Sevoflurane for ENT-surgery in children. A comparison with halothane.

Sevoflurane, a new volatile anesthetic agent, is of great potential interest in pediatric anesthesia. Its use for ENT surgery in children was compared with halothane in this study. Altogether 40 children participated in the investigation. In 18 (median age 4.2 years), halothane was used. The remainder (median age 4.0 years) were anesthetized with sevoflurane. After rectal premedication with midazolam and atropine, anesthesia was induced by mask (the agent in O2/N2O, 40/60) using a Mapleson D system. The trachea was intubated without the use of muscle relaxants and the children were then allowed to breathe spontaneously at fresh gas flows set high enough to avoid rebreathing. Hemoglobine oxygen saturation (SpO2), inspired and expired gas concentrations, respiratory rate (RR), heart rate (HR), ECG and blood pressure were followed. Equianesthetic concentrations of the agents were used and induction characteristics were comparable between the two agents. RR and end-tidal CO2 tensions were similar in the two groups. HR and systolic blood pressures were, however, higher with sevoflurane. Cardiac arrhythmias were seen more frequently with halothane (61%) than with sevoflurane (5%). During emergence, postoperative nausea/vomiting was more frequent after halothane anesthesia. Initially, postoperative excitement occurred more often after sevoflurane, when paracetamol was given during anesthesia, which was reduced (P < 0.01) when paracetamol was given at the time for premedication. It is concluded that sevoflurane is an excellent induction agent, and maintains heart rate and systolic blood pressure better than when halothane is used. The incidence of cardiac arrhythmia is lower with sevoflurane than with halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon dioxide elimination in anaesthetized children.

Carbon dioxide elimination (VCO2) was measured in 186 anaesthetized, spontaneously breathing infants and children with body weights ranging from 2.8 to 26.5 kg. They all underwent minor paediatric surgical procedures. The influence on VCO2 of age, operation, premedication, caudal anaesthesia, and different volatile anaesthetic agents was investigated. The volume of exhaled gas, during three- to five-minute collection periods, was measured and the fraction of exhaled CO2 was determined by a CO2 meter. Under basal anaesthetic conditions, the average output before operation followed the equation: VCO2 (ml.min-1) = -1.25X + 13.0X2, in which X = lne (body weight, kg). Expressed on a weight basis, the youngest infants (weighing less than 5 kg) had the lowest VCO2. Higher values were measured up to a body weight of 10 kg above which a negative correlation occurred between VCO2 (ml.min-1.kg-1) and body weight. The use of premedication resulted in a more variable VCO2 during operations than when opioid premedication was not used. The combination of a general anaesthetic and caudal anaesthesia stabilized VCO2. Also, children anaesthetized with halothane had a higher VCO2 than those who were anaesthetized with enflurane or isoflurane (P less than 0.05). The variable VCO2 emphasizes the need for increased monitoring of VCO2 during routine anaesthesia and operation in infants and children.

Ventilatory CO2 response, respiratory drive and timing in children anaesthetized with halothane, enflurane or isoflurane.

Ventilatory CO2 response, respiratory drive and timing were investigated during anaesthesia prior to surgery in 24 spontaneously breathing cardiopulmonary healthy children. Anaesthesia was maintained with halothane, enflurane or isoflurane combined with oxygen-nitrous oxide (FIO2 0.5). The MAC values were 0.97 for halothane, 0.92 for enflurane and 0.92 for isoflurane. Pneumotachography and capnography were used and airway pressures were measured before and during breathing of 4% CO2 as well as during airway occlusion. Changes in minute ventilation were less with enflurane than with halothane and isoflurane in response to 4% CO2; however, tidal volumes were equally increased with all three agents. End-tidal CO2 tensions were significantly higher during enflurane than during both halothane and isoflurane anaesthesia, before as well as during CO2 stimulation. Respiratory rates were lower in children anaesthetized with enflurane and were unresponsive to CO2 when all three volatile agents were used. During CO2 challenge, mean inspiratory flow and maximal occlusion pressure were similarly increased in all groups.

Pulmonary ventilation and gas exchange in children anaesthetized with halothane, enflurane and isoflurane.

The effects of similar anaesthetic levels of halothane (1.3 MAC), enflurane (1.2 MAC) and isoflurane (1.1 MAC) on pulmonary ventilation and gas exchange were investigated in 24 children subjected to minor and intermediate paediatric surgical procedures. Eight children were anaesthetized with each agent, pneumotachography and capnography were used, and airway as well as oesophageal pressures were measured. Minute ventilation (VE) was lower with enflurane than with halothane (P less than 0.001) and isoflurane (ns). Tidal volumes were, however, similar and variations in VE were thus caused by lower respiratory rates with enflurane than with the two other agents. Alveolar ventilation (VABohr) and carbon dioxide elimination (VCO2) were smaller and end-tidal CO2 tension higher with enflurane. Ventilatory efficiency was, however, somewhat better with enflurane as indicated by lower VDBohr/VT (ns) and VE/VCO2 (P less than 0.05) ratios compared with the two other agents. The effects of all three agents on dynamic compliance were similar, while total pulmonary resistance was less with isoflurane than with halothane and enflurane. It is concluded that although minute ventilation was smaller with enflurane than with halothane and isoflurane, ventilatory efficiency was similar due to a smaller dead space ventilation as a result of the lower respiratory rates in children anaesthetized with enflurane.

Halothane, enflurane and isoflurane anaesthesia for adenoidectomy in children, using two different premedications.

In 48 children subjected to adenoidectomy, comparisons of airway problems, heart rates, cardiac arrhythmias, ventilation and stress hormone reactions were studied during halothane, enflurane and isoflurane anaesthesia. Sixteen children were anaesthetized with either of the three agents and eight patients in each group received diazepam 0.25 mg kg-1 and atropine 0.015 mg kg-1 rectally (DA) as premedication and the remainder diazepam 0.5 mg kg-1, morphine 0.15 mg kg-1 and scopolamine 0.01 mg kg-1 (DMS) rectally. All children were intubated and breathing spontaneously. Equianaesthetic inspired concentrations of halothane, enflurane and isoflurane were used. Airway problems were of the same magnitude during halothane and isoflurane anaesthesia but were less frequent with both agents compared with enflurane anaesthesia. DMS reduced the number of airway reactions in all groups. Respiratory rates were uninfluenced by anaesthesia, intubation and surgery during enflurane anaesthesia. Cardiac arrhythmias were less frequent with enflurane and isoflurane than with halothane. Plasma ACTH and cortisol were similar with all three agents. During induction of anaesthesia in the DA-premedicated halothane group, however, plasma catecholamines were higher than in the group which received DMS, in contrast to the findings during enflurane and isoflurane anaesthesia. The DMS premedication decreased the response of plasma ACTH, cortisol and plasma catecholamines to surgery.