Mechanism: neuraxis dopamine antagonism (Viscomi and Bailey)
Mild syndrome:
(1) mild hoarseness
(2) mild muscle rigidity
(3) alert and responsive
More severe syndrome:
(1) severe rigidity of the chest wall ("wooden chest syndrome")
(2) impaired spontaneous respirations or apnea with hypoxemia and hypercapnia
(3) difficult ventilation
(4) severe rigidity of the abdominal muscles
(5) severe rigidity of the limb muscles, with flexion of the upper extremities and extension of the lower extremities (Streisand et al)
(6) loss of consciousness
(7) rigidity of the oral muscles (tongue jaw)
(8) rigidity of the neck muscles
(9) severe laryngospasm
Patients at risk:
(1) high doses of parenteral opioids (although the syndrome can occur with relatively small doses)
(2) epidural opioid
(3) neonates in the intensive care unit
(4) patients with Parkinson's disease
(5) concurrent therapy with haloperidol or other butyrophenone (Viscomi and Bailey)
(6) previous history of the reaction
(7) no pretreatment with neuromuscular blocking agents
Interventions to reverse:
(1) administer a neuromuscular blocking agent
(2) prompt treatment with naloxone
