume (usually 37% of the total body water).volume (usually 37% of the total body water).

ECF = (26 liters) (0.37)ECF = (26 liters) (0.37)


Step #3: Compute for the plasma volume.Step #3: Compute for the plasma volume.

Plasma = (9.6 liters)/3Plasma = (9.6 liters)/3


Transcellular Exchange Transcellular Exchange Mechanisms:Mechanisms:

ACTIVE TRANSPORTACTIVE TRANSPORT PASSIVE TRANSPORTPASSIVE TRANSPORT

DiffusionDiffusion OsmosisOsmosis FiltrationFiltration Facilitated diffusionFacilitated diffusion

Serum OsmolalitySerum Osmolality

Reflects the amount of solute particles in a Reflects the amount of solute particles in a solution and is a measure of the concentration of solution and is a measure of the concentration of a given solution. a given solution.

Can be calculated using the formula:Can be calculated using the formula:OsmOsmserumserum = 2 (Na) + BUN + glucose = 2 (Na) + BUN + glucose

Normal value = 285 – 295 mosm/kgNormal value = 285 – 295 mosm/kg

Sodium is the most active determinant of serum Sodium is the most active determinant of serum osmolality and is therefore actively moved osmolality and is therefore actively moved across membranes to ensure normal osmolality.across membranes to ensure normal osmolality.

Hence, if too much salt is used in food, the pulse hardens.

HUANG TI (THE YELLOW EMPEROR), 2697-2597 B.C.

IonsIons

NORMAL VALUES AND MASS CONVERSION FACTORSNORMAL VALUES AND MASS CONVERSION FACTORS

Normal Plasma ValuesNormal Plasma Values Mass ConversionMass Conversion

Sodium (NaSodium (Na++)) 135 – 145 meq/L135 – 145 meq/L 23 mg = 1 meq23 mg = 1 meq

Potassium (KPotassium (K++)) 3.5 – 5.0 meq/L3.5 – 5.0 meq/L 39 mg = 1 meq39 mg = 1 meq

Chloride (ClChloride (Cl--)) 98 – 107 meq/L98 – 107 meq/L 35 mg = 1 meq35 mg = 1 meq

Bicarbonate (HCOBicarbonate (HCO33--)) 22 – 26 meq/L22 – 26 meq/L 61 mg = 1 meq61 mg = 1 meq

Calcium (CaCalcium (Ca2+2+)) 8.5 – 10.5 mg/dL8.5 – 10.5 mg/dL 40 mg = 1 mmol40 mg = 1 mmol

PhosphorusPhosphorus 2.5 – 4.5 mg/dL2.5 – 4.5 mg/dL 31 mg = 1 mmol31 mg = 1 mmol

Magnesium (MgMagnesium (Mg2+2+)) 1.8 – 3.0 mg/dL1.8 – 3.0 mg/dL 24 mg = 1 mmol24 mg = 1 mmol

OsmolalityOsmolality 285 – 295 mosm/kg285 – 295 mosm/kg

265 - 305 mosm/kg265 - 305 mosm/kg

--

SodiumSodium

Dominant extracellular ion.Dominant extracellular ion. About 90 to 95% of the osmotic pressure of the About 90 to 95% of the osmotic pressure of the

extracellular fluid results from sodium ions and extracellular fluid results from sodium ions and the negative ions associated with them.the negative ions associated with them.

Recommended dietary intake is less than 2.5 Recommended dietary intake is less than 2.5 grams per day.grams per day.

Kidneys provide the major route by which the Kidneys provide the major route by which the excess sodium ions are excreted.excess sodium ions are excreted.

SodiumSodium

In the presence of In the presence of aldosterone, aldosterone, the reabsorption the reabsorption of sodium ions in the loop of Henle is very of sodium ions in the loop of Henle is very efficient. When efficient. When aldosteronealdosterone is absent, the is absent, the reabsorption of sodium in the nephron is greatly reabsorption of sodium in the nephron is greatly reduced and the amount of sodium lost in the reduced and the amount of sodium lost in the urine increases.urine increases.

Also excreted from the body through the sweat Also excreted from the body through the sweat mechanism.mechanism.

SodiumSodium

Primary mechanisms that regulate the sodium Primary mechanisms that regulate the sodium ion concentration in the extracellular fluid:ion concentration in the extracellular fluid: Changes in the blood pressureChanges in the blood pressure Changes in the osmolality of the extracellular fluidChanges in the osmolality of the extracellular fluid

Sodium RegulationSodium Regulation

NORMAL Na+

INCREASED SODIUM

DECREASED SODIUM

Increased ADH secretion, Decreased urine volume and increased plasma

volume

Decreased aldosterone secretion, decreased sodium reabsorption

DECREASED SODIUM

INCREASED SODIUM

Decreased ADH secretion, Increased urine volume and decreased plasma

volume

Increased aldosterone secretion, increased sodium reabsorption

PotassiumPotassium

Electrically excitable tissue such as muscle and Electrically excitable tissue such as muscle and nerves are highly sensitive to slight changes in nerves are highly sensitive to slight changes in extracellular potassium concentration.extracellular potassium concentration.

The ECF concentration of potassium must be The ECF concentration of potassium must be maintained within a narrow range for tissues to maintained within a narrow range for tissues to function normally.function normally.

PotassiumPotassium

AldosteroneAldosterone also plays a major role in regulating also plays a major role in regulating the concentration of potassium ions in the ECF.the concentration of potassium ions in the ECF.

Circulatory system shock resulting from plasma Circulatory system shock resulting from plasma loss, dehydration, and tissue damage causes loss, dehydration, and tissue damage causes extracellular potassium ions to become more extracellular potassium ions to become more concentrated than normal. In response, concentrated than normal. In response, aldosterone secretion increases and causes aldosterone secretion increases and causes potassium secretion to increase.potassium secretion to increase.

Potassium RegulationPotassium Regulation

NORMAL K+

INCREASED POTASSIUM

DECREASED POTASSIUM

Increased aldosterone secretion with increased potassium secretion by the kidneys and increased potassium in

urine

DECREASED POTASSIUM

INCREASED POTASSIUM

Decreased aldosterone secretion with decreased potassium secretion by the

kidney and decreased potassium in the urine

CalciumCalcium

Extracellular concentration of calcium ions is Extracellular concentration of calcium ions is maintained within a narrow range.maintained within a narrow range.

Increases and decreases in ECF concentration Increases and decreases in ECF concentration of calcium ions have dramatic effects on the of calcium ions have dramatic effects on the electrical properties of excitable tissues.electrical properties of excitable tissues.

Parathyroid hormone (PTH) secreted by the Parathyroid hormone (PTH) secreted by the parathyroid glands increases extracellular parathyroid glands increases extracellular calcium levels. calcium levels.

CalciumCalcium

Calcitonin is secreted by the thyroid gland. Calcitonin is secreted by the thyroid gland. It reduces blood levels of calcium when they are It reduces blood levels of calcium when they are

too high. too high.

Calcium RegulationCalcium Regulation

NORMAL Ca++

INCREASED CALCIUM

DECREASED CALCIUM

Increased Calcitonin secretion with decreased bone resorption

Decreased parathyroid hormone secretion with decreased bone resorption, decreased intestinal

calcium absorption, and decreased kidney calcium reabsorption

DECREASED CALCIUM

INCREASEDCALCIUMIncreased parathyroid hormone

secretion with increased bone resorption, increased intestinal

calcium absorption, and increased renal calcium reabsorption

Phosphate and Sulfate Phosphate and Sulfate

Phosphate and sulfate are reabsorbed by active Phosphate and sulfate are reabsorbed by active transport in the kidneys.transport in the kidneys.

Rate of reabsorption is slow, so that if the Rate of reabsorption is slow, so that if the concentration of these ions in the filtrate concentration of these ions in the filtrate exceeds the ability of the nephron to reabsorb exceeds the ability of the nephron to reabsorb them, the excess is excreted in the urine.them, the excess is excreted in the urine.

Fluid and Electrolyte Fluid and Electrolyte ManagementManagement

General Management of FluidsGeneral Management of Fluids

Maintenance Therapy:Maintenance Therapy:Minimum Water RequirementsMinimum Water Requirements

Can be estimated from the sum of the urine output Can be estimated from the sum of the urine output necessary to excrete the daily solute load (500 mL necessary to excrete the daily solute load (500 mL per day if the urine concentrating ability is normal) per day if the urine concentrating ability is normal) plus the insensible water losses from the skin and plus the insensible water losses from the skin and respiratory system (500 to 1000 mL per day), respiratory system (500 to 1000 mL per day), minus the amount of water produced from minus the amount of water produced from endogenous metabolism (300 mL per day)endogenous metabolism (300 mL per day)

Two to three liters of water are needed to produce Two to three liters of water are needed to produce a urine volume of 1 to 1.5 liters daily.a urine volume of 1 to 1.5 liters daily.

Fluid / Electrolyte Replacement:Fluid / Electrolyte Replacement:Insensible Water LossesInsensible Water Losses

Usually average 500 to 1000 mL daily, and Usually average 500 to 1000 mL daily, and depend on respiratory rate, ambient temperature, depend on respiratory rate, ambient temperature, humidity and body temperature.humidity and body temperature.

Water losses increase by 100 ml daily for each Water losses increase by 100 ml daily for each degree of body temperature over 37degree of body temperature over 37°C.°C.

Fluid losses from sweating can vary enormously Fluid losses from sweating can vary enormously and depend on physical activity and body and and depend on physical activity and body and ambient temperature.ambient temperature.

Mechanical ventilation accentuate losses from the Mechanical ventilation accentuate losses from the respiratory tract.respiratory tract.


A 72-year old female was admitted for pneumonia in A 72-year old female was admitted for pneumonia in the elderly, community-acquired.the elderly, community-acquired.

Previous day’s profile:Previous day’s profile:Total urine output: 1,700 mlTotal urine output: 1,700 ml3 episodes of loose stools, approximately 250 per 3 episodes of loose stools, approximately 250 per episodeepisodeHighest temperature: 39.7 degrees CelsiusHighest temperature: 39.7 degrees CelsiusOn mechanical ventilator for the past three daysOn mechanical ventilator for the past three days


Today’s Orders:Today’s Orders:NGT feeding with the following:NGT feeding with the following:

TCR: 1700 kcal/dayTCR: 1700 kcal/day6 equal feedings, 2:1 dilution6 equal feedings, 2:1 dilutionFlush with 100 ml plain water after every Flush with 100 ml plain water after every feedingfeeding

Compute for the IVF rate for today if the patient is to Compute for the IVF rate for today if the patient is to be connected to an adult venoset.be connected to an adult venoset.

What would be your choice of IVF?What would be your choice of IVF?

Maintenance Therapy:Maintenance Therapy:Minimum Water RequirementsMinimum Water Requirements

Weighing the patient daily is the best means of Weighing the patient daily is the best means of assessing net gain or loss of fluid, since the assessing net gain or loss of fluid, since the gastrointestinal, renal and insensible fluid losses gastrointestinal, renal and insensible fluid losses of the hospitalized patient are unpredictable.of the hospitalized patient are unpredictable.

ECF Volume DepletionECF Volume Depletion

Occurs with losses of both sodium and water.Occurs with losses of both sodium and water. The character of the fluid loss will dictate the The character of the fluid loss will dictate the

clinical picture. If the loss is isotonic, the clinical picture. If the loss is isotonic, the osmolality is unaffected and intracellular volume osmolality is unaffected and intracellular volume will change minimally.will change minimally.

Loss of hypotonic fluid will lead to an increase in Loss of hypotonic fluid will lead to an increase in serum or plasma osmolality.serum or plasma osmolality.


Manifestations of ECF volume depletion depend Manifestations of ECF volume depletion depend on the magnitude and on serum osmolality.on the magnitude and on serum osmolality.

Symptoms:Symptoms: AnorexiaAnorexia NauseaNausea VomitingVomiting ApathyApathy WeaknessWeakness Orthostatic lightheadednessOrthostatic lightheadedness SyncopeSyncope


Weight loss is an important sign and provides an Weight loss is an important sign and provides an estimate of the magnitude of the volume deficit.estimate of the magnitude of the volume deficit.

Other physical findings:Other physical findings: Orthostatic hypotensionOrthostatic hypotension Poor skin turgorPoor skin turgor Sunken eyesSunken eyes Absence of axillary sweatAbsence of axillary sweat OliguriaOliguria TachycardiaTachycardia Shock and coma (severe volume depletion)Shock and coma (severe volume depletion)


Causes of ECF volume depletion:Causes of ECF volume depletion: Gastrointestinal lossesGastrointestinal losses DiureticsDiuretics Renal or adrenal diseaseRenal or adrenal disease Blood lossBlood loss Sequestration of fluidSequestration of fluid

ECF Volume Depletion: ECF Volume Depletion: TreatmentTreatment

Should be directed at restoration of the ECF Should be directed at restoration of the ECF volume with solutions containing the lost water volume with solutions containing the lost water and electrolytes.and electrolytes.

Daily assessment of weight, ongoing fluid losses Daily assessment of weight, ongoing fluid losses and serum electrolyte concentrations.and serum electrolyte concentrations.

Mild degrees of volume depletion can be corrected Mild degrees of volume depletion can be corrected orally.orally.

ECF Volume Depletion: ECF Volume Depletion: TreatmentTreatment

More severe deficits accompanied by circulatory More severe deficits accompanied by circulatory compromise should be treated initially through compromise should be treated initially through intravenous isotonic fluid replacement until intravenous isotonic fluid replacement until hemodynamic stability has been restored. hemodynamic stability has been restored. One to One to two liters of fluid should be given over the first two liters of fluid should be given over the first hour.hour.

Further therapy should be guided by the Further therapy should be guided by the symptoms and signs.symptoms and signs.

Parenteral SolutionsParenteral Solutions

COMMONLY USED PARENTERAL SOLUTIONSCOMMONLY USED PARENTERAL SOLUTIONS

IV SolutionsIV Solutions OsmolalityOsmolality

(mosm/kg)(mosm/kg)

GlucoseGlucose

(g/liter)(g/liter)

SodiumSodium

(meq/liter)(meq/liter)

ChlorideChloride

(meq/liter)(meq/liter)

5% D/W5% D/W 252252 5050 -- --

10% D/W10% D/W 505505 100100 -- --

50% D/W50% D/W 25252525 500500 -- --

0.45% NaCl0.45% NaCl 154154 -- 7777 7777

0.9% NaCl0.9% NaCl 308308 -- 154154 154154

3% NaCl3% NaCl 10261026 -- 513513 513513

Ringer’s lactateRinger’s lactate 282282 -- 130130 109109

5% D/NR5% D/NR 294294 5050 147147 147147

5% D/NM5% D/NM 290290 5050 7777 7777

ECF Volume ExcessECF Volume Excess

Manifestations:Manifestations: Weight gain is the most sensitive and consistent sign of Weight gain is the most sensitive and consistent sign of

ECF volume excess.ECF volume excess. Edema is usually not apparent until 2 to 4 kg of fluid Edema is usually not apparent until 2 to 4 kg of fluid

have been retained.have been retained. DyspneaDyspnea TachycardiaTachycardia Jugular venous distentionJugular venous distention Hepatojugular refluxHepatojugular reflux Rales on pulmonary auscultationRales on pulmonary auscultation

ECF Volume ExcessECF Volume Excess

Causes:Causes: Heart, liver or renal failureHeart, liver or renal failure Excessive renal sodium and water retentionExcessive renal sodium and water retention Unnecessary salt administrationUnnecessary salt administration

ECF Volume Excess: ECF Volume Excess: TreatmentTreatment

Must address not only the ECF volume excess but Must address not only the ECF volume excess but also the underlying pathologic process.also the underlying pathologic process.

Treatment of the nephrotic syndrome and the Treatment of the nephrotic syndrome and the cardiovascular volume overload associated with cardiovascular volume overload associated with renal failure.renal failure.

Treatment of heart failure and cirrhosis.Treatment of heart failure and cirrhosis.


SodiumSodium

SodiumSodium

The primary extracellular cation.The primary extracellular cation. Always accompanies water in the extracellular Always accompanies water in the extracellular

fluid compartment.fluid compartment.

HyponatremiaHyponatremia

Defined as serum concentration less than 135 Defined as serum concentration less than 135 meq/L.meq/L.

Most common electrolyte abnormality observed in Most common electrolyte abnormality observed in a general hospitalized population.a general hospitalized population.

Initial approach is the determination of serum Initial approach is the determination of serum osmolality.osmolality.


SERUM OSMOLALITY

Normal Low High

ISOTONICHyponatremia

HyperproteinemiaHyperlipidemia

HYPERTONICHyponatremia

HyperglycemiaMannitol, sorbitol,Glycerol, maltose

HYPOTONICHyponatremia

VOLUME STATUS


VOLUME STATUS

Hypovolemic Euvolemic Hypervolemic

Una <10 meq/LExtrarenal saltDehydrationDiarrheaVomiting

Edematous states:Congestive heart failureHepatic diseaseNephrotic syndromeAdvanced CHF

SIADHPostop HypoNaHypothyroidismPsychogenic polydipsiaBeer potomaniaDrug reactions

Una >20 meq/LRenal salt lossDiureticsACE-inhibitorsNephropathiesMineralo-Corticoid lack

TreatmentTreatment

Hypertonic (3%) saline with furosemide is indicated for Hypertonic (3%) saline with furosemide is indicated for symptomatic hyponatremic patients.symptomatic hyponatremic patients.

For asymptomatic patients, approach includes water For asymptomatic patients, approach includes water restriction, isotonic saline infusion and administration of restriction, isotonic saline infusion and administration of demeclocycline.demeclocycline.

HypernatremiaHypernatremia

Serum sodium > 145 meq/LSerum sodium > 145 meq/L Develops from excess water loss, frequently Develops from excess water loss, frequently

accompanied by an impaired thirst mechanism.accompanied by an impaired thirst mechanism.

Hypernatremia: TreatmentHypernatremia: Treatment

Directed toward correcting the cause of the fluid Directed toward correcting the cause of the fluid loss and replacing water and, as needed, loss and replacing water and, as needed, electrolytes.electrolytes.

Calculation of water deficit:Calculation of water deficit: When calculating fluid replacement, both the deficit and When calculating fluid replacement, both the deficit and

the maintenance requirement should be added to each the maintenance requirement should be added to each 24-hour replacement regimen.24-hour replacement regimen.


Calculation of water deficit Calculation of water deficit (cont’d)(cont’d)Water deficit = current TBW x Water deficit = current TBW x ([Na] – 140)([Na] – 140)

140140

where [Na] is the measured serum sodium andwhere [Na] is the measured serum sodium and

TBW is the total body water (as percentage of the total TBW is the total body water (as percentage of the total body weight based on age and sex.body weight based on age and sex.


Given a 38/F with a body weight of 50 kg and a Given a 38/F with a body weight of 50 kg and a serum sodium level of 160 meq/L:serum sodium level of 160 meq/L:

What is the total water deficit?What is the total water deficit?

How much water should you give your patient during How much water should you give your patient during the first 24 hours?the first 24 hours?


Water deficit = TBW x Water deficit = TBW x ([Na] - 140)([Na] - 140)

140140

= (50 kg)(0.5) = (50 kg)(0.5) (160-140)(160-140)

140140

= 25 liters = 25 liters (20)(20)

140140

= 25 liters (0.14)= 25 liters (0.14)



Volume to be replaced in 24 hours = Volume to be replaced in 24 hours =

TBW x TBW x (160 – 148)(160 – 148)

148148

= 25 liters = 25 liters (12)(12)

148148

= 25 liters (0.08)= 25 liters (0.08)

= 2 liters= 2 liters


PotassiumPotassium

Hypokalemia Hypokalemia

A total body deficit of about 350 meq occurs for A total body deficit of about 350 meq occurs for each 1 meq/L decrement in serum potassium each 1 meq/L decrement in serum potassium concentration.concentration.

Changes in blood pH and hormones (insulin, Changes in blood pH and hormones (insulin, aldosterone, and aldosterone, and β-adrenergic agonists) β-adrenergic agonists) independently affect serum potassium levels.independently affect serum potassium levels.

Hypokalemia: Clinical Findings Hypokalemia: Clinical Findings

Symptoms and Signs:Symptoms and Signs: Muscular weaknessMuscular weakness FatigueFatigue Muscle crampsMuscle cramps Constipation or ileusConstipation or ileus Flaccid paralysis, hyporeflexia, and rhabdomyolysisFlaccid paralysis, hyporeflexia, and rhabdomyolysis

Hypokalemia: Clinical Findings Hypokalemia: Clinical Findings

Laboratory Findings:Laboratory Findings: Decreased amplitude and broadening of the T wavesDecreased amplitude and broadening of the T waves Prominent U wavesProminent U waves Depressed ST segmentsDepressed ST segments T wave inversionT wave inversion Atrioventricular block (1Atrioventricular block (1stst, 2, 2ndnd, 3, 3rdrd degree AV blocks) degree AV blocks) Cardiac arrestCardiac arrest

Note: Hypokalemia also increases the likelihood of Note: Hypokalemia also increases the likelihood of digitalis toxicitydigitalis toxicity

Hypokalemia: Treatment Hypokalemia: Treatment

Safest way is with oral potassium.Safest way is with oral potassium. Intravenous replacement is indicated for patients Intravenous replacement is indicated for patients

with severe hypokalemia.with severe hypokalemia. If serum potassium is > 2.5 meq/L, and there are If serum potassium is > 2.5 meq/L, and there are

ECG abnormalities, potassium can be given at a ECG abnormalities, potassium can be given at a rate of 10 meq/L/hr in concentration that should rate of 10 meq/L/hr in concentration that should never exceed 80 meq/L.never exceed 80 meq/L.


For severe deficiency, potassium may be given For severe deficiency, potassium may be given through a intravenous cutdown.through a intravenous cutdown.

Occasionally, hypokalemia may be refractory to Occasionally, hypokalemia may be refractory to potassium replacement. Magnesium deficiency potassium replacement. Magnesium deficiency may make potassium correction more difficult. may make potassium correction more difficult. Concomitant magnesium repletion avoids this Concomitant magnesium repletion avoids this problem.problem.


ORAL POTASSIUM REPLACEMENTSORAL POTASSIUM REPLACEMENTS

AMOUNTAMOUNT meq OF Kmeq OF K ANIONANION NAMESNAMES

LIQUIDSLIQUIDS 15 ml15 ml 1010 ClCl 5% Potassium chloride5% Potassium chloride

15 ml15 ml 2020 ClCl 10% Potassium chloride10% Potassium chloride

15 ml15 ml 4040 ClCl 20% Potassium chloride20% Potassium chloride

15 ml15 ml 2020 GluconateGluconate Potassium gluconatePotassium gluconate

POWDERSPOWDERS Packet Packet 1515 ClCl K-lorK-lor

PacketPacket 2020 ClCl Potassium chloridePotassium chloride

PacketPacket 2525 ClCl K-lyteK-lyte

TABLETSTABLETS 11 88 ClCl Slow-KSlow-K

11 88 ClCl Micro-K extencapsMicro-K extencaps

11 1010 ClCl K-dur 10K-dur 10

11 2020 ClCl K-dur 20K-dur 20


POTASSIUM CONTENT OF FOODSPOTASSIUM CONTENT OF FOODS

VERY HIGHVERY HIGH

(12-20 meq)(12-20 meq)

HIGHHIGH

(5-12 meq)(5-12 meq)

BEANSBEANS Garbanzo beansGarbanzo beans

Soy beansSoy beans

Kidney beans Navy beansKidney beans Navy beans

Lima beans Pinto beansLima beans Pinto beans

FRUIT (1/2 cup or as stated)FRUIT (1/2 cup or as stated) Papaya (one medium)Papaya (one medium) Apricots (3 halves)Apricots (3 halves)

Banana (6”)Banana (6”)

Cantaloupe (1/4”)Cantaloupe (1/4”)

Honeydew melon (1/4”)Honeydew melon (1/4”)

Orange (3”) and orange juiceOrange (3”) and orange juice

Pear (one large)Pear (one large)

Prunes (4) and prune juicePrunes (4) and prune juice

RhubarbRhubarb


POTASSIUM CONTENT OF FOODSPOTASSIUM CONTENT OF FOODS

VERY HIGHVERY HIGH

(12-20 meq)(12-20 meq)

HIGHHIGH

(5-12 meq)(5-12 meq)

VEGETABLES (1/2 cup or as VEGETABLES (1/2 cup or as stated)stated)

Artichoke (one)Artichoke (one)

Avocado (1/4)Avocado (1/4)

Brussel sproutsBrussel sprouts

Carrot (7 ½”) and chardCarrot (7 ½”) and chard

Ketchup (1 tbsp)Ketchup (1 tbsp)

Potato (one baked, one Potato (one baked, one broiled, 10 fries, ½ cup broiled, 10 fries, ½ cup mashed)mashed)

Pumpkin and spinachPumpkin and spinach

Tomato (one) and tomato Tomato (one) and tomato juicejuice

HyperkalemiaHyperkalemia

Many are spurious or associated with acidosisMany are spurious or associated with acidosis Common practice of repeatedly clenching and Common practice of repeatedly clenching and

unclenching the fist during venipuncture may raise unclenching the fist during venipuncture may raise the potassium concentration by 1-2 meq/L by the potassium concentration by 1-2 meq/L by causing local release of potassium from forearm causing local release of potassium from forearm muscles.muscles.


CAUSES OF HYPERKALEMIACAUSES OF HYPERKALEMIA

SPURIOUSSPURIOUS Leakage from erythrocytes if separation of serum from clot is Leakage from erythrocytes if separation of serum from clot is delayed.delayed.

ThrombocytosisThrombocytosis

Marked leukocytosisMarked leukocytosis

Repeated fist clenching during phlebotomyRepeated fist clenching during phlebotomy

Specimen drawn from arm with infusionSpecimen drawn from arm with infusion

DECREASED EXCRETIONDECREASED EXCRETION Renal failure, acute and chronicRenal failure, acute and chronic

Severe oliguriaSevere oliguria

Renal secretory defectsRenal secretory defects

Adrenocortical insufficiencyAdrenocortical insufficiency

Hyporeninemic hypoaldosteronismHyporeninemic hypoaldosteronism

Spironolactone, triamterene, ACE-I, trimethoprim, NSAIDsSpironolactone, triamterene, ACE-I, trimethoprim, NSAIDs


CAUSES OF HYPERKALEMIACAUSES OF HYPERKALEMIA

SHIFT FROM TISSUESSHIFT FROM TISSUES Burns, rhabdomyolysis, hemolysisBurns, rhabdomyolysis, hemolysis

Metabolic acidosisMetabolic acidosis

HyperosmolalityHyperosmolality

Insulin deficiencyInsulin deficiency

Hyperkalemic periodic paralysisHyperkalemic periodic paralysis

Succinylcholine, arginine, digitalis toxicity, beta-adrenergic Succinylcholine, arginine, digitalis toxicity, beta-adrenergic blockersblockers

EXCESSIVE INTAKEEXCESSIVE INTAKE Over treatment, orally or parenterallyOver treatment, orally or parenterally

Hyperkalemia: Clinical FindingsHyperkalemia: Clinical Findings

Weakness and flaccid paralysisWeakness and flaccid paralysis Abdominal distention and diarrheaAbdominal distention and diarrhea ECG is not a sensitive method, but if abnormalities ECG is not a sensitive method, but if abnormalities

are present, the most common findings are:are present, the most common findings are: Peaked T wavesPeaked T waves ST segment elevationST segment elevation Tachyarrhythmia / supraventricular tachycardiaTachyarrhythmia / supraventricular tachycardia Ventricular tachycardiaVentricular tachycardia Ventricular fibrillationVentricular fibrillation Cardiac arrestCardiac arrest

Hyperkalemia: TreatmentHyperkalemia: Treatment

Confirm that the elevated level of serum Confirm that the elevated level of serum potassium is genuine.potassium is genuine.

Measure plasma potassium.Measure plasma potassium. Withholding of potassium.Withholding of potassium. Giving cation exchange resins by mouth or Giving cation exchange resins by mouth or

enema: polystyrene sulfate, 40-80 g/day in divided enema: polystyrene sulfate, 40-80 g/day in divided doses.doses.


Emergent treatment is indicated if cardiac toxicity Emergent treatment is indicated if cardiac toxicity or muscular paralysis is present, or if or muscular paralysis is present, or if hyperkalemia is severe (> 6.5-7 meq/L) even in hyperkalemia is severe (> 6.5-7 meq/L) even in the absence of ECG changes.the absence of ECG changes.

Insulin plus 10-50% glucose may be employed to Insulin plus 10-50% glucose may be employed to deposit potassium with glycogen in the liver.deposit potassium with glycogen in the liver.

Calcium may be given intravenously as an Calcium may be given intravenously as an antagonist ion.antagonist ion.


Stimulate transcellular shifts by giving beta-Stimulate transcellular shifts by giving beta-adrenergic agonist drugs.adrenergic agonist drugs.

Sodium bicarbonate as an emergency measure.Sodium bicarbonate as an emergency measure. Hemodialysis or peritoneal dialysis.Hemodialysis or peritoneal dialysis.


EMERGENCY TREATMENT OF HYPERKALEMIAEMERGENCY TREATMENT OF HYPERKALEMIA

MODALITYMODALITY MECHANISM MECHANISM OF ACTIONOF ACTION

ONSETONSET DURATIONDURATION PRESCRIPTIONPRESCRIPTION K REMOVED K REMOVED FROM BODYFROM BODY

Calcium Calcium Antagonizes Antagonizes cardiac cardiac conduction conduction abnormalitiesabnormalities

0-5 min0-5 min 1 hour1 hour Ca gluconate 10%, Ca gluconate 10%, 5-30 ml IV;5-30 ml IV;

CaCl 5%, 5-30 ml CaCl 5%, 5-30 ml IVIV

NoneNone

BicarbonateBicarbonate Shifts K into Shifts K into cellscells

15-30 15-30 minmin

1-2 hours1-2 hours NaHCONaHCO33 44-88 44-88

meq IVmeq IVNoneNone

InsulinInsulin Shifts K into Shifts K into cellscells

15-60 15-60 minmin

4-6 hours4-6 hours SAI, 5-10 u IV, SAI, 5-10 u IV, plus glucose 50%, plus glucose 50%, 25 g IV25 g IV

NoneNone

AlbuterolAlbuterol Shifts K into Shifts K into cellscells

15-30 15-30 minmin

2-4 hours2-4 hours Nebulized Nebulized albuterol, 10-20 albuterol, 10-20 mg in 4 ml salinemg in 4 ml saline

NoneNone


NON-EMERGENCY TREATMENT OF HYPERKALEMIANON-EMERGENCY TREATMENT OF HYPERKALEMIA

MODALITYMODALITY MECHANISM MECHANISM OF ACTIONOF ACTION

DURATION OF DURATION OF TREATMENTTREATMENT

PRESCRIPTIONPRESCRIPTION K REMOVED K REMOVED FROM BODYFROM BODY

Loop diureticLoop diuretic Increased Increased renal K renal K excretionexcretion

0.5-2 hours0.5-2 hours Furosemide 40-160 mg IV Furosemide 40-160 mg IV or orally with or without or orally with or without NaHCONaHCO33, 0.5-3 meq/kg , 0.5-3 meq/kg

dailydaily

VariableVariable

Sodium Sodium polystyrene polystyrene sulfonate sulfonate (Kayexalate(Kayexalate

Ion exchange Ion exchange resin binds Kresin binds K

1-3 hours1-3 hours Oral: 15-30 g in 20% Oral: 15-30 g in 20% sorbitol (50-100 ml)sorbitol (50-100 ml)

Rectal: 50 g in 20% Rectal: 50 g in 20% sorbitolsorbitol

0.5-1 meq/g0.5-1 meq/g

HemodialysisHemodialysis Extracorporeal Extracorporeal K removalK removal

48 hours48 hours Blood flow Blood flow >> 200-300 200-300 ml/min; Dialysate K = 0ml/min; Dialysate K = 0

200-300 meq200-300 meq

Peritoneal Peritoneal dialysisdialysis

Peritoneal K Peritoneal K removalremoval

48 hours48 hours Fast exchange, 3-4 L/hrFast exchange, 3-4 L/hr 200-300 meq200-300 meq


CalciumCalcium

CalciumCalcium

Constitute 2% of body weight, but only 1% of the Constitute 2% of body weight, but only 1% of the total body calcium is in solution in body fluid.total body calcium is in solution in body fluid.

In plasma, calcium is present as a non-diffusible In plasma, calcium is present as a non-diffusible complex with protein (33%); as a diffusible but complex with protein (33%); as a diffusible but undissociated complex with anions like citrate, undissociated complex with anions like citrate, bicarbonate, and phosphate (12%); and as ionized bicarbonate, and phosphate (12%); and as ionized calcium (55%).calcium (55%).

CalciumCalcium

Normal total plasma (or serum) calcium Normal total plasma (or serum) calcium concentration is 8.5 to 10.5 mg/dL.concentration is 8.5 to 10.5 mg/dL.

It is the ionized calcium that is necessary for It is the ionized calcium that is necessary for muscle contraction and nerve function (normal: muscle contraction and nerve function (normal: 4.7 to 5.3 mg/dL).4.7 to 5.3 mg/dL).

HypocalcemiaHypocalcemia

Seen commonly in critically ill patients due to Seen commonly in critically ill patients due to acquired defects in parathyroid-vitamin D axis.acquired defects in parathyroid-vitamin D axis.

Results occasionally in hypotension which Results occasionally in hypotension which responds to calcium replacement therapy. responds to calcium replacement therapy.

HypocalcemiaHypocalcemia

CAUSES OF HYPOCALCEMIACAUSES OF HYPOCALCEMIA

DECREASED INTAKE OR ABSORPTIONDECREASED INTAKE OR ABSORPTION MalabsorptionMalabsorption

Small bowel bypass, short bowelSmall bowel bypass, short bowel

Vitamin D deficitVitamin D deficit

INCREASED IONSINCREASED IONS AlcoholismAlcoholism

Chronic renal insufficiencyChronic renal insufficiency

Diuretic therapy (furosemide or bumetanide)Diuretic therapy (furosemide or bumetanide)

ENDOCRINE DISEASESENDOCRINE DISEASES True and pseudohypoparathyroidismTrue and pseudohypoparathyroidism

Calcitonin hypersecretionCalcitonin hypersecretion

PHYSIOLOGIC CAUSESPHYSIOLOGIC CAUSES Alkalosis and decreased response to vit. DAlkalosis and decreased response to vit. D

Decreased serum albumin Decreased serum albumin

HyperphosphatemiaHyperphosphatemia

Aminoglycosides, loop diuretics, foscarnetAminoglycosides, loop diuretics, foscarnet

Hypocalcemia: Clinical Hypocalcemia: Clinical FindingsFindings

Symptoms and Signs:Symptoms and Signs: Extensive spasm of skeletal muscle causing cramps Extensive spasm of skeletal muscle causing cramps

and tetanyand tetany Laryngospasm with stridorLaryngospasm with stridor Convulsions with paresthesias of the lips and Convulsions with paresthesias of the lips and

extremitiesextremities Abdominal painAbdominal pain Chvostek’s signChvostek’s sign Trousseau’s signTrousseau’s sign

Hypocalcemia: Clinical Hypocalcemia: Clinical FindingsFindings

Laboratory Findings:Laboratory Findings: Low serum calciumLow serum calcium Elevated serum phosphorusElevated serum phosphorus Low serum magnesiumLow serum magnesium Prolonged QT interval on the ECGProlonged QT interval on the ECG

Hypocalcemia: TreatmentHypocalcemia: Treatment

Severe symptomatic hypocalcemia:Severe symptomatic hypocalcemia: In the presence of tetany, arrhythmias or seizures, In the presence of tetany, arrhythmias or seizures,

calcium gluconate 10% is administered intravenously for calcium gluconate 10% is administered intravenously for 10-15 minutes or via calcium infusion.10-15 minutes or via calcium infusion.

10-15 mg of calcium per kilogram body weight, or 6-8 10-15 mg of calcium per kilogram body weight, or 6-8 10-ml vials of 10% calcium gluconate (558-744 mg of 10-ml vials of 10% calcium gluconate (558-744 mg of calcium) is added to 1 liter of D5W and infused over 4 to calcium) is added to 1 liter of D5W and infused over 4 to 6 hours.6 hours.

Asymptomatic hypocalcemia:Asymptomatic hypocalcemia: Oral calcium and vitamin D preparationsOral calcium and vitamin D preparations Calcium carbonate is well tolerated and inexpensive.Calcium carbonate is well tolerated and inexpensive.

Hypocalcemia: TreatmentHypocalcemia: Treatment

TREATMENT OF HYPOCALCEMIATREATMENT OF HYPOCALCEMIA

MODALITYMODALITY AMOUNT OF CALCIUMAMOUNT OF CALCIUM ONSETONSET DOSEDOSE

Intravenous Intravenous calcium (Calcium calcium (Calcium gluconate)gluconate)

93 mg (4.7 meq) per 10 ml93 mg (4.7 meq) per 10 ml Immediate Immediate 93-186 mg over 10-15 mins; 93-186 mg over 10-15 mins; then 10-15 mg/kg over 4-6 then 10-15 mg/kg over 4-6 hours.hours.

Oral calcium Oral calcium (calcium (calcium carbonate)carbonate)

40% elemental calcium;40% elemental calcium;

250 mg/624 mg tablet or250 mg/624 mg tablet or

500 mg/1250 mg tablet or500 mg/1250 mg tablet or

500 mg/1500 mg tablet500 mg/1500 mg tablet

< 1 hour< 1 hour 250-500 mg calcium 3 to 5 250-500 mg calcium 3 to 5 times a day.times a day.

Hypercalcemia Hypercalcemia

CAUSES OF HYPERCALCEMIACAUSES OF HYPERCALCEMIA

INCREASED INTAKE OR INCREASED INTAKE OR ABSORPTIONABSORPTION

Milk-alkali syndromeMilk-alkali syndrome

Vitamin D or vitamin A excessVitamin D or vitamin A excess

ENDOCRINE DISORDERSENDOCRINE DISORDERS Primary and secondary hyperparathyroidismPrimary and secondary hyperparathyroidism

AcromegalyAcromegaly

Adrenal insufficiencyAdrenal insufficiency

NEOPLASTIC DISEASESNEOPLASTIC DISEASES Tumors producing PTH-related proteinsTumors producing PTH-related proteins

Metastases to boneMetastases to bone

Lymphoproliferative diseaseLymphoproliferative disease

Secretion of prostaglandins and osteolytic factorsSecretion of prostaglandins and osteolytic factors

MISCELLANEOUS CAUSESMISCELLANEOUS CAUSES Thiazide diuretics and renal transplant complicationsThiazide diuretics and renal transplant complications

Sarcoidosis and Paget’s disease of the boneSarcoidosis and Paget’s disease of the bone

Hypophosphatasia, immobilization, iatrogenicHypophosphatasia, immobilization, iatrogenic

Hypercalcemia: Clinical Hypercalcemia: Clinical FindingsFindings

Symptoms and Signs:Symptoms and Signs: Polyuria and constipationPolyuria and constipation Stupor, coma and azotemiaStupor, coma and azotemia Ventricular extrasystoles and idioventricular rhythmVentricular extrasystoles and idioventricular rhythm

Laboratory Findings:Laboratory Findings: Significant elevation of serum calciumSignificant elevation of serum calcium Serum phosphorus may or may not be elevatedSerum phosphorus may or may not be elevated Shortened QT interval on the ECGShortened QT interval on the ECG

Hypercalcemia: TreatmentHypercalcemia: Treatment

Renal excretion of calcium is promoted by giving Renal excretion of calcium is promoted by giving saline with furosemide.saline with furosemide.

Treatment of underlying condition.Treatment of underlying condition.


MagnesiumMagnesium

MagnesiumMagnesium

About 50% of total body magnesium exists in the About 50% of total body magnesium exists in the insoluble state in bone.insoluble state in bone.

Only 5% is present as extracellular cation; the Only 5% is present as extracellular cation; the remaining 45% is contained in cells as intracellular remaining 45% is contained in cells as intracellular cation.cation.

Normal plasma concentration is 1.5-2.5 meq/L, Normal plasma concentration is 1.5-2.5 meq/L, with about one-third bound to protein and two-with about one-third bound to protein and two-thirds existing as free cation.thirds existing as free cation.

Excretion is via the kidney.Excretion is via the kidney.

HypomagnesemiaHypomagnesemia

Nearly half of hospitalized patients have Nearly half of hospitalized patients have unrecognized hypomagnesemia.unrecognized hypomagnesemia.

In critically ill patients, arrhythmias and sudden In critically ill patients, arrhythmias and sudden death may be complications. death may be complications.

HypomagnesemiaHypomagnesemia

CAUSES OF HYPOMAGNESEMIACAUSES OF HYPOMAGNESEMIA

DIMINISHED ABSORPTION OR DIMINISHED ABSORPTION OR INTAKEINTAKE

Malabsorption, chronic diarrhea, laxative abuseMalabsorption, chronic diarrhea, laxative abuse

Prolonged gastrointestinal suctionProlonged gastrointestinal suction

Small bowel bypass, malnutritionSmall bowel bypass, malnutrition

Alcoholism, parenteral alimentationAlcoholism, parenteral alimentation

INCREASED LOSSINCREASED LOSS DKA, diuretic therapy, diarrheaDKA, diuretic therapy, diarrhea

Hyperaldosteronism, Bartter’s syndromeHyperaldosteronism, Bartter’s syndrome

HypercalciuriaHypercalciuria

Renal magnesium wastingRenal magnesium wasting

UNEXPLAINEDUNEXPLAINED HyperparathyroidismHyperparathyroidism

PostparathyroidectomyPostparathyroidectomy

Vitamin D therapyVitamin D therapy

Aminoglycoside antibiotics, cisplatin, amphotericin BAminoglycoside antibiotics, cisplatin, amphotericin B

Hypomagnesemia: Hypomagnesemia: Clinical FindingsClinical Findings

Symptoms and Signs:Symptoms and Signs: WeaknessWeakness Muscle crampsMuscle cramps CNS hyperexcitability with tremorsCNS hyperexcitability with tremors Athetoid movementsAthetoid movements Jerking, nystagmusJerking, nystagmus Positive Babinski responsePositive Babinski response Hypertension, tachycardia and ventricular arrhythmiasHypertension, tachycardia and ventricular arrhythmias Confusion and disorientationConfusion and disorientation

Hypomagnesemia: Hypomagnesemia: Clinical FindingsClinical Findings

Laboratory Findings:Laboratory Findings: Decreased serum magnesium levelsDecreased serum magnesium levels Hypocalcemia and hypokalemiaHypocalcemia and hypokalemia Prolonged QT interval on the ECGProlonged QT interval on the ECG Lengthening of the ST segment on the ECGLengthening of the ST segment on the ECG

Hypomagnesemia: TreatmentHypomagnesemia: Treatment

Use of IVF containing magnesium as chloride or Use of IVF containing magnesium as chloride or sulfate, 240-1200 mg/day (10-50 mmol/day) sulfate, 240-1200 mg/day (10-50 mmol/day) during the period of severe deficit, followed by 120 during the period of severe deficit, followed by 120 mg/day (5 mmol/day) for maintenance.mg/day (5 mmol/day) for maintenance.

MgSOMgSO44 may also be given intramuscularly in a may also be given intramuscularly in a

dosage of 200-800 mg/day (8-33 mmol/day) in dosage of 200-800 mg/day (8-33 mmol/day) in four divided doses.four divided doses.

Serum levels must be monitored.Serum levels must be monitored.

HypermagnesemiaHypermagnesemia

Almost always the result of renal insufficiency and Almost always the result of renal insufficiency and the inability to excrete what has been taken in the inability to excrete what has been taken in from food or drugs, especially antacids and from food or drugs, especially antacids and laxatives.laxatives.

Potentially life-threatening as it impairs both Potentially life-threatening as it impairs both central nervous system and muscular function.central nervous system and muscular function.

Hypermagnesemia:Hypermagnesemia:Clinical FindingsClinical Findings

Symptoms and Signs:Symptoms and Signs: Muscle weaknessMuscle weakness Mental obtundation and confusionMental obtundation and confusion HypotensionHypotension Respiratory muscle paralysis or cardiac arrestRespiratory muscle paralysis or cardiac arrest

Laboratory Findings:Laboratory Findings: Elevated serum magnesium, BUN, creatinine, KElevated serum magnesium, BUN, creatinine, K Decreased serum calciumDecreased serum calcium Increased PR interval on the ECGIncreased PR interval on the ECG Broadened QRS complex with elevated T wavesBroadened QRS complex with elevated T waves

Hypermagnesemia: TreatmentHypermagnesemia: Treatment

Alleviating renal insufficiencyAlleviating renal insufficiency Administration of calciumAdministration of calcium Hemodialysis or peritoneal dialysisHemodialysis or peritoneal dialysis

In all things, you shall find everywhere the Acid and the Alcaly.

OTTO TACHENIUS (1620)


Acid-Base DisturbancesAcid-Base Disturbances

Arterial Blood GasesArterial Blood Gases

Regulation of pH is accomplished by:Regulation of pH is accomplished by: KidneysKidneys LungsLungs Buffer systemsBuffer systems

Information obtained from the arterial blood gas Information obtained from the arterial blood gas measurements:measurements: pHpH Partial pressure of carbon dioxide (pCOPartial pressure of carbon dioxide (pCO22))

Partial pressure of oxygen (pOPartial pressure of oxygen (pO22))

HCOHCO33 level level

Oxygen saturation (OOxygen saturation (O2Sat2Sat))


Normal values:Normal values: pH = 7.35 – 7.45pH = 7.35 – 7.45 pCOpCO22 = 35 – 45 mmHg = 35 – 45 mmHg

pOpO2 2 = 80 – 100 mmHg= 80 – 100 mmHg

HCOHCO33 = 22 – 26 meqs/L = 22 – 26 meqs/L

OO2Sat2Sat > 95% > 95%


Steps in obtaining an ABG specimen:Steps in obtaining an ABG specimen: Check the bleeding parameters of the patient.Check the bleeding parameters of the patient. Prepare the following:Prepare the following:

Glass syringeGlass syringe Heparin (1,000 units/mL)Heparin (1,000 units/mL) AlcoholAlcohol Cotton balls (soaked with alcohol AND dry)Cotton balls (soaked with alcohol AND dry) Container with ice waterContainer with ice water

Aspirate 1 mL of heparin using a glass syringeAspirate 1 mL of heparin using a glass syringe


Steps in obtaining an ABG specimen Steps in obtaining an ABG specimen (cont’d)(cont’d):: Coat the inner surface of the syringe with heparin, Coat the inner surface of the syringe with heparin,

taking care to pull and push the plunger to make sure taking care to pull and push the plunger to make sure heparin evenly coats the syringe.heparin evenly coats the syringe.

Expel the excess heparin from the syringe.Expel the excess heparin from the syringe. Palpate for the radial pulse.Palpate for the radial pulse. With the needle directed at a slight angle from the With the needle directed at a slight angle from the

vertical, and pointed cephalad, gradually puncture the vertical, and pointed cephalad, gradually puncture the site and wait for arterial blood to rush in.site and wait for arterial blood to rush in.


Steps in obtaining an ABG specimen Steps in obtaining an ABG specimen (cont’d)(cont’d):: After obtaining the specimen, secure the needle and After obtaining the specimen, secure the needle and

place the syringe with the specimen in ice water.place the syringe with the specimen in ice water. Apply direct pressure on the puncture site for at least Apply direct pressure on the puncture site for at least

one minute, or until bleeding stops using a dry sterile one minute, or until bleeding stops using a dry sterile cotton ball.cotton ball.

Send the specimen directly to the laboratory.Send the specimen directly to the laboratory. A sample is allowed to stand for a maximum of two A sample is allowed to stand for a maximum of two

hours only.hours only.

ABG InterpretationABG Interpretation

SUMMARY OF EXPECTED COMPENSATION FOR SIMPLE ACID-BASE DISORDERSSUMMARY OF EXPECTED COMPENSATION FOR SIMPLE ACID-BASE DISORDERS

DISORDERDISORDER INITIAL CHANGEINITIAL CHANGE COMPENSATORY RESPONSECOMPENSATORY RESPONSE

Metabolic AcidosisMetabolic Acidosis Decrease in HCODecrease in HCO33-- Decrease in pCODecrease in pCO22::

Δ Δ pCOpCO22 = 1.1 – 1.3 (Δ = 1.1 – 1.3 (ΔHCOHCO33--))

Metabolic AlkalosisMetabolic Alkalosis Increase in HCOIncrease in HCO33-- Increase in pCOIncrease in pCO22::

Δ Δ pCOpCO22 = 0.6 – 0.7 (Δ = 0.6 – 0.7 (ΔHCOHCO33--))

Respiratory AcidosisRespiratory Acidosis Increase in pCOIncrease in pCO22 Increase in HCOIncrease in HCO33--

ACUTE: ACUTE: ΔΔHCOHCO33--= 0.1 = 0.1 Δ Δ pCOpCO22 ++ 2 2

CHRONIC: CHRONIC: ΔΔHCOHCO33--= 0.3 – 0.35 = 0.3 – 0.35 Δ Δ pCOpCO22

Respiratory AlkalosisRespiratory Alkalosis Decrease in pCODecrease in pCO22 Decrease in HCODecrease in HCO33--

ACUTE: ACUTE: ΔΔHCOHCO33--= 0.2 – 0.25 = 0.2 – 0.25 Δ Δ pCOpCO22

CHRONIC: ΔCHRONIC: ΔHCOHCO33--= 0.4 – 0.5 = 0.4 – 0.5 Δ Δ pCOpCO22

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