Increased Susceptibility to Postoperative PCA Morphine-Induced Respiratory Depression in a Patient with an Undiagnosed Traumatic Porencephalic Cyst – A Case Report

INTRODUCTION: Patient-controlled analgesia with morphine is routinely used for postoperative pain management. Due to the safety profiles of the technique, which are patient/disease related or technique/equipment related, severe respiratory depression requiring opioid antagonists or airway management are uncommon. CASE PRESENTATION: The case of a patient with right colon carcinoma who was operated on for hemicolectomy under general anaesthesia and who presented with apnoea, after postoperatively receiving an initial bolus of 1mg of morphine. A large post-traumatic porencephalic cyst of the left brain hemisphere, previously undiagnosed, was found on the computed tomography scan. We excluded human errors, technique and equipment factors, and the patient did not have any other predisposing conditions like sleep apnoea, obesity, recent head injury or concurrent use of other sedatives. Previously the patient had been entirely asymptomatic, and her increased susceptibility to respiratory depression was the only clinical manifestation of porencephaly. CONCLUSION: Adult acquired porencephaly is seldom reported in the literature, clinical manifestations depending on the location and size of the cyst. In the present reported case, increased susceptibility to low-dose opioids might be associated with the structural and functional reorganisation of the brain after head trauma with the occurrence of the porencephalic cyst of the brain.