Total Body Water (TBW)<br />• Varies with age, gender<br />• 55% body weight in males<br />• 45% body weight in females<br />• 80% body weight in infants<br />• Less in obese: fat contains little water<br />Body Water Compartments<br />• Intracellular water: 2/3 of TBW<br />• Extracellular water: 1/3 TBW<br />- Extravascular water: 3/4 of extracellular water<br />- Intravascular water: 1/4 of extracellular water<br />Blood Volume<br /> <br />Fluid and Electrolyte Regulation<br />• Volume Regulation<br />- Antidiuretic Hormone<br />- Renin/angiotensin/aldosterone system<br />- Baroreceptors in carotid arteries and aorta<br />- Stretch receptors in atrium and juxtaglomerular apparatus<br />- Cortisol<br />• Plasma Osmolality Regulation<br />- Arginine-Vasopressin (ADH)<br />- Central and Peripheral osmo-receptors<br />• Sodium Concentration Regulation<br />- Renin/angiotensin/aldosterone system<br />- Macula Dense of JG apparatus<br />Preoperative Evaluation of Fluid Status<br />• Factors to Assess:<br />- h/o intake and output<br />- blood pressure: supine and standing<br />- heart rate<br />- skin turgor<br />- urinary output<br />- serum electrolytes/osmo-larity<br />- mental status<br />The following factors must be taken into account:<br />1- Maintenance fluid requirements<br />2- NPO and other deficits: NG suction, bowel prep<br />3- Third space losses<br />4- Replacement of blood loss<br />5- Special additional losses: diarrhea<br />Intravenous Fluids:<br />• Conventional Crystalloids<br />• Colloids<br />• Hypertonic Solutions<br />• Blood/blood products and blood substitutes<br /><br />Crystalloids: - Combination of water and electrolytes<br />- Balanced salt solution: electrolyte composition and osmolality similar to plasma; example: lactated Ringer’s, Plasmlyte, Normosol.<br />- Hypotonic salt solution: electrolyte composition lower than that of plasma; example: D5W.<br />- Hypertonic salt solution: 2.7% NaCl.<br />Hypertonic Solutions<br />• Fluids containing sodium concentrations greater than normal saline.<br />• Available in 1.8%, 2.7%, 3%, 5%, 7.5%, 10% solutions.<br />• Hyperosmolarity creates a gradient that draws water out of cells; therefore, cellular dehydration is a potential problem.<br />Colloids<br />• Fluids containing molecules sufficiently large enough to prevent transfer across capillary membranes.<br />• Solutions stay in the space into which they are infused.<br />• Examples: hetastarch (Hespan), albumin, dextran.<br />Clinical Evaluation of Fluid Replacement<br />1. Urine Output: at least 1.0 ml/kg/hr<br />2. Vital Signs: BP and HR normal (How is the patient doing?)<br />3. Physical Assessment: Skin and mucous membranes no dry; no thirst in an awake patient<br />4. Invasive monitoring; CVP or PCWP may be used as aguide<br />5. Laboratory tests: periodic monitoring of hemoglobin and hematocrit<br />Transfusion Therapy<br />- 60% of transfusions occur perioperatively.<br />- responsibility of transfusing perioperatively is with the anesthesiologist.<br /><br />Done by<br />Dr. Sara Kareem<br />