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Abstract Perioperative fluids are frequently required to correct fluid deficits and compensate for blood loss before and during surgery, Major disturbance in fluid and electrolyte balance can rapidly alter cardiovascular, neurological and neuromuscular functions of the body. Therefore clear understanding of normal water and electrolyte physiology, body fluids compartments and their anesthetic implications is essential for Perioperative care and management of hemodynamic instability. Movement of water between compartments, osmotic pressure, osmolarity, osmolality and tonicity should be taken in consideration. Osmoregulation is essential mechanism to maintain cell volume, in contrast volume regulation is brought about through changes in sodium excretion and is essential requirement to maintain perfusion of the tissues. An accurate method of assessing intravascular volume and preload of the heart is essential component in successful management of patients in the operating room. Clinical assessment of hydration status of the patient by means of body mass, blood indicators , urine color and volume, saliva and skin hydration also for years pressure measurement have represented the only estimation of the volume status in the heart which of course depends on myocardial compliance until invasive hemodynamic monitoring appears such as pulmonary artery catheterization in 1970, measuring important indices e.g pulmonary artery occlusion pressure, cardiac output, mixed venous oxygen saturation which allows more 91 A Rationale Approach to Perioperative Fluid Therapy in Adult Patients accurate determination of the hemodynamic status of critically ill patients than is possible by clinical assessment alone. Intrathoracic blood volume measurements (ITBV) can also reflect accurately intravascular volume , cardiac preload and it has another advantage is that ITBV can be repeatedly determined in spontaneously breathing patients as well as positive pressure mechanical ventilation. Transosphygeal echocardiography can also be used. Volume kinetics means the volume effect of an infusion fluid and is a central issue in fluid therapy, this usually implies how much of infused fluid is retained in the blood stream, basic principles of kinetic analysis such as: using an isotope such as radioiodine labeled human serum albumin to measure the blood volume before and after the infusion. Using physiological end points and also measuring the corresponding change in blood hemoglobin concentration during and after the infusion. Intravenous access establishing is indicated for Perioperative fluid administration and it’s either peripheral intravenous access (PIVs) which remains the safest, easiest and most common means. Veins of upper extremities including those on dorsum of hand ,lateral forearm and antecubital space remains the most sites of cannulation. Or central venous access, which is indicated for administration of specific drugs, heamodialysis, hemodynamic monitoring or inability to attain peripheral IV line. Most common sites are internal jugular vein, subclavian vein and occasionally femoral vein catheter. 9 2 A Rationale Approach to Perioperative Fluid Therapy in Adult Patients Intravenous fluids: include crystalloids, colloids and oxygen carrying plasma expanders. Crystalloid fluids: is a solution of small water soluble molecules that can diffuse easily across semi permeable membranes and are composed of low molecular weight solutes either Ionic e.g (Na+Cl-)or nonionic e.g (mannitol) they are either hypotonic, isotonic and hypertonic crystalloids . The volume effect of crystalloids varies according to its composition. Large volume crystalloid infusion has many drawbacks due to extra vascular accumulation such as delayed healing of anastomosis and wounds, inhibition of gastrointestinal motility, hypercoagulability, lung pneumonia and respiratory problems. It also can alter acid base balance such as saline induced acidosis. Colloids: they are either natural such as albumin or synthetic such as gelatins, dextrans and starches. Oxygen carrying plasma expanders: such as hemoglobin-based oxygen carriers (HBOCs), perfluro-carbon emulsions and liposome encapsulated hemoglobin. In daily practice a combination of measured lost volume and physiological changes is used for the assessment of the fluid status in surgical patients in order to maintain patient’s physiological function and to replace fluid lost with appropriate intravenous fluids. Fluid lost is measured through insensible perspiration which is approximately 10 ml/kg/day in normal conditions plus fasting, urine loss, evaporation loss and third space loss. Intravenous fluid therapy in special situations and the most suitable management, type of fluid should be used in each situation such as hypovolemic shock, trauma and burn also mentioned. A group of recommendations and guidelines for intravenous fluid therapy which should be taken in consideration while managing perioperative surgical patients according to British consensus guidelines. |