**2.3 Delirium work up**

*Perioperative Care for Organ Transplant Recipient*

specific for diagnosing delirium [21].

validated screening tools for assessing for the presence of delirium. The gold standard for diagnosis of delirium is a formal evaluation performed by a psychiatrist using The Diagnostic and Statistical Manual of Mental Disorders criteria; however, the application and feasibility of a formal psychiatric evaluation is not clinically practical [1]. More commonly used methods of delirium screening utilize nursing expertise for frequent and consistent bedside screening. The Richmond Agitation Sedation Scale (RASS) is a widely used screening tool to evaluate and communicate patients' level of sedation and arousal [20]. With an appropriate level of consciousness, there are many validated tools for delirium screening. Importantly, a patient must be arousable to voice (i.e. RASS score of −1) to be able to screen for delirium. The most commonly used tool for screening is the Confusion Assessment Method for Intensive Care Unit (CAM-ICU) [21]. The CAM-ICU (**Figure 2**) is an abbreviated version of the Confusion Assessment Method. The CAM-ICU tool screens for acute changes in mental status, inattention, disorganized thinking and altered level of consciousness in a condensed approach ideal for a fast paced clinical setting. The CAM-intensive care unit screening tool requires less than 2 min to complete and in addition to being rapidly applied, has been shown to be 93% sensitive and 98%

Other screening tools include the Nursing Delirium Symptom Checklist (NuDESC) [22], Confusion Assessment method (CAM) [23] and the Intensive Care Delirium Screening Checklist (ICDSC) [24]. The multiple, validated tools available speaks to the importance for using a tool of any type to achieve consistent screening. More important than which tool to use is having a program in place for regular, routine, and consistent screening. If delirium is not screened for using a validated screening tool, delirium may be missed up to 75% of the time [25–28], especially in the setting of hypoactive delirium. Given the fluctuating course of critically

*Delirium screening tool and flowchart outlining the confusion assessment method for the intensive care unit [2].*

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**Figure 2.**

Following a positive screening evaluation for delirium, working through a differential diagnosis to identify treatable underlying causes is essential. In the transplant population in the setting of immunosuppression, infection is an extremely important diagnosis to consider and rule out in a timely manner. Immunosuppressed patients do not have a robust systemic inflammatory response as compared to non-immunosuppressed, post-operative patients, so infections present in a more discreet and subtle manner, often with mental status changes as the only clinical symptomatology. In a patient with new onset delirium, initial work up should include a comprehensive laboratory evaluation including a complete blood count, comprehensive metabolic panel, liver function tests, lipase and amylase. In the post-transplant recipient where renal dysfunction and electrolyte fluctuations are common, a basic metabolic panel should also be obtained to ensure that uremia or an underlying electrolyte disturbance is not present. Hormone dysregulation should also be considered as a cause of delirium with laboratory evaluation of thyroid function and the pituitary–adrenal axis. The patient's medication list should also be reviewed to ensure that medication toxicity is not contributing or exacerbating the mental status changes. However, in the immunosuppressed, post-operative transplant recipient with clinical decompensation highlighted by new onset mental status changes, sepsis needs to be at the top of the differential diagnosis.

Mental status changes are often the initial presenting symptom of an underlying infection or sepsis in the transplant population. Blood cultures, urine cultures, and a chest x-ray should be obtained to rule out bacteremia, urinary tract infection or pneumonia, respectively. In addition, based on the operative details and time since surgery, cross sectional axial imaging should be considered to rule out a deep space infection or other possible surgical complications. Importantly, early initiation of broad-spectrum antibiotics is strongly recommended if there is any concern that an underlying infection is contributing to the mental status changes.

If surgical drains are present, evaluating the character of the abdominal fluid is important to rule out intra-abdominal pathology. Organ specific evaluation of surgical drains is an important step in evaluating for potential infectious sources. In the setting of liver transplant, drains should be evaluated for elevated bilirubin to rule out a biloma and anastomotic biliary complication. In pancreas recipients, drain amylase and bilirubin should be obtained to evaluate for a pancreatic parenchyma leak and/or an enteric anastomotic leak. If clinically applicable in kidney transplant recipients, drain fluid should be checked for creatinine to evaluate for a possible urine leak. Drain fluid studies should be correlated with high resolution, axial imaging to further define the anatomic location of potential fluid collections to determine if percutaneous drainage or open drainage is needed.

Furthermore, the work up should include placing the patient on a pulse oximeter to obtain an oxygen saturation and obtain an arterial blood gas to ensure that hypoxia or hypercarbia is not causing or contributing to the mental status changes.

Myocardial infarctions and cerebral vascular events can also present with delirium. An electrocardiography, troponins and a possible echocardiography should be obtained if there is a concern for a cardiac event. If there is clinical suspicion for a stroke based on neurologic exam, a non-contrast and subsequently contrasted cerebral, cross sectional imaging should be obtained. In addition, an electroencephalography should be performed if there is clinical concern for seizure activity or postictal metal status changes.

Mental status changes in the transplant recipient can be caused by multiple contributing factors, and a systematic and thoughtful work up is paramount for rapid initiation of treatment. However, the work up for delirium is often negative for any treatable, underlying medical condition. Once all potential medical conditions that can contribute to delirium are evaluated and eliminated as the diagnosis, the focus should shift to optimizing the environment for delirium resolution and cognitive recovery.
