If it is general anesthesia then the individual has to be in a state of fasting for a certain period of time but the immediate requirements of hydration are met through intravenous infusions. The requirement for water and minerals ranges from saline fluids to Hartmann's solutions depending upon the severity of the physical condition and duration of the illness and period of remaining in a state of nothing per orum (NPO).
Apart from the physical condition and the severity of the disease, climate also plays an important role in determining and maintaining the body requirements for hydration. A hot and dry climate demands some additional volumes of fluids to be infused other than what has been calculated. Comparatively, in a cold and humid atmosphere, the fluids requirement may need just the replacement of 24 hours needs based on excretion and perspiration if any exist.
Gender may not be an important determining factor but the extreme of age and size of the body influence the daily needs of the individuals who are o fluids. Calculations for fluid requirements in paediatrics category is strictly based on body weight as compared to rough estimation in adults. Also, elderly patients need to be replaced with fluids with care. Similarly, monitoring fluid intake and output may need some judicious efforts as compared to healthy and adult individuals. In the same context, individuals with some chronic disease, like, diabetes mellitus or congestive heart disease require special care in the replacement of fluids. In the following paragraphs, discussion is made to address the issue of fluid replacement in patients with elective surgical procedures, usually without any complications; followed by fluid requirements and discussion in burn patients. The last topic is on fluid replacement in trauma patients followed by a summary.
Elective surgical procedures
Elective surgical procedures which involve handling of gut may be required not to take something orally so that gut returns to its normal working state after it has gone through some trauma or put to a stage of disturbance. Usually, it takes about six to eight hours postoperatively to start taking some fluids and then light diet orally. During the state of NPO, an adult individual is needed to be infused with some appropriate fluids to replace routine losses. Major sources of fluid losses are urine, insensible loss and faeces. This routine loss of fluid also takes away some important electrolytes from the body; about 80 mmol of sodium and 70 mmol of potassium is excreted (Principles of fluid, 2008) In addition to this routine loss in normal state of health, some changes take place in human body to cope with the situation. These can be termed as 'stress response', 'third space losses' and losses from the gastrointestinal tract (Principles of fluid, 2008). So body requirements may be the losses in addition to through urine or stoll. In such situation, replacement is carried out by crystalloids, the solutions with a similar composition as that of extracellular fluids. These fluids are given till a patient is kept in a state of fasting (Pandey, 2003; Roberts, 2001; Udeani, 2006). The best replacement of fluids can be accomplished by weighing the patient and monitoring any change in weight. This may not be a feasible practice so replacing the losses with addition of insensible loss may be sufficient to maintain a continuous supply of