asthma attack. The vast majority of patients with aspirin/ NSAID-exacerbated sensitivity are able to tolerate selective COX-2 inhibitors, though caution is recommended in those susceptible to severe asthma attacks. Beta-blocker-induced bronchospasm can be abrupt and rapidly fatal [3, 4, 166– 168]. This form of catastrophic asthma can be dif cult to treat, as ongoing β-blockade may blunt the response to β2-agonist therapy. In 1996, the UK Medicines Control Agency had been noti ed 51 reports of bronchospasm that occurred as an adverse reactions to propranolol; 13 of the cases were fatal [166]. The bronchospasm was fatal in ve of the six patients who gave a history of preexisting asthma [166]. Novel selective β-blockers may not induce measurable bronchospasm and may even confer a survival advantage to chronic obstructive pulmonary disease patients [169]. However, it is good practice to exercise due caution with this class of medications in asthmatics.

Inhaled/insuffated heroin, cocaine, and crack cocaine has coincided with a sizable increase in the rate of severe asthma attacks, admissions in emergency departments or death [3, 4]. In one study of 152 acute asthma cases, there were 42 cocaine and 47 heroin users [170]. Intubation rate was higher in cocaine or heroin users (21.4% and 17.0%, respectively) compared to nonusers, in whom the rate was 2.3%. Likewise, the prevalence of heroin insuffation was found to be 56% in a sequential ICU admission study in 23 patients [171]. In appropriate settings, a urine drug screen is indicated in the patient with acute asthma attack [171].

A popular test in young people is the “Dry Cinnamon Inhalation Challenge” whereby the adolescent subject attempts to inhale a large spoonful of the compound [172]. As not enough saliva is available to humidify and swallow the amount of ne cinnamon powder, inhalation, aspiration, and acute bronchospasm may follow. Foreign body bronchiolitis and ILD may also develop in the aftermath. The challenge seems less popular nowadays, and no further report has emerged since 2013 [172].

Peri-operative Emergencies (Table 42.8)

Few situations cause more distress and carry more risk than acute intraoperative catastrophic respiratory events, as the time allotted to understand and solve the issues is typically short or extremely short. Respiratory emergencies can be the direct consequence of drugs taken preoperatively at baseline or of anesthetic or nonanesthetic compounds given during the surgical or endoscopy procedure. Anaphylaxis (due to anesthetic agents, neuromuscular blocking agents, contrast media, latex or antibiotics), angioedema from angiotensin-­ converting enzyme inhibitors (see Table 42.6), explosive coughing from fentanyl, acute severe bronchospasm from anesthetic agents or muscle relaxants, pulmonary edema or ARDS as a complication of narcotics, dextran or transfusion of blood, plasma or proteins, nonthrombotic pulmonary

embolism from aprotinin or methacrylate, protamine-­ induced acute pulmonary vascoconstriction, embolism of lipids or fat from propofol or from drug llers, or drug-­ induced methemoglobinemia [3, 4]. The intraoperative occurrence elevates the severity of the event, in that diagnosis must be both rapid and accurate, and the course of the surgical procedure can be interrupted, delayed or compromised. Examples of scenarios that require emergent recognition and expeditious management include patients on preoperative ACEI who develop pre-, intra-, or postoperative acute angioedema and upper airway obstruction following the trauma of airway intubation [173] and intraoperative bronchospasm that can occur in patients who use beta-­ blockers and/or muscle relaxing agents.

Preoperative chloroquine, dapsone, metoclopramide, sulfonamide or recreational inhalants (amylor isobutyl-nitrite), intraoperative benzocaine, lidocaine, nitroglycerine, nitro compounds or nitric oxide (among 82 drugs or chemicals known to cause methemoglobinemia [3, 4]) may lead to methemoglobin formation, a condition where one and up to four of the four ferrous (Fe2+) iron ions linked to each heme in the hemoglobin molecule become oxidized into the ferric state (Fe3+) [174]. Fully oxidized Fe3+ is largely unable to bind and carry dioxygen (O2). The condition manifests with the progressive or rapid onset of slate-grey cyanosis resistant to high-fow dioxygen, a chocolate-brown hue of blood that does not turn red when exposed to room air or when bubbled with oxygen [175]. Signi cant levels of methemoglobin (25–40% of total hemoglobin while normal is below 3%) are associated with low or erratic pulsed saturation (SpO2) readings (60–70% range) despite normal or above normal measured (dissolved) partial pressure of dioxygen, depending on the FiO2 the patients is exposed to. True hemoglobin saturation and the varied Hb species need be measured (not calculated or assumed from PaO2 measurement), otherwise the diagnosis can be missed. A signi cant saturation gap (calculated minus measured SaO2) is suggestive of methemoglobinemia [3, 4]. Multi (four) wavelength sensors are appropriate for measuring methemoglobin and carboxyhemoglobin in addition to oxyand deoxyhemoglobin or SaO2 can be measured spectrophotometrically in vitro. Methemoglobinemia in excess of 50–60% can induce arrhythmia, central nervous system symptoms, seizures, and coma. Metabolic acidosis can develop with MetHb levels in excess of 70%, that are potentially fatal. Treatment is with high fow inhaled oxygen and the reducing agent methylene blue administered at a rate of 1.5 mg/kg in 5 min, after which disappearance of discoloration, normalization of SpO2, and a drop in methemoglobin should be observed within 1 h [176]. Careful monitoring of methemoglobin levels is required, as methemoglobin may reform. Readministration of methylene blue can be needed, but high dosages may cause paradoxical methemoglobin reformation. Failure to obtain response may

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Table 42.8  Potentially catastrophic intraand peri-operative drug-induced and iatrogenic emergencies

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Reactions Induced-Drug Emergent and Rare, Unusual, on Emphasis With Disease: Respiratory Induced/Iatrogenic-Drug  42

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