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Propofol influences the electroretinogram to a lesser degree than thiopentone
P Tanskanen1, T Kylmä, B Kommonen
1Department of Anaesthesia at Töölö Hospital, Helsinki University Central Hospital, Finland.
Insights
Propofol anesthesia better preserves retinal function for electroretinograms (ERG) compared to thiopentone. This finding is crucial for ERG recordings in pediatric and uncooperative patients requiring anesthesia.
Area of Science:
- Ophthalmology
- Anesthesiology
- Neuroscience
Background:
- Electroretinogram (ERG) assesses retinal function.
- Anesthetic agents can impact ERG results, necessitating study in pediatric and uncooperative patients.
- Barbiturates are known to depress ERG components.
Purpose of the Study:
- Compare the effects of propofol and thiopentone on ERG.
- Determine if propofol better preserves retinal function during anesthesia for ERG.
Main Methods:
- Ten pigs underwent anesthesia with either propofol or thiopentone, with a crossover design after one week.
- ERG responses to graded light intensities were recorded after dark adaptation.
- Key ERG parameters including a- and b-wave amplitudes and implicit times were analyzed.
Main Results:
- Propofol anesthesia resulted in a significantly shorter b-wave implicit time, especially at low light intensities.
- No significant differences were observed in b-wave amplitudes between the two anesthetics.
- The a-wave appeared at lower stimulus intensities and showed steeper slopes under propofol anesthesia.
Conclusions:
- Propofol appears to preserve photoreceptor response more effectively than thiopentone.
- Propofol may be a more suitable anesthetic agent for ERG recordings.
Background:
The Electroretinogram (ERG) is used clinically to assess the function of retina. Anaesthetic agents are known to affect ERG, and as anaesthesia is often needed in children and uncooperative patients, knowledge about its effects is of clinical importance. Barbiturates selectively depress ERG components, and we compared thiopentone with propofol to assess if the latter preserved retinal function better.
Methods:
Ten pigs, average weight 17 kg (SD +/- 2 kg) were anaesthetized randomly with propofol 10 mg kg-1 or thiopentone 30 mg kg-1. Anaesthesia was maintained by 65% nitrous oxide in oxygen and continuous infusion of the induction agent, i.e. 10 mg kg-1 h-1 of propofol, or 10 mg kg-1 h-1 for the first hour, then 5 mg kg-1 h-1 of thiopentone, with doses being based on pilot studies. After an interval of one week the programme was repeated using the other agent. After 40 minutes dark-adaptation, responses to single flashes of graded intensities from a xenon flashlamp were recorded at five-minute intervals. The a- and b-wave amplitudes and implicit times (time to peak), and a-wave slopes were determined.
Results:
The b-wave implicit time was significantly shorter during propofol anaesthesia than when using thiopentone. The effect was most pronounced at the lowest intensities (P < 0.01). No statistically significant differences were found in the amplitudes of the b-waves. The a-wave appeared at lower stimulus intensity (P < 0.05) and the a-wave slopes were significantly steeper (P < 0.01) during propofol anaesthesia.
Conclusion:
Propofol accordingly appeared to preserve the photoreceptor response better than thiopentone, and may therefore be considered to be more suitable for ERG recordings than thiopentone.