| Neck wound infection | Localised and superficial to platysma, e.g. stitch abscess | I |
| Spreading cellulitis or superficial wound infection with no underlying collection treated with antibiotics | II |
| Collection deep to platysma requiring drainage (not under GA) | IIIa |
| Collection deep to platysma requiring drainage (under GA) | IIIb |
| Large collection with organ and/or life-threatening sequelae (i.e. airway obstruction, severe sepsis, septic shock) | IV (a or b depending on organ dysfunction) |
| Other surgical site infection | Localised infection requiring topical or non-invasive treatment | I |
| Infection requiring treatment with antibiotics only | II |
| Collection requiring drainage (not under GA) | IIIa |
| Collection requiring drainage (under GA) | IIIb |
| Large collection with organ and/or life-threatening sequelae (i.e. airway obstruction, severe sepsis, septic shock) | IV (a or b depending on organ dysfunction |
| Bleeding/haematoma | Haematoma not requiring drainage or suitable for simple aspiration with a needle (not radiologically guided) | I |
| Need for blood transfusion | II |
| Requiring drainage (not under GA). Includes radiologically guided aspiration/drainage | IIIa |
| Requiring drainage or return to theatre for haemostasis (under GA) | IIIb |
| Haematoma/haemorrhage sufficiently large to obstruct airway or cause hypovolaemic shock | IV (a or b depending on organ dysfunction) |
| Chyle leak | Low output leak (< 500âml/24âh) suitable for low-fat diet and compression only | I |
| Requirement for pharmacological management including total parenteral nutrition | II |
| Radiologically guided occlusion | IIIa |
| Return to theatre for the procedure under GA | IIIb |
| Evidence of end-organ dysfunction | IV (a or b depending on organ dysfunction) |
| Wound breakdown | Superficial skin dehiscence (platysma layer intact) managed with dressings | I |
| Small fistula managed by an enteral tube or parenteral nutrition only | II |
| Deep dehiscence (through platysma layer) or fistula managed with procedure not under GA | IIIa |
| Deep dehiscence (through platysma layer) or fistula managed with the procedure under GA | IIIb |
| Evidence of end-organ dysfunction | IV (a or b depending on organ dysfunction) |
| Seroma/sialocele | Small collection not requiring drainage or suitable for aspiration with a needle (not radiologically guided) | I |
| Salivary fistula managed medically (e.g. anticholinergic) | II |
| Requiring drainage (not under GA). Includes radiologically guided aspiration/drainage | IIIa |
| Requiring re-exploration and/or drainage (under GA) | IIIb |
| Large collection obstructing airway | IVa |
| Hypersensitivity | Mild reaction not requiring treatment | I |
| Mild/moderate/severe reaction treated with medication (e.g. antihistamine and/or steroid and/or adrenaline) | II |
| Anaphylactic shock | IV (a or b depending on organ dysfunction) |
| Air embolism | By definition clinically evident air embolism results in cardiorespiratory dysfunction | IVb |
| Pneumothorax/haemothorax | Small pneumothorax managed without a chest drain | I |
| Pneumothorax/Haemothorax without respiratory failure requiring chest drain | IIIa |
| Evidence of respiratory failure or any other organ dysfunction | IV (a or b depending on organ dysfunction) |
| Pulmonary embolism | Small PE without evidence of respiratory failure managed with anticoagulation only | II |
| Evidence of respiratory failure or any other organ dysfunction | IV (a or b depending on organ dysfunction) |
| Deep vein thrombosis | Managed with anticoagulation only | II |
| Need for endovascular intervention including filters not under GA | IIIa |
| Need for endovascular intervention or surgical thrombectomy under GA | IIIb |
| Lower respiratory tract infection (including aspiration) | Managed with physiotherapy only | I |
| Managed with antibiotics | II |
| Evidence of respiratory failure or any other organ dysfunction | IV (a or b depending on organ dysfunction) |
