Wednesday, August 13, 2014

My low osmolarity ORS notes for MBBS exam and constituents of ORS mnemonic

{Learning is one thing and deciding what will you write in a written test is another. This is what I have decided to write in my MBBS exam if a short answer question SAQ or a long answer question LAQ on low osmolarity ORS is asked! I might actually do a notes label if time permits for most of important questions. But for now, here goes the first one.

Let's get started!}

Defintion: Oral rehydration therapy is an inexpensive glucose and electrolyte solution as promoted by the World Health Organization that has reduced the number of deaths from dehydration due to diarrhea substantially.

Pathophysiology: Oral rehydration takes advantage of glucose-coupled sodium transport, a process for sodium absorption which remains relatively intact in infective diarrheas due to viruses or to enteropathogenic bacteria, whether invasive or enterotoxigenic. Glucose enhances sodium, and secondarily, water transport across the mucosa of the upper intestine.

Mechanism: The amount of fluid absorbed depends on three factors: the concentration of sodium, the concentration of glucose and the osmolarity of the luminal fluid.
Increasing the sodium concentration may result in hypernatremia and increasing the glucose concentration increases the osmolarity of the solution that may result in a net loss of water.
CHO to Na ratio should not exceed 2:1 in these solutions.

Effectiveness: Studies show that the need for unscheduled supplemental IV therapy in children given this solution was reduced by 33%, the stool output was reduced by about 20% and the incidence of vomiting by about 30%. The effect of this reduction could result in fewer children requiring hospitalization, fewer secondary infections, a diminished need to handle blood with its potentially dangerous consequences, and lower health care costs.

Reduced osmolarity ORS grams/litre
Glucose, anhydrous 13.5    
Sodium chloride 2.6
Potassium chloride 1.5  
Trisodium citrate 2.9          

Reduced osmolarity ORS mmol/litre
Glucose, anhydrous 75
Sodium 75
Potassium 20
Citrate 10
Chloride 65
Total Osmolarity 245

{Mini-memory aid:
Remember 75. It has to be equal for glucose and sodium.
Subtract 10 and you have osmolarity for chloride, that is, 65.
Remember 20 for potassium.
Subtract 10 and you have osmolarity for base citrate, that is, 10.

Remember 2.6 for sodium chloride.
Flip the 6 upside down and it becomes 9 for osmolarity of trisodium citrate, that is, 2.9.
Minus 1 from each decimal of 2.6 and it becomes 1.5 for osmolarity of potassium chloride.}

Contraindications to the use of ORT:
Intestinal ileus
Stupor or coma
Protracted vomiting despite small, frequent feedings
Worsening diarrhea and an inability to keep up with losses

{That's all!


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