This study finds a reduction in the number of surgical interventions, the number of elective surgeries, and the intravenous maintenance of anesthesia during the first wave of the COVID-19 pandemic. The largest decreases in the proportion of surgeries were seen in ear, nose, and throat (ENT) and oral surgery. The number of performed surgical interventions had not recovered to pre-pandemic levels 1 year into the pandemic.

The pandemic had an impact on perioperative care in many countries, and during 2020 it was predicted that about 80% of surgeries would be postponed during the peak of the COVID-19 pandemic (COVIDSurg Collaborative 2020). A decrease in the number of surgeries was seen during the COVID-19 pandemic in the Europe (Shaw et al. 2022), the USA (Zhong et al. 2021), Japan (Okuno et al. 2021), and North and South America (Beninato et al. 2022), and a decrease in the number of elective surgeries was also described (Beninato et al. 2022). The ratio between the numbers of elective and acute surgeries in south-east Queensland, Australia was similar to that found here: the proportion of elective surgeries decreased from 65.18% in March–April 2019 to 58.96% during the first wave of the COVID-19 pandemic (March–April 2020) (Fowler et al. 2021), compared with our finding of a slightly greater decrease from 70.2 to 59.3%. Also, in south-east Queensland, the surgical specialties experiencing the largest decrease were similar to those found here: a decrease from 7.2 to 4.6% was seen for maxillo-facial/dental/ENT surgery and from 6.1 to 3.6% for ophthalmologic surgery (Fowler et al. 2021). Similar decreases in ophthalmologic and ENT surgeries were also described in Japan during the first wave of the COVID-19 pandemic (Okuno et al. 2021). In our results, we also identified an increase in interventions involving chest wall, pleura, mediastinum, diaphragm, trachea, bronchus, and lung during the first wave of the pandemic. It is possible that this increase could be related to the rise in patients developing acute respiratory distress syndrome needing intensive care and mechanical ventilation (Meyer et al. 2021).

We could identify a shift in the choice of maintenance anesthesia to volatiles during the first wave of the COVID-19 pandemic. This can be explained by the shortage of drugs caused by the increased number of patients needing sedation in ICUs. To our knowledge, this shift has not been described before. Shaw et al. described a shift in anesthetic techniques from GA to regional/local anesthesia in patients undergoing hand surgery, and noted that more surgeries were performed in minor OR settings (Shaw et al. 2022). Takazawa et al. identified a decrease in GA during the first wave of the COVID-19 pandemic (Takazawa et al. 2021). We also found a reduction in GA in our study, but mainly due to the decrease in the number of surgeries.

The number of acute surgeries remained stable during the three studied periods, indicating that the perioperative organizations were able to maintain acute perioperative care. This has also been indicated earlier by Holmström et al. (Holmström et al. 2023). We could not identify any large differences in postoperative outcomes between the pre-pandemic period and the first wave of the pandemic. Even though a higher proportion of volatiles was in use, the incidence of PONV increased only slightly. Possibly, the above results indicate that anesthesiology settings and PACUs are resilient organizations that could maintain acceptable postoperative care despite the vast workloads and changes to routines imposed on these units during the COVID-19 pandemic. Organizations that have the capacity to maintain an acceptable level of functioning have a higher organizational resiliency (Barasa et al. 2018). One year into the pandemic (period 3), the number of surgeries had recovered somewhat but had still not reached the pre-pandemic level. This means that a large number of patients have waited and are still waiting for surgeries in Sweden.

The present results highlight the impact that the pandemic has had on perioperative care and on different surgical specialties. It also highlights the need for sufficient resources to restore the perioperative organizations so they can handle the remaining care backlog. The staff who coped with the large inflow of critically ill patients and the new constraints during the COVID-19 pandemic are the same staff who must now work to provide safe and high-quality perioperative care to a large number of patients.

This study has several limitations. The large volume of data analyzed means that even small differences can be statistically significant. Therefore, the results need to be interpreted from the perspective of what is clinically relevant.

SPOR does not cover all surgical interventions in Sweden. Not all settings report postoperative data and outcomes to SPOR, and we found quite a large proportion of missing data. Only 33 settings were included in the analysis regarding postoperative outcomes. It is likely that other results could have been identified if all settings reported postoperative outcomes and were included in the analysis. There could also be some errors in the reporting of postoperative outcomes. All postoperative outcomes are manually reported by the staff working in the PACUs. It is possible that, due to the increased workload and staff changes during the pandemic, such reporting was deprioritized and that false values were reported. We therefore recommend that our results should be interpreted with that in mind.

Other postoperative outcomes registered in SPOR, such as postoperative complications, are of interest. These variables are still not reported by all settings to SPOR, and as we found a large volume of missing data for these variables, we did not include them in this study.

In present study, we report register data from SPOR that only includes perioperative data. Future studies should investigate whether there was an increase in unexpected admissions and readmissions related to the decreased number of performed surgeries and the increased proportion of volatiles used.