Anesthesia for Interventional Cardiology: An Overview

Introduction:

Interventional cardiac procedures have become an integral part of modern medicine, aiding in timely diagnosis and treatment, reducing morbidity and mortality rates, and thus improving quality of life. Interventional catheterization procedures have increased exponentially over the years, and the role of anesthesia is of paramount importance in carrying out uneventful operations. Primary angioplasty has become the standard of management of acute myocardial infarction, and new techniques have been developed to treat cardiac diseases such as mitral regurgitation, aortic stenosis, and atrial septal defects percutaneously. Advances in interventional cardiology have led to increasing involvement of the anesthesiologist because many procedures, such as MitraClip and TAVI (transcatheter aortic valve implantation), require general anesthesia or deep sedation.

What Is Interventional Cardiology?

Interventional cardiology is a branch of cardiology that diagnoses and treats heart and blood vessel conditions using small tubes called catheters. These small tubes put through blood vessels allow healthcare givers to avoid open-heart surgeries and yet assist in achieving positive outcomes.

What Are Some Interventional Cardiology Procedures?

• Coronary angiography or coronary catheterization.

• Coronary angioplasty or percutaneous coronary intervention (PCI).

• Congenital heart defect closure.

• Stenotic heart valve treatment.

• Permanent and temporary pacemaker/AICD (autonomic implantable cardioverter defibrillator)/CRTD (cardiac resynchronization therapy) implantations.

• Myocardial and endomyocardial biopsy.

• Electrophysiological studies.

• Radiofrequency catheter ablation.

• Endovascular neuromodulation treatment for heart failure patients (ENDO-HF).

• Hybrid procedures.

What Are the Types of Anesthesia Used in Interventional Cardiac Procedures?

Local Anesthesia:

• The local anesthetic agents fall into two broad groups: amino ester and amino amide. The amino ester agents are Procaine, Tetracaine, and Benzocaine. The most common amino amide agent used is Lidocaine.

• It is typically a subcutaneous injection during invasive cardiology procedures due to its rapid onset (three to five minutes), short duration of action (30 to 60 minutes), and minimal risk of cardiotoxicity.

• Mepivacaine, Bupivacaine, and Ropivacaine are other alternatives in cases of Lidocaine allergy.

• Due to the effects on the sodium channels, toxicity may result in conduction abnormalities like widened PR or QRS complex, bradycardia, heart block, and negative inotropy.

• The maximum acceptable dose is 5 mg/kg (milligram per kilogram) of Lidocaine, 5 mg/kg of Mepivacaine, 2 mg/kg of Bupivacaine, and 2.5 mg/kg of Ropivacaine.

• The most rapid onset is Lidocaine, and the most potent is Bupivacaine.

• Duration of action is most extended with Bupivacaine and shortest with Lidocaine and Mepivacaine.

Sedation:

• The American Society of Anesthesiologists (ASA) classifies sedation into four categories:

  • Minimal sedation (anxiolysis).

  • Moderate sedation (conscious sedation).

  • Deep sedation.

  • General anesthesia.

• Minimal sedation (anxiolysis) is a drug-induced state where patients respond to verbal commands. Airway reflexes, ventilatory, and cardiovascular functions are unaffected. However, cognitive function and physical coordination may be impaired.

  • Anxiolysis is typically achieved with benzodiazepines, like Midazolam, during cardiac catheterization.

  • Moderate sedation (conscious sedation) is a drug-induced consciousness depression in which the patients will respond to verbal commands or by light tactile stimulation.

  • Interventions are not required to maintain a patent airway as spontaneous ventilation is adequate.

  • Moderate sedation is the preferred level of sedation for cardiac catheterization.

  • Deep sedation is a drug-induced depression of consciousness where patients cannot be easily aroused. However, they respond to painful or repeated stimulation (shoulder rub, sternal rub, etc.).

  • The ability to maintain an independent ventilatory function is impaired. Hence, assistance is required to maintain a patent airway, as spontaneous ventilation is inadequate.

During more involved cardiology procedures, a combination of benzodiazepines, opiates, and Propofol can be used to achieve moderate sedation.

General Anesthesia:

• It is defined as a drug-induced loss of consciousness in which patients cannot be aroused, and the ability to maintain an independent ventilatory function is lost and hence requires assistance to maintain a patent airway and positive pressure ventilation.

• Common agents used for general anesthesia include Propofol, Ketamine, and Etomidate, and volatile gases like Halothane, Isoflurane, Desflurane, and Sevoflurane.

• When administering general anesthesia, it is necessary to reverse the effects in cases of hemodynamic or respiratory instability.

• Cardiology procedures that require general anesthesia should be assisted by an anesthesiologist.

What Are the Anesthetic Agents Used in Interventional Cardiology Procedures?

1.Midazolam:

• Benzodiazepines provide minimal sedation (anxiolysis) by reducing cell excitability through their action on the gamma-aminobutyric acid (GABA) and chloride channels of the cell.

• The benzodiazepine of choice during cardiology procedures is Midazolam, also known as Versed.

• Midazolam is preferred because of its quicker onset of action (two to three minutes), shorter duration time, and mild anterograde amnesia.

• Midazolam is a lipophilic benzodiazepine that allows it to enter the central nervous system quickly.

• Midazolam dosing usually starts at 1 mg intravenously, and it is then titrated to the desired effect.

• In terms of cardiotoxicity, it is relatively safe and has no major effects on hemodynamics.

• Respiratory status should be monitored closely as respiratory depression can occur due to its depression of central nervous system function.

• An additional effect may be post-procedural delirium, which should be considered in elderly patients. If necessary, the reversal can be achieved with Flumazenil, a GABA receptor antagonist.

• Flumazenil is administered with a starting dose of 0.2 mg, which can be titrated up by 0.1 to 0.2 mg/min to a total maximum dose of 1 mg.

2.Fentanyl:

• Like benzodiazepines, opioids may also be used for anxiolysis. They also possess analgesic properties but lack amnestic effects.

• Opioids can be combined with benzodiazepines to produce anxiolysis (reducing anxiety), analgesia (painkiller), and amnesia (loss of memory).

• Fentanyl, in combination with Midazolam, is the preferred agent for sedation and analgesia during cardiac catheterization, mainly using radial access, since they have been shown to reduce radial artery spasms through endothelial relaxation.

• Fentanyl is highly lyophilic, which allows it to enter the central nervous system at a faster rate. The half-life of Fentanyl is estimated to be between 1.5 and seven hours, and it is metabolized by the liver.

• Recommended dosing for Fentanyl is 12.5 to 50 mcg (microgram) intravenously, and this can be repeated every three to five minutes as needed.

• In terms of potential side effects, Fentanyl can cause muscular rigidity, hypoventilation, respiratory depression, and hypoxia (lack of oxygen).

• Opioid reversal can be achieved with Naloxone, an opioid antagonist, at doses of 0.2 to 2 mg. The onset of reversal occurs in two to three minutes if given intravenously.

• Slow administration is recommended unless the level of sedation is causing hemodynamic compromise or respiratory distress to avoid the effects of rapid reversal.

• Rapid reversal can cause withdrawal symptoms, which include elevated blood pressure and respiratory rate.

3. Propofol:

• Numerous studies have reported the benefit of using Propofol for certain cardiology procedures like cardioversions, ablations, TEE (transesophageal echocardiography), and TAVR (transcatheter aortic valve implantation) that require a higher level of patient sedation.

• Compared to sedation with Midazolam, Propofol has a shorter time to onset and faster recovery time].

• Dosing for healthy adults is calculated by adjusted body weight. Initial dosing used for cardiology procedures is 0.5 to 1 mg/kg, followed by 0.25 to 0.5 mg/kg every one to three minutes.

• When given in intermittent boluses, 10 to 20 mg is typically adequate to achieve moderate sedation.

• The onset of action is less than one minute, but this can vary due to dose dependence.

• Caution must be taken to avoid adverse effects, which include hypotension, QT interval prolongation, myoclonus (sudden muscle jerks), and apnea (breathlessness).

• Hypotension is most severe in those patients with reduced left ventricular systolic function. Titration must also be performed with caution, as the therapeutic index is narrow, and patients may transition from deep sedation to general anesthesia if overdosed.

4. Ketamine:

• Ketamine is the most commonly selected dissociative agent for cardiology procedures.

• Ketamine has recently gained recognition in the cardiac catheterization lab due to its ability to produce amnesia, analgesia, and sedation.

• It also allows for the preservation of laryngeal and pharyngeal reflexes and spontaneous respiration and has minimal effects on blood pressure.

• Some studies have found a mild cardiac stimulatory effect with ketamine, which can improve blood pressure, atrial contraction, and heart rate during procedures.

• The dosing of ketamine when used for procedural sedation is 1 to 2 mg/kg over a minute. Additional dosing may be provided every five to ten minutes at 0.5 to 1.0 mg/kg.

• The onset of action is almost immediate when administered intravenously. It is metabolized in the liver and has a half-life of approximately 45 minutes.

Conclusion

As the field of interventional cardiology continues to grow, invasive procedures will only become more common. Thus, a thorough understanding of sedation, anesthesia, and pre-procedural assessment will become a crucial and necessary aspect of all cardiovascular care. It is the need of the hour for an anesthesia professional to be familiar with the challenges occurring in the procedures carried out outside the operation theaters, understand the procedure itself, and manage anesthetic intervention safely in such cases.