fluid, electrolyte & acid-base balance dr. reem ali spring semester 2011-2012

FLUID, ELECTROLYTE &

ACID-BASE BALANCE

DR. REEM ALI

Spring Semester 2011-2012

Body Fluids

Total body fluids/water (TBW) represents 40%-60% of the adult total body weight

TBW decreases with age

TBW consists of intracellular (ICF)and extracellular fluids (ECF)

Body Fluids

ICF: within the cells constitutes about 2/3 of TBW contains solutes such as O2,

electrolytes & glucose Provides a medium for metabolic

processes Primary electrolytes are K, Mg,

ECF constitutes 1/3 of TBW 50% of TBW is contained within the ECF & for

toddlers 30% Is a transport system to carry nutrients and remove

waste products Primary electrolytes are Na, Cl, bicarbonate ECF breaks down into

Intravascular: in blood vessels Interstitial: surrounding the cell and constitutes ¾ of

ECF. Contains little/no protein Transcellular: in special body cavities such as

cerebrospinal, synovial, pleural)

Body Fluids

Functioning of body water

Medium in which body solutes are dissolve Medium for metabolic reactions A conductor of electrochemical activity such as

neurotransmission Transport nutrients and other substance to

cells and remove waste products Lubricant Insulator and shock absorber Regulating body temperature

Daily Maintenance Fluid Requirement

Body Weight (Kg) Amount of Fluid/day

1- 10 100mL/kg

11 – 20 1000 ml + 50ml/kg for each kg more than 10kg

More than 20 1500 ml + 20ml/kg for each kg more than 20kg

Increased requirements

Fever, vomiting, diarrhea, diabetes, shock, burns, excessive urination, tachycardia

Decreased requirements

CHF, SIADH (syndrome of inappropriate anti-diuretic hormone, mechanical ventilation, renal failure & increased ICP

Fluid Loss in Children

Infants prone to fluid loss than adults due to:

A higher proportion of fluid in the EC compartment

Greater surface area in relation to body mass Higher metabolic rate Immature kidneys and immature haemostatic

regulation system(buffer) Greater insensible water loss Inability to shiver or sweat to control temperature

Primary Electrolytes

laboratory tests show the values of electrolytes in blood plasma (ECF)

Mechanisms of Fluid Movement

Hydrostatic pressure/filtrationMovements of fluid from area of high hydrostatic

pressure to lower pressure areae.g increased pressure in the arteries pushes fluids

through capillary walls into the interstitial spaces

Active transportMovement of substance across the cell membrane

from a less concentration solution to higher concentrated by a carrier

Osmotic pressure Movement of water from low osmotic pressure to

higher osmotic pressure

Mechanisms of Fluid Movement

Osmotic pressure Osmolality is the concentration of solutes in the body

fluids and reported by mOsm/kg

Sodium (Na) is the primary determinant of serum osmolality

Tonicity refers to the osmolality of solution Isotonic solution has the same osmolality as the body fluids

(e.g. normal saline 0.9%) Hypertonic solution has a higher osmolality as the body

fluids (e.g. normal saline 3%) Hypotonic solution has a lower osmolality as the body

fluids (e.g. normal saline 0.45%)

Mechanisms Influencing Fluid Balance

Antidiuretic hormone (ADH): controlled by the posterior pituitary gland. ADH promotes water retention in the renal system

Thirst: is stimulated by increased solute concentration of ECF and decreased intravascular volume

Rennin-angiotension system: rennin is stimulated by low flow to kidneys, rennin and plasma globulin generate angiotension which acts as a vasoconstrictor. Angiotension also stimulates aldosterone

Other factors such as hyperventilation, hypoventilarion, vomiting, diarrhea, circulatory failure may alter the volume of fluid lost

Mechanisms that maintain Electrolyte Concentration

Aldosterone: secreted by the adrenal cortex. Aldosterone enhances Na reabsorption in the

renal tubules decreases reabsorption of KConserve Chloride with Na

Parathyroid glands regulate CaParathormone is secreted when the

concentration of Ca is low in the extracellular fluid

Parathormone stimulates the release of Ca from bone

Factors affecting body fluid, electrolytes and acid-base balance

Age Infants have premature kidneys which can not concentrate urine as

adult Rapid respiration Great body surface area High metabolic rate Elderly people have the thirst response blunted

Gender & body size Fat people have less fluid

Environmental temperature Salt and water are lost through sweating

Lifestyle Diet Exercise Stress Alcohol consumption

Imbalance

Greater majority of imbalances in hydration and electrolytes are secondary to vomiting and diarrhea

Dehydration: is a body fluid imbalance

excessive loss of water from the body Total fluid output exceeds total fluid intake Fluid disturbance is common in infants and children Dehydration can be classified by the type and degree

Dehydration

Types of dehydration

Isotonic/isonatremic dehydration

Hypertonic/hypernatremic dehydration

Hypotonic/hyponatremic dehydration

Types of Dehydration

Isotonic/isonatremic dehydration

Occurs when fluids and electrolytes losses are in same proportion as they exist in the body.

Fluid osmolarity is not affected. There is deficit in TBW. This can be seen in 70% of children with diarrhea. Shock is the greatest threat to life in this type. Plasma sodium remains within normal limits (130 – 150

mEq/L )



Represents 10-20% of dehydration in children and most dangerous type

Plasma Na+ > 145 mEq / L

The causes can be When the water intake decreases and Na increases

(e.g. administration of hypertonic IV fluid) Proportionally greater loss of water than Na, can occur

when insensible loss of water from skin and respiration tract is high due to burn, fever, respiratory infection

ADH failure



Na+ increase the osmotic pressure in the blood vessels that shifts the fluids from the IC to the ECS

Body reacts to this type of dehydration by stimulating thirst and ADH

CM: thirst, lethargy, neurological dysfunction due to dehydration of brain cells


Hypotonic/hyponatremic dehydration

Represents 10% of dehydration in children Plasma Na+ < 130 mEq/L Occurs when electrolytes deficit exceeds the water

losses Can be seen in cystic fibrosis due to excessive lose

of Na+ through sweating Water shifts from ECF to ICF (osmotic pressure)

leading to circulatory collapse CM: lethargy, confusion, apprehension, depressed

reflexes, seizures and coma

Sign Isotonic Hypotonic Hypertonic

Skin

Color Gray Gray Gray

Temperature

Cold Cold Cold or hot

Turgor Poor Very poor Fair

Feel Dry Clammy ودبق بارد Thickened

Mucus membrane Dry Slightly moist parched

Tearing and salivation

Absent Absent Absent

Eyeball Sunken Sunken Sunken

Fontanel Sunken Sunken Sunken

Body temperature Hypo or hyper Hypo or hyper Hypo or hyper

Pulse Rapid Very rapid Moderately rapid

Respiration Rapid Rapid Rapid

Behavior irritable to lethargic

Lethargic to comatose; convulsions

Marked lethargy excessive irritability on stimulation

Degree of Dehydration

Sign Mild Moderate Severe

Fluid loss < 5% 5% - 9% >= 10%

Skin Color Pale Gray Mottled

Skin Turgor Poor Very poor Fair

Mucus membrane

Dry Very dry parched

Urine output Decreased Oliguria Marked oliguria

BP Normal Normal/low low

Pulse rate Normal/increased

Increased Rapid & thready

Capillary refill Normal (< 2 sec)

Delayed (2-3 sec)

Delayed (>3 sec)

LOC Alert Irritable/lethargic

Lethargic- comatose

Causes of Dehydration

Vomiting & diarrhea Lack of oral intake Fever Diabetes mellitus Tachypnea (as in bronchitis) Burns

Assessment of dehydration

Weight Output V/S Fontanelles Skin circulation: pulse, BP, capillary refill Laboratory test

Urine specific gravity (> 1.030) CBC ( increased Hgb and Hct) BUN (elevated) ABGs (low serum pH acidosis) Electrolytes : low Na+ in urine & altered serum

electrolytes

Nursing Diagnosis & Intervention

Diagnosis: Fluid Volume Deficit

Intervention Assess hydration status Intake & output Daily weight Correct fluid balance

(rehydration) Administer ORS (oral rehydration

solution) Administer I.V fluids Monitoring IV fluid (site & rate) Withhold a full diet until hydration

level is normal

Oral Rehydration Solution

ORS Treatment of choice for most cases of dehydration

caused by diarrhea 50 ml/kg Q 4hrs for mild & 100ml for moderate cases Stool losses is replaced with ORS 1:1 if the volume of

stool is unknown 10ml/kg for each diarrheal stool Suitable to treat isotonic, hypo/hypertonic dehydration Vomiting is not a contraindication ORS is administer by spoon or syringe 5-10ml every 1-5

minutes In the maintenance phase ORS can be alternated with

other fluid, BF or even regular diet Early introduction of nutrient improved the reduce wt

loss and shorten the duration of illness BF should continue with ORS

Rehydration By IV

For severe dehydration (vomiting) Treatment phases

Restore circulation by ringer’s lactate, saline, plasma or albumin 130 mEq of Sodium ion/L 109 mEq of cholride/L lactate metabolised by liver and form bicarbonate (mainly used in the

case of metabolic acidosis) 4 mEq of potassium/L 3 mEq of calcium/L

Repletion therapy correct for previous and ongoing losses and normal fluid requirement (KcL can be added)

Stabilization: IV fluid for maintenance and ongoing losses. Oral intake can be resumed in this phase

Rehydration

Intravenous Fluid (IV) Most common IV solution constitutes of

dextrose (5% or 10%) and NaCl (around 0.22%-0.3%)

It prevents brain edema by having NaCl in the solution at least 0.2%. Glucose is rapidly metabolized

In case of peripheral circulatory collapse, hypovolemic shock or cardiopulmonary arrest IV fluid can be administered intraosseously

Nursing Care of Client with IV

Monitor client with I.V fluids Site & stability Infiltration

Fluid is leaking into tissues Site is pale, cool, edematous, flow rate decreases IV must be removed and restarted in a new site

Phlebitis Vein is irritated by catheter or medication Site is red, painful, warm and flow rate is

decreased IV must be removed and restarted in a new site Warm compresses are applied to the

inflammation

Nursing Care of Client with IV

Monitor client with I.V fluids Circulatory overload

Flow rate exceeds the cardiovascular system’s capability to adjust to the increased fluid volume

Client exhibit dyspnea, crackles, distended neck veins and increase BP

IV must be removed and restarted in a new site Stop the infusion & notify the Dr. Regulation of flow rate

Milliliter to be infused x drop factor number of hours x 60 minutes

Total Parenteral Nutrition (TPN)

Complete nutrition (carbohydrate, electrolytes, vitamins, minerals, fats)

Is administered for children who can not consume nutrition via GI tract to sustain metabolic requirements for long period

Is administered by IV or catheter External or internal jugular vein to

superior vena cave Subclavian vein to superior vena

cava Umbilical catheter

Total Parenteral Nutrition (TPN)

Indication for TPN Prolonged malnourishment Premature infants GI tract abnormalities Inflammatory bowel disease Severe burns, Renal failure, AIDS

Complications of TPN: infection liver dysfunction Respiratory Distress

Diarrhea

Frequent passage of loose and abnormally watery stools

Acute diarrhea (lasts less than 4 weeks in children) is most common GI alteration in children and leading cause of death in children in developing countries

Possible causes of acute diarrhea Rotavirus most common of nonbacterial diarrhea (gastroenteritis) Bacterial infection such as Salmonella, Shigella Upper respiratory and UT infection Antibiotics, toxins Irritable bowel syndrome

Diarrhea

Chronic diarrhea Malabsorption syndromes Anatomic defects Allergy Lactose intolerance Inflammatory disease Parasites immunodeficiency

Assessment: Diarrhea

Depends on the severity of diarrhea Physical assessment includes

Skin Mucous membrane Eyes Fontanells (infants) Circulation, respiration and neurologic

signs

Degree of diarrhea

S& S Rehydration Replacement of losses

Maintenance therapy

Mild (5% loss of Wt)

Increased thirstSlight dryness of buccal mucous membrane

ORS 50ml/kg for 4 hrs

ORS10 ml/kg for each stool loss

Continue BF or usual diet

Moderate(6% -9% loss of Wt)

Loss of skin turgor, dry mucous membrane, sunken eyes and fontanel

ORS 100ml/kg for 4 hrs

As above As above

Severe(more than 9 % loss of Wt)

Signs of moderate dehy. + rapid thready pulse, cyanosis, lethargy, coma

IV fluids (Ringer’s lactate) 40ml/kg/hr until the pulse and LOC return to normal then ORS50-100ml/kg

As above As above

Overhydration

Overhydration occurs when the body receives more fluids than it can

excrete Receive IV too rapidly (normal kidneys), dialysis or

enema ECF cause cardiovascular load which may lead to cardiac

failure

Edema The presence of excess fluid in the interstitial spaces In infants it can be around the eyes, occipital, genital,

presacral areas Pitting edema; when exerting pressure with the finger

there is impression in the skin that lasts for seconds

Edema

Generalized edema can be seen Face,

extremities, perineum, torso

Distention of the jugular vein

Daily wt & abdominal girth

Assess pitting edema by pressing the fingertip against a bony prominence for 5 sec

Electrolytes Imbalances

Potassium 95% in the IC Excess K is excreted by kidneys K normal value for a child 3.5 – 5.5 mEq/L Hypokalemia

K < 3.5 mEq/L Caused by vomiting , diarrhea, starvation, trauma

from injury or surgery, gastric suction and diuretics CM: loss of muscle tone (muscle weakness),

diminished bowel sound (abdominal distension), lethargy, cardiac dysrhythmia, shallow breathing, polyuria

TX: IV or oral administration of K; increase dietary intake


Potassium Hyperkalemia

K > 5.5 mEq/LCaused by rapid administration of IV

KcL , renal failure.CM: Cardiac irregularities , , malaise,

irritability, muscle weakness, oliguria to anuria, nausea & diarrhea

when K above 6 mEq/L cardiac arrest may occur

TX: admi K free fluids; dialysis; K-removing resin


Calcium

Ca 4 – 5.5 mEq/L Necessary for cardiac, neural and muscular

functioning Hypocalcemia: Ca < 4 mEq/L

Caused by Vit D deficiency, burns, diarrhea, renal failure and inadequate Ca OR removal of parathyroid glands

CM: tetany, cramp, neuromuscular irritability, convulsion, hypotension

TX: oral or parenteral calcium replacement


Hypercalcemia: Ca > 5.5 mEq/L

Caused by: vit D, prolong immobilization, hyperparatheroidism

CM: N&V, constipation, flank pain, bradycardia, weakness fatigue, deep bone pain

TX: correction of primary problem and increase fluid intake

Acid-Base Balance

Normal pH is essential for all body functioning

pH refers to hydrogen ion concentration (H+) system responsible for maintaining a narrow pH

(Normal arterial blood pH 7.35 – 7.45) are: Buffering system mainly HCO3 (hemoglobin, plasma

protein, phosphate and bones) Respiratory system Kidneys

Acid-base balance is evaluated directly from PaCO2 (ABGs) (Normal PaCO2 is 35 – 45 mmHg) and calculated HCO3 (Serum HCO3 level is 22-26 mEq/L)

Acid-Base Balance

Acidosis is the accumulation of acid or loss of base pH < 7.35

Alkalosis is the accumulation of base or loss of acid pH > 7.45

Acid-base disorders The abnormalities of plasma bicarbonate concentration

refer to metabolic process Metabolic acidosis Metabolic alkalosis

The abnormalities in PCO2 increase or decrease is called respiratory process Respiratory acidosis Metabolic alkalosis

Acid-base balance regulatory mechanism

The body has three mechanisms for maintaining acid-base balance; named in order of the speed with which they act: Buffers

Respiratory mechanism

Urinary mechanism


Buffers Consists of chemicals are present in blood and other body

fluids which combine with relatively strong acids or bases to convert them to weaker acids or bases

Buffers function to prevent marked changes in blood pH levels

The chief buffer pair in the blood is carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)

When acid-base is balanced the ration of HCO3 to H2CO3 is 20:1 CO2 + H2O - H2CO3 HCO3¯ +H+

Bicarbonate buffers are actively and constantly regulated by the action of the respiratory and urinary system


Other buffers in the body fluids

ProteinPhosphate Hemoglobin, and bones


Respiratory regulation Regulation acid-base by eliminatin or retaining

CO2 (altering the depth and rate RR)

PCO2 refer to pressure of carbon dioxide in venous blood

PaCO2 refer to pressure of carbon dioxide in arterial blood. Normal PaCO2 is 35-45mmHg If the PCO2 level is (respiratory acidosis) the rate and

depth to excrete CO2 to decrease pH

If the PCO2 level is (respiratory alkalosis) the rate and depth to retain CO2 to increase pH


Renal regulation Kidney regulate acid-base by excreting or

conserving HCO3 or H+ In metabolic acidity (decreased HCO3) kidneys

reabsorb & regenerate HCO3 and remove H+ In metabolic alkalosis (increased HCO3) kidneys

retain H+ and remove HCO3 Serum HCO3 level is 22-26 mEq/L

Respiratory Acidosis

pH < 7.35 Caused by CO2 retention ( aspiration, spasm,

edema of airways, pulmonary edema, sleep apnea, overdose sedation, head injury, asthma attack, atelectasis)

In respiratory acidosis kidneys retain HCO3 CM: dyspnea, cyanosis, tachycardia, headache,

blurred vision, anxiety, restlessness & tremors Management: Correct underlying causes

(bronchodilators, antibiotics, ventilation and decrease the use of sedation)

Respiratory Alkalosis

pH > 7.45 Caused by falling of CO2 ( hyperventilation;

anxiety, pain fever) In respiratory alkalosis kidneys excrete HCO3 CM: deep and rapid breathing , tetany, CNS

alteration (irritability), light headache, altered LOC, paresthesia of extremities , arrhythmias

Management: treat the underlying causes ( stress management , pain control, adjust ventilation)

Metabolic Acidosis

pH < 7.35 ; HCO3 < 22 Caused by :

Gain acid by tissue hypxia, DKA , starvation( fat metabolism produce ketone bodies that includes keto acids),ingestion of acid, renal failure

Loss of HCO3 by diarrhea

In metabolic acidosis respiratory center increases the rate and depth of respiration to eliminate CO2

CM: increase the depth of respiration, arrhythmia, lethargy coma, muscle weakness anorexia

Metabolic Alkalosis

pH > 7.35 ; HCO3 > 26 Caused by :

Gain HCO3 by excessive administration sodium bicarbonate, blood transfusion

Loss of H+ by vomiting, ingestion of antacid Diuretics and hypokalemia

In metabolic alkalosis respiratory center decreases the rate and depth of respiration to retain CO2

CM: weakness, hypertonicity/tetany, dizziness

ABGs & Metabolic Process

Alteration PaCO2 HCO3 Primary Cause

Respiratory Acidosis Hypoventilation

Respiratory AlkalosisHyperventilation

Metabolic AcidosisAdd acid or loss base ( diarrhea)

Metabolic AlkalosisAdd base or loss acid (Vomiting)

To determine the origin of acid-base imbalance, check the pH first:If the pH between 7.35-7.40 this indicates primary acidosis If the pH between 7.40-7.45 this indicates primary alkalosis

ABGs Interpretations

PaCO2 is a better indicator of alveolar ventilation

Abnormal PaCO2 is caused only by abnormal ventilation

Base E is a preferred measure of base because it measures both HCO3 and other buffer anions of whole blood (Hgb, plasma protein)

Base E reflects metabolic activity (normal value -2 to + 2)

ABGs

BICARB pH

CO2 pH

BICARB pH

CO2 pH

ABGs Analysis: three rules of thumb

If the pH and PCO2 are changing in opposite directions, a respiratory disorder is present

If the pH and HCO3 are changing in same direction , a metabolic disorder is present

If the PCO2 and HCO3 are changing in same direction, the body is compensating for an imbalance In this case , if pH still is abnormal the

imbalance is only partially compensated If the pH is normal it is fully compensated state

HCO3 META.pH

PaCO2 pH RESP.

Opposite direction

Same direction

No click

Jane Doe is a 45-year-old female admitted to the nursing unit with a severe asthma attack. She has been experiencing increasing shortness of breath since admission three hours ago. Her arterial blood gas result is as follows:

pH = 7.22

CO2 =55

HCO3 = 25



pH = 7.22 CO2 =55 HCO3 = 25

Follow the steps:1. Assess the pH. It is low (normal 7.35-7.45); therefore, we have acidosis.

2. Assess the PaCO2. It is high (normal 35-45) and in the opposite direction of the pH.

3. Assess the HCO3. It has remained within the normal range (22-26).



pH = 7.22

CO2 =55

HCO3 = 25 Acidosis is present (decreased pH) with the PaCO3

being increased, reflecting a primary respiratory problem. For this patient, we need to improve the ventilation status by providing oxygen therapy, mechanical ventilation, pulmonary toilet or by administering bronchodilators.


John Doe is a 55-year-old male admitted to your nursing unit with a recurring bowel obstruction. He has been experiencing intractable vomiting for the last several hours despite the use of antiemetics. His arterial blood gas result is as follows:

pH = 7.50

CO2 =42

HCO3 = 33


John Doe is a 55-year-old male admitted to your nursing unit with a recurring bowel obstruction. He has been experiencing intractable vomiting for the last several hours despite the use of antiemetics. His arterial blood gas result is as follows:

pH = 7.50

CO2 =42

HCO3 = 33 Alkalosis is present (increased pH) with the

HCO3 increased, reflecting a primary metabolic problem. Treatment of this patient might include the administration of I.V. fluids and measures to reduce the excess base.


John Doe is admitted to the hospital. He is a kidney dialysis patient who has missed his last two appointments at the dialysis center. His arterial blood gas result is as follows:

pH = 7.32

CO2 =32

HCO3 = 18


John Doe is admitted to the hospital. He is a kidney dialysis patient who has missed his last two appointments at the dialysis center. His arterial blood gas result is as follows:

pH = 7.32; CO2 =32; HCO3 = 18 Assess the PaCO2. It is low. Normally we would expect the

pH and PaCO2 to move in opposite directions, but this is not the case. Because the pH and PaCO2 are moving in the same direction, it indicates that the acid-base disorder is primarily metabolic. In this case lungs are acid-base buffers (compensating) by “blowing off excessive C02”, and therefore increasing the pH.

Assess the HCO3. It is low (normal 22-26). We would expect the pH and the HCO3 to move in the same direction, confirming that the primary problem is metabolic.

a partially compensated metabolic acidosis.


Jane Doe is a patient with chronic COPD being admitted for surgery. Her admission labwork reveals an arterial blood gas with the following values:

pH = 7.35; CO2 =48; HCO3 = 28


Jane Doe is a patient with chronic COPD being admitted for surgery. Her admission labwork reveals an arterial blood gas with the following values: pH = 7.35; CO2 =48; HCO3 = 28

1. Assess the pH. It is within the normal range, but on the low side of neutral (<7.40).

2. Assess the PaCO2. It is high the pH and PaCO2 to move in opposite directions thus the primary problem is respiratory.

3. Assess the HCO3. It is also high (22-26). Because they are moving in opposite directions, it confirms that the primary acid-base disorder is respiratory and that the kidneys are attempting to compensate by retaining HCO3.

Because the pH has returned into the low normal range, we would interpret this ABG as a fully compensated respiratory acidosis.


Nursing Process: acute diarrhea & Vomiting

Nursing Diagnosis Fluid volume deficit R/T excessive GI losses in stool or

emesis Interventions

Administer ORS frequently in small amounts and alternate ORS with BM, lactose-free formula (vomiting is not a contraindication of ORS unless it is severe)

IV fluid for severe dehydration Administer medication as ordered After rehydration start regular diet as tolerated Strict I&O, monitor urine specific gravity , daily wt, V/S,

skin, mental status Discourage intake of clear fluid, carbonated soft drinks

because these drinks are have low electrolytes Family education (monitoring hydration level)


Nursing diagnosis: altered nutrition; less than body requirement R/T inadequate intake and excessive losses (diarrhea)

Interventions Encourage early restoration of regular diet such as BF Avoid food with low concentration of electrolyte Record response to feeding Assess family’s concern to promote compliance with the

medical regimen


Nursing diagnosis: Impaired skin integrity R/T increased irritation caused by

frequent and loose stool

Risk for infection R/T GI invading microorganism

Fear/anxiety R/T separation from parents, home and exposure to distress and painful procedures

Altered family functioning R/T situational crisis and knowledge deficit

Knowledge deficit R/T to novelty of the experience (new exposure)

fluid, electrolyte & acid-base balance dr. reem ali spring semester 2011-2012

Documents

body solutes

body fluids icf

special body cavities

higher osmolality

higher proportion of

adult total body weighttbw

higher osmotic pressure

lower osmolality