Approximately 50,000 patients per year present at emergency departments (EDs) because of carbon monoxide (CO) intoxication. The hypothesis of this study was that the half-life of CO and the regression period of complaints could be reduced more rapidly by applying oxygen with the Continuous Positive Airway Pressure (CPAP) modality using a non-invasive mechanical ventilator.

The patients were divided into Group 1 and Group 2 in terms of the treatment method applied. Patients in Group 1 received FiO2 1.0 15 l/minute oxygen at room temperature for at least 30 minutes with a non-rebreather mask. Patients in Group 2 received FiO2 1.0 oxygen at 12 cmH2O pressure with non-invasive mechanical ventilation for at least 30 minutes with an oronasal mask in the CPAP modality.

The median values (interquartile range) of carboxyhemoglobin (COHb) levels at zero and 30 minutes of patients were 19% (8) and 14% (6) in Group 1 and 22% (8) and nine percent (3) in Group 2; a median difference of six percent (2) was detected in Group 1 and of 13% (4) in Group 2 in the first 30 minutes (P <.001). When the symptoms of the patients were examined, the median values of Group 1 and Group 2 at zero minutes were both eight units and at 30 minutes were five and three units, respectively. A decrease of five units was determined in the median of Group 2 in the first 30 minutes, and a decrease of two units in the median of Group 1 (P <.001).

The use of CPAP was determined to more rapidly reduce COHb level as opposed to high-flow oxygen therapy. It is also thought that it may enable earlier discharge by reducing the duration of the emergency follow-up since it provides a faster improvement in the symptoms of the patients.

The newer cyanide antidote, hydroxocobalamin, due to its pigmentation, has been found to cause interferences in some laboratory assays. Co-oximetry may also be affected by hydroxocobalamin, leading to false elevations in hemoglobin concentration, methemoglobin, carboxyhemoglobin, and false decreases in oxyhemoglobin. The Masimo Radical-7 is a medical device that performs noninvasive oximetry and estimates hemoglobin (Hb) concentration and percent carboxyhemoglobin (COHb), methemoglobin (MetHb), and oxyhemoglobin saturation (O2Hb).

The study sought to determine the effect of hydroxocobalamin on noninvasive measurement of hemoglobin indices using the Masimo Radical-7 monitor.

Seven asymptomatic volunteers who were unexposed to cyanide had baseline heart rate (HR), blood pressure (BP), and oximeter measurements recorded followed by an infusion of five grams of hydroxocobalamin over 15 minutes. The above parameters were subsequently recorded at: 5, 10, 15, 30 and 60 minutes post infusion. Data were analyzed by calculating the area under the curve (AUC) for each variable and comparing the results to expected values by paired t tests. Expected AUC values were calculated by extrapolating baseline values across the entire time period.

The mean differences from baseline values with 95% confidence intervals and t tests of mean difference were: SBP: 11 mm Hg (95% CI, 0-22; P = .051); HR: -9 (95% CI, -15 to -3; P = .01); Hb: -0.1 (95% CI, -0.7 to 0.4; P = .57); O2Hb: 0 g/dL (95% CI, -1 to 1; P = .41); COHb: -1 (95% CI, -3 to 1; P = .25); MetHb: -0.2 (95% CI, -0.3 to 0; P = .03).

After infusion of hydroxocobalamin there was a significant elevation of systolic blood pressure and decrease in heart rate. There were no significant differences in Hb, O2Hb, and COHb. Although percent methemoglobin concentrations were statistically lower, the authors feel this difference is of trivial clinical significance.

The administration of hydroxocobalamin does not significantly impact noninvasive oximetry.

CashinB, MatlockA, KangC, ReynoldsP, WillsB. Effect of Hydroxocobalamin on Surface Oximetry in Nonexposed Humans. Prehosp Disaster Med. 2013;28(4):1-3.

Carbon monoxide (CO) toxicity is a significant health problem. The use of non-invasive pulse CO-oximetry screening in the emergency department has demonstrated that the rapid screening of numerous individuals for CO toxicity is simple and capable of identifying occult cases of CO toxicity.

The objective of this study was to extend the use of this handheld device to the prehospital arena, assess carboxyhemoglobin (SpCO) levels in emergency medical services (EMS) patients, and correlate these levels with clinical and demographic data.

This was a retrospective, observational, chart review of adult patients transported to hospital emergency departments by urban fire department EMS ambulances during a six-week period. Each ambulance used a non-invasive pulse CO-oximeter (Rad-57, Masimo Inc.) to record patients' COHb concentrations (SpCO) along with the standard EMS assessment data. Spearman's Rank Correlation tests and Student's t-tests were used to analyze the data and calculate relationships between SpCO and other variables (age, gender, respiratory rate, heart rate, mean arterial pressure, and oxygen saturation measured by pulse oximetry).

A total of 36.4% of the patients transported during the study had SpCO documented. Of the 1,017 adults included in this group, 11 (1.1%) had an SpCO >15%. There was no correlation between SpCO and heart rate, ventilatory rate, mean arterial pressure, and oxygen saturation.

Screening for CO toxicity in the EMS setting is possible, and may aid in the early detection and treatment of CO-poisoned patients.