[The child with minor trauma. Does observation of fasting times reduce the risk of aspiration?]

According to a literature search, it seems most unlikely based on patho-physiological requirements and physiological aspects that traumatized children benefit from preoperative waiting times aimed at achieving a 6-h fast. Irrespective of fasting, traumatized children are at risk of requiring aspiration. Many generally recommended measures for the avoidance of aspiration are neither reasonable nor effective in traumatized children. The physical and psychological benefits that can be derived from shorter preoperative waiting times can more than over-ride the organizational difficulties caused by waiting longer.

Nasal midazolam in children, plasma concentrations and the effect on respiration

Twenty ASA 1 children, one to six years old, weighing 10-20 kg, scheduled for a combination of general and caudal anaesthesia received at random midazolam 0.2, 0.4, or 0.6 mg.kg-1 or NaCl 0.9% (control group) intranasally. Drug or NaCl 0.9% were administered in one nostril, after inhalation induction of anaesthesia, intubation without relaxant and caudal anaesthesia. Spontaneous respiration was via a circle system and fresh gas flow of 6 l.min-1 (N2O/O2 = 2:1), PEEP 5 cm H2O, endtidal halothane 0.4%. Immediately before and 2, 5, 8, 12, 16, 20, 30, 60 and 120 min after application of the drug 2.5 ml blood was sampled for plasma levels of midazolam. Endtidal CO2, respiratory rate, and oxygen saturation were recorded as long as the children were intubated. Endtidal CO2 and respiratory rate showed no statistical difference between the groups at any time, however, in the group receiving 0.6 mg.kg-1, endtidal CO2 increased significantly from 5.3 kPa (41 mm Hg) at the start to 5.9 kPa (45.5 mm Hg) after 30 min. Plasma levels of midazolam were detected 2 min after application in 10 of 15 patients. Median peak levels were found between 12 and 16 min. Medians of peak plasma levels showed no statistical difference between the three groups (0.2 mg.kg-1:111 ng.ml-1, 0.4 mg.kg-1:136 ng.ml-1, 0.6 mg.kg-1:277 ng.ml-1). After 30, 60 and 120 min medians of midazolam plasma concentration were significantly higher in the group 0.6 mg.kg-1.

[Preparation of children for anesthesia]

Children are not born as little adults, and more important than the difference in size are psychic, physiological and pharmacological aspects. Intense preparatory information and training will be necessary to avoid or reduce psychic trauma due to hospitalization, narcosis and operation. Basic laboratory findings as hemoglobin, hematocrit, urinalysis and blood-group are supplemented by special examinations if indicated. Preoperative fasting shouldn't be prolonged respecting poor metabolic and fluid reserves. Adequate oral or rectal premedication is as important as careful induction.

[The prevention of postoperative vomiting following strabismus surgery in children]

Children recovering from anaesthesia for strabismus surgery are particularly prone to nausea and vomiting as a result of intraoperative vagus irritation. Besides being disturbing to the patient, vomiting can be dangerous during emergence from anesthesia and can result in delayed discharge. Droperidol is a powerful antiemetic drug that has been shown to reduce the incidence and severity of postoperative nausea and vomiting in pediatric strabismus patients, although the best timing for administration is not clear. MATERIAL AND METHODS. We compared three randomized groups totalling 61 patients. Droperidol 0.075 mg/kg i.v. was given either at induction of anesthesia after intubation (n = 20) or during the last muscle suture (n = 21). The third group received no antiemetic treatment. The patients' ages ranged from 3 to 14 years (mean 5.9 +/- 2.84 years). There was no difference in age or sex between the three groups. Anesthesia was standardized with rectal midazolam premedication, atropine, thiopental, succinylcholine, O2/N2O = 1:2, enflurane, intubation, and a gastric tube. RESULTS. Nausea, retching, or vomiting occurred in 2/20 children (10%) given droperidol preoperatively, 4/21 children (19%) with droperidol during the operation, and 9/20 children (45%) with no antiemetic treatment. The difference between groups I and III was significant (p less than 0.05). Comparison of groups II and III and groups I and II showed no statistical significance. Operation time was similar in each group and there was no delay in time of extubation. In each group 1 case of hypotension occurred. No child showed extrapyramidal symptoms. The lower incidence of vomiting in all study groups compared to the literature is thought to be due to three factors: (1) emptying the stomach at the end of the operation by a gastric tube, which is removed before extubation; (2) avoidance of opioids; (3) surgical procedure being done by a very experienced surgeon in 57/61 children (12 vomiting versus 45 not vomiting) in contrast to 3/4 children vomiting postoperatively after surgery by a less experienced surgeon. CONCLUSIONS. We recommend preoperative droperidol 75 micrograms/kg i.v. as the best prophylaxis of postoperative emesis without severe side effects in pediatric strabismus surgery.

[Famotidine dosage in children. The effect of different doses on the pH and volume of the gastric juice]

Children undergoing general anesthesia are at increased risk of severe aspiration pneumonitis. Cimetidine and ranitidine, specific histamine (H2-receptor) antagonists, when given 1-3 h preoperatively markedly reduce the acidity and volume of gastric content. A newer compound, famotidine, is a more specific antagonist with no inhibitory effect on the drug metabolizing microsomal enzyme systems of the liver (cytochrome P-450), in contrast to cimetidine. An additional clinical advantage is a possible longer duration of action. In order to evaluate these potential advantages we studied the effects of preanesthetic oral famotidine on gastric fluid pH and volume in 4 groups in a random manner. METHODS. With parental consent, 107 infants and children (ASA I status, 4 months to 14 years old, NPO for at least 6 h) received either no famotidine (n = 29) or 0.15 mg/kg (n = 27), 0.3 mg/kg (n = 25) or 0.6 mg/kg (n = 26) famotidine at 7.00 a.m. Following induction by mask with nitrous oxide/oxygen (N2O/O2) and enflurane (E) or i.v. thiopental, intubation was performed in all patients. Anesthesia was maintained with N2O/O2 and E. A orogastric double-lumen tube was passed into the stomach, and the gastric content was aspirated in a uniform manner. Gastric volume was recorded and pH values were measured with pH paper. RESULTS. In the control group, 28 of 29 patients (97%) had a pH less than 2.5, 18/29 (62%) had a gastric volume greater than 0.4 ml/kg and 17/29 (59%) had a pH less than 2.5 and gastric volume greater than 0.4 ml/kg, meaning an increased risk of pneumonitis if the child aspirates the gastric content. Famotidine administration was effective between 1.5 and 6 h after oral administration. Preoperative famotidine application produces pH values of gastric contents higher than 2.5 in all dosage groups (84%, 94%, 75%), and these differences were highly significant (P less than 0.001), whereas the gastric volume reduction with these doses was not significant. The incidence of pH less than 2.5 and volume of gastric contents exceeding 0.4 ml/kg did not vary with the different doses of famotidine. As there were no measurable differences in the effect of famotidine, we recommend that children at high risk of pulmonary aspiration receive 0.15 mg/kg famotidine orally at least 1.5 h but not later than 6 h before induction.

[Perioperative infusion therapy in children]

An incorrect fluid therapy can lead to serious complications considerably more rapidly in children, especially in newborns and infants, than in adults. The pediatric patient has a limited range of compensation for maintenance of fluid and electrolyte balance. Precise knowledge of the physiological age-dependent fluid balance, i.e. the large extracellular space, the developing renal function, the increased metabolism, the acid-base state, the electrolyte balance with the relatively higher sodium and chloride requirements must be the basis of an adequate fluid therapy. The basic fluid requirement (normal fluid and electrolyte requirement) varies with age and is influenced considerably by environmental conditions, body temperature and metabolism. For substitution of this basic fluid requirement one-third to one-half strength electrolyte solution in 5% dextrose is used, the amount depending on age. The perioperative fluid requirement, however, has to be calculated with due consideration for the characteristic changes in fluid and electrolyte balance during anaesthesia and surgery, the preoperative fasting period, drug effects of anesthetics, hormonal changes and ventilation; it is higher than the basic fluid requirement (infants 6-8 ml.kg-1.h-1, toddlers 4-6 ml.kg.h-1, schoolchildren 2-4 ml.kg-1.h-1). For intraoperative fluid therapy infusions with an increased sodium concentration (70-100 mmol/l) or Ringer's lactate (Na+ = 130 mmol/l) must be used. On no account must electrolyte-free solutions, e.g., 5-10% glucose, be used intraoperatively, as they can lead to water intoxication. The third-space requirements compensate for the additional losses by drainage, third-space deficits by evaporation and gastric and enteral secretions.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetic studies following intravenous and rectal administration of midazolam in children]

In children, rectal midazolam is being used increasingly for premedication, as this substance is reported to have a short half-life and rapid action. Above all it is the only known diazepam derivative with a good correlation of plasma concentration and clinical action despite its receptor binding capacity. As pharmacokinetic data in children are lacking and different dose regimens for rectal premedication exist, we studied plasma concentrations in 3 groups of children. METHODS. After obtaining informed parental consent we studied children aged 3-7 years (15-30 kg body weight) ASA I status scheduled for minor elective surgery. Group 1 (n = 6) received 0.1 mg/kg midazolam i.v. for induction of anesthesia. Group 2 (n = 10) was premedicated with 0.35 mg/kg midazolam, instilled just behind the anal sphincter; group 3 (n = 5) received 0.5 mg/kg midazolam rectally. Blood samples were drawn up to 120 min after application. The anesthesia technique consisted of N2O/O2, enflurane, intubation and the use of muscle relaxants, if necessary. Midazolam plasma levels were measured by HPLC. RESULTS. There were no differences with respect to age or body weight. Group 1: half-life in children was shorter than in adults, Vdss was smaller and clearance identical. Group 2: Rectal midazolam 0.35 mg/kg has a remarkably short onset of action with peak plasma concentrations (71 ng/ml) in the range of sedative levels in adults occurring in 7.5 min. After 2 h they reached levels of 30 ng/ml. Group 3 patients had peak levels of midazolam of 246 ng/ml after 12.5 min, falling to an average concentration of 120 ng/ml after 2 h. The bioavailability of rectal midazolam, comparing the area under the median curves, is 4.7% in group 2 and 16.1% in group 3.

CONCLUSIONS

The pharmacokinetics of midazolam in our patients showed a shorter half-life, probably due to the higher hepatic clearance based on the high CI in children, as midazolam is known to have a first-pass effect of 30-70%. The increased metabolic transformation and the smaller amount of fatty tissue accounts for the smaller Vdss in children compared to adults. Rectal midazolam has a remarkably short onset and especially in a dose of 0.5 mg/kg prolonged action due to ongoing resorption from the rectum as demonstrated by the clinically relevant plasma concentrations. This fact must be taken into consideration in the overall anesthesia management.(ABSTRACT TRUNCATED AT 400 WORDS)

[Observations on preoperative restriction of fluid intake in infants (author's transl)]

The problem was investigated whether a reduction to 4 hours of the interval between fluid intake and start of anaesthesia carried increased anaesthetic risks. In 23 infants the residual volume of gastric fluid, its pH and glucose concentration were determined 6 hours after normal feeding and 2 hours and 4 hours after administration of a 10 per cent glucose solution in quantities equivalent to a normal bottle feed. The results showed almost complete gastric emptying 4 hours after administration of a 10 per cent glucose solution.