This article reviews the evolution of current evidence on fast track cardiac recovery management in cardiac surgery, and particularly in minimally invasive and transcatheter aortic valve surgical procedure. The background of fast track cardiac surgery management and recovery in the 1990' with balanced anesthesia technique and early tracheal extubation is described. The safety, efficacy and cost benefits of fast track cardiac recovery are presented. The risk assessment of patients with severe aortic valve disease for minimally invasive or transcatheter surgical procedure is reviewed. The process of postoperative care together with the intraoperative anesthetic management is highlighted.
The use of a balanced anaesthetic for cardiac surgery was introduced in the early 1980’s and followed closely on the heels of the reintroduction of inhalational anaesthesia as a viable alternative to narcotics in patients with coronary artery disease.1,2 Two ideas developed along in parallel for cardiac surgery that: (1) Lower dose narcotics with the addition of inhalational or iv amnestic still provided a hemodynamically stable patient, and (2) A beneficial effect of lower narcotic doses was the ability to extubate patients earlier than was previously possible. The concept was not adopted widely and another 10 years would pass before a series of articles examined the role of fast track cardiac surgery management and recovery. Cheng et al.3 first demonstrated the safety and efficacy of balanced anaesthesia for early extubation as well as resource reduction post cardiac surgery.4,5 Further, one-year follow up study reaffirmed the long term improved morbidity outcomes and cost benefits in fast track cardiac management and recovery.6 Fast track as currently envisioned employs both aspects of care, however, the definition of early extubation has been variable and certainly in the initial reports early extubation could better be termed earlier extubation and ranged anywhere from 4 h to within 24 h post-operatively.7
The primary driver behind the change was cost and resource restrictions that became increasingly more constrained in the 1990’s while at the same time the demand for health care resources exploded. Many of the early work on fast track cardiac care where unable to show actual reductions in intensive care unit (ICU) length of stay primarily because care pathways that were well established in these institutions were difficult to modify. The entire process of care during surgery (to avoid factors which may delay extubation such as bleeding), during anaesthesia, and the process of care following surgery in the ICU (the ability to transfer patients early in the care pathway to step down units) must be addressed.8 It became evident that several potentially care pathways were available, including modifications to nursing coverage in an ICU, creating a step down unit separate from the ICU, or bypassing critical care altogether (the so called ultra-fast track model). Without fully implanting changes to the pathways or model of care it was evident the potential cost savings from fast track recovery could not be fully realized.9
Process of care
Early work on fast track cardiac recovery (FTCR) failed to produce the anticipated reductions in length of stay in the ICU, despite the fact that patients’ duration of intubation was reduced. Cheng et al.3,4 used the outcome of fit to discharge in an effort to distinguish the FTCR group from the control group and were indeed able to show reductions in ‘length of stay’. However, as patients were unlikely to be discharged in the evening or overnight, actual stays in the ICU were similar between groups. In effect, only one step in the process of care had changed (lower narcotic utilization permitting earlier extubation). This led to the concept of changing the entire process of care from the time the patient left the operating room. Again, Cheng8 proposed two possible pathways for FTCR which would decrease the length of stay in the ICU (Figure 1). The first utilizes a cardiac recovery unit that is separate and distinct from the ICU, the parallel model, allowing cardiac patients to transfer directly out of the cardiac recovery unit bypassing ICU entirely. Some models will transfer patients to ICU if extubation does not occur in a specified time period while other models have the cardiac recovery area function as an entirely separate and inclusive ICU. The second model or integrated unit, maintains patients in the same physical space but downgrade the care they received appropriate to their level of illness, with the potential of increasing the nurse patient ratio, as this is a strong driver of cost and frequently a limitation on resource use. The final option is to bypass ICU completely the ultrafast track approach.
Given the expanded role of procedures which permit ultrafast track recovery, utilizing sedation, or general anaesthesia with extubation in the operating room, the potential to bypass the intensive care unit becomes feasible. Frequently this means the use of the post-anaesthetic care unit (PACU), with the process being transfer to the general ward if the patient meets discharge criteria, or transferring to the ICU if they fail. This pathway is becoming more common and more feasible as the number of cardiac patients receiving sedation or ultrafast track surgery increases. The main limitation is maintaining sufficient volumes to maintenance of skills within the recovery room nursing population. An alternate model is to utilize the ICU coronary care unit instead of the post-operative recovery area with the intention of discharging the patients to the ward 2–3 h after surgery. This care pathway is frequently utilized in transfemoral transcatheter aortic valve implant (TAVI) cases as the use of sedation becomes more prevalent making the need for post-operative ventilation mute.
Fast track cardiac recovery: the evidence
Fast track cardiac recovery for cardiac surgery
Over the last 10 years there have been several meta-analyses reporting on the outcomes following fast track cardiac recovery vs. conventional therapy. Many trials by design have either looked at using a low dose opioid solely (without changing per se the process of recovery) or use of a fast track recovery model (which by design necessitates either a low dose narcotic approach or the use of ultra-short acting narcotics like remifentanil). The most recent meta-analysis in 2016 by Wong et al.10 as part of the Cochrane database of systematic reviews reviewed a total of 28 trials involving 4438 patients spanning the years 1989–2015. The vast majority of trials were relative healthy patients coming for first time cardiac surgery. Many trials included only coronary artery bypass surgery. Figures 2 and 3 denoted no differences in the risks of adverse events when comparing low dose to regular dose narcotic and early extubation vs. routine care.
For favourable outcomes, for which fast track recovery was implemented to improve, specifically reductions in ICU length of stay and hospital length of stay the results are mixed. The fast track trials, both lower opioid dosing and early extubation, were able to demonstrate reductions in duration of intubation from a mean difference of 7.4 h for low dose opioid and 6.25 h for early extubation For duration of ICU stay mean differences were 3.7 h for low dose opioid to 7.16 h for early extubation, all differences were statistically significant. However, most trials were unable to show an impact on overall hospital length of stay. When trials were combined in the meta-analysis no impact on Hospital length of stay was discernable. All favourable outcomes, duration of ventilation and ICU length of stay, had high heterogeneity as measured by the I2 statistic, which suggests a broad range of outcomes across different studies. This likely represents an expectation that a change in anaesthesia practice alone would have a large impact on patient outcomes while not focusing on the entire process of care, which includes changing the model of recovery as well as the expectations for recovery amongst the patient, patient’s family and care providers.
Fast track aortic valve surgery
Most randomized trials on Fast track cardiac recovery tend to enrol lower risk patients undergoing CABG procedures and few studies have examined the use of rapid recovery of patients undergoing aortic valve surgery in particular. Conventional aortic surgery is by nature an open procedure, requires cross clamping of the aorta, may result in debris from the valve being reintroduced into the blood stream, and may compromise coronary perfusion to a greater degree than CABG surgery. It results in a large aortotomy with a potentially greater risk of bleeding. All of these factors may have a negative impact on fast track recovery.
There is one report of ultrafast track recovery of patients following simple or combined aortic valve replacement surgery using rapid recovery with opioids or thoracic epidural anesthesia.11 Unfortunately, the trial is small, having enrolled only 45 patients. They reported 100% success with rapid extubation (within 15 min) in the operating room and no reintubations were required. This suggests that rapid recovery of conventional aortic valve replacements is possible however, given the small size, patient selection likely play a role in the success of this technique.
Fast track aortic valve surgery minimally invasive approach
The use of a limited sternal incision to perform conventional aortic valve replacement (AVR) is becoming more common and theoretically has the advantages of reductions in bleeding and transfusion requirements. Instead of splitting the sternum completely down the midline the sternum is transected at the midline up to the 4th or 5th rib space then the incision is brought off to the side, the ‘J’ incision, or a parasternal, or thoracic approach is employed. Few trials make direct comparisons to the conventional AVR with full sternotomy. Neely et al.12 reported on a propensity matched outcome of conventional AVR vs hemi-sternotomy and demonstrated reduced ventilation times from 6.3 to 5.7 h. These findings were similar to Ghant et al.13 which reported in approximately 1300 patients from 17 centres and also demonstrated shorter length of ventilation times with minimally invasive AVR (5 vs. 6 h). Several other studies have also shown consistently shorter intubation times with a minimally invasive approach to aortic valve replacement compared with conventional AVR.14,15 Taken together these studies suggest that the use of a minimally invasive incisions for aortic valve surgery can reduce the duration of ventilation in the ICU and thus promote fast track management of these patients.
Rapidly deployable aortic valve replacement
The use of rapidly deployable aortic valves (RDV) have recently grown in popularity and employ a design similar to a TAVI valves using a surgical approach similar to conventional surgery. The benefit of such valve is they require a reduced number of sutures, typically using the radial force of the supporting structure to provide the seal to the aortic annulus. As such they typically require less surgical time and thus less bypass time. The benefit of the valves themselves are complicated by the frequent use of a minimally invasive surgical approach which itself seems to, as noted above, reduce ventilation and ICU times and thus support a fast track recovery approach. However, some studies do suggest the reduced surgical times a RDV themselves may also reduce recovery times. A recent review by Davies et al.16 presents a comprehensive narrative review of RDV. Although most studies were in observational nature, most demonstrated reductions in ventilation time, and slight reductions in ICU length of stay (most not being statistically significant). This suggests that RDV may reduce resource utilization following AVR and that patients who have undergone RDV insertion may be appropriate candidates for fast track recovery.
Fast track trans-apical TAVI
Trans-apical TAVI is performed through a small thoracotomy usually located in the mid-axillary line over the 5th or 6th intercostal space. Unlike transfemoral TAVI which utilizes the transapical approach requires general anaesthesia and so is potentially amenable to a fast track approach. The literature seems to suggest such an approach is feasible Walter et al in their series of 49 patients showed a median time to extubation of 6 h, a 62.7% success rate of same day extubation, with a median ICU length of stay of 20 h.17 The Logistic EuroScore in this subset of patients was 26.8%. A systematic review of transapical TAVI published in 2012 found only about half of reported series gave data about ICU length of stay which ranged from 1 to 7 days (mean) which suggested that fast track for transapical TAVI appears feasible but may not be widely practiced.18 A more recent report, on the second generation TAVI valves, suggest LOS in the ICU or intermediate care ward following either TA or TF TAVI was a mean of 5.3 days.19 This seems to suggest that patient factors more than the approach per se may be the biggest factor in the duration of ICU stay following the TAVI approach. Extubation in the OR following transapical procedures is entirely feasible although few trials have reported on this approach. Finally, conscious sedation is possible for transapical aortic valve replacement using a thoracic epidural for anaesthesia. The registry report for second generation valves also reported a 1.3% rate of local/regional/conscious sedation for the transapical approach.19
In general, the above evidence tends to be weak relying on retrospective observational data, which is matched to conventional patients. This suggests that there is potential for bias in the reported times for length of ventilation and length of ICU stay. In addition, many trials failed to report on the duration of ventilation, length of ICU stay or length of hospital stay. Likely reflecting that many of these approaches are fairly novel and/or new technologies which rightly need to demonstrate efficacy in clinical outcomes before examining the resource utilization issues. Despite these limitations, in general the data supports reductions in durations of intubation and ICU length of stay which supports the idea that as these techniques develop a fast track approach may become feasible in an increasing proportion of patients undergoing AVR, and indeed and ultra-fast track approach may become more common.
Risk factors for fast track failure
There have been numerous attempts to identify the causes of failure to rapidly wean and extubate patients. The goal behind these studies is to try to identify modifiable factors which the anaesthesiologist can attend to and thus reduce the overall failure rate. An early article by Wong et al.20 demonstrated that in patients undergoing CABG surgery, increased age, female gender, post-operative use of intra-aortic balloon pump, inotropes, bleeding, and atrial arrhythmia were risk factors associated with failure to extubate within 10 h of ICU admission. This occurred in approximately 25% of the 885 patients studied. Xu et al.21 studied patients undergoing valve surgery and demonstrated that older age, poor left ventricular ejection fraction, previous cardiac surgery and repeat cardiopulmonary bypass (CPB) during surgery were risk factor for prolonged length of stay in the ICU, although the length of intubation was not analysed in their model. Torman et al.22 also examined risk factors for fast track recovery in non-coronary bypass cardiac surgical patients. They found the risks for delayed extubation included congestive heart failure and peripheral vascular disease. While factors that led to prolonged ICU stay included diabetes, emergency operation, red blood cell transfusion and increased chest tube drainage. They extubated 72% of patients within 6 h, and had an 87% discharge rate from the ICU within 24 h. Most of the above studies are small, and therefore did not identify all the factors related to delayed fast track recovery. Most of the above studies are small, and therefore did not identify all the factors related to delayed fast track recovery. A large prospective study by Constantinides et al.23 looked at the risks for fast track failure in a group of 1084 patients. They used a broader definition of fast track failure including death within 30 days, > 48 h in their step down unit, admission to the ICU during the hospital stay. This definition represents a broader more inclusive definition of fast track failure which maybe directly related to fast track management but would also include other patient specific factors. Overall the fast track failure rate was 11%. Factors associated with fast track failure included: impaired left ventricular function re-do operation, extracardiac arteriopathy, preoperative intra-aortic balloon pump, raised serum creatinine and non-elective or complex surgery. The factors identified were subsequently validated in a lager study by Lee et al.24 who examined 1597 patients undergoing fast track management. They were able to show similar results with a failure rate of 11% for fast track management. Unfortunately, most factors associated with fast track failure are not modifiable however, bleeding or need for transfusion is a common theme through-out many studies suggesting that close attention be paid to haemostasis before during and after the procedure.
There is strong evidence that fast track cardiac management with early extubation anaesthesia care is safe, efficacy, and cost beneficial as the standard of cardiac anaesthesia and surgery care in both coronary and valvular patients. As the advancement in cardiac surgery is evolving to incorporate shorter CPB times and less invasive procedures, the number of patients suitable for and will be successful in a fast or ultra-fast track recovery model will grow. For optimal success in fast or ultra-fast track model of cardiac recovery, the most important element is to facilitate the process of post-operative care coupled with intraoperative early extubation anaesthesia.