Fluid Replacement

Selection and care of the hydraulic fluid for a machine will have an important effect on how it performs and on the life of the hydraulic components. During the design of equipment that requires fluid power, many factors are considered in selecting the type of system to be used-hydraulic, pneumatic, or a combination of the two. Some of the factors required are speed and accuracy of operation, surrounding atmospheric conditions, economic conditions, availability of replacement fluid, required pressure level, operating temperature range, contamination possibilities, cost of transmission lines, limitations of the equipment, lubricity, safety to the operators, and expected service life of the equipment. 

The composition of body fluids remains relatively constant despite the many demands placed on the body each day. On occasion, these demands cannot be met, and electrolytes and fluids must be given in an attempt to restore equilibrium. The solutions used in the management of body fluids discussed in this chapter include blood plasma, plasma protein fractions, protein substrates, energy substrates, plasma proteins, electrolytes, and miscellaneous replacement fluids. Electrolytes are electrically charged particles (ions) that are essential for normal cell function and are involved in various metabolic activities. This chapter discusses the use of electrolytes to replace one or more electrolytes that may be lost by the body. The last section of this chapter gives a brief overview of total parenteral nutrition (TPN). 

Combined electrolyte solutions are available for oral and IV administration. The IV solutions contain various electrolytes and dextrose. The amount of electrolytes, given as milliequivalents per liter (mEq/L), also varies. The IV solutions are used to replace fluid and electrolytes that have been lost and to provide calories by means of their carbohydrate content. Examples of IV electrolyte solutions are dextrose 5% with 0.9% NaCl, lactated Ringer s injection, Plasma-Lyte, and 10% Travert (invert sugar—a combination of equal parts of fructose and dextrose) and Electrolyte No. 2. 

Once TBW has been restored, the volume of maintenance fluid equals the basal fluid requirement plus ongoing exceptional losses. If the pathophysiologic process leading to TBW depletion has not been identified and corrected (or accounted for in the calculation of maintenance fluid requirements), TBW depletion will quickly recur. To review the concepts involved in the calculation of replacement fluids for a representative patient (see Patient Encounter 2). 

Replace fluids 2-3 L of 0.9% saline over first 1-3 hours (5—10 mLAkg per hour) subsequently, 0.45% saline at 1 50-300 mLAhour change to 5% glucose and 0.45% saline at 100-200 mLAhour when plasma glucose reaches 250 mg/dL (14 mmol/L). 

If we now replace fluid 2 by a PCM, the heat exchanger from Figure 128 becomes a heat storage as shown in Figure 129. To simplify the calculations we first assume that the PCM is everywhere at the phase change temperature... 

Treatment of AP is aimed at relieving abdominal pain and nausea, replacing fluids, minimizing systemic complications, and preventing pancreatic necrosis and infection. 

Implementation of microanalytical devices presents some issues mostly related to the scale of the volumes. In fact, successive reduction in the sample volume may compromise analysis either because the measurement limit of the analytical method is exceeded or because the sample is no longer representative of the bulk specimen. Another drawback for microchip devices is microvolume evaporation of both sample and reagent from the microchip, compromising quantitative determination or inducing unwanted hydrodynamic flows. This problem has been addressed by designing pipetting systems that automatically replace fluid lost by evaporation or by enclosing the chip in a controlled... 

Base fluid administration on calculated maintenance or replacement fluid requirements. 

A febrile person should stay in a cool place and not be covered in thick blankets/quilts. The body can be dapped with water to cool it down. It is very important to drink plenty of liquid to replace fluid loss due to evaporation. Physical strain should be avoided during fever and preferably until a few days after the fever has disappeared. 

Increase fluid intake in patients with upper respiratory allergies to decrease the viscosity of secretions, offset thirst, and replace fluids lost from diaphoresis... 

When a 45-year-old man with severe lithium-induced diabetes insipidus developed hyperosmolar, nonketotic hyperglycemia, it was suggested that poorly controlled diabetes mellitus may have contributed to the polyuria (684). Prior contact with a female patient who had developed hyperosmolar coma secondary to lithium-induced diabetes insipidus (685) allowed physicians 4 years later to treat her safely after a drug overdose and a surgical procedure, by avoiding intravenous replacement fluids with a high dextrose content (despite stopping lithium several years earlier, the patient continued to put out 10 liters of urine daily) (686). 

Factors that put patients at risk of lithium intoxication are those that increase intake (deliberately or accidentally), reduce excretion (kidney disease, dehydration, low sodium intake, drug interactions), or reduce body water (dehydration secondary to fluid restriction, vomiting, diarrhea, or polyuria) (66). Patients with lithium-induced polyuria are at a particular risk of toxicity if their ability to replace fluids is compromised (for example by anesthesia, over-sedation, CNS trauma). 

The ideal artificial tear would reproduce the metabolic, optical, and physical characteristics of natmal tears. Additionally, it would have a long ocular residence time and would contain therapeutic additives to treat primary and secondary damage to the eye. Supplementation of natural tears with a substance that prolongs residence time generally improves tear film breakup time (TBUT) and is superior to tear replacement fluids of low retention time. 

The authors concluded that the most likely cause of renal insufficiency was etherified starch-induced tubulopathy and hypothesized that even low amounts of etherified starch as replacement fluid in plasma exchange can cause renal tubular lesions in patients predisposed for other reasons (such as drugs or renal hypoperfusion) to renal insufficiency. In this context, albumin should be combined with replacement fluids other than etherified starch. 

While a minority of therapeutic agents are inorganic electrolytes, it is nevertheless pertinent to consider the manner of their interaction with water. Electrolytes are, of necessity, components of replacement fluids, injections and eye drops and many other formulations. An increasing number of metal-containing compounds are used in diagnosis and therapy, some of which have interesting solution behaviour. 

Isotonic (0.9%) sodium chloride is used commonly as an intraoperative intravenous (i.v.) replacement fluid in species other than the horse. Isotonic sodium chloride has a higher ratio of chloride to sodium than plasma and, therefore, reduces the strong ion difference and causes mild hyperchloremic acidosis in normal ponies (Gossett et al 1990a). This limits its utility as a resuscitation fluid in the horse, as most horses requiring fluid resuscitation already have acidosis. Isotonic sodium chloride should not be used for resuscitation unless indicated by measured electrolyte abnormalities. A possible exception is in foals with ruptured bladders, which are highly likely to be hypochloremic, hyponatremic and hyperkalemic. 

The fluid therapy plan should be divided into three stages initial resuscitation, rehydration and maintenance. The focus of resuscitation is the rapid reversal of hypovolemia. Rehydration aims to replace fluid losses. The maintenance phase aims to prevent the occurrence of further fluid deficits. In severely hypovolemic horses, a transition phase, in which fluid rates are higher than those calculated for the rehydration phase, may be necessary after initial resuscitation. The need for this should be assessed based on the clinical and laboratory responses to the initial resuscitation. Although plasma electrolyte imbalances may... 

There does not appear to be an antidote of choice for bismuth toxicity in humans. Gastric lavage can be used within 1 h of exposure. Replace fluids and electrolytes. Monitor renal and liver function for several days and treat failure conventionally. The newer chelating agents, meso-2,3-dimercaptosuccinic acid and D,L-2,3-dimercapto-propane-l-sufonic acid, are being investigated experimentally as antidotes for bismuth toxicity, and the latter has been shown to be effective. In mice, D-penicillamine has proven effective. 

Concentration determines the replacement fluid for a patient whose fluids and electrolytes are imbalanced. Replacement fluids are replaced orally (by mouth or nasogastric tube) or parenterally with IV fluids (intravenously or subcutaneously). 

Risk for fluid volume excess. Too much replacement fluid or fluid is infused too rapidly. 

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