Epileptiform electroencephalogram during mask induction of anesthesia with sevoflurane

Emergence Delirium in Children: Many Questions, Few Answers

The introduction of a new generation of inhaled anesthetics into pediatric clinical practice has been associated with a greater incidence of ED, a short-lived, but troublesome clinical phenomenon of uncertain etiology. A variety of anesthesia-, surgery-, patient-, and adjunct medication-related factors have been suggested to play a potential role in the development of such an event. Restless behavior upon emergence causes not only discomfort to the child, but also makes the caregivers and parents feel unhappy with the quality of recovery from anesthesia. Although the severity of agitation varies, it often requires additional nursing care, as well as treatment with analgesics or sedatives, which may delay discharge from hospital. To reduce the incidence of this adverse event, it is advisable to identify children at risk and take preventive measures, such as reducing preoperative anxiety, removing postoperative pain, and providing a quiet, stress-free environment for postanesthesia recovery. More clinical trials are needed to elucidate the cause as well as provide effective treatment.

Vagal Nerve Stimulation: Overview and Implications for Anesthesiologists

Vagal nerve stimulation is an important adjunctive therapy for medically refractory epilepsy and major depression. Additionally, it may prove effective in treating obesity, Alzheimer's disease, and some neuropsychiatic disorders. As the number of approved indications increases, more patients are becoming eligible for surgical placement of a commercial vagal nerve stimulator (VNS). Initial VNS placement typically requires general anesthesia, and patients with previously implanted devices may present for other surgical procedures requiring anesthetic management. In this review, we will focus on the indications for vagal nerve stimulation (both approved and experimental), proposed therapeutic mechanisms for vagal nerve stimulation, and potential perioperative complications during initial VNS placement. Anesthetic considerations during initial device placement, as well as anesthetic management issues for patients with a preexisting VNS, are reviewed.

Repeat episodes of severe muscle rigidity in a child receiving sevoflurane

We report on a patient who developed two episodes of severe muscle rigidity, increased endtidal CO2 and increased creatine phosphate kinase associated with sevoflurane anesthesia. Dysrhythmias and hyperthermia were not observed and dantrolene was not administered. Genetic testing for the 17 known mutations associated with malignant hyperthermia (MH) was negative. Although we cannot rule out MH or other neuromuscular diseases we suggest that this rare event may be a direct effect of sevoflurane.

Cerebral cortical effects of desflurane in sheep: comparison with isoflurane, sevoflurane and enflurane

BACKGROUND

Different volatile anesthetic agents have differing propensities for inducing seizures. A measure of the predilection to develop seizures is the presence of interictal spike discharges (spikes) on the electrocorticogram (ECoG). In this study, we investigated the propensity of desflurane to induce cortical spikes and made a direct objective comparison with enflurane, isoflurane, and sevoflurane. The ECoG effects of desflurane have not been previously reported.

METHODS

After establishment of invasive monitoring and a parasagittal array of eight electrodes to record the ECoG; eight adult merino sheep were given a series of short inhalational anesthetics (using desflurane, enflurane, sevoflurane and isoflurane); each titrated to ECoG burst suppression. Anesthetic effect was estimated by the effects on the approximate entropy of the ECoG. The effect of anesthetic on the spike-rate in the ECoG was analyzed using a non-linear mixed-effect method with a sigmoid Emax model.

RESULTS

A similar 'depth of anesthesia' was achieved for each agent, as estimated by the approximate entropy. The mean (SD) values of Emax for the spike-rate vs. approximate entropy relationship were desflurane 0.5 (0.9), enflurane 17.2 (4.0), isoflurane 0.7 (1.2), and sevoflurane 5.3 (1.2) spikes/min. The spike rate caused by desflurane was similar to isoflurane and significantly lower than that of enflurane (P < 0.001), and sevoflurane (P = 0.009).

CONCLUSION

Desflurane induces minimal cerebral cortical spike activity when administered to burst suppression, consistent with its low propensity for inducing seizures in non-epileptic brains. The agents can be ranked by their relative ability to cause spike activity: enflurane >> sevoflurane > isoflurane = desflurane.

Method for the automatic detection of epileptiform waveforms in sevoflurane-induced anesthesia EEG

Sevoflurane is a volatile anesthetic which is reported to cause epileptiform EEG changes together with undesired symptoms such as convulsions. In this paper, an algorithm for the automatic detection of these EEG changes is presented which could enable safer induction of anesthesia with sevoflurane by informing the clinicians about the epileptiform EEG. EEG was recorded from 60 healthy female patients during sevoflurane anesthesia. A neurophysiologist classified the EEG waveforms. Each anesthesia period lasted 6 minutes. 48 signal features were extracted from the raw EEG. 5-sec segments of EEG were classified based on the extracted features using a decision tree with a logistic regression based decisions and the classification results were compared to the neurophysiologist's classifications. Awake EEG was recognized with 69%/96% (sensitivity/specificity), Burst suppression with 56%/98%, Epileptiform EEG with 83%/87%, normal slow anesthesia EEG with 86%/64%, slow anesthesia EEG with monophasic pattern with 65%/80%, and slow anesthesia EEG with monophasic pattern and spikes with 54%/84%

Paediatric anaesthesia and inhalation agents

Inhalation agents are amongst the mainstays of paediatric anaesthesia, as children are often induced by mask before venous access is obtained. Children do not like needles and obtaining venous access in an awake and moving child can be very demanding. Safety aspects are of particular importance in paediatric anaesthesia. Therefore, the possibility of monitoring end-tidal concentrations facilitates correct dosing in all patients, from the preterm infant weighing less than 1000 g to the adult-sized adolescent. For induction, sevoflurane has nearly universally replaced halothane, leading to increased cardiovascular safety. The main disadvantages of inhalation agents, especially sevoflurane and desflurane, are delirious behaviour and agitated states during emergence. In addition, there remains uncertainty regarding the relevance of the cerebral stimulating pattern of some of these agents. Inhalation anaesthesia has a long tradition, whereas the experience with propofol is comparatively small. The incidence and clinical relevance of the propofol infusion syndrome during clinical anaesthesia are still unknown. Inhalation anaesthesia is still considered to be the gold standard by the overwhelming majority of paediatric anaesthetists world-wide, however, intravenous techniques can be an attractive alternative in specific clinical situations.

The Effects of Sevoflurane and Hyperventilation on Electrocorticogram Spike Activity in Patients with Refractory Epilepsy

We investigated the effects of sevoflurane and hyperventilation on intraoperative electrocorticogram (ECoG) spike activity in 13 patients with intractable epilepsy. Grid electrodes were placed on the brain surface and ECoG was recorded under the following conditions: 1) 0.5 minimal alveolar anesthetic concentration (MAC) sevoflurane, 2) 1.5 MAC sevoflurane, and 3) 1.5 MAC sevoflurane with hyperventilation. The number of spikes per 5 min and the percentage of leads with spikes were assessed in each condition. In 4 patients with chronically implanted-subdural electrodes, the leads with seizure onset and with spikes during the interictal periods in the awake state were compared with those during sevoflurane anesthesia at 0.5 MAC and 1.5 MAC. The number of spikes and the percentage of leads with spikes were significantly more under 1.5 MAC sevoflurane anesthesia compared with those under 0.5 MAC sevoflurane (P < 0.05). The induction of hyperventilation significantly increased the number of spikes and percentage of leads with spikes (P < 0.05). With 0.5 MAC sevoflurane, the leads with spikes were similar to those at seizure onset in the awake state, whereas with 1.5 MAC sevoflurane, spikes were similar to those occurring during interictal periods in the awake state. These results indicate that sevoflurane and hyperventilation can affect the frequency and extent of ECoG spike activity in patients with intractable epilepsy. Careful attention should be paid to the concentration of sevoflurane used and ventilatory status when intraoperative EcoG is used to localize epileptic lesions.

IMPLICATIONS

Electrocorticogram can be used to define the location and extent of epileptic foci during epilepsy surgery. However, electrocorticogram can be affected by anesthetic technique. The present study found that sevoflurane concentration and hyperventilation affected the frequency and the extent of electrocorticogram spike activity in epileptic patients.

A Rapid Increase in the Inspired Concentration of Desflurane Is Not Associated with Epileptiform Encephalogram

The large inspired concentration of sevoflurane (S) during mask induction of anesthesia can induce epileptiform electroencephalogram (EEG) associated with tachycardia. Tachycardia is also seen when the concentration of desflurane (D) is abruptly increased. It is not known whether this is associated with epileptiform EEG similar to S. We studied EEG and heart rate (HR) during rapidly increased concentrations of S or D in 31 females during the postintubation period of anesthesia. Anesthesia was induced with propofol and remifentanil, and the tracheas were intubated. Patients were randomized to receive either S or D in nitrous oxide-oxygen mixture after intubation, at a small dose first. After 10 min, S or D vaporizer was advanced to the highest reading of the vaporizer (7% for S, 18% for D) for 5 min. HR and EEG were recorded. Epileptiform EEG activity was recorded in eight of 15 patients in group S and in none in group D (P < 0.05). HR increased in both groups. In group S, HR increased gradually and the highest HR value was 84 bpm at 5 min after the increase in sevoflurane concentration. In group D, HR increased to 93 bpm 2 min after the increase in desflurane concentration (no significant difference, S versus D). A rapid increase in the concentration of S frequently induces epileptiform EEG during normoventilation. Tachycardia during increasing concentrations of D is not associated with epileptiform EEG.

IMPLICATIONS

A rapid increase in the concentration of sevoflurane induces epileptiform encephalogram (EEG) with tachycardia. A rapid increase in the concentration of desflurane also induces tachycardia but is not associated with epileptiform EEG.

Sevoflurane (12% and 8%) inhalational induction in children

BACKGROUND

Sevoflurane induction of anesthesia is frequently used in children. Rapidly performed inhalational induction may reduce excitation during early anesthesia. Increasing the total anesthetic MAC delivered to patients can be achieved by increasing volatile concentration or adding nitrous oxide. The latter reduces inspired oxygen concentration delivered, which may not be desirable. Even 8% sevoflurane induction is associated with excitation. A system capable of delivering 12% sevoflurane using two tandem vaporizers has been developed.

METHODS

A randomized double blind study was undertaken to assess whether 12% sevoflurane offered any advantage over 8% in time and quality of induction. Sixty children aged 5-10 years were recruited and received either 12 or 8% sevoflurane. Time to loss of eyelash reflex, central pupils, incidence of adverse events, induction quality, systolic blood pressure and heart rate were recorded.

RESULTS

Twelve percent sevoflurane reduced time to loss of eyelash reflex compared with 8% [mean (sd): 35 (12) and 46 (14) P<0.05], but the reduction was only 10% higher than the error in the measurement (assessment every 10 s). Twelve percent sevoflurane offered significantly better quality of induction (P<0.05). There was no difference in cardiovascular stability between groups, although heart rate rose significantly in both groups. Maintaining sevoflurane at 12% for 4 min caused significant amounts of apnea (69% with 12% and 38% with 8%, P<0.05).

CONCLUSION

Twelve percent sevoflurane offers a smoother anesthesia induction than 8% in children of this age with no additional consequences for the cardiovascular system.

Sevoflurane and epileptiform EEG changes

Sevoflurane has become the volatile agent of choice for inhalation induction of anesthesia. Hemodynamic stability and lack of respiratory irritation have justified its rapid extension to pediatric inhalation induction. The epileptogenic potential of sevoflurane has been suspected since the first case reports of abnormal movements in children without a history of epilepsy. The objectives of this short review are to: (i) analyze clinical and electroencephalographic (EEG) features supporting epileptogenic activity of sevoflurane, (ii) identify factors which may modulate that activity, and (iii) suggest guidelines of clinical practice to limit expression of this epileptiform phenomenon, which has thus far unknown morbidity. The use of sevoflurane may be associated with cortical epileptiform EEG signs, usually without clinical manifestation. No lasting neurological or EEG sequelae have been described thus far, and the potential morbidity of this epileptogenic effect is unknown. The use of sevoflurane in children, with its remarkable cardiovascular profile, should include a number of precautions. Among them, the limitation of the depth of anesthesia is essential. The wide use of cerebral function monitoring (the most simple being the EEG), may permit optimization of sevoflurane dose and avoidance of burst suppression and major epileptiform signs in fragile subjects, notably the very young and the very old.

Effects of subanaesthetic and anaesthetic doses of sevoflurane on regional cerebral blood flow in healthy volunteers. A positron emission tomographic study

BACKGROUND

We tested the hypothesis that escalating drug concentrations of sevoflurane are associated with a significant decline of cerebral blood flow in regions subserving conscious brain activity, including specifically the thalamus.

METHODS

Nine healthy human volunteers received three escalating doses using 0.4%, 0.7% and 2.0% end-tidal sevoflurane inhalation. During baseline and each of the three levels of anaesthesia one PET scan was performed after injection of . Cardiovascular and respiratory parameters were monitored and electroencephalography and bispectral index (BIS) were registered.

RESULTS

Sevoflurane decreased the BIS values dose-dependently. No significant change in global cerebral blood flow (CBF) was observed. Increased regional CBF (rCBF) in the anterior cingulate (17-21%) and decreased rCBF in the cerebellum (18-35%) were identified at all three levels of sedation compared to baseline. Comparison between adjacent levels sevoflurane initially (0 vs. 0.2 MAC) decreased rCBF significantly in the inferior temporal cortex and the lingual gyrus. At the next level (0.2 MAC vs. 0.4 MAC) rCBF was increased in the middle temporal cortex and in the lingual gyrus, and decreased in the thalamus. At the last level (0.4 MAC vs. 1 MAC) the rCBF was increased in the insula and decreased in the posterior cingulate, the lingual gyrus, precuneus and in the frontal cortex.

CONCLUSION

At sevoflurane concentrations at 0.7% and 2.0% a significant decrease in relative rCBF was detected in the thalamus. Interestingly, some of the most profound changes in rCBF were observed in structures related to pain processing (anterior cingulate and insula).

Change in Bispectral Index During Epileptiform Electrical Activity Under Sevoflurane Anesthesia in a Patient with Epilepsy

We observed abnormal fluctuation in Bispectral Index (BIS) caused by repeated alternations between two electroencephalographic (EEG) waveform patterns in a patient with a recent history of epileptic seizure under sevoflurane anesthesia. The repetitive development of the abnormal EEG changes (slow delta with or without spike) and the fluctuation in BIS disappeared almost immediately after administration of anticonvulsants. BIS may give useful information not only on the sedative-hypnotic state, but also on the development of and recovery from abnormal epileptiform EEG activity.

IMPLICATIONS

During epileptiform electroencephalographic activity (EEG), the Bispectral Index shows an abnormal fluctuation caused by repeated abrupt alterations between normal EEG and abnormal epileptiform EEG patterns.

The bispectral index does not correlate with clinical signs of inhalational anesthesia during sevoflurane induction and arousal in children

PURPOSE

Validation of the bispectral index (BIS) in children requires correlating BIS with several levels of sedation, hypnosis and anesthesia. Our purpose was to compare BIS values with objective assessments of the level of hypnosis in children. We postulated that BIS predicted the level of anesthesia during induction and emergence in children.

METHODS

In a prospective observational study, we evaluated the BIS monitor in 87 children (ages: 0.3 to 14 yr) ASA physical status I-II undergoing general surgery under sevoflurane and nitrous oxide. Clinical signs of inhalational anesthesia (CSA), the motor response to surgical incision and signs of arousal were used as indicators of the depth of anesthesia. CSA and BIS measurements were paired every minute during induction and emergence until arousal.

RESULTS

CSA scores decreased during induction and increased during emergence (P < 0.001) and correlated with changes in sevoflurane concentrations (r = -0.46; P < 0.001). BIS was associated with changes in CSA scores during induction (r = 0.49; P < 0.01) and emergence (r = 0.62; P < 0.01), but the ranges of individual BIS values overlapped several levels of hypnosis. A BIS value greater than 50 had a positive predictive value of 25% for distinguishing between responders and non-responders to surgical incision. A BIS score equal or greater than 72 had a predictive value of 63% for discriminating between pre-arousal and arousal.

CONCLUSIONS

BIS correlates with several levels of hypnosis during inhalational induction and emergence in children, but individual BIS values show large inter-individual variability. The BIS monitor identified the physiological changes associated with arousal and distinguished the effects of preoperative sedation during emergence. The use of movement as an endpoint of hypnosis during surgical stimulation does not correlate with BIS values in children. The large inter-individual variability of BIS at different levels of anesthetic depth may limit the applicability of BIS to pediatric anesthesia.

Les nouveaux agents volatils halogénés en neuro-anesthésie : quelle place pour le sévoflurane ou le desflurane ?

The effects on cerebral circulation and metabolism of sevoflurane and desflurane are largely comparable to isoflurane. Both induce a direct vasodilation of the cerebral vessels, resulting in a less pronounced decrease in cerebral blood flow compared to the decrease in cerebral metabolism. This direct vasodilation seems to be dose-dependent and more pronounced for desflurane > isoflurane > sevoflurane. Many reports suggest luxury perfusion at high concentrations of desflurane. Sevoflurane maintains intact cerebral autoregulation up to 1.5 MAC. Desflurane induces a significant impairment in autoregulation, with a completely abolished autoregulation at 1.5 MAC. Both sevoflurane and desflurane (up to 1.5 MAC) maintain normal CO(2) regulation. As to their effect on final intracranial pressure (ICP), both sevoflurane and desflurane revealed no increases in ICP. However, compared to intravenous hypnotics, subdural ICP is higher with volatiles because of their tendency to increase cerebral swelling after dura opening (isoflurane > sevoflurane). Several case reports have noted seizure-like movements, as well as EEG recorded seizures during induction of sevoflurane anesthesia. Especially, in children during inhalational induction with hyperventilation at a high sevoflurane concentration, severe epileptiform EEG with a hyperdynamic response were observed, which urges for caution using inhalational sevoflurane induction in children for neurosurgical procedures. Neuroprotective properties (reduced neuronal death either by necrosis or apoptosis) have been attributed to all volatile agents. However, these neuroprotective effects have been described in experimental or animal models, so their possible effect on humans remains to be proven.

Convulsions on anaesthetic induction with sevoflurane in young children

Increased worldwide use for paediatric anaesthesia of the volatile anaesthetic agent sevoflurane has mainly resulted from its low blood-gas partition coefficient and low airway irritability, providing smooth conditions for rapid induction of anaesthesia. Nevertheless, there are several clinical and experimental reports suggesting a correlation between exposure to sevoflurane and generalized clonic or tonic seizure activity. We report two clinical episodes of convulsions associated with the induction of sevoflurane anaesthesia in young children. CASE 1: during induction of anaesthesia with sevoflurane by facemask in a 3-year-old healthy boy, there were symmetrical clonic seizure-like movements of the upper extremities for 60 s. CASE 2: on re-induction of anaesthesia with sevoflurane because of profuse bleeding following nasal adenoidectomy in a 4-year-old healthy girl with a family history of epilepsy, there were symmetrical tonic and clonic seizure-like movements for 30-40 s in the upper and lower extremities. Both episodes ceased spontaneously. Although no EEG was recorded, it cannot be excluded that both episodes resulted from seizure activity within the CNS. Based on our observations and reports by others we suggest that, until further notice, sevoflurane should be avoided or at least used cautiously in patients where clinical epileptic activity has been verified or is strongly suspected.

Sevoflurane: an ideal agent for adult day-case anesthesia?

Sevoflurane has several properties which make it potentially useful as a day case anaesthetic. Following induction of anaesthesia with propofol, awakening from sevoflurane is faster compared to isoflurane, faster or similar compared to propofol and comparable (in the majority of studies) to desflurane. Subsequent recovery and discharge is generally similar following all agents. Sevoflurane may also be used to induce anaesthesia, which is generally well-received and causes less hypotension and apnoea compared to propofol. When used as a maintenance anaesthetic, the incidence of postoperative nausea and vomiting after sevoflurane is comparable to other inhaled anaesthetics, but this complication appears more common after inhaled inductions. The tolerability and low solubility of sevoflurane facilitate titration of anaesthesia and may reduce the need for opioid analgesia, which in turn may limit the occurrence of nausea and vomiting.

The effect of isoflurane and sevoflurane on cerebrocortical presynaptic Ca2+ and protein kinase C activity

Protein kinase C (PKC) is an important enzyme involved in the regulation of neurotransmission and might also be important in the mediation of ischemic neuronal death. PKC has been implicated as a target of volatile anesthetics as well as in anesthetic protection against ischemia. The present study tested the effect of isoflurane and sevoflurane, both used in neuroanesthetic practice, on presynaptic free cytosolic Ca2+ ([Ca2+](i)) and PKC activity. To measure [Ca2+](i) and PKC activation simultaneously, rat synaptosomes, mostly containing presynaptic terminals, were loaded with the fluorescent probes fura-2 and fim-1, respectively. The synaptosomes were exposed to either isoflurane or sevoflurane in concentrations corresponding to 1 and 2 MAC values in rats, both in Ca2+-containing and Ca2+-free medium. After 8 minutes of anesthetic exposure, 1 mM 4-aminopyridine was added to induce membrane depolarization. Isoflurane 1 and 2 MAC increased the basal PKC activity after 8 minutes in Ca2+-containing medium by 15.1% (3.6%) and 30.5% (5.5%) compared with control, respectively [mean (SEM); n = 9, both values P < 0.05]. Sevoflurane 2 MAC transiently decreased but thereafter increased the PKC activity (P < 0.05). In Ca2+ -free medium sevoflurane attenuated the PKC activity (P < 0.05). The anesthetics did not alter the depolarization-evoked enzyme activation. Furthermore, 2 MAC of both isoflurane and sevoflurane increased the basal- and attenuated the depolarization-evoked increase in [Ca2+](i) (P < 0.05). The present study supports the hypotheses that volatile anesthetics affect presynaptic PKC activity and that the anesthetic effect on enzyme activation seems to be related to an increase in [Ca2+](i).

Sevoflurane provides faster recovery and postoperative neurological assessment than isoflurane in long-duration neurosurgical cases

Sevoflurane (SEVO) provides faster emergence than isoflurane (ISO). This advantage is thought to magnify with increased duration of exposure. In addition, SEVO has several of the characteristics of an ideal neuroanesthetic. We designed a prospective, randomized, double-blinded study to compare the recovery profile of SEVO versus ISO in neurosurgery. Sixty patients undergoing intracranial surgery were enrolled. They were randomized to receive SEVO or ISO in 40% oxygen as part of a balanced anesthetic regimen. The anesthetic concentration (0.5 to 1.0 minimum alveolar anesthetic concentration [MAC]) was adjusted to maintain mean arterial blood pressure within 20% of the preinduction baseline. At the end of the surgery, neuromuscular blockade was reversed, anesthetics were discontinued without prior tapering, and fresh gas flow was increased to 10 L/min. Recovery end-points were measured as the time from closure of the anesthetic vaporizer. Mean MAC-hours were identical in both groups (4.7). Patients in the SEVO group demonstrated a shorter time to emergence (P = 0.02) and for response to command (squeeze hand, P = 0.03; move feet, P = 0.01). Patients in the SEVO group obtained a Glasgow coma scale score of >/=10 5 min before patients in the ISO group (P = 0.04). Obtaining an early neurological examination can be critical in neurosurgical patients. The observed difference in emergence between SEVO and ISO could therefore be of clinical importance.

IMPLICATIONS

The low-solubility anesthetic, sevoflurane, provides faster recovery and postoperative neurological assessment than isoflurane after long-duration (4.7 MAC-h) intracranial surgery.

Sevoflurane reduces synaptic glutamate release in human synaptosomes

Volatile anesthetics reduce excitatory synaptic transmission in the mammalian brain. In the present study, the effect of sevoflurane on synaptic glutamate release, free cytosolic Ca2+ ([Ca2+]i), and glutamate uptake was investigated using isolated presynaptic terminals prepared from human cerebral cortex. The tissue was obtained from standard temporal lobe specimens removed because of epilepsy. The glutamate release and [Ca2+]i was measured as the fluorescence of nicotinamide adenine dinucleotide phosphate (NADPH) and fura-2, respectively. The uptake of radiolabeled glutamate was measured in a beta-scintillation counter. Membrane depolarization with 4-aminopyridine for three minutes evoked a Ca2+-dependent glutamate release of 3.4 +/- 0.5 nmol/mg. Sevoflurane 2.5 and 4.0% attenuated the evoked release by 45 and 55%, respectively. The evoked increase in [Ca2+]i was not significantly altered by the anesthetic agent. The uptake studies were performed in the high-affinity area, and Km was calculated to 19.3 +/- 5.7 x 10(-6) M and Vmax to 5.7 +/- 1.0 micromol g(-1) min(-1). The Km and Vmax values were not significantly altered by sevoflurane 2.5%. These results demonstrate that sevoflurane in the human brain reduces Ca2+-dependent glutamate release. The exact mode of action is still to be resolved.

Motion sickness and postoperative vomiting in children

BACKGROUND

Motion sickness is considered an important risk factor for postoperative nausea and vomiting in children. The aim of this study was to verify the impact of motion sickness on the incidence of vomiting after routine surgery in children, and to compare the incidence of vomiting, after combined regional/general anaesthesia, using either halothane or sevoflurane.

METHODS

We prospectively studied 420 children (369 males and 51 females) who received general anaesthesia and inguinal field block for common paediatric surgery. The children were randomly allocated into one of two groups (halothane or sevoflurane). In the 200 children in the first group (H), general anaesthesia was induced and maintained with halothane, whereas in the 220 children in the second group (S), anaesthesia was induced and maintained with sevoflurane.

RESULTS

There were 79 children with a prior history of motion sickness (MS+) and 341 without such a history (MS-). In the MS+ population, the incidence of vomiting was similar in both H and S groups, being around 33%. However, repeated episodes of vomiting in MS+ children were more frequent when halothane was used. In the MS- group, the incidence of vomiting was significantly greater in the H group (19%) than in the S group (8%).

CONCLUSIONS

In the postoperative period, we found that MS+ children vomit more than MS- children, regardless of the inhalation anaesthetic used. However, MS- children displayed a higher incidence of vomiting when halothane was used rather than sevoflurane.

Effects of sevoflurane on electrocorticography in patients with intractable temporal lobe epilepsy

Fentanyl-droperidol technique is the choice for epilepsy surgery. It requires intraoperative electrocorticography (ECoG), but a large dose of fentanyl is needed for this technique. On the other hand, sevoflurane reportedly may be beneficial for intraoperative ECoG. To reveal whether the combined technique with fentanyl and sevoflurane is beneficial for epilepsy surgery, we investigated ECoG in 10 patients with intractable temporal lobe epilepsy without sevoflurane, with 0.5 minimum alveolar concentration (MAC) sevoflurane, and with 1.5 MAC sevoflurane under fentanyl-based anesthesia. The mean number of spikes for 1 minute decreased from 38.3 to 14.1 after 1.5 MAC sevoflurane was induced, which was statistically significant ( P <.05). Our results showed that balanced technique with neurolepto-analgesia (NLA) and sevoflurane is not suitable for epilepsy surgery requiring intraoperative ECoG. When epilepsy surgeries are performed under sevoflurane anesthesia, it is important to consider that sevoflurane may suppress electric activities when it is used with other anesthetic agents.

[Automatic analysis of electroencephalogram: what is its value in the year 2000 for monitoring anesthesia depth?]

Spontaneous EEG has been proposed for monitoring depth of anaesthesia and adjusting anesthetic drugs doses. This review describes the main features of spontaneous EEG, the principles of EEG signal analysis used in anaesthesia, and the EEG effects of the different anesthetic drugs in adults and children. Then, the correlations between EEG parameters changes and clinical signs of anesthesia (loss of consciousness and memory, lack of movement and haemodynamic stability despite noxious stimulations) are analyzed. The best signal analysis technique available today for routine use seems to be bispectral analysis, which returns, in the available monitors, a single number called bispectral index or BIS. Based upon the recent literature, clinical uses, performances and limits of use of BIS are described and discussed.

Sevoflurane mask induction of anaesthesia is associated with epileptiform EEG in children

BACKGROUND

Sevoflurane inhalation induction of anaesthesia is widely used in paediatric anaesthesia. We have found that this method is frequently associated with epileptiform electroencephalogram (EEG) in adults, especially if controlled hyperventilation is used.

METHODS

We assessed EEG during sevoflurane inhalation induction in 31 children, aged 2-12 yr. Anaesthesia was induced with 8% sevoflurane in O2 in N2O 1:2. The patients were randomized to undergo controlled ventilation (CV group), or to breathe spontaneously (SB group) for 5 min. EEG was recorded as were noninvasive blood pressure and heart rate (HR). EEG recordings were classified by a clinical neurophysiologist.

RESULTS

Three different types of interictal epileptiform discharge were detected. Suppression with spikes (SSP) was found in 25% and 0% in the CV and SB groups, rhythmic polyspikes (PSR) in 44% and 20%, and periodic epileptiform discharges (PED) in 44% and 0% (P<0.01), respectively. The incidence of all different types of interictal epileptiform discharge (SSP+PSR+PED) was 88% and 20% (P<0.001), respectively. Epileptiform EEG was associated with increased heart rate and blood pressure during anaesthetic induction.

CONCLUSION

Both ventilation modes produced epileptiform EEG. With controlled ventilation, epileptiform discharges were seen in 88% of children. This warrants further studies of the suitability of this induction type in general, and especially in children with epilepsy.

Excitation phenomena during sevoflurane anaesthesia in children

The advantages of rapid induction of and emergence from sevoflurane anaesthesia may be more than offset by the frequent occurrence of agitation during induction and recovery, and a possible epileptogenic effect. The mechanisms and possible strategies to prevent these drawbacks are reviewed, on the basis of the most recent literature.

[Electroencephalographic effects of sevoflurane in pediatric anesthesia: a prospective study of 20 cases]

OBJECTIVE

To study electroencephalographic (EEG) changes in children during induction of anaesthesia with 8% sevoflurane.

PATIENTS

Twenty patients were consecutively included (ASA I-II; aged: 13-101 months).

MATERIAL AND METHOD

Prospective study; approved by the Ethics Committee; written informed consent obtained from parents; anaesthesia induced with 8% sevoflurane in oxygen; no premedication was given; to collect the EEG data, non-invasive electodes were installed before induction; EEG was recorded continuously and stored on a computer for later analyses (descriptive analysis).

RESULTS

Myoclonics movements were observed during induction of anaesthesia in two boys. Myoclonics movements stopped spontaneously without therapy. Epileptiform EEG activity (spikes and poly-spikes, burst suppression) was observed. In the 18 others cases, during sevoflurane induction, EEG changed rapidly with an increase in the range of beta activity (> 13 Hz) (n = 15) and in slow (< 8 Hz) and delta activity (< 4 Hz). In 14 patients, at time of laryngoscopy, the EEGs showed monophasic slow data activity (sharp high-voltage slow waves). Periods of EEG isoelectrical (burst suppression) were seen without spikes in four cases.

CONCLUSION

At 2 MAC, epileptiform EEG activity has been observed during sevoflurane anaesthesia. In a short group of patients, this raises the question of avoiding sevoflurane in patients who have a history of epilepsy.

Similar haemodynamic, respiratory and metabolic changes with the use of sevoflurane or halothane in children breathing spontaneously via a laryngeal mask airway

BACKGROUND

In preschool children, short-lasting surgical procedures are often performed under combined inhalational and regional anaesthesia with the child breathing spontaneously via a laryngeal mask airway (LMA). Despite widespread use, only limited data are available on haemodynamic, respiratory and metabolic effects of sevoflurane and halothane during LMA anaesthesia.

METHODS

In an open-label, randomised, controlled study, 49 children (aged 3-8 years) were allocated to receive either sevoflurane or halothane in 60% nitrous oxide. After insertion of the LMA, end-tidal concentrations of sevoflurane or halothane were maintained at 1 MAC with the child ventilating spontaneously throughout the entire procedure. Analgesia was provided by caudal block. Haemodynamic and respiratory parameters were recorded, and capillary blood-gas samples were obtained repeatedly.

RESULTS

Changes in heart rate (HR) and systolic blood pressure were similar in both groups during all observed periods, apart from a significantly higher increase in HR during inhalational induction with sevoflurane (P<0.05). Regression slope analysis during anaesthesia revealed a decrease of the respiratory rate of 5 breaths h-1 (P<0.001) and an increase of end-tidal PCO2 and capillary PCO2 of about 0.25 kPa h-1 (P<0.001), with no significant difference between the two groups. Base excess, calculated in capillary blood gas samples, did not change over time (P>0.5) in either group.

CONCLUSIONS

The use of approximately 1 MAC sevoflurane or halothane in 60% N2O in children breathing spontaneously via LMA resulted in comparable haemodynamic, respiratory and metabolic changes, and clinically relevant deteriorations did not occur during the 65-min study period.

[Epileptogenic drugs in anesthesia]

Most anaesthetics and analgesics have both pro- and anticonvulsant activity. The data in the literature should be analysed with respect to the patient population, the recording of epileptic activity and the method of EEG analysis. Among inhaled anaesthetics, isoflurane has strong anticonvulsant properties. In some circumstances, sevoflurane may induce an epileptic activity. With the exception of ketamine and etomidate, all intravenous hypnotics may be used for anesthesia of the epileptic patient. Midazolam is a potent anticonvulsant. Among narcotics, fentanyl and alfentanil may induce clinical or electroencephalographic seizures. Considering the large number of patients treated with these agents without any neurological adverse effect, the clinical relevance of these data is unclear. Neuromuscular blocking agents do not possess pro- or anticonvulsant properties.

[Anesthesia for epilepsy surgery]

Epilepsy is rather common, affecting 0.5 to 2% of the population. Numerous patients, particularly those resistant to the antiepileptic therapy, can be surgically treated after a thorough evaluation. Surgery for epilepsy can be carried out either under general or local anaesthesia with sedation. This second approach is reserved for the extirpation of foci localised in motor, sensory or language areas. During the preoperative anaesthetic evaluation, two specific points have to be taken into account: the psychological aspect and the antiepileptic medication. During the procedure, an electrocorticography with or without stimulation may be indicated, particularly when a perioperative stimulation is scheduled. Low doses of volatile agents are chosen, and no curare and large doses of benzodiazepines and barbiturates. Awakening takes place on the operation table for a rapid and reliable neurological evaluation. During procedures performed under local anaesthesia, the anaesthetist must be ready at any time to intubate the patient in order to secure the airway.

Sevoflurance: approaching the ideal inhalational anesthetic. a pharmacologic, pharmacoeconomic, and clinical review

Sevoflurane is a safe and versatile inhalational anesthetic compared with currently available agents. Sevoflurane is useful in adults and children for both induction and maintenance of anesthesia in inpatient and outpatient surgery. Of all currently used anesthetics, the physical, pharmacodynamic, and pharmacokinetic properties of sevoflurane come closest to that of the ideal anesthetic (200). These characteristics include inherent stability, low flammability, non-pungent odor, lack of irritation to airway passages, low blood:gas solubility allowing rapid induction of and emergence from anesthesia, minimal cardiovascular and respiratory side effects, minimal end-organ effects, minimal effect on cerebral blood flow, low reactivity with other drugs, and a vapor pressure and boiling point that enables delivery using standard vaporization techniques. As a result, sevoflurane has become one of the most widely used agents in its class.

Epileptiform EEG during sevoflurane mask induction: effect of delaying the onset of hyperventilation

BACKGROUND

Hyperventilation during sevoflurane-N2O-O2 mask induction in adults is associated with a hyperdynamic circulatory response and epileptiform electroencephalogram (EEG). We tested the hypothesis that delaying onset of hyperventilation will prevent severe (periodic) epileptiform EEG and hyperdynamic response.

METHODS

Thirty patients were randomized to receive either delayed (group D, n=15) or immediate (group I, n=15) onset of hyperventilation during sevoflurane (8% in N2O 50%) mask inhalation induction with single-breath method for unconsciousness. Fifteen patients were allowed to breathe spontaneously for 2 min after loss of consciousness and controlled hyperventilation (ETCO2 <4%) was started thereafter. In 15 patients controlled hyperventilation was started immediately after loss of consciousness. EEG was recorded, and mean arterial pressure (MAP) and heart rate (HR) registered.

RESULTS

Epileptiform EEG patterns were seen in 13 patients in group I and in 9 patients in group D (n.s.). Periodic epileptiform discharges (PED) tended to occur more often in group I (P=0.07). Heart rate and MAP were higher in group I than in group D from 2 min to 3 min (P < 0.05), and both HR and MAP rose significantly from the baseline in group I. In group D, HR but not MAP rose significantly from baseline.

CONCLUSION

Regardless of its timing, hyperventilation at a high sevoflurane concentration produced severe epileptiform EEG with a hyperdynamic response. PED tended to occur more often with immediate onset of hyperventilation.