Measurement of surgical stress in anaesthetized children.

BACKGROUND: The surgical stress index (SSI), derived from a combination of heart rate (HR) and photoplethysmographic amplitude (PPGA) time series, is a novel method for continuous monitoring of intraoperative stress and has been validated in adults. The applicability of SSI and its constituents to monitoring children has not been previously evaluated. METHODS: In this controlled trial, 22 anaesthetized patients, aged 4-17 yr, undergoing strabismus surgery were randomized into two groups, Group LL and Group BSS. Patients in Group LL received topical conjunctival anaesthesia with a 1:1 mixture of lidocaine 2% and levobupivacaine 0.75%, and patients in Group BSS received balanced salt solution. RESULTS: Endotracheal intubation (n=22) increased median (range) SSI from 39.2 (22.6-55.6) to 53.6 (35.8-63.3) (P<0.001), decreased PPGA from 5.62 (2.79-9.69) to 5.27 (2.59-7.54)% (P=0.001), and increased the difference of response entropy (RE) and state entropy (SE) of frontal biopotentials (RE-SE) from 3.1 (0.06-9.1) to 5.7 (0.6-9.4) (P=0.01). Conventional haemodynamic variables also increased, median (range) HR from 72.9 (56.7-113.8) to 84.2 (60.4-124.8) beats min(-1) (P<0.001), and systolic non-invasive arterial pressure (S-NIBP) from 87 (78-143) to 103 (79-125) (P=0.007). When 3 min baseline before surgery was compared with 12 min of surgery, median (range) SSI increased from 43.3 (31.2-58.0) to 49.9 (39.3-57.2) (P=0.042) vs from 46.6 (26.8-57.8) to 52.1 (31.7-60.1) (P=0.024) and PPGA decreased from 6.60 (3.10-8.24) to 5.80 (3.03-7.65)% (P<0.001) vs from 5.51 (3.25-9.84) to 5.06 (3.08-8.99)% (P=0.042), in Groups LL and BSS, respectively, but SSI or other indicators did not differ significantly between the groups. CONCLUSIONS: SSI, PPGA, HR, NIBP, RE, and RE-SE detect autonomic responses to nociceptive stimuli in anaesthetized children undergoing strabismus surgery.

Isolation and characterisation of subcomplexes of the mitochondrial NADH:ubiquinone oxidoreductase (complex I).

Enzymically active subcomplexes were purified from bovine mitochondrial NADH:ubiquinone oxidoreductase (complex I) by sucrose-gradient centrifugation in the presence of detergents. These subcomplexes, named I lambda, IS, and I lambda S, catalyse ferricyanide and ubiquinone-1 (Q-1) reduction by NADH at similar rates to complex I, but do not catalyse the reduction of decylubiquinone. In addition, the Q-1 reductase activity of all the subcomplexes is insensitive to rotenone. Chemical and EPR analyses of the subcomplexes show that FMN and all the Fe-S clusters of complex I are present, but that the line shape of cluster 2 is modified. The smallest subcomplex, I lambda S, contains only approximately 13 subunits, as compared to approximately 22 in the previously described subcomplex I alpha [Finel, M., Skehel, J. M., Albracht, S. J. P., Fearnley, I. M. & Walker, J. E. (1992) Biochemistry 31, 11425-11434], but it retains the 75-, 51-, 49-, 30-, 24-, 23- (TYKY) and 20-kDa (PSST) subunits, which are suggested to form a functional core that comprises the EPR-detectable Fe-S clusters 1-4, and FMN. The structural and functional implications of such an arrangement are discussed.