Distinguishing medical from psychiatric causes of mental disorder presentations

Introduction

Emergency physicians (EPs) often assess patients with suspected mental disorder. The critical question posed is: What is causing this? Causes broadly include psychiatric, medical, intoxication and behavioural. Identifying the likely cause and careful consideration of the capability of local facilities usually leads to correct disposition, reduced morbidity and costs. EPs need a simple classification defining the principal diagnosis of the presenting mental disorder consistent with the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-V) terminology. This allows us to communicate with psychiatric colleagues and should assist diagnostic, management and disposition accuracy. Table 20.2.1 is such a suggested classification.

Medical issues are traditionally called organic. That terminology persists but is increasingly challenged by a postulated medical basis for some psychiatric disorders.

Medical clearance has been used for over 40 years, but there is still no accepted universal agreement of what that means or should entail. As a minimum, it aims to identify medical conditions causing, aggravating or co-existing with an apparent mental disorder that require medical rather than psychiatric care. Overall, the process should be considered an imperfect risk reduction strategy.

General approach

Patients with abnormal behaviour labelled as psychiatric after routine medical and psychiatric assessment frequently have a final diagnosis of a medical cause or precipitant for the mental disorder. The incidence ranges between 19% and 80%. Deciding whether a particular presentation of mental disorder is medical or psychiatric is often difficult, as there are very few absolutes that distinguish medical from psychiatric illness. Careful collection and weighting of appropriate information commonly only leads to a differential diagnosis.

Some diagnoses and dispositions can be determined quickly after a medical and psychiatric history, with the addition of a mental state and full physical examination. This sometimes takes place without diagnostic procedures. Other presentations require extensive and intensive evaluation, repeat evaluation, observation in hospital and significant investigations before the diagnosis is clear.

Medical clearance in emergency departments (EDs) can be inaccurate due to the presence of intoxicating substances or patient factors that limit assessments. A non-judgemental approach with prudent intervention based on known or likely risks, close monitoring in a safe environment and repeated assessment of physical and mental state over time are often necessary to obtain an accurate diagnosis and optimal outcome.

Studies on medical clearance by ED staff and psychiatrists have repeatedly shown a poor ability to discover medical conditions. This failure is commonly due to one or more of the following factors: inadequate history; failure to seek collateral history; poor attention to physical examination, including vital signs; absence of a reasonable mental state examination; uncritical acceptance of medical clearance by receiving psychiatric staff; and failure to re-evaluate over time. Medical conditions were most easily identified in the ED by the triage nurse or medical officer when asking whether any medical conditions existed in addition to the psychiatric complaints.

Evaluation requires a thorough approach and a commitment of time and effort. Special skills are required for medical clearance and psychiatric interview. A coordinated and focused medical and psychiatric assessment has the highest yield of correct diagnoses. Proformas or clinical pathways may improve compliance and documentation of important details, but have not demonstrated improved patient outcomes.

National Emergency Access Targets (NEAT) in Australia have changed the management in some situations. Approaches vary depending on institutional capabilities and local agreements. Detailed medical clearance for every patient is no longer universally practiced in ED. Many known psychiatric patients are now triaged directly for psychiatric assessment. Inpatient psychiatric services have, in response, taken the responsibility for medical assessment for those incompletely or not assessed in EDs. Triage screening still leaves a volume of complex patients requiring detailed medical assessment in the ED.

Triage

Triage is vital, as many apparent psychiatric presentations have medical conditions. Correct identification by nursing staff facilitates correct management and reduces morbidity and mortality. Many patients with psychiatric illness are also a significant risk to themselves or to others and require urgent intervention. Questions regarding safety should always be raised ( Box 20.2.1 ).

Nursing staff can use a triage checklist to identify presentations with high yield for organic illness ( Box 20.2.2 ). These require ED medical assessment. With local service agreement these also allow streamlined psychiatric referral without ED medical clearance for those with a known mental disorder and a low medical risk. These are based on consensus guidelines previously developed by EPs and Psychiatrists. They require vigilance by the psychiatric team to consider that a low risk of medical cause remains. They have been operating for some years without obvious increase in adverse outcomes. They are yet to be validated.

If a psychiatric diagnosis is likely, then an appropriate urgency rating by the Australasian Triage Scale for psychiatric presentations should be applied. This triage categorization for psychiatric presentations has been developed and verified and allows reasonable waiting time standards for urgency to be applied in Triage Category 2–5 ( Box 20.2.3 ). A Triage Category 1, when there is severe behavioural disturbance with immediate threat of serious violence, has been sensibly added to that scale by the Australasian College for Emergency Medicine.