According to the results of this study, nitrous oxide has no effect on pupillary diameter of patients under general anesthesia, so it could be safety used, in this regard, in ophthalmic operations.

Background: Postoperative pain in addicted patients is important because they are opioid tolerant, they have abnormal pain sensitivity and psychological disorders. Many modalities and combination of medications have been used to reduce the suffering of addicted patients' postoperative pain. There has been some evidence for the use of antipsychotics for such pain control. Objectives: The aim of this study was to compare the effect of morphine versus morphine/haloperidol on postoperative pain management in opioid-addicted patients undergoing orthopedic surgery. Patients and Methods:In this randomized double-blinded placebo-controlled trial, 101 addicted patients were divided randomly into two groups. For pain intensity, the categorical scale was marked by asking the patient at time zero in the recovery unit. The patients received 0.1 mg/kg morphine with either 20 mg haloperidol or 4 mL normal saline in the first episode of pain, according to the study groups. Pain ratings were obtained at 30-minute intervals till two hours. Pain scores were measured by the summation of numbers equal to pain severity in the categorical scale. The total morphine dosage was also assessed in the study. Results:The trend of decrease in the pain scores between the placebo and haloperidol groups was significant (P < 0.001) with higher slope in the haloperidol group. The trend of decrease in morphine consumption between the groups was significant (P < 0.001) with higher slope in the haloperidol group. In the placebo group, at hour two, 45 patients (90%) were pain-free, whereas in the haloperidol group, 51 patients (100%) were pain-free (P = 0.027). The total morphine dosages used in the two groups had a statistically significant difference (P < 0.001). Conclusions: Haloperidol together with morphine is beneficial in postoperative pain management in opium-addicted patients.