Infants Part I (1 Hour)
Body Mass To Surface Area Ration
Body mass is often represented mathematically as the Body Mass Index. To calculate Body Mass Index, simply divide your weight (in kg) by your height (in meters). Body surface area is another way of saying surface area of the skin. There are various mathematical formulas to determine body surface areas, which make determining body surface area something a clinician might use to calculate instead of trying to measure the amount of skin on the patient's body. In nature, smaller mammals tend to have larger body surface area to body mass ratios and larger animals tend to have smaller body surface areas to body mass ratios. This body mass to surface area ratio is what causes:
- Elephants to have a hard time cooling themselves off (smaller body mass to surface area ratio).
- Small animals having super high metabolic rates so they can generate warmth.
- The infant freezing to death in 60-degree weather, takes several bowel movements every day, and eats 5 or 6 times a day.
Now that you understand the concept and can appreciate the difference between body mass and body surface area, let’s explore the relevance of the statement, ‘children have higher body surface area to mass ratios’. The reason this is important is because of difference in adult and pediatric body surface area to mass ratios. Pediatric metabolic rate is much higher. The amount of hormones in your blood, the amount of blood pumped by your heart, amount of water evaporation, and nearly every other metabolic process is dictated by the body surface area (not body mass). Additionally, children are more susceptible to toxic exposures through the skin because they will proportionately take in more toxins than their body mass can absorb. What all this means for you is children are more easily and deeply burned than adults. Additionally they lose more fluid and heat than adults. This is why you have to keep them warm and why they have so many problems when they get dehydrated or lose any amount of fluid.
