Intraoperative pathophysiological changes and therapeutic interventions in patients undergoing on-pump cardiac surgery may be risk factors for the development of postoperative Delirium. Observational Study

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Halahla, Abdallah
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An-Najah National University
Introduction: Delirium after cardiac surgery is a common complication in cardiovascular intensive care units. Estimated incidence rates are approximately 2% to 72%. Delirium is an acute organic syndrome characterized by inattention, disorientation, along with global cognitive impairment and disturbance in consciousness. Postoperative delirium is typically characterized by a varying rate and can be associated with either increased or decreased psychomotor activity. Delirium after cardiac surgery to be quite distinct from other forms of delirium for the following reasons: Different surgical Populations have different medication profiles, require different anesthesia techniques thus pharmacological triggers of delirium will vary depending on the surgery, the use of cardio-pulmonary bypass in cardiac surgeries requires special consideration since its use is associated with postoperative effects on neurotransmitter function and an increase in delirium. Research has shown that predictors of delirium appear vary depending on the surgery type and the levels of various biomarkers for delirium. Identification of risk factors of delirium is important for positive postoperative outcomes. Aim: The aims of this study are to investigate whether intra-operative events and therapeutic interventions affect the risk of postoperative delirium in patients undergoing cardiac surgery in the ICU and to determine the incidence of and risk factors for delirium in patients undergoing cardiac surgery. Material and methods: A descriptive analytical study design used; study performed at cardiac surgery units at three hospitals in Palestine. Sixty patients who underwent elective cardiac surgery are subsequently admitted to cardiac surgical ICU are enrolled into this study. A detailed clinical report form was created to collect pertinent data in order to determine the effect of pre-operative, intraoperative and postoperative variables on delirium. All subjects are screened for delirium using the RASS and CAM‑ICU test once daily, and all those who tested positive were thereafter designated as cases and the other subjects are deemed controls. Results: The percentage of patients who developed delirium right after the operation were 75.9% (41/54) of the targeted sample, the percentage continued to drop until it reached 3.7% (2 patients) in the second and third day. No relation could be detected between delirium and the demographic variables (education, smoking status, gender, marital status and age) and no relation could be detected between delirium and the pre-operative factors. Intraoperative, total amount of midazolam/mg in control group 3.31±0.398 compared to 2.41±.135 in delirium group, p= .051, (95% confidence level) and the result shows that those who did not suffer from delirium postoperative have had higher amount of midazolam. There was a significant difference at (90% confidence level) in the total amount of morphine/mg in control group (no delirium) 8.85±1.04 compared to delirium group 7.93±.45 (p= .085), those who received more morphine intra-operatively where more likely not to develop delirium after the surgery. The variable with significant relation to delirium was the use of atropine (90% confidence level) as those who seemed to use more atropine were significantly less likely to develop delirium, as in control group (not delirium) 3 (23.1%) patients received atropine compared to delirium group 1 (2.4%), p= 0.062. Regarding temperature (95% confidence level) those patients who had low grade or high temperature 19(46.3) in delirium group compared to 0(0%) in the control group (p= 0.01) were significantly more likely to develop delirium. This result indicates that low grade or high temperature postoperative is a precipitating factor for delirium. Postoperatively, bolus doses of morphine/mg (95% confidence level) as in the control (not delirium) M(SD) .00±.000 compared to 1.17±.308 in the delirium group, p= (0.001) those patients who received morphine where significantly more likely to develop delirium postoperatively. Regarding the sequential organ failure assessment score (SOFA) (90% confidence level) as those patients who scored higher SOFA in the delirium group 5.56±.191were more likely to develop delirium compared with control group (not delirium) 4.85±.390, (p= 0.083). This result indicates that higher SOFA was a precipitating factor for delirium. Hyperactive type of delirium was seen in 22/41 patients (54.7%) while 11/41 patients (25.9%) had hypoactive delirium and 6/41 (13%) patients had mixed delirium. Conclusion: A compelling percentage of cardiac surgical patients encountered delirium in ICU, broadly in its hyperactive form. Few modifiable risk factors have been determined that could lower the probability of post cardiac surgical ICU delirium. One should contemplate the use of midazolam, morphine and atropine intra-operative as protective drugs for postoperative delirium. Low and high grade fever, postoperative morphine usage and augmenting of SOFA score are precipitating factors for postoperative delirium.
Cardiac surgery , Delirium , CAM-ICU , Cardiac intensive care unit , Risk factors