Data Interpretation Flashcards
What is a normal pH and H+ value on an ABG?
pH 7.35-7.45
H+ 35-45
What is a normal PaO2 value on an ABG?
11-13 kPa
What is a normal PaCO2 value on an ABG?
4.7-6.0 kPa
What is a normal HCO3 value on an ABG?
22-26
Outline how interpretation of an ABG should be approached
O2 - is the patient hypoxaemic? in respiratory failure?
pH - acidotic or alkalotic
CO2 - does it match with pH? is it the cause?
HCO3 - does it match the pH? is it the cause?
Is there compensation? What is the cause of the disturbance?
How is PaO2 interpreted for a patient on O2?
PaO2 should be 10 kPa less than inspired %
E.g. 40% = 30 kPa
How is type 1 respiratory failure defined?
Hypoxaemia (<8 kPa) with normo/hypocapnia (<6)
How is type 2 respiratory failure defined?
Hypoxaemia (<8 kPa) with hypercapnia (>6)
Give 2 causes of type 1 respiratory failure
Pulmonary oedema
Bronchoconstriction
PE
Give 2 causes of type 2 respiratory failure
COPD Pneumonia Rib fracture Obesity Guillain-Barre Motor neuron disease Opiate overdose
What is the main mechanism of type 1 and type 2 respiratory failure?
1 - V/Q mismatch
2 - Alveolar hypoventilation
What is the base excess?
Surrogate marker of metabolic acidosis/alkalosis
What does a high base excess mean?
HCO3 is high - metabolic alkalosis or compensated respiratory acidosis
What does a low base excess mean?
HCO3 is low - metabolic acidosis or compensated respiratory alkalosis
Is it possible to have respiratory and metabolic acidosis or respiratory and metabolic alkalosis?
Yes
How is a mixed acidosis/alkalosis identified?
CO2 and HCO3 will move in opposite directions
Give 2 causes of respiratory acidosis
Opiates Guillain Barre COPD Asthma Iatrogenic
Give 2 causes of respiratory alkalosis
Panic attack Pain Hypoxia PE Pneumothorax Iatrogenic
Give 2 causes of metabolic acidosis
Increased acid production/ingestion
Decreased acid excretion
GI/renal HCO3 loss
Give 2 causes of metabolic alkalosis
Vomiting Diarrhoea Diuretics HF Nephrotic syndrome Cirrhosis Conn's syndrome Milk-alkali syndrome
Give 2 causes of mixed acidosis
Cardiac arrest
Multi-organ failure
Give 2 causes of mixed alkalosis
Cirrhosis with diuretic use
Hyperemesis gravidarum
Excessive ventilation in COPD
What is the anion gap, what is the normal value and how is it calculated?
Determines presence of unmeasured anions in metabolic acidosis
Normal value 4-12 mmol/L
Na - (Cl + HCO3)
Give 2 causes of an increased anion gap
DKA
Lactic acidosis
Aspirin overdose
Give 2 causes of a decreased anion gap
Diarrhoea/ileostomy
Renal tubular acidosis
Addison’s disease
Outline how spirometry/PEFR results are interpreted
FEV1/FVC ratio - if <70% then obstructive
If obstructive - FEV1 % predicted (severity) and reversibility (COPD vs asthma)
If not obstructive - FVC % predicted (low = restrictive)
How is reversibility defined on spirometry?
15% increase in FEV1
400ml increased capacity
Name 2 obstructive respiratory diseases
Asthma
COPD
Cystic fibrosis
Emphysema
Name 2 restrictive respiratory diseases
Interstitial lung disease Pulmonary oedema Chest wall deformity Neuromuscular disease Obesity Pregnancy
How do the flow/volume loops differ in appearance for restrictive and obstructive disease?
Restrictive - same as normal but smaller
Obstructive - church and steeple (COPD)
What is transfer factor? What can it be reduced by?
Measure of gas exchange in lungs
Reduced by emphysema, ILD, anaemia, pulmonary vascular disease
Give 2 causes of hypochromic microcytic anaemia
Thalassaemia Anaemia of chronic disease Iron deficiency anaemia Lead poisoning (TAIL)
Give 2 causes of macrocytic anaemia
Folate deficiency/foetus Alcoholic liver disease Thyroid (hypo) Reticulocytosis B12 deficiency Cirrhosis/cytotoxics (FAT RBC)
What is the most likely diagnosis if iron, transferrin and ferritin are all raised?
Haemochromatosis
What haematological disease may occur in someone with an autoimmune background?
Pernicious anaemia
What does a raised APTT, PT and D-dimer indicate when fibrinogen is reduced?
Disseminated intravascular coagulation
What is Churg-Strauss syndrome?
Rare systemic vasculitis affecting small-to-medium vessels which is associated with severe asthma and eosinophilia
What rare adverse drug reaction can cause platelet depletion?
Heparin induced thrombocytopaenia
What does an elevated urea and creatinine indicate?
Acute kidney injury
What does an elevated urea indicate?
Dehydration
Upper GI bleed
What does a reduced creatinine indicate?
Reduced muscle mass
What does a reduced sodium indicate?
Nephrotic syndrome Cirrhosis HF SIADH GI loss Diuretic use
What does an elevated sodium indicate?
Diabetes insipidus
Primary aldosteronism
Fluid loss (burns, D&V)
Excess saline
What does a reduced potassium indicate?
Diuretic use D&V Pyloric stenosis Cushing's syndrome Conn's syndrome
What does an elevated potassium indicate?
Drugs (K sparing diuretics, ACEi)
Rhabdomyolysis
Oliguric renal failure
Addison’s disease
What causes an elevated bilirubin?
Acute/chronic liver disease
Gilbert’s syndrome
What causes an elevated AST and ALT?
Hepatitis
What causes an elevated AST, ALT and ALP?
Gallstones
What causes an elevated GGT (when ALP is normal)?
Alcohol excess
What does an isolated rise in ALP indicate?
Paget’s disease
Bony metastases
Primary sclerosing cholangitis
What tests are used to diagnose primary biliary cholangitis?
Anti-mitochondrial antibody
Smooth muscle antibody
Serum IgM
What blood results are seen in upper GI bleed?
Increased urea (normal creatinine)
Decreased haemoglobin
Increased WCC (no infection)
Increased platelets
What TFT results indicate primary hypothyroidism?
TSH increased
T3 and T4 decreased
What TFT results indicate primary hyperthyroidism?
TSH decreased
T3 and T4 increased
Give 2 causes of reduced calcium
Vitamin D deficiency Osteomalacia Chronic kidney disease Hyperparathyroidism Acute rhabdomyolysis
Give 2 causes of raised calcium
Malignancy Sarcoidosis Thyrotoxicosis Lithium Tertiary hyperparathyroidism
What blood tests can be used to diagnose rheumatoid arthritis?
Rheumatoid factor
Anti-cyclic citrullinated peptide
What blood tests can be used to diagnose SLE?
Anti-Smith antibody
Anti-dsDNA antibody
What blood test can be used to diagnose primary biliary cirrhosis?
ANCA may be positive
What component of hepatitis B serology is a marker of infection?
SAg - surface antigen
What component of hepatitis B serology is a marker of immunity?
sAb - surface antibody
What component of hepatitis B serology is a marker of previous infection?
cAb - core antibody (IgM acute, IgG persists)
What component of hepatitis B serology is a marker of high infectivity?
eAg - e antigen
What component of hepatitis B serology is a marker of low infectivity?
eAb - e antibody
What is HBV DNA used for?
Diagnosis (along with sAg)
Monitoring response to treatment
What hepatitis B serology results would indicate previous immunisation?
Only sAb positive
What hepatitis B serology results would indicate previous infection?
cAb positive, sAg negative
What hepatitis B serology results would indicate chronic infection?
sAg and cAb positive
How is urosepsis treated?
Gentamicin
How is clostridium difficile infection treated?
Vancomycin
How is meningitis treated?
Ceftriaxone and dexamethasome
+ amoxicillin if listeria
+ benzylpenicillin if meningococcal septicaemia
What information can be obtained from the colour of urine?
Straw - normal
Dark - dehydration
Red - haematuria/rifampicin/porphyria/beetroot
Brown - bile pigment/myoglobin/antimalarials
What information can be obtained from the clarity of urine?
Clear - normal
Cloudy/debris - UTI
Frothy - protein = nephrotic syndrome
Give 3 causes of haematuria
Kidney disease Kidney stones Tumour Infection Trauma
What does bilirubin in the urine indicate?
Biliary tract obstruction
What does urobilinogen in the urine indicate?
Malaria
Haemolytic anaemia
What is the p wave?
Atrial depolarisation
What is the PR interval?
Delay between atria and ventricles
What is the QRS complex?
Ventricular depolarisation
What is the ST segment?
Isoelectric line - time between depolarisation and repolarisation of ventricles (contraction)
What is the T wave?
Ventricular repolarisation
What is the RR interval?
Time between 2 QRS complexes
What is the QT interval?
Time taken for ventricles to depolarise and repolarise
What are the chest leads?
V1-V6
What are the limb leads?
I, II, III
aVR, aVL, aVF
What leads are involved in an inferior MI? What blood vessel is affected?
II, III, aVF
Right coronary artery
What leads are involved in an anterior MI? What blood vessel is affected?
V1-V4
Left anterior descending
What leads are involved in a lateral MI? What blood vessel is affected?
I, aVL, V5, V6
Left circumflex artery
If leads II, III and aVF are affected, what is the location of the MI?
Inferior
If leads V1-V4 are affected, what is the location of the MI?
Anterior
If leads I, aVL, V5 and V6 are affected, what is the location of the MI?
Lateral
What region of the heart is supplied by the right coronary artery?
Inferior
What region of the heart is supplied by the left anterior descending artery?
Anterior
What region of the heart is supplied by the left circumflex artery?
Lateral
What is the QRS axis and how is it determined?
Average direction of ventricular depolarisation
Limb leads only
What is a normal QRS axis?
-30 to +90
What is right axis deviation?
+90 to +180
What is left axis deviation?
-30 to -90
Outline how to interpret an ECG
Check details and assess quality Heart rate Rhythm QRS axis P waves PR interval QRS complex ST segment T waves
How is heart rate interpreted on ECG?
Regular - count number of large squares between QRS complexes and divide by 300
Irregular - count number of QRS complexes on rhythm strip and multiply by 6
State if normal, bradycardic or tachycardic
How is heart rhythm interpreted on ECG?
Mark consecutive QRS complexes on a piece of paper and shift along to check if distance is the same
How is QRS axis interpreted on ECG?
Check leads I, II and III
Normal - II most positive
Right - III most positive
Left - l most positive
How are p waves interpreted on ECG?
Present or absent
Followed by QRS complexes - sinus rhythm
How is the PR interval interpreted on ECG?
Should be 120-200ms (3-5 small squares)
Prolonged - AV block
Shortened - normal or accessory pathway
What is first degree AV block?
Fixed prolonged PR interval
What is second degree (Mobitz I) AV block?
PR interval slowly increases and then QRS is dropped (Wenckebach)
What is second degree (Mobitz II) AV block?
PR interval is fixed and QRS is dropped
What is third degree AV block?
Complete
Unrelated P waves and QRS complexes
How are QRS complexes interpreted on ECG?
Normal 120ms
Width - broad = ectopic, BBB
Height - tall = ventricular hypertrophy, tall/slim person
Morphology - delta wave
What is benign early repolarisation?
J point segment exists where the S can be elevated which is normal but looks similar to ST elevation (MI)
How is the ST segment interpreted on ECG?
Elevation - acute MI
Depression - myocardial ischaemia
What is the definition of an elevated ST segment?
> 1mm (limb) or >2mm (chest) in >2 leads
What is the definition of a depressed ST segment?
> /=0.5mm in >/= leads
How are T waves interpreted on ECG?
Tall tented - hyperacute STEMI, hyperkalaemia
Inversion - in leads other than VI and III = ischaemia, BBB, PE, LV hypertrophy, illness
Biphasic - ischaemia, hypokalaemia
Flattened - ischaemia, electrolyte imbalance
What may be the first sign of an MI on an ECG?
Tall tented T waves
How can you determine if bundle branch block is left or right?
Right - V1-3
Left - V4-6
Give 2 causes of inverted T waves
Normal (VI and III) Ischaemia BBB PE LV hypertrophy Illness
What is ascites?
Accumulation of fluid in the peritoneal cavity, usually due to portal hypertension caused by cirrhosis
When is ascites clinically detectable?
Over 500mls
What are the main signs/symptoms of ascites?
Distended abdomen
Hyper-resonance on percussion
Shifting dullness
Shortness of breath (diaphragmatic splinting)
What investigation is used to confirm ascites?
Ascitic tap/paracentesis
What ascitic fluid results would indicate spontaneous bacterial peritonitis?
Cloudy Protein high (>4) WCC high (>250), neutrophil predominant SAAG low (<1.1)
What ascitic fluid results would indicate pancreatitis?
Cloudy
Amylase higher than serum
SAAG low (<1.1)
What ascitic fluid results would indicate tuberculosis?
Chylous Protein high (>4) WCC high (>250), lymphocyte predominant Glucose less than serum RCC high (>100) SAAG low (<1.1)
What ascitic fluid results would indicate malignancy?
Bloody
Glucose less than serum
RCC high (>100)
SAAG low (<1.1)
What ascitic fluid results would indicate cirrhosis?
Clear/straw WCC low (<250) SAAG high (>1.1)
What is the SAAG?
Serum ascitic albumin gradient - indirect measure of portal hypertension (serum-ascitic)
What does a high SAAG indicate?
Transudate
Portal hypertension - cirrhosis, hepatic failure
What does a low SAAG indicate?
Exudate
Inflammation - malignancy, infection
What would an ascitic fluid RCC of >100,000 indicate?
Haemorrhage
Trauma
How can lactate dehydrogenase be used to analyse ascitic fluid?
Opposite of SAAG
Low - transudate
High - exudate
CSF results are - cloudy, low glucose, high protein, neutrophils. What is the diagnosis?
Bacterial meningitis
CSF results are - clear/cloudy, normal glucose, high protein, lymphocytes (neutrophils early). What is the diagnosis?
Viral meningitis
CSF results are - low glucose, high protein, lymphocytes. What is the diagnosis?
Fungal meningitis
CSF results are - slightly cloudy, low glucose, high protein, lymphocytes. What is the diagnosis?
TB meningitis
What would be found in the CSF of a patient with a subarachnoid haemorrhage?
Blood/xanthochromia (12 hours)
High WCC/RBC/protein
Normal glucose
What would be found in the CSF of a patient with Guillain-Barre?
Clear/xanthochromia
Normal WCC/glucose
High protein
What would be found in the CSF of a patient with MS?
Clear Lymphocytes Normal glucose Mild elevation of protein Oligoclonal bands on IgG electrophoresis
How is pleural fluid characterised?
Transudate or exudate
Light’s criteria
How is pleural fluid collected?
Thoracentesis
What are the indications for pleural tap?
Pleuritic pain Breathlessness Coughing Fever Fatigue
What are the features of transudative pleural fluid?
Protein low (<30)
Yellow/clear
Few cells
Give 2 causes of transudative pleural fluid
Congestive HF
Liver cirrhosis
Nephrotic syndrome
Severe hypoalbuminaemia
What are the features of exudative pleural fluid?
Protein high (>30)
Cloudy
Increased cells
Give 2 causes of exudative pleural fluid
Malignancy
Infection (empyema due to pneumonia)
Trauma
PE
What pleural fluid type is more accurately diagnosed using Light’s criteria?
Exudative
What is Light’s criteria?
Fluid is considered exudative if any of the following:
Pleural fluid:serum protein >0.5
Pleural fluid:serum LDH > 0.61
Pleural fluid LDH >2/3rds upper limit of normal for serum value
How can synovial fluid be characterised?
Normal Non-inflammatory Inflammatory Septic Haemarthroses
Synovial fluid is - colourless, transparent, normal viscosity, <200 WBCs, <25% neutrophils, gram stain and crystals negative. What is the diagnosis?
Normal
Synovial fluid is - straw-like/yellow, translucent, increased viscosity, WBCs 200-2000, neutrophils <25%, GS and C negative. What is the diagnosis? What investigations can be done?
Non-inflammatory
Osteoarthritis, trauma
WCC/CRP, x-ray, MRI
Synovial fluid is - yellow, cloudy, decreased viscosity, WBCs 2000-50000, neutrophils >50%, GS negative, C positive. What is the diagnosis? What investigations can be done?
Inflammatory
RA, reactive/psoriatic arthritis, gout/pseudogout
CRP, urate, anti-CCP/RF, x-ray
Synovial fluid is - yellow/green, cloudy, decreased viscosity, >50000 WBCs, neutrophils >75%, GS positive, C negative. What is the diagnosis? What investigations can be done?
Septic
Staphylococcus aureus, streptococcus, neisseria gonorrhea, eschericia coli (old, IVDU)
WCC/CRP, blood/fluid culture, x-ray
Synovial fluid is - red/xanthochromic, bloody, variable viscosity, 200-2000 WBCs, neutrophils 50-75%, GS and C negative. What is the diagnosis? What investigations can be done?
Haemarthroses
Trauma, tumour, bleeding disorder
Hb, coagulation studies, x-ray
Outline how to interpret a chest x-ray
Check details
Assess technical quality - PIER
Briefly mention obvious abnormality
ABCDE or centre out and review areas
What features on an x-ray indicate heart failure?
Alveolar oedema Kerley B lines Cardiomegaly Diversion of upper lobe vessels Effusions Fluid in fissures (ABCDEF)
What features on an x-ray indicate lobar collapse?
Golden S sign - right upper lobe
Sail sign - left lower lobe
Outline how an abdominal x-ray is interpreted
Check details
Position and exposure
Obvious abnormalities
BINGSCA - bones, inflammation, gas, soft tissues, calcifications, artefacts
What does a bamboo spine on abdominal x-ray indicate?
Ankylosing spondylitis
What are lytic and sclerotic lesions?
Lytic - punched out
Sclerotic - white
What does a small bowel obstruction look like on abdominal x-ray?
Central
Lines all the way across (valvulae conniventes)
Diameter = 3cm
What does a large bowel obstruction look like on abdominal x-ray?
Peripheral
Lines not all the way across (haustra)
= 6cm in LB and = 9cm in sigmoid/caecum
What does a coffee bean sign on abdominal x-ray indicate?
Sigmoid volvulus
What does an embryo sign on abdominal x-ray indicate?
Caecal volvulus
What is Rigler’s sign on abdominal x-ray?
Pneumoperitoneum due to perforation
Double wall sign
What does an apple core sign on abdominal x-ray indicate?
Colorectal cancer
What does thumbprinting on abdominal x-ray indicate?
Colitis
What does a lead pipe colon on abdominal x-ray indicate?
Ulcerative colitis
What units should not be abbreviated on a kardex?
Micrograms
Nanograms
Units
What drugs have a separate chart?
Gentamicin
Warfarin
Insulin
Vancomycin
When should thromboprophylaxis be administered?
Evening
When should metformin be administered?
Morning (with breakfast)
When should alendronic acid be administered?
Weekly before breakfast with lots of water and sitting up for at least 30 minutes
When should statins be administered?
Night
When should diuretics be administered?
Morning
What should be prescribed on the oral and other drugs page?
Oral
Suppositories
Topical
Steroid inhaler
What should be done if prescribing antibiotics to a patient on statins?
Withhold statin for duration of antibiotic
What details should be on a prescription?
Patient - full name, address, age/DOB
Medication - name, formulation, strength, dose/instructions, quantity
Prescriber - name, authority, date
Name 2 controlled drugs
Morphine Codeine Tramadol Pregabalin Fentanyl Oxycodone
Name 3 drugs with a narrow therapeutic range
Warfarin Theophylline Phenytoin Carbamazepine Digoxin Lithium Clozapine
What signs/symptoms are associated with hypercapnia?
Confusion
Reduced conscious level
Flapping tremor
Bounding pulse
How does hyperventilation cause perioral and peripheral paraesthesia?
Alkalosis causes hypocalcaemia due to increased albumin binding of calcium
Why does vomiting lead to metabolic alkalosis?
Loss of H+ in stomach acid causing an increase in free HCO3
Volume depletion causing release of aldosterone which increases HCO3 reabsorption
How can sepsis cause metabolic acidosis?
Reduced end organ perfusion causes tissue hypoxia and cells undergo anaerobic respiration to produce lactic acid, causing metabolic acidosis
How can a cardiac arrest cause a mixed base disorder?
Respiratory acidosis caused by hypercapnia due to lack of ventilation
Metabolic acidosis caused by accumulation of anaerobic products