Pupillometry is a non-invasive monitoring technique, which allows dynamic pupillary diameter measurement by an infrared camera. Pupillary diameter increases in response to nociceptive stimuli. In patients anesthetized with propofol or volatile agents, the magnitude of this pupillary dilation is related to the intensity of the stimulus. Pupillary response to nociceptive stimuli has never been studied under ketamine anesthesia. Our objective was to describe pupillary reflex dilation after calibrated tetanic stimulations in patients receiving intravenous ketamine. After written consent, 24 patients of our pediatric burn care unit were included. They received an oral morphine premedication (0.3 mg kg) 1 h before their scheduled daily dressing change. Just before the procedure, they received 1 mg kg of intravenous ketamine. Two minutes after this bolus, tetanic stimulations of incremental intensities were performed on the arm of each patient (5-10-20-30-40-60 mA, 60 s interval between stimulations). Pupillary diameter, heart rate and movements were recorded before and after each stimulation. Tetanic stimulations were associated with changes in pupillary diameter and heart rate. The magnitude of these changes was significantly influenced by the intensity of stimulation (ANOVA for repeated measures, p < 0.001). Movement was associated with a 32% increase in diameter (ROC curves, AUC 0.758) with 65% sensitivity and 77% specificity. In children, pupillary reflex dilation to nociceptive stimuli persists under deep sedation obtained with 1 mg kg of intravenous ketamine combined with a 0.3 mg kg oral morphine premedication, and its magnitude depends on the intensity of the stimulation. Our results confirm that pupillometry could be a relevant way to monitor nociception in anaesthetised subjects, including those receiving ketamine. Trial registration clinicaltrials.gov, NCT 02648412.

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Background and objectives: The objective was to assess the kinetics of postoperative bleeding after total hip or knee replacement, with or without administration of tranexamic acid, in order to anticipate red blood cell transfusion thresholds in the recovery room. Materials and methods: This was a prospective, observational, single-center study. All patients undergoing primary or revision total hip or knee replacement were enrolled for two months. Patients were managed using a multimodal strategy designed to reduce the need for red blood cell transfusion. Postoperative bleeding kinetics was assessed according to the drop of hemoglobin levels between the arrival in the recovery room and day one after surgery. Results: A total of 106 patients were included. The mean transfusion rate was 18%. Nadir hemoglobin levels were observed on day + 2, and about 60% of bleeding occurred during the postoperative period, with a drop of 1.2 ± 0.2 g/dL between the recovery room and day one for patients receiving tranexamic acid, and 1.9 ± 0.2 g/dL for those not receiving tranexamic acid (p=0.018). Discussion: In our center, the hemoglobin transfusion threshold in recovery room might be raised by 1 or 2 g/ dL depending on whether tranexamic acid is used.