Dear Readers
It’s been a while. Actually it’s been about 7 years since I last wrote on this blog. I have been busy with many things!!! But the urge to write has brought me back here.
Today I want to briefly discuss about “flapping tremor”, otherwise known as asterixis.
Asterixis is a rapid and brief flexion and corrective extension of the fingers when the aforementioned digits are extended and with the wrist, forearm and shoulder being held in extension. Basically it looks like someone maintaining a press-up position with their arms outstretched and the hands “flat to the floor” when instructed to do so in a supine, semi-recumbent or sitting posture. The rapid flexion and corrective extension is brief and irregular in occurrence. But it’s presence signifies possible encephalopathy and hence, when noticed by the clinician, it can lead to an important diagnosis and intervention.
Traditionally there are three main causes including:
- Hepatic failure (fulminant or decompensated chronic types)
- Uremia
- CO2 retention.
However, common problems such electrolyte abnormalities and drugs are also sometimes implicated.
Asterixis can sometimes be accompanied by irregular movements of the legs referred to as jactitations. This is when a supine patient’s legs rotate laterally and then medially in an irregular fashion. Again, this is a representation of encephalopathy.
The key to diagnosing it is observation.
Starting your physical examination by looking at the hands (instead of the eyes and conjuctivae) is the entry step towards being able to see the sign (and other important hand signs!) Even without outstretched hands the “flapping” can occasionally be seen. If suspicious of the sign then ask the patient to stretch out their hands and keep looking for perhaps up to 30 seconds or even a minute. Use your common sense. If the patient has weakness or joint pains then please do not subject your patient to this test. It will either produce a false negative result or cause unnecessary pain, respectively.
Recently, I was consulted on a very elderly lady with mild chronic kidney disease who had experienced an osteoporotic vertebral fracture. She had been commenced on tramadol at a regular, but high-end dose four times daily.
The nursing staff had been worried because the patient developed new onset nocturnal hypoxemia without a known cause. Her cardiopulmonary physical examination was apparently unchanged from admission and tests including a chest radiograph, and a work up for pulmonary embolism were negative.
When asked to see her, I immediately saw the flicker of asterixis. On proceeding to ask the patient to stretch out her hands, she began to show the “flapping” sign. Bingo! Jactitations were also evident even when the patient was sitting.
Her liver function tests were normal, her chronic kidney disease was not advanced and she had no evidence of chronic obstructive pulmonary disease. An arterial blood gas had not been performed at that time though.
However, the drug history including tramadol and a third generation cephalosporin (for treating a urinary tract infection) are little known causes of asterixis. Tramadol, an opioid medication, can cause the “morphine twitch.” In this patient, she had normal pupils and her respiratory rate and SpO2 when awake were all normal. Her GCS was 15/15. She had no signs to signify ongoing infection and her vital signs were otherwise stable.
Hence, reversal by naloxone was not deemed necessary. Simply discontinuing the tramadol (particularly because the back pain was resolving during the hospital admission) was all that was considered necessary.
With increased age, both hepatic metabolism and/or renal excretion of drugs can become impaired. Therefore, the levels of certain drugs can increase leading to side effects.
Even if the common three causes of liver disease, uremia and CO2 retention are not present, keep on thinking about the cause of asterixis and consider excluding implicated drugs (anticonvulsants are also causes but a dose reduction rather than stopping the drug permanently may be better to avoid withdrawal seizures; please consult a neurologist!) and correct electrolyte abnormalities accordingly.
In this case, the tramadol, an opioid, was most likely the cause of asterixis and jactitations. The hypoxemia may relate to a reduced respiratory rate (a side effect of opioids) at night leading to hypoxemia. As a result, she might have nocturnal CO2 retention thereby compounding the presence of drug-induced asterixis.
Sometimes patients can also have Cheyne Stoke respiration or obstructive sleep apnea at night which can also lead to hypoxemia.
An important intervention would be to observe the patient sleeping at night by looking for an abnormal respiratory pattern, hypoxia, episodes of apnea, snoring and awakening in an abrupt and startling manner. Obtaining an arterial blood gas during an episode of hypoxemia and performing a sleep study would be other important meaures.
Remember that common things are common.
I hope that this helps.
Time for me to flap away........
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