Fluid and Electrolytes PDF

FLUID AND ELETROLYTES PROF O.A AKPOR  OBJECTIVES At the end of this unit, you should be able to: Identify body fluid compartment Describe the mechanism regulatory fluid and electrolyte balance Identify the factors affecting fluid and electrolyte balances Explain rou...

FLUID AND ELETROLYTES PROF O.A AKPOR  OBJECTIVES At the end of this unit, you should be able to: Identify body fluid compartment Describe the mechanism regulatory fluid and electrolyte balance Identify the factors affecting fluid and electrolyte balances Explain route by which water and Electrolyte leave and enter the body Describe the types of electrolytes in the body Distinguish between electrolyte balance and imbalance  INTRODUCTION All bodily functions rely on the proper distribution of fluids and electrolytes between the intracellular and extracellular compartments Fluid and electrolyte balance is maintained by the interaction of renal, hormonal, and metabolic mechanisms Imbalances can occur secondary to other disorders or as complications of therapy The major objective of fluid and electrolyte distribution is the replacement for prior deficits and continuing losses, and nutrition  FLUIDS The fluids system plays an important role in the body. The principal functions of body fluids are: 1. Maintains of blood volume 2. Aids digestion 3. Transports material to and from body cells 4. Acts as a medium for cellular metabolism 5. Excretes of waste 6. Regulation body temperature  FLUIDS Water is the largest single constituent of the human body and forms about 50-70% of the total body weight (TBW) of the average young to middle age adult and 75-80% of total body weight of an infant By the age of two, the percentage of total body weight that is fluid is the same as that of a young to middle aged adult (60%). The total body fluid drops about 45-60% in the elderly because of changes on the body tissue.  BODY FLUID COMPARTMENTS In the adult, 60% of body weight consists of water, of which 45% is intracellular fluid (ICF). The remaining 15% is distributed between the intravascular and interstitial compartments and is considered extracellular fluid (ECF) Body fluids are found in two major compartments of the body. These are a. Intracellular fluid b. Extracellular fluid  THE INTRACELLULAR FLUID It is found within the cells of the body It accounts for approximately 40-50% of the total body weight The main electrolyte is potassium (K) and this provides the cells with aqueous medium for its chemical functions  THE EXTRACELLULAR FLUID This is found outside the cells The main electrolyte is sodium (Na) The extracellular fluid is made up of two compartments: a. Interstitial Fluid This is found in the spaces between the cells and accounts for approximately 15% of total body weight of an adult b. Intravascular Fluid This is found in the blood and lymph vessels and makes up about 5% of the total body weight  DISTRIBUTION AND CONCENTRATION OF ELECTROLYTES IN BODY FLUID Distribution and concentration of electrolytes in the body fluids are regulated by: Osmosis Diffusion Active transport Filtration Pinocytosis (absorption of liquids by cells with phagocytic properties such as the macrophage)  OSMOSIS Is the process by which water passes through a semi-permeable membrane from a lower concentrations of solution to higher concentrations This continues until equilibrium is achieved on both sides of the membrane. Simply stated, in osmosis, water passes from a more dilute solution to a more concentrated one, water goes where the electrolytes go  OSMOSIS If blood cells are suspended in an isotonic solution (a solution having the same osmotic pressure as the cells), the osmotic pressure will remain the same inside and outside the cell. In this case, no movement occurs.  OSMOSIS AND DIFFUSION If the blood cells are placed in a hypotonic solution (much less concentrated than the cellular contents), water will flow into the cells until they swell and burst. In a hypertonic solution (more concentrated than the cellular contents), water flows out of the cells and they shrink DIFFUSION: Diffusion is a process whereby molecules move from higher concentrations of solution to lower concentrations Oxygen and carbon dioxide exchange in the lungs occurs through diffusion  ACTIVE TRANSPORT Active transport is a mechanism, still not fully understood, whereby ions move from areas of lesser concentration to areas of greater concentration It involves the release of energy by the action of adenosine triphosphate (ATP), which supplies the necessary “uphill movement,” enabling certain substances to pass through the cell membrane Sodium, potassium, and amino acids are probably carried through all cell membranes by active transport  FILTRATION Filtration is related to hydrostatic pressure produced by the pumping action of the heart. (Hydrostatic pressure is the pressure of water or other liquids) It involves the transfer of both solute and solvent through a permeable membrane from a region of higher hydrostatic pressure to a region of lower pressure An example is the passage of water and electrolytes from the capillary beds to the interstitial fluid PINOCYTOSIS AND PHAGOCYTOSIS Pinocytosis is the process by which substances of higher molecular weight, such as protein, enter the body In this process, the cell membrane folds inward to incorporate the substances In phagocytosis, foreign particles are engulfed or digested by specialized cells called phagocytes COMMON SOURCES OF FLUID AND ELECTROLYTE IMBALANCE 1. Vomiting and Gastric Suction: When the quantity of acidic gastric juices is reduced through vomiting or by gastric suction, a number of vital electrolytes is lost. These usually include hydrogen, chloride, potassium, and sodium. The total amount of fluid in the body is decreased, and the client may develop metabolic alkalosis from the resulting excess of base bicarbonate 1. Vomiting and Gastric Suction contd The symptoms of metabolic alkalosis include: Slow, shallow respiration Muscle hypertonicity and tetany, and Personality changes. The client may become disoriented, irritable, or uncooperative  2. DIARRHOEA, AND OTHER SOURCES OF GASTROINTESTINAL FLUID LOSS In a 24-hour period, 17,000 ml of fluid can be lost through diarrhoea With intestinal suction, 3,000 ml of fluid per day can be lost Prolonged use of laxatives and enemas can result in serious water and electrolyte disturbances 2. DIARRHOEA, AND OTHER SOURCES OF GASTROINTESTINAL FLUID LOSS Gastrointestinal fluids can also be lost through fistulas or drainage tubes Gastrointestinal obstruction also produces fluid loss because the fluids are trapped within the intestine and cannot be used by the body.  OTHER SOURCES OF GASTROINTESTINAL FLUID LOSS In addition to fluid volume loss, gastrointestinal disturbances can result in metabolic acidosis (because the intestinal secretions are primarily alkaline). Symptoms of metabolic acidosis include shortness of breath, deep, rapid breathing, weakness, malaise, and stupor progressing to coma 3. Wound Exudates: This can result in losses of protein and sodium and a deficit in the extracellular fluid volume  4. EXCESSIVE PERSPIRATION This can lead to abnormal losses of water, sodium, and chloride If fluid intake of both water and electrolytes is not continued, the fluid volume and proportion of electrolytes decrease The client with this condition may even develop sodium excess if insufficient water is ingested during a period of heavy perspiration  5. INSENSIBLE Water loss occurs through the lungs and skin It totals approximately 600 to 1,000 ml per day in the average adult If respiratory activity is increased, more water vapour is lost, and if there is damage to the skin, still more loss occurs Because only water, and not electrolytes, is lost through the skin, water deficit and sodium excess will develop  6. HYPERVENTILATION Results in respiratory alkalosis due to excessive elimination of carbon dioxide 7. HYPOVENTILATION: Is more dangerous than hyperventilation, causes retention of excessive amounts of carbon dioxide This condition results in respiration acidosis  ELECTROLYTES Electrolytes are chemicals that when dissolved, dissociate into positively and negatively charged ions (cations and anions). Total cation always equals total anions. They are important constituents of intracellular and extracellular fluids, serving vital functions in maintaining fluid and acid – base balance, neuromuscular excitability, blood clotting, and protein and cellular metabolism  ELECTROLYTES The composition and concentration of electrolytes in each fluid compartment vary Measurement of electrolytes is usually expressed in mill equivalents per liter (mEq/L).  ELECTROLYTES The electrolytes in the body fluid are involved in chemical reaction such as: i. Regulating the permeability of cell membranes thus, controlling the transfer of various materials across the membrane ii. Maintenance of the body acid-base balance iii. Promotion of neuro-muscular irritability by transmission of electrical energy within the body e.g. without calcium muscle contraction cannot occur iv. Maintenance of fluids osmolarity (the osmotic pull of all particles per kg of H2O) MECHANISMS REGULATING FLUID AND ELECTROLYTE BALANCE Proteins and electrolytes are the main forces holding H2O within the various compartments of the fluid system in the body In the intravascular compartments the force is by the serum albumin, whereas in the interstitial fluid is by Sodium (Na+) ions and in the intracellular by potassium  MECHANISMS REGULATING FLUID AND ELECTROLYTE BALANCE These substances exact an osmotic pressure which holds the H2O in their respective compartments For example a patient who has lost a great deal of serum albumin through malnutrition tends to become oedematous, since fluid is drawn from the blood plasma into the intracellular space because the main force holding the H2O in the blood vessels has been lost  MECHANISMS REGULATING FLUID AND ELECTROLYTE BALANCE 1. Kidneys 2. Gastro-intestinal tract 3. Thirst 4. Lungs 5. Skin 6. Hormonal control  1. KIDNEYS This is the most important regulatory mechanism This function is regulated by the action of two hormones – Anti Diuretic Hormone (ADH) which controls H2O reabsorption and Aldesterone which promotes the retention of Sodium (N+) and the excretion of Potasium (K+) Under the influence of these hormones the kidney assists in regulating: a. Total value of extracellular fluid b. Electrolyte concentrate c. Acid-base balance d. Blood pressure  2. GASTRO-INTESTINAL TRACT This is done through the selective reabsorption of water and solutes which occur principally in the small intestine The gastrointestinal tract absorbs about 7-9 litres of glandular and gastrointestinal secretions per day About 100mls of H2O are excreted from the bowel daily, the rest are reabsorbed Both fluids and electrolytes may be lost in considerable quantities in conditions as vomiting and diarrhoea  3. THIRST This is stimulated by a decrease in extracellular fluid volume Thirst indicates a basic physiological need for H2O The thirst mechanism is stimulated by: a. Increase osmotic pressure b. Decrease ECF c. Dry mucous membrane in the mouth  4. LUNGS H2O is lost during expiration and inspiration, although amount of H2O lost is small Whenever respiration increases in rate and depth, the amount of lost H2O via this route increased This is seen in strenuous muscular exercise, fever or any condition in which respiration is increased or when the air that is breathed is very dry 5. Skin: H2O is lost through perspiration  6. HORMONAL CONTROL Three hormones play a particularly vital role in maintaining fluid and electrolyte balances: 1. Antidiuretic hormone (ADH) a. Is produced in the hypothalamus and stored and released from the posterior pituitary gland b. Acts on the renal tubules to retain water and to decrease urinary output 2. Aldosterone a. Is secreted by the adrenal cortex b. Acts on the renal tubules to reabsorb sodium and to excrete potassium c. Increase circulatory volume by reabsorbing water along with sodium. 6. HORMONAL CONTROL CONT 3. Parathormone: a. Produced by the parathyroid glands b. Promotes absorption of calcium from the intestine c. Promotes release of calcium from bone d. Increases the excretion of phosphate ions by the kidneys  FACTORS AFFECTING FLUID AND ELECTROLYTE BALANCE 1. Insufficient intake of fluid 2. Disturbance of the gastrointestinal tract such as diarrhoea and vomiting, gastric suction and wash out 3. Disturbances of kidney function e.g. cardio vascular dysfunction or imbalance in antidiuretic hormone 4. Excessive perspiration and evaporation 5. Lost of body fluid as occurs with haemorrhage, burns and body trauma including surgical trauma  MECHANISM IN WHICH H2O AND ELECTROLYTE ENTER AND LEAVES THE BODY Water enters the body through a. Oral liquids = 1,500ml b. Water in fluids = 700ml c. Water from oxidation = 200ml Total =2,400ml  MECHANISM IN WHICH H2O AND ELECTROLYTE ENTER AND LEAVES THE BODY Water leaves the body by several routes a. Skin diffusion 350ml b. Skin by perspiration 100ml c. Lungs 350ml d. Feaces 200ml e. Kidneys 1400ml = 2,400ml As long as all organs are functioning normally, the body is able to maintain balance in its fluid contents. i.e. the intake of fluid must balance the output  FLUID BALANCE Electrolytes must be balanced within a narrow margin to maintain homeostasis Primary and secondary imbalances exist While primary imbalances occur on their own, secondary electrolyte imbalance occur as a result of another pathophysiologic situation  SODIUM Is the major cation in the ECF: Regulates fluid volume within compartments Is the principal regulator of the osmotic pressure of the ECF Maintains cellular membrane potential (transfers neuromuscular impulses) Maintains blood volume and regulates size of vascular bed Normal level : 135-145mEq/L  SODIUM DEFICIT(HYPONATREMIA) Abnormal decrease in plasma sodium levels: < 135mEq/L. In severe cases: 145mEq/L Serum osmolality: >295mOsm/kg rise CLINICAL MANIFESTATIONS CONT Firm, rubbery tissue turgor (increase in Na draws H2O from ICF) In severe hypernatremia; depression, fatigue and coma Intracranial hemorrhage Oliguria and anuria (increase in ADH)  HYPERNATREMIA INTERVENTIONS AND TREATMENT High oral intake of water to decrease osmolality of ECF Hypotonic IVs Monitor weight Intake and output Inspect oedema: dependent edema (sacrum, feet)  POTASSIUM Potassium is the main cation in ICF Normal concentration: 3.5 to 5.0 mEq/L Functions: Maintains intracellular homeostasis and determines the cells resting membrane potential Helps promote conduction of nerve impulses Promotes skeletal muscle impulses Promotes heart muscle function Catalyzes many reactions and participates in protein synthesis and CHO metabolism Kidney excretes 90 to 95% of all potassium  POTASSIUM CONTD Potassium moves into the cell when glucose is being metabolized Potassium moves out of the cell during strenuous exercise, impaired cell metabolism, cells destruction (burns, major trauma, serious infections, chemotherapy) When potassium is lost, sodium and hydrogen ions shift into the cell to maintain cellular tonicity and cells become more acidic. POTASSIUM DEFICIT ( HYPOKALEMIA) Serum potassium 5.3 mEq/L Hyperparathyroidism(due to excessive parathormone secretion Widespread bone metastasis with calcium resorption Prolonged immobilization: (decreased bone formation and bone resorption) Hypervitaminosis D (increased bone resorption of vit D) Multiple myeloma (bone destruction liberates Ca), CA breast, leukemia, lymphoma Kidney stones: when the rate of demineralization exceeds kidneys excretion of excess calcium. Kidney stones forms  HYPERCALCEAMIA: CLINICAL OBSERVATION Decreased neuromuscular excitability with reduced muscle tone Fatigue Nausea, vomiting anorexia and weight loss Deep bone pain elated to pathological fractures Flank pain (calcium renal stones) Prolonged Q-T interval on ECG  HYPERCALCEAMIA: TREATMENT Promote urinary excretion of calcium: diuretics (Lasix) – Hydration with sufficient fluids (3000 to 4000ml/day) while restricting calcium Synthetic Calcitonin Calcium-free diet Mobilization of an immobilized person Pamidronate (Aredia ) to inhibit osteoclasts for malignancy