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 Table of Contents  
Year : 2015  |  Volume : 52  |  Issue : 4  |  Page : 254-257

Preoperative sleep quality and inhalation anesthetic requirements: a sleep electroencephalography study

1 Department of Anesthesiology, Theodor Bilharz Research Institute, Cairo, Egypt
2 Clinical Neurophysiology Unit, Department of Neurology, Faculty of Medicine, Cairo University, Giza, Egypt
3 Department of Anesthesiology, Beni Suef University, Beni Suef, Egypt

Date of Submission18-Apr-2015
Date of Acceptance01-Jun-2015
Date of Web Publication27-Nov-2015

Correspondence Address:
Eman A Maher
Clinical Neurophysiology Unit, Department of Neurology, Faculty of Medicine, Cairo University, Giza, 11562
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1110-1083.170657

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On the night before surgery, poor sleep quality due to anxiety is a frequently encountered problem.
This study aimed at determining the effect of preoperative sleep quality on intraoperative isoflurane requirements in patients undergoing elective surgeries and also offers an electroencephalography (EEG)-based classification of sleep quality.
Patients and methods
Twenty-seven adult male patients scheduled for elective open cholecystectomy with ages ranging from 20 to 40 years were included in this study. The night before the operation, the patients were subjected to an at least 8 h sleep EEG, which was scored for the following: total sleep time, percentage of slow wave sleep, and percentage of rapid eye movement sleep. Intraoperative isoflurane requirements were determined by recording the amount of inspired isoflurane concentration (every 2 min) needed to achieve an intraoperative bispectral index value between 40 and 60. Patients were classified according to sleep EEG into good sleepers and bad sleepers. Isoflurane requirements were first correlated with the EEG and then compared between the two groups.
The inspired concentration of isoflurane in good sleepers was 1.15% (1.01-1.22%), whereas in bad sleepers it was significantly lower, at 0.99% (0.87-1.18%) (P = 0.003). There was a positive correlation between isoflurane requirements and both slow wave sleep percentage (r = 0.693; P = 0.003) and rapid eye movement sleep percentage (r = 0.687; P = 0.005).
Patients suffering from poor sleep quality on the night before surgery need less intraoperatively inspired isoflurane concentration. This finding may have clinical importance in adjusting the isoflurane dose to meet patients' requirements, avoiding intraoperative complications. In addition, an EEG-based classification of sleep is offered.

Keywords: anesthesia, isoflurane, preoperative sleep, sleep electroencephalography

How to cite this article:
Maher MA, Maher EA, Ahmed Mahmoud AA. Preoperative sleep quality and inhalation anesthetic requirements: a sleep electroencephalography study. Egypt J Neurol Psychiatry Neurosurg 2015;52:254-7

How to cite this URL:
Maher MA, Maher EA, Ahmed Mahmoud AA. Preoperative sleep quality and inhalation anesthetic requirements: a sleep electroencephalography study. Egypt J Neurol Psychiatry Neurosurg [serial online] 2015 [cited 2021 Apr 20];52:254-7. Available from: http://www.ejnpn.eg.net/text.asp?2015/52/4/254/170657

  Introduction Top

Although not identical, sleep and anesthesia have similarities such as hypnosis, amnesia, immobility, and reduced response to external stimuli [1] . These similarities are supported by data: labeled PET detects similar regional changes in brain activity during anesthesia and sleep [2] ; the bispectral index scale can monitor the depth of both anesthesia and sleep in patients without sleep disorders [3.4]; and anesthetics administered into brain areas responsible for sleep regulations produced anesthesia [5] .

Differences between states of anesthesia and sleep include ability of sleep only to meet physiological needs, which may be due to rapid eye movement sleep (REM) [6] . In addition, unlike sleep, general anesthesia is a drug-induced dose-dependent state of reduced responsiveness, which is minimally altered by environmental factors [7] . In addition, electroencephalographic (EEG) findings in both states vary widely [8] .

Previous studies concentrated on studying the correlation between induced sleep deprivation and anesthetic requirements in animals [5],[8],[9],[10] , but to the authors' knowledge this is the first study to examine the quality of preoperative sleep and its effect on the intraoperative anesthetic requirements in humans under normal conditions with no induced maneuvers.

The objectives of this study are as follows:

  1. To test the sleep and isoflurane relation hypothesis in humans, unlike the above-mentioned studies, which were carried out on rats;
  2. To investigate sleep isoflurane relation in its clinical everyday use by analyzing natural preoperative sleep (with no induced maneuvers);
  3. To extract a clinical impact from this relation; and
  4. To offer an EEG-based classification of sleep.

  Patients and methods Top


This is a prospective observational study.

After obtaining ethical committee approval from the Theodor Bilharz Research Institute and written informed consent, we studied 27 adult male patients scheduled for elective open cholecystectomy in the Theodor Bilharz Research Institute during the period from January 2012 to September 2012.

Inclusion criteria

  1. Age between 20 and 40 years.
  2. BMI 25-30.
  3. Regular sleep-wake pattern.
  4. Epworth Sleepiness Scale scores less than 5.

Exclusion criteria

  1. History suggestive of sleep disorders such as insomnia and excessive daytime sleepiness.
  2. Intake of any drugs that could affect sleep or cognition, such as stimulants, hypnotics, benzodiazepines, and antidepressants.
  3. History or evidence at clinical examination of any chronic systemic disease.

Preoperative assessments

  1. Clinical evaluation: Patients were subjected to history taking, full general and neurological examination, and laboratory workup to exclude any medical condition.
  2. Sleep diary: A sleep diary was administered for 1 week before the operation to monitor the participants' sleep-wake schedules.
  3. Epworth Sleepiness Scale [11] : Any patient with a score greater than 5 was excluded to ensure that all patients had nearly the same levels of subjective sleepiness.
  4. Sleep EEG: Patients were subjected to an EEG for at least 8 h the night before the operation (software used Nicolet V.5.3, Viasys Healthcare Inc., PA, USA). Twenty-one electrodes were applied to the scalp as per the international 10-20 system. Additional electrodes were applied to monitor eye movements as well as muscle tone. Gain was set as 30 µv/cm, paper speed at 30 mm/s, and the filter bandwidth was adjusted to 35, 1.600, and 50 Hz. EEG was manually scored for the following:
    1. Total sleep time (TST),
    2. Slow wave sleep percentage (SWS%), and
    3. REM%. According to EEG data, patients were classified into three groups:

      Group 1 (good sleepers): This group comprised those with normal sleep EEG values [12] - that is, TST equal to or more than 6 h, SWS% greater than 25%, and REM% greater than 20%.

      Group 2 (bad sleepers): This group comprised those with less than half of any of the normal values of sleep EEG - that is, TST less than 3 h, SWS% less than 12%, and REM% less than 10%.

      Group 3 (moderate sleepers): This group comprised those with values between group 1 and 2 - that is, TST between 3 and 6 h, SWS% between 12 and 25%, and REM% between 10 and 20%.
  5. Determination of intraoperative isoflurane requirements : All patients received propofol for sleep induction and fentanyl 2 µg/kg and atracurium besylate at a dose of 0.5 mg/kg bolus for induction and 0.5 mg/kg/h infusion to maintain muscle relaxation. Intraoperative isoflurane requirements were determined by recording inspired isoflurane concentration (every 2 min) needed to achieve an intraoperative bispectral index value between 40 and 60.

Statistical analyses

Pearson's correlation between isoflurane percentage and both SWS% and REM% was ascertained in good and bad sleepers. Correlation was considered significant if P value was 0.01 or less. Comparison between the two groups was made using the Mann-Whitney U-test. The data were considered significant if P-value was 0.05 or less. Statistical analysis was performed with the aid of SPSS (version 12 for Windows; SPSS Inc., Chicago, Illinois, USA).

  Results Top

There were no statistically significant differences between good and bad sleepers as regards age and BMI. The median value of the inspired concentration of isoflurane in good sleepers was 1.15% (1.01-1.22%), whereas in the bad sleepers it was significantly lower, at 0.99% (0.87-1.18%) (P = 0.003; [Table 1]).
Table 1 The difference between good and bad sleepers with regard to age and body mass index

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There was a significant positive correlation between isoflurane percentage and both SWS% (r = 0.693; P = 0.003; [Figure 1]) and REM% (r = 0.687; P = 0.005; [Figure 2]) in the studied patients.
Figure 1 Correlation between isoflurane percentage and slow wave sleep percentage (SWS%).

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Figure 2 Correlation between isoflurane percentage and rapid eye movement sleep percentage (REM%).

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  Discussion Top

Understanding the effect of sleep on anesthesia can help anesthesiologists foresee and prevent exaggerated postoperative pain in patients with a history suggestive of sleep disorders as well as assess whether anesthetics may substitute for sleep and can be used in the treatment of insomnia.

As regards isoflurane and sleep specifically, several recent studies proposed a serious hypothesis that isoflurane does not appear to satisfy the need for both REM and SWS [6],[10],[13],[14],[15] . By analyzing those studies, we see that all of them depended on animal models, especially rats. Furthermore, their argument in confirming their hypothesis was based on sleep debt [16] monitoring and induced 24 h sleep deprivation. Although these approaches were insightful, unfortunately they cannot be implemented on humans. Thus, a natural, simple, noninvasive approach is needed.

To the authors' knowledge, this is the first study investigating the relation between isoflurane and preoperative sleep in humans under no induced abnormal conditions. In addition, from this new perspective, important clinical impacts can be extracted.

First, we found that the value of isoflurane percentage is strongly correlated with SWS% and REM% - that is to say, the lower the REM% and SWS%, the lower the dose of isoflurane needed for induction of general anesthesia and vice versa. This means that bad-quality sleep on the night of surgery increases the propensity for isoflurane anesthesia. This agrees with previous studies that even mild sleep loss increases the propensity for natural sleep [17] .

Second, isoflurane dose was compared in good and bad sleepers and it was found that a decreased amount of isoflurane was required to induce general anesthesia in bad sleepers when compared with good sleepers. This finding should alert anesthesiologist to add preoperative sleep quality to their routine history taking. Bad preoperative sleep quality is a common condition due to anxiety; thus, our finding helps adjust isoflurane dose to meet patients' requirements and avoid unwanted complications.

Finally, several sleep questionnaires are commonly used for assessment of sleep quality, like the Stanford Sleepiness Scale [18] and the Epworth Sleepiness Scale [11] . Although they are subjective and depend on many variables, they are widely used in most studies because they offer numerical cutoff values for classification of sleep disorders and daytime sleepiness. Sleep EEG offers better objective numerical data for many sleep parameters like TST, SWS, REM, sleep efficiency, and number of awakenings, yet there is no agreed-upon cutoff value that defines bad or good sleep quality. In this study, we proposed an EEG-based classification of good and bad sleep quality. As sleep is an active integrative process with many compensatory mechanisms, not all sleep parameters should be within normal range to ensure good sleep quality. Since restoration of brain energy, information processing, and memory formation occur mainly in SWS and REM [19],[20] any suggested classification without including these two parameters will be lagging. In addition, there is a strong relation between SWS and sleep continuity and TST [19],[21] , and thus we added TST to our classification.

Determination of good sleepers was easy, as the normal cutoff values for the above-mentioned sleep parameters are agreed upon [12] . However, determination of bad sleepers was challenging; a wide range of below normal values exist. To overcome this problem we created a third group of patients with intermediate values; retrospectively, this group was eliminated from dose comparison. This creates better-identified good and bad sleeper groups and ensures results that are more accurate.

  Conclusion Top

To our knowledge, this is the first study to confirm the common neurophysiological mechanisms between isoflurane and REM% and SWS% in humans by studying natural sleep under no induced abnormal conditions. The median value of the inspired concentration of isoflurane in bad sleepers was significantly lower than that in good sleepers. This finding should alert anesthesiologists to add preoperative sleep quality to their routine history taking. EEG can be a useful tool in assessment of sleep quality.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1]

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