|Year : 2015 | Volume
| Issue : 4 | Page : 535-538
Effect of sevoflurane versus isoflurane on middle ear pressure during tonsillectomy operation
Samia R El Azab MBBCh, MSc, MD, PhD 1, Zeinab Bayomi1, Soad S.A. El Gaby1, Fatma M Abdelgaber2
1 Department of Anesthesiology and Intensive Care, Faculty of Medicine, Al Azhar University for Girls, Cairo, Egypt
2 Department of Otolaryngology, Faculty of Medicine, Al Azhar University for Girls, Cairo, Egypt
|Date of Submission||16-May-2014|
|Date of Acceptance||24-Aug-2014|
|Date of Web Publication||29-Dec-2015|
Samia R El Azab
Department of Anesthesiology and Intensive Care, Faculty of Medicine, Al Azhar University for Girls, Cairo
Source of Support: None, Conflict of Interest: None
Increase in middle ear pressure (MEP) (mmH 2 O) is an undesirable condition because of its potential complications. The aim of this randomized study was to compare the effects of isoflurane and sevoflurane on MEP.
Patients and methods
Patients in American Society of Anesthesiologists (ASA) group I-II between 6 and 14 years of age undergoing tonsillectomy operation were randomized into two groups. Group 1 received isoflurane and group 2 received sevoflurane for maintenance of anesthesia after induction with thiopental and suxamethonium in both groups. MEPs were measured and recorded 1 day before the operation (T0), with the patient lying supine on the operating table (T1), after the induction of anesthesia and endotracheal intubation (T2), and soon after withdrawal of anesthesia (T3). Finally, MEP values were compared intragroup with the baseline value (T0) and between groups.
In comparison with the baseline value in T0, MEP was significantly increased in T1, T2, and T3 in the two groups. There were no differences between groups at all times, but at the end of anesthesia at T3, the increase in MEP was significantly lower in group 1 (isoflurane group) than in group 2 (sevoflurane groups) (103 ± 68 vs. 138 ± 99, P < 0.01 in the right ear and 112 ± 82 vs. 141 ± 101, P < 0.01 in the left ear).
There was an increase in MEP after anesthesia with both the inhalational anesthetics, but the increase in MEP was significantly lower during isoflurane anesthesia, which makes it more suitable during middle ear surgery.
Keywords: inhalation anesthetics, isoflurane, middle ear pressure, sevoflurane
|How to cite this article:|
El Azab SR, Bayomi Z, El Gaby SS, Abdelgaber FM. Effect of sevoflurane versus isoflurane on middle ear pressure during tonsillectomy operation. Ain-Shams J Anaesthesiol 2015;8:535-8
|How to cite this URL:|
El Azab SR, Bayomi Z, El Gaby SS, Abdelgaber FM. Effect of sevoflurane versus isoflurane on middle ear pressure during tonsillectomy operation. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2019 Sep 22];8:535-8. Available from: http://www.asja.eg.net/text.asp?2015/8/4/535/172729
| Introduction|| |
Inhalant anesthetic agents may enter the middle ear (ME) space during the administration of anesthesia and can affect ME status by increasing middle ear pressure (MEP) to a larger extent than intravenous anesthetics  .
The volatile anesthetic agents pass into the ME by insufflations through the Eustachian tube and/or by diffusion from the circulation and cause changes in the MEP  . Increase in MEP may cause complications such as ear pain, transient or permanent hearing loss, hemotympanium, disarticulation of stapes, tympanic membrane rupture, serous otitis media, displacement of tympanic membrane graft, and failure of ossicular chain repair ,, .
It has been reported that an increase in MEP because of inhalant anesthesia may cause effusion to be pushed out of the ME by the Eustachian tube  . This may cause an ear, preoperatively diagnosed to have otitis media with effusion, to be found dry during surgery, leading to a wrong decision of insertion of a tempanostomy tube  .
Surgery under general anesthesia may lead to negative MEP in some patients, and otitis media with effusion was reported in 3.3% of cases. Gas dynamics in the ME cavity induced by inhalation anesthesia and transient blockage of the Eustachian tube induced by surgery are considered to be involved in the development of this phenomenon  .
Therefore, the anesthesiologist should use an anesthetic agent that would result in minimal intratympanic pressure. The aim of this work was to compare the effects of sevoflurane versus isoflurane on MEP to determine which of these options will be more appropriate in ME operations.
| Patients and methods|| |
This study was carried out at the Ear, Nose and Throat, Audiology and Anesthesiology departments in Al Azhar University Hospital. After approval from the hospital ethics committee and obtaining signed informed consent from parents or guardians, the study was carried out on 30 children between 6 and 12 years old, scheduled for tonsillectomy with previously known normal ME function. Physical and ENT examinations were carried out on the preoperative day and patients were excluded from the study if they had acute or chronic otitis media, a history of previous ME surgery, otoscopic evidence of a perforated tympanic membrane, and any ME pathology such as effusion, nasal septum deviation, flat tympanogram, or absence of acoustic reflexes. On the morning of the operation, patients were allocated randomly to receive either isoflurane (group 1) or sevoflurane (group 2).
Patients were fasting for 6-8 h before the operation and premedicated with 0.1 mg/kg midazolam intramuscularly 30 min before operation. In the operating room, an intravenous line was inserted with a 20-22 G cannula and infusion was initiated with 5 ml/kg of dextrose 5%. Continuous monitoring of heart rate was performed with ECG, and noninvasive monitoring of systolic, diastolic, mean arterial pressures, and oxygen saturation.
Anesthesia induction was standardized in both groups as follows: 2-3 min of preoxygenation, followed by intravenous 5 mg/kg thiopental (Thiopental, Sandoz, Egypt), 1.0 mg/kg suxamethonium, and 1.0 µg/kg fentanyl repeated after 30 min. Nasal intubation was performed to facilitate surgical exposure during tonsillectomy. Maintenance of anesthesia was achieved with isoflurane 1.5-2.5% (in group 1) or sevoflurane 2-4% (in group 2) in a 50% O 2 /air mixture. Spontaneous respiration was allowed after cessation of the effect of suxamethonium.
At the end of the operation after bleeding control, oral suction was performed, inhalation anesthetics were stopped, and 100% O 2 was inhaled; then, patient was extubated and transferred to the recovery room. The time of anesthesia and surgery were recorded.
The tonsillectomy was performed by the dissection procedure, where the patient lies supine with the neck extended by a sandbag placed under the shoulders. The mouth was opened using a Boyle-Davis mouth gag. The tonsil was grasped by a tonsil holding forceps and pulled medially. The anterior pillar was then incised, and by sharp dissection, the plane of cleavage was obtained. The upper pole of the tonsil was held by an artery forceps and was cut by a scissor. Then, the tonsil was removed by blunt dissection till its lower pole, which was held by clamp forceps and ligated, to be followed by good hemostasis.
Tympanometric functions were assessed by an audiologist using Middle Ear Analyzer Model GSI (Philadelphia, PA, USA) to check the standard immitance screening of the ME of patients. Tympanometric tests were performed using the Jerger and Jerger (1972) classification; type A curve on normal MEP ranges between -100 and +500 daPa. Four measurements were performed and recorded as follows: at time 0, 1 day before the operation while the patient was in the sitting position (T0); time 1, preoperative when the patient lay supine on the operating table (T1); time 2, after the induction of anesthesia and endotracheal intubation (T2); and time 3, soon after withdrawal of anesthesia (T3).
Sample size was calculated using a 'Nomogram for calculating sample size or power'; we chose a power of 90% and a standardized difference of 1.2 and simply drew a line that passed by the number of 30 at a P-value of 0.05. Calculations were performed on a personal computer using SPSS (version 16.0; SPSS Inc., Chicago, Illinois, USA). The groups were tested for differences using Student's t-test for continuous variables and Fisher's exact test for categorical variables. The Mann-Whitney U-test was used to compare MEP between the two groups at each time point (intergroup) and Wilcoxon tests (intragroup). In all cases, a P-value less than 0.05 was considered to indicate statistical significance.
| Results|| |
The intraoperative and postoperative periods were uneventful in both groups. Demographic data, and time of anesthesia and surgery were comparable in both groups [Table 1]. Compared with the baseline measurement at T0, the MEP continually increased significantly after that at all time points of measurements in the right and left ears in both groups [Figure 1] and [Figure 2]. There were no differences between the groups at any of the time points, but at the end of anesthesia at T3, the increase in MEP was significantly lower in group 1 (isoflurane group) than in group 2 (sevoflurane group) [Table 2].
|Figure 1: Increase in right middle ear pressure in both groups. Middle ear pressure is shown in mmH2O. *Significant difference|
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|Figure 2: Increase in left middle ear pressure in both groups. Middle ear pressure is shown in mmH2O. *Significant difference|
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| Discussion|| |
MEP variations because of inhalant anesthesia have been reported by several investigators. It has been reported before that volatile anesthetic agents pass into the ME by insufflations through the Eustachian tube and/or by diffusion from the circulation and cause changes in the MEP  . The change in the MEP during surgery may cause rupture of the tympanic membrane, displacement of a tympanic membrane graft, hemotympanum, temporary or permanent hearing loss, and failure in ossicular chain repair  . Previous investigations have mostly been performed with nitrous oxide, halothane, sevoflurane, and desflurane in comparison with total intravenous anesthetics with propofol  . Volatile anesthetic agents are frequently used in general anesthesia practices without complications. Inhalation anesthetics are less expensive, simpler to use, and offer comparable intraoperative conditions to intravenous anesthesia techniques  .
In this study, we observed an increase in MEP in both patient groups starting from T1, when the patients lay on the operation table before induction of anesthesia, which could be attributed to the alteration in the aerated volume in the ME caused by filling of blood vessels within the ME cleft because of gravity when the patient lies in the supine position. This result has been reported previously by Cinamon et al.  , who reported an instant and significant increase in pressure in all ears once the position was changed from upright to recumbent.
In T2, after induction of anesthesia and laryngeal intubation, MEP continued to increase, without a difference between groups. This may have been because of manipulation of the laryngoscope in the airway and insertion of the endotracheal tube into the trachea. When a laryngoscope is placed along the airway, there is an impact on the tissues around the nasopharyngeal area. This pressure of the laryngoscope may result with auditory tube opening and in turn this will increase MEP. ET increases the pressure of the mucosal veins because of venous congestion. In addition, endotracheal intubation leads to marked changes in cardiovascular and hemodynamic status because of tissue irritation in the supraglottic region and the trachea  .
Also, procedures in the airway generate hypertension and tachycardia because of the response of the cardioaccelerator nerves and sympathetic ganglia , . As a result of all the above, an increase in venous pressure occurs in the ME mucosa, and consequently, there will be an increase in MEP.
This is why the MEP was increased markedly at T3, at the end of anesthesia, but this time, the increase in MEP was significantly higher in the patients in group 2, who received sevoflurane for maintenance of anesthesia. The increase in MEP levels with sevoflurane is probably because of the lower solubility in comparison with isoflurane. Laster et al.  reported a high rate of diffusion of inhaled anesthetics in the abdominal and thoracic viscera from swine. They showed that the least soluble agent was desflurane, followed by nitrous oxide, sevoflurane, and isoflurane and the most soluble agent was halothane.
The lower increase in MEP in the isoflurane group than the sevoflurane group in our patients is considered be related to the higher blood/gas partition coefficient of this anesthetic gas (1.4), which consequently decreased its transition into air-filled body spaces. The high solubility of anesthesia gases may not enable influx in the ME space, thus not resulting in a significant increase in MEP.
| Conclusion|| |
The results from this study have shown that isoflurane has a lower effect compared with sevoflurane on MEP, which makes it more suitable during surgery to avoid the occurrence of ME complications post operatively. Further, our results support the avoidance of inhalational anesthetics and usage of total intravenous anesthesia during ME surgery, but if indispensable, isoflurane may be a better choice than sevoflurane.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2]
[Table 1], [Table 2]