Clinical Problem Solving

By Neel Shah

Problem List

• Gathering all the information from the patient via a history and physical

• But what do we do with all this information? It’s important to categorize many symptoms into a processed problem list of 5-10 things

• For example a dropping O2 Saturation and tachypnea can be categorized as acutely worsening hypoxia

Illness Script

• Disease based (Epidemiology, Time Course, Clinical Presentation, Mechanisms)

• Patient Based ( Epid, Time course, Syndrome, Other PMhx)

• Manner of learning about diseases and categorizing patients, fundamentally knowledge based

• Illness scripts should be 5-7 items long and easy to remember

Prioritized Differential Diagnosis

• Tier I – Clinically High LikelihoodDisease explains all patient’s major findingsPatient has all major manifestations of the diseaseThey have no rejecting features and may have key features

• Tier II – Clinically Moderate LikelihoodDisease explains most of the patient’s findingsPatient lacks some of the usual manifestations of the diseaseThey have no rejecting features

• Tier III- Clinically Low LikelihoodPatient has single or few features of disease in questionPatient has rejecting feature of disease in question

Pretest Probability

Tier Categorical Probability

Numerical Probability

Comment

I Very Likely

Likely

>90%

67-90%

Defining Feature

II Uncertain 34-66%

III Unlikely

Very Unlikely

10-33%

<10% Rejecting Feature

Heuristic

• In general good tests are able to move likelihood of diseases up or down one category (Uncertain to likely etc.)

• Good Tests normally over >85% Sensitivity and Specificity

• Special Cases:

• If you need to rule out a disease find a test with sensitivity >99%

• If you need to rule in a disease find a test with a specificity of >99%

• Tests are generally not necessary for very likely or very unlikely possibilities

Mrs. Triglioni

• Mrs. Triglioni is admitted to the hospital with a diagnosis of pulmonary embolism. Approximately 30 hours after the admission in the middle of the night Mrs. Triglioni got up to use the commode, strained to have a bowel movement and became short of breath and dizzy. She describes the dizziness as room spinning continuously worse when she opens her eyes or turns her head. No position feels better. When she opens her eyes she sees double. In addition she says that her right arm feels “Wobbly” and is unable to support her weigh when she tries to reposition herself after returning to bed.

Physical Exam

• BP 160/110, HR 110, 85% O2 up to 92% with supplemental oxygen

• Continues retching and holds her right eye closed because if it’s open she has double vision

• Lungs: Pleural rub is audible in left post lung field

• CVS: PMI non displaced, S1 S2 and increased P2, No murmurs

• Abdomen soft and nontender

• Left leg is markedly swollen to level of the thigh, evidence of recent knee surgery

• Eye exam is difficult because of upward beating nystagmus both eyes

• Visual acuity cannot be assessed, but CN V, VII, IX, X, II, XII appear intact but cannot assess CN VII

• Pronator drift present, reflexes intact, unable to walk because of immobilized leg

Processed Problem List

• Acutely worsening Hypoxia

• Pulmonary HTN

• Vertigo

• Diplopia

• Nystagmus

• Monoparesis Right Arm

• Truncal Ataxia

• Evidence of DVT

Patient Illness Script

• Epidemiology – 48 yo woman with DVT and PE

• Time Course: Acute

• Syndrome Statement: Hypoxia and pulmonary HTN, Central Nervous syndrome characterized by vertigo, diplopia, nystagmus, monoparesis and truncal ataxia

• Other: Surgery 3 weeks ago

Pre-Test probability

• Tier I – Recurrent PE with paradoxical Embolus and Brain Stem Stroke (Why recurrent? She was fine till using the commode then acutely dropped O2)

• Tier II

• Tier III – Benign Positional Vertigo and Meniere’s Disease

What Actually happened?

• Cross cover resident sees patient and believes she has paradoxical embolus and brain stem stroke. She orders an MRI of brain and transthoracic echo to check for patent foramen ovale

• Next day primary team checks TTE and it’s negative for patent foramen

• Resident calls and says “Good News! She didn’t have a paradoxical embolus”

• But wait.. Pre test probability was Very Likely, the Sensitivity and Specificity of the Transthoracic Echo for Paradoxical Embolus is 60% and 99%

TTE LR+ =67 (Sen/1-Spec)TTE LR - = 0.3 (1-Sen/Spec)

So a Positive result on the TTE is 67x more likely to come from someone with a PFE than someone without. While a negative result 0.3x more likely to come from someone with a PFE than someone without.

Fagan Nomogram

Types of Error

• Clinical Input Error : Wrong data was collected from patientLack of clinical encounter skills (wrong history or physical)eg: Resident or student doesn’t pick up the weak arm and misdiagnoses patient as vertigo

• Clinical Analysis Error: Right data but wrong clinical interpretationLack of knowledge :ignorance of diseaseCognitive Biases: Mental models that trip us up

System 1 Vs. System 2 Thinking

• System 1Intuitive, Automatic, FastCommon recurrent scenarios – relies on Schema (procedural (Chief Surgery resident doing central line), diagnostic (internist diagnosing HTN), pattern recognition (diagnosis) and the directions that followOften consciously activated

• Rule basedMidway between System 1 and 2, familiar situations but not common. Relies upon stored rules. Example if blood pressure doesn’t respond to three drugs it’s not essential htn. If patient remains febrile despite abx look for an abscess.

• System 2Conscious, deliberate, rational thoughtUsed in novel situations, ultimate problem solving failures, synthetic problem solvingChallenging, taxing and unsustainable

Problems continued

• System 1 Error: Slips – execution errors – System basedImbalance between monitoring checks and automatic activity, impacted by stress, fatigue, boredom, workload. Right solution chosen but outcome not what is what is intended.Distraction errors (resident interrupted reading c-xray is interrupted and misses pneumothorax), Capture Errors (anesthesiologist used to administering ab at certain rate, gets new antibiotic requires a different infusion rate)

• System 2: Mistakes – Planning errors – Rule based (good rule or wrong application), Knowledge based (strong tendency to fit problem into something we’ve seen – long term memory bias)

Cognitive Biases

• Availability Heuristic – This patient has what the last patient had..or.. Common things are common

• Confirmation Bias – Giving preferential attention to data that supports an initial diagnosis rather than refutes the initial hypothesis

• Over confidence Bias – Relying heavily on opinion of experts

• Premature Closure – Most commonly missed fracture is the second one

• Fundamental Attribution error – tendency to identify patient as cause of his/her illness

• Commission/Omission bias – tendency towards action (test ordering) or inaction