Summary of the available case report 

Zoorob et al., 2023¹

The case involved an 80-year-old male with a medical history of chronic inflammatory demyelinating polyneuropathy (CIDP) and Guillain-Barré syndrome (GBS), alongside other comorbidities such as atrial fibrillation and hypertension. The patient received a single 50 mcg dose of intravenous (IV) fentanyl (approximately 0.49 mcg/kg) preoperatively for anxiolysis and analgesia prior to a planned mediport removal. Within minutes of fentanyl administration, the patient developed complete body rigidity, ceased verbal communication, and experienced apnea, resulting in a rapid drop in oxygen saturation to 70%. Efforts to establish ventilation were initially unsuccessful due to the rigidity of the chest wall, which prevented airway insertion. Propofol (70 mg) was subsequently administered, allowing for relaxation of the rigidity, successful airway management with a laryngeal mask airway, and subsequent stabilization. The report highlighted several notable findings, including the exceptional susceptibility of the patient to wooden chest syndrome (WCS) at a fentanyl dosage significantly lower than previously reported thresholds for rigidity development. This phenomenon is typically associated with rapid infusion, high doses, or extremes of age; however, the case underscores the role of possible underlying neurologic conditions, such as CIDP, that may predispose patients to such complications. Central mechanisms were implicated in the rigidity, likely mediated by mu-opioid receptor activation in the brainstem's locus coeruleus. 

A 35-year-old male undergoing laparoscopic cholecystectomy, categorized as ASA grade 1, received IV midazolam 1 mg followed by a bolus of fentanyl 100 mcg administered over 30 seconds. Shortly after administration, significant hypertension (BP 164/112 mmHg) and tachycardia (HR 110/min) were observed. During induction with propofol, bag-and-mask ventilation was found unsatisfactory, and subsequent oropharyngeal airway insertion revealed profound glottic narrowing (Cormack-Lehane grade 2b). Despite successful endotracheal intubation, the patient experienced silent chest syndrome, elevated airway pressures (35 cmH₂0), and failure to deliver adequate tidal volume, consistent with fentanyl-induced skeletal muscle rigidity. Post-intubation management involved transitioning to pressure-regulated volume control ventilation and administering IV succinylcholine, hydrocortisone, dexamethasone, and dexmedetomidine infusion. Intraoperative arterial blood gas analysis showed significant respiratory acidosis (pH 7.18, pCO2 90 mmHg). The patient's condition stabilized intraoperatively, with gradual resolution of elevated airway pressures, tachycardia, and hypertension. Extubation was uneventful, and follow-up ABG results normalized. 

A 61-year-old female patient presenting with pancreatitis-associated respiratory failure required endotracheal intubation and sedation using IV fentanyl and midazolam infusions. Fentanyl doses were incrementally increased to a maximum of 300 mcg/h on the fifth day of mechanical ventilation, at which point the patient experienced episodic hypoxia, tense abdominal musculature, facial cyanosis, and breath-holding spells. Physical and ventilator findings revealed markedly elevated airway pressures, absence of mucus obstruction, and resistance to bag-valve-mask ventilation. After the exclusion of other potential causes, the clinical picture raised suspicion for WCS. Immediate down-titration of fentanyl over three hours, supplemented with dexmedetomidine infusion, successfully resolved the episodes, allowing for extubation three days later. The highly lipophilic nature of fentanyl facilitates its CNS penetration, potentially contributing to this phenomenon. Although WCS was primarily observed in pediatric cases, this instance highlights its occurrence in adults exposed to high-dose fentanyl infusions. 

A 52-year-old male who had intravenously injected a mixture of opioids at a supervised consumption facility in Vancouver exhibited rapid-onset rigidity, characterized by clenched fists, stiff neck, cyanosis, and chest wall immobility, within minutes of injection. Ventilation with a bag-valve-mask at 25 L/min of oxygen was initiated, and 0.4 mg of subcutaneous naloxone was administered as the first-line intervention. Within two minutes, ventilation improved, and the patient's oxygen saturation normalized to 100%. Over the next six minutes, muscle rigidity subsided completely, and the patient resumed spontaneous breathing. Toxicological analysis of the drug preparation revealed the presence of fentanyl but no other opioids, cocaine, or methamphetamines. The incident underscores the diagnostic challenges in differentiating fentanyl-induced rigidity from other potential etiologies, such as toxicologic seizures, dystonic reactions, or hypoxic injuries, while emphasizing the role of naloxone in prompt reversal. It emphasized the need for ongoing education among at-risk populations about harm reduction strategies, including slow injection techniques and the importance of injecting in supervised environments. The authors also discussed gaps in knowledge, such as the potential recurrence of rigidity after naloxone reversal and the role of genetic predispositions, warranting further investigation.

A unique case of recurrent opioid-induced chest wall rigidity in a 76-year-old female patient following low-dose fentanyl administration was detailed. This phenomenon, though rare, was observed during post-surgical management for a periprosthetic femoral neck fracture. The patient, with comorbid conditions including asthma, coronary artery disease, and chronic kidney disease, initially experienced an abrupt increase in airway pressure and oxygen desaturation below 95% following a 50 mcg IV bolus of fentanyl prior to extubation. Despite no evidence of airway obstruction or wheezing, oxygenation remained impaired, and the event recurred hours later in the intensive care unit (ICU). Early resolution of symptoms was achieved through the administration of a muscle relaxant, specifically vecuronium bromide, which reduced airway pressure and restored ventilation efficacy. The publication underscores the challenges in differential diagnosis in mechanically ventilated patients with elevated airway pressures. While acute asthma exacerbation, bronchospasm, or upper airway obstruction are common considerations, the absence of wheezing and normal capnography pointed toward opioid-induced chest wall rigidity. Notably, this event was induced by a relatively low fentanyl dose rather than the higher doses typically associated with this complication. Management included discontinuation of opioid infusion and prompt use of muscle relaxants, resulting in successful extubation within 24 hours. 

A 76-year-old man had a history of stage IA non-small cell lung cancer with prior surgical resection and presented for lymph node evaluation following imaging and symptoms of hoarseness and cough. Sedation was achieved using IV midazolam and fentanyl in divided doses. Following administration of a cumulative fentanyl dose of 250 mcg and 5 mg of midazolam, the patient exhibited clenched hands and jaw, rigid chest wall, cessation of spontaneous ventilation, hypertension (208/134 mm Hg), and oxygen desaturation to 81%. Upon administration of naloxone (0.2 mg IV), rapid reversal of rigidity and restoration of effective ventilation were observed. The procedure was aborted, and the patient recovered fully, with plans for future biopsy under general anesthesia. Risk factors include rapid administration, higher doses, extremes of age, and underlying neurologic or metabolic diseases. The rigidity, mediated through central mechanisms involving regions such as the nucleus raphe pontis and caudate nucleus, compromises ventilatory compliance and may involve glottic closure, complicating ventilation. Management is centered on ventilatory support and reversal using naloxone or neuromuscular blocking agents. It noted that such reactions do not contraindicate future opioid use if precautions are taken.

Thio-Remi (n= 30)

Pro-Remi (n= 30) R

emi-Thio (n= 30) R

emi-Pro (n= 30)

^Desaturation is indicated by a SpO2<94%

*Comparisons among the four groups