Homeostasis Fluid Balance

NURN 160 Nursing Concepts I

Susan Thompson, MS, RN,B.C.

Homeostasis

• the state of dynamic equilibrium in the internal environment of the body maintained by adaptive processes

Body fluid composition• Water

• Electrolytes:– dissociate in solution and carry an electrical charge• Cations• Anions

Non electrolytes:• substances that do not dissociate in solution

– Glucose– urea

Fluid compartments

• Intracellular fluid (ICF) 2/3

• Extracellular fluid (ECF) 1/3– Intravascular

– Interstitial

– Transcellular

Fluid and Solute Movement

• Depends upon:–Cell membrane–Pores –Molecule size –Presence of fat

Transport Processes

• Diffusion/Facilitated Diffusion

• Osmosis

• Active Transport

Diffusion/Facilitated Diffusion

Osmosis

Active Transport• requires energy (ATP)

Osmotic and Hydrostatic Pressures

• Osmotic pressure • Oncotic/Colloidal Pressure• Hydrostatic Pressure –Filtration

Capillary Dynamics

Functions of Body Water

• Transportation • Excretion • Regulation• Lubrication • Medium for food digestion• Space filler

Fluid Gains and Losses

• Goal: Homeostasis

• Normal fluid gains and losses

• Abnormal fluid gains and losses

Regulation of Fluid balance

• Goal: Preserve the balance between fluid intake and output

»Thirst»Antidiuretic hormone »Aldosterone »Renin-angiotensin»Atrial natriuretic peptide

Thirst

• primary regulator of water intake

• Thirst center located in hypothalamus stimulated by osmolality

Antidiuretic hormone (ADH)

• produced by the hypothalamus and stored in the posterior pituitary gland–osmoreceptors – volume-sensitive receptors –baroreceptors

• Action – slows dilution of urine– constricts arterioles

ADHRelease or Suppression

• ADH released continuously in response to many conditions

• Released– NPO, watery diarrhea, conc. food or fluid intake,

pain, certain medications, stress• Suppressed– hyposmolality of ECF, blood volume,

exposure to cold, acute alcohol ingestion, carbon dioxide inhalation, certain medications, disorders of pituitary

Renin – Angiotensin- Aldosterone Mechanism

• Renin produced by the kidneys• response to renal perfusion• Renin Angiotensin I Angiotensin II• Actions– Stimulate aldosterone release– Na & H2O reabsorption– vasoconstriction

Aldosterone

• hormone secreted by the adrenal cortex• response to – fall in plasma volume blood flow or–decreased sodium level in the ECF

• secretion is stimulated by angiotensin II• Action – conserves body sodium by promoting

potassium excretion from the kidneys, 1.5 to 6 hours for effect

Atrial Natriuretic Peptide (ANP)

• released by specialized cells of the atria of the heart

• Actions– vasodilation–decreases tubular reabsorption of

sodium – suppresses serum renin–decreases aldosterone release–decreases ADH release

Test your understanding (#1)

• If you were walking across the desert with an empty canteen, the amount of ADH secreted would be?– A. increased– B. decreased– C. stay the same

WHY?

Test your understanding (#2)

• The action of colloid osmotic pressure involves___________________.– A. Pushing fluid out of capillaries– B. An increase in ADH secretion– C. The pulling power of proteins

Test your understanding (#3)

• When a person’s blood pressure drops, the kidneys respond by_________.– A. Secreting renin– B. Inhibiting aldosterone– C. Slowing the release of ADH

Test your understanding (#4)

• Giving a hypertonic IV may cause too much fluid to be:– A. Pulled from the cells into the

bloodstream– B. Pulled out of the bloodstream

into the cells

Nursing Assessment of Fluid Balance

– Height and weight • Changes in daily weight good indicator of fluid

losses or excesses–One liter of water weighs approximately 1

kg (2.2 lbs)–1 lb corresponds to about a change of 500 ml

History

• Tightness of clothing, rings, and shoes

• Any sensation of palpitations or any lightheadedness on moving from lying to sitting or standing

• Abnormal or excessive fluid losses or gains

History cont.

• chronic or recent acute illnesses

• recent surgeries

• medications

• urine output

• recently engaged in strenuous exercise

• environment

Nursing Assessment for Homeostasis

• Perfusion• Oxygenation• Nutrition• Elimination• Cognition• Neural Regulation

Perfusion Assessment

Fluid Deficit• pulse rate• thready pulse quality• BP• postural hypotension• flat neck and hand veins in

dependent positions• diminished peripheral pulses,

weaker and easier to block• delayed capillary refill• mouth dry with fissures and

paste-like coating• poor skin turgor

Fluid Excess

• pulse rate• bounding pulse quality• peripheral pulses full• BP• pulse pressure• central venous pressure• distended neck and hand veins• engorged venous varicosities• S3 gallop• edema

Fluid Deficit or Excess?

Oxygenation assessment

Fluid Deficit

• rate• depth• When accompanied by

acidosis (Kussmaul breathing) – deep and rapid

Fluid Excess• rate• shallow respirations• dyspnea increases with

exertion or in the supine position

• moist crackles present on auscultation

Nutrition/Elimination assessment

Fluid Deficit• motility • diminished bowel sounds• constipation• Thirst• Weight loss• Anorexia• Nausea & vomiting• urine output

Fluid Excess• motility• Weight gain• Anorexia• Nausea & vomiting• urine output• nocturia

Cognition/Neural regulation assessment

Fluid Deficit• CNS activity

– flat affect at first – – progresses to apprehension,

restlessness, lethargy, confusion

– If circulation to cerebral tissues so impaired – delirium and coma

Fluid Excess• altered level of

consciousness• headache• visual disturbances• skeletal muscle weakness• paresthesias

Risk Factors for Changes in Fluid Balance

• Nutritional issues• Lifestyle• Social/Spiritual/Cultural risk factors• Medical Therapies• Chronic or recent acute illnesses

Lifespan Considerations regarding Fluid Balance

• Infants and young children– greater percentage of water than adults– greater water needs, higher risk for fluid

volume deficits– aren’t able to independently respond to thirst

• Elderly – decreased thirst sensation– higher percentage of fat (less water)– changes in the kidney which affects the ability

to concentrate urine

Labs tests (Serum)

• Serum osmolality• Hematocrit• Blood Urea Nitrogen (BUN) • Serum creatinine• Serum electrolytes• Serum Albumin• Serum glucose

Labs tests (Urine)

• Urine specific gravity (1.003-1.030)• Urine osmolality

• Increased– fluid volume deficit– amounts of glucose or protein

• Decreased– fluid volume excess – diabetes insipidus

Nursing Diagnoses for Fluid Imbalance

• There are two types of fluid imbalances– isotonic imbalances where fluids and electrolytes are lost or

gained in equal amounts– fluid imbalances with abnormal osmolarity which are caused by

loss or gain of water

• Fluid volume deficit– Hypovolemia (Isotonic)– Dehydration (Hypertonic)

• Fluid volume excess– Hypervolemia (Isotonic)– Overhydration (Hypotonic)

Patient Outcomes

• The patient will have a balanced fluid level, prior to discharge, as shown by: –electrolyte lab values WNL–a balanced I&O for 48 hours–a stable daily weight x 2 days–Patient stating symptoms are resolving

Collaborative Care Planning

• Nutritional Consult

• Occupational Therapy Consult

• Case Management/Social Work Consult

Nursing Interventions for Homeostasis – Fluid Balance

– Prevent Imbalance• Avoid potential causes• Teach patient prevention methods

– Identify fluid imbalance(deficit or excess)

– Fluid management– Drug therapy – Manage other related Nursing Diagnoses– Monitor I&O, weight

Fluid volume deficitHypovolemia (Isotonic)

• Water and dissolved electrolytes are lost in equal proportions– loss of isotonic fluids from ECF compartment – osmolarity remains normal– no fluid shift between compartments – decreased circulating blood volume and

inadequate tissue perfusion

Causes of Hypovolemia

• Hemorrhage• Vomiting/Diarrhea • Burns• Ileostomy/Cecostomy• Profuse salivation or diaphoresis• Frequent enemas • Severe wounds • Long-term NPO/GI suction • Diuretic therapy

COMPENSATORY ACTIONS for hypovolemia

Increased venous constriction

Increased cardiac contractility

Increased arterialconstriction

Increased venousreturn

Increased HRIncreased stroke

volume

Increasedperipheralresistance

Increased cardiac outputIncreased mean arterial pressure

RESTORATIVE ACTIONS for hypovolemia

Increased reninsecretion

Increased renalsodium reabsorption

Increasedangiotensin II

formationIncreased effectivecirculating volume

Increased aldosteronesecretion

Fluid volume deficit Dehydration (Hypertonic)

• Water loss exceeds electrolyte loss– alterations in concentrations of specific plasma

electrolytes– increases the osmolarity (primarily sodium) of the

remaining plasma – fluids to move from the ICF into the plasma and

interstitial fluid spaces– fluid shift results in cellular dehydration and

shrinkage

Hypertonic dehydration cont.– Fluid shift also causes plasma volume to

approach or perhaps exceed normal levels– No hypovolemic shock symptoms – Excitable membrane activity and cardiac

contractility are affected – Compensatory mechanisms for hypertonic

dehydration occur in response to the ECF osmolarity

Causes hypertonic of dehydration• Watery diarrhea Systemic infection• Renal failure Fever• Diabetes insipidus Ketoacidosis• Tube feedings Dysphagia• Impaired motor function • Impaired thirst• Unconsciousness• Hyperventilation• Excessive fluid replacement (hypertonic)• Excessive sodium bicarbonate administration

COMPENSATORY ACTIONS for hypertonic dehydration

• Decreased ECF volume• Increased ECF osmolarity

Fluid shift(ICF to ECF)

Cell shrinkage

Increased ADHsecretion

(posterior pituitary

Increased renalreabsorption of water

Decreased urinaryoutput

Increased ECF volume

Stimulation of osmoreceptors(hypothalamus

Activation of thirst reflex

Increased oralwater intake

Health Promotion teachingFluid volume deficit

Teaching should include:• maintaining adequate fluid intake and

increasing fluids with activity, warm weather, and fever

• the increased risk for fluid volume deficit in the elderly due to decreased total body water and decreased thirst

• the increased risk for fluid volume deficit with illness

• to monitor a daily weight.

Fluid volume excessHypervolemia

• excessive fluid in ECF compartment• osmolarity remains normal• only ECF expanded – no fluid shift• Effects - severe circulatory overload,

interstitial edemaCauses - poorly controlled IV therapy, renal

failure, long-term corticosteroid therapy

Compensatory actions for hypervolemia• Circulatory overload

secretion of ADH and

aldosterone

mean arterial pressure venous return

cardiaccontractility

Fluid shift(plasma to

interstitial space)

Formation ofvisible edema

secretionof natriuretic

peptide

renal excretionof sodium and water

Normal plasma volume

Fluid volume excess HYPOTONIC overhydration

• osmolarity of ECF • hydrostatic pressure • excessive fluid moves into the ICF space • all body fluid compartments expand• Effects - polyuria, diarrhea, nonpitting edema,

cardiac dysrhythmias associated with electrolyte dilution, projectile vomiting

Causes - CHF, poorly controlled IV therapy, irrigation of wounds and body cavities with hypotonic solutions, syndrome of inappropriate antidiuretic hormone (SIADH)

Health Promotion teachingFluid volume Excess

Teach the patient: • to avoid salt if indicated • to monitor a daily weight• to monitor daily fluid intake and limit if

indicated

IV Fluids & Tonicity

• Measurement of osmotic pressure of a solution

• Compares concentration of solutes in the solution to those in the serum– Isotonic– Hypertonic– Hypotonic

Fluid Concentrations

• Osmolality – concentration of molecules per kilogram of solution(weight)– Normal for serum 280-300 mOsm/kg

• Osmolarity –concentration of molecules per liter of solution (volume) – Used when describing IV fluids

Isotonic

Hypertonic

Hypotonic

IV Fluid Tonicity

Isotonic DD55WW0.9% NaCl0.9% NaClDD55W in 0.25% NaClW in 0.25% NaClRinger’s LactateRinger’s Lactate

Hypertonic DD55W in 0.45% NaClW in 0.45% NaClDD55W in 0.9% NaClW in 0.9% NaClDD1010WWDD55W in RLW in RL

Hypotonic 0.45% NaCl0.45% NaCl

IV solution effects on RBCs

IV fluid replacement

– Hypovolemia• tx with isotonic fluids

– Dehydration with elevated sodium level• tx with hypotonic fluid

– Loss of solutes• tx with hypertonic fluid

Drug Therapies

Fluid Deficit• Antidiarrheal• Antimicrobial• Antiemetics• Antipyretics– Oral Rehydration Solutions

Fluid Excess• Diuretics

Nursing Diagnoses related to Fluid Balance

• Cardiac Output, altered• Oral Mucous Membranes, altered • Potential for Dysrhythmias• Constipation• High Risk for Injury• Knowledge Deficit • High Risk for Impaired Skin Integrity• Ineffective Airway Clearance• Potential for Hypovolemic Shock• Impaired gas exchange• Ineffective tissue perfusion• Potential for electrolyte imbalances

Nursing Process-Evaluation• ongoing process• outcome criteria provide measures for

determining effectiveness of care• determine whether goals have been met,

partially met, or not met at all– if not been met - re-evaluate – new assessment needed to alter the plan

• The patient, family, and the health care team participate in the evaluation process, when appropriate.