Perioperative care in cardiac surgery

Learning objectives.

By reading this article you should be able to:

• •Identify the key components of the enhanced recovery after surgery (ERAS) pathway for patients undergoing cardiac operations.
• •Discuss the multiple factors involved in recovery after cardiac surgery.
• •Review strategies to reduce the use of opioids in the ERAS pathway.

Key points.

• •Perioperative care refers to the care of the patient from the point at which surgery is first considered through to their recovery.
• •Enhanced recovery is a new but growing concept for cardiac surgical patients.
• •Prehabilitation is a multimodal approach to enhance an individual's functional capacity to withstand the stress of surgery.
• •Patient blood management (PBM) involves using a range of interventions to avoid unnecessary blood transfusions and hence improve outcomes.
• •Greater compliance to a pathway is associated with better clinical outcomes.

Perioperative medicine is a growing area of interest within anaesthesia, critical care and surgical specialties worldwide. In recent years enhanced recovery after surgery (ERAS) principles have become central to high-quality care in many surgical specialties. These ERAS principles are based upon the development of evidence-based protocols to engage patients in their care, reduce the stress response to surgical trauma and enable the patient to recover normal function more rapidly after major surgery. These goals are achieved through consistent application of evidence-based best practices and reducing unnecessary clinical variation. The potential for improving patients' and healthcare system's outcomes has increased in our modern era of increasingly complex patients, and new developments in anaesthetic and surgical techniques, despite growing constraints on healthcare budgets. Overall, this fundamentally shifts the traditional paradigm of care from an individual clinician model, to a holistic, collaborative, multidisciplinary approach that aims to optimise the patient's experience and outcomes.

Although rooted in the approach originally championed by the early founders of ERAS for non-cardiac surgery, there are several important differences in the development of programmes for patients undergoing cardiac surgical procedures. These differences present both unique challenges and opportunities in the development and implementation of ERAS programmes in cardiac surgery. In the 1980s, increased demands, limited resources and economic pressures led many centres to initiate ‘fast-track’ care pathways. These pathways were focused on reducing the time to tracheal extubation as a means to reduce ICU stay, and they differ significantly from a holistic patient-centred ERAS approach. The ERAS Cardiac Society has recently published evidence-driven recommendations for pathways to optimise patients' care in cardiac surgery.¹

Cardiac surgery covers a range of surgical techniques and a variety of physiological insults that may have an impact on postoperative recovery. As in any other specialty, the patient's own pre-existing comorbidities have the greatest effect on outcome. These factors include the condition requiring surgery such as acute infective endocarditis and pre-existing conditions such as anaemia, diabetes or chronic kidney disease (CKD). The urgency, complexity and duration of both surgery and cardiopulmonary bypass (CPB) all have a major influence on recovery. Complex surgery requiring long CPB times, the use of profound hypothermia, reduced cerebral perfusion and potentially greater blood loss all increase adverse events and prolong recovery. Postoperative complications such as bleeding, which may lead to cardiac tamponade, acute kidney injury (AKI) and the requirement for resternotomy, affect recovery and prevent ERAS goals being achieved. Despite all these complexities, the adherence to multimodal, evidence-based pathways in the perioperative period is fundamental for optimum benefit and the success of the programme. However, a ‘one-size-fits-all’ approach will inherently risk limiting the potential benefits for patients, fail to achieve the desired gains in efficacy and reduce satisfaction within the healthcare team. These conflicting principles must be acknowledged to allow individual treatment and differences between units. Enhanced recovery after surgery programmes are a collection of interventions, which alone may be of little benefit but when taken as a collective pathway result in significant gains and improvement in the patient's experience and outcome.

Patients presenting for cardiac surgery are likely to benefit from an ERAS programme as there are common features in the nature of the surgery and patients' characteristics. The basic steps involve ensuring that the patient presents for surgery in the best possible physical and psychological condition. Management during surgery is optimised to agreed best practice, and every effort is made to ensure early recovery of function (such as mobility and nutrition). Table 1 illustrates this approach.

Table 1.

Cardiac enhanced recovery pathway (reproduced from NHS Improvement for use in South Tees Hospital). PPI, proton pump inhibitor

<-------Active patient involvement-------->
Referral from primary care	Preoperative	Admission	Intraoperative	Postoperative	Follow-up
•Optimising haemoglobin concentrations •Managing pre-existing comorbidities (e.g. diabetes, hypertension)	•Health and risk assessment •Good quality patient information •Informed decision-making •Patient surgery school •Optimised health/medical conditions •Therapy advice •Nutritional advice •Discharge planning	•Admit on night before or day of surgery •Optimise fluid hydration •Minimise fasting period (i.e. solids 6 h liquids 2 h) •Avoid routine use of sedative premedication •Carbohydrate preloading •Gabapentin and PPI	•Surgical site infection reduction •Temperature management •Tranexamic acid •Opioid-sparing analgesics •Use of local anaesthetic to wound and drain sites •Antiemetic prophylaxis	•Sedation hold and extubation •Active, planned mobilisation within 4 h of extubation •Systematic delirium screening •Early oral hydration •Early oral nutrition •Early drains and catheter removal •Glycaemic control •Thromboprophylaxis •Avoidance of systemic opioid-based analgesia when possible	•Discharge on planned day or when criteria met •Therapy support (physiotherapy, dietician, community nurse) •24 h telephone follow-up if appropriate
<-------Whole team involvement-------->

Preoperative preparation

The patient should be at the centre of their ‘contract of care’. This involves providing sufficient information to obtain informed consent for surgery, but also a detailed discussion of anticipated events, the importance of preoperative interventions (see below) and expectations about early mobilisation and return to normal function. This timely and honest discussion is an essential part of enhanced recovery and relies upon consistent transfer of good quality information.

Before referral from primary care

Many patient-related risk factors can be modified by changes in behaviour or medication before referral. These should be started early in the progress by the referring physician (usually a cardiologist) with the patient's primary care doctor playing an active role. Initial screening of fitness for surgery should identify risk factors such as poorly controlled diabetes or hypertension, and factors associated with an increase in complications such as anaemia or impaired renal function. Behavioural changes can address alcohol intake, cigarette smoking and poor cardiorespiratory fitness.² By establishing these plans early, best use can be made of the time between referral and an outpatient appointment. Primary care physicians can also provide information on extra support that may be needed such as social care on discharge from hospital.

Risk assessment and stratification

All patients undergoing cardiac surgery have a thorough risk assessment to score for intraoperative risk. Models such as the European System for Cardiac Operative Risk Evaluation (EuroSCORE) and Society of Thoracic Surgeons (STS) adult cardiac surgery risk score can be used to identify high-risk patients. These risk scoring systems focus on the overall risk for the procedure and do not, necessarily, involve a holistic consideration of the patient's other comorbidities and modifiable factors. This information provides a greater understanding for the patient, improves decision-making, allows preoperative optimisation and enables the surgical technique or procedure to be altered if needed.

Adequate preoperative glycaemic control is defined as a haemoglobin A1_c (HbA1_c) concentration value ≤6.5%; optimising glycaemic control reduces morbidity and postoperative complications such as myocardial injury and surgical site infections. Similarly, hypoalbuminaemia can be a useful marker to identify patients at increased risk of prolonged mechanical ventilation, AKI, infectious complications, longer hospital stay and increased mortality. The cardiac ERAS guidelines recommend measuring HbA1_c and albumin to assist with risk stratification, with a moderate quality level of evidence.³

Patients with low Hb concentrations have a far higher in-hospital mortality than those with normal concentrations. For example, an Hb concentration ≤10 g dl⁻¹ is associated with a five-fold increase in mortality, and lesser degrees of anaemia are also associated with increased risks of morbidity and mortality.⁴ Anaemia should be investigated before cardiac surgery and treated where possible.⁵ Iron deficiency is one of the most common causes of anaemia before surgery, and underlying causes should be excluded. Patients will sometimes present for cardiac surgery with an identified cause of anaemia, such as malignancy or CKD, which requires good patient blood management with iron, transfusion, or both. Oral iron therapy is tolerated poorly and may be less effective in treating anaemia, particularly in the period shortly before surgery. Intravenous iron, such as ferric carboxymaltose preparations, may be better for a quicker and more sustained response. Iron therapy should also be considered (with or without erythropoiesis-stimulating agents) in anaemia of chronic disease where, despite normal or high serum ferritin concentration, there may be concurrent absolute or relative iron deficiency.⁶ Studies are currently underway to determine the impact of preoperative iron therapy on transfusions and outcomes after cardiac surgery.

Prehabilitation

Prehabilitation is the process of augmenting a patient's functional status to withstand the stress of subsequent surgery. This includes education, correcting nutritional deficiencies, optimising physical fitness and providing psychological and social support. The net result of these interventions is to reduce the patient's anxiety and increase their understanding of the surgical process.

Cardiac surgery school

The concept of multidisciplinary surgery school in cardiac surgery is a novel approach. Surgery school provides an environment for the patient and their relatives to learn and about their perioperative course and how they can influence it. This helps to reduce psychological stress and improve their recovery. The education can take place face to face or via an online programme. At James Cook University Hospital the patient views educational videos on digital devices whilst waiting in the clinic. These sessions emphasise the importance of being active, living well, eating well and physical training to improve respiratory and muscle function before the surgery.

Preoperative exercise

Exercise programmes that improve physical fitness are deemed safe in patients with cardiorespiratory conditions, although current evidence in cardiac surgery is limited.² This can be high-intensity interval training alone or in combination with muscular strength training. A preoperative exercise programme may decrease perioperative sympathetic dysregulation and insulin resistance, and increase the ratio of lean body mass to body fat.⁷ Additional benefits include improving the patient's physical and psychological readiness for surgery, reducing postoperative complications, shortening length of stay and improving the patient's experience during recovery before returning home.⁸ This needs to be individualised according to a patient health status.

Lifestyle modifications

Smoking, excessive alcohol use and obesity are all associated with perioperative complications and poorer outcomes and should be screened for before surgery. Serious cardiorespiratory complications and wound infections can be significantly reduced with abstinence from smoking starting 3–8 weeks before surgery. The main points of preoperative intervention are individual counselling to explain the results and benefits of abstinence, and how to manage immediate withdrawal symptoms.⁹

Minimisation of fasting and giving a preoperative carbohydrate load

Giving clear fluids up to 2 h before induction of anaesthesia has been previously shown to be safe.¹⁰ A carbohydrate drink (typically containing 24 g complex carbohydrate) 2 h before surgery has been a mainstay of most ERAS programmes. In non-cardiac patients this practice has led to reduced insulin resistance and tissue glycosylation, more stable postoperative glucose concentrations and earlier return of normal gastrointestinal function.¹¹ A Cochrane review found that giving carbohydrate drinks before cardiac surgery is safe and improves cardiac function immediately after CPB.¹² For these reasons ERAS programmes usually include preoperative carbohydrate drinks the night before and 2 h before surgery.

Intraoperative interventions

Reducing surgical site infections

The incidence of surgical site infection is 1.1–7.9%. This prolongs the duration of hospital stay, increases healthcare-related costs and is associated with high morbidity and mortality after cardiac surgery.¹³ A care bundle to reduce surgical site infections should include topical intranasal therapies to eradicate staphylococcal colonisation, weight-based doses of cephalosporin antibiotics between 30 and 60 min before skin incision (repeated after 4 h if surgery is ongoing), skin sterilisation with cleaning solution and depilation protocols with dressing changes every 48 h.¹⁴ Smoking cessation, adequate glycaemic control and maintaining normothermia after surgery also play a vital role.

Avoiding hyperthermia

Cardiopulmonary bypass may be carried out at normothermic or hypothermic body temperatures. The efficiency of heat exchangers means that patient can be subjected to inadvertent hyperthermia especially during rewarming from hypothermic CPB. Excessive hyperthermia during rewarming is defined as a core temperature >37.9°C and is associated with increased postoperative neurological injury, infection and renal dysfunction. Guidelines for rewarming to mitigate these risks have been published (Table 2).¹⁵

Table 2.

Recommendations for temperature management during CPB (adapted from Ann Thoracic Surg, Special Report| Volume 100, Issue 2, pp. 748–57, August 1, 2015). CPB, cardiopulmonary bypass

Optimal site for temperature measurement	–The oxygenator arterial outlet blood temperature is recommended to be used as a surrogate for cerebral temperature measurement during CPB. –To monitor cerebral perfusate temperature accurately during warming, it should be assumed that the oxygenator arterial outlet blood temperature underestimates cerebral perfusate temperature. –Pulmonary artery catheter or nasopharyngeal temperature recording is reasonable for weaning and immediate temperature measurement after CPB.
Avoidance of hyperthermia	–Surgical teams should limit arterial outlet blood temperature to <37°C to avoid cerebral hyperthermia.
Peak cooling temperature gradient and cooling rate	–Temperature gradients from the arterial outlet and venous inflow on the oxygenator during CPB cooling should not exceed 10°C to avoid generation of gaseous emboli.
Peak warming temperature gradient and rewarming rate	–Temperature gradients from the arterial outlet and venous inflow on the oxygenator during CPB rewarming should not exceed 10°C to avoid outgassing when warm blood is returned to the patient.
Rewarming when arterial blood outlet temperature is ≥30°C	–To achieve the desired temperature for separation from bypass, it is reasonable to maintain a temperature gradient between arterial outlet temperature and venous inflow of ≤4°C –To achieve the desired temperature of separation from bypass, it is reasonable to maintain a rewarming rate of ≤0.5°C min−1.
Rewarming when arterial blood outlet temperature is <30°C	–To achieve the desired temperature for separation from bypass, it is reasonable to maintain a maximal gradient of 10°C between arterial outlet temperature and venous inflow.

Blood management and tranexamic acid

Bleeding after cardiac surgery is a common complication, with a very significant impact. Rates of resternotomy vary between 0.69% and 7.6% in different units, but the impact is significant; the mortality rate is 15% after resternotomy and so it is of paramount importance to reduce the risk of postoperative bleeding.¹⁶ Intraoperative tranexamic acid reduces the need for blood transfusion, major haemorrhage or tamponade requiring reoperation.¹⁷ A maximum total dose of 100 mg kg⁻¹ is recommended as higher dosages are associated with seizures. Reducing perioperative red blood cell transfusion involves correction and optimisation of haemoglobin before surgery, intraoperative blood scavenging and avoiding postoperative hypothermia. The use of data-driven transfusion algorithms supported by comprehensive point-of-care coagulation testing can guide transfusion choices and reduce the use of blood products.¹⁸ The effect of CPB on platelet function may make the use of a higher platelet count (>750,000 L⁻¹) necessary after bypass.¹⁹

A reduction in bleeding in the immediate postoperative phase is crucial in meeting the ERAS goals of early tracheal extubation, mobilisation and restarting oral diet.

Postoperative care

Multimodal, opioid-sparing analgesia

Adequate analgesia is key and needs to be considered before, during and after surgery. Pain has undesirable physiological effects including sympathetic nervous system activation, increased inflammation, immune suppression and impaired gastrointestinal function. Optimal analgesia is an important component of ERAS as it facilitates early extubation, mobilisation and recovery. Multimodal opioid-sparing approaches can provide the desired balance of adequate analgesia while minimising the known detrimental adverse effects of opioids such as sedation, respiratory depression, nausea, vomiting and ileus.

Multimodal opioid-sparing analgesics for cardiac surgery can be divided into pharmacological (e.g. magnesium sulfate, gabapentinoids, paracetamol, dexmedetomidine, ketamine), local anaesthetic (LA) infiltration over the sternal wound and drain sites, and regional anaesthetic techniques (epidural, paravertebral, erector spinae or parasternal blocks).

Magnesium sulfate is commonly used in cardiac surgery as prophylaxis for arrhythmias. Higher doses (50 mg kg⁻¹ i.v.) help to reduce opioid requirements and pain scores. The analgesic properties of magnesium are probably related to N-methyl-d-aspartate (NMDA) antagonism, leading to inhibition of calcium influx and attenuation of central sensitisation in the dorsal horn of the spinal cord.²⁰

Gabapentinoids (pregabalin and gabapentin) are often included in ERAS protocols. Their use may reduce postoperative pain scores, opioid requirements and related adverse effects, although most ERAS protocols use doses below those in the literature shown to reduce opioid requirements significantly.²¹

Dexmedetomidine acts on presynaptic α₂ adrenergic receptors to inhibit the release of noradrenaline (norepinephrine), which in turn induces hyperpolarisation and inhibits the propagation of pain signals to the brain. It also acts on postsynaptic α₂ receptors to decrease sympathetic activity and causes dose-dependent inhibition of peripheral C- and α pain fibres. Dexmedetomidine has been used as premedication, analgesic, adjuvant analgesic and sedative, although data in cardiac surgery are limited. Potential adverse effects such as hypotension and bradycardia may occur.

Regional anaesthetic techniques such as thoracic epidural anaesthesia (TEA) and paravertebral block have all been safely used for cardiac surgery despite the potential hazards of using these techniques shortly before a full anticoagulant dose of heparin. In practice the time taken for TEA and management of inadvertent venous puncture, a ‘bloody tap’, at the start of surgery have precluded its widespread use. Infusion of LA via a wound catheter or by simple infiltration at the wound edges by the surgeon has a surprisingly large impact on postoperative pain.²²

Non-steroidal anti-inflammatory drugs are associated with renal dysfunction and thromboembolic events after cardiac surgery, and are best avoided.

Although not widely practiced in the UK, rigid sternal fixation may have a place in reducing pain, improving mobility and quality of life. The evidence for this is currently weak, but it may be beneficial in patients with risk factors for poor wound healing or with a high BMI.

Preoperative counselling to establish appropriate expectations of perioperative analgesia targets and use of pain observation tools in intubated and awake patients have a role in minimising opioid use.

Postoperative nausea and vomiting prophylaxis

Postoperative nausea and vomiting (PONV) is frequently listed by patients as contributing to a negative experience. It also increases adrenergic stimulation, limits mobilisation and slows the progression of oral intake and diet. Published rates of PONV in cardiac surgery are as high as 67%.²³

Tracheal extubation

Prolonged postoperative ventilation is associated with increased morbidity, mortality and prolonged stays in ICU and hospital.²⁴ Timely tracheal extubation has been an important element of cardiac surgery quality improvement initiatives since the earliest ‘fast-track’ protocols. Although prolonged mechanical ventilation (defined as >24 h) is the current STS quality metric, early extubation (defined as <6 h) is a generally agreed goal for postoperative care and has been endorsed as a key benchmark in the ERAS Cardiac Guidelines.²⁵ Early extubation without achieving differences in other outcomes such as ICU or hospital length of stay shows that the benefits of early extubation alone may be limited.²⁶ However, a comprehensive strategy of optimisation with a goal of facilitating early extubation has demonstrable positive effects when implemented consistently.²⁷ Extubation, a simple act for most anaesthetists, is in fact made up of several overlapping factors related to the patient, the healthcare providers and the hospital system. It is likely that the processes of optimising the patient for extubation are more important than its exact timing.

Active, planned mobilisation

Early mobilisation after surgery helps to reduce pulmonary and thromboembolic complications and to prevent deconditioning.²⁸ Patients should be assessed by a physiotherapist after extubation and start therapy as soon as possible. The target should be to sit up on the bed within 4 h of extubation and start deep breathing exercises.

After cardiac surgery patients are hypercoagulable and at risk of thromboembolism. Along with early mobilisation, chemical thromboprophylaxis should be considered when their chest tube drains are absent or the drains are removed.

Perioperative glycaemic control

Hyperglycaemia leads to glucose toxicity, greater oxidative stress, a prothrombotic state and increased inflammation. Interventions to improve glycaemic control have been shown to improve outcomes.²⁹ Hyperglycaemia (glucose >8.8–9.9 mmol L⁻¹) should be managed with a titrated infusion of insulin; however, care must be taken to also avoid hypoglycaemic events.

Managing temperature

Postoperative hypothermia is the failure to return to, or to maintain, normothermia (>36°C) 2–5 h after admission to ICU. Postoperative hypothermia is associated with increased bleeding, infection, prolonged hospital stays and death. In addition to ensuring adequate rewarming before separating from CPB, use of forced air warming blankets, fluid warmers, and raised room ambient temperature should all be considered.

Screening for delirium

Delirium is defined as a disturbance of consciousness and a change in cognition that develops over a short period of time. Approximately 50% of patients after cardiac surgery develop delirium, which can be hyperactive, hypoactive or mixed psychomotor behaviours. Delirium is associated with decreased survival, in both the short and long term. In addition, it also leads to more hospital readmissions and diminished recovery of cognition and normal function. A systematic delirium screening tool such as the Confusion Assessment Method for Intensive Care Unit (CAM-ICU) or the Intensive Care Delirium Screening Checklist (ICDSC) should be used at least once during each nursing shift to identify delirium in a timely fashion. A management plan should include assessment of risk factors (patient, critical illness and iatrogenic), screening and treatment. Techniques such as sedation holds, orientation, correction of the sleep–wake cycle and using visual and hearing aids should be used before starting drug treatments. The goal of an ERAS programme should be to minimise delirium and enable progression with postoperative nutrition, mobilisation and recovery.

Removing drains and catheters early

ERAS programmes in other surgical specialities have moved towards using no surgical drains or advocated the early removal of drains and catheters. Immediately after cardiac surgery most patients have some intrathoracic bleeding, which needs to be evacuated via chest drains, and arterial and central venous catheters are considered a minimum standard of care. Chest tubes are prone to obstruction by clots leading to retained mediastinal blood, compression of the heart or lungs and potentially requiring a return to the operating theatre. Even small volumes of retained mediastinal blood can promote a pro-inflammatory state, which may result in pleural/pericardial effusions or postoperative atrial fibrillation. Finally, retained mediastinal blood has been previously linked to greater transfusion requirements, rates of AKI, duration of mechanical ventilation, length of stay and mortality. The common practice of milking or stripping tubes is unlikely to be effective, and is potentially harmful. Active chest tube clearance methods prevent occlusion without breaking the sterile field, thereby maintaining inner lumen patency and reducing the volume of retained blood.

Chest tubes and invasive lines should be removed as soon as they are not required, according to clear protocols. Chest drains can be safely removed once drainage is determined to be serous on visual inspection.

Goal-directed therapy

Goal-directed therapy (GDT) is an algorithmic approach to optimise a patient's cardiovascular physiology, using the comprehensive application of dynamic responsive monitors. Although the exact monitors, decision pathways and interventions may differ, meta-analysis of the data on the standardised application of GDT protocols for cardiac surgery has shown a reduction in hospital length of stay and complications, but not ICU length of stay or mortality.³⁰ Subgroup analysis has shown that initiation in the operating room (with continuation to the ICU) confers no additional benefit to a protocol applied solely on arrival in the ICU.³¹ This suggests that a GDT strategy might only achieve maximum benefit if it includes a postoperative ICU phase, which is in contrast to the majority of GDT literature in non-cardiac surgery. The next progressin GDT for cardiac surgery may be within CPB techniques, where early data are promising. Ongoing research should help determine the most useful and cost-effective monitoring strategy and GDT intervention bundles, but the current evidence suggests the benefits of GDT warrant their inclusion in cardiac surgery ERAS pathways.

AKI

Acute kidney injury contributes to morbidity and mortality after cardiac surgery. Urinary biomarkers, such as tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7), can identify patients at risk for developing renal injury before increases in serum creatinine or reduced urine output.³² Activating a renal-protection and haemodynamic optimisation bundle based on the detection of urinary biomarkers has been shown to reduce the incidence of AKI after cardiac surgery.³³

Conclusions

The development of ERAS programmes for cardiac surgery draws on advances made in other surgical specialities to reduce surgical trauma, improve patients' experience and lead to a more rapid recovery. This is a team-based approach that puts patient at the centre of care and focuses on the entire perioperative period. Transition from existing care to a bundle of enhanced recovery interventions is not straightforward and relies upon good communication with patients from the point of referral. The interventions are simple but require the support from all disciplines involved to maximise the benefits.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Declaration of interests

The authors declare that they have no conflicts of interest.

Biographies

Savin Pokhrel FRCA is a speciality trainee in anaesthesia at James Cook University Hospital, Middlesbrough who has completed a fellowship in cardiac enhanced recovery.

Adrian Mellor MD FRCA is a consultant cardiothoracic anaesthetist at James Cook University Hospital. He is a visiting professor at Leeds Beckett University, has given invited lectures on ERAS and has instituted a cardiac ERAS programme.

Alexander Gregory MD FRCPC is a cardiac anaesthesiologist and assistant professor in the Department of Anesthesiology, Perioperative and Pain Medicine at the Cumming School of Medicine, University of Calgary and a member of the Libin Cardiovascular Institute. He is an Executive Board member of the ERAS Cardiac Society and has published articles and given invited lectures on enhanced recovery for cardiac surgery.

Matrix codes: 1A01, 2A07, 3G00