Cardiac Anesthesia

 Question:  How do you safely anesthetize a patient with abnormal vascular circulation and changes on echocardiograph examination? 

What are the consequences of the different premedication or intravenous anesthesia drugs?  How and why would you choose one inhalant over another?  What intra-operative concerns could you anticipate based on

the procedure and what drugs could be used to prevent or address this consequence?

Answer and Discussion:  To safely anesthetize a patient with compromised cardiac function and abnormal circulation, the goal is to preserve the function as close to the non-anesthetized normal parameters as possible.  A premedication of fentanyl and midazolam, followed by induction with etomidate or alfaxalone and maintenance with sevoflurane and a combined fentanyl and midazolam constant rate infusion can be used.  Etomidate is a cardiac-sparing induction agent that is rapidly hydrolyzed by both hepatic and plasma esterases.12  The drawback is that it can suppress the adrenocorticol responses and cortisol for 2-6 hours.  An alternative to etomidate is Alfaxalone which gives a smooth induction with minimal cardiac impact. 
​Injectable premedication drugs that are considered cardiac-safe include benzodiazepines and opioids.3  The main negative cardiac effect that manifests with opioids is a decrease in heart rate because of the stimulation of the medullary vagal nucleus resulting in increased vagal tone.4  This can be corrected with an anticholinergic such as glycopyrrolate.5  Benzodiazepines, such as midazolam, have minimal impact on cardiac function and act synergistically with fentanyl. 3 

            The choice of sevoflurane as the inhalant agent was made because of its innate characteristic of being poorly soluble in blood, less so than isoflurane.  The advantage is that the lower the blood solubility of an anesthetic agent is, the more rapidly the partial pressure can be changed and the faster the degree of CNS depression can be adjusted.6  This translates into a faster induction, faster recovery, and a faster rate of adjustment of the anesthetic depth.

The potential problems with this regimen are an opioid-induced bradycardia treated with an anticholinergic and resulting in a sinus tachycardia.  This can negatively impact perfusion and make intrathoracic suture placement more difficult.   A consideration for this procedure was that the ligation can increase the blood pressure and cause a reflex bradycardia or arrest.  In some cases, we use repeat boluses of glycopyrrolate to correct a low heart rate. 

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