- procedures under local anaesthesia - known history of adverse reaction/contraindication to trial drug - pregnancy and/or lactating patients (including patients undergoing caesarean section) - history of methaemoglobinaemia - patients receiving any type of prescribed nitric oxide-donating agents (e.g. nitroprusside, isosorbide dinitrate, isosorbide mononitrate, naproxcinod, molsidomine and linsidomine) - unable to tolerate use of a nebuliser and/or deemed unlikely to be able to adhere to protocol in view of investigator

- procedures under local anaesthesia - known history of adverse reaction/contraindication to trial drug - pregnancy and/or lactating patients (including patients undergoing caesarean section) - history of methaemoglobinaemia - patients receiving any type of prescribed nitric oxide-donating agents (e.g. nitroprusside, isosorbide dinitrate, isosorbide mononitrate, naproxcinod, molsidomine and linsidomine) - unable to tolerate use of a nebuliser and/or deemed unlikely to be able to adhere to protocol in view of investigator

- procedures under local anaesthesia. - symptomatic covid-19 infection (by confirmed covid-19 test or a clinical diagnosis); these patients will be eligible for the recovery trial. - existing regular preoperative treatment with trial drugs. - known history of adverse reaction/contraindication to trial drugs. - pregnancy (including caesarean section). - actively breastfeeding.

- procedures under local anaesthesia. - symptomatic covid-19 infection (by confirmed covid-19 test or a clinical diagnosis); these patients will be eligible for the recovery trial. - existing regular preoperative treatment with trial drugs. - known history of adverse reaction/contraindication to trial drugs. - pregnancy (including caesarean section). - actively breastfeeding.