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Ocular tonometry in the child under general anesthesia with IM ketamine
Insights
Measuring ocular tension in young children requires anesthesia. Ketamine uniquely elevates ocular tension, necessitating prompt measurement post-induction to avoid inaccurate glaucoma assessment.
Area of Science:
- Ophthalmology
- Anesthesiology
- Pediatrics
Background:
- Ocular tension measurement in young children typically requires general anesthesia.
- Most anesthetic agents lower intraocular pressure, potentially leading to false-negative glaucoma diagnoses.
- Ketamine is a notable exception, as it tends to increase ocular tension.
Purpose of the Study:
- To quantify the change in ocular tension under ketamine anesthesia in children.
- To establish optimal timing for ocular tension measurement during ketamine anesthesia.
- To compare ocular tension changes between ketamine and other anesthetic agents.
Main Methods:
- Ocular tension was measured in 30 children without ocular disease after intramuscular ketamine administration (5-10 mg/kg).
- Measurements were taken 15-20 minutes after induction, once sedation was achieved.
- Ocular tensions were compared between ketamine and a combination of methohexital + Thalamonal anesthesia.
Main Results:
- Ocular tension remained stable initially but showed a tendency to rise after approximately eight minutes of ketamine narcosis.
- The study observed that ocular tension should be measured promptly after induction, as soon as the child is unresponsive to stimuli.
- Abnormal ocular tension findings under ketamine and comparisons with other anesthetics were discussed, including specific glaucoma case examples.
Conclusions:
- Prompt ocular tension measurement after ketamine induction is crucial for accurate assessment in pediatric patients.
- Understanding ketamine's effect on ocular tension is vital for diagnosing and managing pediatric glaucoma.
- Further research comparing anesthetic effects on pediatric ocular tension is warranted.
Abstract:
In the young child, the ocular tension cannot be taken without general anesthesia. Most of the anesthetic drugs lower the ocular tension which may give false low results in glaucoma. Ketamine is the only practical drug elevating the ocular tension. To determine the amount of the change in ocular tension under ketamine, the ocular tension was measured under I.M. ketamine 5 to 10 mg/kg in 30 children without ocular disease. The ocular tension before the anesthesia has not been measured. As soon as the child fell asleep, the ocular tension was recorded between 15 to 20 minutes. We noticed that the ocular tension remains stable in the beginning, but that it tends to rise after eight minutes of narcosis. So the ocular tension must be measured as soon as possible after induction, as soon as the child does not react to stimuli. Abnormal ocular tensions under ketamine are discussed. The ocular tensions under two different types of anesthesia (ketamine and methohexital + Thalamonal) are compared. Some examples of ocular tensions in glaucoma under ketamine are presented.