1. An Introduction to Clinical Decision Making
Dr Graham R. Nimmo
Chair, Scottish Clinical Decision Making Special Interest Group
Clinical Skills Managed Educational Network and Scottish Clinical Skills Network
Hello and welcome to this interactive tutorial on clinical decision making. Once you have completed it you should have an enhanced idea of what is involved in CDM and hopefully will have surfaced and framed your own questions regarding cognition in the clinical context which will require further exploration both physically and into the literature. I would like to thank my colleagues in the Scottish CDM SIG for input to this work and particularly to thank Prof Pat Croskerry from Halifax, Nova Scotia for his advice, inspiration and slides!

2. Overview Intro to clinical decision making (CDM)
The five second rule: a case based CDM challenge
How do we think and make decisions?
What affects our CDM?
How can we improve CDM and enhance patient safety?
Next?
CDM is a massive subject and this short introduction aims to give you an insight to the practicalities of CDM and a window onto the theoretical basis, particularly current theories of how we make decisions. This might influence your clinical practice and teaching.

3. CDM and non-technical skills
Team working
Decision making
Situation awareness
Task management
Diagnosis
Prognosis
Decision making is one of the so-called ‘softer’ skills in clinical practice. It sits within the wider group of skills which are embraced in the terms human factors or non-technical skills and which are listed here. If you are interested in learning more about these look at the links at the end of this tutorial. There are a number of viewpoints as to which of them is most important, with some authorities viewing situation awareness as the critical element. My own take on the NTSs is that they shouldn’t be parcelled up into separate boxes but that there is overlap between the so-called domains and that decision making and communication probably flow through all of them. Diagnosis is a separate issue. The construction of a clinical picture in terms of what the underlying disease process is lies at the heart of all medicine whether the therapy is surgical, psychological, pharmacological, palliative, curative. As GH Rodger stated eloquently in his 1906 book ‘an introduction to the study of medicine’ “Medicine is a science by its means of study: it is an art by its applications”. Two branches concerning the medical art are defined: diagnosis (from Greek to know, through) and prognosis (from the Greek from, before, to know). These involve some of the most complex and difficult decisions which need to be made and often involve elements of uncertainty and judgment. More about these later.

4. CDM exercise 1 Think about your choice of speciality, profession, job
What influenced you in that decision making?
Of course decisions are made continuously in life, some trivial (HP sauce or tomato ketchup?), some monumental like ‘should I accept this job in Alaska?’ Speaking of jobs have a think about why you chose your particular career.

5. CDM exercise 2 Look at the next slide and ask yourself:
“Which beach would I rather be on?”

6. A or B ?
How did you decide that? Did you spend time and effort deciding? Or was it virtually instantaneous? More about that later…………

7. CDM in the acutely ill 21 year old with known asthma
In respiratory ward
Phone call
Decisions
Recognition
Let’s think about our assessment process for this patient and the decision making necessary. Actually seeing the patient can give a huge amount of information to the experienced clinician. Physically going to look at the patient is more valuable than hearing about them over the phone: the five second rule relates to that initial sight of the patient where their demeanour and context are added to the standard clinical and physiological assessment . This disciplined noticing can avoid cognitive biases of the telephone caller. (This is equivalent to the lesson in Dawn’s telephone scenario in the other on line introductory module : speak to/look at the patient rather than getting second hand information). Let’s go through the process. We have already made the critical decision to GO TO SEE THE PATIENT.

8. The five second rule
So to the patient: in the first few seconds our decision making and diagnostics may work in a very fast, efficient but potentially hazardous way. This is named System 1 thinking and its characteristics are listed on the next slide…

9. System 1 thinking: (intuitive)
CDM in the acutely ill
In the ward
Assessment and management
Looks….
Obs….
Actions
System 1 thinking: (intuitive)
Cognitive style Heuristic
Cognitive awareness Low
Cost Low
Automaticity High
Rate Fast
Reliability Low
Errors Usually
Effort Low
Predictive power Low
Emotional component High
Scientific rigour Low
The immediate impression is based in what we define as System 1 thinking: impulsive, immediate, urgent. In the hands of an expert this can be invaluable although still potentially risky. In the hands of a novice it is quite likely to be dangerous. It involves emotion and rapid almost ‘reflex’ decision making. If we are aware that this process is happening we can step back from our decisions and examine them, check for errors and calibrate our decision making.

10. Importance of CDM in managing sick patients
Patients still die from ‘simple’ things either missed, delayed or done sub-optimally
Decisions including diagnosis
Approx 80% of clinical time spent in the cognitive domain
Clinical decision making is one of the key activities which underpins patient safety and the quality of patient experience.

11. THE FOUR KEY DOMAINS OF EMERGENCY CARE1.
Acute assessment + stabilisation with immediate investigations and support.
Targeted secondary exam 2.
Monitors: reassess
Surface
Invasive
Real time or Delayed
Illness severity 3.
CDM
Team work
Task Mx
Situation Awareness
Critical Thinking 4.
Differential diagnosis/ definitive diagnosis
Immediate, medium term and long term treatment
We can think of a number of particular activities which need to happen simultaneously when we are dealing with a sick patient such as our young man with acute asthma: the familiar ABCDE approach is employed to help identify life threatening abnormalities which require immediate attention: usually respiratory failure (hypoxaemia with or without hypercapnia, shock, impaired conscious level or a combination of these as in severe sepsis or major trauma. Even within this standardised, structured approach there is a plethora of decisions to be made as you can see in the next few slides. In addition an assessment of illness severity must be made in order to guide the speed and level of intervention. In the next section relating to ABCDE approach and ISA the key clinical decisions are highlighted in yellow font.

12. 1. Advanced First Aid ASSESSMENT Hello, how are you ? Response
Airway: patent ?
Breathing
ACTION
Look: obstruction
Listen: ? noise
Clear or secure: headtilt/chin lift or jaw thrust? Airway: oral or nasal?
High concn oxygen: mask type? Flow?

13. 1. Advanced First Aid ASSESSMENT Sounds ? Common 3 are ? Causes are ?
ACTION
Clear and keep open
Get help 2222?
Advanced airway management required? Tracheal tube? Size? Cut to what length? Are drugs needed for anaesthesia and intubation? If yes, which?

14. For each ask ‘what is the diagnosis?’
1. Advanced First Aid
ASSESSMENT
Sounds
Nil: complete obstruction or not breathing
Snoring/gurgling: reduced GCS, foreign material
Stridor: anaphylaxis, burns/thermal; tumour; abscess/infection
For each ask ‘what is the diagnosis?’
ACTION
Clear and keep open
Get help 2222
Positioning
Advanced airway management required

15. 1. Advanced First Aid plus 2.
OBSERVE
Rate
Volume
Symmetry
Character
Work of breathing
Compromise
Ix & MONITOR
CXR, PEFR, ABGs
Repeat observations
Pulse oximetry
TREAT
Oxygen
Nebulisers

16. 1. Advanced First Aid ASSESS Pulse: which pulse?
Skin: cap refill time, temperature
BP: where? Which method?
PHYSIOLOGY
MAP = CO x SVR
CO = HR x SV
Low BP = decompensation

17. 1. Advanced First Aid iv access iv access Site Upper limb Femoral Size
Blood sampling
iv access
Upper limb
Femoral
High flow: short and thick
Fluids
Drugs

18. Wide bore peripheral cannulae
The bottom one is a straw!

19. 1. Advanced First Aid Disability ? Conscious level, focal neurology
DEFG
Difficult bit

20. IMMEDIATE INVESTIGATIONS
Arterial blood gases: O2, CO2, acid-base
Potassium
Glucose can all be done on a
Haemoglobin blood gas sample
12 lead ECG
CXR
Targeted investigations
What should we do having analysed this information?
Having a system and a routine can help reduce the cognitive load. Having a blood gas machine which can rapidly perform the most critical investigations which result in instability, and which are also rapidly improvable (usually), takes away the need to decide on them individually. The decision to obtain an arterial blood sample for analysis needs to be made and then a decision as to which artery to sample from is required. Once these and other investigations are available multiple decisions on supportive treatments (eg oxygen, ventilation, potassium, glucose, iv fluids, blood transfusion, analgesia), diagnosis and definitive treatments (eg antimicrobials, heparin, anticonvulsants and so on), prognosis, illness severity, where should they be looked after?

21. 1. Advanced First Aid Evidence Environment: context
Targeted secondary Examination
Explanation
Everything else…
For completeness here is the E of the acute approach. Where the patient is and what is happening around them may affect CDM. See the reading list to access a paper on the impact of context on decision making.

22. Advanced First Aid=Phase 1:abcde
abcde, treating as you go
Repeated assessment and continuous
monitoring: patient better or worse ?
Do we need enhanced abcde ?
Targeted secondary examination

23. THE FOUR KEY DOMAINS OF EMERGENCY CARE1.
Acute assessment + stabilisation & immediate investigations and support.
Targeted secondary exam 2.
Monitors: reassess
Surface
Invasive
Real time or Delayed
Illness severity 3.
CDM
Team work
Task Mx
Situation Awareness
Critical Thinking 4.
Differential diagnosis/ definitive diagnosis
Immediate, medium term and long term treatment
At the same time as all of this is going on with our asthma patient we need to establish monitoring: this will be determined by what is available? (context, ergonomics) and your experience, competence and capability. In severe or LT asthma a large bore iv cannula is mandatory and (ideally) an arterial line although time pressure may negate the latter.

24. Illness Severity Assessment
Speed of action needed
Level & type of expertise: resuscitation;
diagnostic; therapeutic
Where should the patient be ? Nursing
intensity, monitoring, medical input?
Definitive treatment: speed ?
Rapid illness severity assessment is needed to answer these questions…However further information may help with this as the assessment, investigations and management proceed.

25. SEVERITY SCORING 1:CLINICAL
ABNORMAL PHYSIOLOGY
Airway compromised
Resp rate
Pulse rate
SBP
GCS
OBSERVATIONS
Bad
<10 or >30
<45 or >120
<100 (110) or >200
Fall of 2 points, <15
Initially the ‘vital signs’ may be abnormal and indicate severity.

26. SEVERITY SCORING 2: INVESTIGATIONS
ABNORMAL INVESTIGATIONS
Hypoxaemia
Hypercarbia
Potassium
Glucose H+
Base excess
Lactate
RESULTS
<3 or >6 (ECG)
<3 or >20
>50 or <30
< -5 or > +10
Diagnosis ?
As investigation results become available these add further to the assessment of illness severity.

27. Relationship between base excess and mortality in ICU
Some specific results such as base deficit, lactate indicate tissue hypoxia and risk of death.
Base Excess and Mortality Red = Dead Green = survivor
ICM 2001;27:74-83

28. SEVERITY SCORING 3: organ failures
Clinical: cardiovascular (shock)
CNS reduced conscious level
Urea and creatinine: renal
ABGs: respiratory (oxygenation+/or CO2 clearance)
Clotting: coagulation
WBC: bone marrow
Gut/liver: glucose; lactate; clinical
Thirdly, as measures of specific organ systems function are reported a picture of how many organ systems are failing is built up. We know that the more systems involved the worse the patient’s outlook so this helps with prognostic decision making although

29. 4. Differential Diagnosis, ultimate diagnosis and definitive treatment
Get more history
Trachea
Chest
JVP and heart
Abdomen
Skin, CNS
GP, family, SAS
Deviation
Lateralising signs, wheeze, crackles
HS III or IV, murmurs
Swelling, pulsation
Rashes, neck stiffness, lateralising signs
the actual diagnosis (or diagnoses) and the response to both supportive and definitive treatment refines the prognostic decisions.

30. ASSESSMENT A clinical + B investigations C organ failures D diagnosis
So you can see that a number of factors (which become available over time) are required to make decisions about prognosis. An understanding of this helps in decisions to refer patients for intensive care and in discussions with relatives and friends.

31. Decision making Diagnosis (and treatment)
Is the diagnosis correct (complete) ?
Prognosis
Admit ?
Discharge ?
Stop ?
Distributed
So what other kinds of decisions are we making: some of these are listed above but I want to spend some time considering diagnostic decision making.

32. Diagnostic Error
Ranked 2nd cause of adverse events (Harvard study, 1991)
Diagnostic failure highest in EM, GP, Gen Med
Passing on to specialists in wards, ICU
2/3 of claims against UK GPs are for diagnostic failure
This area is one of uncertainty with major patient safety implications.

33. Type 2 thinking (analytical) Cognitive style Systematic
Cognitive awareness High
Cost High
Automaticity Low
Rate Low
Reliability High
Errors Few
Effort High
Predictive power High
Emotional component Low
Scientific rigour High
Diagnosis
History: full
Examination: complete
Investigations
Differential Dx
Treatment
Refine diagnosis
So in order to make the diagnosis accurate we have developed and learned a painstaking approach which involves detailed history taking, systematic clinical examination, the performance of appropriate targeted investigations to allow us to create a differential diagnosis. Treatment is then started and the response of the patient helps to inform the subsequent refining of the diagnosis. This process can be neatly aligned to the profile of type 2 thinking. It requires high cognitive awareness, is costly etc

34. Categorising Clinical Decision Making
Cognitive theory: traditional
Technical
Professional
Distributed
Traditionally theory related to clinical practice has been psychologically based on a number of cognitive paradigms. However when you look at your clinical practice you will see that there are a number of domains into which most decisions can be placed: t, p, d.

35. Traditional cognitive taxonomy or “how you think it”
Problem solving
Pattern recognition
Decision analysis theory
Hypothetico-deductive reasoning
There is a vast literature on this area but how useful these individual theories are on informing, supporting, helping our day to day CDM is not always clear.

36. CDM: a universal model of diagnostic reasoning
Intuitive
Experiential-inductive
Bounded rationality
Heuristic
Pattern recognition
Hard wired response
Thin slicing
Unconscious thinking theory
Analytical
Hypothetico-deductive
Unbounded rationality
Normative reasoning
Robust CDM
Acquired, critical, logical thought
Multiple branching/arborisation
Deliberate, purposeful thinking
However if you fit these theories into a universal model which is built around system 1 and system 2 thinking and we start to examine our day to day decision making you can start to work out which kind of thinking you are engaged in for specific decisions. And if you are making intuitive decisions you should then ask “what influences my rapid fire decision making? Remember the beach question?

37. A or B ?
How did you decide that? Using system 1 processes. But what about context? If you were an international art thief and you wanted to be inconspicuous which beach would you prefer to hide on?

38. What affects clinical decision making ?
CDM
What affects clinical decision making ?
Knowledge and skills
Behaviours: attitude (multiple selves), emotions (affect: self, family, patients, relatives, colleagues), values.
If you use system 1 processes as an expert you are often correct (remember the skin rashes? most experienced clinicians get the right diagnosis in a blink). However if you use these hardwired processes as a novice it could be way off the mark.

39. What affects clinical decision making ?
Context
Values
Affect
Knowledge
Critical thinking
Interruptions
Clinical reasoning
Words
Non-technical Skills
Physical factors
Stress and Fatigue
Ergonomics
Experience
What we hear
What we think
Cognitive biases
Heuristics
Epiphanies
Geography
Numerous factors affect decision making and this far from exhaustive list (in no particular order) gives an idea of the complexities underlying what is such an integral component of everyday clinical activity.

40. 30 Cognitive Errors after Croskerry
Aggregate bias
Gender bias
Psych-Out Errors
Anchoring
Hindsight bias
Representativeness
Ascertainment bias
Multip.Alternatives
Search satisficing
Availability
Omission bias
Sutton’s Slip
Base rate neglect
Order effects
Triage-Cueing
Commission bias
Outcome bias
Unpacking principle
Confirmation bias
Overconfidence
Vertical line failure
Diagnostic creep
Playing the odds
Visceral bias
Attribution error
Posterior prob.
Ying-Yang Out
Gambler’s Fallacy
Premature closure
Zebra retreat
One particular area which has been surfaced over the last few years is that of cognitive dispositions to respond. Pat Croskerry has catalogued and defined these innate human ‘failures of cognition’. Some are negative biases, others can be useful or detrimental. A detailed analysis of them is beyond the scope of this tutorial but to give a couple of examples: confirmation bias is where the clinician shoe-horns the patient into their preferred diagnosis; Ying-Yang Out is where boredom sets in: we have investigated this patient up and down the Ying Yang river so stop; Availability is that situation where you saw a patient with a certain condition last week so it is at the forefront of possibilities when you see a patient with similar symptoms and so on. The importance of knowing about these is that we can recognise when we are straying down one of these paths and by applying corrective processes known as cognitive forcing strategies we can avoid the biases and improve our CDM and enhance patient safety.

41. 1 2 TYPE Calibration Diagnosis TYPE Intellectual ability Hard wiring
Heuristics and Biases
Ambient conditions/Context
Task characteristics
Age and Experience
Affective state
Gender
Personality
TYPE 1
processes
RECOGNIZED
Pattern Recognition
Patient
Presentation
Pattern
Processor
Rational
override
Dysrationalia
override
Calibration
Diagnosis
Repetition
TYPE 2
processes
Putting it all together we work using both S 1 and S 2 processes all the time toggling back and forth between them with influences from all of the factors included in this schema. If we understand where we are situated cognitively we should be able to improve CDM and patient management.
NOT
RECOGNIZED
Intellectual ability
Education
Training
Critical thinking
Logical competence
Rationality
Feedback

42. THE FOUR KEY DOMAINS OF EMERGENCY CARE1.
Acute assessment + stabilisation & immediate investigations and support.
Targetted secondary exam 2.
Mons: reassess
Surface
Invasive
Real time or Delayed
Tissue hypoxia 3.
CDM
Team work
Task Mx
Situation Awareness
Critical Thinking 4.
Differential diagnosis/ definitive diagnosis
Immediate, medium term and long term treatment
So this is where we are working clinically

43. Clinician factors: Evidence Based judgment, affect, Medicine Patient
experience
Patient
Factors
these are the elements which need to be included in our approach

44. Solutions Training in critical thinking
Training in major cognitive and affective biases
Training in logical thought
Awareness of self and metacognition
Timely feedback
Training in cognitive forcing strategies
And these are some of the potential solutions and that will be where we go in the next tutorial ….

46. You can find further information including related citations at