Intrathecal morphine reduces blood loss during idiopathic scoliosis surgery: retrospective study of 256 pediatric cases.

BACKGROUND: This retrospective cohort study was designed to assess the impact of intrathecal morphine compared with no intrathecal morphine on blood loss and on hemodynamic stability during surgery for pediatric idiopathic scoliosis correction. METHODS: A retrospective review was done of 256 anesthetic charts who underwent scoliosis surgery between January 1993 and February 2012 by the same orthopedic surgeon. 128 patients were operated on before 2003 without intrathecal morphine (NITM group) and 128 were treated later on with intrathecal morphine (ITM group).Primary endpoints were a 20% decrease in blood loss in the ITM group and hemodynamic stability. RESULTS: Both groups were similar for age, girl/boy ratio, weight and duration of surgery. Blood loss was significantly greater in the NITM group: 1793.1 ± 964.3 ml vs 655.8 ± 323.0 ml (P < 0.0001). Overall mean decrease in blood loss was 63.4% between the NITM group and the ITM group. A significantly (P < 0.0001) greater number of patients from the NITM group (122) received blood transfusions as compared to the ITM group (30). The volume of blood transfused per patient was significantly greater in the NITM group (701.4 ± 492.5 ml) than in the ITM group (293.7 ± 170.9 ml) (P < 0.0001). Heart rate was stable intra-operatively in both groups. Variation in blood pressure >20% of baseline occurred more frequently in the NITM group (28.1%) than in the ITM group (14.8%) (P = 0.01). CONCLUSIONS: These data demonstrate that intrathecal morphine in pediatric surgical scoliosis correction significantly decreases intra-operative blood loss and transfusions and enhances blood pressure stability.

Prevention of emergence agitation after sevoflurane anesthesia for pediatric cerebral magnetic resonance imaging by small doses of ketamine or nalbuphine administered just before discontinuing anesthesia.

Magnetic resonance imaging (MRI) requires long-lasting immobilization that frequently can only be provided by general anesthesia in pediatric patients. Sevoflurane provides adequate anesthesia but many patients experience emergence agitation. Small doses of ketamine and nalbuphine provide moderate sedation but their benefits have subsided at the time of emergence. We hypothesized that delaying their administration until the end of the procedure would prevent emergence agitation without prolonging patient wake-up and discharge times from the postanesthesia care unit. We performed a double-blind study involving 90 patients (aged 6 mo to 8 yr) randomly allocated to 1 of 3 groups receiving either saline (S-group), ketamine (0.25 mg/kg) (K-group), or nalbuphine (0.1 mg/kg) (N-group) at the end of an MRI procedure under sevoflurane anesthesia. We evaluated emergence conditions, sedation/agitation status and completion of discharge criteria at 30 min. The three groups were comparable in age, sex ratio, physical status, and associated medical disorders. Emergence conditions did not differ significantly. There were significantly more agitated children, at all times, in the S-group and more obtunded patients at early times (5 and 10 min) in both K- and N-groups. All patients met discharge criteria at 30 min but significantly more children were awake and quiet in the K-group and still more in the N-group. In conclusion, small doses of ketamine or nalbuphine administered at the end of an MRI procedure under sevoflurane anesthesia reduce emergence agitation without delaying discharge. Nalbuphine provided better results than ketamine.

Pharmacokinetics of local anaesthetics in infants and children.

Amide local anaesthetics used for regional anaesthesia in paediatric patients are potent sodium channel blockers with marked stereospecificity, which consistently influences their action, especially their toxic action on the heart. At toxic concentrations, they induce severe arrhythmias with the potential for cardiac arrest. These agents are all bound to serum proteins, mainly to alpha(1)-acid glycoprotein (AAG), but also to human serum albumin. Protein binding ranges from 65% (lidocaine) to more than 95% (bupivacaine, ropivacaine). Because AAG is a major acute phase protein, its concentration rapidly increases when inflammatory processes develop, particularly during the postoperative period. Neonates and infants have a lower AAG concentration in serum as compared with adults; therefore, their free fraction of local anaesthetics is increased accordingly. This has important clinical implications since, at least at steady state, the toxic effects of local anaesthetics are directly related to the free (unbound) drug concentration. After injection into the epidural space, absorption into the bloodstream follows a biphasic process. The buffering properties of the epidural space are important and prevent a rapid rise in concentration. In infants and children, the epidural space seems to protect patients in a similar manner. Moreover, it has been observed that the peak plasma concentration (C(max)) of ropivacaine is delayed in infants and children when compared with adults. The time to C(max) decreases from 90-120 minutes in infants aged less than 6 months to 30 minutes in children aged more than 8 years. This delay in C(max) may also be related to the lower clearance observed in younger patients. Local anaesthetics are metabolised by cytochrome P450 (CYP). The main CYP isoforms involved are CYP3A4 for lidocaine and bupivacaine and CYP1A2 for ropivacaine. CYP3A4 is not mature at birth but is partly replaced by CYP3A7. The intrinsic clearance of bupivacaine is only one-third of that in adults at 1 month of age, and two-thirds at 6 months. CYP1A2 is not fully mature before the age of 3 years. Indeed, the clearance of ropivacaine does not reach its maximum before the age of 5 years. However, at birth this clearance is not as low as expected, and ropivacaine may be used even in younger patients.

Ropivacaine in infants and children.

PURPOSE OF REVIEW: Ropivacaine is considered less toxic than bupivacaine. In addition, at the low concentrations used for providing postoperative analgesia, ropivacaine seems to produce less motor blockade than bupivacaine. These two properties are of particular interest in paediatric practice. RECENT FINDINGS: In paediatric practice regional anaesthesia is usually performed under general anaesthesia, and postoperative analgesia was until recently the major concern for most practitioners. The question now is: what is the right concentration to provide adequate intraoperative anaesthesia when ropivacaine is used in combination with volatile anaesthetic agents? The low concentration of ropivacaine used for postoperative analgesia seems to provide adequate intraoperative anaesthesia when general anaesthesia with a 0.5 minimum concentration of volatile anaesthetic is used in combination. However, potential toxicity is still the subject of debate because ropivacaine clearance is low in infancy and early childhood. Ropivacaine has a longer absorption process than bupivacaine, which leads to a lower maximum peak concentration with ropivacaine than with bupivacaine either after central or peripheral blocks, thus increasing the safety of the drug. The addition of adjuvant drugs also permits lower concentrations of ropivacaine, while providing excellent analgesia. The addition of adrenaline at very low concentrations has recently been found to increase the quality of epidural analgesia. SUMMARY: Ropivacaine is now the reference drug for regional anaesthesia in paediatric patients, mainly because it is considered less toxic than bupivacaine and provides excellent postoperative analgesia even when used at low concentrations.