A prospective, observational study comparing postoperative residual curarisation and early adverse respiratory events in patients reversed with neostigmine or sugammadex or after apparent spontaneous recovery.

Six years ago, a study performed in our department reported that the incidence of postoperative residual curarisation (PORC) was 39%. The reassessment of neuromuscular monitoring and reversal of neuromuscular block in routine anaesthetic practice is relevant now that sugammadex has become available. The incidence of PORC, defined by a train-of-four (TOF) <90%, was evaluated at post-anaesthesia care unit (PACU) arrival in patients whose neuromuscular block had been reversed with neostigmine or sugammadex and those in whom reversal was felt unnecessary (adequate spontaneous recovery). During the PACU stay we recorded the oxygen saturation (SpO(2)) at arrival, episodes of SpO(2) <90%, airway manoeuvres and/or stimulation required to maintain SpO(2) >90%, and the need for re-intubation. In total, 624 patients were studied. Fifteen percent (66/441) of the patients who were not reversed, 15% (21/139) of those who were reversed with neostigmine and 2% (1/44) of those who received sugammadex exhibited PORC (P=0.06). No patient required reintubation in the PACU. The absence of neuromuscular monitoring and pharmacological reversal before extubation were not associated with PORC. A TOF <90% at PACU arrival was not associated with SpO(2) <90% during the PACU stay. Body mass index was the only independent predictor of SpO(2) <90% during the stay in the PACU. These findings indicate that in recent years, the incidence of PORC, defined by a TOF <90%, has dramatically decreased in our institution. The differences in PORC were not statistically significant between patients who received sugammadex for reversal and patients with spontaneous recovery or neostigmine reversal.

Air-oxygen mixtures in circle systems.

STUDY OBJECTIVE: To determine the effect of different air-O(2) mixtures and fresh gas flows (FGF) on the relationship between the delivered (F(Del)O(2)) and inspired O(2) fraction (FIO(2)) in a circle system. STUDY DESIGN: Randomized clinical study. SETTING: Large teaching hospital. PATIENTS: 160 ASA physical status I, II, and III patients undergoing a variety of cardiovascular procedures with general endotracheal anesthesia. INTERVENTIONS: 160 patients were randomly assigned to one of 20 groups (n = 8 each), depending on the combination of total FGF (0.5, 1, 2, 4, or 8 L/min) and air-O(2) mixture used (ratios of 4/1, 3/2, 2/3, or 1/4), corresponding to a F(Del)O(2) of 0.37, 0.53, 0.68, and 0.84. For each combination of FGF and air-O(2) mixture, FIO(2) after equilibration was compared with F(Del)O(2). MEASUREMENTS AND MAIN RESULTS: With any air-O(2) mixture with a FGF < or = 2 L/min, FIO(2) became lower than F(Del)O(2). Because FIO(2) decreased below 0.25 after 13 and 26 minutes in the first two patients of the 4/1 0.5 L/min air-O(2) group, this study limb was terminated. CONCLUSIONS: When using air-O(2) mixtures in a circle system, FIO(2) becomes lower than the F(Del)O(2) with FGF < or = 2 L/min. The relative proportion of O(2) in the FGF has to be increased accordingly.

The ADU vaporizing unit: a new vaporizer.

UNLABELLED: We determined the performance of the vaporizer of the ADU machine (Anesthesia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N(2)O mixture, and air) and fresh gas flow (0.2 to 10 L/min) on vaporizer performance were examined with variable concentrations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer's output. In addition, the effects of sudden changes in fresh gas flow and carrier gas composition, back pressure, flushing, and tipping were assessed. Vaporizer output depended on fresh gas flow, carrier gas composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3-10 L/min for isoflurane, within 10% of dial setting with fresh gas flows of 0.5-5 L/min for sevoflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L/min for desflurane. Outside these fresh gas flow ranges, output deviated more. The effect of sudden changes in fresh gas flow or carrier gas composition, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer. IMPLICATIONS: The ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.

Maintaining sevoflurane anesthesia during low-flow anesthesia using a single vaporizer setting change after overpressure induction.

STUDY OBJECTIVE: A sevoflurane vaporizer dial setting of 1.9% was previously found to maintain the end-expired sevoflurane concentration (Et(sevo)) at 1.3% during maintenance of anesthesia for procedures up to one hour with an O(2) FGF of 1 L/min. We examined whether applying these parameters could simplify low-flow sevoflurane anesthesia after overpressure induction using two slightly different techniques. DESIGN: Prospective clinical study. SETTING: Large teaching hospital. PATIENTS: Sixteen patients receiving general anesthesia for a variety of peripheral procedures. INTERVENTIONS: Anesthesia was induced with overpressure with sevoflurane (8%) in an 8 L. min(-1) O(2)/N(2)O mixture (30%/70%). After a laryngeal mask airway (LMA) was placed, fresh gas flow (FGF) was lowered to 1 L. min(-1) using O(2) and N(2)O (FiO(2) 30%) with patients breathing spontaneously. In group I patients (n = 8), the vaporizer dial was set at 1.9% at the same time the FGF was lowered. In group II patients (n = 8), the vaporizer was turned off until Et(sevo) had decreased to 1.3%, after which the dial was set at 1.9%. The course of Et(sevo) in the two groups was examined. MEASUREMENTS AND MAIN RESULTS: In group I, Et(sevo) after 3 min was 4.88 +/- 1. 12%. Et(sevo) decreased slowly after reduction of FGF to 1.83 +/- 0. 19%, 1.59 +/- 0.18%, and 1.52 +/- 0.19% at 10, 20, and 30 min, respectively. In group II, Et(sevo) after 3 min was 4.34 +/- 0.84%, and decreased more rapidly after reduction of FGF to 1 L. min(-1) than in group I. Et(sevo) was 1.40 +/- 0.09%, 1.40 +/- 0.11%, and 1. 38 +/- 0.13% at 10, 20, and 30 min, respectively. CONCLUSIONS: After high-flow overpressure induction with sevoflurane, a single change in vaporizer setting (to 1.9%) and FGF (to 1 L. min(-1)) suffices for the Et(sevo) to approach the predicted Et(sevo) (1.3%) within 10-15 min; thereafter the Et(sevo) remains nearly constant. As expected, the predicted Et(sevo) is attained slightly faster when the vaporizer is temporarily turned off. Clinically applying previously derived pharmacokinetic parameters simplifies low-flow sevoflurane anesthesia after overpressure induction.

Coasting after overpressure induction with sevoflurane.

STUDY OBJECTIVE: To evaluate the clinical feasibility of using a coasting technique to temporarily maintain anesthesia after overpressure induction with sevoflurane. STUDY DESIGN: Prospective clinical study. SETTING: Large teaching hospital. PATIENTS: 12 ASA physical status I, II, and III patients receiving general anesthesia for a variety of peripheral procedures. INTERVENTIONS: After overpressure induction of anesthesia with sevoflurane (8%) in an O(2)/N(2)O mixture, the fresh gas flow (FGF) was lowered to 0.5 L/min and the vaporizer was turned off (coasting). MEASUREMENTS AND MAIN RESULTS: After priming a circle system with sevoflurane (8% sevoflurane vaporizer setting in 6 L/min O(2)/N(2)O [33%/66%] for 30 s), patients took several vital capacity breaths from the mixture until loss of consciousness. After 3.4 +/- 0.7 min, depth of anesthesia was considered adequate for laryngeal mask airway (LMA) insertion, and FGF was reduced to 0.5 L/min (33% O(2), 66% N(2)O) and the sevoflurane vaporizer was turned off. The end-expired sevoflurane concentration (Et(sevo)) decreased from 5.8 +/- 1.3% just before insertion of the LMA to 0.97 +/- 0.22% at 20 minutes. CONCLUSIONS: After overpressure induction with sevoflurane, coasting during minimal flow anesthesia (FGF 0.5 L/min) is a simple technique that can maintain anesthesia for short procedures (less than 15 to 20 min), or can be used as a bridge or an adjunct to other low-flow techniques.

Patient-controlled epidural analgesia with sufentanil following caesarean section: the effect of adrenaline and clonidine admixture.

Sixty patients, scheduled for Caesarean section were randomly allocated to receive by the epidural route in a double-blind fashion one of the following patient-controlled analgesia mixtures for the relief of postoperative pain: sufentanil 2 micrograms.ml-1 in 0.9% sodium chloride, sufentanil 2 micrograms.ml-1 + adrenaline 2.5 micrograms.ml-1, or sufentanil 2 micrograms.ml-1 + clonidine 3 micrograms.ml-1. Patient-controlled analgesia settings were a basal infusion rate of 2.5 ml.h-1, an incremental dose of 2.5 ml, a lockout interval of 10 min and a 1-h limit of 10 ml. Whereas patient demographics and pain scores between the groups were not different, the 24-h consumption of sufentanil was significantly lower in the groups receiving a combination (167.5 SD 45 and 139.1 SD 31.9 micrograms for the adrenaline and clonidine groups respectively) as compared to the plain sufentanil regimen (208.2 SD 38.9 micrograms). Although sufentanil requirements were the lowest in the clonidine admixture group, there were no differences with regard to sedation as compared to the plain sufentanil group. The quality of sleep appeared to be significantly better in the sufentanil/adrenaline group despite a significantly lower degree of sedation and higher incidence of pruritus. Treatment of pruritus with naloxone did not seem to influence the quality of analgesia.

Combined continuous spinal-epidural anaesthesia with a single interspace, double-catheter technique.

A double catheter, single interspace combined spinal-epidural anaesthetic was performed in 12 ASA grade 3 patients. The technique failed in one patient in whom the intrathecal catheter could not be inserted satisfactorily. In another patient, the epidural catheter was accidentally placed intrathecally. The maximum height of the block obtained with hyperbaric lignocaine or bupivacaine was below T10 in all patients and there were no adverse cardiovascular changes. As opposed to a classical combined spinal-epidural block, this technique is most suitable for very debilitated patients. The advantages are the ability to titrate the intrathecal dose of the local anaesthetic to achieve the desired dermatomal level and to test the correct position of the epidural catheter before injecting drugs intrathecally.