Fluid Balance PDF

# Mechanism of Fluid Shifts - Osmotic pressures: The pressure exerted by solutes in solution - Hydrostatic pressure: The pressure exerted by a fluid within a closed system - Membrane permeability - Oncotic pressure: Pressure exerted by proteins and other soluble substance Some of the different fac...

# Mechanism of Fluid Shifts - Osmotic pressures: The pressure exerted by solutes in solution - Hydrostatic pressure: The pressure exerted by a fluid within a closed system - Membrane permeability - Oncotic pressure: Pressure exerted by proteins and other soluble substance Some of the different factors that can cause extracellular and intracellular volumes to change markedly are: ## Factors causing excess of water in the body: 1. Excess ingestion 2. Renal retention of water 3. Intravenous infusion of different types of solutions ## Factors causing loss of water in the body: 1. Dehydration 2. Loss of large amounts of fluid from the gastrointestinal tract 3. Loss of abnormal amounts of fluid by sweating or through the kidneys. **Water moves rapidly across cell membranes and cell membranes are almost completely impermeable to many solutes, such as sodium and chloride** # Clinical Consequences of Fluid Shifts: - Dehydration or Overhydration - Edema - Hemodynamic Instability ## Edema - Is the presence of excess fluid in the body tissues. - **Types of edema:** 1. Intracellular Edema 2. Extracellular edema. - In most instances, edema occurs mainly in the extracellular fluid compartment. # Edema ## Intracellular Edema: - Is presence of large amount of fluid inside the cell. - Three conditions are especially prone to cause intracellular swelling: - Hyponatremia - Depression of the metabolic systems of the tissues - Lack of adequate nutrition to the cells - Inflamed tissues **Pathophysiology:** - Oxygen & nutrients: ATP production - Pumping Na outside the cell: water moves form low area to high areas (cell swelling) cell death. - Cell inflamed: cell membrane permeability large; amount of sodium enter the cell then the flow of water cell swelling & death. ## Extracellular Edema: - Is an excess fluid accumulates in the extracellular spaces. - Two general causes of extracellular edema: - Abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries. - Failure of the lymphatics to return fluid from the interstitium back into the blood. # Assessment: - Vital signs: Monitoring blood pressure; heart rate and respiratory rate for signs of fluid overload or deficit. - Physical examination: Observing for signs of dehydration (e.g., dry mucus membranes; decreased skin turgor) or fluid overload (e.g., edema; jugular venous distension). - Urine output: Tracking urine production can indicate kidney function and fluid status (typically, 0.5-1 mL/kg/hr is considered adequate). ## Conditions that can cause extracellular edema: 1. Increased capillary pressure 2. Increased capillary permeability 3. Decreased plasma proteins 4. Blockage lymph return. # Fluid management - Start with boluses of isotonic Crystalloid solutions (e.g., 1 liters of normal saline) in cases of hypovolemic shock or significant blood loss. - Maintenance fluids: Calculate maintenance needs using formulas like the "4-2-1 rule" (4 mL/kg/hr for the first 10 kg; 2 mL/kg/hr for the next 10 kg; and 1 mL/kg/hr for each additional kg). - Continuous monitoring: Regular assessment of hemodynamic parameters and laboratory values to adjust fluid therapy as needed. # Special considerations: - Patient specific factors: Consider underlying conditions (e.g., Heart failure; liver disease: kidney failure) that may influence fluid management strategies. - Electrolyte monitoring: Frequent checks of electrolyte levels as alterations can occur rapidly during fluid shifts. - Postoperative considerations: Monitor fluid status closely in postoperative patients adjusting intake based on output: overall clinical condition: and any signs of complication. # Concentration - This is measured in terms of: - Osmolality-number of osmoles (particles) per kilogram solution. - Independent of volume and pressure - Osmolarity-number of osmoles per liter of solution - Dependent on volume and temperature and pressure - Tonicity- measure of effective osmolality. # Mole and osmole - Mole: Weight of a substance in grams - Osmole: Expression of Osmotically active particles **Eg: 0.1 mole of glucose has osmolality of 0.1 osmolar, while 0.1 mole of Nacl has osmolality of 0.2 osmolar because Nacl dissociate into 2 active particles** - Urea and alcohol cross membrane very rapidly hence do not affect tonicity; Nacl crosses slowly hence affect tonicity. # Tonicity | Tonicity | mOsm/kg | Outcomes | | ------------- | ---------- | --------------------------------------- | | Hypertonic | > 300 | Cell shrinking-burst | | Isotonic | 275-295 | Normal | | Hypotonic | < 270 | Cell swelling-edema | # Types of fluids: - Colloids - Albumin - Hydroxyethyl starch (HES) - Dextran - Blood and blood products - Crystalloids - Saline - hypertonic, isotonic, hypotonic - Lactated Ringer's solution - Dextrose - Dextrose saline - Special solutions - Potassium chloride or calcium gluconate - Intravenous nutrition # Fluid shifts. - Fluid shifts refer to the movement of fluid between different compartments in the body and are essential to understanding fluid and electrolyte management. - Particularly in surgical patients. - These shifts can significantly influence hemodynamic, hydration status and overall patient outcomes. ## Balance between Fluid Intake & Fluid loss: ### Daily intake of Water: 1. It is ingested in the form of liquids or water in food (2L). 2. It is synthesized in the body by oxidation of carbohydrates, adding about 200 mL/day. ### Daily loss of body water: 1. Insensible water loss (skin, lungs). 2. Fluid loss in sweat. 3. Water loss in feces. 4. Water loss by the kidneys (Urine). # Causes of fluid shift - Bleeding - Vomiting - Diarrhoea - Dehydration: - Excessive loss of water from the body - Causes: - Diarrhea or vomiting (isotonic dehydration) - Fever (hypertonic dehydration) - Excess use of diuretics (hypotonic dehydration) - Overhydration: - Condition characterized by a great increase in the water content of the body. - (Also called hyperhydration, water intoxication, or water poisoning). - Causes: - Heart failure - Renal Disorders - Hypersecretion of antidiuretic hormone. - Intravenous administration of unduly medications and fluids.