Increased muscle responses to balance perturbations in children with cerebral palsy can be explained by increased sensitivity to center of mass movement.

BACKGROUND: Balance impairments are common in children with cerebral palsy (CP). Muscle activity during perturbed standing is higher in children with CP than in typically developing (TD) children, but we know surprisingly little about how sensorimotor processes for balance control are altered in CP. Sensorimotor processing refers to how the nervous system translates incoming sensory information about body motion into motor commands to activate muscles. In healthy adults, muscle activity in response to backward support-surface translations during standing can be reconstructed by center of mass (CoM) feedback, i.e., by a linear combination of delayed (due to neural transmission times) CoM displacement, velocity, and acceleration. The level of muscle activity in relation to changes in CoM kinematics, i.e., the feedback gains, provides a metric of the sensitivity of the muscle response to CoM perturbations. RESEARCH QUESTION: Can CoM feedback explain reactive muscle activity in children with CP, yet with higher feedback gains than in TD children? METHODS: We perturbed standing balance by backward support-surface translations of different magnitudes in 20 children with CP and 20 age-matched TD children and investigated CoM feedback pathways underlying reactive muscle activity in the triceps surae and tibialis anterior. RESULTS: Reactive muscle activity could be reconstructed by delayed feedback of CoM kinematics and hence similar sensorimotor pathways might underlie balance control in children with CP and TD children. However, sensitivities of both agonistic and antagonistic muscle activity to CoM displacement and velocity were higher in children with CP than in TD children. The increased sensitivity of balance correcting responses to CoM movement might explain the stiffer kinematic response, i.e., smaller CoM movement, observed in children with CP. SIGNIFICANCE: The sensorimotor model used here provided unique insights into how CP affects neural processing underlying balance control. Sensorimotor sensitivities might be a useful metric to diagnose balance impairments.

Postoperative analgesia for major abdominal surgery with continuous thoracic epidural infusion of bupivacaine with sufentanil, versus bupivacaine with morphine. A randomized double blind study.

Forty-six patients undergoing major abdominal surgery were given postoperative epidural analgesia for four days with bupivacaine-sufentanil or bupivacaine-morphine. Both groups received a bolus of 8 ml bupivacaine 0.5% followed after 30 minutes by an infusion of 20 ml/h bupivacaine 0.1%. The sufentanil group (group A: 21 patients) received a loading dose of 50 micrograms sufentanil and a continuous infusion of 5 micrograms/h sufentanil. The morphine group (group B: 25 patients) received no loading dose of morphine but only a continuous infusion of 0.5 mg/h morphine. Both regimens provided excellent analgesia, but the frequency of respiratory depression was much greater in group A (33% versus 4% in group B). This respiratory depression occurred in the first hours postoperatively, when the patients were still in the post-anesthesia care unit. There was also a high incidence of hypotension after the loading dose of bupivacaine 0.5%. Although we noticed a large incidence of pruritus, no patient needed naloxone reversal. In view of these side effects we recommend a lower loading dose of both bupivacaine and sufentanil.

The effects of the addition of sufentanil to 0.125% bupivacaine on the quality of analgesia during labor and on the incidence of instrumental deliveries.

In a double-blinded, randomized, prospective multi-center study of 695 women, we investigated whether epidural injection of sufentanil added to 0.125% bupivacaine with epinephrine (1:800,000) reduces the total amount of local anesthetic required, resulting in less motor blockade and reduced incidence of instrumental deliveries, and improves the quality of analgesia provided by this low concentration of local anesthetic without jeopardizing the safety of the baby. In addition, other potential benefits of sufentanil (such as decrease in the incidence of shivering) and side effects were examined. It was found that adding incremental doses of 10 micrograms sufentanil up to a maximum of 30 micrograms reduced the incidence of instrumental deliveries from 36 to 24% (P less than 0.01) and significantly improved quality and duration of analgesia without depressing the neurobehavioral status of the baby. No other benefits from adding sufentanil were found. The only side effect that occurred more frequently after sufentanil was pruritus. We conclude that epidural injection of 10-30 micrograms sufentanil added to 0.125% bupivacaine with epinephrine (1:800,000) improved the quality of analgesia during labor and reduced the incidence of instrumental deliveries without jeopardizing the safety of the baby.