<prompt> Biphasic respiratory depression is usually seen after:NeuroleptanaesthesiaRegional anaesthesiaHalothane anaesthesiaIsoflurane anaesthesia  <response>: Neuroleptanaesthesia is produced by droperidol fentanyl. Fentanyl after IV injection is sequestered by stomach in significant amounts, released into circulation after 3-6 hours and can produce second phase of respiratory depression i.e., biphasic respiratory depression. 