Setting: ED
CC: “My legs are weak.”
VS: BP: 110/70 mm Hg; P: 110 beats/minute; T: 97.8°F; R: 12 breaths/minute
HPI: A 43-year-old man comes to the ED with bilateral leg weakness, which he has been experiencing for the past 2 days. For the first day it was minor and did not interfere with function. On the day of admission, he has become unable to walk. He is brought by ambulance.
PMHX: none
Medications: none
PE:
General: awake and alert
Neurological examination: bilateral leg weakness, equally on both sides; absence of ankle jerk and knee jerk reflexes
Chest: clear
Cardiovascular: normal
HEENT: normal pupil reflexes; no ptosis
Initial Orders:
Forced vital capacity (FVC)
Peak inspiratory capacity
Oximeter
Which of the following will lead to the patient’s death?
a. Sepsis
b. Respiratory failure
c. Seizure
d. Encephalitis
Answer b. Respiratory failure
When weakness ascends up to the diaphragm, it will potentially impair breathing. Guillain-Barré syndrome (GBS) is ascending weakness with the loss of reflexes. MG is weakness that is slowly progressive and distinctly worsens with repetitive use.
There is a slight decrease in FVC and a peak inspiratory pressure of −24 cm H2O. There is no fever. Because there is impairment of respiratory functioning, the person should be placed in the ICU. You do not want the patient to develop respiratory failure unobserved on a regular hospital ward.
Which of the following will stay intact in this patient?
a. Elastic recoil
b. Ability to cough
c. Total lung capacity
d. Inspiratory reserve volume
Answer a. Elastic recoil
Elastic recoil is not based on muscular exertion. GBS only impairs muscular exertion. It has no effect on tissue characteristic, such as elastic fibers or the flexibility of the chest wall. Total lung capacity is decreased because it is based partly on the inspiratory reserve volume, which will be markedly reduced in this patient.
What is the most accurate diagnostic test?
a. Nerve biopsy
b. Nerve conduction velocity (NCV) testing
c. Serum anti-nerve immunoglobulin G (IgG)
d. LP
e. Lumbosacral spine CT/MRI
Answer b. Nerve conduction velocity (NCV) testing
A needle is placed at one end of the nerve and an electrical impulse is administered. A positive test shows decreased F-wave transmission. There is no such test as a “serum anti-nerve IgG.” Although LP is often done, it is more useful for excluding other diseases than it is to specifically show something pathognomonic for GBS.
Orders:
Start IVIG.
Do LP.
Test NCV.
Move the patient to ICU.
Which of the following is most likely found on LP in GBS?
a. Moderate elevation of lymphocytes
b. High protein with normal cell count
c. Low glucose and neutrophils
d. High protein and high lymphocyte count
Answer b. High protein with normal cell count
The LP is done to exclude CNS infection. You should find a normal CSF cell count in GBS. There is no specific finding on LP that confirms GBS.
IVIG should be ordered stat without waiting for a laboratory confirmation of the diagnosis. GBS can result in permanent neurological disability and there is no reason to delay therapy although it does not work overnight.
CSF shows normal cell count and elevated protein. NCV testing takes more time to perform and receive results.
Ask anyone with GBS about the following:
• Recent vaccinations
• Diarrheal episodes or gastrointestinal (GI) tract infections
Campylobacter infection is the most common identifiable event causing GBS.
IVIG = Plasma Exchange (Plasmapheresis) for Efficacy
What is the mechanism underlying GBS?
a. Interleukin elevation
b. Antibodies attacking CNS white matter
c. Antibodies attacking peripheral nerve myelin
d. Infarction of vasonervorum
Answer c. Antibodies attacking peripheral nerve myelin
In GBS, antibodies attack the myelin, stripping it off and damaging conduction. Without myelin, NCV is slow. Campylobacter provokes the production of these antibodies for an unknown reason. The vasonervorum is damaged in diabetes peripheral neuropathy and vasculitis. Multiple sclerosis damages CNS white matter.
“Molecular mimicry” means something in myelin seems to “mimic” the cell surface of campylobacter.
In the ICU, the patient is reported as “looking fine” and the postgraduate year 3 (PGY3) resident wants to transfer the patient out immediately. He says “the saturation is normal.”
How would you best follow the patient’s respiratory condition?
a. Serial arterial blood gas (ABG) measurements
b. Peak inspiratory flow
c. Pulse oximetry
d. Forced expiratory volume at 1 second (FEV1)
Answer b. Peak inspiratory flow
You want to know if the respiratory muscles are weakening before the patient’s oxygen saturation level drops. You cannot wait for the partial pressure of carbon dioxide (PCO2) to rise before determining that the patient needs intubation. It will be too late. The same is true of oxygen saturation. The PCO2 and oxygen saturation do not change until there is outright respiratory failure. Peak inspiratory pressure predicts who is about to have respiratory failure before it occurs.
Do not wait for desaturation or respiratory acidosis!
Use peak inspiratory pressure to follow GBS!
Thirty percent of patients with GBS need intubation.
GBS is a demyelinating disease decreasing muscle strength (Figure 4-3).
The diaphragm is a muscle.
Figure 4-3. Antibodies attack and remove myelin from peripheral nerves. (Reproduced with permission from Longo DL, et al. Harrison’s Principles of Internal Medicine, 18th ed., Vol. 2. New York: McGraw-Hill; 2012.)
Peak inspiratory pressure starts to improve as does the FEV1 on bedside spirometry. You transfer the patient out of the ICU. Consult medical rehabilitation, physical therapy, and the hospital social worker. The Step 3 examination is also very big on asking “what will you tell the patient?” in terms of prognosis. Twenty percent of patients will not recover muscle strength and it will take months for full recovery in the patients who do recover.
Ineffective Therapy in GBS
• Glucocorticoids
• Combining IVIG and plasmapheresis
• Cyclosporine
• IVIG blocks macrophages.
• Blocked macrophages cannot attack myelin.