High concentrations of isoflurane do not block the sympathetic nervous system activation from desflurane

Examination under anesthesia: Preferred Practice

Pediatric ocular examinations are often a challenge in the outpatient setting due to limited cooperation of the child. Hence an evaluation under anesthesia (EUA) or sedation is important for a holistic ophthalmic examination. It can be combined with short procedures, such as suture removal and corneal scrappings, both for diagnosis and for the management of several ophthalmic disorders. It can also be performed before planning a surgical intervention to record the baseline characters and formulate or refine a surgical plan. Every EUA must be used as a chance to perform a complete ophthalmic examination rather than perform a single task such as recording the intraocular pressure. This article aims to provide a protocol that can be followed for a complete EUA.

Effect of general anaesthesia on intraocular pressure in paediatric patients: a systematic review

OBJECTIVES

Assessment of the impact of general anaesthetic agents on intraocular pressure (IOP) in children via systematic review.

METHODS

Pubmed, Embase, and CENTRAL databases were systematically searched to identify randomised controlled trials, prospective, and interventional studies. The search included all studies through October 5, 2018 with no date or language restrictions. A linear mixed-effects regression analysis was performed to study the change in IOP after general anaesthesia (GA).

RESULTS

The strategy identified 518 studies that met search criteria. Six studies (531 eyes) were included for quantitative synthesis. Seven categories of mixed and non-mixed induction and maintenance agents were compared. When assessing all agents utilising a model of mean IOP as a function of time, IOP decreased after induction phase at a rate of -0.59 ± 0.19 mmHg/min (P value = 0.006).

CONCLUSIONS

This systematic review showed that most anaesthetic agents significantly decrease IOP over time after the induction phase of general anaesthesia in children. An understanding of the effects of GA on IOP is critical for those performing paediatric ophthalmic examinations under anaesthesia.

Effect of anesthesia on intraocular pressure measurement in children

Measurement of the intraocular pressure (IOP) is central to the diagnosis and management of pediatric glaucoma. An examination under anesthesia is often necessary in pediatric patients. Different agents used for sedation or general anesthesia have varied effects on IOP. Hemodynamic factors, methods of airway management, tonometry technique, and body positioning can all affect IOP measurements. The most accurate technique is one that reflects the awake IOP. We review factors affecting IOP measurements in the pediatric population and provide recommendations on the most accurate means to measure IOP under anesthesia based on the present literature.

Recovery of postoperative cognitive function in elderly patients after a long duration of desflurane anesthesia: a pilot study

Postoperative cognitive dysfunction (POCD) increases morbidity and mortality. The mechanisms underlying POCD remain elusive; however, systemic responses induced by anesthesia and surgery might trigger neuroinflammation and POCD. Desflurane is a preferable volatile anesthetic agent for elderly patients because it facilitates shorter recovery from general anesthesia. The aim of this study was to determine whether quality of emergence and cognitive function in elderly patients undergoing a long duration desflurane anesthesia are better than those in the case of sevoflurane anesthesia. Forty-two patients who were older than 65 years of age and scheduled for surgery of more than 4 h in duration were enrolled in this study. Patients were randomly assigned to a desflurane anesthesia group (D group) and sevoflurane anesthesia group (S group). General anesthesia was maintained with 3.5 % desflurane (D group) and 1.0 % sevoflurane (S group). The Mini-Mental State Examination (MMSE) was used for assessing cognitive function 24 h before and after surgery. Postoperative MMSE score in the D group was significantly improved compared to that in the preoperative period. In conclusion, elderly patients undergoing desflurane anesthesia have significantly better quality of emergence and may have better cognitive function than those in elderly patients undergoing sevoflurane anesthesia.

Vasovagal oscillations and vasovagal responses produced by the vestibulo-sympathetic reflex in the rat

Sinusoidal galvanic vestibular stimulation (sGVS) induces oscillations in blood pressure (BP) and heart rate (HR), i.e., vasovagal oscillations, as well as transient decreases in BP and HR, i.e., vasovagal responses, in isoflurane-anesthetized rats. We determined the characteristics of the vasovagal oscillations, assessed their role in the generation of vasovagal responses, and determined whether they could be induced by monaural as well as by binaural sGVS and by oscillation in pitch. Wavelet analyses were used to determine the power distributions of the waveforms. Monaural and binaural sGVS and pitch generated vasovagal oscillations at the frequency and at twice the frequency of stimulation. Vasovagal oscillations and vasovagal responses were maximally induced at low stimulus frequencies (0.025-0.05 Hz). The oscillations were attenuated and the responses were rarely induced at higher stimulus frequencies. Vasovagal oscillations could occur without induction of vasovagal responses, but vasovagal responses were always associated with a vasovagal oscillation. We posit that the vasovagal oscillations originate in a low frequency band that, when appropriately activated by strong sympathetic stimulation, can generate vasovagal oscillations as a precursor for vasovagal responses and syncope. We further suggest that the activity responsible for the vasovagal oscillations arises in low frequency, otolith neurons with orientation vectors close to the vertical axis of the head. These neurons are likely to provide critical input to the vestibulo-sympathetic reflex to increase BP and HR upon changes in head position relative to gravity, and to contribute to the production of vasovagal oscillations and vasovagal responses and syncope when the baroreflex is inactivated.

Hemodynamic effects of butorphanol in desflurane-anesthetized dogs

OBJECTIVE

To evaluate the effects of butorphanol on cardiopulmonary parameters in dogs anesthetized with desflurane and breathing spontaneously.

STUDY DESIGN

Prospective, randomized experimental trial.

ANIMALS

Twenty dogs weighing 12 ± 3 kg.

METHODS

Animals were distributed into two groups: a control group (CG) and butorphanol group (BG). Propofol was used for induction and anesthesia was maintained with desflurane (10%). Forty minutes after induction, the dogs in the CG received sodium chloride 0.9% (0.05 mL kg(-1) IM), and dogs in the BG received butorphanol (0.4 mg kg(-1) IM). The first measurements of body temperature (BT), heart rate (HR), arterial pressures (AP), cardiac output (CO), cardiac index (CI), central venous pressure (CVP), stroke volume index (SVI), pulmonary arterial occlusion pressure (PAOP), mean pulmonary arterial pressure (mPAP), left ventricular stroke work (LVSW), systemic (SVR) and pulmonary (PVR) vascular resistances, respiratory rate (f(R) ), and arterial oxygen (PaO(2) ) and carbon dioxide (PaCO(2) ) partial pressures were taken immediately before the administration of butorphanol or sodium chloride solution (T0) and then at 15-minute intervals (T15-T75).

RESULTS

In the BG, HR, AP, mPAP and SVR decreased significantly from T15 to T75 compared to baseline. f(R) was lower at T30 than at T0 in the BG. AP and f(R) were significantly lower than in the CG from T15 to T75. PVR was lower in the BG than in the CG at T30, while PaCO(2) was higher compared with T0 from T30 to T75 in the BG and significantly higher than in the CG at T30 to T75.

CONCLUSIONS AND CLINICAL RELEVANCE

At the studied dose, butorphanol caused hypotension and decreased ventilation during desflurane anesthesia in dogs. The hypotension (from 86 ± 10 to 64 ± 10 mmHg) is clinically relevant, despite the maintenance of cardiac index.

Sinusoidal neck suction for evaluation of baroreflex sensitivity during desflurane and sevoflurane anesthesia

Sevoflurane and desflurane modulate autonomic nervous activity by different mechanisms. We tested the hypothesis that these anesthetics also exhibit different effects on short-term baroreflex regulation of arterial blood pressure. Forty ASA physical status I patients, aged 20 to 42 yr, were randomly assigned to receive either 1.0 minimum alveolar anesthetic concentration of sevoflurane or desflurane for the maintenance of anesthesia. Patients were studied during awake conditions and 20 min after the anesthesia induction using sinusoidal neck suction at 0.2 Hz (baroreflex response mediated mainly by vagal activity) and 0.1 Hz (baroreflex response mediated by vagal and sympathetic activity), whereas respiratory frequency was fixed at 0.25 Hz. RR interval and arterial blood pressure responses were evaluated by power spectral analysis and complex transfer function analysis. Sevoflurane and desflurane did not disturb the linear relationship between baroreceptor stimulation and effector response, expressed as squared coherence of signals, i.e., the equivalent of the correlation coefficient of power spectra. Sevoflurane and desflurane depressed the response of the heart rate to neck suction in a similar way without affecting the time delay between baroreceptor stimulation and vagal-mediated cardiac response. The gain of the transfer function between neck suction and oscillation in arterial blood pressure at 0.1 Hz decreased with sevoflurane and desflurane to comparable values. Both anesthetics increased the delay of systolic blood pressure response to baroreceptor stimulation from approximately 3.5 to 4.3 s. Baroreflex-mediated short-term control of arterial blood pressure is similar between desflurane and sevoflurane during steady-state conditions.

IMPLICATIONS

Despite exhibiting different effects on autonomic activity, sevoflurane and desflurane depress the baroreflex-mediated short-term control of heart rate and blood pressure in a similar manner.

Inhalational anaesthesia

Sevoflurane and desflurane have important advantages over isoflurane and halothane. Disadvantages, which the clinician should keep in mind, include the degradation of both agents by soda lime under certain circumstances during closed circuit anaesthesia. As a result compound A and carbon monoxide (CO) may be generated in soda lime canisters and may be inhaled by patients. The extent to which this constitutes a significant problem during routine anaesthesia in humans is not clear. Recent developments in absorbent technology have the potential to reduce any hazard to negligible proportions. Other undesirable properties of the newer inhalation agents include agitation with sevoflurane in children and cardiovascular and airway effects with desflurane.