Keeping Pace with Prevention of Complications in the Cardiac Intensive Care Unit

Cardiovascular specialists have been challenged to keep pace with the advancing complexity of care in the environment of the cardiac intensive care unit (CICU), which is now marked by a pervasiveness of non-cardiovascular comorbid conditions, and multisystem organ dysfunction.^{1, 2} Outcomes in this environment are plausibly influenced as much by the complications of care that we provide as by the acute cardiovascular conditions that triage patients to the CICU. Potentially preventable complications are associated with longer ICU stays, greater consumption of healthcare resources, and greater morbidity and mortality. The American Heart Association Scientific Statement on Prevention of Complications in the Cardiac Intensive Care Unit provides a framework for practitioners in the CICU to anticipate, recognize, and mitigate the risk of complications of care that can occur in the CICU.

Perhaps, the most common phrase in the scientific statement is “there are no data specific to the CICU” to guide evidence-based practice. This repeated observation is one of the most important elements of the scientific statement and is highlighted by the writing committee as identifying key gaps in knowledge that should stimulate additional investigation to quantify the incidence of complications of CICU care, definitively determine their association with outcomes, and test the efficacy and safety of proposed interventions for their prevention. Despite these major gaps in evidence with which to define CICU-specific practices, the writing committee has rationally drawn on extensive experience in general medical and surgical ICUs to formulate a comprehensive set of suggestions for current best practices to prevent complications in the CICU. The highlights of these suggestions are summarized below.

As a dominant theme, the writing committee emphasizes that the incidence of complications related to ICU care is strongly associated with the duration of exposure to invasive elements of care, including central vascular access, indwelling urinary catheters, and invasive mechanical ventilation, along with its related cumulative dose of sedating and neuroactive medications. Therefore, the central intervention for prevention is a daily multidisciplinary structured review and active discussion of a ‘safety bundle’ that includes 1) explicit review of ongoing indications for any indwelling catheters or tubes, or other ICU therapies associated with a risk of complications (e.g. antibiotics or sedating medications); 2) dialog regarding the potential for liberating the patient from each; 3) identification of any possible emerging complications; and 4) preventive measures being deployed, such as prophylactic anticoagulation, and early mobilization. In the AHA Scientific Statement, the writing committee describes the rationale and evidence for each element of such a ‘safety bundle’ and key aspects of its implementation, including principles for teamwork and effective communication.

Prevention of CICU-acquired infections:

• This objective includes prevention of central line-associated bloodstream infections (CLABSI), catheter-associated urinary tract infections (CAUTI), ventilator-associated pneumonia (VAP), other ICU healthcare-associated infections (HAI), and most specific to the CICU,infections related to mechanical circulatory support (MCS) devices.MCS device infections occur in an estimated 1% of cases of microaxial left ventricular support devices as an example.³
• Given the high proportion (>20%) of patients managed with invasive mechanical ventilation in advanced CICUs, clinicians practicing in this environment also need to become proficient in preventing, recognizing, and managing VAP and other ventilator-related complications.^{2, 4}
• Unfailing hand hygiene, rigorously sterile device placement, access site care, and minimization of days of device exposure are the key elements for the prevention of CICU-acquired infections.
• Stewardship of antimicrobial therapy is an important part of avoiding perpetuating and accelerating multidrug resistance among ICU pathogens.
• The benefit vs. risk of peri-implantation prophylactic antibiotics for temporary MCS is insufficiently studied to make firm recommendations.
• Avoidance of the femoral access site for central venous catheters is another practical suggestion.

Prevention of delirium:

• Diligent management of pain first, avoidance of excessive use of sedation, and preventive non-pharmacological measures are important to minimizing the duration of mechanical ventilation and minimizing the risk of ICU-related delirium, that occurs in up to 20% of patients.⁵
• An ABCDEF bundle (Assessment and management of pain; spontaneous awakening and Breathing trials, analgesia and sedation Choice; Delirium monitoring, prevention, and treatment; Early mobilization and exercise; Family engagement and empowerment) has been reported to reduce delirium, and mortality in general ICU patients.⁶
• Structured assessment using validated instruments for pain and delirium, targeted light sedation, and minimization of accumulation of sedatives, particularly benzodiazepines, are perhaps the most important elements of the bundle.
• In one of few CICU-based studies, prospective implementation of a structured nursing-driven sedation protocol that targeted light sedation (arousable to voice) decreased the average dose of sedatives and reduced mean ventilation times by 1.1 days.⁷
• The writing committee also suggests limiting antipsychotic treatment to patients with hyperactive delirium and minimizing the use of QTc-prolonging antipsychotic medications in the CICU population.

Prevention of ventilator complications:

• Practitioners in the CICU should be aware of the concepts behind and interventions valuable to mitigating the risk of ventilator-associated lung injury (VALI), including from volutrauma (from alveolar overdistension), atelectrauma (from repetitive alveolar opening and closing) and barotrauma (from elevated airway pressure).
• The key principle is targeting what is believed to be an optimal range for tidal volume and avoiding excessively high driving pressure.⁸
• The writing committee suggests a tidal volume of 6-10 ml/kg (ideal body weight), with lower tidal volume (6-8 ml/kg) for patients at high risk of VALI or with established acute respiratory distress syndrome, while avoiding a plateau pressure >30 cm H₂O.
• As well, clinicians in the CICU should be familiar with the potential hemodynamic benefits and complications of positive pressure ventilation in specific subsets of patients with acute and chronic cardiovascular disease. ⁹
• Data specific to acute cardiovascular disease have established the lack of benefit and the possibility of harm from targeting hyperoxia through treatment with supplemental oxygen.^10-12
• The writing group also describes the appropriate uses of non-invasive positive pressure ventilation to minimize the need for invasive ventilation or reintubation.

Prevention of gastrointestinal complications:

• Prevention of gastrointestinal bleeding is highly relevant in the CICU. Although in the general ICU population, the number needed to treat with routine stress ulcer prophylaxis is very high; recognizing the high prevalence of antithrombotic therapy in the CICU, the writing committee suggests that it is reasonable to administer stress ulcer prophylaxis for patients with high risk features (shock, renal replacement therapy, mechanical ventilation, or coagulopathy) who are receiving dual antiplatelet therapy, or patients receiving triple antithrombotic therapy.
• In addition to these considerations, attention to nutrition is a vital component of comprehensive care in the CICU. Malnutrition in the ICU is associated increased length of stay, infection, and hospital mortality.
• The writing committee suggests enteral nutrition within 24-48 hours of CICU admission in most patients unable to eat and identifies trophic enteral feeding as reasonable in patients with compensated or resolving shock, and those undergoing therapeutic temperature management (TTM).
• In general, parenteral nutrition should be avoided except in patients unable to meet >60% of caloric requirements after 7-10 days via enteral feeding.

Each of these critical areas for prevention of complications in the CICU, as well as the benefits of surveillance systems for medication complications, early mobilization, family engagement, and palliative care, are eloquently explored in this AHA Scientific Statement, which serves as a practical contemporary framework for maximizing the safety of the patients whom we care for in the CICU.