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Kattan et al, 2018;3(1):136–140.

International Journal of Medicine in Developing Countries

Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review

Mohammed Abdulaziz Kattan1*, Abdulaziz Eidhah Alnimari1, Ahmed Faisal Siraj1, Alotaibi Abdulrahman Humied1, Faisal Adel Alsuqati1

Correspondence to: Mohammed Abdulaziz Kattan

*Taif University, Taif, Saudi Arabia.

Email: dr.m.a.q [at] hotmail.com

Full list of author information is available at the end of the article.

Received: 02 October 2018 | Accepted: 18 October 2018


ABSTRACT

Over the years, postoperative cognitive dysfunction (POCD) has been considered an essential complication of cardiac surgery. Neurocognitive dysfunction can affect the quality of life and lead to social, emotional, functional, and financial problems in the patient's life. In this article, the incidence, symptoms, diagnosis, risk factors, and treatment of POCD are reviewed.


Keywords:

Postoperative cognitive dysfunction (POCD), neuroinflammation, cardiac surgery.

Introduction

Patients who undergo cardiac surgery are at risk of postoperative cognitive dysfunction (POCD). POCD is known to be an important complication of cardiac and non-cardiac surgeries with marked consequences for the quality of life, workability, and intermediate-term mortality [1].

POCD, at 3 months after surgery, indicates a 1.6 times higher rate of mortality; it also increases the risk of disability or voluntary early retirement [2]. In the United Kingdom, 26.5% of patients developed POCD after undergoing surgery for 1 week, and 9.9% of patients had POCD after 3 months [3]. Global prevalence of POCD has not been reported, mainly because POCD was not clearly defined in the published studies, and assessment methods were significantly heterogeneous in these studies [4].

Neurological complications after cardiac surgery are classified into Type-I and Type-II by the American College of Cardiology and the American Heart Association [5]. Stroke, transient ischemic attack, coma, and fatal cerebral injury are categorized among Type-I neurological complications. Delirium and POCD, including deficits of memory, concentration, and psychomotor speed are regarded as Type-II neurological deficits [6].

Risk factors for postoperative cognitive decline following cardiac surgery include advanced age, noncoronary atherosclerosis (carotid, peripheral vascular), low education level, pre-existing neurologic deficit, diabetes, adverse intraoperative, and postoperative events, and valve as opposed to Coronary artery bypass grafting surgery [7].

Clinical suspicion of POCD might be confirmed with neuropsychological testing that is completed several weeks after surgery and compared with baseline tests performed preoperatively. There is no international agreement on what test batteries should be used for the diagnosis of POCD. Different POCD studies have used a diverse compilation of neuropsychological tests, with each test reflecting different aspects of the cerebral cortex [8].

Material and Methods

Scientific websites such as PubMed, Google Scholar, and Research Gate were used to get related articles on this subject. The research process involved specific keywords: “POCD, an association between POCD and cardiac surgery, and POCD and neuroinflammation associated with cardiac surgery” to find more articles on the subject. The authors were more concerned about English published articles only which were published from 1995 to 2018.

The Incidence of Postoperative Cognitive Dysfunction (POCD) and Neuroinflammation Associated With Cardiac Surgery

POCD is now the most frequent significant neurological sequela post-cardiac surgery. Quoted incidences are dependent on varying factors: timing of measurements, the type of surgery (cardiac vs. non-cardiac), the exact assessment used, and its sensitivity. POCD can be sub-classified into short term and long term. Short-term POCD is usually transitory and is defined as cognitive decline lasting up to 6 weeks post-surgery. This occurs in 20%–50% of patients undergoing cardiac surgery. However, POCD can be long term, which is defined as a mental deterioration in cognitive function 6 months after surgery. This occurs in 10%–30% of cardiac patients [9]. As mentioned earlier, there are no gold standard tests for POCD. Hence, the incidences quoted vary greatly, and the diagnosis of POCD is not uniform. The issue of POCD is essential as patients’ perception of their general health correlates directly with neurocognitive function. POCD itself heralds a loss of independence, quality of life, and withdrawal from society. If present at 3 months after the operation, it is associated with significant long-term consequences and financial implications such as a higher risk of leaving the labor market and dependency on social welfare payments, and also increased mortality at a median of 8.5 years [10]. According to a Danish study [11], POCD only after 1 week of surgery increases the risk of leaving the labor market prematurely. POCD also leads to a prolonged hospital stay [12].

The Pathogenesis

The exact pathogenesis of POCD is unknown. Nevertheless, it can be supposed that POCD is a result of interactions between preoperative (patient-related), perioperative, and hospital-associated factors [13,14]. There is substantial evidence that inflammation plays a vital role in the development of cognitive decline and dementia in the elderly. Elevated C-reactive protein (CRP) and interleukin-6 (IL-6) were found to be the predictors of these in the general population [1518]. The potential causative factors of POCD, surgical trauma generated the inflammatory response, and blood-brain barrier (BBB) disruption had been the subject of several clinical investigations in cardiac and non-cardiac surgeries in the past [17,19,20]. These studies have confirmed a definitive inflammatory response and BBB injury after cardiac surgery in both animal and human investigations [14,1921]. However, the direct relationship between inflammatory response and POCD remains controversial [16,22].

Symptoms of POCD

In contrast to acute and, sometimes, visible onset of POD, POCD usually manifests itself as a subtle decline in cognitive functions, including memory, attention, concentration, perception, verbal function, learning, and social activities. Cognitive declines are often revealed only by a comparison of pre- and postoperative neuropsychological test scores. Therefore, subjective self-reported cognitive symptoms do not substitute for an objective cognitive evaluation [23].

The Neuropsychological Tests Used for the Diagnosis of POCD

As multiple locations of the brain can be influenced to various extents in POCD, it is essential to select an efficient combination of neuropsychological tests to evaluate several cognitive domains and to diagnose POCD correctly.

Although, as yet, there are no standardized neurocognitive test batteries routinely used for the diagnosis of POCD, a consensus meeting in 1995 advocated four core tests as detailed below [24].

Rey auditory verbal learning test for verbal memory

The examiner reads aloud a list of 15 words, and then, the participant is asked to repeat all the words he or she can remember in any order. The procedure is carried out five times. Then, a second list of 15 words is presented, and the participant attempts to recall them (only once for this time). Immediately following this, the participant is asked to remember as many words as possible from the first list.

Trail-making A and trail-making B for attention and concentration

These tests consist of 25 circled numbers or letters distributed over a sheet of paper (1–25 for Test A; 1–13 and A–L for Test B). The participant is asked to draw lines to connect circles in ascending order as quickly as possible (1-2-3-4—for Test A, 1-A-2-B-3-C—for Test B).

Grooved pegboard test for motor skills

This test involves a pegboard with 25 holes with randomly positioned slots and pegs with a key along one side. The participant is asked to pick up a peg, rotate it, and insert it to match the hole with one hand. The time to insert all of the 25 pegs correctly into the holes is measured.

Other tests

Other cognitive tests often used to diagnose POCD include the Stroop test (the word red is printed in blue ink, for example; you are asked to name the color of the ink instead of the word itself), the digit span test for short-term memory (how many digits of numbers the subject can remember), and the paper and pencil memory test for sensorimotor and recall speed. The mini-mental status examination (MMSE) takes only 5 minutes and is considered to be suitable for preoperative identification of subclinical dementia. However, the MMSE is fundamentally a screening tool and may not be sensitive enough to detect a subtle postoperative decline in cognitive function. Furthermore, the MMSE is not suitable for quantitative evaluation of POCD because there is a learning effect caused by repeated examinations.

Neurocognitive tests should be conducted by trained and qualified examiners to reduce the variance in scores that cannot be ascribed to the subjects’ ability alone. Moreover, anxiety and depression should also be assessed because these conditions are known to affect cognitive performance. Finally, it should be noted that many of the neuropsychological tests are not designed to detect the subtle cognitive impairment seen in surgical patients.

Risk Factors

The risk of POCD may be increased in older adults due to the physiologic, pharmacokinetic, and pharmacodynamic changes that are associated with aging. These changes may result in increased sensitivity and susceptibility to the insult from the surgical experience, anesthetic agents, and other drugs that are administered before, during, and after surgery and are known to cause adverse cognitive outcomes (e.g., highly anticholinergic and sedative-hypnotic drugs) [2528]. POCD after non-cardiac surgery has been associated with increased mortality, decreased quality of life, a risk of early withdrawal from the workforce, and increased dependency [29].

Treatment of POCDs

The treatment of POCDs includes two different approaches: (a) exclusion of any other severe disease that can cause organic psycho-syndrome and (b) treatment of the symptoms of POCDs. When treating patients with POCD at home or in the hospital, the first concern should be the exclusion of other diseases that can provide treatment for the underlying disease. More often, POCDs are due to drugs or latent infection induced. The meticulous record of the medication that the patient takes (whether prescribed or not and including herbal medicines) must be made, for identifying potential toxic substances that need to be discontinued or dosage reduced. Latent infections (including urinary tract infections or pneumonia) must, in the secondary level, be excluded. Electrolyte disorders, dehydration, endocrine, kidney, liver, or neurological diseases need to be investigated with diagnostic tests. It is useful that hypoglycemia would be excluded with intravenous glucose solution administration and Wernicke encephalopathy with thiamine administration before glucose in alcoholics. The treatment of symptoms of POCDs makes supportive therapy indispensable. Supportive therapy (i.e., sufficient ventilation and oxygenation, hemodynamic support) should be secured to achieve an optimal environment for recovery. In addition, the control of postoperative pain is essential, as there is a correlation between higher pain levels and the development of POCD [30]. In-patient care usually requires several non-pharmaceutical interventions. The regular measurement of vital signs and the frequent communication of the health professional team with the patient ensure that any aberrant behavior will be recorded immediately, the sleep–wake cycle will be estimated, and the intake and output of liquids during 24 hours will be calculated. Mechanical restrictions are often used in aggressive patients with manic symptoms [31]. Single-bed rooms help in reducing the stimulation. A clock mounted in a prominent position, a calendar, and watching the news on television can help reorientation. It can also be helpful in providing adequate room light with variations in light intensity for the patient to achieve a normal circadian rhythm [32]. The assessment of the ability of swallowing may become useful before the start of feeding per os. It is necessary to monitor the fluid–electrolyte balance and the respiratory and cardiovascular function [33] closely. After recovery, patients might have fragmentary memory recovery and remember events during an episode, which often causes them stress. The ability to recall facts after the end of the episode varies [34].

Conclusion

POCD is now the most frequent significant neurological sequela post-cardiac surgery. The exact pathogenesis of POCD is unknown. Elevated CRP and IL-6 were found to be the predictors of these in the general population. Clinical suspicion of POCD may be confirmed with neuropsychological testing completed several weeks after surgery and compared with baseline tests performed preoperatively. The treatment of POCDs includes two different approaches: (a) exclusion of any other severe disease that can cause organic psycho-syndrome and (b) treatment of the symptoms of POCDs.

Acknowledgment

None.


List of abbreviations

BBB Blood brain barrier

CRP C-reactive protein

IL Interleukin

POCD Postoperative cognitive dysfunction


Funding

None.


Declaration of conflicting interests

None.


Consent for publication

Not applicable.


Ethical approval

Not applicable.


Author details

Mohammed Abdulaziz Kattan1, Abdulaziz Eidhah Alnimari1, Ahmed Faisal Siraj1, Alotaibi Abdulrahman Humied1, Faisal Adel Alsuqati1

  1. Taif University, Taif, Saudi Arabia

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How to Cite this Article
Pubmed Style

Kattan MA, Alnimari AE, Siraj AF, Alotaibi AH, Alsuqati FA. Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. IJMDC. 2019; 3(1): 136-140. doi:10.24911/IJMDC/51-1538435553


Web Style

Kattan MA, Alnimari AE, Siraj AF, Alotaibi AH, Alsuqati FA. Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. https://www.ijmdc.com/?mno=10826 [Access: January 28, 2022]. doi:10.24911/IJMDC/51-1538435553


AMA (American Medical Association) Style

Kattan MA, Alnimari AE, Siraj AF, Alotaibi AH, Alsuqati FA. Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. IJMDC. 2019; 3(1): 136-140. doi:10.24911/IJMDC/51-1538435553



Vancouver/ICMJE Style

Kattan MA, Alnimari AE, Siraj AF, Alotaibi AH, Alsuqati FA. Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. IJMDC. (2019), [cited January 28, 2022]; 3(1): 136-140. doi:10.24911/IJMDC/51-1538435553



Harvard Style

Kattan, M. A., Alnimari, . A. E., Siraj, . A. F., Alotaibi, . A. H. & Alsuqati, . F. A. (2019) Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. IJMDC, 3 (1), 136-140. doi:10.24911/IJMDC/51-1538435553



Turabian Style

Kattan, Mohammed Abdulaziz, Abdulaziz Eidhah Alnimari, Ahmed Faisal Siraj, Abdulrahman Humied Alotaibi, and Faisal Adel Alsuqati. 2019. Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. International Journal of Medicine in Developing Countries, 3 (1), 136-140. doi:10.24911/IJMDC/51-1538435553



Chicago Style

Kattan, Mohammed Abdulaziz, Abdulaziz Eidhah Alnimari, Ahmed Faisal Siraj, Abdulrahman Humied Alotaibi, and Faisal Adel Alsuqati. "Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review." International Journal of Medicine in Developing Countries 3 (2019), 136-140. doi:10.24911/IJMDC/51-1538435553



MLA (The Modern Language Association) Style

Kattan, Mohammed Abdulaziz, Abdulaziz Eidhah Alnimari, Ahmed Faisal Siraj, Abdulrahman Humied Alotaibi, and Faisal Adel Alsuqati. "Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review." International Journal of Medicine in Developing Countries 3.1 (2019), 136-140. Print. doi:10.24911/IJMDC/51-1538435553



APA (American Psychological Association) Style

Kattan, M. A., Alnimari, . A. E., Siraj, . A. F., Alotaibi, . A. H. & Alsuqati, . F. A. (2019) Postoperative cognitive dysfunction (POCD) and neuroinflammation associated with cardiac surgery: a review. International Journal of Medicine in Developing Countries, 3 (1), 136-140. doi:10.24911/IJMDC/51-1538435553