|
In
Chapter Seven, you learned about the importance of
osmolality as an indicator of dehydration. A valuable
part of the medical record you keep for your loved one
will be your assessment of his or her hydration status.
Using the lab values that you will find in the medical
record kept by the nursing home (or by your loved one’s
physician if your loved one is living independently),
you can monitor this status. An important tool is the
calculation of osmolality. Keep a copy of this appendix
in your three-ring binder and update the osmolality
chart frequently.
Calculating Osmolality:
|
|
normal |
date |
date |
date |
Sodium
|
135 – 148 |
|
|
|
|
Potassium |
3.5 – 5.5 |
|
|
|
|
BUN |
5 – 26 |
|
|
|
|
Glucose |
65 – 109 |
|
|
|
|
|
|
|
|
|
Osmolality
|
285 – 295 |
|
|
|
An Internet
calculator is found at the following site:
You can also calculate
this on paper using the following formula:
Serum Osmolality = (2 x (Na+K)) +
(BUN/2.8) + (glucose/18)
Because kidney function is adversely affected by
dehydration, keeping track of kidney function is
important as an early warning that serious problems
exist. An important indicator of kidney function is the
ratio of BUN to serum creatinine. You can use the lab
values in the chart below to make this calculation. Note
that a ratio of 20:1 or higher indicates serious kidney
malfunction.
Tracking BUN:Serum creatinine
ratio:
|
|
Normal |
date |
date |
date |
|
A. BUN |
5 –
26 |
|
|
|
|
B.
Serum creatinine |
65 –
109 |
|
|
|
|
|
|
|
|
|
|
Ratio = (A÷B)/1 |
<
20:1 |
|
|
|
(BUN:Serum
creatinine ratio equals BUN ÷
Serum creatinine:1)
Example: 40:2 equals 40 ÷ 2
to 1 (20 to 1 or 20:1)
Another valuable indicator of kidney function measures
how well the kidneys filter and eliminate toxins. This
is done by measuring the level of serum creatinine left
in the bloodstream after filtration. Use the chart below
to record lab values and to record the calculation of
estimated glomerular filtration.
Calculating Kidney Function – Estimated
Glomerular Filtration rate (GFR):
|
|
Normal |
date |
date |
date |
|
A. BUN |
5 – 26 |
|
|
|
|
B.
Serum creatinine |
65 – 109 |
|
|
|
|
|
|
|
|
|
|
Est. Creatinine Clearance |
85 – 125 ♀
95 –
135 ♂ |
|
|
|
You can also use the following formula to calculate
estimated creatinine clearance:
For men:
[[140 - age(yr)]*weight(kg)]/[72*serum Cr(mg/dL)]
For women: [[140 - age(yr)]*weight(kg)]/[72*serum
Cr(mg/dL)] X .85
Monitoring Body Mass Index (BMI)
Use
the website below to monitor BMI. For this, you will
need to keep track of your loved one’s weight and
height. Again, clinicians recommend that the elderly be
weighed once a week at the same time of day, wearing the
same or similar clothing.
Body Mass Index:
|
|
Date |
Date |
Date |
Weight
|
|
|
|
|
Height |
|
|
|
|
|
|
|
|
|
Body Mass
Index (BMI): |
|
|
|
|
