Fluid and Electrolyte Balance: A Summary of Concepts and Assessment PDF

An electrolyte is defined as a substance that develops an electrical charge when dissolved in water. Examples of electrolytes are sodium, potassium, calcium, chlo-ride, bicarbonate, and magnesium. When these substances are dissolved in water, they break up into small particles called ions, which hav...

An electrolyte is defined as a substance that develops an electrical charge when dissolved in water. Examples of electrolytes are sodium, potassium, calcium, chlo-ride, bicarbonate, and magnesium. When these substances are dissolved in water, they break up into small particles called ions, which have either a positive (+) or a negative (-) charge. Examples of anions are chloride (CI), bicarbonate (HCOz), and phosphate (HPO,-)? Osmolality refers to the concentration of a solution determined by the number of dissolved particles per kilogram of water. A higher osmolality means that the concentration of salt, or any other solute, is higher in the water because the solution contains less water, Hormones: Aldosterone is released by the adrenal glands in response to the hormone renin. Aldosterone acts on the kidney tubules to increase the reabsorption sodium and decrease the reabsorption of potassium. Because the retention of sodium causes water retention, aldosterone acts as a volume regulator. ADH is produced by the hypothalamus and is se-f creted into the general circulation by the posterior pituitary gland. It causes the capillaries to reabsorb more water so that urine is more concentrated and less volume is excreted. Vital signs: Assessment of pulse, respiration, temperature, and blood pressure can detect indicators/ of changes in both fluid and electrolyte balance, Blood pressure is directly related to blood volume/Also excess fluid volume can lead to heart failure and pulmonary edema with shortness / of breath. PULSE - Increased rate with fluid volume deficit, sodium deficit, or magnesium deficit. - Weak quality, irregular rhythm, and rapid rate suggest severe potassium excess or sodium deficit. - Bounding quality with fluid volume excess, which often results in circulatory overloads RESPIRATION - Fluid volume excess can cause pulmonary edema with dyspneal and tachypnea! - BLOOD PRESSURE - \* A fall in systolic pressure of more than 20 mm Hg when the patient changes from the lying to the standing positiont or from the lying to the sitting position usually indicates fluld volume deficit? - Fluid volume excess that expands blood volume raises the blood pressure! Clear, pale urinerin a healthy person suggests the excretion ! of excess water whereas dark, concentrated urine indir cates that the kidneyslare retaining water. Measurement of body weight is a good indicator of fluid loss or retention (Box 6.3). One liter of fluid/ weighs 2.2 Ib. Therefore, retention of 1 liter of fluid is reflected as a weight gain of 2.2 lb (1 kg). Soft eyeballs and sunken eyes accompany a severe fluid volume deficit Puffy eyelids and fuller cheeks suggest excess fluid volumé. Pitting edemalis evaluated (on a four-point scalé, ranging from 1+ edema (barely detectablé pit) to 4+ edema (deep and persistent pit that is apr proximately 1 inch or 2.54 cm deep). Distention of the jugular veins can indicate excess fluid® volume. Inspect the neck veins by having the patient recline with the head of the bed elevated at a 30- to 45-degree angle, If the jugular veins can be seen more! than 3 cm above the sternal angle, then excess fluid volume is most likely present. Urine specific gravity (Sp) is a measure of urine con centration. In most instances, normal urine SpGris between 1.016 and 1.022 in adults. A high Sp indicates that the urine is highly concentrated, usually as a result\'of deficient fluid volume.! A low SpG indicates that the urine contains a large amount of water in relation to solutes, usually as a result of excess fluid volume. Dilute urine has a low osmolality and generally ret flects renal excretion of excess water! Low osmolality is also apparent when kidneys are unable to conserve water by concentrating urine. Concentrated urine has a high osmolality and generally indicates renal conserva-l tion of water. It can also be present when the kidneys are failing because the volume of urine secreted declines, Urine creatinine clearance Urine creatinine clearance tests are used to detect glomerular damage in the kidney. A 24-hour specimen is required, The patienttis instructed to void, discard the specimen, record the time, and start collecting allr urine thereafter for 24 hours? The specimen must be refrigerated! During the specimen collection period, the patient should maintain good hydration, should not engage in vigorous exercise, and should avoid high-protein foods, coffee, tea, and cola drinks. Blood urea nitrogen (BUN) provides a measure of renal function. Normal is 5 to 20 mg/dis for adults under 60 years of age and 8 to 23 mg/dL for adults over 60 years of age. A high BUN is associated with deficient fluid volume and possibly impaired renal function, conversely, a low BUN is associated with excess fluid volume.! Albumin is a plasma protein that helps\'to maintain blood volume by creating colloid osmotic pressure! The normal range for serum albumin is 3.5 to 5.5 g/ dL. Low serum albumin allows water to shift into the interstitial compart-ment, which reduces blood volume and creates edema. Fluid volume deficit occurs when water is less than nort mal in the body signs and symptoms of fluid volume deficit vary depending on how suddenly the deficit develops and how body attempts to compensate for fluid volume deficis by decreasing urine output. The heart rate increases to maintain blood flow to body tissues, The blood pressurp may fall because of the reduced blood volumel An increase in body water is called fluid volume excess. Fluid volume excess may result from renal or cardiac failure with retention of fluid, increased production of ADH or aldo-sterone, overload with isotonic intravenous fluids, or the administration of 5% dextroselin water (DgW) after surgery or trauma! The body attempts to compensate for fluid volume excess by increasing the filtration and excretion of sodium and water by the kidneys and decreasing the production of ADH. Severe fluid volume excess can cause or aggravate heart failure and pulmonary edema, NURSING CARE OF THE PATIENT WITH HYPOKALEMIA When a patient has hypokalemia, monitor for decreased bowel sounds, a weak and irregular pulses decreased reflexes, and decreased muscle tone. Monitoring the heart rate and rhythm of patients taking digitalis is especially important because hypokalemia increases the risk of digitalis toxicity, Cardiac monitors may be used to detect dyschythmias. Hyperkalemia is a serious imbalance because of the potential (for life-threatening dyshythmias! Neuromuscular effects are muscle cramps and weakness and paresthesia / (a tingling sensation), Caretully monitor the flow rate of intravenous fluids, which should not exceed 10 mEq/h of potassium chloridé through peripheral veins. Examine the infusion site because potassium is very irritating to subcutaneous tissues. Extravasation can cause serious tissue damage. Screen the results of laboratory studies. Because serum potassium levels greater than 5.0 mEq/L can cause cardiac arrest) immediately report the results to the physician and anticipate an order for the patient to be placed on cardiac monitoring and a change in the potassium supplement order. The normal acid-base balance is maintained by three primary, complex mechanismS: (1) buffers) \(2) respiratory control of carbon dioxid, and (3) renal regulationio HCO,? To maintain body fluids in the normal pH range, the blood buf fers circulate throughout the body in pairs, acting as sponges to soak up hydrogen ions. One of the buffers takes away a hydrogen ionif a fluid is too acid and one of the buffers gives an ion if the fluid is too alkaline. The lungs and kidneys are the next line of defense alter the blood buffers for maintaining acid-base balance. The lungs are primarily responsible for the regulation of carbon dioxide/in the blood, which is controlled by the raté and depth of respirations Carbonic acid in the alveolar capillaries breaks down into water and carbon dioxide, which is eliminated through exhalation Deep, rapid breathing eliminates excess carbon dioxide, thereby reducing extracellular fluid acidity. Shallow, slow respirations reduce the lossiof carbon dioxide, thereby increasing extracellu-lar acidity. If the pHlof the blood becomes too high or too low, the respiratory center in the brain sends signals to the lungs to increase or decrease respirations to either \"blow off\' or retainithe appropriate amount of carbon dioxide. The kidneys act as the metabolic regulators of pH by excreting acids or bases as needed. Renal regulation of bicarbonate and excretion of hydrogen ions are the chief means of regulating acid-base balance through the kidneys. Bicarbonate is a major acid buffer in the blood and is reabsorbed and produced through the kidneys! If the regulatory mechanisms fail, acid-base imbalances occur. The four major typesofacid-base imbalane. estare (1) respiratory acidosis, (2) respiratory alkalosis, \(3) metabolic acidosis, and (4) metabiolic alkalosis/ Respiratory acidosis occurs when the respiratory system fails to eliminate the appropriate amount of carbon dioxide to maintain the normal acid-base bar-ance. Carbon dioxide is retained, with a resultant act cumulation of carbonic acid and a decrease in bload pH The body responds to respiratory acidosis by stimulating respirations to eliminate excess carbon dir oxide! Acute respiratory acidosis is caused by respiratory diseases such as pneumonia, drug overdose, head int jury chest wall injury, obesity, asphyxiation, drowning, or acute respiratory failure. Interventions for respiratory acidosis are geared fo-ward improving ventilation, which in turn restores; the partial pressurel of carbon dioxide in arterial blood (PaCO?) to normali Focused Assessment The most accurate method of assessing for respira-l tory acidosis is the measurement of the PaCO, level. The PaCO, directly reflects the degree of respira\* tory dysfunction! In addition, observe the patient for signstand symptoms of respiratory distress, including restlessness, anxiety, confusion, and tachycardia. The most common cause of respiratory alkalosis is hyperventilation. Hyperventilation is characterized by rapid or deep respirations that cause excessive amounts of carbon dioxidel to be eliminated through the lungs! One cause (of hyperventilation leading to respirat tory alkalosis is anxiety. Clinical signs and symptoms include increased respiratory and heart rates, an anxious appearance, irritability, dizziness, lightheadedness, muscle weak-ness, and tingling or numbness of the tingers.. In extreme respiratory alkalosis, confusion, fainting, and seizures may occur. To relieve anxiety, give sedatives as ordered and reas sure the patient Encourage the patierit to breathe slowly, which will retain carbon dioxide in the body. Breathing slowlytinto a paper bag raises the PaCO, because the patient rebreathes exhaled carbon dioxide! When breathing stabilizes, allow the patient to have uninterrupted ! rest, because hyperventilation can result in fatigué. Metabolic acidosis occurs when the body retains too many hydrogen ions or loses too many bicarbonate ions. With too much acid and too little base, the pH of the blood falls. Metabolic acidosis leads to hyperventilation because the lungs try to compensate by blowing off carbon dioxide and lowering PaCO, levels, which raises the pHI. Causes of metabolic acidosis are starvation, dehy-dration, diarrhea, shock, renal failure, and diabetici ketoacidosis. Signs and symptoms vary according to the underlying cause and the severity of the acid-base disturbance. However, patients may experience changing levels of consciousness, ranging from fatigue and confusion to stupor and coma, headache, vomiting and diarrhea, anorexia, muscle weakness, and cardiac dysrhythmias. METABOLIC ALKALOSIS Metabolic alkalosis is the opposite of metabolic aci-dosis. It results from an increase in bicarbonate lev, els or a loss of hydrogen ions. Losslof hydrogen iong may be caused by prolonged nasogastrit suctioning, excessive vomiting, diuretics, and electrolyte distuf-bances. Retention of bicarbonate may result from the administration of bicarbonate or massive blood transfusions. Clinical signs and symptoms may include head-ache, irritability, lethargy, changes in level of cong sciousness, confusion, changes in heart rate, slow and shallow respirations with periods of apnea, nausea and vomiting, hyperactive reflexes, and numbness of the extremities.