Abstract
BACKGROUND: Hypotension is commonly observed after induction of anesthesia. Risk factors for intraoperative hypotension include higher ASA class, older age, propofol use, combined general/regional anesthesia, emergency surgery, and use of antihypertensives. Patients who are treated with tricyclic antidepressants (TCAs) may develop severe hypotension in connection with surgery and anesthesia, not responding to vasopressors such as phenylephrine and ephedrine, and use of adrenaline or noradrenaline are necessary to restore the blood pressure. Anaphylaxis may be suspected due to the rapid onset and resistance to usual treatments leading to referral for allergy investigation. The aim of this paper was to identify and describe the clinical characteristics of patients referred to the Danish Anesthesia Allergy Center (DAAC) with perioperative hypotension, without elevation in tryptase, and with negative allergy investigations, who were on regular treatment with TCAs. The pharmacological mechanism behind this phenomenon will also be explored. METHODS: Patients were identified from the DAAC database. Patients with hypotension (systolic blood pressure <75 mmHg) as the only symptom and negative allergy investigations and patients on antidepressants were included. The study period was 2011-2019. RESULTS: Ten patients were identified. Hypotension occurred after anesthesia induction, the median time from induction to the onset of hypotension was 7.5 min. Eight needed adrenaline or noradrenaline to restore blood pressure. No allergen was identified on detailed investigation and serum tryptase was not significantly elevated. CONCLUSION: Monosymptomatic perioperative hypotension without a significant increase in serum tryptase can be caused by TCAs and this is an important differential diagnosis to anaphylaxis. In patients on regular treatment with TCA perioperative hypotension responds well to noradrenaline or adrenaline but less well to vasopressors such as phenylephrine and ephedrine used perioperatively.