01Approach to the Critical Patient/attcp35

Immediate priorities

›Initial stabilization

›Hazard control and decontamination

›Fresh air relocation

›Scene safety and carbon monoxide source control

›Airway and breathing

›High flow oxygen 100% via nonrebreather

›If airway compromise, intubation with FiO2 1.0

›Circulation

›Cardiac monitor and defibrillator readiness

›IV access and isotonic crystalloid for hypotension

›Neurologic status

›GCS trend

›If seizure, benzodiazepine first line

›Antidotes and special therapies

›Hyperbaric oxygen eligibility screen early

›If smoke inhalation, cyanide toxicity consideration

›Consult and escalation triggers

›Poison control and local toxicology

›Hyperbaric center early contact if criteria met

›ICU activation for coma, shock, refractory hypoxemia, malignant dysrhythmia

Key clinical decision points

›High risk features

›Altered mental status or syncope

›Seizure

›Chest pain or ECG ischemia

›Hypotension or dysrhythmia

›Severe metabolic acidosis

02History/hx28

Exposure and timeline

›Exposure context

›Enclosed space combustion

›Vehicle exhaust exposure

›House fire and smoke inhalation

›Workplace exposure

›Timing

›Duration of exposure

›Time since removal from source

›Prehospital oxygen duration

›Co exposed contacts

›Similar symptoms in others

›Pets affected

Symptoms and risk features

›Symptom pattern

›Headache

›Dizziness

›Nausea and vomiting

›Dyspnea

›Chest pain

›Confusion

›Syncope

›Seizure

›Vulnerability factors

›Pregnancy and gestational age

›Coronary artery disease

›Heart failure

›Chronic lung disease

03Physical Exam/exam21

Primary survey findings

›Vital sign abnormalities

›Tachycardia

›Hypotension

›Tachypnea

›Fever alternative diagnosis consideration

›Respiratory status

›Increased work of breathing

›Wheeze or bronchospasm with smoke inhalation

›Cardiovascular status

›Dysrhythmia

›Signs of poor perfusion

Neurologic and skin findings

›Neurologic status

›Mental status changes

›Focal neurologic deficit

›Ataxia

›Seizure activity or postictal state

›Skin and mucosa

›Soot or facial burns

›Oral soot

›Cyanosis alternative etiology consideration

›Cherry red skin unreliable clinical sign

04Differential Diagnosis/ddx21

Life threatening alternatives

›Hypoxia and toxic inhalation syndromes

›Cyanide toxicity from smoke inhalation

›Methemoglobinemia

›Hydrogen sulfide exposure

›Cardiopulmonary emergencies

›Acute coronary syndrome

›Pulmonary embolism

›Severe asthma or COPD exacerbation

›Neurologic emergencies

›Intracranial hemorrhage

›Ischemic stroke

›Status epilepticus

›Infection and metabolic

›Sepsis

›Hypoglycemia

›Meningitis or encephalitis

Mimics and common confounders

›Symptom overlap syndromes

›Viral syndrome

›Migraine

›Anxiety and panic

›Medication or substance intoxication

05Laboratory Tests/lt18

Core toxicology and acid base

›Carboxyhemoglobin evaluation

›Co oxymetry on venous or arterial blood

›Interpretation with baseline smoker levels consideration

›Acid base status

›Venous blood gas or arterial blood gas

›Serum lactate for tissue hypoxia

›Metabolic profile

›Electrolytes and renal function

›Glucose

End organ injury screening

›Cardiac injury

›High sensitivity troponin trend

›BNP optional for heart failure concern

›Rhabdomyolysis and hypoperfusion

›Creatine kinase if prolonged down time or coma

›AST and ALT as muscle and hepatic injury markers

›Pregnancy and smoke inhalation

›Pregnancy test in reproductive potential

›Co ingestion markers if smoke inhalation and severe lactic acidosis

06Diagnostic Tests/dt41

Scoring Systems

›Severity stratification framework

›Mild toxicity

›Headache and nausea only

›Normal mental status

›Moderate toxicity

›Syncope or confusion

›Persistent symptoms despite oxygen

›Severe toxicity

›Coma

›Seizure

›ECG ischemia or dysrhythmia

›Severe metabolic acidosis

›Limitations

›Carboxyhemoglobin level does not reliably correlate with severity

›Clinical features drive disposition and hyperbaric consideration

MRI

›Neuroimaging for delayed neurologic sequelae

›Indications

›Persistent neurologic deficit

›Delayed neurocognitive symptoms after apparent recovery

›Typical findings

›Basal ganglia and globus pallidus injury patterns

›White matter changes

›Operational considerations

›Not a first line ED test in stable improving patients

›Neurology follow up planning if delayed symptoms

07Disposition/dispo21

Level of care selection

›ICU indications

›Persistent altered mental status

›Seizure

›Hemodynamic instability

›Significant ECG changes or troponin elevation

›Severe metabolic acidosis

›Need for mechanical ventilation

›Ward or monitored bed indications

›Moderate symptoms with improvement on oxygen

›High risk comorbidities

›Pregnancy

›Smoke inhalation with airway monitoring needs

›Hyperbaric transfer criteria

›Candidate for HBO2 with feasible timing and safe transport

›Early contact with hyperbaric center for logistics and protocol

Discharge criteria

›Low risk discharge prerequisites

›Symptoms fully resolved on oxygen

›No neurologic deficits

›No cardiac symptoms and reassuring ECG

›Safe home environment with source remediation

›Follow up plan and return precautions

08Treatment/t61

Oxygen and supportive care

›Oxygen therapy

›Normobaric oxygen

›Delivery

›Nonrebreather mask 15 L per minute

›If inadequate ventilation, bag valve mask with FiO2 1.0

›Duration targets

›Continue until symptom free or CO poisoning ruled out

›Continue until carboxyhemoglobin trending toward baseline when available

›Physiologic rationale

›Accelerated carboxyhemoglobin elimination

›Improved dissolved oxygen delivery

›Ventilatory support

›If respiratory failure, intubation with FiO2 1.0

›Avoid hypoventilation and hypercapnia in depressed mental status

›Symptom directed care

›Antiemetic options

›Ondansetron IV 4 mg

›Repeat dosing per local protocol if persistent vomiting

›Seizure management

›Lorazepam IV 0.1 mg per kg

›Maximum single dose 4 mg

›If refractory, escalation to status epilepticus pathway

›Hypotension management

›Isotonic crystalloid bolus

›Adult 500 mL to 1000 mL reassess

›Pediatrics 10 mL per kg to 20 mL per kg reassess

›If persistent, norepinephrine infusion

09Special Populations/sp27

Pregnancy

›Maternal fetal risk amplification

›Fetal hemoglobin higher CO affinity and slower clearance

›Fetal injury possible at lower maternal carboxyhemoglobin

›Management modifications

›Early hyperbaric consultation

›Continuous fetal assessment per gestational age and local obstetric pathway

›If no HBO2, extended high flow oxygen course

›Disposition

›Admission for observation even with symptom improvement when exposure significant

›Obstetrics involvement for monitoring plan

Geriatric

›Higher complication risk

›Cardiac ischemia at lower exposure severity

›Reduced physiologic reserve

›Evaluation adjustments

›Lower threshold for troponin trending and telemetry

›Medication interaction and comorbidity review

›Disposition

›Lower threshold for admission due to delayed sequelae risk and home safety concerns

Pediatrics

›Pediatric presentation variability

›Irritability and lethargy

›Feeding intolerance and vomiting

›Weight based supportive dosing

›Fluids 10 mL per kg to 20 mL per kg bolus reassess

›Lorazepam 0.1 mg per kg IV for seizure

›Disposition and safety

10Background/b31

Epidemiology

›Exposure patterns

›Common sources

›Faulty indoor heating appliances

›Vehicle exhaust in enclosed or semi enclosed spaces

›Fires and smoke inhalation

›Cluster presentations

›Multiple household members with similar symptoms

›Seasonal increase in winter heating months

Pathophysiology

›Mechanisms of injury

›Hemoglobin binding

›Carboxyhemoglobin formation reduces oxygen carrying capacity

›Left shift of oxyhemoglobin dissociation curve impairs tissue oxygen delivery

›Cellular toxicity

›Mitochondrial dysfunction and impaired oxidative phosphorylation

›Oxidative stress and inflammatory cascades contributing to delayed neurologic sequelae

›Target organs

›Brain vulnerability to hypoxia

›Myocardial vulnerability to hypoxia and dysrhythmia

Therapeutic Considerations

›Oxygen kinetics

›Carboxyhemoglobin half life approximations

›Room air several hours

›100% oxygen about 60 to 90 minutes

›Hyperbaric oxygen markedly shorter

›Treatment rationale

›Rapid displacement of CO from hemoglobin

11Patient Discharge Instructions/pdi19

Copy discharge instructions

›Carbon monoxide exposure aftercare

›Do not return to the exposure site until it is declared safe by qualified services

›Arrange inspection and repair of suspected source

›Install and test carbon monoxide detectors

›Avoid using generators, grills, or fuel burning heaters indoors

›Medication and symptom plan

›Hydration and rest

›Avoid alcohol and sedatives for 24 hours

›Return to emergency care immediately for

›Chest pain

›Shortness of breath

›Confusion or unusual behavior

›New weakness, trouble walking, or vision changes

›Severe headache or persistent vomiting

›Fainting or seizure

›Follow up

›Primary care follow up within 24 to 72 hours

›Neurology follow up if any cognitive or neurologic symptoms recur

›Pregnancy specific follow up with obstetrics

12References/r12

Clinical guidelines and society statements

›Guideline sources

›CDC Clinical Guidance for Carbon Monoxide Poisoning updated July 8 2024

›ACEP Clinical Policy on Acute Carbon Monoxide Poisoning 2017 Level B recommendation

›Undersea and Hyperbaric Medical Society Carbon Monoxide Poisoning indications and resources

›Ontario Poison Centre Carbon Monoxide protocol December 2024

Evidence based reviews and coding systems

›Evidence and reviews

›StatPearls Carbon Monoxide Toxicity updated April 19 2025

›Emergency Care BC Carbon Monoxide Toxicity Treatment summary October 27 2020

›Medical coding alignment

›ICD 10 CM category T58 Toxic effect of carbon monoxide

›SNOMED CT 17383000 Toxic effect of carbon monoxide

›Build spec reference

Evidence & Review

Evidence & Review