Porphyria Flashcards
What are porphyrias?
Porphyrias are inherited errors of metabolism in which porphyrins (proteins essential for oxygen transport among other functions) are overproduced.
What is considered to be the most vital porphyrin
produced in the body?
Heme is considered to be the most vital porphyrin. It combines with proteins to form hemoglobin and the cytochrome P-450 isoenzymes.
What is the pathophysiologic characteristic that
distinguishes one form of porphyria from another?
There are eight major steps in the formation of heme. Each step requires a specific enzyme to produce the next chemical in the chain reaction. Each form of porphyria is defined by a deficiency in the enzyme that accomplishes a specific step.
Depending upon the enzyme that is lacking, there is an accumulation in the chemical components that lead up to it, similar to cars being backed up on a blocked freeway. The specific chemical components that accumulate cause different disease characteristics to appear.
What is the most common type of porphyria? What
is the most common type of ACUTE porphyria?
Porphyria cutanea tarda is the most common form of porphyria. It usually appears as photosensitivity in males over the age of 35 and is not stimulated by the administration of any drugs, nor does it exhibit any forms of neurotoxicity. Acute intermittent porphyria is the most common acute form of porphyria. It produces the most serious symptoms such as hypertension, renal dysfunction, and CNS symptoms and can be precipitated by the administration of certain drugs.
What are common symptoms of an acute porphyric
attack?
Severe abdominal pain, nausea, diarrhea, dark urine, seizures, cranial nerve deficits, peripheral neuropathy, hypertension, skeletal muscle weakness, and electrolyte disorders.
Can patients with acute intermittent porphyria
undergo regional anesthesia?
Yes, there is no evidence that any regional technique or local anesthetic has precipitated an acute porphyric attack.
How should an acute porphyric attack be treated?
Avoiding any other precipitating factors is key, keeping the patient warm (cold may precipitate an attack), and administering intravenous glucose can shorten the length of an attack. If an attack occurs in the operating room, benzodiazepines should be
administered to help alleviate symptoms. Propofol is another anesthetic agent that can be administered until other measures can be taken to relieve the patient’s condition.
How does NPO time relate to patients with acute
intermittent porphyria?
Fasting has been identified as a precipitating factor for AIP. As such, prolonged NPO times should be avoided and the administration of a glucose-saline solution during the NPO time should be considered.
What anesthesia-related drugs should definitely be
avoided in patients with porphyria?
An easy mnemonic to remember which anesthesia-related drugs should be avoided in patients with acute intermittent porphyria is “a patient with porphyria should avoid being a KEPT MAN” for Ketorolac, Etomidate, Pentazocine, Thiopental,
Methohexital And Nifidepine”.
