Enhanced Recovery After Surgery (ERAS) Protocols

Enhanced Recovery After Surgery (ERAS) is a multimodal, evidence-based perioperative care pathway designed to reduce surgical stress, accelerate recovery, and minimize complications. Originally developed for colorectal surgery by Henrik Kehlet in the 1990s, ERAS has been successfully adapted to orthopaedic surgery, particularly total joint arthroplasty.

ERAS accelerates recovery because each element blunts the surgical stress response - the neuroendocrine and inflammatory reaction to tissue injury that drives catabolism and complications. This mechanism is the examiner's favourite 'why'.

• Neuroendocrine limb: afferent nociceptive and inflammatory signals activate the hypothalamic-pituitary-adrenal axis (raised ACTH and cortisol) and the sympathoadrenal system (catecholamines), with ADH and the renin-angiotensin-aldosterone system - producing hyperglycaemia and insulin resistance, protein catabolism (negative nitrogen balance, muscle loss), and sodium/water retention.
• Inflammatory limb: tissue trauma releases cytokines (IL-6 is the principal driver and correlates with the magnitude of injury, with IL-1 and TNF-alpha), producing the acute-phase response (CRP), fever and a degree of immunosuppression that raises infection risk.
• Ebb and flow: a brief early hypometabolic "ebb" phase is followed by a catabolic "flow" phase proportional to the magnitude of surgery.

How ERAS attenuates it: regional/neuraxial anaesthesia and multimodal analgesia block the afferent nociceptive limb; minimally invasive surgery reduces the tissue-injury stimulus; pre-operative carbohydrate loading and early enteral nutrition reduce insulin resistance and catabolism; and normothermia, euvolaemic goal-directed fluids and avoiding prolonged fasting/opioids limit the derangement. The synergistic blunting of this response - not any single element - is why the bundle works. Exam point: ERAS targets the cortisol/catecholamine and IL-6 stress response and its catabolism/insulin resistance, each element addressing a limb of that response.

The natural extension of a mature ERAS pathway is same-day-discharge (day-case/outpatient) hip and knee arthroplasty - increasingly performed and examinable.

• It is the same bundle: multimodal opioid-sparing analgesia, tranexamic acid, spinal anaesthesia with short-acting agents, no drain/no urinary catheter, and day-of-surgery mobilisation - but with discharge on the day of surgery rather than at 1-2 days.
• Patient selection is the safety-critical step: younger, motivated, ASA I-II patients without significant cardiac, pulmonary or obstructive-sleep-apnoea disease or poorly-controlled diabetes, a sensible BMI, low bleeding/VTE risk, and adequate home support with a responsible adult for the first 24 hours; validated tools such as the Outpatient Arthroplasty Risk Assessment (OARA) score aid selection.
• Safeguards: rigorous pre-operative education, a same-day discharge-criteria checklist (mobilising safely, pain controlled on oral analgesia, voiding, no concerning observations), a 24-hour telephone hotline with clear safety-netting, and audited readmission rates.
• Evidence: in well-selected patients, same-day discharge is safe, with readmission/complication rates comparable to inpatient pathways and high satisfaction - but it is not appropriate for the frail, comorbid or poorly-supported patient.

Exam point: day-case arthroplasty is ERAS plus stringent patient selection and safety-netting - the bundle is the same; the difference is who you choose and the support you wrap around same-day discharge.

Studies show that compliance with the full ERAS bundle is critical. Implementing only selected elements (e.g., just early mobilization without multimodal analgesia) will not achieve full benefits. Audit and feedback mechanisms are essential to maintain compliance.