Enhanced recovery after surgery, protocol elements, evidence, outcome measures

Overview and Context

• The traditional model of anaesthetic care, confined to the operating theatre and the immediate perioperative window, is undergoing fundamental transformation.
• Two complementary frameworks have emerged to address the limitations of fragmented, episodic surgical care: Enhanced Recovery After Surgery (ERAS) and the Perioperative Surgical Home (PSH).
• Both represent a shift toward coordinated, evidence-based, patient-centred perioperative medicine, and both create expanded professional opportunities for anaesthetists as perioperative physicians.
• The impetus for these models arises from several converging pressures: escalating healthcare costs, rising surgical complexity, an opioid epidemic, increasing patient comorbidity, and a healthcare system increasingly focused on value, defined as outcomes achieved per unit cost.
• These models have demonstrated measurable improvements in outcomes, length of stay (LOS), complication rates, and cost-efficiency across multiple surgical specialties.

Enhanced Recovery After Surgery (ERAS)

Definition and Principles

ERAS protocols are evidence-based, multidisciplinary perioperative care pathways designed to accelerate postoperative convalescence, reduce surgical stress response, minimise complications, and facilitate early functional recovery, without increasing readmission rates.

• ERAS represents a paradigm shift: it replaces traditional surgical practices (prolonged fasting, routine bowel preparation, liberal opioid use, routine drains and tubes) with practices validated by high-quality evidence.
• The fundamental insight is that multiple simultaneous interventions targeting different aspects of the perioperative stress response achieve outcomes that no single intervention can achieve alone.

The concept underpins "fast-track" surgery and involves surgeons, anaesthetists, nurses, physiotherapists, nutritionists, and pharmacists working collaboratively within an integrated pathway.

The Surgical Stress Response: The Central Target

• The surgical stress response, mediated by neuroendocrine activation, inflammatory cascades, catecholamine release, and cytokine elaboration, drives postoperative catabolism, ileus, insulin resistance, immunosuppression, and organ dysfunction.
• ERAS protocols attack this response simultaneously from multiple vectors: attenuating afferent neural signals (regional anaesthesia), minimising the inflammatory trigger (minimally invasive surgery), maintaining metabolic homeostasis (carbohydrate loading, early feeding), and facilitating rapid return of function (early mobilisation, removal of lines and drains).
• Critically, good analgesia alone is insufficient to accelerate recovery, because acute pain is only one of many triggers of the injury response.
• This explains why well-controlled pain with thoracic epidural analgesia (TEA), while providing superior analgesia and earlier return of bowel function, does not consistently shorten LOS or reduce morbidity versus alternative techniques when used within a complete ERAS protocol.

ERAS Protocol Elements

• ERAS elements span the full perioperative continuum.
• The wedge model illustrates how each phase's interventions influence subsequent phases.

Carbohydrate Loading, Mechanistic Rationale

Preoperative oral carbohydrate drinks (typically a 12.5% carbohydrate solution, 800 mL the evening before and 400 mL 2 hours preoperatively) produce a metabolic anabolic shift with several benefits:

• Perioperative oral carbohydrates raise insulin sensitivity by approximately 50%, reducing postoperative insulin resistance
• Ameliorate gut barrier failure and reduce bacterial translocation risk
• Reduce risk of hyperglycaemic events
• Improve retention of protein and lean body mass
• Support the shift from a catabolic to anabolic metabolic state

The majority of national and international anaesthetic societies now recommend 6-hour fasting for light non-fatty solids and 2-hour fasting for clear fluids (including carbohydrate drinks).

Evidence for ERAS

ERAS has been most extensively evaluated in colorectal surgery, with robust evidence extending to gynaecology, orthopaedics, hepatobiliary, thoracic, vascular, and neurosurgical procedures. Key outcome data include:

• Elements most strongly associated with shorter LOS in colorectal surgery include: laparoscopic approach, increasing protocol compliance, preoperative carbohydrate and fluid loading, and TIVA.
• Factors reducing complication risk include restrictive perioperative IV fluids, laparoscopic approach, and increasing overall protocol compliance.
• Independent predictors of early recovery include enforced early oral intake (normal diet by POD 1-3) and early mobilisation.
• Importantly, the number of ERAS elements employed matters, protocols in major trials used between 4 and 12 elements (mean 9).
• Partial compliance yields attenuated benefit; comprehensive, audited implementation is essential.

Multidisciplinary Team Requirements

• The most successful ERAS programs include all healthcare and service providers involved in the perioperative course.
• This is not optional, the multidisciplinary nature is fundamental to the model's success.
• Without genuine engagement from surgical, nursing, physiotherapy, pharmacy, and nutrition teams alongside anaesthesia, protocols become fragmented and benefits are lost.
• Ongoing outcome measurement, audit, and protocol refinement are essential components.
• When adverse outcomes occur (e.g. acute kidney injury following implementation of restrictive fluid strategies in some colorectal ERAS protocols), the protocol must be reviewed and modified.
• This iterative approach, collaborative development, implementation, outcomes review, and modification, underpins the value-based healthcare rationale for ERAS.

Perioperative Surgical Home (PSH)

Definition and Conceptual Framework

• The Perioperative Surgical Home is a patient-centred, physician-led model of coordinated care that manages the patient from the time of surgical scheduling through the entire perioperative continuum, including the return to primary care.
• Developed by the American Society of Anesthesiologists (ASA) in collaboration with other medical specialties, the PSH builds on concepts from the Patient-Centred Medical Home (PCMH) model for outpatient chronic disease management.
• The PSH is broader in scope than ERAS.
• Where ERAS provides specific evidence-based protocol elements within the perioperative window, the PSH is an organisational and care coordination model that encompasses the entire patient journey, including scheduling, preoperative assessment, intraoperative and postoperative management, discharge planning, and transition to primary or community care.

Comparison: ERAS vs PSH

PSH Goals (as proposed by the ASA)

1. Identify the patient and proposed surgical plans
2. Facilitate communication among surgeons, anaesthesiologists, and other providers to coordinate care
3. Provide thorough preoperative assessment and develop a care plan, including management of associated diseases
4. Develop and implement evidence-based protocols for clinical care throughout the perioperative period
5. Manage clinical care across the continuum
6. Measure and publicly report outcomes and performance

The final goal, public reporting, reflects the PSH's alignment with value-based healthcare and the "triple aim" of improving patient experience, improving population health, and reducing per-capita costs.

The Anaesthesiologist as Perioperative Physician

• The PSH creates an expanded professional role for anaesthetists, building on their existing expertise in pathophysiology, pharmacology, monitoring, and perioperative risk.
• In PSH models where the anaesthesiologist assumes primary coordination responsibility, input from hospitalists and medical subspecialists remains essential to address specific clinical needs.

The PSH also has strategic professional implications: the collaborative relationships built under PSH models increase understanding of anaesthesiologists' skills and value within the health system, and critically position anaesthetists in discussions about bundled payment models and distribution of healthcare funding.

Models and Implementation

There is no single mandated PSH model, implementation varies by health system, institutional relationships, and provider interest. Observed benefits from PSH implementation have included:

Relationship to the Surgical Hospitalist Model

• The surgical hospitalist model, where a hospitalist (surgical or medical) manages non-surgical comorbidities perioperatively, freeing surgeons to focus on operative care, is complementary to but distinct from the PSH.
• The PSH incorporates clear delineation of roles between anaesthesiologist, hospitalist, and intensivist, particularly during transitions of care (e.g. theatre to ICU, ICU to ward, ward to home).
• Coordination of these transitions is a core PSH function.

Anaesthetic Implications

Role of the Anaesthetist in ERAS

As a consultant anaesthetist, engagement with ERAS should be proactive and informed. Key intraoperative contributions include:

Role of the Anaesthetist in PSH

• Lead or participate in preoperative assessment clinics with a focus on optimisation, not just risk stratification
• Develop and champion evidence-based perioperative protocols collaboratively with surgical teams
• Ensure clear handover documentation and care transitions (theatre → recovery → ward → home)
• Contribute to outcome measurement and protocol audit; be prepared to modify practice based on data
• Engage with postdischarge follow-up pathways; support telemedicine and home-monitoring initiatives increasingly used for postoperative care

Pitfalls and Challenges

Healthcare Economics

• ERAS and PSH both represent value-based approaches to perioperative care.
• Demonstrating value requires measuring outcomes that matter to patients, not just institutional metrics.
• Future ERAS protocol development must incorporate patient-reported outcome measures (PROMs) to ensure that shorter LOS and fewer complications translate into recovery experiences that patients themselves value.

The PSH model positions anaesthesiology to participate meaningfully in bundled payment models and healthcare funding discussions, a strategic professional opportunity that requires both clinical excellence and outcome data transparency.

Summary