Fluid & electrolytes

Fluid & Electrolytes Acid –Base Balance

Chapter 4

Amount/Composition of Body Fluids• 60% of body weight = fluid.• Age, gender, body fat influence amount.• Body fluid is divided into 2 compartments• Intracellular space (2/3) – fluid in cells• Extracellular space (1/3) – fluid outside of cells• Intravascular space (fluid in blood vessels: plasma) 3.5L• Interstitial space (lymph fluid) 10L• Transcellular fluid spaces (cerebrospinal, pericardial, synovial, intraocular) 1L

Electrolytes: Active chemicals in body fluidsCations: Positively Charged• Sodium • Potassium • Calcium • Magnesium • Hydrogen

Anions: Negatively Charged• Chloride• Bicarbonate• Phosphate• Sulfate• proteinate

Vocabulary• Diffusion: The natural tendency of a substance to move from an area

of high concentration to one of lower concentration.• Hydrostatic pressure: the pressure exerted by the fluid on the walls of

the blood pressure by the heart• Oncotic pressure: Pressure exerted on the capillaries primarily by

albumin.• Osmolality: The concentration of fluid that affects the movement of

water between fluid compartments by osmosis.• Osmosis: The movement of water caused by a concentration gradient.• Tonicity: The ability of all solutes to cause an osmotic driving force

that promotes water movement from one compartment to another.

Average Daily I & O (Adult)

Average Intake = 2600 ml/day

• Oral Liquids = 1300 ml• Solid Foods = 1000 ml• Oxidation = 300 ml

Average Output = 2600 ml/day

• Kidneys (urine) = 1500• Skin (perspiration) = 600• Lungs (respiration) = 400• GI Tract (feces) = 100

Sensible vs. Insensible LossSensible Loss: Fluid loss that can be measured

• Urination• Defecation• Bleeding• Wound drainage• Gastric drainage• Vomiting

Insensible Loss: Fluid loss that cannot be measured• Perspiration• Respiration• Changes in humidity levels,

respiratory rate and depth, and fever affect insensible loss

Homeostasis • Organs involved in homeostasis include:• Kidneys• Lungs• Heart• Adrenal glands• Parathyroid glands• Pituitary glands

Hypovolemia (fluid volume deficit)

• FVD occurs when loss of ECF exceeds intake of fluid. • Hypovolemia or FVD ≠ dehydration - Dehydration is loss of H2O only!!• Causes:

• Vomiting/Diarrhea• GI suctioning• Sweating• Decreased intake

• Risk Factors:• Diabetes insipidus• Adrenal insufficiency• Osmotic diuresis• Hemorrhage• 3rd spacing• Coma

Hypovolemia (fluid volume deficit)

• Signs (Manifestations):• Acute weight loss• Decreased skin turgor• Oliguria• Concentrated urine w/high specific gravity• Weak rapid pulse• Flattened neck veins• Decreased central venous pressure• Elevated BUN out of proportion to creatinine (>20:1)

Hypervolemia(fluid volume excess)

• Isotonic expansion of the ECF caused by:• Abnormal retention of water AND sodium. (proportionately)

• Occurs secondary to retention of Na+ • Causes:• Fluid overload • Diminished function of homeostatic mechanisms• Cirrhosis, heart/renal failure• Excessive table salt

Hypervolemia(fluid volume excess)

• Manifestations: • Weight gain• Edema• Polyuria• Distended neck veins• Crackles in lung fields SOB/wheezing• Tachycardia• Increased blood/pulse pressure• Increased central venous pressure

Sodium (135-145 mEq/L)Hyponatremia• Causes:• ↑ Vasopressin/ADH• SIADH• Adrenal Insufficiency• Diuretics• Hypervolemia• Liver Failure• Heart Failure• Psychogenic polydipsia

Hypernatremia• Causes:• Dehydration/Hypovolemia• Diabetes Insipidus• Ingestion/Infusion of Hypertonic

Solutions• Cushing’s Syndrome• Hyperaldosteronism• Loss of pure water (excessive

sweating or respiratory infections)

Sodium (135-145 mEq/L)Hyponatremia• Signs & Symptoms:• Nausea/Vomiting• Headache• Malaise• Confusion• Diminished Reflexes• Confusion• Convulsions• Stupor or Coma

Hypernatremia• Signs & Symptoms:• Thirst• Lethargy • Edema• Decreased vascular volume• Neurologic Dysfunction (d/t dehydration of brain cells)

• Irritability• Weakness• Seizures• Coma

Sodium (135-145 mEq/L)Hyponatremia

• Treatment:• Oral/IV Na+ (3%) supplements• Encourage foods high in Na+• Fluid restriction • Monitor I&Os• Daily weights• Monitor Neuro Status• Monitor for Arrhythmias

Hypernatremia• Treatment:• Hypotonic IV Fluids • Encourage foods low in Na+• Push P.O. Fluids• Monitor I&Os• Monitor Neuro Status• Monitor for Arrhythmias

Potassium (3.5 – 5.0 mEq/L)Hypokalemia• Causes:• Increased Urine Output • Malnutrition• Vomiting and/or Diarrhea• Hypomagnesemia• DKA

Hyperkalemia• Causes:• Renal Failure• Meds (ACEIs, ARBs, K+ sparing

diuretics, NSAIDs)• Addison’s Disease• Aldosterone Insufficiencies• Digoxin Overdose• Beta-Blocker Therapy

Potassium (3.5 – 5.0 mEq/L)Hypokalemia• Treatment• Oral/IV Potassium Chloride

Replacement• D/C or adjust meds causing K+• Reverse alkalosis, if cause• Monitor closely for arrhythmias• Monitor Respiratory Status• Monitor LOC• Monitor GI symptoms

Hyperkalemia• Treatment:• Medications: (D/C meds that may

cause hyperkalemia)• Restrict foods with K+• Dialysis for renal failure • Monitor closely for arrhythmias• Monitor Blood Pressure• Monitor GI symptoms

Calcium (9.0 – 10.5 mg/dL)Hypocalcemia• Causes• Inadequate calcium intake (ETOH,

malnutrition)• Increased calcium loss (pancreatic

insufficiency)• Malabsorption of calcium• Decrease in serum protein levels• Increased binding of calcium

Hypercalcemia• Causes:• Malignancy• Hyperparathyroidism• Prolonged immobilization• Milk-alkali syndrome (Too many

Tums)

Calcium (9.0 – 10.5 mg/dL)Hypocalcemia

• Signs & Symptoms• Tetany• Muscle spasms/convulsions &

seizures• Trousseau’s & Chvostek’s signs• Dyspnea & laryngospasm (stridor)• Torsades de pointes (v. tach)• Hyperactive bowel sounds• Brittle hair/nails

Hypercalcemia• Signs & Symptoms:• Muscle weakness/Incoordination• Anorexia/Constipation• Hypertension• Severe thirst/polyuria• Bone pain/Kidney stones• Psychiatric symptoms• Cardiac standstill > 18 mg/dL

Calcium (9.0 – 10.5 mg/dL)Hypocalcemia

• Treatment:• PO or IV calcium replacement(depends on severity of symptoms or deficiency)• Vitamin D supplement• Encourage foods high in calcium

Hypercalcemia• Treatment:• Hydration• Increased Salt Intake• Diuretics• Dialysis (renal failure)• Glucocorticoids

Magnesium (1.3-2.3 mEq/L)Hypomagnesemia

Causes:• Alcoholism (#1)• Malnutrition/malabsorption• Chronic Diarrhea• Diuretics• DKA• Pancreatitis• Sepsis/burns/hypothermia

HypermagnesemiaCauses:• Renal Failure (#1)• Untreated DKA• Adrenocortical insufficiency• Lithium toxicity

Phosphorus (2.5 – 4.5 mg/dL)Hypomagnesemia

Causes:• Use of nutritional supplements

(enteral or parenteral feedings)• s/sx: neuro/muscular symptoms• Treatment:• Phosphorus supplementation

HypermagnesemiaCauses:• Renal failure (asymptomatic)• Treatment focuses on underlying

disorder

Chloride (97-107 mEq/L)Hypochloremia

Rarely occurs in the absence of other abnormalities.• S/Sx: associated with:• Hyponatremia• Hypokalemia • Metabolic alkalosis.

• Treatment: Correct the cause.

HyperchloremiaCauses r/t :• Hypernatremia • Bicarbonate loss • Metabolic acidosis

Treatment: correct the cause. *Restore fluid, lytes, & acid-base balance.

Acid–Base Balance• Homeostatic mechanisms keep pH within a normal range (7.35 to 7.45)• Buffer systems prevent major changes in the pH of body fluids by

removing or releasing H+

• The major extracellular buffer system is the bicarbonate–carbonic acid buffer system

• The kidneys regulate the bicarbonate level in the ECF• The lungs, under the control of the medulla, regulate the CO2 and the

carbonic acid content of the ECF

Metabolic Acidosis (Base Bicarbonate Deficit)• pH is >7.45 and PaCO2 is <35 mm Hg• Always caused by hyperventilation• Signs consist of lightheadedness due to vasoconstriction and

decreased cerebral blood flow, inability to concentrate, numbness and tingling from decreased calcium ionization, tinnitus, and sometimes loss of consciousness• Treatment depends on the underlying cause of respiratory alkalosis

Arterial Blood Gases: Blood gas analysis is often used to identify the specific acid–base disturbance and the degree of compensation that has occurred