71.GENERAL ANESTHETIC USED IN PATIENT WITH MYOCARDIAL INFARCTION

A.ISOFLURANE
B.SEVOFLURANE
C.HALOTHANE
D.ENFLURANE

ANS:ISOFLURANE


Inhalational Agents

Overview:
The use inhalational agents in cardiac surgery involves a balancing between desirable features and disadvantages

Advantages of  inhalation anesthetics

• Fulfill objectives of anesthesia:

1.  causes unconsciousness
2.  muscle relaxation
3.  rapid ventilatory function recovery {allowing early tracheal extubation postoperatively}

•  Dose-related  reduction in ventricular work/oxygen consumption
•  Easily reversible
•  Amnesia
•  Titratable myocardial depression
•  Attenuation of autonomic {sympathetic} response to surgical stimulation and cardiopulmonary bypass

 Disadvantages of inhalation anesthetics

•  Myocardial depression-excessive under some conditions
•   Hypotension, secondary to either vasodilation or reduced by myocardial contractility
•  Incomplete suppression of sympathetic responses to noxious/painful stimulation
•  Absence of postoperative analgesia {i.e., sub-anesthetic concentrations do not provide analgesia}
•  Post-operative shivering, secondary to peripheral vasodilation -- would be accompanied by increased oxygen demand because of excessive heat loss

In cardiovascular surgery, the combination of volatile anesthetics and narcotics optimizes advantages of both, while reducing the likelihood of untoward systemic responses

Tailoring of inhalational agents to the patient's needs-- examples:
Patient has a high systemic vascular resistance [high afterload, which necessarily increases myocardial oxygen requirements by increasing ventricular wall tension]: Appropriate inhalational agent = possibly isoflurane (Forane) which produces vasodilation
Patient exhibits cardiac hypertrophy {hypertrophic cardiomyopathy}:  Appropriate inhalational agent  = possibly enflurane (Ethrane), taking advantage of that drug's myocardial depressant effect