Dexmedetomidine Versus Midazolam-Fentanyl for Analgesia and Sedation

Valvular Cardiac Surgeries

Postoperative sedation is an essential component in recovery of the patient undergoing cardiac surgery. It facilitates the patient's unawareness of the environment as well as reduce the discomfort and anxiety caused by surgery, intubation, mechanical ventilation, suction, and physiotherapy. Despite the advances in anesthesia and surgical techniques, the duration of mechanical ventilation (MV) may be prolonged after cardiac surgery, due to the classic high-dose narcotic-based cardiac anesthesia.

In recent years, fast-track extubation (FTE) protocols have been developed to reduce the long period of intubation and complications that may occur due to the long duration of MV. Potential advantages of FTE protocols following surgery for congenital cardiac disease are reduced ventilator-associated pulmonary complications and the negative effects of positive pressure ventilation, reduced nosocomial infections, postoperative atelectasis, reduced requirements of sedatives and analgesic drugs, early enteral feeding, rapid patient mobilization, and shorter intensive care unit (ICU) stay. The ideal analgesic-sedative agents would keep the patient comfortable without anxiety. It would effectively provide adequate sedation, but also allow neurologic evaluation of the patient, ideally without stopping administration of the drug. It would have minimal hemodynamic and respiratory depressant effects. It also would have a rapid onset and offset of action without drug accumulation or active metabolites, making it easily titratable and allowing rapid recovery with a prompt return to normal activity after discontinuation. Opioids and benzodiazepines are the most frequently used analgesic-sedative agents after cardiac surgery. Although opioid can provide excellent analgesia, the doses for effective pain relief may lead to undesirable side effects, such as respiratory depression requiring prolonged MV, hemodynamic instability, tolerance, and significant withdrawal symptoms that also delay patient recovery. Dexmedetomidine is a highly selective α2-adrenoreceptor agonist. Presynaptic activation of α2-adrenoreceptors at sympathetic nerve endings inhibits catecholamine release. The major effect of dexmedetomidine is maintaining sedation-analgesia without a respiratory depressant effect. It has relatively few cardiovascular side effects and produces sleep-like sedation without narcosis or respiratory depression. Indeed, current guidelines recommend lighter levels of sedation to manage ventilated patients preferably using nonbenzodiazepine sedatives. Nevertheless, there is currently no consistent recommendation regarding which nonbenzodiazepine sedative agents should be used.

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