Effect of Anesthesia on Intraocular Pressure Measured With Continuous Wireless Telemetry in Nonhuman Primates

Abstract

PurposeTo compare the effects of both injectable anesthesia (ketamine/dexmedetomidine versus ketamine/xylazine) and inhalant anesthesia (isoflurane) on IOP using continuous, bilateral IOP telemetry in nonhuman primates (NHP).MethodsBilateral IOP was recorded continuously using a proven implantable telemetry system in five different sessions at least 2 weeks apart in four male rhesus macaques under two conditions: ketamine (3 mg/kg) with dexmedetomidine (50 μg/kg) or ketamine with xylazine (0.5 mg/kg) for induction, both followed by isoflurane for maintenance. IOP transducers were calibrated via anterior chamber manometry. Bilateral IOP was averaged over 2 minutes after injectable anesthetic induction and again after isoflurane inhalant had stabilized the anesthetic plane, then compared to baseline IOP measurements acquired immediately prior to anesthesia (both before and after initial human contact).ResultsWhen compared to pre-contact baseline measurements, ketamine/dexmedetomidine injectable anesthesia lowers IOP by 1.5 mm Hg on average (P < 0.05), but IOP did not change with ketamine/xylazine anesthesia. IOP returned to baseline levels shortly after isoflurane gas anesthesia was initiated. However, injectable anesthesia lowered IOP by an average of 5.4 mm Hg when compared to that measured after initial human contact (P < 0.01).ConclusionsAnesthetic effects on IOP are generally small when compared to precontact baseline but much larger when compared to IOP measures taken after human contact, indicating that IOP is temporarily elevated due to acute stress (similar to a “white coat effect”) and then decreased with anesthetic relaxation. Anesthetic induction with ketamine/xylazine and maintenance with isoflurane gas should be used when IOP is measured postanesthesia.

Ocular Pulse Amplitude Correlates With Ocular Rigidity at Native IOP Despite the Variability in Intraocular Pulse Volume With Each Heartbeat

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Glaucoma through Animal’s Eyes: Insights from the Evolution of Intraocular Pressure in Mammals and Birds

“…The type of tonometer (applanation and rebound tonometer) and sedation used during IOP measurements influence IOP [ 21 , 39 ]. However, our IOP data were obtained with various types of tonometer, and some of the IOPs were measured while animals were sedated.…”

Intra-Subject Variability and Diurnal Cycle of Ocular Perfusion Pressure as Characterized by Continuous Telemetry in Nonhuman Primates

“…2)-which allow continuous measurement of IOP and arterial BP up to 500 times per second for approximately 24 months. These telemetry systems measured IOP and arterial BP either continuously (Konigsberg; 500 Hz) 39,[42][43][44][45][46] or on a 10% duty cycle of 15 seconds out of every 150-second period (TSE Systems Stellar; 200 Hz). 47 All animals underwent surgical implantation of the telemetry system, including bilateral IOP sensors and an arterial BP sensor placed in the lumen of the femoral, carotid, or aortic artery, as described previously.…”