The effects of remifentanil on cerebral capacity in awake volunteers

Remifentanil and the brain

BACKGROUND AND AIM

Remifentanil is an ultra-short-acting opioid, increasingly used today in neuroanesthesia and neurointensive care. Its characteristics make remifentanil a potentially ideal agent, but previous data have cast a shadow on this opioid, supporting potentially toxic effects on the ischemic brain. The aim of the present concise review is to survey available up-to-date information on the effects of remifentanil on the central nervous system.

METHOD

A MEDLINE search within the past seven years for available up-to-date information on remifentanil and brain was performed.

RESULTS

Concise up-to-date information on the effects of remifentanil on the central nervous system was reported, with a particular emphasis on the following topics: cerebral metabolism, electroencephalogram, electrocorticography, motor-evoked potentials, regional cerebral blood flow, cerebral blood flow velocity, arterial hypotension and hypertension, intracranial pressure, cerebral perfusion pressure, cerebral autoregulation, cerebrovascular CO(2) reactivity, cerebrospinal fluid, painful stimulation, analgesia and hyperalgesia, neuroprotection, neurotoxicity and hypothermia.

CONCLUSION

The knowledge of the influence of remifentanil on brain functions is crucial before routine use in neuroanesthesia to improve anesthesia performance and patient safety as well as outcome.

Remifentanil

Remifentanil (Ultiva), a 4-anilidopiperidine derivative of fentanyl, is an ultra-short-acting micro-opioid receptor agonist indicated to provide analgesia and sedation in mechanically ventilated intensive care unit (ICU) patients.Analgesia-based sedation with remifentanil is a useful option for mechanically ventilated patients in the ICU setting. Its unique properties (e.g. organ-independent metabolism, lack of accumulation, rapid offset of action) set it apart from other opioid agents. Remifentanil is at least as effective as comparator opioids such as fentanyl, morphine and sufentanil in providing pain relief and sedation in mechanically ventilated ICU patients. Moreover, it allows fast and predictable extubation, as well as being associated with a shorter duration of mechanical ventilation and quicker ICU discharge than comparators in some studies. In addition, remifentanil is generally well tolerated in this patient population. Thus, remifentanil is a welcome addition to the currently available pharmacological agents employed in the management of mechanically ventilated ICU patients.

Remifentanil

Remifentanil (Ultiva), a fentanyl derivative, is an ultra-short acting, nonspecific esterase-metabolised, selective mu-opioid receptor agonist, with a pharmacodynamic profile typical of opioid analgesic agents. Notably, the esterase linkage in remifentanil results in a unique and favourable pharmacokinetic profile for this class of agent. Adjunctive intravenous remifentanil during general anaesthesia is an effective and generally well tolerated opioid analgesic in a broad spectrum of patients, including adults and paediatric patients, undergoing several types of surgical procedures in both the inpatient and outpatient setting. Remifentanil is efficacious in combination with intravenous or volatile hypnotic agents, with these regimens generally being at least as effective as fentanyl- or alfentanil-containing regimens in terms of attenuation of haemodynamic, autonomic and somatic intraoperative responses, and postoperative recovery parameters. The rapid offset of action and short context-sensitive half-time of remifentanil, irrespective of the duration of the infusion, makes the drug a valuable opioid analgesic option for use during balanced general inhalational or total intravenous anaesthesia (TIVA) where rapid, titratable, intense analgesia of variable duration, and a fast and predictable recovery are required.

Comparative tolerability of sedative agents in head-injured adults

Sedative agents are widely used in the management of patients with head injury. These drugs can facilitate assisted ventilation and may provide useful reductions in cerebral oxygen demand. However, they may compromise cerebral oxygen delivery via their cardiovascular effects. In addition, individual sedative agents have specific and sometimes serious adverse effects. This review focuses on the different classes of sedative agents used in head injury, with a discussion of their role in the context of clinical pathophysiology. While there is no sedative that has all the desirable characteristics for an agent in this clinical setting, careful titration of dose, combination of agents, and a clear understanding of the pathophysiology and pharmacology of these agents will allow safe sedative administration in head injury.

Les morphiniques (sufentanil et rémifentanil) en neuro-anesthésie

Remifentanil is the latest available compound of the 4-anilidopiperidine derivatives. It is characterized by an ultrashort duration of action and a metabolism independent of both hepatic and renal functions. Its main drawback is a lack of residual analgesia and the risk of postoperative hyperalgesia. Since its introduction in clinical practice, this drug has been compared to other congeners in a few studies in the setting of neurosurgery. Cerebral hemodynamics, intracranial pressure and CO(2) reactivity are similar to the effects of fentanyl and sufentanil provided that systemic arterial pressure is maintained. Haemodynamics does not greatly vary according to the type of the opioid. Fentanyl and sufentanil require higher hypnotic dosage (halogenated agents, propofol) and remifentanil is accompanied by greater volumes of fluid infusion. A marked reduction in extubation times and superior level of consciousness are reported with remifentanil. Rescue analgesic has to be given faster but pain scores remain low. Morphine 0.08 mg/kg IV administered at bone replacement results in good postoperative analgesia without delayed recovery. In summary, remifentanil is appropriate when rapid recovery and neurological evaluation are desired. Conversely, sufentanil is more suitable and easier to administer when postoperative mechanical ventilation and postponed awakening are scheduled.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Remifentanil conscious sedation during regional anaesthesia for carotid endarterectomy: rationale and safety

OBJECTIVES

to prospectively evaluate the safety and efficacy of remifentanil during regional anaesthesia for carotid endarterectomy.

METHODS

twenty-eight consecutive patients underwent carotid endarterectomy with combined superficial and deep cervical plexus block supplemented with continuous intravenous 0.04 microg.kg(-1).min(-1)remifentanil infusion. Depth of sedation was monitored using the Observer's Assessment of Alertness/Sedation Scale (OAA/S). The degree of pain, discomfort and anxiety was self-assessed by the patients using a horizontal visual analogue scale.

RESULTS

all patients experienced adequate comfort and analgesia. No local anaesthetic supplementation was necessary. No patient had a OAA/S score lower than 4 (with 5=awake/alert to 1=asleep). Respiratory depression did not occur. Selective shunting was required in four cases. No patient was converted to general anaesthesia. There were no permanent neurological deficits, cardiopulmonary complications or deaths.

CONCLUSION

remifentanil as a supplement to regional anaesthesia for carotid endarterectomy, provides comfort and analgesia without hampering mental status evaluation.