Exogenous adenosine potentiates hypnosis induced by intravenous anaesthetics

Activation of astrocytes in the basal forebrain in mice facilitates isoflurane-induced loss of consciousness and prolongs recovery

OBJECTIVES

General anesthesia results in a state of unconsciousness that is similar to sleep. In recent years, increasing evidence has reported that astrocytes play a crucial role in regulating sleep. However, whether astrocytes are involved in general anesthesia is unknown.

METHODS

In the present study, the designer receptors exclusively activated by designer drugs (DREADDs) approach was utilized to specifically activate astrocytes in the basal forebrain (BF) and observed its effect on isoflurane anesthesia. One the other side, L-α-aminoadipic acid was used to selectively inhibit astrocytes in the BF and investigated its influence on isoflurane-induced hypnotic effect. During the anesthesia experiment, cortical electroencephalography (EEG) signals were recorded as well.

RESULTS

The chemogenetic activation group had a significantly shorter isoflurane induction time, longer recovery time, and higher delta power of EEG during anesthesia maintenance and recovery periods than the control group. Inhibition of astrocytes in the BF delayed isoflurane-induced loss of consciousness, promoted recovery, decreased delta power and increased beta and gamma power during maintenance and recovery periods.

CONCLUSIONS

The present study suggests that astrocytes in the BF region are involved in isoflurane anesthesia and may be a potential target for regulating the consciousness state of anesthesia.

The effect of preoperative aminophylline on the recovery profile after major pelvic-abdominal surgeries: a randomized controlled double-blinded study

Background

This study compared the effects of premedication with different doses of aminophylline on the recovery profile after general anaesthesia.

Methods

Forty-five patients scheduled for pelvic-abdominal surgeries were divided into 3 groups: Group C: the patients received 100 ml of IV normal saline, Group A1: the patients received 2 mg/kg IV aminophylline, and Group A2: the patients received 4 mg/kg IV aminophylline 30 min before induction of general anaesthesia. The following data were recorded: demographic data, ASA physical status, duration of anaesthesia and surgery, heart rate, mean arterial blood pressure, propofol dose, fentanyl dose, times to reach BIS (48 ± 2) after induction of anaesthesia and to reach a value of 80 after discontinuation of sevoflurane anaesthesia, time to recovery of consciousness and to tracheal extubation and to discharge from the post-anaesthesia care unit, and side effects of aminophylline.

Results

The time to reach a BIS of 48 ± 2 was significantly lower for the control group than group A2 (70.67 ± 22.50 and 106.67 ± 34.77 s for groups C and A2, respectively, p -value =0.01). The time to reach a BIS of 80 was significantly longer for the control group than group A1 andA2 (5.6 ± 1.40,3.5 ± 1.93and 2.53 ± 1.72 min for groups C,A1 and A2, respectively, p -value < 0.01). The time to ROC was significantly longer for the control group than groups A1 and A2 (8.93 ± 0.92, 5.6 ± 2.47 and 4.53 ± 3.33 min for groups C, A1 and A2, respectively; p -value < 0.01). The extubation time was significantly longer for the control group than groups A1 and A2 (12.4 ± 1.08, 7.87 ± 3.27 and 6.6 ± 2.47 min for groups C, A1 and A2, respectively; p -value < 0.01).

Conclusion

Premedication with aminophylline enhanced the recovery profile after pelvic-abdominal surgeries under general anaesthesia without cardiovascular complications.

Clinical trial registration

Name of the registry: Register@ClinicalTrials.gov

Trial registration number: ClinicalTrials.gov Identifier: NCT04151381.

Date of registration, November 5, 2019, ‘Retrospectively registered’.

Neuronal mechanisms of adenosine A2A receptors in the loss of consciousness induced by propofol general anesthesia with functional magnetic resonance imaging

Propofol is the most common intravenous anesthetic agent for induction and maintenance of anesthesia, and has been used clinically for more than 30 years. However, the mechanism by which propofol induces loss of consciousness (LOC) remains largely unknown. The adenosine A_2A receptor (A_2A R) has been extensively proven to have an effect on physiological sleep. It is, therefore, important to investigate the role of A_2A R in the induction of LOC using propofol. In the present study, the administration of the highly selective A_2A R agonist (CGS21680) and antagonist (SCH58261) was utilized to investigate the function of A_2A R under general anesthesia induced by propofol by means of animal behavior studies, resting-state magnetic resonance imaging and c-Fos immunofluorescence staining approaches. Our results show that CGS21680 significantly prolonged the duration of LOC induced by propofol, increased the c-Fos expression in nucleus accumbens (NAc) and suppressed the functional connectivity of NAc-dorsal raphe nucleus (DR) and NAc-cingulate cortex (CG). However, SCH58261 significantly shortened the duration of LOC induced by propofol, decreased the c-Fos expression in NAc, increased the c-Fos expression in DR, and elevated the functional connectivity of NAc-DR and NAc-CG. Collectively, our findings demonstrate the important roles played by A_2A R in the LOC induced by propofol and suggest that the neural circuit between NAc-DR maybe controlled by A_2A R in the mechanism of anesthesia induced by propofol.

The effects of Aminophylline on clinical recovery and bispectral index in patients anesthetized with total intravenous anaesthesia

OBJECTIVE

Aminophylline, which is clinically used as a bronchodilator, antagonizes the action of adenosine, so it can be used to shorten the recovery time after general anesthesia. Therefore, we wanted to test the hypothesis that the administration of aminophylline leads to an increase in bispectral index (BIS) and clinical recovery in patients anesthetized with total intravenous anesthesia (TIVA). Methods : Ninety two patients who were scheduled for elective inguinal herniorrhaphy were enrolled in this study. All patients were premedicated with midazolam and morphine. Anesthesia was induced with propofol 2.5 mg /kg and remifentanil 2.5 µg/kg without muscle relaxant. For maintenance of anesthesia we used propofol 100µg/kg/min, remifentanil 0.2µg/kg/min and 100% oxygen with stable BIS readings in the range 40-60. After skin closure, aminophylline 4mg/ kg was given to Group A and an equivalent volume of normal saline to Group P. BIS values, heart rate, blood pressure, oxygen saturation and End tidal CO2(ETco2) were determined. Time to eye opening, extubation time and response to command were measured. Results : There were no significant differences in SpO2, ETco2 and anesthesia time. Heart rate and systolic blood pressure were found to be statistically higher (p<0.001) in Group A. Time to eye opening, hand grip and extubation were significantly shorter (p<0.001) in Group A. Bispectral index scores were significantly higher in group A.

CONCLUSIONS

Injection of aminophylline at emergence time led to significant increase in BIS and shortening recovery time from anesthesia.

IV ATP potentiates midazolam sedation as assessed by bispectral index

In this study, by measuring bispectral index (BIS), we tested the hypothesis that intravenous adenosine 5'-triphosphate (ATP) infusion would deepen the level of midazolam-induced sedation. Ten healthy volunteers underwent 2 experiments with at least 2 weeks' interval: immediately after intravenous bolus administration of midazolam (0.04 mg/kg), they received continuous infusion of either ATP infusion (100 μg/kg/min) or placebo (saline) for 40 minutes in a double-blind, randomized, crossover manner. Changes in BIS values and responsiveness to verbal command as well as cardiorespiratory variables were observed throughout the study periods. Administration of midazolam alone reduced BIS value from control: 97 ± 1 to 68 ± 18 at 25 minutes, which was accompanied by significant cardiopulmonary depressant effects, while maintaining responsiveness to verbal command (consciousness) throughout the study period. Coadministration of ATP with midazolam further reduced BIS value to 51 ± 13, associated with complete loss of consciousness without adverse effect on the cardiorespiratory systems. We conclude that the addition of ATP infusion to midazolam significantly enhances midazolam sedation without disturbing cardiorespiratory functions.

[Is deep anesthesia dangerous?]

Regarding the question of an adequate depth of anesthesia, over the past decade anesthesiologists have focused on the prevention of intraoperative consciousness in combination with explicit memory. Recent studies approached the topic from a different way postulating that deep anesthesia, quantified as time with a bispectral index (BIS)< 45, is associated with increased postoperative mortality and four out of the five published studies revealed such a correlation. However, the finding is limited by a suboptimal study design, e.g. none of the studies presented randomized data. Furthermore, it is ambiguous whether the correlation is causal as the administration of deep anesthesia determines higher postoperative mortality or the study results reveal an epiphenomenon. An epiphenomenon implies e.g. that patients with cancer respond to general anesthesia with deeper cortical depression. In summary, as long as there is a lack of adequately performed randomized trials, there is no reason why anesthesiologists should change the current practice.

Rapid eye movement sleep debt accrues in mice exposed to volatile anesthetics

BACKGROUND

General anesthesia has been likened to a state in which anesthetized subjects are locked out of access to both rapid eye movement (REM) sleep and wakefulness. Were this true for all anesthetics, a significant REM rebound after anesthetic exposure might be expected. However, for the intravenous anesthetic propofol, studies demonstrate that no sleep debt accrues. Moreover, preexisting sleep debts dissipate during propofol anesthesia. To determine whether these effects are specific to propofol or are typical of volatile anesthetics, the authors tested the hypothesis that REM sleep debt would accrue in rodents anesthetized with volatile anesthetics.

METHODS

Electroencephalographic and electromyographic electrodes were implanted in 10 mice. After 9-11 days of recovery and habituation to a 12 h:12 h light-dark cycle, baseline states of wakefulness, nonrapid eye movement sleep, and REM sleep were recorded in mice exposed to 6 h of an oxygen control and on separate days to 6 h of isoflurane, sevoflurane, or halothane in oxygen. All exposures were conducted at the onset of light.

RESULTS

Mice in all three anesthetized groups exhibited a significant doubling of REM sleep during the first 6 h of the dark phase of the circadian schedule, whereas only mice exposed to halothane displayed a significant increase in nonrapid eye movement sleep that peaked at 152% of baseline.

CONCLUSION

REM sleep rebound after exposure to volatile anesthetics suggests that these volatile anesthetics do not fully substitute for natural sleep. This result contrasts with the published actions of propofol for which no REM sleep rebound occurred.

The effect of aminophylline on loss of consciousness, bispectral index, propofol requirement, and minimum alveolar concentration of desflurane in volunteers

BACKGROUND

Adenosine is a soporific neuromodulator; aminophylline, which is clinically used as a bronchodilator, antagonizes the action of adenosine in the central nervous system. Thus, we tested the hypothesis that aminophylline delays loss of consciousness (LOC) and speeds recovery of consciousness (ROC) with propofol anesthesia, and that aminophylline increases the minimum alveolar concentration (MAC) of desflurane.

METHODS

In this double-blind crossover study, volunteers were randomized to either aminophylline or saline on different days. Aminophylline 6 mg/kg was given IV, followed by 1.5 mg x kg(-1) x h(-1) throughout the study day. After 1 h of aminophylline or saline administration, propofol 200 mg was given at a rate of 20 mg/min. The bispectral index was continuously monitored, as were times to LOC and ROC. After recovery from propofol, general anesthesia was induced with sevoflurane and subsequently maintained with desflurane. The Dixon "up-and-down" method was used to determine MAC in each volunteer after repeated tetanic electrical stimulation.

RESULTS

Eight volunteers completed both study days. Time to LOC was prolonged by aminophylline compared with saline (mean +/- SD) (7.7 +/- 2.03 min vs 5.1 +/- 0.75 s, respectively, P = 0.011). The total propofol dose at LOC was larger with aminophylline (2.2 +/- 0.9 vs 1.4 +/- 0.4 mg/kg, P = 0.01), and the time to ROC was shorter (6.18 +/- 3.96 vs 12.2 +/- 4.73 min, P = 0.035). The minimum bispectral index was greater with aminophylline (51 +/- 15 vs 38 +/- 9, P = 0.034). There was no difference in MAC.

CONCLUSION

Aminophylline decreases the sedative effects of propofol but does not affect MAC of desflurane as determined by tetanic electrical stimulation.

Increased volatile anesthetic requirement in short-sleeping Drosophila mutants

BACKGROUND

Anesthesia and sleep share physiologic and behavioral similarities. The anesthetic requirement of the recently identified Drosophila mutant minisleeper and other Drosophila mutants was investigated.

METHODS

Sleep and wakefulness were determined by measuring activity of individual wild-type and mutant flies. Based on the response of the flies at different concentrations of the volatile anesthetics isoflurane and sevoflurane, concentration-response curves were generated and EC50 values were calculated.

RESULTS

The average amount of daily sleep in wild-type Drosophila (n = 64) was 965 +/- 15 min, and 1,022 +/- 29 in Na[har](P > 0.05; n = 32) (mean +/- SEM, all P compared to wild-type and other shaker alleles). Sh flies slept 584 +/- 13 min (n = 64, P < 0.01), Sh flies 412 +/- 22 min (n = 32, P < 0.01), and Sh flies 782 +/- 25 min (n = 32, P < 0.01). The EC50 values for isoflurane were 0.706 (95% CI 0.649 to 0.764, n = 661) and for sevoflurane 1.298 (1.180 to 1.416, n = 522) in wild-type Drosophila; 1.599 (1.527 to 1.671, n = 308) and 2.329 (2.177 to 2.482, n = 282) in Sh, 1.306 (1.212 to 1.400, n = 393) and 2.013 (1.868 to 2.158, n = 550) in Sh, 0.957 (0.860 to 1.054, n = 297) and 1.619 (1.508 to 1.731, n = 386) in Sh, and 0.6154 (0.581 to 0.649, n = 360; P < 0.05) and 0.9339 (0.823 to 1.041, n = 274) in Na[har], respectively (all P < 0.01).

CONCLUSIONS

A single-gene mutation in Drosophila that causes an extreme reduction in daily sleep is responsible for a significant increase in the requirement of volatile anesthetics. This suggests that a single gene mutation affects both sleep behavior and anesthesia and sedation.

An essential role for orexins in emergence from general anesthesia

The neural mechanisms through which the state of anesthesia arises and dissipates remain unknown. One common belief is that emergence from anesthesia is the inverse process of induction, brought about by elimination of anesthetic drugs from their CNS site(s) of action. Anesthetic-induced unconsciousness may result from specific interactions of anesthetics with the neural circuits regulating sleep and wakefulness. Orexinergic agonists and antagonists have the potential to alter the stability of the anesthetized state. In this report, we refine the role of the endogenous orexin system in impacting emergence from, but not entry into the anesthetized state, and in doing so, we distinguish mechanisms of induction from those of emergence. We demonstrate that isoflurane and sevoflurane, two commonly used general anesthetics, inhibit c-Fos expression in orexinergic but not adjacent melanin-concentrating hormone (MCH) neurons; suggesting that wake-active orexinergic neurons are inhibited by these anesthetics. Genetic ablation of orexinergic neurons, which causes acquired murine narcolepsy, delays emergence from anesthesia, without changing anesthetic induction. Pharmacologic studies with a selective orexin-1 receptor antagonist confirm a specific orexin effect on anesthetic emergence without an associated change in induction. We conclude that there are important differences in the neural substrates mediating induction and emergence. These findings support the concept that emergence depends, in part, on recruitment and stabilization of wake-active regions of brain.

Anesthesia and sleep

Although both general anesthesia and naturally occurring sleep depress consciousness, distinct physiological differences exist between the two states. Recent lines of evidence have suggested that sleep and anesthesia may be more similar than previously realized. Localization studies of brain nuclei involved in sleep have indicated that such nuclei are important in anesthetic action. Additional observations that regional brain activity during anesthesia resembles that in the sleeping brain have raised the possibility that anesthesia may exert its effects by activating neuronal networks normally involved in sleep. In animals, behavioral interactions between sleep and anesthesia appear to support these mechanistic similarities. Rat studies demonstrate that sleep debt accrued during prolonged wakefulness dissipate during anesthesia. Moreover, anesthetic potency is subject both to circadian effects and to the degree of prior sleep deprivation. Such interactions may partly explain anesthetic variability among patients. Finally, sleep and anesthesia interact physiologically. Endogenous neuromodulators known to regulate sleep also alter anesthetic action, and anesthetics cause sleep with direct administration into brain nuclei known to regulate sleep. Together, these observations provide new research directions for understanding sleep regulation and generation, and suggest the possibility of new clinical therapies both for patients with sleep disturbances and for sleep deprived patients receiving anesthesia.

Administration of adenosine receptor agonists or antagonists after controlled cortical impact in mice: effects on function and histopathology

Adenosine is an endogenous neuroprotectant via anti-excitotoxic effects at A(1) receptors, and blood flow promoting and anti-inflammatory effects at A(2a) receptors. Previous studies showed improved motor function after fluid percussion injury (FPI) in rats treated with the broad-spectrum adenosine receptor agonist 2-chloroadenosine (2-CA). We studied the effects of 2-CA, a specific A(1) agonist (2-chloro-N(6)-cyclopentyladenosine, CCPA), and a specific A(1) antagonist (8-cyclopentyl-1,3-dipropylxanthine, DPCPX) on motor task and Morris water maze (MWM) performance, and histopathology (contusion volume, hippocampal cell counts) after controlled cortical impact (CCI) in mice. Each agent (12 nmol), or respective vehicle (saline or DMSO) was injected into dorsal hippocampus beneath the contusion immediately after CCI or craniotomy (sham). 2-CA treatment attenuated wire grip deficits after CCI (P<0.05 versus other treatments). DPCPX treatment exacerbated deficits on beam balance (P<0.05 versus sham). No treatment effect was seen on MWM performance, although there was a deleterious effect of the DMSO vehicle used for DPCPX. Contusion volume tended to be attenuated by 2-CA (P=0.08 versus saline) and increased after either DMSO or DPCPX (P<0.05 versus all groups). CA1 and CA3 counts were decreased in all groups versus sham. However, treatment with the selective A(1) agonist CCPA attenuated the CA3 cell loss (P<0.05 versus other treatment). We suggest that the beneficial effect of the broad spectrum adenosine receptor agonist 2-CA on motor function after CCI is not mediated solely by effects at the A(1) receptor.

The sodium pentothal hypnosis interview with follow-up treatment for complex regional pain syndrome

A patient who was unresponsive to multiple conservative medical treatments for complex regional pain syndrome was assessed using a novel approach--the sodium pentothal hypnosis interview. The interview suggested that his pain was centrally generated. The patient's pain symptoms resolved with hypnotherapeutic treatment. Indications for this procedure and implications for assessment and treatment are discussed. This case raises more questions than it answers, and leaves the reader to struggle with current difficulties in diagnostic decision-making.