Background
Hereditary angioedema is a rare genetic disorder most commonly caused by C1 esterase inhibitor deficiency, which leads to overactivity of the complement system and excess production of the vasoactive mediator bradykinin. It is characterized by recurrent episodes of angioedema affecting the skin, upper airway, and gastrointestinal tract. Triggers include but are not limited to trauma, surgery, intubation, dental work, infection, menses, and estrogen-containing oral contraceptives. The most feared complication is laryngeal edema leading to airway obstruction. Serum complement studies can be obtained to support the diagnosis of HAE. Patients may be on long-term prophylaxis with agents such as C1 inhibitor concentrate, androgens (e.g. danazol), and antifibrinolytics (e.g. tranexamic acid). Short-term prophylaxis prior to procedures may similarly be achieved with C1 inhibitor concentrate (or FFP if unavailable) and androgens. For acute attacks, the priorities are airway management and early administration of C1 inhibitor concentrate (or FFP if unavailable), ecallantide (kallikrein inhibitor), or icatibant (bradykinin B2 receptor antagonist).
Case Description
A 46-year-old female with HAE and right knee dislocation presented for elective arthroscopy and open medial collateral ligament repair. Her symptoms included episodic skin swelling, abdominal pain, & dyspnea secondary to airway edema requiring intubation at the age of 22. She was taking C1 esterase inhibitor by intravenous self-administration for prophylaxis every 48 hours and for acute attacks as needed. Her symptoms were currently well-controlled on this regimen.
On the day of surgery, the patient was given C1 inhibitor one hour prior to incision. She had a single shot femoral nerve block with 21 milliliters 0.5% ropivacaine, 50 mcg clonidine, and 150 mcg buprenorphine for post-operative analgesia. This was followed by a single shot spinal with 1.8 milliliters 0.75% bupivacaine in 8.25% dextrose and 15 mcg fentanyl. She was given intravenous midazolam and dexmedetomidine for sedation. Surgery proceeded uneventfully without airway compromise and the patient was brought to the recovery room in stable condition. On post-operative day number 1, the patient experienced swelling in the operative leg felt to be from angioedema and she was promptly given a dose of C1 inhibitor with resolution. She was discharged later that day and was doing well when seen in clinic one month post-operatively with no further exacerbations.
Discussion
Our patient with hereditary angioedema successfully underwent knee arthroscopy with peripheral nerve blockade and neuraxial anesthesia. We chose regional anesthesia to decrease the stress response associated with surgery and to avoid intubation, both known triggers for angioedema attacks. It also allowed our patient to communicate with us if she had the sensation of an acute attack coming on. We administered prophylactic C1 inhibitor as this has been shown to significantly decrease the risk of angioedema attacks and had additional doses of C1 inhibitor in case of an acute attack in the operating room. Lastly, the patient was admitted for observation as angioedema attacks can occur up to 48 hours following the procedure.
