Which of the following is FALSE regarding hypertonic saline?
Hypertonic saline (7.5%) has been used as a treatment modality in patients with closed head injuries. It has been shown to increase cerebral perfusion and decrease intracranial pressure, thus decreasing brain edema. However, there also have been concerns of increased bleeding because hypertonic saline is an arteriolar vasodilator.
Normal saline is:
Sodium chloride is mildly hypertonic, containing 154 mEq of sodium that is balanced by 154 mEq of chloride. The high chloride concentration imposes a significant chloride load upon the kidneys and may lead to a hyperchloremic metabolic acidosis. It is an ideal solution, however, for correcting volume deficits associated with hyponatremia, hypochloremia, and metabolic alkalosis.
Fluid resuscitation using albumin:
Albumin is available as 5% (osmolality of 300 mOsm/L) or 25% (osmolality of 1500 mOsm/L). Due to increased intravascular oncotic pressure, fluid is drawn into the intravascular space, leading to pulmonary edema when albumin is used for resuscitation for hypovolemic shock. Hydroxyethyl starch solutions are associated with postoperative bleeding in cardiac and neurosurgery patients.
Water constitutes what percentage of total body weight?
Water constitutes approximately 50 to 60% of total body weight. The relationship between total body weight and total body water (TBW) is relatively constant for an individual and is primarily a reflection of body fat. Lean tissues, such as muscle and solid organs, have higher water content than fat and bone. As a result, young, lean men have a higher proportion of body weight as water than elderly or obese individuals. An average young adult male will have 60% of his total body weight as TBW, while an average young adult female's will be 50%. The lower percentage ofTBW in women correlates with a higher percentage of adipose tissue and lower percentage of muscle mass in most. Estimates of TBW should be adjusted down approximately 10 to 20% in obese individuals and up by 10% in malnourished individuals. The highest percentage of TBW is found in newborns, with approximately 80% of their total body weight composed of water. This decreases to about 65% by 1 year and thereafter remains fairly constant.
If a patient's serum glucose increases by 180 mg/dL, what is the increase in serum osmolality, assuming all other laboratory values remain constant?
Osmotic pressure is measured in units of osmoles (osm) or milliosmoles (mOsm) that refer to the actual number of osmotically active particles. For example, 1 millimole (mmol) of sodium chloride contributes to 2 mOsm (one from sodium and one from chloride).
The principal determinants of osmolality are the concentrations of sodium, glucose, and urea (blood urea nitrogen [BUN] ):
Calculated serum osmolality= 2 x sodium + glucose / 18 + BUN / 2.8
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