Abstract Introduction Fentanyl, a synthetic opioid analgesic, is frequently used in intensive care units for its rapid onset and potent analgesic properties. However, its use is not without risks, one of the most concerning being the potential for inducing muscle rigidity, particularly in the thoracic and abdominal regions, leading to significant respiratory compromise. This phenomenon, often referred to as wooden chest syndrome (WCS). A case of a patient intubated for acute hypoxemic respiratory failure who developed WCS in a medical intensive care unit is described here. Case Presentation An 84-year-old male presenting with altered mental status and decreased oral intake for two weeks. On presentation, the patient was hypotensive to 43/33, hypoxic, SpO2 of 77%, tachycardic to 105 bpm. CT of the chest was notable for right upper lobe consolidation. He was admitted to the medical ICU for septic shock secondary to pneumonia with worsening acute hypoxemic respiratory failure, requiring intubation. He was initially sedated on fentanyl 25-50 mcg/hour for a goal Richmond-Agitation-Sedation Scale score of -1 to -2. The next day, the patient had a tense and distended abdomen on physical exam with decreased bowel sounds, concerning for ileus. Abdominal x-ray showed no dilated bowel or signs of obstruction (Figure 1). Fentanyl was discontinued, and he was started on ketamine as he appeared uncomfortable without change in oxygen requirement. The following day, his abdomen exam was soft and non-distended, with decreased bowel sounds, after discontinuation of fentanyl. Discussion Opioid-induced chest wall rigidity was first described by Hamilton and Cullen in 1953 while studying the effects of opioid on respiratory depression. Common predisposing factors include extremes of age and high doses of fentanyl. The two most common factors associated with the development of WCS are opioid lipophilicity and the speed of injection. Although WCS primarily affects the chest wall, fentanyl-induced rigidity may also involve abdominal musculature, producing a distended, firm abdomen with decreased bowel sounds. This pseudo-ileus presentation can mislead clinicians toward gastrointestinal pathology when the true mechanism is neuromuscular, as in this case, where rigid chest and abdomen lead to suspected ileus, which resolved after discontinuation of fentanyl 5. Fentanyl-induced muscle rigidity commonly results in respiratory compromise and ventilator asynchrony in mechanically ventilated patients. However, the patient here did not exhibit increased ventilatory requirements or evidence of asynchrony despite presumed rigidity. Recognizing WCS allows for prompt resolution through early discontinuation of the opioid, preventing unnecessary diagnostic testing or invasive interventions. This abstract is funded by: None
Mohamed et al. (Fri,) studied this question.