Factors influencing practice
The key factors thought to influence the practice of using guideline-developed criteria or clinical decision rules to determine the appropriate use and timing of a CT scan were grouped within seven theoretical domains (see Additional file
2: Table S2).
Although most senior doctors were aware of CPGs or clinical decision tools to guide CT scanning decisions for mTBI, junior doctors were less likely to know about these (Knowledge). Senior doctors reported a preference to use their clinical experience rather than a decision rule to determine the need for CT. They considered the assessment of head injury as not always objective, and decision rules or criteria could not cover all options (Beliefs about consequences). (‘I know they’ve tried to make decision rules for CT heads. In injury they don’t work very well…it completely varies and there’s no hard or fast [rules].’ ID 19.4, senior doctor). Although the majority of doctors stated that they were aware of the radiation risks associated with CT scanning and the need to reduce a patient’s exposure to ionizing radiation, particularly if they are young, they articulated concerns about missing life-threatening events. Ordering a CT scan was seen as reassuring, confirming the patient was safe for discharge. (‘It takes one person that you miss and then it’s finger pointing asking why didn’t you CT scan when it is available? It’s very hard sometimes because if you’re in a culture where they do a lot of CT scanning, the consequences of not doing it, and there is a problem, is very high.’ ID 22.3, senior doctor).
Junior doctors found the decision more difficult due to their lack of experience and were more likely to want to scan these patients (Beliefs about capabilities). (‘The hard and fast rules are great when you are learning but you’ve got to use a mix of that and your experience as well I think.’ ID 4.2, senior doctor).
The majority of doctors stated that their hospital had policies in place for junior doctors to discuss their CT scanning decision with senior members of staff. This was particularly important in regional hospitals with a high number of junior or less experienced doctors (Behavioral regulation).
A consistent finding across all interviews was the environmental context and resources of the ED and the pressure on ED staff to discharge patients quickly due to increasing ED presentations and workload. When an ED is nearing full capacity, ordering a CT scan was seen as a quicker way of discharging the patient safely. (‘People are colored by situation.. if the place is absolutely going off and you know you are going to struggle to go back in and check on that person and there are two junior nurses out there… the risk benefit for the greater good is just to scan the brain and make sure we are not missing something…our practice is impacted by the moment.’ ID: 10.1, senior doctor). The increasing availability of the CT scan was seen as a key factor influencing its increased use and the reduced need to be selective about its use. (‘The CT scan unfortunately has become like a chest x-ray. It’s become almost like a screening tool.’ ID 22.3, senior doctor).
Several doctors who were aware of clinical decision rules for mTBI thought they were complicated and difficult to remember (Memory, attention and decision processes). (‘I know they’ve tried to make decision rules for CT heads… some are too complicated to apply anyways, because there’s too many criteria.’ ID 19.4, senior doctor).
With regard to social influences, several doctors indicated that there was a changing culture in Australia to scan most adult patients with mTBI rather than observe. (‘There is a changing pattern going on here. I was going to say the more experienced but maybe the older medical staff won’t scan everyone with a period of loss of consciousness. The more junior staff will scan everybody who’s had a loss of consciousness.’ ID 25.1, senior doctor). Radiologists were infrequently consulted in the decision-making process to CT scan adults with mTBI, and it was suggested that different professional groups have different CT thresholds. Some ED doctors felt there was a pressure on them from in-patient consultants to scan the majority of patients with mTBI before admission, and specialist registrars who had been trained at trauma centres were more likely to want to scan more often.
The biggest differences between regional and metropolitan hospitals were in environmental contextual factors. Regional hospitals were less likely to have 24-hour access to a radiographer out-of-hours and therefore have to be selective about which patients receive a CT scan. These hospitals were also more likely to have a greater proportion of junior staff. In light of their circumstances, they were more likely to suggest the use of decision rules to inform the decision to CT.