Effect Of Remifentanil Infusion Rate On Respiratory Function In Children With Upper Arm Fracture

BcakgroundMany children experience upper limb fractures due to their active nature and lacking with self-protection awareness and capacity. Such children usually are in perfect condition except injuries. Some of them need surgical treatments because of failure of manual reduction or fracture malunion. These operations are usually simple, low traumatic and short. Therefore special anesthesia methods should be considered. General anesthesia with endotracheal intubation is often safe and reliable. However, it'll invade children's air way, acquire more equipments money and time. It is not conducive to rapid turnover of operations. Traditional brachial plexus blocks combined with basal anesthesia are often selected in operations of children's arm. The drugs include propofol, ketamine, fentanil, et al. Ketamine is both sedation and analgesia efficiently. At the same time, it's side effects, such as more secretions of the respiratory tract, delaying awake and hallucinogens, often limit it's widely and repeatedly usage. Propofol has a powerful sedative effect with not a little analgesic effect. Fentanly is a strong analgesic agent with long lasting half time. It usually results in respiratory depression and chest wall rigidity. All the above mentioned characteristics inhibit their widely application in clinical practices in children.Compared with other opioids, Remifentanil is a new potent, synthetic opioid with an ultra short acting time and a stable, context-sensitive half-time. But the side effects of remifentanil are also intensive, including respiration depression, chest wall rigidity and moderate bradycardia. There are few studies about the usage of remifentanil on children. Can we effectively and safely apply it in children? In this study, we try to observe the effects of remifentanil on respiratory and circulatory functions in children with arm fractures, in an attempt to help applying remifentanil safely and reasonably. ObjectiveTo observe the effects of different remifentanil infusion rates on children's respiration and circulation functions, in an attempt to obtain both effective and safe infusing rates in them.MethodsA total of 25 children, ASAâ… toâ…¡, and ages 2¹2 years were selected in the study.All the children have arm-fractures and would be operated. The children were given basal anesthesia (midazolam 0.05⁰.08mg·kg^-1 iv; ketamine 1² mg·kg^-1 iv) before entering operation room. After entering operation room, Oxygen was given to every child by open veil (3L·min^-1). Remifentanil was administered in an initial infusion rate of 0.100μg·kg^-1·min^-1. Every five minutes an increasing rate of 0.025μg·kg^-1·min^-1. Increments were discontinued when children were respiration depression. Continuous monitored inclines including SpO₂, heart rate, noninvasive blood pressure, end tidal carbon dioxide and respiratory rate. When children happened respiration depression, assisted their ventilation with tight veil.When patients are infused opioids, the respiratory depression is usually defined as SpO₂<90% lasting 1 min, or PACO₂>52.63mmHg. But considering the poorer oxygen storage and the higher metabolism in children, I define the respiratory depression as≤99% in the condition of spontaneously breathing with oxygen by open veil.Brachial plexus blocks were performed with 1% lidocaine (8mg·kg^-1) after children's spontaneously ventilation recovered. Adjusting the infusion rate of remifentanil based on the extent of children's pian.Results1. All children went through the operation safety. Respiration depression occurred in three children at the rate of 0.175μg·kg^-1·min^-1; in eighteen children at the rate of 0.200μg·kg^-1·min^-1; in four children at the rate of 0.225μg·kg^-1·min^-1.2. Children's PETCO₂ raised from 35.3mmHg to 36.6mmHg when remifentanil infused at the rate of 0.100μg·kg^-1·min^-1(P<0.05), raised from 36.6mmHg to 38.4mmHg as the rate of raised to 0.125μg·kg^-1·min^-1(P<0.05), then didn't raised obviously. Children's RR dropped from 26.9bpm to 21.7bpm at the rate of 0.100μg·kg^-1·min^-1(P<0.05), dropped from 21.7bpm to 17.3bpm as the rate of raised to 0.125μg·kg^-1·min^-1(P<0.05), then didn't raised obviously.Children's HR dropped from 118.7bpm to 103.5bpm when remifentanil infused at the rate of 0.100μg·kg^-1·min^-1(P<0.05), then didn't raised obviously. MAP didn't alter obviously to the raise of remifentanil infuse rate.3. The maximum rate of remifentanil infusion was 0.225μg·kg^-1·min^-1 during the operation. The recover time of the children were 9.1±5.2min.Conclusion1. Remifentanil combine with brachial plexus block aneasthesia can use for operation on children's safely and effectively.2. When children Spontaneous breathing oxygen with opening veil. The dosages of remifentanil causing respiration depression are: ED₀₅=0.17023μg·kg^-1·min^-1; ED₅₀=0.18806μg·kg^-1·min^-1; ED₉₅=0.20775μg·kg^-1·min^-1.3. A reasonable rate of remifentanil for children is less than 0.180μg·kg^-1·min^-1.