Abstract
Background and Purpose Short-term ventricular assist device (VAD) support is used in the intensive care unit (ICU) to support individuals in end-stage heart failure prior to heart transplantation or implantation of a long-term left VAD. The literature investigating the feasibility, safety, and content of rehabilitation for this patient group is lacking. This report retrospectively describes the rehabilitation strategy, safety measures used, and nature of any adverse events and, therefore, the feasibility of this practice.
Case Series Description Ten individuals (80% male) admitted to the ICU in critical cardiogenic shock required support via a short-term VAD. A prerehabilitation risk assessment was used to reduce the risk of cannula dislodgement. The therapeutic strategy was a stepwise progression of exercises, mobilization, and ambulation.
Outcomes Retrospective inspection of the case notes showed 330 rehabilitation sessions (X̅=33, SD=18.1, range=16–72) were performed and progressed to ambulation on 71 occasions (X̅=7.1, SD=7.7, range=1–27). Distance ambulated ranged from 7 to 1,200 m (X̅=157.7, SD=367.3). The Chelsea Critical Care Physical Assessment Tool (CPAx) score for 7 patients improved from a median of 0 (interquartile range=0–1) on day 1 to a median peak score of 39 (interquartile range=37–42). There were 8 episodes of minor adverse events (2.4% incidence rate), including 7 of transient low VAD flows. There were no major adverse events.
Discussion Early rehabilitation and ambulation of recipients of short-term VAD support was safe and feasible. Recipients demonstrated improvements in physical function (CPAx score) while the VAD was in situ.
When pharmaceutical options have been exhausted in the management of end-stage heart failure, surgical implantation of a temporary extracorporeal mechanical circulatory support (MCS) device in the form of a ventricular assist device (VAD) may be necessary.1,2 Once the device is inserted, the individual must remain an inpatient, usually in an intensive care unit (ICU), as the device acts as a short-term bridge to either heart transplantation (HT) or implantation of a long-term ventricular assist device (LVAD).3 Short-term MCS use has increased in frequency and duration, as individuals with multisystem organ failure require a period of stabilization, neurological assessment, and rehabilitation prior to further surgical decision making.1,4–6 The safety and feasibility of physical therapy for this patient group has not been thoroughly evaluated in the literature. Freeman and Maley3 outlined their strategy for progressing mobilization and ambulation with recipients of a VAD but provided limited details of any safety protocol (including clotting factors) and did not document how many individuals participated or whether any adverse events occurred. Soni et al7 reported their experiences of ambulation over 5 years with 46 individuals and the occasions when mobilization was prevented due to VAD-related complications. They did not provide information on safety protocols, staffing requirements, or the nature of exercise progression.7 Neither study defined an “adverse event.” Publications detailing reproducible safety protocols, therapy strategies, or transparent data regarding adverse events are lacking. This significant gap in the literature should be considered by therapists when analyzing the risks and benefits of mobilization in this cohort.
The CentriMag ventricular assist system (Thoratec Corp, Pleasanton, California) consists of a centrifugal pump supporting the systemic circulation. Extracorporeal MCS devices such as the CentriMag provide effective hemodynamic support but carry a significant rate of complication, including bleeding, hemolysis, neurological events, and infection.5 Historically, patients were confined to bed rest to guard against incidents of bleeding or cannula dislodgement during patient mobilization. Recent developments in surgical methods of implantation and the securing of VAD cannulae have allowed the initiation of ambulatory rehabilitation.1–3,7 For physical therapists, ambulatory rehabilitation provides an opportunity to challenge the paradigm around rehabilitation during MCS. However, active rehabilitation creates additional complexity. The cannulae (4 for biventricular support) typically exit the body via central subcostal incisions. Maintenance of cannula fixation during mobilization and modification of activities to reduce strain on the cannulae are essential. Rehabilitation of this group is particularly important, as immobility can adversely affect long-term outcomes and, ultimately, cost.8 Further literature detailing the feasibility of progressive mobilization programs after VAD implantation may support therapists in embedding this strategy into their practice and, therefore, into their ICU team culture.
Individuals requiring a short-term VAD are at risk of ICU-acquired weakness due to the critical nature of their illness and the mobility restrictions placed on recipients by ICU teams cautious of the potential consequences that movement may have on the VAD (ie, dislodgement or reduced pump flows).3 The effects of prolonged bed rest, the benefits and safety of ICU rehabilitation, and early mobility are well documented.9–14 Much of the literature detailing suitable physiological parameters for rehabilitation of an individual in critical care is inapplicable to the VAD population. The parameters that define cardiovascular and respiratory stability and, therefore, suitability for rehabilitation in the general critical care population, such as heart rate, heart rhythm, and blood pressure,10,12,15 may lie outside the recognized “normal” range in the CentriMag device user population. Ventricular assist device flow rate provides a critical and more useful indicator of circulating intravascular volume and potential for orthostatic intolerance. Some individuals tolerate cardiac dysrhythmias (even ventricular fibrillation) due to the maintenance of cardiac output to both the pulmonary and systemic circulations with a biventricular VAD.16 A target heart rate range prior to and during exercise also may be irrelevant for the same reason.
The purpose of this case report is to present a case series that demonstrates the feasibility and safe use of physical therapist–led, progressive ambulatory rehabilitation for individuals requiring short-term VAD support.
Case Description: Patient History and Systems Review
All patients (N=17) requiring a Thoratec CentriMag device implantation (for cardiac support, except after HT) between November 2012 and November 2014 were identified retrospectively. Individuals over the age of 18 years who had participated in rehabilitation during CentriMag support were identified (n=12) and were approached at a follow-up clinic appointment for consent to retrospectively review their medical and therapy records. Ten patients consented to their data being used (Fig. 1). The rehabilitation strategy for this patient group was developed over several years as part of our standard clinical practice. This study, therefore, was categorized as a service evaluation by the local research and development department, and the national research ethics service and thus was exempt from any specific research ethical approval process.
Patient flowchart and surgical outcomes. VAD=ventricular assist device, HT=heart transplantation, LVAD=long-term ventricular assist device.
The 10 individuals making up the cohort of this study (Tab. 1) were referred to the cardiothoracic critical care unit (CTCCU) of a large UK tertiary referral teaching hospital for MCS due to critical cardiogenic shock (Interagency Registry for Mechanically Assisted Circulatory Support [INTERMACS] profile 1 or 2).17 The mean time of VAD support was 40.7 days (SD=17.8, range=11–68). Six patients were bridged to HT, and 4 patients received an implantable long-term LVAD (Fig. 1).
Patient Demographics (N=10)a
The rehabilitation goal for this group was to optimize physical function prior to HT or LVAD implantation. Further aims included prevention of muscle atrophy and pulmonary complications and engaging individuals in meaningful tasks and activities to improve their mood.
Clinical Impression 1
Individuals were deemed suitable for active rehabilitation by meeting the following inclusion criteria (based on the consensus opinion of the multidisciplinary team [MDT]): sternum surgically wired closed, cannulae surgically secured4,16 with confirmation from the surgeon,* patient conscious and able to consent to rehabilitation, and MDT agreement of a patient's suitability for rehabilitation.
Individuals with any of the following criteria were excluded due to their inability to actively participate or their cardiovascular instability: ongoing extracorporeal membrane oxygenation (ECMO) support, multi-organ failure unresponsive to medical therapy, and ongoing sedation.
Examination
A risk assessment was introduced to ensure suitability for the rehabilitation intervention and was performed by one of the team's senior physical therapists prior to every mobilization activity4 (Appendix). A structured procedure was followed to minimize the risk of cannula dislodgement during interventions (Fig. 2). The safety precautions were based on previous clinical experiences, liaison with perfusionists and specialist physical therapists working at the other UK transplant/VAD centers, and the limited studies published to date.3,4,16 The literature on ICU rehabilitation in populations without MCS also was consulted.9,10,12,15 The risk assessment ensured that each individual demonstrated: hemodynamic stability, defined in this context as stable mean arterial pressure and no acute onset cardiac arrhythmia; stable CentriMag flow rates, defined as no unexplained drop in flow >0.5 L/min or alarms within an hour of treatment (agreed on and defined locally for the purpose of consistency in clinical reasoning); firmly secured VAD cannulae (using Hollister clips), with no indication of infection or oozing; stability in clotting parameters, with mobilization not performed if the activated partial thromboplastin time ratio was ≥3.0 or the activated clotting time was ≥240 seconds (based on unit anticoagulation protocol and consensus opinion of MDT); and the ability to follow instructions (ie, no obvious confusion or agitation).4
Risk assessment procedural flowchart—physical therapy mobilization of recipients of short-term mechanical circulatory support. VAD=ventricular assist device, MDT=multidisciplinary team, ACT=activated clotting time, APTT=activated partial thromboplastin time, IVs=intravenous injections.
Clinical Impression 2
Each patient received a daily physical therapy review while the VAD was in situ. The examination prior to each rehabilitation session demonstrated that each individual was stable from a cardiorespiratory perspective. The risk assessment procedure (Fig. 2) highlighted 32 occasions on which mobilization was inappropriate and, therefore, withheld. The VAD-related factors were: low flow alarms (3), insecure cannulae (2), oozing cannulae (12), cannulae requiring resuturing (3), and one occasion of a large visible thrombus within the cannulae. The non–VAD-related factors that prevented mobilization were: inability to follow instructions (4), insufficient staff (1), deranged clotting factors (1), bleeding at a tracheotomy site (2), and a new cardiac arrhythmia (3).
Response to the rehabilitation intervention was assessed using the Chelsea Critical Care Physical Assessment Tool (CPAx).18–20 Ten commonly evaluated measures of physical function generate a score of 0 to 5 on a Guttman scale (eAppendix). These scores combined produced a total score out of 50, which was calculated on admission and twice weekly thereafter. A score of 0 represents an individual receiving sedation and mechanical ventilation. A score of 50 represents a self-ventilating individual who requires no additional oxygen and is fully mobile and independent in all transfers. The CPAx was only introduced into our routine clinical practice at a time that captured data for the last 7 individuals of this study. Data also were collected detailing the number and content of rehabilitation sessions and distance of ambulation. Progression of physical function was observed in the increase of the CPAx score and a greater distance ambulated.
Records were examined for any adverse events during rehabilitation. Adverse events were categorized as significant (serious incident involving harm to the patient, such as cannula dislodgement) or minor (incident or change in VAD flows resolving easily and causing no harm to the patient).
Intervention
All of the patients were cared for in the CTCCU by the same clinical MDT. Transthoracic echocardiograms were performed postoperatively to confirm cannula position, ventricular filling, and ejection and to identify whether any thrombus was present prior to commencing rehabilitation.4
Physical Therapy Personnel
All physical therapists responsible for performing the rehabilitation program had attended an educational session detailing the theory of the CentriMag device and emergency protocols. When therapy involved mobilization out of bed, at least one senior physical therapist was present.
Staffing Requirements
When mobilizing an individual for the first time, a minimum of 4 staff members were present. On subsequent transfers out of bed, at least 3 staff members were available. The VAD cannulae were supported by a staff member at all times, and the patient was closely monitored for any signs of dizziness, excessive dyspnea, fatigue, or fall in VAD flow rates, in which case they were returned to their chair or bed, and their legs were elevated if required. When ambulating away from the bed space, a chair was wheeled behind the patient.
Therapeutic Strategy
Although initially unable to engage in active rehabilitation (ie, while sedated or receiving ECMO support), each patient received a daily physical therapy assessment and passive limb movements or stretches. The details of this period are not included in this report.
Once a patient was able to consent to active rehabilitation, the therapeutic aims were to complete a stepwise progression of exercises and mobilization to improve strength and functional capacity. Further aims included improving exercise tolerance and independence in activities of daily living.4,16 The term “mobilization” refers to therapeutic moving of an individual from a static supine position in a bed or chair.15 This intervention included rolling, sitting on the edge of the bed, hoisting out of bed, standing, walking in place, step-ups, stepping around an obstacle to a chair, and ambulation away from the bed area. In addition, each patient was prescribed a bed or chair exercise program. Equipment included pedals (for cycling while seated in a chair), ankle weights, dumbbells, handgrip exercisers, and an exercise bike.
Every patient had an individualized plan to progress through “phases” of rehabilitation of increasing intensity similar to those described in the ICU rehabilitation literature.12,21,22 The rehabilitation plan was tailored to each patient's requirements, so a standardized algorithm for exercise progression was avoided. Content and progression were based on the ongoing assessment of each patient's specific impairments and guided by the therapists' training, experience, and knowledge of the principles of training.3,10,23
Outcome
Rehabilitation was performed on 330 occasions (X̅=33, SD=18.1, range=16–72). All patients performed limb exercises. Rehabilitation progressed to include reeducation of sitting balance and ceiling track hoist or standing transfers out of bed. Standing practice was undertaken by all patients with physical assistance, a walking aid, or ReTurn 7500 transfer aid (Handicare Group, Kista, Sweden) on 37 occasions. Six individuals completed weight-bearing exercises, such as squats or heel-raises, on 13 occasions. All patients began work on walking by stepping or marching in place on a total of 38 occasions. All patients performed ambulation out of the bed space (71 occasions). The distance walked ranged from 7 to 1,200 m (X̅=157.7, SD=367.7). Cycling activities also were progressed from a bed bike to chair-based pedals to an upright exercise bike. The most capable patient also completed step-ups on 2 occasions (see Tab. 2 and Fig. 3 for all data).
Data Related to Rehabilitation Activities
Rehabilitation activities undertaken during mechanical circulatory support: mean (SD) number of times each activity was performed.
Chelsea Critical Care Physical Assessment Tool scores after commencing MCS were obtained for the most recent 7 patients. The median CPAx score was 0 on day 1 (interquartile range [IQR]=0–1). The peak CPAx score was the highest score achieved by each patient, with the median score being 39 (IQR=37–42) (Fig. 4).
Individual domain median scores and median cumulative peak Chelsea Critical Care Physical Assessment Tool (CPAx) scores on ventricular assist device support. © Copyright of Chelsea and Westminster Hospital. Reprinted with permission.
In 330 rehabilitation sessions, there were no significant adverse events. There were 8 minor adverse events (2.4%). Those related to the VAD were 7 episodes (2.1%) of a transient drop in flow rate (>0.5 L/min), all of which resolved with adjusting the position of the patient (5 occasions) or the administration of intravascular fluids (2 occasions). These events occurred while using seated pedals (1 occasion), standing up (3), or sitting on the edge of a bed (1) or after sitting or lying down (2). One patient reported dizziness on standing and transferring out of bed to a chair. This patient's dizziness was not accompanied by a change in mean arterial pressure or VAD flow rates and resolved on sitting.
Despite the lack of cannula-related adverse events during physical therapy, there were some cannula issues with this patient group. Surgical intervention was required for one patient, and a cannula site bleed was discovered at the time of transplant for a second patient. As individuals were free to move around independently in their bed or chair and were mobilized in and out of bed by nursing staff throughout the day, it is impossible to know whether any specific physical therapy interventions had a detrimental influence on the cannula position. The data in this case report relied on an ongoing thorough examination of each patient with corresponding accurate documentation. However, cannula issues may have not been apparent at the time of treatment, which may have led to an under-reporting of adverse events.
Discussion
The aims of reviewing the data were to detail the rate of adverse events and to examine the feasibility of ambulatory rehabilitation for this expanding patient group. A physical therapy program of structured rehabilitation incorporating mobilization and ambulation has been shown to contribute to improved outcomes in general ICU populations.10,21,24,25 The therapy team for this study consisted of a small, highly specialized subteam with responsibility for rehabilitation of the VAD and transplant population only. The structure and function of this team are comparable to those in the study by McWilliams et al,21 who initiated a small dedicated rehabilitation subteam in their mixed population ICU. They demonstrated significant improvements in mobility at ICU discharge, time taken to mobilize, ICU length of stay, and days ventilated. The before-after model of their data collection and the lack of therapist blinding, however, may have led to a measurement bias. The literature on rehabilitation in the ICU identifies screening measures for suitability for rehabilitation, and it has been shown that these guidelines facilitate rehabilitation, with a low rate of adverse events.9,10,15,23
There were no major adverse events during the rehabilitation of this group, which is supported by international VAD literature that also reports an absence of major adverse events where rehabilitation has allowed mobilization out of bed and ambulation in both adults7,8,26 and children.27 These reports, however, are limited in their detail of safety protocols and exercise progression strategies. Adverse events were briefly described by Soni et al7 and were similar to those in our case series. Soni et al7 reported 4 incidences of VAD flow decline during patient mobilization, but the total number of mobility sessions is unknown, so we cannot compare their low flow incidence rate with that of our case series.
Despite low native cardiac output or ongoing cardiac dysrhythmias, the 10 patients all performed progressive exercise programs. They demonstrated improvements in the time spent exercising and the distance ambulated. It can be argued that this patient group may tolerate physical exertion better than their non-VAD counterparts, as they have a sustained and adequate cardiac output maintained by the CentriMag pumps.16
Rehabilitation assisted all 10 individuals to increase their physical function and independence. All patients began their ICU stay as patients who were critically unwell and requiring emergency care, as demonstrated by a median CPAx score of 0 on admission (IQR=0–1) for the most recent 7 patients. After a period of medical stabilization (including VAD support) and then rehabilitation, all patients were free from mechanical ventilation and able to participate in daily exercise including ambulation. The 7 peak CPAx scores obtained produced a median score of 39 (IQR=37–42), which demonstrates a significant increase in physical function.
The CPAx is a detailed tool that is easily applied to this population. It was developed and is used widely by ICU physical therapists in the United Kingdom to monitor functional recovery from critical illness. Although the CPAx outcome measure has not been validated in the MCS patient population it has been shown to have good face and construct validity in a mixed ICU population that included patients with diagnoses of cardiac arrest and chronic cardiovascular disease,20 similar to the patients described in our case report. The CPAx tool has demonstrated good interrater reliability in a group of specialized critical care physical therapists in a mixed-population adult ICU.18 The CPAx is a responsive tool with a limited ceiling and floor effects,20 which is important when considering the patients requiring a CentriMag VAD whose clinical condition and physical function cover a wide spectrum of abilities. The peak CPAx score will have been affected by the length of wait for a donor organ/decision to implant an LVAD. Length of stay cannot be used as a clinical outcome measure for this group, as it depends primarily on the availability of donor organs, which is outside the control of the ICU team.
It can be argued that sufficiently challenging activities can be provided at the bedside, negating the need for ambulation. We have shown, however, that it can be performed without adverse events when performing a pretreatment risk assessment. Our experience showed that ambulation acted as an excellent motivational tool, allowing individuals to visualize their achievement, and, anecdotally, we found an improvement in adherence. Early mobility has been reported to foster an increasingly positive attitude toward recovery.12 Early mobility, rehabilitation, and education of the wider team by physical therapists may lead to an increased awareness of the benefits and facilitate a necessary change in culture and MDT engagement within an ICU.3,12,21,28
The risk of moving an individual with an extracorporeal VAD should not be ignored. Rehabilitation should have the backing of the whole MDT, who must liaise closely about any cannula-related concern. Ensuring clotting parameters are in range, adequately securing each cannula prior to moving the patient, and having a chair available behind the patient at all times are simple measures that may help to reduce the risk.3 Our standard protocol was to cease mobilization with physical therapists where ongoing cannula oozing was occurring. The use of an abdominal binder (Beagle Orthopaedic, Blackburn, United Kingdom)3,4 was introduced as part of the measures to support cannula position and stability during mobilization.
The limitations of this case series include its retrospective nature. The risk of errors due to confounding and bias was higher than in a prospective study. The data were collected and recorded during routine clinical practice and were not initially intended for use in a case series report, which may have led to bias and inaccuracies. Patient selection included all consecutive cases over a 2-year period; however, only 10 patients gave consent for their data to be used, and they may not accurately represent the wider population of VAD recipients. The lack of a control group reduces the internal validity of this case report. There are no outcome measures validated for measuring physical function in this patient group. Using a test such as the Six-Minute Walk Test might have improved the validity and reliability of the data, but we do not use this test clinically due to the physical and verbal support given to the patient, the challenge of maneuvering and turning the VAD equipment alongside the patient, and the desire to discourage patients from rushing, which increases the risk of falling. Despite the limitations of this small case series, the detailed risk assessment and content of the rehabilitation program allow this practice to be reproduced by others and add to the very limited information already published about rehabilitation of individuals needing CentriMag support.
Further investigations are needed to establish whether rehabilitation while requiring a short-term VAD has any impact on outcomes after HT and LVAD implantation. Qualitative studies into the quality of life and experiences of individuals undertaking this rehabilitation may allow MDTs to further support the physical and psychological needs of this complex patient group.
Ambulatory rehabilitation for 10 individuals who were critically unwell and required VAD support resulted in positive physical outcomes and no significant adverse events in 330 episodes of rehabilitation. Rehabilitation of this critically unwell patient group may be performed safely when adhering to thorough risk-reducing measures.
Appendix.
Risk Assessment Documentationa
a UHSM=University Hospital of South Manchester, VAD=ventricular assist device, NHS=National Health Service, MDT=multidisciplinary team, pt=patient, exs=exercises. © University Hospital of South Manchester NHSFT. Reprinted with permission.
Footnotes
Both authors provided concept/idea/project design and writing. Ms McGarrigle provided data collection and analysis, project management, participants, and facilities/equipment.
Dr Caunt is a Fellow of the Higher Education Academy.
The authors thank doctors Peter Goodwin and Francis Fatoye (Manchester Metropolitan University) for their advice regarding the writing of the manuscript and the staff of the Transplant Unit and Cardiothoracic Critical Care Unit at Wythenshawe Hospital for their support during the inception and development of the mobility protocol.
↵* In the surgical cannulation technique used at the University Hospital of South Manchester NHS Foundation Trust, the short-term ventricular assist device cannulae are inserted through a purse-string suture placed on the chamber or the vessel. Both aorta and pulmonary arteries will have 2 purse-string sutures and are tightly snugged down and secured in place with a sterile bung to avoid slipping. The left ventricle apical cannula is inserted at the apex and secured with 2 purse-string sutures. The right atrial pipe is secured with 1 or 2 snuggers. All cannulae are tunneled under the chest wall prior to insertion into the heart to allow closure of the sternal wound. All pipes should then be fixed doubly to the skin at the exit site to avoid any movement. In addition, all tubing will be fixed to the skin with the Hollister adhesive dressing.
- Received December 1, 2015.
- Accepted May 25, 2016.
- © 2016 American Physical Therapy Association
References
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