Desflurane increases heart rate independent of sympathetic activity in dogs

Esmolol pretreatment attenuates heart rate increase and parasympathetic inhibition during rapid increases in desflurane concentration: A preliminary randomized study

BACKGROUND

Rapid increases in desflurane concentration can transiently increase the heart rate (HR). Esmolol possesses a high β1-adrenoceptor selectivity and a short duration of action. This preliminary study aimed at investigating the effects of esmolol on the HR and autonomic modulation during a desflurane-induced HR increase.

METHODS

American Society of Anesthesiologists physical status I female subjects, aged 20 to 50 years, who were undergoing minor breast surgery were randomly assigned to 2 groups. Rapid increases in desflurane concentration were commenced after induction of anesthesia. Each subject received either i.v. saline (control group) or esmolol 0.5 mg/kg (esmolol group) before desflurane inhalation. Using time-frequency spectral analysis of HR variability, the HR indices were studied at baseline, postinduction, posttreatment, as well as at minimal alveolar concentrations of desflurane reaching 1.0, 1.3, and 1.5. The low frequency (LF) power is influenced by both the sympathetic and parasympathetic activity, whereas the high frequency (HF) power reflects the parasympathetic activity. The LF/HF ratio is thought to reflect either sympathovagal balance or sympathetic modulation.

RESULTS

Electrocardiograms for data analysis were obtained from 8 subjects in each group. Rapid increases in desflurane concentration after induction caused a HR increase. Both the corresponding LF and HF powers were low and the LF/HF ratio remained unchanged. This indicates that the desflurane-induced HR increase may be attributed to parasympathetic inhibition and may be independent of sympathetic activation. Esmolol pretreatment effectively attenuated desflurane-induced HR increase. Moreover, subjects receiving esmolol pretreatment had increased LF and HF powers, but did not have changes in their LF/HF ratios, as compared to those without esmolol.

CONCLUSION

Esmolol pretreatment attenuates HR increase and parasympathetic inhibition during rapid increases in desflurane concentration.

Effect of different anesthetic agents on oculocardiac reflex in pediatric strabismus surgery

PURPOSE

The oculocardiac reflex (OCR) occurs frequently during pediatric strabismus surgery. The aim of this study was to assess the effects of various anesthetic regimens on the incidence of OCR during the surgery.

METHODS

Two hundred and eighty children, 1 to 9 years old, undergoing elective strabismus surgery, were randomly assigned to eight groups; ketamine-sevoflurane (KS), ketamine-desflurane (KD), ketamine-propofol (KP), ketamine-remifentanil (KR), midazolam-sevoflurane (MS), midazolam-desflurane (MD), midazolam-propofol (MP), and midazolam-remifentanil (MR). No premedication was given. Anesthesia was induced using ketamine 1 mg kg(-1) or midazolam 0.15 mg kg(-1) with 66% N(2)O in O(2). Laryngeal mask airways (LMAs) were placed with rocuronium 0.5 mg kg(-1). Anesthesia was maintained with sevoflurane 2-3 vol. %, desflurane 5-6 vol. %, propofol 7-8 mg kg(-1) h(-1), or remifentanil 0.75 microg kg(-1) over 1 min, followed by a continuous infusion of remifentanil 0.5 microg kg(-1) min(-1) with 66% N(2)O in O(2). Heart rate (HR) was recorded during extraocular muscle (EOM) manipulation. OCR was defined as a reduction in HR of more than 20% induced by the traction of an EOM.

RESULTS

In patients given ketamine, OCR occurred more frequently in the KP (65.7%) and KR (62.9%) groups than in the KD (29.4%) and KS (37.1%) groups (P < 0.05). In patients given midazolam, OCR occurred more frequently in the MP (54.3%) and MR (60.6%) groups than in the MD (36.4%) and MS (31.4%) groups (P < 0.05).

CONCLUSION

Propofol or remifentanil anesthesia was associated with a higher incidence of OCR during pediatric strabismus surgery than sevoflurane and desflurane anesthesia, when either ketamine or midazolam was used as an induction agent.

Anesthetic management for cesarean delivery in a patient with severe aortic stenosis and severe obesity

Valvular heart disease has significant effect on the maternal and fetal outcome of pregnancy. The severity and extent of aortic stenosis is of great value for risk assessment and for the design of a therapeutic plan. The therapeutic plan for such patients is further complicated by severe obesity. We report a case describing the anesthetic management of an extremely obese patient for cesarean delivery with severe aortic valve stenosis and regurgitation. The case was made complex due to the patient's deteriorating condition and not offering consent to emergency surgical procedures. The 34-year-old parturient underwent cesarean delivery at 32 weeks gestation under general anesthesia in the presence of a cardiothoracic surgical team. This case report demonstrates the importance of multidisciplinary preoperative assessment in such patients and careful anesthetic planning to avoid the deterioration of perioperative cardiac performance in parturients with complex valvular disease.