Hyponatremia, By Dr.Michelle Lee.
The nurse pages.
The patient's sodium is 127.
It wasn't that low yesterday.
Can you come to look at him?
In your mind, you consider the causes of hyponatremia.
Acute causes could include an errant result, IV fluid or parenteral nutrition or medications,
volume depletion, third spacing, or SIADH.
You also consider chronic causes, like renal wasting and water intoxication.
Questions to ask on the phone or to look up: What phase of transplant is the patient in?
Is the patient undergoing conditioning, receiving high-dose chemotherapy or immunosuppression?
Has the patient received the stem cell infusion today?
Are the patient's counts in the process of falling or is the patient awaiting engraftment?
Has the patient already experienced the acute toxicities of transplant and is recovering,
approaching discharge?
Or is this a patient who's been readmitted for infection, graft versus host disease,
or dehydration?
Knowing what phase of transplant the patient is in can help you understand why the patient
should have hyponatremia.
Other questions to consider for the patient: Has the patient been urinating normally?
Does the patient have excessive output, like vomiting or diarrhea, excessive input, like
receiving hyperhydration?
Trends to evaluate for the patient include heart rate, blood pressure, respiratory rate,
oxygen saturation.
It's worth looking to see how the patient's sodium and, if checked, osms have been trending.
And it's important to know how the patient's weights and specific gravities have changed
over recent days.
This allows an appropriate assessment of fluid status.
And finally, evaluating the patient's urine output will help in the same regard.
As you go to the room to see the patient, you want to observe, is the patient awake
or asleep?
Has the patient had a recent history of vomiting, diarrhea?
Is the patient able to urinate?
Is the patient having any pain?
On examination, you'll want to assess whether the patient responds appropriately to questions.
Does the patient have hepatomegaly?
Any focal abdominal pain?
Does the patient have any edema?
You'll want to check the IV infusions into the patient.
You can ask the nurse: can you show me what the patient is getting now?
Studies to order include rapidly repeating the chem 10.
Obtain a VBG and lactate if there are any signs of vital sign instability.
Point of clarification.
You can also consider sending whole blood electrolytes with your VBG.
Repeat the CBC and liver function tests.
It's reasonable to check serum sodium and serum osms as well as urine sodium and osms,
and in the same vein, a serum sodium and creatinine with a urine sodium and creatinine.
A urine analysis will allow for assessment of the specific gravity and whether there
are any blood or red blood cells in the urine.
And a weight may be appropriate if there are concerns for recent changes.
Interventions to initiate include evaluating those repeat laboratory studies that should
return quickly to determine whether the sodium change is real, and that may have actually
worsened since the time of the initial check.
If the process is acute, then you must act to understand the etiology to prevent progression
and to slowly correct the course.
If there's concern for the IV fluid or parenteral nutrition bag or medication side effect, then
please stop it, and call the pharmacy.
If the patient appears to have volume depletion, like a recent history of vomiting or diarrhea
or an exam with tachycardia, hypotension, or delayed capillary refill, give a normal
saline bolus of 20 cc per kilogram over 20 minutes, and monitor for improvement in vital
signs.
If there's evidence of third spacing, then consider how much excess fluid the patient
is carrying and where it is.
If the respiratory rate is increased and the oxygen saturation is decreased, it's appropriate
to worry about pulmonary edema or pleural effusions.
Obtain a chest X-ray and VBG to assess the patient's respiratory status further.
If the heart rate is increased, or heart sounds are distant, or pulses weak, it's appropriate
to worry about a pericardial effusion.
Obtain a chest X-ray and VBG and lactic acid to reassess the cardiac status.
Other causes of third spacing in transplant include sepsis or veno-occlusive disease of
the liver.
Consider further evaluation if evidence points towards those indications.
If the patient has evidence of SIADH, Syndrome of Inappropriate ADH Secretion, and a reason
for that to happen, make the patient NPO.
Call the on-call attending for help with prioritizing the intravenous intake and inform the ICU
with a plan to have 3% sodium chloride available.
Point of Clarification.
It is important to evaluate for possible causes of SIADH, which may include medications, problems
with the brain or nervous system including encephalitis or meningitis, problems with
the lung including pneumonia or respiratory failure, and cancer such as lymphoma or brain
tumor.
If a post-renal process, like hemorrhagic cystitis with obstruction is possible, then
a renal ultrasound may be indicated.
If the process appears chronic and the patient's vital signs and exam are normal, then calculation
of the fractional excretion of sodium can help with determining the cause of hyponatremia.
The urinalysis can be evaluated for blood or red blood cells.
If a renal process is suggested, then the IV fluids can be changed from half normal
saline to normal saline.
A review of hyponatremia in the bone marrow transplant patient includes evaluating for
acute and chronic issues.
The acute issues include an errant result, IV fluid or parenteral nutrition or medications,
volume depletion, third spacing, or SIADH.
Chronic causes include renal wasting and water intoxication.
Evaluation of hyponatremia in the bone marrow transplant patient should be performed rapidly
and lead to an intervention and appropriate follow-up.
After developing a hypothesis for why hyponatremia has occurred and making an intervention, it's
appropriate to establish a monitoring plan for following up the sodium and a chemistry
at some interval of time, like every six hours.