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Year : 2021  |  Volume : 15  |  Issue : 2  |  Page : 123-126

Influencing factors of early cognitive deficits after ambulatory anesthesia

1 Department of Anesthesiology, University Hospital Regensburg, Regensburg, Germany
2 Department of Anesthesiology, University Hospital Wuerzburg, Wuerzburg, Germany
3 Clinic for Anesthesiology and Intensive Care, Chemnitz Hospital, Chemnitz, Germany

Correspondence Address:
Thomas Metterlein
Anesthesiology Department, University Hospital Regensburg, 93051 Regensburg
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sja.sja_967_20

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Date of Submission21-Sep-2020
Date of Decision17-Oct-2020
Date of Acceptance20-Oct-2020
Date of Web Publication01-Apr-2021


Background: Anesthesia has an influence on early postoperative cognitive function. This is specifically relevant in ambulatory surgery. At discharge, patients must return to their normal life and manage simple tasks. Goal was to detect influencing factors of early postoperative cognitive dysfunction after ambulatory anesthesia.
Methods: With approval of the local ethics committee, 102 individuals scheduled for ambulatory anesthesia were examined with a specific test battery. Cued and uncued reaction time, divided and selective attention were tested prior to anesthesia and at the time of discharge. Differences between the two examinations and potential influencing factors including age, premedication, type and duration of anesthesia were evaluated with the Student t-test and linear regression. P < 0.05 considered significant.
Results: In all, 86 individuals completed the study. Both reaction times were reduced after anesthesia compared to before. No differences were seen for divided and selective attention. Age influenced on the post-anesthesia reaction time while all other factors did not.
Conclusion: Reaction time but not attention as more complex cognitive function is influenced by anesthesia. Age seems to be an important factor in early postoperative cognitive dysfunction.

Keywords: Anesthesia; attention; cognitive deficit; influencing factors; reaction time

How to cite this article:
Metterlein T, Wobbe T, Brede EM, Vogtner A, Krannich J, Eichelbrönner O, Broscheit J. Influencing factors of early cognitive deficits after ambulatory anesthesia. Saudi J Anaesth 2021;15:123-6

How to cite this URL:
Metterlein T, Wobbe T, Brede EM, Vogtner A, Krannich J, Eichelbrönner O, Broscheit J. Influencing factors of early cognitive deficits after ambulatory anesthesia. Saudi J Anaesth [serial online] 2021 [cited 2022 Dec 7];15:123-6. Available from:

  Background Top

Anesthesia or sedation is frequently used to provide optimal conditions for various interventions and operations. This is mainly achieved by exposure to agents that reduce alertness. While this is required during the procedure it is desired that full cognitive function is regained quickly.[1] This is especially important in an ambulatory setting.[2] Cognitive malfunction is associated with a significant risk for the patient. Every type of practical or intellectual activity can be restricted considerably through a reduced level of alertness. Alertness is particularly important to control the flow of information into the cognitive system. In our daily lives, however, more complex cognitive functions are needed. Divided attention describes the ability to operate different tasks at the same time. Multitasking is important for many activities of our daily life. Selective attention conversely describes the capability to suppress undesired reactions.[3] Both divided and selective attentions involve a more complex cognitive capability than pure alertness. Anesthesia is also capable to influence these higher functions.[1]

Ambulatory surgery has been gaining popularity. Prior studies could show that both type of surgery and a proper patient selection is important in outpatient surgery.[4] However, many procedures can be carried out in an ambulatory setting with a high success rate and very little postoperative complications.[5] Especially, in patients who are discharged shortly after the intervention a sufficient level of alertness and adequate attention is important to reduce postoperative risks.[1] Prior studies could show that after anesthesia cognitive function is reduced.[6],[7] Therefore, the patients are advised not to make any relevant decisions or actively participate in road traffic and operate machinery.[8]

To objectively measure cognitive malfunction various tests are available. The TAP-M test battery is a highly validated computer-based objective tool to assess alertness and attention. Compared to other tests it excludes memory defects, speech impediments, level of education and to a certain degree sensory and motor deficits.[9]

While various studies could demonstrate that anesthesia has an influence on early postoperative cognitive function.[4],[10] Little is known about possible influencing factors. Various anesthesia-related factors like medical premedication, duration of anesthesia, type of anesthesia (general vs. regional) and patient-related factors like gender, age and ASA physical status were assed using linear regression.

This specific study aimed to identify factors that have an influence on early postoperative cognitive malfunction in an ambulatory setting.

  Methods Top

With approval of the local ethics committee (University Wuerzburg; AZ 184/09), 102 patients scheduled for outpatient surgery at three different operative centers of the University Hospital Wuerzburg, Wuerzburg, Germany were included in the study. After prior written consent all participants were examined with the standardized TAP-M test battery (Psytest, Herzogenrath, Germany). The test took place in a quiet well-lit room without any distracting factors. Participants were seated at a table in front of the computer screen and the reaction keys. All instructions for every individual test were read to the patients while simultaneously being shown on the computer screen. Before the actual measurement all tests were practiced. A second test run was performed after surgery and immediately before discharge. Again, the tasks were explained and practiced before the actual measurement.


The TAP-M test battery is specifically designed to assess alertness and attention. It includes four subtests that evaluate various aspects.


The first two tests simply measured reaction time to an optical stimulus by pushing a reaction key. In the first test, the person should react as quickly as possible to a cross that appears on the screen (uncued reaction). The second test measures the same reaction time. The only difference is that the optical stimulus is preceded by an acoustic warning signal (cued reaction). Performance is evaluated by measuring reaction time.

Divided attention

The third test measures the ability to simultaneously process a visual and an acoustic signal. The visual task involves pushing a reaction key when figures “01” or “10” appear on the screen and not to react to similar geometrical figures. The acoustic task involves hearing alternating high (f = 2000 Hz) and low (f = 1000 Hz) beeps (di-da-di-da-di-da….). As soon as a deviation from the sequence described above occurs (same tone sounds twice, di-di or da-da) the reaction key has to be pressed. Performance is evaluated by counting the numbers of omissions.

Selective attention

The fourth test measures the ability to suppress an unwanted reaction. The individual has to react to one stimulus (a horizontal x) and ignore the other stimulus (an upright +) seen on the screen. Performance is determined based on mistakes made.

The time for the entire test is approximately 15 minutes.

Patient related (gender, age, and ASA physical status) and surgery/anesthesia-related (medical premedication, type (general/regional) and duration of anesthesia) factors were documented. Test performance was compared with a standard population and between the two test runs (Student's t-test). A linear regression was used to identify factors that influence differences between pre- and postoperative test results. Influencing factors were confirmed with a two-way ANOVA.

Statistical Analyses were accomplished with Microsoft Excel and IBM SPSS Statistics Version 19 (IBM Deutschland GmbH, Ehningen, Germany). A P <0.05 was considered statistically significant.

  Results Top

In 85 individuals, both test runs could be completed. In the remaining, 17 patients surgery was postponed and the two measurements could not be completed according to the study protocol. Biometric data are shown in [Table 1].
Table 1: Biometric data

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Preoperative alertness and attention was not different from the standard population. At the time of discharge alertness was lower compared to the standard population while divided and selective attention was not different.

Reaction times were slower at the time of discharge compared to the preoperative results. No difference was seen for divided and selective attention between the two test runs. [Table 2].
Table 2: Pre- and postoperative test results (*t-test P<0.001)

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Step-by-step linear regression showed that age had an influence on postoperative reaction time. This could be confirmed with a two-way ANOVA comparing two same size groups of younger and older individuals.

All other factors (gender, ASA physical status, medical premedication, and type (general/regional) and duration of anesthesia had no influence on postoperative alertness and attention.

  Discussion Top

Sedation and anesthesia should provide optimal operation conditions. For various reasons, a rapid recovery is desired. This is especially important in ambulatory surgery.[4] At the time of discharge the patients must be able to return to their normal lives safely and promptly. An adequate level of alertness and attention is an important factor when it comes to dealing with everyday tasks.[6] Impairment can lead to catastrophic consequences when individuals participate in road traffic or operate machinery.[8] To allow the patient to regain the preoperative cognitive state immediately short acting anesthetics are widely used in ambulatory anesthesia.[5] Depending on the substance the short action is either due to rapid distribution from central to peripheral compartments or degradation and to a lesser extend elimination.

The preoperative test revealed alertness and attention was well within the range of the standard population. This indicated that the patients were in mental good shape and well rested.[11] In patients who spend the preoperative night at the hospital even preoperatively an impaired cognitive sate is seen, mostly due to less relaxing sleep in the new environment.[1],[4]

The second examination took place at the time of discharge from the hospital about 2½ hours after completion of the surgical procedure. All patients felt comfortable and awake enough to leave the hospital. Similar to other studies a relevant influence on the patient's alertness could be demonstrated.[7] A comparison of preoperative and postoperative reaction time proves an influence of anesthesia and/or surgery. At that time point, the anesthetic was most likely not completely eliminated from the patient. It, however, still remains unclear if low anesthetic concentrations or other factors like physical stress, pain or an inflammatory reaction are responsible for the postoperative changes.[12]

Interestingly, only alertness was impaired during hospital discharge. Higher cognitive functions like divided and selective attention were not impaired. Multitasking and impulse suppression were not influenced 2½ hours after the procedure. It might be possible that higher cognitive functions involving different neuronal structured are capable to compensate a reduced alertness. Decision making might be influenced simply by increased focusing on the examined task. It was not compared if the answers in the attention tests were slower after anesthesia. On the other hand, it might just be easier to measure a simple time than more complex wright or wrong decision. Therefore, significance could have been reached easier.

One important new finding in this study was that variations on post-anesthesia alertness mainly depend on the patient's age. All other examined factors did not reach significance. Apparently, an older patient's cognitive function does not regenerate as quickly compared to a younger patient's. A very similar phenomenon is seen with other forms of interference. The older patients with cerebral trauma are the less likely it is that pre-trauma cognitive levels can be resumed.[13] Sleep deprivation also leads to a higher cognitive impairment in older individuals.[14] Another possible explanation is that anesthetic effects last longer due to decreased drug clearance with increasing age.[15],[16]

Interestingly, the type of anesthesia had no influence on early postoperative cognitive dysfunction. Individuals with regional anesthesia did not perform better compared to those with general anesthesia. However, all patients with regional anesthesia either had a medical premedication or received sedating substances during the operation. It remains an interesting observation that the higher amount of anesthetic substances for general anesthesia had no deteriorating effect on postoperative alertness. Similarly, the duration of anesthesia with higher cumulative dosages for longer procedures had no influence. This supports the assumption that not anesthesia per se but the combination of anesthesia and surgery leads to postoperative cognitive impairment.[10] Additional factors like physical stress, pain or inflammatory responses seem to have an independent influence.[12] Variation in anesthesia technique can improve early postoperative cognitive function.

  Conclusion Top

Reaction time but not higher cognitive functions like divided and selective attention are influenced by anesthesia and surgery in ambulatory patients at discharge. Age could be identified as the only relevant influencing factor for early postoperative cognitive dysfunction.


ASA American society of anesthesiologists

POCD postoperative cognitive deficit

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Table 1], [Table 2]


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