Is there implicit memory after propofol sedation?

Recent evidence indicates that implicit memory may be preserved during general anaesthesia. We tested for the presence of explicit and implicit memory in patients undergoing surgical procedures with local or regional anaesthesia and sedation with propofol. Initial i.v. boluses of propofol 0.5 mg kg-1 and fentanyl 1 microgram kg-1 were administered, followed by an infusion of propofol 50 micrograms kg-1 min-1. Administration of one or more doses of propofol 30 mg i.v. during operation was controlled either by the patient or the anaesthetist. At the start of the last skin stitch, patients were presented with a list of 15 stimulus words and the most frequently associated response. The infusion was then discontinued. After 1 h in the recovery area, all patients were tested for free recall, free association, cued recall and recognition on the list presented during surgery (critical list) and a matched list not presented (neutral list). Data of all patients without free recall (explicit memory) were analysed with repeated-measures analysis of variance. Of 36 patients, five demonstrated free recall. For the remaining 31 patients, cued recall and recognition showed no evidence of explicit memory. However, the free association tests demonstrated significant priming. The mean number of critical free associations was 6.6 (SEM 0.4) compared with 5.5 (0.4) neutral free association (P < 0.05). In the absence of explicit memory, implicit memory persists after intraoperative sedation with propofol.

Prospective survey of continuous versus single-injection spinal anesthesia in obstetrics.

Prior to the removal of spinal microcatheters from the market in 1992, these catheters were used extensively in the Obstetric Anesthesia Service at the Medical Center of Louisiana. We report on a prospective survey of the clinical application of single-injection versus continuous-catheter spinal anesthesia. Two hundred sixteen patients had single-injection anesthesia, and 218 had continuous-catheter anesthesia. No neurologic complications other than postdural puncture headache (PDPH) were encountered in either group. Five patients had PDPH after single-injection technique, and 8 patients had PDPH from continuous spinal anesthesia. Patients with diabetes were at higher risk for PDPH, and blacks were at lower risk (relative risks 4.35 and 0.31, respectively). Additionally, PDPH was associated with lower intraoperative urine output. No increased risk of complications was found after continuous spinal anesthesia with microcatheters.

Effect of patient-controlled sedation on recovery from ambulatory monitored anesthesia care.

Patient-controlled sedation (PCS) with propofol has been shown to be an effective means of conscious sedation during monitored anesthesia care. The purpose of this study was to assess both the intraoperative conduct and postoperative recovery of patients receiving propofol for conscious sedation, randomized to either PCS or anesthetist-controlled sedation (ACS). Forty-three patients scheduled for outpatient procedures requiring monitored anesthesia care were randomized to PCS or ACS. Both groups received an initial bolus of propofol 0.5 mg/kg and fentanyl 1 microgram/kg i.v., followed by an identical background infusion of propofol 50 micrograms/kg per minute. Subsequent doses of propofol 30 mg i.v. were either self-administered (PCS) or administered at the discretion of the anesthetist (ACS). Variables measuring hemodynamics, ventilation, saturation, and level of sedation were measured at baseline, after initial bolus of propofol and fentanyl, after skin incision, at last stitch, at admission to recovery, and 1 hour later. More propofol was used by the PCS group (P < 0.05). Finger-tapping was slower and responsiveness scores were lower in the PCS group at the end of the procedure (P < 0.05). More patients in the PCS group required oxygen supplementation (saturation < 90%) on admission to recovery (P < 0.05). At 1 hour after recovery admission, however, there were no differences between groups. These results indicate that when patients determine their own sedation, they are more sedated at the end of a procedure than when the anesthetist determines the level of sedation.

Pediatric extracorporeal membrane oxygenation in posttraumatic respiratory failure.

The leading cause of death in the pediatric population in the United States is trauma. A retrospective review of patients treated with extracorporeal membrane oxygenation (ECMO) for traumatic respiratory failure was performed. Eight children were treated at the Ochsner Medical Foundation and additional data on six children were available from the National Registry. Six children developed respiratory failure as a result of blunt trauma and eight as a result of near drowning. Standard venoarterial ECMO was used with a circuit very similar to that used in neonatal ECMO. Vascular access was via the common carotid artery and the internal jugular vein. Ventilatory support was weaned to minimal settings during ECMO. Central hyperalimentation and systemic antibiotics were used in all of the cases. Four of six children survived in the blunt trauma group; three of eight children survived in the near drowning group. Although significant conclusions cannot be drawn from a small group of patients the average pre-ECMO PO2 for survivors was 87 mm Hg, whereas for nonsurvivors the average PO2 was only 46 mm Hg. Ventilatory support for both groups was not remarkably different, and the average PCO2 was lower in the nonsurvivor group. The cause of death in this group of patients is usually multisystem organ failure. In the four patients treated at Ochsner who did not survive, all had positive blood cultures and presumed systemic sepsis. ECMO has been demonstrated to be very successful in neonatal respiratory failure. Predicting mortality and morbidity in pediatric respiratory failure has been more difficult.(ABSTRACT TRUNCATED AT 250 WORDS)