Opioid Neurotoxicity

Comparative effects of fentanyl versus sufentanil on cerebral oxygen saturation and postoperative cognitive function in elderly patients undergoing open surgery

This study was aimed to systematically evaluate the effects of fentanyl and sufentanil on intraoperative cerebral oxygen saturation changes and postoperative cognitive function in elderly patients undergoing open surgery. Ninety-six elderly patients who had undergone open surgery under general anesthesia were randomly divided into fentanyl group (F group, anesthesia by fentanyl, 4 g/kg) and sufentanil group (S group, anesthesia by sufentanil, 0.4 µg/kg). There were no significant differences between the F group and S group in the general characteristics of patients. Compared to the F group, the S group had a better effect on suppressing the stress response, maintaining a stable hemodynamic status and achieving better anesthesia effects. The anesthesia recovery time of the S group was significantly shorter than that of the F group. There was no significant difference between the two groups in the intraoperative and postoperative agitation. Patient's waking time and extubation time were significantly shorter in the S group than the F group. The VAS scores in the S group were significantly lower than those in the F group at each time point. The Ramsay scores in the S group were significantly higher than those in the F group at each time point. The cerebral oxygen saturation (SctO₂) levels in both groups were significantly increased following anesthesia induction and intubation compared to that of the awake state (P < 0.05), and SctO₂ was significantly decreased during the surgery in both groups. The changes in SctO₂ levels were not significantly different between the two groups (P > 0.05). The SctO₂ level was significantly higher during surgery than that after intubation. Compared with the F group, the relative value of SctO₂ decline in the S group was smaller. Compared to the day before surgery, the Montreal Cognitive Assessment (MoCA) scores of both groups were significantly reduced after surgery. At 1 day post-surgery, the MoCA scores of the S group were significantly higher and the incidence of postoperative cognitive dysfunction (POCD) was significantly lower compared to the F group. POCD occurred in three patients (6.2%) in the S group, and the ratio was significantly lower than that in the F group (11.9%) (P < 0.05). It showed a consistent trend with the SctO₂ status during the surgery. The relative value of SctO₂ decline in the S group was significantly smaller than that in the F group. The reduction of cognitive function in the S group was significantly lower than that in the F group. These results indicate that the changes in SctO₂ are a good prediction of the incidence of POCD.

Analgesia-sedation in PICU and neurological outcome: a secondary analysis of long-term neuropsychological follow-up in meningococcal septic shock survivors*

OBJECTIVES

To investigate whether analgesic and sedative drug use during PICU treatment is associated with long-term neurodevelopmental outcome in children who survived meningococcal septic shock.

DESIGN

This study concerned a secondary analysis of data from medical and psychological follow-up of a cross-sectional cohort of all consecutive surviving patients with septic shock and purpura requiring intensive care treatment between 1988 and 2001 at the Erasmus MC-Sophia Children's Hospital. At least 4 years after PICU admission, these children showed impairments on several domains of neuropsychological functioning. In the present study, type, number, and dose of sedatives and analgesics were retrospectively evaluated.

SETTING

Tertiary care university hospital.

PATIENTS

Seventy-seven meningococcal septic shock survivors (median age, 2.1 yr).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Forty-five patients (58%) received one or more analgesic and/or sedative drugs during PICU admission, most commonly benzodiazepines (n = 39; 51%), followed by opioids (n = 23; 30%). In total, 12 different kinds of analgesic or sedative drugs were given. The use and dose of opioids were significantly associated with poor test outcome on full-scale intelligence quotient (p = 0.02; Z = -2.28), verbal intelligence quotient (p = 0.02; Z = -2.32), verbal intelligence quotient subtests (verbal comprehension [p = 0.01; Z = -2.56] and vocabulary [p = 0.01; Z = -2.45]), and visual attention/executive functioning (Trial Making Test part B) (p = 0.03; Z = -2.17). In multivariate analysis adjusting for patient and disease characteristics, the use of opioids remained significant on most neuropsychological tests.

CONCLUSIONS

The use of opioids during PICU admission was significantly associated with long-term adverse neuropsychological outcome independent of severity of illness scores in meningococcal septic shock survivors.

Anesthetic management of the patient with epilepsy or prior seizures

PURPOSE OF REVIEW

Epilepsy is a clinical disorder of paroxysmal recurring seizures, the diagnosis excluding alcohol or drug withdrawal seizures or such recurring exogenous events as repeated insulin-induced hypoglycemia. Epilepsy has a profound impact on each individual diagnosed with this disease.

RECENT FINDINGS

New antiepileptic drugs (AEDs) have been a major change in the approach to management of patients with epilepsy. These drugs tend to have fewer significant drug interactions and less severe side effects. Nonetheless, first-generation AEDs are still widely used. Propofol and desflurane have reliable anticonvulsant effects, whereas remifentanil in larger doses and sevoflurane appear to support epileptiform activity, although the clinical significance of these observations is unclear.

SUMMARY

The primary concerns for providing anesthesia to the patient with epilepsy are the capacity of anesthetics to modulate or potentiate seizure activity and the interaction of anesthetic drugs with AEDs. Proconvulsant and anticonvulsant properties have been reported for virtually every anesthetic such that these properties become elements of the anesthetic plan in the patient with epilepsy. Moreover, AEDs have many physiologic and pharmacologic effects that can have an impact on an anesthetic.

Monitoring and intraoperative management of elevated intracranial pressure and decompressive craniectomy

There are numerous clinical scenarios wherein a critically ill patient may present with neurologic dysfunction. In a general sense these scenarios often involve ischemia, trauma, or neuroexcitation. Each of these may include a period of decreased cerebral perfusion pressure, usually due to elevated intracranial pressure (ICP), eventually compromising cerebral blood flow sufficiently to produce permanent neuronal loss, infarction, and possibly brain death. Elevated ICP is thus a common pathway for neural demise and it may arise from a variety of causes, many of which may result in a neurosurgical procedure intended to ameliorate the impact or etiology of elevated ICP.

Remifentanil-induced cerebral blood flow effects in normal humans: dose and ApoE genotype

BACKGROUND

Opioids have been linked to limbic system activation and, in animals, to neurotoxicity. Limbic system nonpharmacologic activation patterns have been linked to the Apolipoprotein E (ApoE) allelic distribution. We tested the hypothesis that, in the absence of surgery, small doses of remifentanil produce limbic system activation in humans which varies with dose and ApoE genotype.

METHODS

Twenty-seven ASA I-II volunteers received a remifentanil (Ultiva) infusion at four sequentially increasing doses: 0, 0.05, 0.1, and 0.2 microg x kg(-1) x min(-1) while receiving 100% oxygen. Cerebral blood flow (CBF) was measured at each dose globally and in the amygdala, cingulate, hippocampus, insula, and thalamus regions by pulsed arterial spin labeling magnetic resonance imaging. ApoE single nucleotide polymorphisms were determined in each subject.

RESULTS

Significant dose-related CBF increases, without correction for Paco(2), were detected in all areas. After normalizing for global CBF to correct for Paco(2) effects, the remifentanil-mediated increased CBF in the cingulate persisted, with decreased flow occurring in the hippocampus and amygdala. All these Paco(2)-corrected effects were reversed in the presence of the ApoE4 polymorphism.

CONCLUSION

Remifentanil at sedative doses produces both activating and depressing effects in various limbic system structures. The cingulate cortex seems to have the most susceptibility to remifentanil activation, and ApoE4 seems to produce relative activation of the hippocampus and amygdala.

Modulation of cerebral microvascular permeability by endothelial nicotinic acetylcholine receptors

Nicotine increases the permeability of the blood-brain barrier in vivo. This implies a possible role for nicotinic acetylcholine receptors in the regulation of cerebral microvascular permeability. Expression of nicotinic acetylcholine receptor subunits in cerebral microvessels was investigated with immunofluorescence microscopy. Positive immunoreactivity was found for receptor subunits alpha3, alpha5, alpha7, and beta2, but not subunits alpha4, beta3, or beta4. Blood-brain barrier permeability was assessed via in situ brain perfusion with [14C]sucrose. Nicotine increased the rate of sucrose entry into the brain from 0.3 +/- 0.1 to 1.1 +/- 0.2 microl.g(-1).min(-1), as previously described. This nicotine-induced increase in blood-brain barrier permeability was significantly attenuated by both the blood-brain barrier-permeant nicotinic antagonist mecamylamine and the blood-brain barrier-impermeant nicotinic antagonist hexamethonium to 0.5 +/- 0.2 and 0.3 +/- 0.2 microl.g(-1).min(-1), respectively. These data suggest that nicotinic acetylcholine receptors expressed on the cerebral microvascular endothelium mediate nicotine-induced changes in blood-brain barrier permeability.

Opioid neurotoxicity: comparison of morphine and tramadol in an experimental rat model

Histopathologic changes in rat brain due to chronic use of morphine and/or tramadol in progressively increased doses were investigated in this study. Thirty male Wistar rats (180-220 g) were included and divided into three groups. Normal saline (1 ml/kg) was given intraperitoneally as placebo in the control group (n = 10). Morphine group (n = 10) received morphine intraperitoneally at a dose of 4 mg/kg/day for the first 10 days, 8 mg/kg/day between 11-20 days, and 12 mg/kg/day between 21-30 days. The tramadol group (n = 10) received the drug intraperitoneally at doses of 20, 40, and 80 mg/kg/day in the first, second, and the third 10 days of the study, respectively. All rats were decapitated on the 30th day and the brain was removed intact for histology. The presence and the number of red neurons, which are a histologic marker of apoptosis, were investigated in the parietal, frontal, temporal, occipital, entorhinal, pyriform, and hippocampal CA1, CA2, CA3 regions. Red neurons were found in morphine and tramadol groups but not in the control group. The total number of red neurons was not different in morphine and tramadol groups, but the numbers of red neurons were significantly higher in the temporal and occipital regions in tramadol group as compared with the morphine group (p < .05). In conclusion, chronic use of morphine and/or tramadol in increasing doses is found to cause red neuron degeneration in the rat brain, which probably contributes to cerebral dysfunction. These findings should be taken into consideration when chrome use of opioids is indicated.

The neuropathologic effects in rats and neurometabolic effects in humans of large-dose remifentanil

Given in clinically relevant large doses to rats, mu-opioids produce limbic system hypermetabolism and histopathology. This investigation extends these observations, in both rats and humans, for the short-acting drug remifentanil, which allows more precise control and assessment of the effects of duration of opioid exposure. We performed two series of experiments: one in rats for neuropathologic effects and the second in humans for neurometabolic effects. Fifty mechanically ventilated rats received saline solution or remifentanil 20-160 microg x kg(-1) x min(-1) for 3 h, followed by neuropathologic evaluation 7 days later. Four volunteers underwent induction of anesthesia and endotracheal intubation with propofol and rocuronium administration followed by remifentanil infusion at 1-3 microg x kg(-1) x min(-1) with positron emission tomography evaluation of cerebral metabolic rate for glucose. In rats, dose-related electroencephalogram activation was evident and 19 of 40 remifentanil-treated rats showed brain damage, primarily in the limbic system (P < 0.01). In humans, cerebral metabolic rate for glucose in the temporal lobe increased from 6.29 +/- 0.32 to 7.68 +/- 1.05 mg x 100 g(-1) x min(-1) (P < 0.05). These data indicate that prolonged large-dose remifentanil infusion is neurotoxic in rats with congruent metabolic effects with brief infusion in humans and suggest that some adverse effects reported in rats may be clinically relevant.

IMPLICATIONS

This study demonstrates dose-related remifentanil neurotoxicity in physiologically controlled rats with congruent brain metabolic effects in four humans undergoing positron emission tomography evaluation during brief large-dose remifentanil anesthesia. These data suggest that some adverse effects reported in rats may be clinically relevant.

Phenytoin, midazolam, and naloxone protect against fentanyl-induced brain damage in rats

In previous studies, large-dose fentanyl produced electrographic seizure activity and histologically evident brain damage. We assessed whether fentanyl-induced brain damage is attenuated by using anticonvulsant drugs. Using halothane/nitrous oxide anesthesia, 40 Sprague-Dawley rats underwent tracheal intubation, arterial and venous cannulation, and insertion of biparietal electroencephalogram electrodes and a rectal temperature probe. Halothane was discontinued. The dose of IV fentanyl shown previously to cause maximal brain damage was given to all animals and N(2)O was discontinued. Control rats were given fentanyl only. Rats in the three study groups also received midazolam, phenytoin, or N(2)O/naloxone. After characteristic seizure activity began with fentanyl loading the study drug was started. After a 2-h infusion, wounds were closed, and animals recovered overnight and underwent cerebral perfusion-fixation. Neuropathologic alterations were ranked on a scale of 0-5 for both neuronal death (0 = normal, 5 = more than 75% neuronal death) and for malacia. Significantly fewer rats in the N(2)O/Naloxone, Phenytoin, and Midazolam Groups sustained any brain damage compared with controls. Protection against opioid neurotoxicity is achieved with midazolam, naloxone, and phenytoin. If opioid neurotoxicity is clinically relevant, a small change in anesthetic practice might reduce any potential neurologic morbidity.

IMPLICATIONS

Narcotics in large doses can cause brain damage in rats. This brain damage is attenuated by a narcotic antagonist, a sedative, and an antiepileptic drug.