2006 OPEN FORUM Abstracts
NON-INVASIVE CARBOXYHEMOGLOBIN MONITORING: SCREENING EMERGENCY DEPARTMENT PATIENTS FOR CARBON MONOXIDE EXPOSURE
Robert Partridge, MD, MPH, Kerlen J Chee, MD, Selim Suner, MD, Andrew Sucov, MD,
Gregory D. Jay, MD, PhD. Department of Emergency Medicine, Rhode Island
Hospital, Brown Medical School, Providence, RI.
Background: Carbon monoxide (CO) poisoning is a significant cause of
mortality and morbidity. Symptoms of CO
poisoning can be non-specific, so the clinician must have sufficient suspicion
to order a venous carboxyhemoglobin (COHb) level.
Assessing COHb levels non-invasively on all
emergency department (ED) patients provides an opportunity to identify CO
poisoning and determine the prevalence of occult cases.
OBJECTIVES: Assess baseline COHb levels in ED
patients using a non-invasive device and correlate these levels with known
clinical and demographic data.
Methods: A retrospective
chart review was conducted on all adult patients presenting to an urban
academic ED (annual adult census 95,000 patients). One month prior to chart review, non-invasive
Pulse CO-oximeters (Rad-57, Masimo, Inc.) were placed at ED triage to assess
baseline COHb levels as part of the standard ED
triage process. Baseline COHb levels were correlated with age, gender, smoking history, mode of
transportation, and vital signs. Wilcoxon Rank Sum tests and ANOVAs were used to analyze
correlation data with p< 0.05 considered significant.
Results: Of 6861consecutive ED patients over a 39 day period, 4955 (72.2%) had COHb
levels documented at triage. Mean age
was 44.6 (19.4 SD) years, 49.5% were female, and 31.7% were
smokers. Mean COHb
level was 3.59% (3.26% SD) with a range of 0-22%. Males had higher COHb
levels than females [3.81% (3.35% SD) vs. 3.37% (3.16% SD)], but there was a greater proportion of males smokers than female
smokers (36.3% vs. 26.9%). Smokers
exhibited higher COHb levels [5.10% (3.70% SD) vs.
2.88% (2.76% SD)]. 28.4% arrived at the ED by ambulance. The mean COHb level
was lower for ambulance patients [3.16% (3.12% SD)], vs. for patients arriving
by private vehicle [3.77% (3.25% SD)] and for patients arriving on foot [4.54%
(3.74% SD)]. However, there were fewer
smokers among patients arriving by ambulance (27.4%) than those arriving by
private car (30.7%) or by foot (49.2%).
There was no correlation between COHb level
and heart rate (r=0.02), respiratory rate (r=0.01), SpO2 (r=-0.002) and MAP (r=-0.001). In a larger
cohort over 3 months, there were 9 cases of unsuspected CO toxicity (COT)
identified in patients with non-specific symptoms or unrelated chief
complaints. Toxic COHb levels ranged from 16-33% and
were confirmed with serum values. The source of CO exposure in patients with
COT was later identified, and was usually in the home. All patients with
presumed COT (e.g. smoke inhalation) were also identified with the non-invasive
device. 13 patients were identified with false positive values, however, no
false negatives were observed.
Conclusions: Non-invasive
testing for COT can be performed at ED triage.
There is no correlation between age, vital signs and non-invasive COHb levels. Smokers
had significantly elevated COHb levels compared to
nonsmokers. Males had higher levels than
females, possibly due to a higher proportion of male smokers. Ambulance patients had lower COHb levels, possibly due to a lower proportion of smokers
arriving by ambulance. Unsuspected COT
may be identified using non-invasive COHb screening,
and the prevalence of COT may be higher than previously recognized.