Can patients with methemoglobinaemia safely be discharged based on clinical observations?

Date First Published:
March 23, 2022
Last Updated:
April 8, 2022
Report by:
Simon Ross Deveau, Advanced Clinical Practitioner (Torbay Hospital)
Search checked by:
Simon Ross Deveau, Torbay Hospital
Three-Part Question:
In [patients with methaemoglobinaemia] are [normal observations] sufficient to [allow safe same day discharge]?
Clinical Scenario:
A 37 year-old man attends the emergency department with cyanosis unresponsive to high flow oxygen. When blood is drawn it is a dark ‘chocolate’ colour and does not lighten when exposed to air. The patient reports he has recurrent methaemoglobinaemia of unknown origin and is currently under haematology who are attempting to illicit a cause. When is this man safe to be discharged?
Search Strategy:
CINAHL Plus & Medline – using the EBSCO interface, no date limit, apply equivalent subjects allowed
Search Details:
Terms = “meth*emoglobin*emia” AND “discharge”
Outcome:
Returned a maximum of 17 (CINAHL = 5, Medline = 17) results that were manually checked. Multiple animal studies and those where discharge criteria were not reported were rejected.

Search terms “meth*emoglobin*emia” AND “discharge (planning OR process OR management OR criteria)” – medline = 0, CINAHL = 1 (Croke, 2020) result.
Relevant Paper(s):
Study Title Patient Group Study type (level of evidence) Outcomes Key results Study Weaknesses
Methemoglobinemia in bronchoscopy: a case series and a review of the literature. Brown C; Bowling M 2013 America 11 people aged 17-77 years-old Literature review to form case series Narrative synthesis. These 11 case studies did not include the other 3 case studies in this table Peripheral oxygen saturations returning to normal may permit same-day discharge Differing treatments – not all study participants received methylene blue (MB), even those who received MB did not receive the same dosage. Many patients remained in hospital due to co-morbidities
Topical Benzocaine and Methemoglobinemia. Hieger, MA; Afeld, JL; Cumpston, KL; Wills, BK 2017 America Single 47 year-old female Case study None – narrative Observations within normal limits and MetHb level 5.4% before discharge Case study/single participant
Suspected methemeglobinemia following awake intubation: one possible effect of benzocaine topical anesthesia -- a case report Rinehart RS; Norman D 2003 America Single 28 year-old male Case study None – narrative Observations returned to normal allowing same day discharge Case study/single participant
Thinner intoxication manifesting as methemoglobinemia. Verma S; Gomber S 2009 India Single 3 year-old male Case study None – narrative Patients who return to normal may be discharged Case study/single participant
Author Commentary:
No experimental studies have been reported that investigated safe discharge criteria for patients with methaemoglobinaemia.
In total there is limited data to support any decision to admit or discharge, however reported clinical practice supports discharge when clinical observations return to normal range.
Bottom Line:
It would appear safe to discharge patients with normal observations and methaemoglobinaemia from the Emergency Department, or other area, assuming no co-existent conditions that warrant admission.
References:
  1. Brown C; Bowling M . Methemoglobinemia in bronchoscopy: a case series and a review of the literature.
  2. Hieger, MA; Afeld, JL; Cumpston, KL; Wills, BK. Topical Benzocaine and Methemoglobinemia.
  3. Rinehart RS; Norman D . Suspected methemeglobinemia following awake intubation: one possible effect of benzocaine topical anesthesia -- a case report
  4. Verma S; Gomber S. Thinner intoxication manifesting as methemoglobinemia.