Introduction Postoperative delirium POD is a potentially deb
Postoperative delirium (POD) is a potentially debilitating disorder experienced by many elderly patients admitted to a surgical intensive care unit (ICU) after noncardiac surgery. Delirium is often defined as acute cognitive dysfunction that is characterized by an altered mental status, inattention, a fluctuation of mental status, and disorganized thinking.1, 2 This complication usually occurs within 5 days of surgery, and is especially during the first 24–48 hours postoperatively. The incidence of delirium after surgery in the ICU ranges from 20–80%, depending on different study populations.4, 5, 6 POD impairs postoperative recovery, prolongs mechanical ventilation, ICU stay, and hospitalization time; increases hospital mortality rate, and leads to long-term cognitive impairment or even permanent dementia.7, 8
Despite POD being a very common problem, its pathophysiology is poorly understood and it has often been neglected in previous research. Several different mechanisms have been proposed to explain the development of POD. These include neuroinflammation, neurotransmitter dysregulation, reduction of cerebral blood flow, disruption of the blood–brain barrier, and oxidative stress.
Central nervous system (CNS) functioning depends on several neurotransmitter systems and their interactions. One neurotransmitter system is the cholinergic system, and cholinergic pathways have been implicated in the development of delirium. The activation of cholinergic receptors modulates cognition, arousal, attention, and memory. Cholinesterase (ChE) terminates the action of 17 aag by hydrolyzing this neurotransmitter to produce inactive products. The lack of these enzymes or the inhibition of cholinesterase thus causes an increase in extracellular acetylcholine. There are 2 known types of cholinesterase: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), both of which are present in blood. AChE is found in the lungs, spleen, nerve endings, gray matter of the brain, and red blood cells, while BChE is found in plasma and in different organs including the liver, pancreas, heart, and brain.
It has been reported that individuals with delirium have lower plasma levels of cholinesterase activity than controls even before surgery, suggesting that altered cholinergic function in resting conditions is a risk marker for POD13, 14; however, another report did not support these findings. Moreover, to our knowledge, there are no studies of the relationship between cholinesterase activity and POD in the Chinese Han population.
Material and Methods
Results A total of 206 patients participated in the study. The study enrollment process was outlined in Figure 1.
Discussion POD is a common complication after operations, and depends on interactions between internal and extrinsic factors. A meta-analysis published in 2017 by Yang etal, which included 24 studies and a total of 5364 cases with hip fracture surgery, showed that preoperative cognitive dysfunction, older age, cardiac insufficiency, a variety of other complications, and the application of morphine were all risk factors for POD. In the current study, age was an independent risk factor for POD, consistent with previous studies.21, 22, 23, 24 With age, the physiological functions of the CNS are degenerated, and POD is more likely to occur. The APACHE II score is based on an acute physiology score, age grading, and a chronic health evaluation. A higher APACHE II score indicates that the patient's condition is more serious. Patients with higher APACHE II scores may be more prone to POD.25, 26 Our study also showed that higher APACHE II score was a risk factor for POD. The current study focused on whether plasma cholinesterase activity was related to POD following noncardiac surgery. There are few published studies and the conclusions are not completely consistent.13, 14, In addition, there are no reports from China. In recent years, studies into the relationship between cholinesterase and many different diseases have increased. In addition to links with organophosphorus poisoning and liver disease, plasma cholinesterase is also closely related to condition and prognosis of many other diseases, such as sepsis, chronic obstructive pulmonary disease, cardiac dysfunction, multiple organ failure, obesity, and even infertility.28, 29, 30 Our results showed that activity of plasma AChE and BChE was both independent risk factors for POD in multi-factor logistic regression analyses.