The effects of isoflurane and desflurane titrated to a bispectral index of 60 on the cortical somatosensory evoked potential during pediatric scoliosis surgery.

In this study, we compared the effect of isoflurane and desflurane on the posterior tibial somatosensory evoked potential recorded by scalp electrodes during correction of idiopathic scoliosis in pediatric patients. Depth of sedation was controlled by maintaining bispectral index (BIS) at 60 throughout the study. Comparison of patients breathing desflurane and isoflurane showed an evoked cortical amplitude (N37-P45) of 0.53 +/- 0.3 microV versus 1.3 +/- 0.8 microV (P = 0.014), respectively. In addition to this comparison, a crossover design was included whereby the desflurane or isoflurane received in the first part of the study was changed to the other anesthetic. Substituting one anesthetic for another confirmed our initial finding that the cortical evoked amplitude is greater with isoflurane than with desflurane. No differential effect was found between desflurane and isoflurane on the evoked subcortical (N31-P34) amplitude or the P37 latency.

The clinical effect of mixing different proportions of rocuronium and mivacurium.

BACKGROUND: A synergistic effect has been described when rocuronium (Roc) and mivacurium (Miv) are combined in equal (i.e. 1:1) ED95 proportions at various total doses. We have investigated the effect of Roc or Miv alone and four different ratios (1:4, 2:3, 3:2 and 4:1) of Roc and Miv mixed to a total dose of 1.33 x ED95. The primary outcome is the ratio producing the maximum enhancement of duration of clinical effect. METHODS: Sixty-eight healthy children were anaesthetized with propofol, nitrous oxide and fentanyl. They then randomly received either Roc 0.4 (mg.kg(-1)), Miv 0.133 (mg.kg(-1)) or one of four Roc + Miv combinations (mg.kg(-1)): Roc 0.32 + Miv 0.027; Roc 0.24 + Miv 0.053; Roc 0.16 + Miv 0.08; and Roc 0.08 + Miv 0.106. The mechanical response of the adductor pollicis muscle to supramaximal stimulation of the ulnar nerve at the wrist was recorded. RESULTS: Duration of effect was greater in the combination groups than that predicted from the duration of Roc or Miv used alone. Duration was maximally increased around a 1:1 ratio (2:3 and 3:2) of Roc and Miv. The likelihood of achieving 100% block was greater in combination groups compared with Roc or Miv used alone. CONCLUSIONS: Combinations of Roc and Miv show a synergistic effect, which appears maximal as the mixture approaches a 1:1 ratio of their ED95s. This combination acted as if a larger effective dose of a single (new) drug had been given, but did not offer the advantage of both rapid onset and short duration of effect.

Methadone dosage for prevention of opioid withdrawal in children.

BACKGROUND: Opioids are frequently used for sedation in the Paediatric Intensive Care Unit (PICU). With time the dosing often increases because of tolerance. On cessation of the sedation there is a risk of the opioid withdrawal syndrome. The aim of our study was to evaluate methadone dosing as a risk factor for opioid withdrawal and to determine optimal dose and efficacy of methadone to prevent withdrawal. METHOD: We undertook a clinical, retrospective, chart review study. Data were analysed from the quality improvement initiative database of a tertiary-care 18 bed PICU. RESULTS: Data from 30 children who received an opioid infusion for >/=7 days and subsequently received methadone for opioid withdrawal (between January 2000 and July 2001) were analysed. Nurses documented the presence or absence of withdrawal signs daily. Our unit protocol has recommended converting the patient's opioid dose into fentanyl equivalents and a dose of methadone equal to the total daily dose of fentanyl to be given three times a day. Twenty patients had no or minimal withdrawal symptoms and 10 experienced significant withdrawal. Age, weight, PRISM score, lorazepam dose, muscle relaxant use and fentanyl dose were not statistically significantly between these groups. Receiver Operator Characteristics analysis showed that 80% of the suggested methadone dose was effective in minimizing withdrawal symptoms. The odds ratio for withdrawal with <80% of the predicted methadone dose was 21. CONCLUSIONS: Inadequate methadone is a risk factor for opioid withdrawal. A daily starting methadone dose equivalent to 2.5 times the daily fentanyl dose is effective in minimizing withdrawal symptoms.

Sedation monitoring of children by the Bispectral Index in the pediatric intensive care unit.

OBJECTIVE: To compare the Bispectral Index with clinical sedation assessment using the Ramsay score in normal sedated and paralyzed critically ill children. DESIGN: Prospective observational study. SETTING: Multidisciplinary 18-bed pediatric intensive care unit at a university-affiliated children's hospital. PATIENTS: A total of 48 pediatric intensive care unit patients requiring mechanical ventilation and sedation. Of these, 24 patients were not paralyzed. MEASUREMENTS AND MAIN RESULTS: Twenty-four pediatric intensive care unit children with normal mentation who were sedated and being ventilated in the intensive care unit were included in the study. The Ramsay score as assessed by the nurses was compared with the blinded Bispectral Index score. The regression coefficient between the Bispectral Index score and Ramsay score was 0.77 (p < 0.0001). The second group of patients included normal children similar to the previous group but paralyzed. The Ramsay score, as expected, was a poor tool for sedation assessment in a paralyzed patient. The nurse assessment only detected 8% of those patients at risk for awareness and recall (Bispectral Index score, > or = 80). Nurse assessment for oversedation (Bispectral Index score, < 40) was better with a sensitivity of 89.7% but a poor specificity of 38.6%. CONCLUSIONS: The Bispectral Index correlates well with the Ramsay score in the normal sedated child. The Ramsay score and bedside nurse assessment are inadequate for monitoring the depth of sedation in paralyzed children. The Bispectral Index is a useful adjunct in assessing sedation in a paralyzed patient.