Sevoflurane and propofol decrease intraocular pressure equally during non-ophthalmic surgery and recovery

S. Sator-Katzenschlager*,1,2, E. Deusch2, S. Dolezal1, A. Michalek-Sauberer1,2, R. Grubmüller1, G. Heinze3 and A. Wedrich4

1 Department of Anaesthesiology and General Intensive Care A, University of Vienna, Austria. 2 Department of Anaesthesiology and General Intensive Care B, University of Vienna, Austria. 3 Department of Medical Computer Science, University of Vienna, Austria. 4 Department of Ophthalmology and Optometrics, University of Vienna, Austria*Corresponding author: Department of Anaesthesiology and General Intensive Care, University of Vienna, Währinger Gürtel 1820, A-1090 Vienna, Austria

Accepted for publication: June 18, 2002


    Abstract
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
Background. To provide good control of intraocular pressure (IOP) during anaesthesia and surgery, we conducted a study comparing the effects on IOP during maintenance and recovery of sevoflurane vs propofol anaesthesia in 33 patients (ASA I–II) undergoing elective non- ophthalmic surgery.

Methods. Anaesthesia was induced with propofol 2 mg kg–1, fentanyl 2 µg kg–1 and vecuronium 0.1 mg kg–1. Patients were allocated randomly to receive either propofol 4–8 mg kg–1 h–1 (group P; n=16) or 1.5–2.5 vol% sevoflurane (group S; n=17) for maintenance of anaesthesia. Fentanyl 2–4 µg kg–1 was added if necessary. The lungs were ventilated with 50% air in oxygen. Blood pressure, heart rate, oxygen saturation and end-tidal carbon dioxide were measured before and throughout anaesthesia and in the recovery room. IOP was determined with applanation tonometry (Perkins) by one ophthalmologist blinded to the anaesthetic technique.

Results. There was a significant decrease in IOP after induction and during maintenance of anaesthesia in both groups. No significant differences in IOP between the two groups was found.

Conclusion. Sevoflurane maintains the IOP at an equally reduced level compared with propofol.

Br J Anaesth 2002; 89: 764–6

Keywords: anaesthetics i.v., propofol; anaesthetics volatile, sevoflurane; analgesics opioid, fentanyl; eye, intraocular pressure


    Introduction
 Top
 Abstract
 Introduction
 Methods and results
 Comment
 References
 
One goal of anaesthetic management during ophthalmic surgery is to provide good control of intraocular pressure (IOP). An increase in IOP may be catastrophic in patients with glaucoma or a penetrating open-eye injury. The IOP is determined by several factors, e.g. the rate of aqueous humour production, vitreous volume, choroidal blood volume, sclera rigidity, orbicularis oculi muscle tension and external pressure.1 The normal IOP is approximately 15 mm Hg, with a normal range of 10–20 mm Hg. Previous studies have examined the effects of anaesthetics and related drugs on IOP, although the mechanisms underlying effects on IOP remain largely unclear. Potent inhalation anaesthetics are used widely for maintenance of general anaesthesia because of their ease of administration and practicable intraoperative and recovery characteristics.2 Since the introduction of propofol, i.v. anaesthesia has also been used commonly. Sevoflurane and sevoflurane–remifentanil both decreased IOP from baseline values in rabbits, with no difference between groups.3 No reports have been published concerning the effects of sevoflurane on IOP in humans. Therefore we performed a randomized, prospective, single-blinded study to compare the effects of sevoflurane and propofol on intraocular pressure during maintenance and recovery of anaesthesia.


    Methods and results
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
After obtaining approval from the ethics committee of the hospital and written, informed consent, we studied 32 Caucasian patients aged 16–60 yr, ASA I or II, undergoing elective gynaecological or urological procedures. Exclusion criteria included a previous history of malignant hyperthermia, known allergies or adverse reaction to inhalation anaesthetics or propofol, patients with pre-existing ophthalmic diseases and those who had had laparoscopic surgical procedures. Patients were not envisaged to receive any catecholamine during the study.

Patients were allocated randomly to one of two groups: group P (n=16) and group S (n=17). All patients received orally midazolam 7.5 mg as premedication 1 h before surgery. Anaesthesia was induced with fentanyl 2 µg kg–1 and propofol 2 mg kg–1, and vecuronium 0.1 mg kg–1 was used to facilitate tracheal intubation. Ventilation was adjusted to maintain end-tidal carbon dioxide partial pressure (PE'CO2) at 4.3–4.6 kPa. Anaesthesia was maintained in group P with a continuous infusion of propofol 6–8 mg kg–1 h–1 and in group S with 1.5–2.5% sevoflurane. All patients were ventilated with a 50% mixture of air and oxygen. The inspired concentration of sevoflurane or infusion rate of propofol was titrated to maintain mean arterial blood pressure (MAP) and heart rate (HR) within 20% of baseline values. Mean MAP, electrocardiography, HR, arterial oxygen saturation (SaO2), end-tidal carbon dioxide (E'CO2 and nasopharyngeal temperature were measured continuously throughout anaesthesia. IOP values were obtained with a hand-held Perkins applanation tonometer.4 Patients were positioned supine for examination. One ophthalmologist, blinded to the anaesthetic technique, made all IOP measurements. IOP was measured before induction of anaesthesia (baseline), after induction but immediately before intubation, 1 min after intubation, 5 min after intubation and 2 min after skin incision, then every 15 min during maintenance of anaesthesia, completion of skin closure and after tracheal extubation.The inspired sevoflurane concentration was reduced or discontinued to achieve an end-tidal sevoflurane concentration of <0.1% by the completion of skin closure. The propofol infusion was also discontinued before completion of skin closure. In the recovery room, 30 min after the end of anaesthesia, a final measurement of IOP and haemodynamic variables and SaO2 was performed.

Baseline values are presented as mean (SD) and compared using t-tests. ANOVA for repeated measurements was used to assess differences from baseline values within groups and differences between groups at specific time-points. P<0.05 was considered statistically significant, using the Bonferroni–Holm method. Randomization of the patients was achieved using a computer-generated table.

All patients were evaluated and were comparable in age, body weight, sex and duration of operation. After induction of anaesthesia there was a significant decrease in IOP compared with baseline values in both groups (P<0.05). During maintenance of anaesthesia, significant IOP reductions over time were found in both groups (P<0.05). After extubation, the IOP increased in group P and S and returned nearly to baseline values. In the recovery room 30 min after the end of anaesthesia, IOP had returned to baseline values in group P and S. No significant differences in IOP were found between the groups. The baseline values of IOP were also similar between the groups (Fig. 1). Baseline values of haemodynamic (MAP and HR) and respiratory (E'CO2 and SaO2) variables were similar between the groups. MAP did not decrease significantly from baseline after induction and maintenance of anaesthesia, but HR decreased significantly from baseline during anaesthesia in groups P and S (both P<0.01). The respiratory variables were stable thoughout in both groups. No significant differences in MAP or HR and E'CO2 or SaO2were found between groups. No correlation was found between MAP, HR and IOP values.



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Fig 1 Intraocular pressure (IOP) in patients (n=33) undergoing non-ophthalmic surgery anaesthesia. Data are mean and SD. *P<=0.05 compared with baseline values.

 

    Comment
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
This study has demonstrated that during maintenance of anaesthesia significant IOP reductions occurred over time in both groups. During recovery from anaesthesia IOP returned to baseline values in both groups. No significant differences in IOP were found between the sevoflurane and propofol groups.

Apart from glaucoma, many factors influence intraocular pressure, such as genetics, age, refractive error and race.1 Central venous pressure and arterial carbon dioxide tension may influence IOP also. Any acute rise in intra-abdominal or intrathoracic pressure, which are observed frequently during extubation, might increase IOP. Particular attention must be paid to induction and emergence of anaesthesia, as both mechanical and pharmacological stressors have an amplifying effect on IOP. Most anaesthetic and hypnotic agents, including potent inhalation anaesthetics, barbiturates, opioids, neuroleptics and benzodiazepines, decrease IOP in proportion to the depth of anaesthesia. Jantzen emphasized the importance of anaesthetic drugs when general anaesthesia was planned for ophthalmic surgery.5

Anaesthesia for eye surgery patients must prevent an increase in IOP. Our results suggest that sevoflurane is a practical maintenance agent for adults, which decreased the IOP during anaesthesia at a constantly low level in patients undergoing non-ophthalmic surgery. We have shown previously a decrease in IOP after anaesthetic maintenance with propofol.6 The decrease in IOP after anaesthetic induction was sustained whether maintenance was provided by sevoflurane or propofol. In all groups, IOP increased towards baseline values after emergence from anaesthesia.

We conclude that maintenance of anaesthesia with sevoflurane sustained a low IOP at a level equivalent to that of propofol.


    References
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 Abstract
 Introduction
 Methods and results
 Comment
 References
 
1 Cunningham AJ, Barry P. Intraocular pressure physiology and implications for anaesthetic management. Can Anaesth Soc J 1986; 33: 195–208[ISI][Medline]

2 Thomson MF, Brock-Utne JG, Bean P, Welsh N, Downing JW. Anaesthesia and intraocular pressure: a comparison of total intravenous anaesthesia using etomidate with conventional inhalation anaesthesia. Anaesthesia 1982; 37: 758–61[ISI][Medline]

3 Artru AA, Momota Y. Trabecular outflow facility and formation rate of aqueous humor during anesthesia with sevoflurane nitrous oxide or sevoflurane–remifentanil in rabbits. Anesth Analg 1999; 88: 781–6[Abstract/Free Full Text]

4 Dunn R, Brubaker F. Perkins applanation tonometer, clinical and laboratory evaluation. Arch Ophthalmol 1973; 89: 149–51[ISI][Medline]

5 Jantzen JPAH. Anaesthesia and intraocular pressure. Anaesthesist 1988; 37: 458–69[ISI][Medline]

6 Sator S, Wildling E, Schabernig C, Akramian J, Zulus E, Winkler M. Desflurane maintains intraocular pressure at an equivalent level to isoflurane and propofol during unstressed non-ophthalmic surgery. Br J Anaesth 1998; 80: 243–4[ISI][Medline]





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