Capnometry and the paediatric laryngeal mask airway.

The laryngeal mask airway (LMA), an alternative to tracheal intubation in certain situations, has gained popularity in recent years. Initially designed for use in adults it has now become available in suitable sizes for paediatric anaesthesia. The objectives of this study were to identify the preferred site of sampling the end-tidal carbon dioxide (PETCO2) with the LMA and to determine the accuracy of this recording when compared with arterial CO2 (PaCO2). We studied 30 healthy children, age one to five years and weighing between 10 and 25 kg undergoing minor surgery requiring mask anaesthesia. In each case, after induction of anaesthesia, the LMA was inserted under direct vision to eliminate the possibility of epiglottic airway obstruction. The fresh gas flow was provided by a Jackson Rees modification of an Ayre's T-piece and was determined according to the following formula: 3 x (1000 + (100 x body weight)) LPM. Blood pressure, ECG, O2 saturation, temperature and end-tidal gas concentrations were recorded. The measures of peak PETCO2 were taken at pre-determined distances from the elbow connector down the LMA shaft. During the sampling sequence an arterial blood sample was taken for gas analysis. The PaCO2 was 63.5 +/- 9.3 mmHg (mean +/- SD). At any given sampling site, mean PETCO2 values were less than PaCO2 (P < 0.05). However, in eight patients PETCO2 values measured at the distal site were higher than the PaCO2 (negative P(a-ET)CO2 gradients).(ABSTRACT TRUNCATED AT 250 WORDS)

Oral midazolam premedication for children with congenital cyanotic heart disease undergoing cardiac surgery: a comparative study.

To determine whether oral midazolam is a safe and effective alternative to our current standard premedication for children with cyanotic congenital heart disease (CCHD), 30 children aged 1-6 yr, scheduled for elective cardiac surgery, were studied. The children were randomly assigned to one of two groups: Group I received oral midazolam 0.75 mg.kg-1 30 min before separation from their parents in the surgical waiting area, and Group II received oral or rectal pentobarbitone 2 mg.kg-1 at 90 min, and morphine 0.2 mg.kg-1 and atropine 0.02 mg.kg-1 im at 60 min before separation. Heart rate, haemoglobin oxygen saturation (SpO2) and anxiolysis and sedation scores were recorded at four times during the study: at baseline (immediately before premedication), immediately after administration of the premedication, at separation of children from parents in the waiting area and at the time of application of the face mask in the operating room. We found that in Group I, anxiolysis improved at separation from parents compared with baseline (P < 0.05) and sedation increased both at separation and on mask application (P < 0.05), whereas in Group II anxiolysis did not change at any time and sedation increased only at separation (P < 0.05). Intramuscular injection of morphine produced a transient decrease in mean SpO2 (from 84% to 76%) (P < 0.05) that did not occur after ingestion of oral midazolam. The results of this study indicate that oral midazolam is a safe and effective replacement for the standard premedication for children with CCHD undergoing cardiac surgery and avoids the decrease in SpO2 associated with im injections.

Should all children with suspected or confirmed malignant hyperthermia susceptibility be admitted after surgery? A 10-year review.

Children otherwise suitable for same-day discharge may be admitted to the hospital solely because they are known or suspected to be malignant hyperthermia-susceptible (MHS). To determine whether their hospitalization is necessary, the medical charts of 303 children labeled MHS who had undergone surgery with anesthesia free of malignant hyperthermia-triggering agents on 431 occasions between 1981 and 1990 were reviewed. Eighteen of these patients (25 cases) who were subsequently identified as biopsy-negative were excluded from the study. We recorded the reason for the MHS label and the perioperative management and outcome of the cases. Fifty-eight percent of procedures were followed by hospital admission solely because of the patient's MHS label. None of the 25 children (33 cases) with biopsy-proven malignant hyperthermia developed intraoperative or postoperative pyrexia. Ten children suspected to be MHS developed pyrexia greater than 38.5 degrees C. These episodes were not considered to be malignant hyperthermia and were not treated with dantrolene. None of the remaining 275 patients exhibited any features of malignant hyperthermia, although one had an adverse reaction to radiologic contrast medium. On the basis of our retrospective analysis, postoperative admission to the hospital solely on the basis of the MHS label is not warranted.

Determination of bupivacaine in plasma by high-performance liquid chromatography. Levels after scalp infiltration in children.

The local anaesthetic bupivacaine could be very useful for analgesia in pediatric neurosurgery. Since systemic toxic reactions to bupivacaine are correlated with high plasma levels it was important, as an adjunct to clinical evaluation, to measure plasma bupivacaine. This report describes a high-performance liquid chromatography (HPLC) method for the quantitation of plasma bupivacaine. Sample preparation involves extraction into ether followed by back-extraction into HCl. After evaporation, the acid extract is redissolved and separated by reversed-phase chromatography. The assay is linear to 5 mg bupivacaine/L and shows excellent recovery and precision. With samples from children undergoing brain surgery following scalp infiltration with either 0.125% or 0.25% bupivacaine, plasma levels peak within 10 min, then fall rapidly to a plateau by 30 min. This plateau is maintained for at least 120 min. In no case did we find supposed toxic levels of bupivacaine.

Scalp infiltration with bupivacaine in pediatric brain surgery.

To evaluate whether local anesthetic scalp infiltration blunts hemodynamic responses to craniotomy in anesthetized children (age, 2-18 yr), two concentrations of bupivacaine (0.125% and 0.25%) with vasoconstrictor (epinephrine 1:400,000) were compared with control data when a solution of vasoconstrictor alone was injected. Arterial plasma levels of bupivacaine were measured by high-pressure liquid chromatography. Statistically significant increases in mean arterial pressure and heart rate above baseline measurements occurred in the control group during the period between scalp incision and dural reflection (P less than 0.05). Both concentrations of bupivacaine prevented these increases. Mean arterial pressure and heart rate during scalp incision and scalp reflection were significantly higher in the control group than in both bupivacaine groups (P less than 0.05). Peak bupivacaine plasma levels (mean +/- SD) occurred either 5 or 10 min after infiltration and were significantly higher in the 0.25% group (0.48 +/- 0.31 microgram/mL) than the 0.125% group (0.14 +/- 0.13 microgram/mL) (P less than 0.05). These results suggest that bupivacaine infiltration blocks the hemodynamic response to craniotomy. A concentration of 0.125% bupivacaine with 1:400,000 epinephrine is as effective as 0.25% bupivacaine with 1:400,000 epinephrine at reducing the hemodynamic response to craniotomy. Because the lower concentration of bupivacaine produces lower blood levels, we recommend 0.125% bupivacaine with 1:400,000 epinephrine as a useful, safe adjunct to general anesthesia in children undergoing craniotomy.

Development of receptors for dopamine and noradrenaline in rat brain.

In order to examine the receptor basis for the development of spontaneous locomotion and for the effects of clonidine in the infant rat, we measured the densities of alpha 1-adrenoceptors, alpha 2-adrenoceptors and D2-dopamine receptors in various brain regions of the developing infant Wistar rat. The mesolimbic D2-dopamine receptors paralleled the rise in spontaneous locomotion of the infant rat. No alpha 1-adrenoceptors were detectable at birth in any of the four regions examined (mesolimbic, hippocampus, frontal cortex, and hypothalamus), thus providing no basis for the locomotor-stimulating action of clonidine in the first week of life. Mesolimbic alpha 2-adrenoceptors matured between 21 and 28 days (at which time clonidine yields its usual sedating action).

The effect of calcium oncardiac phosphorylase activation, contractile force and cyclic AMP in euthyroid and hyperthyroid rat hearts.

Calcium chloride injected into isolated perfused rat hearts produced a positive inotropic effect and increased the levels of phosphorylase a (EC 2.4.1.1). The increase in enzyme activity lagged behind the inotropic effect. Pretreatment of animals with thyroid hormone enhanced the ability of noradrenaline to activate phosphorylase but did not affect the inotropic or phosphorylase activating effect of calcium. Thyroid hormone pretreatment did enhance the chronotropic effect of calcium. Calcium did not affect the cardiac levels of cyclic AMP. It is concluded that calcium can activate phosphorylase by a mechanism other than cyclic AMP and that the enhancement of adrenergic amine-induced phosphorylase activation by thyroid hormone is not a calcium mediated event.