An air medical team is called to transport a 13-year-old female with altered mental status and irregular breathing. The patient was found unconscious at home in the garage by her older sister. She had a rag in her hand that smelled of gasoline and was surrounded by cans of paint and furniture varnish. She had vomited prior to EMS arrival.
When the flight crew arrives at the emergency department, they encounter a very anxious patient with stridor and obvious accessory muscle use. Her respiratory rate is between 22 and 26 breaths per minute. Room air pulse oximetry was reported to be 89 percent. She is currently on high-flow oxygen via face mask with an oxygen saturation of 93 percent. Heart rate is 146 beats per minute with a blood pressure of 142/96. Her lips and nail beds are “dusky” and skin is cool. Electrolyte abnormalities include potassium of 5.9 mEq/L and an associated anion gap of 19. Serum blood glucose is 58. Toxicology screen is negative for narcotics, amphetamines and barbiturates. Capillary blood gas reading reveals a pH of 7.25, PCO2 25 mmHg, PO2 45 mmHg, HCO3 16 mg/dl and a saturation of 71 percent.
The culprit
Inhalant abuse has many names: huffing, bagging, air blasting, gassing. Inhalants are volatile substances that produce chemical vapors that are inhaled to induce an alteration in consciousness. While many other substances of abuse can be inhaled, the term “inhalants” is used to describe substances that primarily and commonly used by inhalation only. Inhaled substances encompass a broad range of chemicals found in hundreds of different products that may have different pharmacological effects.
The patient in this scenario was suspected of inhaling gasoline, paint and varnish; all of which contain the aromatic hydrocarbon toluene. A hydrocarbon is a compound that contains the elements hydrogen and carbon, and is identified by the covalent bonds formed between the carbon and hydrogen atoms. The best known hydrocarbons are aromatic hydrocarbons (named after their sweet aroma). The basic structure of an aromatic hydrocarbon is a ring of 6 carbon atoms joined by alternating single and double covalent bonds. The “building block” of aromatic hydrocarbons is benzene (C6H6). Other aromatic hydrocarbons include toluene (C7H8) and naphthalene (C10H8).
Inhaled hydrocarbons have a dis-inhibiting euphoric effect. This hydrocarbon “high” makes them a popular substance of abuse. Patients present with CNS symptoms such as slurred speech, dizziness and ataxia. Respiratory and ventilatory drive may be compromised. Presentation may resemble that of alcohol intoxication. In some patients, an initial component of CNS stimulation may present as agitation, tremor or seizure. Additionally, high concentrations of hydrocarbons sensitize the myocardium to catecholamines, predisposing patients to ventricular tachycardia and fibrillation. These arrhythmias are responsible for a syndrome known as “sudden sniffing death.” Additionally, gas exchange in the lungs is impaired secondary to direct damage, displacement of oxygen, and washout of surfactant.
Why inhalants?
Literally hundreds (over 1000 identified) of household and office products have been identified as substances of inhalant abuse and are easily accessible by adolescents. Inhalants are also relatively inexpensive compared to other street drugs. For school-aged children and adolescents, inhalant abuse can be viewed as an extracurricular activity of sorts. These substances rapidly affect the central nervous system and, depending on what and how much is inhaled, the effects can wear off relatively quickly (before dinnertime with the parents). Another factor may be that general perception of harm from inhalant use is relatively low. Kids (and often adults) don’t think of inhalants as being as dangerous as street drugs because they often aren’t educated as such.
What is most alarming about inhalant abuse is that a great proportion of abusers are not adolescents. One national survey indicates that about 3 percent of U.S. children have tried inhalants by the time they reach fourth grade. Current National Institute on Drug Abuse statistics report that 1 in every 10 eighth graders are using inhalants. The In the Monitoring the Future study, an annual NIDA-supported survey of the nation’s secondary school students, states that eighth-graders regularly report the highest rate of “current,” “past year” and “lifetime” inhalant abuse; 10th- and 12th-graders report less abuse.
About 18 percent of eighth graders, 17 percent of 10th graders, and 14 percent of 12th graders surveyed in 2004 say that they have sniffed or huffed inhalants at least once in their lives.
Care of these patients
Whether in the field, emergency department or ICU, scene awareness and safety is paramount. Avoiding exposure to abused substances and protecting yourself, your crew and your patient from harm is of utmost importance. Beware of bizarre patient behavior and wear protective barriers to prevent personal dermal, respiratory or mucous membrane exposure while providing care. Arguing with or exciting the abuser when they are under the influence may cause them to become aggressive or violent.
Keep patients calm to prevent arrhythmias from myocardial sensitization. Treat arrhythmias according to local protocols and ACLS algorithms. Apneic or comatose patients may require aggressive airway management. All patients should receive supplemental oxygen since inhalant use compromises oxygen transport. Anecdotal reports suggest early intubation with positive end expiratory pressure may avoid aspiration and alveolar collapse in cases of severe hydrocarbon exposure. No definitive studies have yet demonstrated improved outcomes with this treatment approach, when compared to conservative respiratory management.
Treat hypotension with intravenous crystalloids. If possible, avoid catecholamines, as these agents have the possibility of inducing arrhythmias. Critical care transport teams may be tasked with continuing advanced supportive therapies such as sophisticated ventilatory management, invasive hemodynamic monitoring, management of disseminated intravascular coagulation, electrolyte management, or treatment of rhabdomyolysis.
Conclusion
The patient in this scenario requires aggressive therapy in order to support vital functions. Ensuring adequate oxygenation and ventilation, management of acidosis, and appropriate hemodynamic support should be in the plan of care. While identifying the exact substance that was inhaled isn’t necessary to provide adequate treatment, making it part of the differential is useful in ensuring crew and patient safety.
The best management for the abuse of inhaled substances is prevention and education. Critical care transport teams can play a pivotal role in educating their communities in the dangers of inhalant abuse. The following web sites provide useful information for developing educational programs.
