Fluid Electrolyte Balance

Normal arterial blood pH range

7.35-7.45

True or false: abnormal pH can lead to death

true

Respiratory actions

rapid pH changes due to quick diffusion of CO2 (minutes to hours)

Renal actions

Regulate hydrogen ion excretion or retention and formation or excretion of bicarbonate ions 

• Slower compensatory mechanism than respiratory (can take up to 3 days)

How is acid-base balance measured?

measured through ABGs (arterial blood gases)

• arterial blood sample (freshly oxygenated blood)

• partial pressure of the gases reflects the overall effectiveness of gas exchange

Normal ABG Interpretation

• Determine if pH is acidosis or alkalotic

• Evaluate the PaCO2 (Respiratory Mechanism, rapid changes)

• Evaluate the HCO3- (Renal Mechanism, slower changes)

• If the pH and PaCO2 are inversely related you have a respiratory problem; if the pH and HCO3- have direct correlation you have a metabolic problem

Compensation

• Partially Compensated = pH, PaCO2, and HCO3 are abnormal

• Uncompensated = pH and only one other variable are abnormal

• Compensated = pH is normal

Metabolic acidosis clinical manifestations

• Kussmaul breathing (rapid & vigorous breathing)

• Capillary dilation (flushing of the skin)

• Dehydration

• Abd pain, n/v

Metabolic Acidosis Causes

• Severe infection

• Diabetic acidosis

• Tissue trauma

• Shock

• Renal failure 

• Heart failure

• Severe diarrhea or starvation

Metabolic Alkalosis Clinical Manifestations

• Shallow breathing

• Tetany-like sx

• Confusion/irritability

• Vomiting 

Metabolic Alkalosis Causes

• Hyperemesis

• Gastric suctioning

• Peptic ulcers

Respiratory Acidosis Clinical Manifestations

• Dyspnea/impaired gas exchange 

• Flushing/warm skin

• Tachycardia/weakness

Respiratory Acidosis Causes

• Pneumonia

• COPD

• Chest injuries

• Opioids

Respiratory Alkalosis Clinical Manifestations

• Rapid shallow breathing

• Tetany-like sx

• Palpations/vertigo

Respiratory Alkalosis Causes

• Fever 

• Pain

• Brain tumor 

• Anxiety

• Drug toxicity

• Excessive exercise 

What regulates CO2?

Respiratory rate/depth

• As CO2 increases in the blood, the respiratory rate increases to reduce CO2 levels

  • This leads to decreased H2CO3, and the blood pH increases

Respiratory assessment 

• Respiratory rate and depth

• Cognitive function

• Dizziness

Respiratory interventions

• Altered respiratory rate

• Administration of oxygen

• Administration of bicarbonate

Respiratory evaluation

• Improved pH

• Respiratory rate/depth

Intracellular

• ICF is critical for maintain cell size

• 70% of total body fluid

  • about 40% of adult body weight is from ICF

Extracellular

• 30% of total body fluid and 20% of body weight

• Intravascular fluid = plasma of the blood → blood volume, impacts HR/BP

• Interstitial fluid = surrounds cells

• Trans Cellular = cerebrospinal, pleural, peritoneal, synovial, digestive, secretions, sweat 

Isotonic

When the osmolarity is equivalent to plasma

• Isotonic fluid remains in the intravascular space 

Hypertonic

When osmolarity is greater than plasma

• Hypertonic fluids pull water from the cells and into the intravascular spaces

  • cells shrink

Hypotonic

When osmolarity is less than plasma

• Hypotonic fluids move from the intravascular space to the ICF 

  • Cells swell

Isotonic solutions

• Normal saline (0.9% NaCl)

• Lactated Ringer’s (LR)

Hypertonic solutions

• 5% dextrose in lactated ringer’s (D5LR)

• TPN

Hypotonic solutions

• Half strength normal

• Saline (0.45% NaCl)

How is fluid balance achieved?

• Oral intake of fluid matches the output of the kidneys

  • 2600 mL

• Output can be sensible or insensible

  • Insensible can be hard to measure (sweat, respiratory sputum)

Organs and systems that manage fluid and electrolyte balance

• Kidneys

• Heart and vascular

• Lungs

• Nervous system

• GI track

Hormonal control of fluid and electrolyte balance

• Adrenal gland

• Thyroid gland

• Pituitary gland

• Parathyroid gland 

Fluid volume deficit hypovolemia

loss of fluid and solutes from

Dehydration

Loss of total body water results in increased serum sodium

Fluid volume excess

• Retaining sodium and water in ECF

  • Intravascular excess - hypervolemia

  • Interstitial excess - edema

Third spacing

• Fluid moves into transcellular compartment (pleural, peritoneal, pericardial, joints, bowel) or interstitial spaces

  • Causes hypovolemia (fluid is unavailable for use)

Electrolytes

basis for chemical interactions in the body necessary for metabolism and oter functions

Cations

sodium, potassium, calcium, hydrogen, magnesium

Anions

• Chloride, bicarbonate, phosphate 

-natremia

sodium 

-kalemia

potassium

-calcemia

calcium

-magnesemia

magnesium

-phosphatemia

phosphorus

-chloremia

chloride

Hyponatremia causes

• Diuretics

• GI losses

• Excessive water intake 

Hypernatremia causes

• Poor oral water intake

• Increases fluid losses (sweat/burns)

• Increased salt intake

• Enteral feeding without water 

Hyponatremia sx

• N/V

• muscle cramps

• hypotension

• edema

• weakness

• confusion

• lethargy* 

• twitching*

• seizures*

• coma*

Hyponatremia tx

• measure I&O 

• encourage sodium rich foods

• seizure precautions

• careful IV replacement 

Hypernatremia sx

• thirst

• dry mucous membranes

• hallucinations*

• lethargy*

• seizures*

• coma*

hypernatremia tx

• gradual rehydration

• measure I&O

• sodium restricted diet 

Hypokalemia sx

• vomiting

• diarrhea

• GI losses

• diuretics

• poor intake (anorexia, ETOH, polyuria)

Hypokalemia causes

vomit, diarrhea, diuretics, poor intake

Hypocalcemia tests

• Chvostek’s 

• Trousseau 

History/risk factors

• Illness (diabetes, HF, renal failure)

• Abnormal fluid losses (vomiting, diarrhea, draining wounds), burns, trauma, surgery

• Medications (laxatives, diuretics)

• Weight changes

• Lab studies (CBC, electrolytes, BUN, creatinine, specific gravity)

Skin

• Turgor

• Mucous membranes

Cardiac

• Edema

• Heart rate

• Rhythm

• Blood pressure

• JVD

Respiratory

Lung sounds

Neuro-musculoskeletal

• Mental status

• Reflexes

• Muscle tone

Nursing Diagnoses

• Excess fluid volume

• Deficient fluid volume

• Impaired oral mucous membrane integrity r/t fluid volume deficit 

Prevention

• Education (s/s of dehydration, individual risk factors)

• Monitor I&O, daily weight, labs 

Treatment

Fluid management

Encourage or restrict oral fluid intake

• (+) offer preferred fluids, set goals, always have some fluids available for the patient

• (-) fluid restriction, set goals, use smaller cups, provide ice chips instead, avoid salty foods, keep drinks out of sight, good oral hygiene, communicate with other caregivers

Electrolyte Management

• Administer replacement electrolytes as ordered

  • Be aware of the administration instructions; many IV preparations must be diluted and given very slowly (over hours)

Medication management

Diuretics may be ordered to assist with fluid or electrolyte balance