Secondary outcome
- Repeat ESS in any subsequent admission within 180 days of discharge
from the index procedure. The same OPCS-4 codes listed above for ESS
were used to define repeat surgery. This follow-up period was chosen
to allow sufficient time for complications of index surgery to arise,
but to avoid cases of planned repeat surgery.
- Mortality at one year post-discharge. Mortality data were taken from
the UK Office for National Statistics (ONS).
- Likely complications of surgery identified during emergency admission
within 30 days post-discharge. These complications were defined within
five broad categories: haemorrhage, orbital injury, cerebrospinal
fluid leak, meningitis, other post-procedural complication. The ICD-10
codes used to define these complications are given inSupplementary material Table S1 .
- Haemorrhage was the most common recorded complication and was also
considered separately.