A comparison of postoperative respiratory complications associated with the use of desflurane and sevoflurane: a single-centre cohort study

Dynamic Stimulation Aberrometry: Objectively Measured Accommodation and Pupil Dynamics after Phakic Iris-Fixated Intraocular Lens Implantation

Purpose

Anterior iris-claw phakic intraocular lens (pIOL) implantation is a treatment option for refractive, ametropic patients. However, the postoperative accommodative ability has not been systematically researched. Dynamic stimulation aberrometry allows the objective and dynamical measurement of accommodation by observing ocular aberrations during the accommodation process. We investigated the dynamic accommodative ability after pIOL implantation compared with a healthy age- and gender-matched control group.

Design

Clinical, comparative case-control study.

Subjects

We included patients aged 18-50 years that either underwent pIOL implantation > 1 month ago or served as a healthy, phakic control group.

Methods

The accommodative ability and pupil dynamics of both groups were investigated using dynamic stimulation aberrometry. The method allows the analysis of dynamic parameters during accommodation, such as the accommodation speed. A 1:1 propensity score matching was conducted based on the patients' age and gender.

Main Outcome Measures

Parameters of objective accommodation, such as accommodative amplitude and pupil dynamic during accommodation.

Results

Fifty-eight healthy, phakic eyes < 50 years of age and 21 eyes after pIOL implantation to correct myopia (pIOL, Verisyse, AMO, Inc) were enrolled. Patients that underwent anterior pIOL implantation were examined on average 24 ± 18 months after surgery. After matching, the mean age of both groups was not significantly different (35 ± 8 vs. 34 ± 8 years). No significant difference in dynamic parameters of accommodation or the accommodative amplitude (2.8 ± 1.4 and 2.9 ± 1.4 diopters [D] for pIOL and control group, P = 0.82) were seen. Maximum and minimum pupil sizes were not significantly different. The change in pupil size during deaccommodation was significantly faster in patients after pIOL implantation (P < 0.001).

Conclusions

Dynamic stimulation aberrometry allowed the objective, dynamic, measurement of wavefronts in subjects with accommodative amplitudes up to 7 D. Phakic intraocular lens implantation does not impair the accommodative ability. It alters pupil dynamics during deaccommodation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Developing a quality improvement project to tackle the desflurane problem

Anaesthesia is associated with the routine use of volatile anaesthetic agents, all of which are potent greenhouse gases in varying degrees. Desflurane, in particular, has a high global warming potential and in recent years, there has been a global movement to reduce or remove its usage entirely from operating theatres. We work in a large tertiary teaching hospital in Singapore with deeply entrenched practices of using desflurane to facilitate high turnover of operating theatre cases. We launched a quality improvement project to (1) reduce the median usage of desflurane by 50% (by volume), and (2) reduce the number of theatre cases administering desflurane by 50% over a period of 6 months.We collected baseline data to determine departmental monthly median usage of desflurane. We then deployed sequential quality improvement methods to educate staff and to eliminate misconceptions, as well as to promote a gradual cultural change.We successfully reduced monthly median desflurane usage from 31.5 L to 12.2 L per month (61.3% reduction) within our targeted time frame. We also achieved a reduction in the number of theatre cases using desflurane by approximately 80%. This translated to significant cost savings of US$195 000 per year and over 840 tonnes of carbon dioxide equivalents saved.Healthcare is a resource intensive industry. Anaesthetists are well placed to play an important role in reducing healthcare-related carbon emissions by choosing anaesthetic techniques and resources responsibly. Through multiple Plan-Do-Study-Act cycles and a persistent, multifaceted campaign, we achieved a sustained change in our institution.

Association between intraoperative tidal volume and postoperative respiratory complications is dependent on respiratory elastance: a retrospective, multicentre cohort study

BACKGROUND

The impact of high vs low intraoperative tidal volumes on postoperative respiratory complications remains unclear. We hypothesised that the effect of intraoperative tidal volume on postoperative respiratory complications is dependent on respiratory system elastance.

METHODS

We retrospectively recorded tidal volume (Vt; ml kg^-1 ideal body weight [IBW]) in patients undergoing elective, non-cardiothoracic surgery from hospital registry data. The primary outcome was respiratory failure (requiring reintubation within 7 days of surgery, desaturation after extubation, or both). The primary exposure was defined as the interaction between Vt and standardised respiratory system elastance (driving pressure divided by Vt; cm H₂O/[ml kg^-1]). Multivariable logistic regression models, with and without interaction terms (which categorised Vt as low [Vt ≤8 ml kg^-1] or high [Vt >8 ml kg^-1]), were adjusted for potential confounders. Additional analyses included path mediation analysis and fractional polynomial modelling.

RESULTS

Overall, 10 821/197 474 (5.5%) patients sustained postoperative respiratory complications. Higher Vt was associated with greater risk of postoperative respiratory complications (adjusted odds ratio=1.42 per ml kg^-1; 95% confidence interval [CI], 1.35-1.50]; P<0.001). This association was modified by respiratory system elastance (P<0.001); in patients with low compliance (<42.4 ml cm H₂O^-1), higher Vt was associated with greater risk of postoperative respiratory complications (adjusted risk difference=0.3% [95% CI, 0.0-0.5] at 41.2 ml cm H₂O^-1 compliance, compared with 5.8% [95% CI, 3.8-7.8] at 14 ml cm H₂O^-1 compliance). This association was absent when compliance exceeded 41.2 ml cm H₂O^-1. Adverse effects associated with high Vt were entirely mediated by driving pressures (P<0.001).

CONCLUSIONS

The association of harm with higher tidal volumes during intraoperative mechanical ventilation is modified by respiratory system elastance. These data suggest that respiratory elastance should inform the design of perioperative trials testing intraoperative ventilatory strategies.

Greenhouse gas reduction in anaesthesia practice: a departmental environmental strategy

Sustainability interventions were implemented at the Royal Brisbane and Women’s Hospital (RBWH) following identification of inhaled anaesthetic gases as a target for reducing medical carbon emissions. This quality improvement study assessed and evaluated the impact of sustainability interventions on the environmental and financial cost of inhaled anaesthetic gas use in order to guide future initiatives and research in reducing carbon emissions from healthcare practice.

Ethical exemption was granted from the RBWH Research Ethics Committee (EX/2021/QRBW/76078). Usage (bottles) and expenditure for desflurane and sevoflurane from January 2016 to December 2021 were obtained. Global warming potential and carbon dioxide equivalent (CO₂e) were used to report environmental impact of volatile agents. Methods to estimate this were performed in Excel based on Campbell and Pierce methodology. An Environmental Protection Agency greenhouse gas equivalency calculator was used to convert CO₂e to equivalent petrol carbon emissions and kilometres travelled by a typical passenger vehicle.

The total number of bottles of sevoflurane and desflurane purchased between January 2016 and December 2021 decreased by 34.76% from 1991 to 1299. The number of desflurane bottles purchased decreased by 95.63% from 800 to 35 bottles. The number of sevoflurane bottles purchased increased by 6.13% from 1191 bottles to 1264 bottles. This was achieved by implementing quality improvement interventions such as staff education of desflurane-sparing practices, distribution of posters and progressive removal of desflurane from operating theatres. Total carbon emission from volatile anaesthetics equalled 2326 tonnes CO₂e. Combined desflurane and sevoflurane emissions decreased by 87.88%. In 2016, desflurane made up 92.39% of the annual CO₂e, which steadily decreased to 33.36% in 2021. Combined sevoflurane and desflurane usage costs decreased by 58.33%.

Substantial reductions in carbon emissions from volatile anaesthetics demonstrate the significant degree to which environmentally sustainable practices have been implemented. Applying desflurane-sparing practice can heavily limit anaesthetic drug expenditure and contribution to environmental waste. This is important given the global health sector’s challenge to optimise patient outcomes in the face of global climate change crisis.

Inhalational anaesthetics, ozone depletion, and greenhouse warming: the basics and status of our efforts in environmental mitigation

PURPOSE OF REVIEW

Following their use for medicinal purposes, volatile inhalational anaesthetic agents are expelled into the atmosphere where they contribute to anthropogenic climate change. We describe recent evidence examining the benefits and harms associated with their use.

RECENT FINDINGS

The environmental harms associated with desflurane and nitrous oxide likely outweigh any purported clinical benefits. Life cycle analyses are beginning to address the many gaps in our understanding, and informing choices made on all aspects of anaesthetic care. There is, however, an urgent need to move beyond the debate about anaesthetic technique A vs. B and focus also on areas such as sustainable procurement, waste management, pharmacological stewardship and joined-up solutions.

SUMMARY

There is now compelling evidence that anaesthetists, departments and hospitals should avoid desflurane completely, and limit nitrous oxide use to settings where there is no viable alternative, as their environmental harms outweigh any perceived clinical benefit. Life cycle analyses seem supportive of total intravenous and/or regional anaesthesia. There are many other areas where choices can be made by individual anaesthetists that contribute towards reducing the environmental burden of healthcare, such as prioritising the reduction of inappropriate resource use and over-treatment. However, this all requires joined up solutions where all parts of an organisation engage.

The expanded effects of sevoflurane on the nervous system: the harmful effect of residual concentration of sevoflurane on the respiratory system through neurogenic inflammation

Background

Neurogenic inflammation caused by sevoflurane may not only limite to the nervous system, but also expand to the respiratory system. The purpose of this study was to investigate the expression changes of transient receptor potential vanilloid 1 (TRPV1), neurokinin A (NKA), neurokinin B (NKB), calcitonin gene related peptide (CGRP) and substance P (SP) in 14, 21 and 42-day-old rats after inhaling 0.4% sevoflurane, in order to evaluate whether the residual sevoflurane be harmful to the respiratory system through neurogenic inflammation.

Methods

The anesthetic inhalation device was designed to allow 14, 21 and 42-day-old rats inhale 0.4% sevoflurane, while rats in the control group inhaled 40% O2 for 1h. Rats in the antagonist group inhaled 0.4% sevoflurane or 40% O2 for 1 h after Capsazepine (CPZ) pretreatment. The expression of TRPV1 in lung tissue was detected by western blot, and the expression of NKA, NKB, CGRP and SP in trachea was detected by immunohistochemistry.

Results

After inhaling 0.4% sevoflurane, the expression of TRPV1 in lung tissue of 14 and 21-day-old rats was significantly higher than that of the control group, as well as increased the expression of CGRP and SP in the trachea of 14-day-old rats and NKA, NKB, CGRP and SP in the trachea of 21-day-old rats. CPZ pretreatment could antagonize these effects.

Conclusion

Residual sevoflurane during resuscitation of inhalation anesthesia could induce neurogenic inflammation by activating TRPV1, which damaged to the developing respiratory system, but has no significant effect on the respiratory system in adulthood.