Caffeine accelerates recovery from general anesthesia via multiple pathways

Time to Wake Up! The Ongoing Search for General Anesthetic Reversal Agents

How general anesthetics work remains a topic of ongoing study. A parallel field of research has sought to identify methods to reverse general anesthesia. Reversal agents could shorten patients' recovery time and potentially reduce the risk of postoperative complications. An incomplete understanding of the mechanisms of general anesthesia has hampered the pursuit for reversal agents. Nevertheless, the search for reversal agents has furthered understanding of the mechanisms underlying general anesthesia. The study of potential reversal agents has highlighted the importance of rigorous criteria to assess recovery from general anesthesia in animal models, and has helped identify key arousal systems (e.g., cholinergic, dopaminergic, and orexinergic systems) relevant to emergence from general anesthesia. Furthermore, the effects of reversal agents have been found to be inconsistent across different general anesthetics, revealing differences in mechanisms among these drugs. The presynapse and glia probably also contribute to general anesthesia recovery alongside postsynaptic receptors. The next stage in the search for reversal agents will have to consider alternate mechanisms encompassing the tripartite synapse.

Caffeine administration to treat oversedation after general anesthesia: A retrospective analysis

STUDY OBJECTIVE

Our institution has adopted an informal practice of administering postoperative caffeine to expedite anesthesia recovery for patients with excessive sedation. This study aimed to determine whether caffeine administration was associated with improved sedation recovery and reduced risk of respiratory complications.

DESIGN

Single-center, retrospective, observational study.

SETTING

Quaternary medical center.

PATIENTS

We included adult patients who were admitted to a postanesthesia recovery care unit (PACU) after general anesthesia and had evidence of postoperative sedation (Richmond Agitation Sedation Score [RASS] < 0). Patients were seen from May 5, 2018, through December 31, 2020.

INTERVENTIONS

Patients were categorized according to caffeine administration (0 vs 250 mg).

MEASUREMENTS

Sedation was measured with RASS. To account for potential confounding, binary and ordinal logistic regression with inverse probability of treatment weighting (IPTW) were used to compare RASS and episodes of severe respiratory complications within 48 h after PACU discharge.

MAIN RESULTS

We identified 47,222 adult surgical patients with evidence of sedation in the PACU, and of these, 1892 (4.0%) were intravenously administered caffeine. Patients who received caffeine had more sedation in the PACU. In the IPTW-adjusted analysis, caffeine administration was associated with improved sedation scores after PACU discharge (ordinal logistic regression odds ratio [OR], 1.13 [95% CI, 1.00-1.28]; P = .04 for the first RASS score after PACU discharge) but increased risk of respiratory complications (OR, 2.99 [95% CI, 1.44-6.24]; P = .003) and emergency response team activation (OR, 7.18 [95% CI, 2.85-18.10]; P < .001).

CONCLUSIONS

In this observational study, caffeine administration during anesthesia recovery was associated with improved sedation scores. However, it was also associated with an increased risk of respiratory complications, possibly reflecting selection bias (ie, administering caffeine to higher-risk patients). Patients with signs of excessive sedation during anesthesia recovery may benefit from enhanced postoperative respiratory monitoring.

Caffeine - Essentials for anaesthesiologists: A narrative review

Caffeine has a multitude of uses in anaesthesia, and numerous studies have evaluated its efficacy and usefulness in various aspects of anaesthesia and medical practice. Its various applications in anaesthesia include its role in awakening from anaesthesia, managing post-dural puncture headache, managing post-sedation paradoxical hyper-activity in children, post-operative bowel paralysis, and apnoea in paediatric populations, that is, apnoea in infancy, paediatric obstructive apnoea, and post-anaesthetic apnoea in pre-mature infants. Though the effects of caffeine on bronchial smooth muscle, neurological, and cardio-vascular systems are well known, the relatively little-known effects on the endocrine and gastro-intestinal (GI) system have been recently taking primacy for eliciting its therapeutic benefits. The literature shows encouraging evidence in favour of caffeine, but unambiguous evidence of caffeine benefits for patients is lacking and needs further investigation. In this narrative review of literature, we summarise the available literature to provide insights into the pharmacokinetics, pharmacodynamics, clinical application of caffeine in modern anaesthetic practice, and evidence available in this field to date. An awareness of the various physiological effects, adverse effects, reported applications, and their evidence will widen the horizon for anaesthesiologists to increase its rational use and advance research in this field. Well-designed randomised controlled trials regarding the various outcomes related to caffeine use in anaesthesia should be planned to generate sound evidence and formulate recommendations to guide clinicians.

Comparison of the effects of caffeine, aminophylline, and saline on the recovery from total intravenous anesthesia in laparoscopic surgeries: A randomized controlled trial

Background and Aims

The return of consciousness (ROC) after general anesthesia (GA) is by stopping the administration of anesthetic agents. At present, no drug is given to reverse the loss of consciousness produced by general anesthetic agents. This study is conducted to find whether caffeine and aminophylline hasten the ROC.

Material and Methods

This study was conducted on 75 American Society of Anesthesiologists (ASA) I and II female patients undergoing laparoscopic hysterectomy, aged between 18 and 60 years. The patients were divided into three equal groups (Group C: caffeine citrate, Group A: aminophylline, and Group S: saline) of 25 each by a computer-generated random number table. GA was induced with propofol, fentanyl, and maintained with propofol infusion. On completion of the surgery, the neuromuscular blocking agent was reversed and then the infusion of propofol was stopped. The study drug was administered intravenously when the BIS 60 was achieved. Time to achieve BIS 90, return of first gag reflex, eye-opening on verbal command, and extubation after study drug administration were noted. Hemodynamic parameters and SpO2 were also monitored.

Results

The time for BIS 60 to 90 was 10 (4.25) min in the caffeine group, 13 (4.25) min in the aminophylline group, and 26 (9.0) min in the saline group. The time to return of gag reflex and time to extubation were shorter in the caffeine and aminophylline group compared to the saline group. The time to eye-opening on verbal command was shorter in the aminophylline group compared to the saline group. Hemodynamic parameters after infusion of the study drug were comparable in all three groups.

Conclusion

Caffeine hastens the recovery from total intravenous anesthesia with propofol and fentanyl in laparoscopic hysterectomy as effectively as aminophylline.

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.

Ketone supplementation abolished isoflurane anesthesia-induced elevation in blood glucose level and increased recovery time from anesthesia in Wistar Albino Glaxo Rijswijk rats

BACKGROUND

It has been suggested that administration of exogenous ketone supplements (EKSs) not only increases blood ketone body levels but also decreases blood glucose level and modulates isoflurane-induced anesthesia in different rodents, such as Wistar Albino Glaxo Rijswijk (WAG/Rij) rats. Thus, we investigated whether administration of EKSs can modulate the isoflurane anesthesia-generated increase in blood glucose level and the time required to recover from isoflurane-induced anesthesia.

METHODS

To investigate the effect of EKSs on isoflurane anesthesia-induced changes in blood glucose and R-β-hydroxybutyrate (R-βHB) level as well as recovery time from anesthesia, we used KEMCT (mix of ketone ester/KE and medium chain triglyceride/MCT oil in a 1:1 ratio) in WAG/Rij rats. First, to accustom the animals to the method, water gavage was carried out for 5 days (adaptation period). After adaptation period, rats of first group (group 1) were gavaged by water (3 g/kg), whereas, in the case of second group (group 2), the diet of animals was supplemented by KEMCT (3 g/kg, gavage) once per day for 7 days. One hour after the last gavage, isoflurane (3%) anesthesia was induced for 20 min (group 1 and group 2) and the time required for recovery from anesthesia was measured by using righting reflex. Subsequently, blood levels of both R-βHB and glucose were also evaluated. Changes in blood glucose and R-βHB levels were compared to control, which control glucose and R-βHB levels were measured on the last day of the adaptation period (group 1 and group 2). Time required for recovery from isoflurane anesthesia, which was detected after 7^th KEMCT gavage (group 2), was compared to recovery time measured after 7^th water gavage (group 1).

RESULTS

The KEMCT maintained the normal glucose level under isoflurane anesthesia-evoked circumstances preventing the glucose level elevating effect of isoflurane. Thus, we demonstrated that administration of KEMCT not only increased blood level of R-βHB but also abolished the isoflurane anesthesia-generated increase in blood glucose level. Moreover, the time required for recovery from isoflurane-evoked anesthesia increased significantly in KEMCT treated animals.

CONCLUSIONS

Putative influence of elevated blood ketone body level on isoflurane-evoked effects, such as modulation of blood glucose level and recovery time from anesthesia, should be considered by anesthesiologists.

Caffeine Use in the Anesthetic Management of a Patient With Congenital Central Hypoventilation

Congenital central hypoventilation syndrome (CCHS) is a rare neurological disease affecting the brain’s response to carbon dioxide levels, resulting in dysregulation of respiration. CCHS is characterized by a diminished effort to breathe during sleep despite hypoxia and hypercapnia. Ventilation is adequate during wakeful periods but diminished during sleep. Alterations in ventilation pose a challenge to anesthesiologists in their attempts to wean these patients from ventilatory support. We describe a patient with CCHS and a complicated history of prolonged tracheal intubation, who was treated with intravenous (IV) caffeine and was able to resume adequate spontaneous ventilation and baseline mental status immediately post-procedure.

Historical and Modern Evidence for the Role of Reward Circuitry in Emergence

Increasing evidence supports a role for brain reward circuitry in modulating arousal along with emergence from anesthesia. Emergence remains an important frontier for investigation, since no drug exists in clinical practice to initiate rapid and smooth emergence. This review discusses clinical and preclinical evidence indicating a role for two brain regions classically considered integral components of the mesolimbic brain reward circuitry, the ventral tegmental area and the nucleus accumbens, in emergence from propofol and volatile anesthesia. Then there is a description of modern systems neuroscience approaches to neural circuit investigations that will help span the large gap between preclinical and clinical investigation with the shared aim of developing therapies to promote rapid emergence without agitation or delirium. This article proposes that neuroscientists include models of whole-brain network activity in future studies to inform the translational value of preclinical investigations and foster productive dialogues with clinician anesthesiologists.

Effect of Caffeine on the Acceleration of Emergence from General Anesthesia with Inhalation Anesthetics in Children Undergoing Inguinal Herniorrhaphy: A Randomized Clinical Trial

Background

Awakening following general anesthesia (GA) is one of the most important concerns of anesthesiologists in their daily work. Previous studies on adult humans found that caffeine could accelerate awakening after anesthesia. This study aimed to determine whether or not caffeine can accelerate awakening after anesthesia in children undergoing inguinal herniorrhaphy under GA.

Methods

In this randomized clinical trial, we enrolled 18 children undergoing inguinal herniorrhaphy under GA with inhaled anesthetics from June 2019 to September 2019 in the tertiary hospital affiliated with Shiraz University of Medical Sciences (Shiraz, Iran). These children were randomly allocated to two groups. In group A, the children received intravenous caffeine (10 mg/Kg) at the end of the surgery, and in group B, the children received intravenous normal saline at the end of the surgery. The primary outcome was laryngeal mask airway (LMA) removal time at the end of anesthesia. Intra-operative hemodynamic data and side effects such as nausea, vomiting, dysrhythmia, cyanosis, and seizures in the recovery room were recorded and compared between the two groups. We used the independent-samples t test, Fisher's exact test, and repeated measures ANOVA for analyzing the data. P values<0.05 were considered statistically significant.

Results

There were no significant differences in terms of demographic characteristics and hemodynamic data between the two groups. Furthermore, the time from the induction of anesthesia to laryngeal mask removal was 44.77±7.87 min in the placebo group and 44.55±10.68 min in the caffeine group. Therefore, there was no significant difference between the two groups (P=0.961).

Conclusion

In children undergoing inguinal herniorrhaphy under GA, 10 mg/Kg of caffeine could not accelerate awakening from GA. However, caffeine did not increase the blood pressure and heart rate in the children, and no significant side effects were observed.

Trial Registration Number

IRCT20190511043550N1.

The Neural Circuits Underlying General Anesthesia and Sleep

General anesthesia is characterized by loss of consciousness, amnesia, analgesia, and immobility. Important molecular targets of general anesthetics have been identified, but the neural circuits underlying the discrete end points of general anesthesia remain incompletely understood. General anesthesia and natural sleep share the common feature of reversible unconsciousness, and recent developments in neuroscience have enabled elegant studies that investigate the brain nuclei and neural circuits underlying this important end point. A common approach to measure cortical activity across the brain is electroencephalogram (EEG), which can reflect local neuronal activity as well as connectivity among brain regions. The EEG oscillations observed during general anesthesia depend greatly on the anesthetic agent as well as dosing, and only some resemble those observed during sleep. For example, the EEG oscillations during dexmedetomidine sedation are similar to those of stage 2 nonrapid eye movement (NREM) sleep, but high doses of propofol and ether anesthetics produce burst suppression, a pattern that is never observed during natural sleep. Sleep is primarily driven by withdrawal of subcortical excitation to the cortex, but anesthetics can directly act at both subcortical and cortical targets. While some anesthetics appear to activate specific sleep-active regions to induce unconsciousness, not all sleep-active regions play a significant role in anesthesia. Anesthetics also inhibit cortical neurons, and it is likely that each class of anesthetic drugs produces a distinct combination of subcortical and cortical effects that lead to unconsciousness. Conversely, arousal circuits that promote wakefulness are involved in anesthetic emergence and activating them can induce emergence and accelerate recovery of consciousness. Modern neuroscience techniques that enable the manipulation of specific neural circuits have led to new insights into the neural circuitry underlying general anesthesia and sleep. In the coming years, we will continue to better understand the mechanisms that generate these distinct states of reversible unconsciousness.

Caffeine supplementation in the hospital: Potential role for the treatment of caffeine withdrawal

Caffeine use in the population is widespread. Caffeine withdrawal in the hospital setting is an underappreciated syndrome with symptoms including drowsiness, difficulty concentrating, mood disturbances, low motivation, flu-like symptoms, and headache. Withdrawal may occur upon abstinence from chronic daily exposure at doses as low as 100 mg/day and following only 3-7 days of consumption at higher doses. There are limited data investigating how caffeine withdrawal contributes to hospital morbidity. Some studies suggest caffeine withdrawal may contribute to intensive care delirium and that caffeine may promote wakefulness post-anesthesia. Caffeine supplementation has also shown promise in patients at risk of caffeine withdrawal, such as those placed on nil per os (NPO) status, in preventing caffeine withdrawal headache. These data on caffeine supplementation are not entirely consistent, and routine caffeine administration has not been implemented into clinical practice for patients at risk of withdrawal. Notably, caffeine serves a therapeutic role in the hospital for other conditions. Our review demonstrates that caffeine is largely safe in the general population and may be an appropriate therapeutic option for future studies, if administered properly. There is a need for a randomized controlled trial investigating in-hospital caffeine supplementation and the population that this would best serve.

Respiratory depression in the post-anesthesia care unit: Mayo Clinic experience

The anesthesia recovery is a complex physiologic process as systems recover from the effects of surgery and anesthesia. Inadequate recovery of respiratory physiology can lead to severe hypoxemia-induced end-organ damage and even death. Emerging evidence suggests that signs of respiratory depression during early anesthesia recovery may portend increased risk for future severe adverse events. This article briefly reviews the Mayo Clinic research experience and advances in clinical practice. From the implementation of a step-down model of discharge criteria in the post-anesthesia care unit (PACU), consisting of PACU nurses monitoring patients in predetermined periods for signs of respiratory depression, and delaying PACU discharge for patients who exhibit signs of respiratory depression, and early intervention in high-risk patients. Subsequent studies found that even a single episode of respiratory depression in the PACU was strongly associated with subsequent respiratory complications. Further, patient baseline characteristics found to be associated with respiratory depression included obstructive sleep apnea and low body weight, and surgical factors associated with increased risk included the use of preoperative sustained-release opioids, perioperative gabapentinoid use, higher intraoperative opioids, isoflurane as the volatile anesthetic, and longer surgical duration. Based in part of Mayo Clinic research, the FDA issued a warning in 2019 on gabapentinoids use and respiratory complications, increasing the recommended level of respiratory vigilance in patients using this medication. Understanding the complex nature of postoperative respiratory events requires a range of translational and clinical research and constant update of practice.

Use of therapeutic caffeine in acute care postoperative and critical care settings: a scoping review

BACKGROUND

Caffeine is the most utilised psychoactive drug worldwide. However, caffeine withdrawal and the therapeutic use of caffeine in intensive care and in the perioperative period have not been well summarised. Our objective was to conduct a scoping review of caffeine withdrawal and use in the intensive care unit (ICU) and postoperative patients.

METHODS

PubMed, Embase, CINAHL Complete, Scopus and Web of Science were systematically searched for studies investigating the effects of caffeine withdrawal or administration in ICU patients and in the perioperative period. Areas of recent systematic review such as pain or post-dural puncture headache were not included in this review. Studies were limited to adults.

RESULTS

Of 2268 articles screened, 26 were included and grouped into two themes of caffeine use in in the perioperative period and in the ICU. Caffeine withdrawal in the postoperative period increases the incidence of headache, which can be effectively treated prophylactically with perioperative caffeine. There were no studies investigating caffeine withdrawal or effect on sleep wake cycles, daytime somnolence, or delirium in the intensive care setting. Administration of caffeine results in faster emergence from sedation and anaesthesia, particularly in individuals who are at high risk of post-extubation complications. There has only been one study investigating caffeine administration to facilitate post-anaesthetic emergence in ICU. Caffeine administration appears to be safe in moderate doses in the perioperative period and in the intensive care setting.

CONCLUSIONS

Although caffeine is widely used, there is a paucity of studies investigating withdrawal or therapeutic effects in patients admitted to ICU and further novel studies are a priority.

Caffeine reverses the unconsciousness produced by light anesthesia in the continued presence of isoflurane in rats

Currently no drugs are employed clinically to reverse the unconsciousness induced by general anesthetics. Our previous studies showed that caffeine, when given near the end of an anesthesia session, accelerated emergence from isoflurane anesthesia, likely caused by caffeine’s ability to elevate intracellular cAMP levels and to block adenosine receptors. These earlier studies showed that caffeine did not rouse either rats or humans from deep anesthesia (≥ 1 minimum alveolar concentration, MAC). In this current crossover study, we examined whether caffeine reversed the unconsciousness produced by light anesthesia (< 1 MAC) in the continued presence of isoflurane. The primary endpoint of this study was to measure isoflurane levels at the time of recovery of righting reflex, which was a proxy for consciousness. Rats were deeply anesthetized with 2% isoflurane (~1.5 MAC) for 20 minutes. Subsequently, isoflurane was reduced to 1.2% for 10 minutes, then by 0.2% every 10 min; animals were monitored until the recovery of righting reflex occurred, in the continued presence of isoflurane. Respiration rate, heart rate and electroencephalogram (EEG) were monitored. Our results show that caffeine-treated rats recovered their righting reflex at a significantly higher inspired isoflurane concentration, corresponding to light anesthesia, than the same rats treated with saline (control). Respiration rate and heart rate increased initially after caffeine injection but were then unchanged for the rest of the anesthesia session. Deep anesthesia is correlated with burst suppression in EEG recordings. Our data showed that caffeine transiently reduced the burst suppression time produced by deep anesthesia, suggesting that caffeine altered neuronal circuit function but not to a point where it caused arousal. In contrast, under light anesthesia, caffeine shifted the EEG power to high frequency beta and gamma bands. These data suggest that caffeine may represent a clinically viable drug to reverse the unconsciousness produced by light anesthesia.

Neurotransmitter networks in mouse prefrontal cortex are reconfigured by isoflurane anesthesia

This study quantified eight small-molecule neurotransmitters collected simultaneously from prefrontal cortex of C57BL/6J mice (n = 23) during wakefulness and during isoflurane anesthesia (1.3%). Using isoflurane anesthesia as an independent variable enabled evaluation of the hypothesis that isoflurane anesthesia differentially alters concentrations of multiple neurotransmitters and their interactions. Machine learning was applied to reveal higher order interactions among neurotransmitters. Using a between-subjects design, microdialysis was performed during wakefulness and during anesthesia. Concentrations (nM) of acetylcholine, adenosine, dopamine, GABA, glutamate, histamine, norepinephrine, and serotonin in the dialysis samples are reported (means ± SD). Relative to wakefulness, acetylcholine concentration was lower during isoflurane anesthesia (1.254 ± 1.118 vs. 0.401 ± 0.134, P = 0.009), and concentrations of adenosine (29.456 ± 29.756 vs. 101.321 ± 38.603, P < 0.001), dopamine (0.0578 ± 0.0384 vs. 0.113 ± 0.084, P = 0.036), and norepinephrine (0.126 ± 0.080 vs. 0.219 ± 0.066, P = 0.010) were higher during anesthesia. Isoflurane reconfigured neurotransmitter interactions in prefrontal cortex, and the state of isoflurane anesthesia was reliably predicted by prefrontal cortex concentrations of adenosine, norepinephrine, and acetylcholine. A novel finding to emerge from machine learning analyses is that neurotransmitter concentration profiles in mouse prefrontal cortex undergo functional reconfiguration during isoflurane anesthesia. Adenosine, norepinephrine, and acetylcholine showed high feature importance, supporting the interpretation that interactions among these three transmitters may play a key role in modulating levels of cortical and behavioral arousal.

NEW & NOTEWORTHY This study discovered that interactions between neurotransmitters in mouse prefrontal cortex were altered during isoflurane anesthesia relative to wakefulness. Machine learning further demonstrated that, relative to wakefulness, higher order interactions among neurotransmitters were disrupted during isoflurane administration. These findings extend to the neurochemical domain the concept that anesthetic-induced loss of wakefulness results from a disruption of neural network connectivity.

Escape From Oblivion: Neural Mechanisms of Emergence From General Anesthesia

The question of how general anesthetics suppress consciousness has persisted since the mid-19th century, but it is only relatively recently that the field has turned its focus to a systematic understanding of emergence. Once assumed to be a purely passive process, spontaneously occurring as residual levels of anesthetics dwindle below a critical value, emergence from general anesthesia has been reconsidered as an active and controllable process. Emergence is driven by mechanisms that can be distinct from entry to the anesthetized state. In this narrative review, we focus on the burgeoning scientific understanding of anesthetic emergence, summarizing current knowledge of the neurotransmitter, neuromodulators, and neuronal groups that prime the brain as it prepares for its journey back from oblivion. We also review evidence for possible strategies that may actively bias the brain back toward the wakeful state.

Caffeine Accelerates Emergence from Isoflurane Anesthesia in Humans: A Randomized, Double-blind, Crossover Study

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: There are currently no drugs clinically available to reverse general anesthesia. We previously reported that caffeine is able to accelerate emergence from anesthesia in rodents. This study was carried out to test the hypothesis that caffeine accelerates emergence from anesthesia in humans.

METHODS

We conducted a single-center, randomized, double-blind crossover study with eight healthy males. Each subject was anesthetized twice with 1.2% isoflurane for 1 h. During the final 10 min of each session, participants received an IV infusion of either caffeine citrate (15 mg/kg, equivalent to 7.5 mg/kg of caffeine base) or saline placebo. The primary outcome was the average difference in time to emergence after isoflurane discontinuation between caffeine and saline sessions. Secondary outcomes included the end-tidal isoflurane concentration at emergence, vital signs, and Bispectral Index values measured throughout anesthesia and emergence. Additional endpoints related to data gathered from postanesthesia psychomotor testing.

RESULTS

All randomized participants were included in the analysis. The mean time to emergence with saline was 16.5 ± 3.9 (SD) min compared to 9.6 ± 5.1 (SD) min with caffeine (P = 0.002), a difference of 6.9 min (99% CI, 1.8 to 12), a 42% reduction. Participants emerged at a higher expired isoflurane concentration, manifested more rapid return to baseline Bispectral Index values, and were able to participate in psychomotor testing sooner when receiving caffeine. There were no statistically significant differences in vital signs with caffeine administration and caffeine-related adverse events.

CONCLUSIONS

Intravenous caffeine is able to accelerate emergence from isoflurane anesthesia in healthy males without any apparent adverse effects.

Effects of caffeine administration on sedation and respiratory parameters in patients recovering from anesthesia

Caffeine has been shown to enhance the speed of recovery from general anesthesia in murine models, though data in human patients is lacking. This is a retrospective review of intravenous caffeine administration (median dose 150 [125, 250] mg) to 151 heavily sedated patients in the post-anesthesia recovery area, to determine the association between caffeine administration and changes in sedation score, respiratory rate, and oxyhemoglobin saturation. Richmond Agitation-Sedation Scale (RASS) score, respiratory rate, and oxyhemoglobin saturation values were obtained during the 90-minute period prior to and following caffeine administration. Generalized estimating equations (GEE) with explanatory variables of time, caffeine, and the time-by-caffeine interaction were created to assess changes in the variables of interest after caffeine administration. Following the administration of caffeine, the RASS scores increased (estimate = 0.57, SE = 0.14, p < 0.001) but a trend over time or in the interaction effect was not observed, suggesting that the changes in RASS were not solely due to the recovery from anesthesia over time. No association was found between caffeine administration and changes in respiratory parameters. No adverse cardiac events were observed. Our data suggests that intravenous caffeine may enhance the speed of recovery following general anesthesia, though future prospective trials are necessary to define the optimal dose and timing of administration.