The effect of nitrous oxide on intra‐ocular pressure in healthy adults*

Abstract

SummaryMany anaesthetic agents affect intra-ocular pressure, yet little is known about nitrous oxide and intra-ocular pressure. This study assessed the effect of nitrous oxide on intra-ocular pressure in 20 healthy adult volunteers. The intra-ocular pressure was measured at baseline, while breathing a 70:30 mix of nitrous oxide and oxygen for 12 min, and then while breathing room air for 15 min. A linear mixed effects model was used to assess change in intra-ocular pressure over time. There was no significant difference in intra-ocular pressure between baseline and during or after nitrous oxide inhalation. Several differences in intra-ocular pressure were noted between internal time-points: pressure increased by 2.4 mmHg between 3 and 6 min of breathing nitrous oxide (p = 0.01); it increased by 1.4 mmHg between 3 and 9 min of breathing nitrous oxide (p = 0.046); and it decreased by 2.2 mmHg between 6 min of breathing nitrous oxide and 15 min of breathing room air (p = 0.035). This study indicates that nitrous oxide inhalation does not significantly change intra-ocular pressure from baseline values in a population of healthy adults. Accepted: 25 October 2011There have been few studies to assess the effect of nitrous oxide (N 2 O) on intra-ocular pressure (IOP) [1]. This is an important question, as many anaesthetic agents produce clinically significant changes in IOP. Volatile agents like halothane, isoflurane and sevoflurane have been shown to decrease IOP, as has the intravenous anaesthetic agent propofol [2][3][4]. Other drugs, such as suxamethonium, can produce an increase in IOP [5]. Several human and animal studies have peripherally investigated the effect of N 2 O on IOP, but all have used N 2 O in combination with anaesthetic agents that are known to affect IOP [6][7][8]. One report indicates that N 2 O seems to have no effect on IOP, but supporting data or references are not given [9]. To our knowledge, there are no other studies that have explored the effect of isolated N 2 O administration on IOP in humans.Reliable IOP measurements are essential for the effective management of glaucoma, yet accurate values are

The Effect of Nitrous Oxide on the Intraocular Pressure in Patients Undergoing Abdominal Surgery under Sevoflurane and Remifentanil Anesthesia

“…Lalwani et al have shown that nitrous oxide inhalation did not significantly change IOP from baseline values in a population of healthy adults [13]. Our result of present study was consistent with their result.…”

“…Based on the present and previous similar study [11]- [13], the effect of N 2 O would not affect the IOP during 3 hours sevoflurane and remifentanil anesthesia in patients undergoing abdominal surgery. Our study had the following possible limitations.…”

“…Although major determinants for IOP include the production rate of aqueous humor, vitreous volume, sclera rigidity, choroidal blood volume, and orbicularis oculi muscle tension [12], there have been few studies to assess the effect of nitrous oxide on IOP [10]- [13]. Lalwani et al have shown that nitrous oxide inhalation did not significantly change IOP from baseline values in a population of healthy adults [13].…”

“…Moreover, N 2 O has been shown to have no influence in healthy volunteer [13]. On the other hand, detrimental effect of N 2 O is reported, indicated that the use of N 2 O in patients, who undergo vitreoretinal procedures cause retinal or optic nerve ischemia, results in visual loss [14]- [16].…”

The effect of nitrous oxide on intra‐ocular pressure

“…I read with interest the recent article by Lalwani et al demonstrating that nitrous oxide (N 2 O) did not significantly change intra‐ocular pressure (IOP) from baseline in healthy adults [1]. The authors concluded that this raises the possibility of using N 2 O to aid IOP measurement, either as a sole inhalational agent or as part of a multi‐agent protocol.…”