Prolonged Stay in ICU after Cardiac Surgery: Challenges –A Review

Hemoglobin A1C (HbA1c) measurement for risk stratification

Optimal glycemic control with a target HbA1c level of <6.5% has been found to decrease the incidence of sternal wound infections, events of ischemia, and related complications. Although there is no strong evidence-based guideline to tell what is the preoperative HbA1c cutoff value, various literature suggests a value <7% as an achievable goal. A clear demonstration of the long-term survival benefit is demonstrated in a recent retrospective review. However, it is difficult to extrapolate these data to cardiac surgery. Halkos et al. prospectively analyzed the relationship between HbA1c values and post-operative outcomes in 3555 patients.^[4] They found an increase in in-hospital mortality by fourfold when the HbA1c levels were above 8.4%. Furthermore, there was an increased odds for the occurrence of myocardial infarction (MI), deep sternal wound infection, and cerebrovascular accident.^[4] Another large study by Carson et al. examined 41,663 people with diabetes with 1,05,123 non-diabetic patients and found that the 30-day mortality and in-hospital morbidity were significantly higher to the tune of 23–37% in people with diabetes.^[5] Tight perioperative glucose control improves the post-operative outcome.^[4,5] Routine HbA1c testing is recommended, and if the value is more than 7%, they should be treated as diabetics.^[6]

Preoperative albumin measurement for risk stratification

There is an increased risk of mortality and morbidity in patients with a low serum albumin concentration. Hypoalbuminemia is found to be a prognosticator of preoperative risk, correlating with increased length of time on a ventilator, acute kidney injury (AKI), infection, longer LOS, and mortality. A preoperative serum albumin concentration of <3 g/dL may have an implication on the morbidity following cardiac surgery, especially on CPB. Its non-oncotic properties, such as immunomodulation, antibiotic transportation, endothelial stabilization, and anti-inflammatory effects, may have a role in critically ill cardiac patients. Albumin molecules also have been found to have antioxidant properties, which may be an advantage in recovery from the early inflammatory insult following a CPB, especially for a prolonged duration.^[7,8]

Correction of nutritional deficiency

In patients undergoing cardiac surgery, supplemental nutritional therapy targeting albumin levels (>3 g/dL) may improve the outcomes. This may require at least 7–10 days of intense nutritional therapy. This becomes all the more important when the patients have a history of weight loss of more than 10–15% in the past six months, have a body mass index (BMI) of <18.5 kg/m², and a serum albumin level of <3 g/dL without any hepatic or renal dysfunction.^[1]

Prehabilitation

An interprofessional multimodal approach focusing on bettering the nutritional and physical status of a patient is found to have a positive impact on bettering the post-operative complication rates in surgeries. This includes education about the disease and disease progression and outcomes, nutritional support, anxiety reduction, and social support. The same model has been extensively studied and practiced in colonic surgeries and is being extrapolated to cardiac surgery and is found to have a positive impact. The training of inspiratory muscles with spirometry exercises betters the post-operative respiratory complication rates.^[1,9] This requires a coordinated approach between the anesthesia and surgical team and the physiotherapy department, classifying the patients into discrete groups based on the preoperative physical status and listing the patients for cardiac surgery accordingly.

Patient engagement tools

Making use of the patient-smartphone interaction platform to improve the patient-healthcare interaction is desirable. The cost to the end user is often negligible. Digital health in cardiac surgery may be commonly applied in postoperative screening of possible or expected complications on a time-to-time basis. This, when integrated with the hospital database of the patient and the use of similar applications at the hospital level, will help in alerting the hospital about such a patient. Telehealth visits have been in use, especially post-COVID. This also ensures patient education, and patients often remain more active in self-care.^[10]

Smoking and alcohol

Tobacco smoking and alcohol consumption are known risk factors for post-operative complications involving respiratory tract, wound healing, metabolic derangements, and infections. Abstinence for four weeks minimum is found to have a favorable post-operative outcome, which may not be possible in urgent or emergency surgeries.^[1]

Surgical site infection (SSI) reduction

Reducing SSI requires a multidisciplinary approach involving surgeons, nurses, anesthesiologists, infection control teams, and the active participation of the patients themselves. Adherence to evidence-based guidelines and continuous quality improvement efforts are the cornerstone of achieving this goal. Reducing SSI is a crucial aspect of patient safety and post-operative care. SSI can lead to complications, prolonged hospital stays, increased healthcare costs, and patient discomfort. Some of the strategies to reduce SSI apart from following strict hand hygiene and aseptic techniques are as follows:^[11]

Rigid sternal fixation

Wire cerclage of the sternal ends is commonly practiced in cardiac surgery for sternal closure. This ensures approximation of the edges, but it has been found that the side-to-side movement of the sternal edge is not prevented with the wire cerclage. The use of rigid plate fixation is an alternative that has been studied and found to be beneficial, especially in high-risk groups like those with high BMI, COPD, and a history of chest wall radiation. There is a reduced incidence of mediastinal wound complication and better sternal adherence, as per a meta-analysis.^[14]

Hyperthermia

Temperature monitoring and normothermia are essential aspects of cardiac surgery, especially on a CPB. Prospective studies have demonstrated that a core temperature exceeding 37.9°C is known to cause cognitive impairment, infection, and renal impairment, all of which increase the LOS in ICU.^[15,16] Post-operative hyperthermia within 24 hours after the surgery may cause cognitive impairment, which may even persist up to 4–6 weeks after a CABG surgery. Normothermia with continuous surface warming should be adhered to.^[15]

Blood transfusion

Inappropriate transfusion of packed red blood cells (RBCs) and blood products such as fresh frozen plasma and platelets is known to have a negative impact on the patient’s recovery and prolong the ICU LOS. Transfusion practice in the Operating room and ICU should be point-of-care test-driven. The use of thromboelastography or rotational thromboelastometry has been found to help in avoiding unnecessary preoperative or intraoperative blood transfusion. Blood salvage techniques and the use of tranexamic acid or epsilon aminocaproic acid for correcting ongoing bleeding once surgical hemostats are done should be encouraged intraoperatively.

Glycemic control and insulin infusion

Hyperglycemia in the preoperative period is known to increase morbidity due to its varied effects on physiology. It has been attributed to oxidative stress, prothrombotic effects, glucose toxicity per se, and inflammation. Multiple randomized controlled trials do support the same on varied patient cohorts. A strict post-operative glycemic control is known to improve the post-operative outcomes. Using epidural analgesia in cardiac surgery is also known to ensue good post-operative glycemic control in such patients.^[17,18] Tight blood glucose control between 80 mg/dL and 110 mg/dL, at the same time avoiding hypoglycemia, is known to have a positive impact on post-operative outcomes. Still, subsequent studies have not been able to replicate those findings.^[16] Due to the higher incidence of hypoglycemia, blood glucose should be maintained between 110 mg/dL and 200 mg/dL.

Pain management

Parenteral opioids have been the mainstay in pain management in cardiac surgery, which has its own set of side effects, such as sedation, respiratory depression, nausea, and ileus. A multimodal analgesia approach using nonopioid or opioid-sparing techniques due to their additive or synergistic effects will ensure equipotent analgesia, at the same time bringing down the side effects of opioids, which would help in early discharge from the ICU and hospital. The use of non-steroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors have their own complications of renal dysfunction and thromboembolic events after cardiac surgery. The safest non-opioid analgesic prescribed is paracetamol, which may be given intravenously and converted to oral formulations once the gut function recovers. Tramadol is a common analgesic used after cardiac surgery, which has opioid as well as non-opioid effects, bringing down the requirement of morphine by almost 25% and improving pain scores. Pregabalin and gabapentin also have been tried and are found to reduce the opioid requirement drastically. A pregabalin administered one hour before and up to 2 days postoperatively is known to improve the pain scores compared to the placebo. Dexmedetomidine, an α-2 adrenergic agonist, is showing a lot of promise in analgesic management, bringing down the opioid requirement significantly, also with its favorable pharmacokinetic profile in decreasing the incidence of AKI after cardiac surgery.^[19-21] We have demonstrated earlier extubation and discharge from the ICU in cardiac surgical patients by thoracic epidural analgesia.^[22]

Delirium screening

An acute confusional state is characterized by disorganized thinking, inattention, or fluctuating mental status and is associated with reduced in-hospital and long-term survival. Detection of delirium at an early stage with a systematic screening tool, such as the confusion assessment method for ICU or the ICU delirium screening checklist, should be considered to improve the outcomes. This should be done at least once per nursing shift. The most common causes of delirium, such as pain, hypoxemia, a low cardiac output state, and sepsis, should be identified and treated accordingly.^[23] We found a lesser incidence of delirium post-cardiac surgery using dexmedetomidine.^[24]

Hypothermia

Hypothermia after cardiac surgery is found to be deleterious as it is associated with an increased risk of bleeding, infection, and arrhythmias, leading to prolonged LOS in the ICU. Persistent hypothermia is the failure to return to or unable to maintain a temperature of 36°C for 2–5 h after an ICU admission of a patient after cardiac surgery. Measures such as raising the ambient temperature, using warm intravenous fluids, and using Bair Hugger forced air warming blankets should be encouraged to mitigate this issue.^[25]

Chest tube patency

An efficient mediastinal and pleural tube drain management is essential after cardiac surgery as a clogged drain might lead to collection of blood in the pericardial or pleural sac, leading to cardiac tamponade or hemothorax, respectively. Furthermore, retained shed blood in the mediastinal space would hemolyze and trigger an oxidative inflammatory pathway, which is found to cause further pleural or pericardial effusion and is also associated with AF.^[1] The most common chest tube manipulation strategy used in ICUs is chest tube milking or suctioning out the clots from the chest tube. The effectiveness of the first method is found to be questionable, as suggested by a meta-analysis of randomized controlled trials. It is found to be harmful and ineffective while suctioning out the clots by a breach in the sterile barrier, which is again something that can lead to infections and may damage the internal structures. Active chest tube clearance methods may be used to manage the chest tube systems, and once the drainage levels become visibly serous, the drains should be removed as early as possible.^[1,26,27]

Pharmacological thromboprophylaxis

A patient, after cardiac surgery, remains in a hypercoagulable state, increasing the risk of vascular thrombotic events, which may be a deep venous thrombosis to a fatal pulmonary embolism (PE). Hence, effective thromboprophylaxis in the form of either anticoagulation or mechanical thromboprophylaxis – compression stockings and/or intermittent pneumatic compression devices should be prescribed until a patient is in hospital or until they are effectively mobilized. Prophylactic dose of anticoagulation should be considered from the 1^st post-operative day itself unless contraindicated. A meta-analysis by Ho et al. suggests that chemical thromboprophylaxis could reduce the vascular thrombotic risk without increasing the bleeding risk in such post-operative cardiac surgical patients.^[28,29]

Extubation strategy

Prolonged mechanical ventilation after cardiac surgery is known to be associated with long-term hospitalization, morbidity, and associated increase in hospital costs. Some of the common reasons are attributed to the complications like dysphagia and ventilator associated pneumonia. Fast-tracking protocols tailored to every ICU should be ensured in aiding early extubation of a post-cardiac surgical patient within six hours of ICU admission. Although early extubation has shown to be an effective strategy in bringing down the complications, the overall outcomes in a post-cardiac surgery patient depend on the intraoperative clinical variables like intra aortic, duration of surgery, blood transfusion, opioids, intraaortic balloon pump, etc. Hence, a direct association of early extubation with a significant reduction in complications have not been clearly demonstrated.^[30,31]

Acute Kidney Injury and prevention

AKI is found to complicate 22.3 % of all cardiac surgical procedures as per a meta-analysis by Hu et al., of which 2.3% end up receiving renal replacement therapy (RRT).^[32] Of all the strategies, the most effective one is to identify such potential at-risk patients before the surgery and ensure therapies or strategies to reduce the incidence of AKI. Although not used on a routine basis, urinary biomarkers such as urinary neutrophil gelatinase-associated lipocalin, tissue inhibitor of metalloproteinase-2, or insulin-like growth factor binding protein 7 are helpful in identifying patients who are at high risk of developing AKI.^[33,34] Discontinuing angiotensin-converting enzyme inhibitors I and angiotensin-II antagonists for 48 hours before surgery, avoiding hyperglycemia and radiocontrast agents close to surgery, close monitoring of the patient’s volume status and hemodynamics, and avoiding nephrotoxic medicines are few effective and proven strategies which may be implemented in bringing down the incidence of AKI.

Goal-directed fluid therapy (GDT)

Using monitoring techniques in aiding fluid therapy, vasopressor, and inotrope administration with a standardized algorithm helps in bettering the patient outcomes following cardiac surgery. The most commonly used end parameters are cardiac output, cardiac index, systemic venous oxygen saturation, and urine output. At the same time, calculating oxygen debt and oxygen consumption and serial monitoring of serum lactate levels helps in tight monitoring of the ongoing hemodynamic state and ensures a patient-tailored fluid administration. GDT has consistently demonstrated an improvement in the overall survival rates and hospital and ICU LOS across surgical specialties and not just in cardiac surgery.^[35,36] In a randomized prospective, multicenter trial of GDT after cardiac surgery, we have demonstrated earlier extubation and a favorable postoperative outcome with a reduced ICU LOS in high-risk cardiac surgical patients.^[37]

Right ventricular dysfunction after cardiac surgery

Right ventricular dysfunction after cardiac surgery occurs in 0.1% of the patients after a cardiotomy, in approximately 2–3% of the patients undergoing heart transplantation, and 10–20% of the patients needing left ventricular assist device insertion. The most commonly identified causes are as follows.^[47]

Management of the right ventricular (RV) dysfunction is focused on identifying the correctibles, such as hypoxemia, hypercapnia, acidosis, raised airway pressures on ventilation, and inotropes such as dobutamine, milrinone, and epinephrine in titrated doses. Treatable precipitants of right-sided heart failure include infection, anemia, thyroid dysfunction, PE, arrhythmia, or non-adherence to prescribed medications. Supraventricular tachyarrhythmias, especially atrial flutter and AF, are common causes of right-sided heart failure in patients with severe pulmonary hypertension. Diuretics are administered if the patient is volume-loaded. There should be a strong suspicion when there is a significant stroke volume variation (SVV) and pulse pressure variation (PPV), but there is no response to intravenous fluids. Hence, the reliability of SVV and PPV in RV dysfunction is questionable. Mechanical ventilation in acute RV dysfunction can turn out to be deleterious. The targets should be to limit the plateau pressure to <27 cm H₂O and keep the driving pressure to <18 cm H₂O. Reversing or preventing hypoxemic pulmonary vasoconstriction also should be ensured.^[48]

Strategies to reduce prolonged ICU stays

1. Preoperative optimization

   • Identifying high-risk patients

   • Optimizing comorbidities

   • Patient education and shared decision-making

2. ERACS protocols

   • Multidisciplinary approach

   • Early extubation

   • Reduced use of opioids

   • Early mobilization

3. Surgical techniques

   • Minimally invasive procedures

   • Off-pump bypass surgery - Hybrid approaches

4. Post-operative care

   • Aggressive pain management

   • Goal-directed fluid therapy

   • Early enteral nutrition

   • Delirium prevention strategies

5. Enhanced monitoring

   • Hemodynamic monitoring

   • Continuous cardiac output monitoring

   • Bedside ultrasound.