Cardiac

Preoperative Cardiac Optimization

Another Anaesthesia review discusses the approach to preoperative cardiac risk stratification, hypertension, heart failure, murmurs, beta-blockers and other medication management, and implantable electronic cardiac devices.

Also discussed is the role of preoperative investigation such as EKG, CXR, and Echocardiography, as well as serial monitoring of Troponins and BNP. Some evidence for exercise therapy as a preoperative cardiac prehabilitation is reviewed.

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ICDs and Electromagnetic Interference

Bipolar cautery is ideal to minimize electromagnetic interference with Implantable Cardioverter Defibrillators (ICDs).

Where monopolar is used, this study employed protocolized placement of electrosurgery dispersive electrode positioning to divert return current away from the ICD. They found no interference from below-umbilicus procedures but 7% in above-umbilicus procedures and as high as 29% in cardiac surgery (using underbody Megadyne, described as alarmingly high!).

The findings support recommendations that reprogramming and suspending anti-tachycardia functions may be unnecessary in below-umbilicus procedures. However higher risk exists in above-umbilicus procedures and especially in cardiac surgery and underbody dispersive electrodes.

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Perioperative Atrial Fibrillation in Cardiac Surgery

A practice advisory is issued from cardiovascular anesthesiologists for the prophylaxis and treatment of perioperative atrial fibrillation, which has an occurrence of 30 – 50% in this population.

They review such strategies as Beta-Blockers, Amiodarone, cardioversion, Calcium Channel Blockers, Vernakalant, Colchicine etc.

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Recommendations table

Contrast associated Kidney Injury

The PRESERVE trial studying angiography showed no benefit for iv bicarbonate or oral acetylcysteine in preventing death, need for dialysis, or persistent decline in kidney function at 90 days or for the prevention of contrast-associated acute kidney injury ( link ).

This subgroup analysis looked at percutaneous coronary intervention (PCI) and found: Among patients with chronic kidney disease undergoing PCI, there was no benefit of IV sodium bicarbonate over IV sodium chloride or of acetylcysteine over placebo for the prevention of contrast associated acute kidney injury or intermediate-term adverse outcomes.

It is perhaps a bridge too far to declare contrast-induced nephropathy a myth, but for now adequate fluids and attention to nephrotoxic agents like NSAIDS, diuretics, ACEIs etc. are important.

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ECMO Resuscitation in Pediatric Cardiac Arrest

Recent evidence in adults found benefit in using Extracorporeal Membrane Resuscitation in OR cardiac arrest in particular from hemorrhage ( link ).

This study in infants and children also found some positive outcomes after in-hospital cardiac arrest.  “About one third of children survived with good neurobehavioral outcome 1 year after receiving extracorporeal cardiopulmonary resuscitation for in-hospital arrest. Open-chest cardiac massage and minimum postarrest lactate were associated with survival with good neurobehavioral outcome at 1 year”.

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Etomidate vs. Propofol

Etomidate is the time-honoured ATLS-recommended induction agent for those in shock due to its hemodynamic stability. This randomized study compared it with Propofol in cardiac surgery anesthesia induction. They confirmed: Propofol caused a 34% greater reduction in MAP-time integral from baseline after induction of anaesthesia than etomidate, despite more frequent use of vasopressors with propofol, confirming the superior haemodynamic profile of etomidate in this context.

Etomidate is not easily available everywhere – such as in Canada, where Ketamine’s wild resurgent popularity makes it a common agent in this scenario.

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Diastolic Dysfunction and Adverse Cardiac Outcomes

This study focussed on isolated diastolic dysfunction (where Ejection Fraction > 50%). Less extensively studied than systolic dysfunction, diastolic dysfunction is associated with age, ischemia, hypertension and diabetes. These authors found that in patients with isolated diastolic dysfunction undergoing noncardiac surgery, 10.0% develop major adverse cardiovascular events (MACEs) during hospital stay after surgery; grade 3 diastolic dysfunction is associated with greater risk of MACEs.

It is unsurprising that severe grade 3 diastolic dysfunction is a higher risk, although this was a retrospective study and most patients had echocardiography due to an already higher risk status because of age and cardiovascular disease.

Other higher risk factors were also extracted from the study: age ≥70 years, body mass index <18.5 kg/m2, hypertension, coronary heart disease, arrhythmia, renal insufficiency, regular glucocorticoid therapy, symptomatic diastolic dysfunction, ASA classification grades III and IV, intraoperative use of vasopressors or antihypertensives, intraoperative fluid infusion rate ≥9.0 mL/kg/h, cancer surgery, duration of surgery ≥120 minutes, and medium- and high-grade complexity of surgery. BMI > 30 was interestingly associated with a lower risk.

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Hydroxyethyl Starch Discontinuance and CABG Outcome

This study reflects the shift away from colloids, in particular Hydroxyethyl Starch (HES), due to its association with adverse outcomes particularly in sepsis and renal dysfunction. Its use during surgery has persisted somewhat, with evidence of improved or no different outcomes using HES in abdominal surgery, not necessarily translatable to cardiac or critical care settings.

While suffering from retrospective limitations, this study showed that “for patients undergoing CABG on CPB, disinvestment in HES was associated with a reduced length of hospital stay and reduced blood product transfusion, without measurable change in death, renal failure, or dialysis rate. This association suggests that the continued use of HES in the cardiac surgical setting should be carefully reconsidered”.

Cost savings is another advantage, and many would advocate removing HES from anesthesia carts, suggested in a correspondence in the same journal (CJA)

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Perioperative management of direct oral anticoagulants (DOACS) in cardiac surgery

An international consensus on managing new oral anticoagulants in patients having cardiac surgery provides pertinent information that will enlighten their use outside cardiac surgery also.

Measurement of DOACS may be useful in emergencies or uncertainty, or in significant renal or hepatic dysfunction; however, such measurement as well as routine coagulation testing is not recommended. Greater caution is also needed in the elderly. Dabigatran is particularly dependent on renal function.

Normal prothrombin time or activated partial thromboplastin time results exclude excess levels of dabigatran, rivaroxaban and edoxaban, but not apixaban. Normal thrombin time precludes significant dabigatran plasma levels, and the aPTT shows some correlation here also – for precise measurements, the diluted thrombin time (dTT), the ecarin clotting time or the ecarin chromogenic assay may be used. For the precise measurement of drug concentrations of all FXa inhibitors, chromogenic and calibrated anti‐FXa tests are recommended.

Reversal agents: for dabigatran, idarucizumab is available; for the FXa inhibitors, andexanet alpha has been approved in the US, and ciraparantag is currently under investigation. Ultrafiltration and Hemodialysis are also discussed for Dabigatran, and non-specific approaches of varying efficacy include prothrombin complex concentrate, fibrinogen concentrate, tranexamic acid and/or factor VIIa.

In general, withholding for 2 days is appropriate. For Dabigatran, this may need 3-5 days depending on renal function. Resumption at therapeutic doses is recommended after 2-3 days and after removal of chest drains. (In the non-cardiac surgery setting, resumption may be sooner depending on bleeding risk). Prophylactic doses may be needed sooner after surgery for thromboembolic prophylaxis. Bridging agents are not recommended for interruptions less than 4 days, as increased bleeding without lower thromboembolism is reported. Individualized approaches may be needed based on CHA2DS2‐VASc Score and bleeding risk.

From an anesthesia perspective, neuraxial anesthesia performance should be equated with high bleeding risk and longer interruption may be the preferred – the ASRA provides one such set of guidelines.

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ECMO for Cardiac Arrest

Refractory cardiac arrest was defined as no return of spontaneous circulation after 30mins of CPR.

This was a small observational study of 23 patients suffering cardiac arrest in the Operating Room who underwent extracorporeal cardiopulmonary resuscitation. The survival rates of neurologically‐intact subjects were 9/23 (39%) and 6/23 (26%) at 24 hours postoperatively and at hospital discharge, respectively.The main cause was hemorrhagic shock and 23% of these were discharged neurologically intact.

Where available, extracorporeal cardiopulmonary resuscitation is suggested as an option for refractory cardiac arrest in the OR due to hemorrhage.

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