Thoracic epidural anaesthesia for cardiac surgery: are we missing the point?
Anaesthetic techniques have always had to adapt to changing surgical interventions. Several developments over the last 15 yr have changed practice in cardiac surgery. First, standard access to the heart via median sternotomy can often be replaced by less invasive approaches, as used in minimally invasive direct coronary artery bypass surgery, robotic surgery, or endovascular valve surgery.1 Secondly, perioperative management strategies have adopted more ‘physiological’ techniques, such as normothermic extracorporeal circulation2 3 or blood cardioplegia.4 Thirdly, off-pump aorto-coronary bypass grafting (OPCAB) avoiding extracorporeal circulation has been shown to have the potential to decrease postoperative morbidity.5 6 The absence of extracorporeal circulation has made our anaesthetic management change rapidly towards a more balanced form of anaesthesia, as practised for other major surgery, be it major abdominal, thoracic, or vascular surgery.Have these novel changes in cardiac surgery practice been accompanied by a change in anaesthetic techniques?
Fast-track cardiac anaesthesia, meaning tracheal extubation within 8 h after cardiac surgery, has been established as routine in many centres worldwide, resulting in less resource utilization and intensive care (ICU) costs while providing the same security and safety as prolonged postoperative ventilation. In addition, several reviews have shown significant potential benefits for patient outcome.7–9 The positive effect of fast-track anaesthesia on early tracheal extubation and adequate pain management has largely been possible because of the use of short-acting anaesthetic drugs, mainly short-acting opioids, short-acting neuromuscular blocking agents, and the introduction of highly soluble volatile anaesthetic agents. Regrettably, fast-track anaesthesia has not had a major impact on postoperative outcome other than some improvement in pulmonary function. Some authors have argued that this might be due to the fact that postoperative ventilation, even for a short period, has a negative impact on postoperative outcome.10 Perhaps fast-track programmes have not used regional anaesthetic techniques to facilitate early tracheal extubation? High thoracic epidural anaesthesia (TEA) provides good haemodynamic stability throughout surgery (orthostatic hypotension after surgery does not impair patient ambulation11), superior analgesia facilitating respiratory movements, and adequate muscle tone,12 13 all necessary criteria for safe early extubation. Centres using this technique claim that immediate extubation at the end of surgery is possible.
The fundamental question is whether TEA influences patient outcome after cardiac surgery, other than early extubation. Several meta-analyses and randomized-controlled studies have demonstrated better analgesia, less pulmonary complications, better cardiac function, lower incidence of renal failure, and faster recovery compared with conventional opioid-based techniques. 10 14 15 However, some criticism has been raised as these studies have small numbers of patients and are sometimes not well controlled. In the meantime, other studies have produced negative results.16 Some concern has been expressed regarding the risk of epidural haematoma17 or abscess formation18 in this group of patients. However, it has recently19 been calculated that the risk is similar to the risk in other non-obstetric surgical procedures.
Given the positive physiological effects of TEA on cardiac, respiratory and vascular function, which have been demonstrated in animals and humans, and other advantages mentioned above, the question remains as to why the results of the clinical studies have not been consistent and are at times disappointing.
Is ultra-fast-track cardiac anaesthesia and surgery the answer?
Is it be possible that TEA has not been used to its full capacity in order to implement immediate tracheal extubation, which would then allow mobilization and earlier discharge for the patient? There is some evidence that the length of ICU stay represents a major obstacle to speeding up the recovery process after cardiac surgery. This brings us to the issue of fast-tracking with the implementation of care programmes which identify those steps necessary to accelerate resumption of daily activities.20 Maximal benefits of TEA can only be achieved when perioperative medical and surgical care principles are adjusted to the principle of fast-track surgery.21 22 Such an approach requires extensive revision of the current practice of perioperative management in cardiac surgery starting from the preoperative assessment and treatment to hospital discharge and further rehabilitation.
As the role of the anaesthetist changes from a clinician providing satisfactory surgical conditions and adequate pain control, to a perioperative physician facilitating the recovery process by minimizing side-effects and complications, it becomes necessary to verify the effectiveness of a programme with multimodal interventions through well-designed large controlled trials, and using outcome measures which are meaningful and relevant to the patient (quality of recovery, functional exercise capacity, return to normal activity).23
Perioperative management requires a continuous re-evaluation of every aspect of care and the implementation of the best evidence in our daily routine starting with optimal preoperative preparation and assessment of cardiac patients. Thus, TEA would represent an important intervention in the multimodal strategy facilitating a series of other therapeutic manoeuvres. This would not exclude the integration of alternative regional (e.g. spinal anaesthesia, paravertebral blocks24) or non-regional (e.g. short-acting opioids throughout the perioperative period) strategies. This is analogous to other fast-track programmes, for example, for colon surgery, where the positive effects of TEA and, when applicable, minimally invasive surgery, on incisional and visceral nociception, mesenteric blood flow and bowel motility, allow earlier food intake and mobilization, thus accelerating the recovery with minimal morbidity.21
Immediate extubation after cardiac surgery can be an important step along other management strategies, such as body temperature maintenance (especially in OPCAB), implementation of new myocardial protective strategies (e.g. volatile anaesthetics), the use of non-cumulative neuromuscular blocking agents, avoidance of perioperative nerve damage by using careful topical cooling strategies, appropriate glycaemic control with adequate doses of insulin, maintenance of sufficient cardiac output with good splanchnic and renal oxygenation, early removal of drains and urinary catheter, early mobilization and dietary intake, and early discharge from the ICU (Table 1). The close interaction of all members of the perioperative team, patients, surgeons, anaesthetists, intensivists, nurses, respiratory physiotherapists, nutritionists is required for the implementation of these changes. Such an approach will bring us closer to addressing other interesting and more daring questions, such as whether every cardiac surgical patient needs ICU stay or general anaesthesia.
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We have a long way to go, but we have all the necessary tools to demystify cardiac anaesthesia, TEA being probably an important trigger of a novel chain reaction.
Department of Anesthesiology Montreal General Hospital and Cardiac Surgery McGill University 1650 Cedar Avenue Montreal H3G 1B7 Canada
University of Montreal Hotel-Dieu Montreal Quebec Canada
* E-mail: thomashemmerling{at}hotmail.com
References
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