Transient Hyperdynamic Response Associated with Controlled Hypocapneic Hyperventilation During Sevoflurane-Nitrous Oxide Mask Induction in Adults

Management and Anesthetic Considerations for Patients With Anomalous Aortic Origin of a Coronary Artery

The term "coronary artery anomalies" encompasses a large and heterogeneous group of disorders that may affect origin, intrinsic anatomy, course, location, and termination of the coronary arteries. With these different anatomies, presentation, symptoms, and outcomes are heterogeneous as well. While significant efforts are directed toward improving diagnosis and risk-stratification, best evidence-guided practices remain in evolution. Data about anesthetic management of patients with coronary anomalies are lacking as well. This review aims to provide the anesthesiologist with a better understanding of an important subgroup of coronary artery anomalies: anomalous aortic origin of a coronary artery. We will discuss classification, pathophysiology, incidence, evaluation, management, and anesthetic implications of this potentially fatal disease group.

Repetitive generalized seizure-like activity during emergence from sevoflurane anesthesia

PURPOSE

Sevoflurane-induced seizures are most often described during mask induction of anesthesia when high concentrations of the volatile agent are administered concomitant with alveolar hyperventilation. The occurrence of seizure-like activity during emergence from sevoflurane anesthesia has been rarely reported.

CLINICAL FEATURES

We describe a patient who developed several episodes of generalized tonic-clonic seizure-like activity during and immediately after emergence from sevoflurane anesthesia and discuss the potential factors that contributed to this unusual complication. The patient was treated with intravenous propofol, midazolam, and phenytoin and required intensive care management before his neurologic status stabilized.

CONCLUSION

The report emphasizes that sevoflurane is capable of producing excitatory central nervous system (CNS) phenomena in spite of causing primarily CNS depressant effects.

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.

[Occurrence of epileptiform crisis in child under sevoflurane anaesthesia]

A case report is presented of an unknown epileptic child, who developed convulsive movements during inhalation of 3.9% sevoflurane for 45 minutes associated with moderate hyperventilation. Epilepsy was discovered on the EEG, which was performed postoperatively.

Low alfentanil target-concentrations improve hemodynamic and intubating conditions during induction with sevoflurane

PURPOSE

To investigate the effects of different alfentanil target-concentrations on hemodynamics, respiration and conditions of tracheal intubation during an inhalation induction with 8% sevoflurane.

METHODS

In this prospective randomized open-label study, 40 ASA I adult patients received alfentanil at the following target-concentrations: zero (Group 0), 25 (Group 25), 50 (Group 50) and 75 ng*mL(-1) (Group 75), starting five minutes before induction of anesthesia with 8% sevoflurane in 50% nitrous oxide. The ease of intubation was determined on fixed criteria and scored; arterial pressure, heart rate and bispectral index (BIS) were recorded at one-minute intervals.

RESULTS

Times to allow tracheal intubation were shortened only in Group 75 (94 +/- 8 sec) as compared to Group 0 (140 +/- 11 sec, P < 0.05). BIS values, tracheal intubation scores and number of attempts were not different between groups. However, more patients suffered from apnea in Group 75. Heart rate and mean arterial pressure remained stable in Group 75 whereas they increased significantly in the three other groups. No patient suffered hypotension.

CONCLUSION

Adding alfentanil at a 75 ng*mL(-1) target-concentration during an inhalation induction with 8% sevoflurane in 50% nitrous oxide allows intubation slightly earlier and provides stable hemodynamic conditions but the incidence of apnea during induction is higher. Lower concentrations are of little clinical interest.

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.

Induction with propofol target-concentration infusion vs. 8% sevoflurane inhalation and alfentanil in hypertensive patients

Haemodynamic parameters during an inhalation induction with 8% sevoflurane were compared with those obtained with a target-controlled infusion of propofol in 50 hypertensive patients in a prospective randomised study. Heart rate and arterial pressure were recorded continuously. End-tidal sevoflurane and nitrous oxide concentration, SpO2 and bispectral index (BIS) were also collected from the beginning of anaesthesia until 8 min after tracheal intubation. Patients either received 4 mg.l-1 target-concentration propofol or performed a vital capacity inhalation of 8% sevoflurane in a high flow of oxygen (8 l.min-1) supplemented with 50% nitrous oxide at loss of consciousness. As soon as BIS was < 60, 20 microg.kg-1 alfentanil and 0.6 mg.kg-1 rocuronium were injected and orotracheal intubation was then performed 1 min later. Thereafter, the end-tidal concentration of sevoflurane was reduced to 1.3 minimum alveolar concentration (MAC). Hypotension was defined as a 30% decrease in arterial pressure and was treated with repeated 3-mg boluses of ephedrine. When 12 mg ephedrine was unable to correct hypotension, the concentration of propofol was reduced by 1 mg.l-1 and that of sevoflurane by 0.5%. Hypotension occurred in 22 patients in the sevoflurane group and 21 in the propofol group, and hypertension occurred in two and three patients in each group, respectively. The maximal reduction in mean (SD) arterial pressure was similar in the sevoflurane (45 (4) mmHg) and propofol (41.3 (2.6) mmHg) groups, as were the ephedrine requirements (9.6 (1.1) vs. 9.1 (1.1) mg, sevoflurane vs. propofol, p > 0.05), the duration of hypotension (276 (37) vs. 292 (38) s, sevoflurane vs. propofol, p > 0.05), and the number of hypotensive episodes or anaesthetic changes and depth of anaesthesia. Nevertheless, heart rate was lower during the 8 min following tracheal intubation in the sevoflurane group. In both groups, the duration of hypotension was easily controlled either by ephedrine or by adjusting the anaesthetic concentrations. Overall, haemodynamic tolerance appears to be similar in the two techniques. Because hypotension occurred after alfentanil in most patients, this study questioned which is the best opioid dose, if any, to associate with propofol or sevoflurane for the induction in hypertensive patients.

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.