Inhalational anaesthetic agents are frequently used in paediatric daily practice . However, a high flow of fresh gas is preferred in a semi-closed system in this type of anaesthesia. Although low flow anaesthesia techniques with new inhalation anaesthetics like desflurane and sevoflurane were studied in adult patients previously, there are a few studies regarding the use of low flow anaesthesia with these agents in children [2-4].
Our aim in organizing this study was to assess the effects of low flow anaesthesia with desflurane and sevoflurane on intraoperative haemodynamics, hepatic and renal functions, recovery period, and on postoperative nausea and vomiting.
The study was approved by the Local Ethics Committee of the Medical School of Gaziantep University, Turkey. Eighty ASA I-II children, aged between 5 and 15 yr were included in the study after obtaining informed consent from the parents. This prospective, randomized, unblinded study was conducted on consecutive children who underwent elective surgery. A computer-generated table of random numbers was used in the randomization. There were no patients with cardiac, respiratory, endocrine, metabolic, hepatic, renal or central nervous system diseases.
The patients were premedicated with oral 0.5 mg kg−1 midazolam 30 min before surgery. In the operating theatre, an intravenous (i.v.) cannula was placed in one of the antecubital veins, and 5% dextrose plus 0.9% NaCl (ratio 1 to 3) was infused at 5 mL kg−1 h−1. Electrocardiogram, heart rate (HR), non-invasive blood pressure (BP) and peripheral arterial oxygen saturation (SPO2) were recorded. In all patients, Drager Cato M 33010 (Lubeck, Germany) anaesthesia equipment and Dräger PM 8040 (Lubeck, Germany) monitor were used. The anaesthetic machine (Drager Cato M 33010) is equipped with compact breathing system and a piston pump ventilator featuring fresh gas flow compensation by fresh gas decoupling. The breathing system is characterized by very high gas tightness which is checked automatically when switching on the machine. The ventilator can be used even in the smallest infants as the lowest tidal volume precisely delivered is only 20 mL. The machine is specially suitable for use in low and minimal flow anaesthesia .
Inspired and expired oxygen fraction, nitrous oxide and end-tidal carbon dioxide values were continuously monitored. Preoxygenation was performed for 5 min in all patients before induction. For induction, i.v. propofol (2 mg kg−1) and fentanyl (1 μg kg−1) was given initially and muscle relaxation achieved by i.v. atracurium (0.5 mg kg−1) after loss of eyelash reflex. Orotracheal intubation was performed using a cuffed tube and mechanical ventilation was maintained. End-tidal carbon dioxide, tidal volume and respiratory rate were adjusted to 30-40 mmHg, 8-10 mL kg−1, 14-22 min−1, respectively.
Systolic, diastolic and mean arterial pressures, HR, SPO2, and end-tidal gas values were measured before induction and during surgery. After induction, the values were also recorded every 5 min for the first 30 min of the operation, every 15 min until the 90th-minute of the operation and every half an hour until completion of the operation. Meanwhile, volatile anaesthesic concentrations were also recorded in the samples obtained by a side-stream method and using infrared analysis technique. Patients were randomly divided into two groups as follows:
Desflurane group (n = 40). At the beginning of anaesthesia, 4 L min−1 N2O, 2 L min−1 O2 and 4-6% desflurane vaporizer combination was given for 10 min. Then, 50% O2 + 50% N2O + 4-6% desflurane was given as 1 minimal alveolar concentration (MAC) total fresh gas flow at 1L min−1 using a Devapor vaporizer (Lubeck, Germany).
Sevoflurane group (n = 40). At the beginning of anaesthesia, 4 L min−1 N2O, 2 L min−1 O2 and 2-2.5% sevoflurane combination was given for 10 min. Then, 50% O2 + 50% N2O + 3% sevoflurane was given as 1.5 MAC total fresh gas flow at 1 L min−1 using a Drager 19.3 vaporizer (Lubeck, Germany).
When a 30% decrease occurred in O2 concentration, the O2 flow could be increased by 10% of the total flow and N2O could be decreased by the same rate. When HR and mean arterial pressure rose by more than 20% of the baseline, the anaesthetic gas concentration was increased by 25%. If this did not prove to be adequate, i.v. 1 μg kg−1 fentanyl could be given. When HR and mean arterial pressure were less than baseline by 20%, anaesthetic gas concentration were decreased by 25%. If needed, 5-10 mg i.v. ephedrine could be given.
Ten minutes before completion of the surgery, the expiration valve was opened and fresh gas flow rate was increased to 6 L min−1. The vaporizer and N2O were turned off when skin was sutured and ventilation was performed manually with 100% O2. The muscle relaxation was reversed with 0.04 mg kg−1 neostigmine and 0.02 mg kg−1 atropine.
Anaesthesia time was accepted as the duration between administration of i.v. induction drug and closure of the skin incision. Anaesthesia time and duration of surgery were noted in both groups. In order to evaluate hepatic and renal functions, 4 mL blood was drawn preoperatively and 24 h after the operation. Within half an hour, the blood samples were centrifuged at 3000 rpm for 10 min, and serum was obtained. Blood urea nitrogen, creatinine, alanine transaminase, aspartate transaminase, alkaline phosphatase and bilirubin levels were measured.
After discontinuing the inhalation anaesthetic, the patient was instructed to open his/her eyes every 30 s and this was termed the eye opening time. The time until extubation after cessation of the inhalation anaesthesia and the resumption of spontaneous respiration was measured. The time to obey the instruction ‘protrude your tongue’ after discontinuing the inhalational agent was also recorded. Postanaesthetic recovery score was evaluated at the 10th and 30th minutes after extubation according to a modified Aldrete scoring system . Patients who had a score of <8 were taken into postoperative recovery room and followed up until full recovery.
All patients in both groups were followed up for 24 h after the operation in order to record nausea and vomiting on the following scale: 0, no nausea or vomiting; 1, nausea but no vomiting; 2, vomiting only once; 3, vomiting more than one.
SPSS for windows version 10.1 was used for statistical analysis. Results were presented as mean ± SD. t-test was used to compare haemodynamic parameters. Paired t-test was used to compare renal and hepatic parameters. Nausea and vomiting rates were compared using χ2-test. A P-value of <0.05 was considered significant.
Patient characteristics for both groups are given in Table 1. Preoperative and postoperative BPs were significantly different within each group (P < 0.05). However, this difference was not clinically significant as there was no need to give further medication. There was a decrease in BP in the sevoflurane group compared to the desflurane group (P > 0.05). In both groups, the haemodynamic parameters did not exceed the basal level by ±20%. There was no significant difference between two groups regarding HR or BP values (P > 0.05).
Renal function test results are shown in Table 2. Although there was a slight increase in the postoperative values compared with preoperative values, this increase was not statistically significant both within and between the groups. Hepatic function test results are shown in Table 2. In both groups alanine and aspartate transaminases and bilirubin increased after the operation but they were not statistically significant both within and between the groups. Early period recovery data (eye opening time, extubation time, time to obey commands) were shorter in the desflurane group compared to the sevoflurane group (Fig. 1) (P < 0.05). None of the patients had a recovery score <8 at the 10th minute, and all patients had a score of 10 at the 30th minute. There was no significant difference between recovery scores (Table 3). There was no significant difference between the groups regarding the rate of nausea and vomiting (Fig. 2).
Sevoflurane and desflurane are frequently used for paediatric anaesthesia [1,6,7]. They are metabolized to a low extent, and reported to be safe haemodynamically in low flow anaesthesia in adult patients . Sponheim and colleagues  used sevoflurane and desflurane in children, and reported that mean arterial pressure had been decreased significantly after the use of these agents. However, we could not find any report in the literature regarding the haemodynamic effects of sevoflurane or desflurane with low flow anaesthesia in children. Contradictory to the report of Sponheim and colleagues , which is not a low flow anaesthesia study, we observed insignificant decreases in arterial pressures in both groups. This difference may be due to the lower flow rate that was used in our study.
Sevoflurane and desflurane are reported to be neither hepatotoxic nor nephrotoxic in a study performed in adult patients with high flow anaesthesia . Similarly, Frink and colleagues  applied sevoflurane (2L min−1) anaesthesia in 19 infants for 4 h, and did not encounter any hepatic or renal toxicity. In our study, we observed a slight but statistically insignificant increase in urea and creatinine levels after the operation in both desflurane and sevoflurane groups. This result also suggests that low flow desflurane and sevoflurane anaesthesia does not have a nephrotoxic effect. Nishiyama and colleagues  showed in adult patients that isoflurane caused an increase in transaminase values 7 days after the operation while sevoflurane did not have a similar effect. Wissing and Kuhn  showed that high flow desflurane anaesthesia caused a significant decrease in alkaline phosphatase after the operation whereas transaminases did not change.
In our study, there was a slight decrease in transaminases and an increase in alkaline phosphatase and total bilirubin after the operation although there was no significant difference between the groups. This also suggests that low flow desflurane and sevoflurane anaesthesia does not impact on liver function.
In children, recovery time after high flow desflurane anaesthesia is shorter compared with sevoflurane and halothane anaesthesia . In a series of 100 children, Cohen and colleagues  found that extubation time was shorter with desflurane anaesthesia compared with sevoflurane anaesthesia (6.5 vs. 9.3 min, respectively). In our study, eye opening time, extubation time and time to obey commands were shorter in the desflurane group compared with the sevoflurane group. Kuhn and colleagues  reported that high flow desflurane anaesthesia caused nausea and vomiting in 37% and 32% of children, respectively. Low nausea and vomiting rate after desflurane anaesthesia is an advantage for early discharge. In our study, postoperative nausea and vomiting rates were not significantly different between desflurane and sevoflurane groups, and were 37% and 35%, respectively.
In conclusion, low flow desflurane and sevoflurane anaesthesia does not impact on haemodynamic parameters, hepatic and renal functions in children. We conclude that both agents can be used in low flow paediatric anaesthesia routinely. Desflurane anaesthesia may be preferred when early recovery from anaesthesia is warranted.
The authors wish to thank Dr Yildirim A. Beyazit, for invaluable support and his assistance with this article.
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