Hyponatremia: Quick & Dirty

Clinical Manifestations

Serum [Na] > 125 mmol/L

Usually asymptomatic

Serum [Na] 125-130 mmol/L

Predominantly GI symptoms (nausea, vomiting)

Serum [Na] <>

Lethargy, headache, ataxia, psychosis,weakness

Severe cerebral edema - seizures, coma, brain stem herniation, respiratory depression, death

Physiological Manifestations

↓ Serum [Na]

(in the presence of ↓ tonicity)

Shift of water from ECF → ICF

Water enters brain cells

Cerebral edema

Really good article

Adroque HJ, Madias NE. Hyponatremia. NEJM 2000, 342(21): 1581-9.

1. Figure out their volume status
1. Hypovolemic (thirsty, + orthostatics, dry mucus membranes, BUN/Cr)- diuretics, hypoaldosterone, salt-wasting nephropathy

Treat with fluids, hormones, salt

2. Hypervolemic (edema in legs, pulmonary edema)- CHF, Liver disease, nephrotic syndrome

Treat by diuresing, water restriction

3. Euvolemic (none of the above problems)- SIADH

inappropriately secretes ADH, so body doesn’t want to lose water, have very concentrated urine (urine osm- high, urine Na- high), so water stays in the body (serum osm- low)

need to make sure nothing is wrong with thyroid and adrenals (check TSH, cortisol)

treat by free water restriction and sometimes need to replace sodium, if chronic- demeclocycline

psychogenic polydipsia- need to drink 12-20 L a day and urine osm will be low

2. How to Treat
1. Too rapid- central pontine myelinosis
2. Rate of increase should not exceed 0.5 mEq/L/hr
3. In the case of neurologic emergency

Awesome Website

http://www.medcalc.com/sodium.html

Adrogue Formula:
Change in serum Na+ =	(infusate Na+ + infusate K+) - serum Na+
	_____________________________
	total body water + 1

Use the above formula to estimate the effect of 1 liter of any infusate containing sodium and potassium on serum sodium

Infusate Infusate Na+ (mmol/L) 5% NaCl 855 3% NaCl 513 0.9% NaCl (NS) 154 Lactate Ringer's 130 0.45% NaCl (½ NS) 77 0.2% NaCl (¼ NS) 34 5% Dextrose in water (D5W) 0

Total Body Water (in liters) : Children 0.6 x weight Women 0.5 x weight Men 0.6 x weight Elderly Women 0.45 x weight Elderly Men 0.5 x weight

Example

45 yr old 70 kg man, Na 110

Using 3% NS

Change in serum Na= (infusate Na + infusate K) – serum Na/ total body water + 1

= 513- 110/ 0.6 (70) + 1

= 403/ 43

= 9.7

So, 1 liter of 3% NS will bring up this patient’s serum Na by 9.7

Let’s use 0.9% NaCl

= 154 – 110/ 43

= 44/43

= 1

So, 1 liter of 0.9% NS will bring this patient’s serum sodium up by 1

Gen Med Floor Tips

1. Work as a Team- help each other out, start discharge summaries early, help the post-call person, get labs for people, etc…

2. Get organized- keep all of your patient’s info on a card so you’ll know everything on a day-to-day basis

3. Do not leave without signing out to the senior and on-call person

4. Come early and find out everything about what happened to your patient by talking to the on-call person and nurses, check the orders for that night

5. When doing an H&P in the PMHx section, please quantify everything. If patient has COPD, write their last PFTs, if patient has DM, write their last hemoglobin A1C, if patient is coming in for a pneumonia, write down their last few chest xray results (and get the xrays, of course). Write their echos in the the PMHx section. In the HPI section, towards the bottom, write down the vitals of the patient in the ED and write down what they did in the ED to treat the patient.

6. If you need help, are confused or overwhelmed, have a question, don’t hesitate to ask me anything. If you are on-call and unsure how to handle anything, call your senior. Nobody will think that you couldn’t handle it. Everyone will think you are wise to ask for help.

7. If you don’t know something during rounds, just say it. It is okay. But, get the information ASAP.

8. You will be the primary doctor for this patient. You need to write labs that are needed every morning. You will need to make sure social issues are met. Make sure things we ordered in the AM actually happened.

9. When cross-covering on the weekends, find out everything you need to know about the patient. Please don’t say, “This isn’t my patient, so I didn’t know.” Find out.

10. If you order a test, follow it up. Take the time to look at the echo with the cardiologists or watch the EGD.

11. Fill out orange med sheets when the patient is admitted.

12. Read, read, read about your patients. Keep a Washington’s Manual on you. Get a Pocket Medicine by the Mass Gen Hospital. (You have a book fund.)