Ambulatory Anesthesia for a Case of Idiopathic Bronchiolitis Obliterans

Abstract

Bronchiolitis obliterans is rarely described in the nonlung transplant anesthesia literature. This case report describes a 27-year-old female patient with idiopathic bronchiolitis obliterans and dental anxiety who safely received intravenous deep sedation using diphenhydramine, dexmedetomidine, and ketamine in an ambulatory community dental clinic. This report outlines the anesthetic plan developed following a thorough preoperative assessment and review of the key anesthetic considerations of idiopathic bronchiolitis obliterans (eg, potential respiratory complications and appropriateness for the ambulatory dental environment) and discusses the careful anesthetic management of this patient using deep sedation to facilitate comprehensive restorative dentistry.

Bronchiolitis obliterans (also known as constrictive bronchiolitis, idiopathic constrictive bronchiolitis, cryptogenic obliterative bronchiolitis, popcorn workers' lung, or popcorn lung)¹ is a very rare obstructive respiratory disease characterized by pathologic luminal plugging with chronic inflammatory granulation tissue or luminal obliteration by fibrosis.² Histologically, bronchiolitis obliterans affects the small noncartilaginous airways and spares the parenchymal lung tissue.^2–4 Similar pulmonary conditions and their characteristic features as detailed in the literature are presented (Table 1).

Table 1.

Bronchiolitis Obliterans and Similar Pulmonary Conditions^{1,2,8,9,21–25}*

Pulmonary Condition	Etiology of Bronchiolitis Obliterans	Histological Characteristics	Chest X-Ray	CT Scan	Pulmonary Function Test
Bronchiolitis obliterans (popcorn lung, popcorn workers' lung)	Occupational/environmental exposure to toxins, gases, ash, fiberglass	Irreversible destruction of lung architecture peribronchiolar fibrosis (luminal plugging, granulation tissue) compressing and obliterating the airway	Unremarkable chest x-ray or nonspecific findings (hyperinflation, vascular attenuation in lower or mid-lung zones)	Areas of decreased parenchymal attenuation with decreased vessel size segmental, subsegmental bronchial dilatation, centrilobular branching structures	Fixed obstructive pattern
e-cigarette or vaping, product use-associated lung injury (EVALI)	Inhalational exposure to diacetyl-containing agents	Bronchioalveolar lavage fluid in lipid-laden macrophages seen with red O staining	Diffuse bilateral pulmonary opacities	Diffuse bilateral ground-glass opacities; basilar predominance; occasional subpleural or lobular sparing	Obstructive pattern
Swyer-James (Macleod)'s syndrome	Postviral infection in early childhood	Obstruction and emphysematous changes (bronchiectasis)	Unilateral hyperlucency, unilateral emphysematous changes	Unilateral small lung with air trapping	Reduced lung volumes without obstruction
Bronchiolitis obliterans organizing pneumonia	Postbacterial infection	Reversible damage of alveoli and alveolar ducts, minimal or no involvement of bronchioles Lung architecture remains intact Presence of dominant lesion of organizing pneumonia	Patchy consolidation in a diffuse peripheral distribution	Nodules, nonseptal linear or reticular opacities and bronchial dilatation, peribronchial distribution of consolidation	Restrictive pattern; possible obstructive component
Bronchiolitis obliterans syndrome	Cytotoxic drugs postlung transplantation	Patchy submucosal fibrosis involving bronchioles lumen occlusion	Unremarkable chest x-ray or nonspecific findings	Air-trapping, persistent lucency, bronchial wall thickening common in lower lobes; occasional bronchiectasis and centrilobular opacities	FEV1 < 75% FEV1/FVC < 5th percentile of CI RV > 120% or RV/TLC > 120% of baseline

^*CI indicates confidence interval; CT, computed tomography; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; RV, residual volume; TLC, total lung capacity.

This case report outlines the anesthetic considerations and management of a patient with bronchiolitis obliterans and pulmonary function test (PFT) results consistent with severe obstructive pulmonary disease (Tables 2 and 3) undergoing deep sedation for restorative dental treatment. Additionally, this patient historically experienced reactive airway-like episodes requiring regular use of an inhaled corticosteroid and long-acting bronchodilator combination and occasional use of a short-acting bronchodilator and oral steroids for respiratory exacerbations. The specific details about this case are described.

Table 2.

Spirometry Abbreviations

Abbreviation	Spirometry Term
FEV1	Forced expiratory volume in 1 second
FEF50	Forced expiratory flow at 50%
FEF75	Forced expiratory flow at 75%
FVC	Forced vital capacity
TLC	Total lung capacity
RV	Residual volume
CI	Confidence interval
S	Second
L	Liter

Table 3.

Pulmonary Function Tests from 2019—Spirometry Measurements*

Spirometry	Patient's Values	Reference Values	% of Reference	Lower Limit	Upper Limit
FVC (L)	2.88	3.86	74	3.2	4.6
FEV1 (L)	1.05	3.35	31	2.8	3.9
FEV1/FVC (%)	37	85		76	95
FEF50% (L/S)	0.41	4.53	9	65	% of Ref
FEF75% (L/S)	0.18	1.95	9	65	% of Ref

^*FEF50% indicates forced expiratory flow at 50%; FEF75%, forced expiratory flow at 75%; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; L, liter; S, second.

CASE REPORT

A 27-year-old female patient (height, 158 cm; weight, 95 kg; body mass index, 38.1 kg/m²) presented with dental anxiety, idiopathic bronchiolitis obliterans diagnosed at age 8, and the need for comprehensive dental treatment. Her medical history also included generalized anxiety, depression, allergic rhinitis, chronic fatigue, and obesity, and she reported regularly enjoying light walking, which approximates 3 metabolic equivalents.⁵ Her medications included a combined mometasone and formoterol (Zenhale) inhaler (200 mcg + 5 mcg/actuation) with 2 actuations administered twice daily, consistent with the higher recommended dosing range.⁶ She also reported using a salbutamol (albuterol) inhaler (200 mcg/actuation) with 1 actuation 2 to 3 times per day when needed to manage a mild persistent cough. The patient denied any notable sputum production or experiencing any fevers or night sweats. Upon further questioning, she reported responding well to nebulized salbutamol (albuterol) and short courses of oral prednisone whenever she had experienced dyspnea in the past. Her last course of prednisone was 2 months ago in the summer. Known airway triggers included summer heat and humidity. Furthermore, she ingested cannabidiol 2 to 3 times weekly and vaped marijuana once per month for her other comorbidities. She occasionally used xylometazoline nasal sprays and saline rinses for allergic rhinitis and reported no known drug allergies.

During her preanesthetic consultation and physical examination, she appeared well and not in distress. Assessment of her airway revealed full range of motion (cervical and temporomandibular joints), mouth opening and thyromental distance of 3 fingers' width, and a Mallampati score of 1. Her vitals at that time were as follows: blood pressure 125/75 mm Hg, heart rate 106 beats per minute (bpm), and resting oxygen saturation (SpO₂) 96% on room air. Upon auscultation, her breath sounds were reduced but heart sounds were normal. She demonstrated normal capillary refill, and her fingers were not clubbed.

The patient's respirologist (pulmonologist) was consulted and reported stable spirometry results from 3 months prior to the planned dental treatment (Table 3; Figure 1). These PFT data were consistent with significant obstructive pulmonary disease as evident by her reduced forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and a FEV1/FVC ratio of 37%. A previous chest computed tomography scan (Figure 2) obtained from her medical record revealed extensive mosaic attenuation and airway thickening and bronchiectasis. There was evidence of minor airway plugging but no suggestion of nontuberculous mycobacterial infection. Prior chest radiograph (Figure 3) was viewed as unremarkable and the study was stated to be within normal limits, which is typical of bronchiolitis obliterans (Table 1).

Figure 1.

Pulmonary function tests from 2019: Flow-volume loop demonstrating an obstructive pattern, severe airflow reduction with reduced forced vital capacity suggestive of gas trapping; and estimated healthy reference for comparison.

Figure 2.

Axial CT scan from 2019 revealing extensive mosaic attenuation, airway thickening, and bronchiectasis. CT indicates computed tomography.

Figure 3.

Unremarkable anteroposterior chest radiograph from 2015, which is typical of the disease.

The patient also reported during the preoperative evaluation a previous general anesthetic for dentistry that was aborted when she experienced rapid desaturation/hypoxemia and required urgent intubation after intravenous induction of general anesthesia. This event reportedly happened at another dental office; however, those anesthetic records could not be obtained. No dentistry could be performed during that failed anesthetic. She was categorized as American Society of Anesthesiology Physical Status Class 3 due to her stable medical comorbidities and electively scheduled for restorative dentistry procedures under deep sedation at a community dental clinic using total intravenous anesthesia (TIVA).

The patient presented on the day of surgery, and after confirming that she followed the preanesthetic instructions (fast for 12 hours, refrain from cannabidiol use, maintain regular use of the Zenhale inhaler), she was instructed to take 2 puffs of salbutamol (albuterol) just prior to entering the operatory. Standard anesthetic monitors were placed, consisting of a 3-lead electrocardiogram, noninvasive blood pressure cuff, pulse oximeter, and capnography by nasal cannula. Her baseline vital signs were stable: blood pressure 132/83 mm Hg, heart rate 101 bpm, normal sinus rhythm on lead II, respiratory rate 12 bpm, and SpO₂ 92% on room air at rest that improved to 96% when prompted to take deep breaths preoperatively. Her SpO₂ further improved to 100% with 5 L/min of supplemental oxygen delivered by nasal cannula before induction. A 22-gauge peripheral IV was secured on the dorsum of the right hand and administration of a Lactated Ringers solution was initiated. The patient was slowly induced with IV boluses of diphenhydramine 50 mg and ketamine 50 mg, plus a dexmedetomidine 70 mcg bolus given over 10 minutes that was converted to a continuous infusion of 0.7 mcg/kg/h with an infusion pump and titrated to achieve deep sedation. She maintained a patent unobstructed airway and spontaneous ventilations, achieving an SpO₂ of 98 to 100% with supportive neck and shoulder rolls to facilitate head-tilt/chin-lift positioning. Restorative dental procedures were completed following placement of a Molt mouth prop and administration of 2% lidocaine (72 mg) with 1:100,000 epinephrine (0.036 mg) via maxillary infiltration. Intraoral fluids were actively removed by simultaneous use of a high-volume suction and a saliva ejector. Dental isolation was done using cotton rolls, foil-covered paper triangles (Dri-Angles), and folded 4 × 4 gauzes, which were periodically replaced when soiled. The patient occasionally demonstrated swallowing and intermittent vocalizations whenever the ketamine dissociation waned and the depth of sedation lightened, transitioning from deep to moderate. A bolus of ketamine 25 mg was given 35 minutes into the restorative procedure to re-establish dissociation. The patient tolerated the sedation and restorative dental procedures very well and remained stable throughout, with no episodes of desaturation, hypoxemia, respiratory depression, apnea, or coughing. The duration of the procedures was 55 minutes at which point the dexmedetomidine infusion was stopped and the patient regained consciousness within 20 minutes. She recovered uneventfully and comfortably with vital signs returning to baseline: blood pressure, 106/65 mm Hg; heart rate, 92 bpm; respiratory rate, 18 bpm; SpO₂, 92% on room air that increased to 96% when prompted to take deep breaths. The IV was discontinued after a total of 500 mL of fluid was administered. The patient was subsequently discharged home 60 minutes after anesthesia end-time. Follow-up phone call determined the patient recovered uneventfully at home and she reported having no memory of the procedure.

DISCUSSION

Preoperative evaluation of obstructive lung diseases such as bronchiolitis obliterans requires a thorough workup including a comprehensive patient interview and physical examination, consultation with the patient's respirologist (pulmonologist), and review of PFTs and radiographic studies (ie, computed tomography scan and/or chest radiograph). A review of current literature on this rare condition in addition to reviewing existing documented anesthetic practices helped to guide the preoperative evaluation and anesthetic planning for this patient. Furthermore, this patient's body mass index of 38.1 kg/m² prompted the review of anesthetic considerations for obesity as well.

Bronchiolitis obliterans is also known as obliterative bronchiolitis, constrictive bronchiolitis, and bronchiolitis obliterans organizing pneumonias.^4,7 This disease may be associated with autoimmune disorders. Acquired forms of bronchiolitis obliterans can occur after the following: environmental exposure to inhaled toxins, gases, ash, fiberglass, electronic cigarettes or “vaping e-liquids”; infectious exposure to bacteria or viruses; or lung or hematopoietic stem cell transplantation.^7,8 The etiology of this patient's disease is unknown. The incidence of bronchiolitis obliterans has not been reported with consistency in the literature. Patients may first present with vague flu-like signs or symptoms or it may be an incidental diagnostic finding.⁴ Management can involve intermittent courses of corticosteroids, antibiotics, and inhaled bronchodilators.⁴

Electronic cigarettes or e-cigarettes have become the most commonly used nicotine product among Canadian⁸ and American youth in recent years. These popular electronic devices aerosolize liquid substances for inhalation, which can include nicotine, tetrahydrocannabinol, cannabidiol, and other flavoring agents that may contain diacetyl. The use of e-cigarettes or “vaping” of diacetyl-containing agents are known to cause pulmonary toxicity. The patient in this case vaped marijuana once per month, which likely negatively impacted her lung condition.

There is limited literature pertaining to the anesthetic considerations and management of bronchiolitis obliterans.^4,9 Furthermore, bronchiolitis obliterans is rarely described in the nonlung transplant anesthesia literature. Detailed history-taking, physical examination, and PFTs are important aspects of determining the patient's pulmonary status. This patient's FEV1 of 31% and FVC of 74% of normal values indicated that she had severe obstructive disease,¹⁰ but she was currently optimized on her inhalers and discontinued her recent course of prednisone. For patients with pulmonary disease of this severity, anesthesiologists should anticipate challenges like air trapping, ventilation-perfusion mismatching, and difficulty weaning/extubating if intubated anesthesia is planned.

Planned endotracheal intubation outside of a hospital setting would likely not be recommended for a patient with bronchiolitis obliterans due to limited resources and facilities. Furthermore, potentially severe postoperative pulmonary complications, such as delayed weaning from mechanical ventilation, could be exceedingly difficult to manage in a nonhospital setting, requiring prolonged monitoring or even hospital admission postoperatively, which may not be readily available.¹¹ Optimal ventilation strategies for an intubated patient with bronchiolitis obliterans would include monitoring for high peak pressures, preventing rapid arterial hypoxemia due to apnea, maintaining positive end-expiratory pressure to improve functional residual capacity (FRC), and sustaining continuous positive airway pressure in recovery.⁴ Patients who are unable to deep breathe, cough freely, exhibit dyspnea, or unable to maintain an oxygen saturation above 92% on room air would not be dischargeable.¹¹ Patients with bronchiolitis obliterans are also prone to respiratory infections, which may be exacerbated by prolonged endotracheal intubation.¹²

When determining this patient's fitness and appropriateness for receiving care in the community dental clinic setting, the risks versus benefits were weighed. This cooperative and participatory patient expressed her dental goals, a desire to attend a convenient dental clinic, and an understanding that safety was paramount. After her preoperative consultation, she was comfortable with the plan to use a dissociative TIVA approach to facilitate completion of her restorative dental needs. She was also comfortable with the anesthesiologist's low threshold for aborting the procedure and referring her to a hospital dental clinic, where wait-times were stated to be greater than a year which could potentially lead to further deterioration of her dental condition. In this case, patient rapport and a therapeutic partnership was established between the anesthesiologist and patient. A registered nurse also remained present to assist the dentist anesthesiologist in monitoring the patient throughout the case. There were shared objectives of administering doses of TIVA as low as reasonably achievable for restorative dentistry, performed by a separate dentist operator. Upper respiratory infections or reactive airway exacerbations were ruled out during the preanesthesia consultation and prior to confirming her appointment to avoid respiratory complications.¹³

Anesthetic Drug Selection

A key anesthetic goal was to avoid apnea, which ruled out the use of agents that cause respiratory depression. Therefore, benzodiazepines and opioids were intentionally avoided and the combination of dexmedetomidine, ketamine, and diphenhydramine was selected.

Dexmedetomidine.

Dexmedetomidine offered ideal properties for this procedural sedation; most notably, it did not cause respiratory depression. This α-2 adrenergic agonist maintains spontaneous ventilation and sustains baseline respiratory rates and volumes. Capnography values obtained by nasal cannula remained in a steady range of 37 to 43 mm Hg in this case. Other desired effects include hypnosis, analgesia, and sympatholysis.¹⁴ Sedative effects occur when the drug binds to receptors in the locus coeruleus. Peripherally, analgesia is achieved when the drug binds to α-2 adrenergic receptors and causes dose-dependent inhibition of C-fibers and Aα-fibers. Centrally in the locus coeruleus, α-2 adrenergic receptors inhibit nociceptive neurotransmission through the posterior horn of the spinal cord.¹⁵ At the presynaptic membrane, α-2 adrenergic receptors impair the release of norepinephrine thus impeding pain signals directed centrally.¹⁵ Acetylcholine release from the spinal interneurons increases nitric oxide synthesis and release, which may also play a role in analgesia.¹⁵ While sympatholysis is desired, dexmedetomidine may profoundly blunt the surgical stress response in some patients causing significant hypotension and bradycardia. These adverse effects were not observed in this patient, and she remained comfortable on doses stated in dexmedetomidine's drug monograph. For conscious sedation, it is recommended that a loading dose of 0.5 to 1 mcg/kg be given over 10 minutes and an infusion titrated in the range of 0.2 to 1 mcg/kg/h.¹⁶ Furthermore, dexmedetomidine is reported to have antiemetic effects, cause xerostomia, and possibly prevent delirium although further study is needed.¹⁴ This drug has primarily been used as a maintenance agent in intensive care and for awake fiberoptic intubation prior to surgical or diagnostic procedures. Dexmedetomidine's primary use in critically ill patients and those with difficult airways signaled its usefulness in bronchiolitis obliterans patients. In this case, deep sedation was achieved with the addition of ketamine and diphenhydramine.

Ketamine.

Ketamine, a N-methyl-D-aspartate receptor antagonist, was selected for its desired effects of amnesia, dissociative anesthesia, analgesia, maintenance of FRC, and bronchodilation.¹⁷ When administered intravenously, it has a rapid, smooth onset of action approximating 30 seconds and a predictable duration of effect approximating 10 to 20 minutes.¹⁸ For this case, a low IV dose of 50 mg (0.2–0.5 mg/kg) was used since a profound dissociative effect was not required for the restorative dental procedures. The mild cataleptic dissociation and nystagmus, observed during the case, is pharmacodynamically achieved by ketamine's disruption of the afferent impulses that traverse the sensory cortex through the thalamoneocortical and limbic systems of the central nervous system.¹⁷ Ketamine's analgesic benefit is believed to be partially mediated by opioid μ and δ receptors of the brain, spine, and peripheral nerves.^17,19 Bronchodilation is believed to be mediated by dose-dependent inhibition of extracellular calcium transport.¹⁷ Additionally, ketamine's maintenance of smooth muscle tone prevents atelectasis and shunting.¹⁷ Ketamine's potential adverse effects of hypersalivation and emergence delirium were not observed in this case, likely because low doses were used, coupled with dexmedetomidine.

Diphenhydramine.

Diphenhydramine, an antihistamine with anticholinergic effects, was used as an adjunctive agent because it offered central nervous system depression or sedation, antiemesis, and dried the nasopharyngeal passages. The patient reported a history of allergic rhinitis and reactive airways, which indicated its use would offer benefit. Diphenhydramine has been shown to benefit procedural sedation.²⁰

CONCLUSION

Rare medical conditions like bronchiolitis obliterans pose challenges for planning safe anesthesia, particularly in the ambulatory setting. Thorough review of the patient's medical history, obtaining accurate diagnostic information, and reviewing pertinent literature and available case reports aid in the formulation of an appropriate anesthetic plan. Principles of rational drug selection and patient-centered care were followed in this case to successfully manage this patient in a community dental clinic using deep sedation with a nonintubated TIVA technique of dexmedetomidine, ketamine, and diphenhydramine. The importance of forethought when planning for the preoperative, intraoperative, and postoperative periods is key to patient safety as well as treatment success.