Traditionally in surgical practice, the decision to proceed to surgery is made between the surgeons and the patients. Whenever necessary, the patients are sent to other specialties (eg. anaesthesiologists, physicians, dietitians, physiotherapists) for consultation and optimization before elective surgery. This approach is acceptable for the majority of fit patients, it can however be unsatisfactory for high-risk frail patients undergoing major surgical procedures. Hong Kong is facing an aging population. According to the 2016-based population projections published by the Census and Statistics Department, the pace of population aging in Hong Kong will keep on ramping up in the coming 20 years or so. Between 2018 and 2038, the size and share of the elderly population will almost double from 1.27 million and 17.9% to 2.44 million and 31.9% respectively. With aging, there is an increase in frailty and a loss in functional and physiological reserve and adaptability, putting a patient that is exposed to a stressor, such as a major operation, at a higher risk of adverse outcomes. Frailty is associated with two to six- fold increased risk of major adverse cardiac and cerebrovascular events, longer stays in intensive care unit and hospital, a 1-year mortality. Pre-frail patients are also at risk of poor outcomes. Compared to non-frail patients, pre-frail patients (Clinical Frailty Score 4) had longer ICU stays, longer hospital stays, higher risk of postoperative stroke and a high risk of in-hospital mortality. Malnutrition and sedentary lifestyle are common in frail elderly patients. These have been demonstrated to be a recognizable risk factor of poor postoperative outcomes. It is therefore necessary to have a multidisciplinary team to manage frailty preoperatively.

Prehabilitation is a multidisciplinary and multimodal approach involving anaesthesiologists, physicians, physiotherapists, occupational therapists and dietitians that aims to optimize functional capacity, nutritional status and emotional resilience before surgery, so as to enable the patients to better withstand perioperative stress. It encompass individualized aerobic and resistance training to enhance cardiopulmonary fitness, dietary interventions to counteract the catabolic state of surgery, emotional support to improve resilience and advice on behavioural changes such as cessation of smoking and alcohol abuse. In the literature, prehabilitation has well been reported to enhance functional capacity before and after surgery. In particular, exercise training has been shown to improve various aspects of physical function of the frail elderly (eg. muscle strength, body composition, mobility, functional status and fall prevention). Tailored exercise training is therefore expected to improve physical fitness and increase functional capacity so that patients can better withstand the stress of surgery. In a systematic review, prehabilitation before orthopaedic surgery have beneficial effects in improving strength, flexibility, balance and speed in 5 out of 7 randomized controlled trials. Regarding postoperative clinical outcomes such as length of stay, readmission rate and postoperative complications rate, evidence demonstrated an association between physical fitness improvement and a lower rate and severity of complications. Despite the heterogenicity in study design and modalities of prehabilitation program, the positive effect of prehabilitation on perioperative functional fitness has been shown across a wide variety of surgical procedures, including abdominal aortic aneurysm repair, esophagectomy, cystectomy, liver resection and colorectal surgery. In general, individuals who have been frail and having a sedentary activity level would benefit the most from prehabilitation program. Preoperative malnutrition can be due to inadequate intake and high requirements from the disease process that results in reduced body mass, strength and function and a reduced ability to mount an immunological defense. All these can be significant in the high catabolic state perioperatively for the healing process and the systemic inflammatory response to surgery. Preoperative malnutrition is associated with many adverse outcomes. After adjusting for active smoking status, preoperative malnutrition was associated with postoperative complications after pneumonectomy and hepatectomy, a longer length of stay in hospital, higher readmissions within 28 days and a higher mortality up to 90 days after surgery. Nutritional prehabilitation therefore helps prepare and optimize the patients' nutritional status for surgery and recovery.

The timing and duration of prehabilitation program can affect the risk of postoperative outcomes. An ideal duration of prehabilitation has not been established and there is a large heterogenicity in duration from the literature. But in general, a minimum of three to four weeks is required to have an effect of physical fitness. Despite the need for novel resources, economic evaluation suggested that prehabilitation could be a cost-effective approach, the resulting benefits in short- and medium-term outcomes offset the costs of additional resources.

Most of the "fast-track" surgical pathways focus on intraoperative and postoperative measures to enhance recovery, and the traditional rehabilitation approach is to operate first and then intervene. However, postoperative pain, fatigue and wound care impede the efficiency of rehabilitation measures such as physiotherapy and nutritional program. Therefore, it would be more ideal to start intervention before surgery while patients can be more actively engaged in the process of perioperative care and functional improvement. The earlier the patients can be engaged, the greater the likelihood of having a meaningful impact and the less likely to affect the surgical schedule. The waiting time for surgery creates a window of opportunity to prepare the patients for prehabilitation by addressing problems of physical fitness, nutritional status and emotional distress. By re-engineering our preoperative assessment clinic and integration within the prehabilitation clinic, we are more able to risk stratify and identify high-risk patients at the time of preoperative evaluation. A common and one-stop platform can be shared by a multidisciplinary perioperative team with seamless communications, which reduces the chance of high-risk patients being bounced between independent consultations.

Changing the present structure and logistics of preoperative assessment clinic requires active participation of the stakeholders involved in perioperative care. Surgeons need to refer patients to anaesthesiologists as early as possible for further screening into prehabilitation program. Anaesthesiologists need to have new assessment strategies for functional capacity that are not traditionally used in routine preoperative assessment clinic. Physiotherapist, occupational therapist and dietitians should ideally set up a one-stop service model to minimize patient travel. Effective implementation requires buy-in from hospital administrators, investing resources to support this value-based approach. Therefore, the investigators will conduct a pilot retrospective observational study to evaluate the feasibility and impact of prehabilitation on our study participants before major elective surgery. In particular, for the feasibility part, the investigators aim to (1) estimate recruitment, attrition and adherence rate, and (2) ensure safety of prehabilitation. For the pilot part, the investigators aim to identify if there are any changes on the outcomes after the prehabilitation intervention, and (2) identify estimates of variance for sample size calculation for future randomized trials.