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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

Terms = “meth*emoglobin*emia” AND “discharge”

Search 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)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
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
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
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
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

Comment(s)

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.

Clinical 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. Journal of bronchology & interventional 20(3); 241-6
2. Hieger, MA; Afeld, JL; Cumpston, KL; Wills, BK Topical Benzocaine and Methemoglobinemia. American Journal of Therapeutics 24(5); e596-e598
3. Rinehart RS; Norman D Suspected methemeglobinemia following awake intubation: one possible effect of benzocaine topical anesthesia -- a case report AANA Journal 71(2); 117-118
4. Verma S; Gomber S Thinner intoxication manifesting as methemoglobinemia. Indian Journal of Pediatrics 76(3); 315-316