Interaction Of Sufentanil

Volatile Aspects

Combining the opioid sufentanil with a volatile agent such as desflurane or sevoflurane, minimal alveolar concentration (MAC) dose-proportionally is reduced, whereby a high dose of sufentanil reduced requirements of the volatile agent by 60-70% (Figure III-44). When compared to fentanyl this MAC reduction is much more pronounced [41] which is why in a balanced type of anesthesia the usually administered concentration of the volatile anesthetic can be reduced by at least 50%.

Muscle Relaxants

The simultaneous application of sufentanil and a muscle relaxant such as pancuro-niumbromide results in blunting the usual bradycardic and hypotonic action of the

Figure 111-43. Sensory-evoked potential before and after laryngoscopy and intubation (L & I). Note the significant higher increase in late amplitude height in patients with fentanyl, suggesting a higher sensory impulse flow of nociceptive activity to the CNS (Adapted from [119])

Figure III-44. Dose-related comparable reduction of enflurane following increasing doses of sufentanil or fentanyl (Adapted from [132])

Heart Rate (beatsMirn)

Control 2 5 10 Intubation m

Control 2 5 10 Intubation

Minutes After Drug

Figure III-45. Heart rate changes following the combined application of sufentanil with pancuronium-bromide and vecuronium respectively (Adapted from [134])

opioid (Figure III-45). While such compensatory effect is due to the vagolytic and sympathomimetic action it is not seen when the muscle relaxant vecuronium is co-administered with the opioid. This lack in effect is related to negligible autonomic reactions of this muscle relaxant. Because pancuroniumbromide is able to counteract the vagomimetic effects of sufentanil, such a combination is preferred in patients, where a pronounced decline in blood pressure has to be anticipated. Therefore, the combination of sufentanil with vecuronium or atracurium sometimes can result in a major drop in mean artrial pressure with bradycardia than the combination with pancuroniumbromide (Figure III-45).

In summary, it has to be clarified that in spite of the decline in blood pressure after sufentanil, this can not be taken as an indicative sign of myocardial ischemia

The simultaneous and rapid injection of sufentanil with the polarizing muscle relaxant succinylcholine, due to the bradycardic effect of the latter, results in pronounced bradycardia than seen after sole injection of the opioid. Also, when given together with sufentanil, due to the succinyl-induced rise of potassium and histamine, which by itself already induces a decline in mean arterial pressure, there is a potentiation of the hypotensive effect. The hypotensive effect of sufentanil can be diminished by the slow injection over a period of 2 min or by titration of the opioid to the desired amount.

Barbiturates

Because a barbiturate like thiopental, when administered together with a muscle relaxant for the induction of anesthesia results in a significant increase in heart rate and systolic pressure, the product of both (the rate-pressure product) can be considered as an index of myocardial oxygen demand (MVO2) exceeding significantly the awake-control situation (Figure III-46). This increase can significantly be reduced or even totally attenuated when a small dose of sufentanil of 0.5-1.0 ^g/kg body weight is given prior to both induction agents (Figure III-46).

Control | intubation 1 min 3 min

Pre-lntubation Post-Intubation

Control | intubation 1 min 3 min

Pre-lntubation Post-Intubation

Figure III-46. Hemodynamic consequences during the induction of anesthesia with thiopental in combination with different doses of sufentanil (Adapted from [135])

Due to the attenuation of the hemodynamic responses following laryngoscopy and intubation, sufentanil is able to preferably block the nociceptive reflex mechanism, which is usually observed during the induction period. However, when using a combination of a barbiturate and sufentanil, one should realize that the dose of the hypnotic should be reduced accordingly. For the induction of unconsciousness, usually a sole dose of thiopental of 4.08mg/kg is necessary. Adding sufentanil (0.5-1.0 ^g/kg body weight) to the induction agent there is a significant reduction of the dose of the barbiturate to 1.99-1.32 mg/kg body weight [135].

Anesthesia, however, can also be induced by the sole use of sufentanil. When using 2-8 ^g/kg body weight of sufentanil this especially is of advantage in cardiac patients, because coronary sinus blood flow (CSBF), an index of coronary perfusion, mean arterial pressure and heart rate are not affected because of intubation, and following sternotomy [136]. Since the decline in mean arterial pressure correlates with a decline in myocardial oxygen demand (MVO2) it can be concluded that sufentanil is a preferable agent for the induction of anesthesia in patients undergoing coronary artery by-pass graft operation (Figure III-47).

In summary, drug-drug interactions with sufentanil differ significantly resulting in either a decrease or an increase of hemodynamics. Most of all it is important to know, which of the additionally used agents result in a prolongation of effects, so that there is no overhang and the patient needs additional time on the ventilator, supervision, or there is retarded awakening (Table III-14).

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