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Interpreting Investigations Part b Bassant Abdelfadeel & Amitoj HeerObjectives ◦ To learn systematic approaches to interpreting formal blood results and ABGs. ◦ To use these systematic approaches to work through some examples and identify important pathological findings at each part of the system. ◦ To practise applying this learning to tackling common clinical scenarios.FORMAL BLOODS Interpretation Systematic Approach 1. Confirm patient identity 2. Check formal bloods details 3. Identify obvious abnormality 4. Systematically review: ◦ FBC ◦ CRP ◦ U+Es ◦ LFTs ◦ Clotting ◦ Other tests 5. Consider clinical question Images: https://www.cvphysiology.com/Arrhythmias/A009; https://ecg.utah.edu/lesson/1 FBC A 60 year old man presents to MAU with chest pain. Your senior asks you to clerk in this patient What questions would you like to ask ?FBC Test Result Range A 60 year old man presents to MAU with chest pain. WCC 9.8 4-11 A clinical assessment reveals: Hb 78 115-160 ◦ Central chest pain ◦ Ongoing PR bleeding and weight loss which he hasn’t seen his GP about Plts 288 150-450 ◦ PMH - IHD, T2DM, HTN ◦ NEWS 0; Alert and chatty MCV 77 80-100 ◦ Normal ECGFBC Test Result Range A 60 year old man presents to MAU with chest pain. WCC 9.8 4-11 A clinical assessment reveals: Hb 78 115-160 ◦ Central chest pain ◦ Ongoing PR bleeding and weight loss which he hasn’t seen his GP about Plts 288 150-450 ◦ PMH - IHD, T2DM, HTN ◦ NEWS 0; Alert and chatty MCV 77 80-100 ◦ Normal ECGFBC Test Result Range A 60 year old man presents to MAU with chest pain. WCC 9.8 4-11 A clinical assessment reveals: ◦ Central chest pain Hb 78 115-160 ◦ Ongoing PR bleeding and weight loss which he hasn’t seen his GP about ◦ PMH - IHD, T2DM, HTN Plts 288 150-450 ◦ NEWS 0; Alert and chatty ◦ Normal ECG MCV 77 80-100 Acute severe anaemia can be a cause of unstable angina/ NSTEMI What type of anaemia?Anaemia MCV normal = 80-100 femtolitres (fl) microcytic anaemia (<80 fl) normacytic anaemia (80-100 macrocytic anaemia (>80 fl) fl) - iron deficiency decrease in reticulocyte increase in non- - sideroblastic count= can't reticulocyte count = megablastic anemia megablastic anaemia produce these are on the blood film = will anemia on - chronic enough RBCs. conditions where see large immature blood film inflammatory disease the body is trying to RBC and compensate by hypersgmented - thalassaemia - bone marrow producing more neutrophils - alcohol abuse disorders such as RBCs. - hypothyrodism aplastic anaemia to help differentiate between (suspect if low wcc -heamolytic anemia - B12 deficiency -pregnancy them you need to do your iron or low platelet in anaemia -Myelodysplastic studies (ferritin and transferrin. normocytic anaemia) - blood loss syndrome ferritin is low and transferrin is - renal failure -anaemia of chronic - folate deficiency (myelodysplasia) high in iron def anaemia and disease anaemia sideroblastic anaemia. For - drug induced e.g thalassameia you do the - preganancy from methotrexate or haemiglonipathy screen. -sickle cell anaemia phenytoin or hydroxycarbamideFBC A 72 year old man is directly admitted to oncology. You are oncall and the nurses ask you to see patient as he looks unwell and has got a new rash.FBC Test Result Range A 72 year old man is directly admitted to WCC 3.6 4-11 oncology. HB 91 115-160 A clinical assessment reveals: MCV 90 80-100 ◦ Lethargy and weakness PLT 15 150-450 ◦ PMH – Lung cancer; Last chemotherapy dose administered one week ago Neut 1.62 1.8- 8.0 ◦ NEWS 1 for tachycardia at 110 Lymph 0.97 1-4 ◦ Purpuric patches on forearms but no active bleeding Mono 0.17 0.2-0.8 Eosino 0.4 Baso 0.07FBC Test Result Range A 72 year old man is directly admitted to WCC 3.6 4-11 oncology. HB 91 115-160 A clinical assessment reveals: MCV 90 80-100 ◦ Lethargy and weakness PLT 15 150-450 ◦ PMH – Lung cancer; Last chemotherapy dose administered one week ago Neut 1.62 1.8- 8.0 ◦ NEWS 1 for tachycardia at 110 Lymph 0.97 1-4 ◦ Purpuric patches on forearms but no active bleeding Mono 0.17 0.2-0.8 Eosino 0.4 Baso 0.07FBC Test Result Range A 72 year old man is directly admitted to WCC 3.6 4-11 oncology. HB 91 115-160 A clinical assessment reveals: MCV 90 80-100 ◦ Lethargy and weakness PLT 15 150-450 ◦ PMH – Lung cancer; Last chemotherapy dose administered one week ago Neut 1.62 1.8- 8.0 ◦ NEWS 1 for tachycardia at 110 Lymph 0.97 1-4 ◦ Purpuric patches on forearms but no active bleeding Mono 0.17 0.2-0.8 Pancytopenia secondary to chemotherapy Eosino 0.4 Neutropenic sepsis Baso 0.07CRP and U+Es An 82 year old woman presents to Test Result Range AMU with a cough. WCC 16 4-11 HB 109 115-160 A clinical assessment reveals: CRP 74 <5 ◦ Worsening confusion Creat 110 50-95 ◦ Recently started on treatment for CAP by her GP Urea 7.5 2.5-7.8 ◦ PMH – Heart failure, Asthma Na 127 135-145 K+ 3.1 3.5-5.3 Alb 30 35-50 ALP 216 Bili 15CRP and U+Es An 82 year old woman presents to Test Result Range AMU with a cough. WCC 16 4-11 HB 109 115-160 A clinical assessment reveals: CRP 74 <5 ◦ Worsening confusion Creat 110 50-95 ◦ Recently started on treatment for CAP by her GP Urea 7.5 2.5-7.8 ◦ PMH – Heart failure, Asthma Na 127 135-145 K+ 3.1 3.5-5.3 Alb 30 35-50 ALP 216 Bili 15CRP and U+Es An 82 year old woman presents to Test Result Range AMU with a cough. WCC 16 4-11 HB 109 115-160 A clinical assessment reveals: CRP 74 <5 ◦ Worsening confusion Creat 110 50-95 ◦ Recently started on treatment for CAP by her GP Urea 7.5 2.5-7.8 ◦ PMH – Heart failure, Asthma Na 127 135-145 K+ 3.1 3.5-5.3 Worsening CAP causing delirium Alb 30 35-50 Hyponatremia ?cause ALP 216 Bili 15Hyponatraemia Fluid balance Negative fluid Positive fluid Equal fluid balance balance balance Hypovolaemic Hypervolemic Euvolaemic hyponatraemia hyponatraemia hyponatraemia - GI tract loss i.e N+v/ skin - CHF Durgs- Other- -CKD SIADH diuretics, hyperglycaemia - 3rd space loss i.e SSRIs, PPIs, , hyperlipidemia sepsis, pancreatitis, GI - liver failure antipsychotics obstruction - Primary adrenal Insufficiency LFTs Hepatic (hepatocellular injury) vs post hepatic (cholestasis) causes Hepatic Post-hepatic Causes Hepatitis, ALD, NAFLD PBC, PSC Which LFT is most abnormal? AST, ALT GGT, ALP Measures of function: 1. Bilirubin – conjugated vs unconjugated 2. Albumin 3. ClottingCLOTTING Condition PT /INR APTT Bleedingtime Vitamin K deficiency Prolonged Normal Normal or warfarin DIC Prolonged Prolonged Prolonged (due to decreased fibrinogen) Von willebrand Unaffected Unaffected Prolonged disease Haemophilia Unaffected Prolonged Normal Liver failure early Prolonged Unaffected Normal End stage liver failurProlonged Prolonged Prolonged Factor V/X deficiency Prolonged Prolonged Normal Factor XII deficiency Unaffected Prolonged Normal Aspirin administrationNormal Normal Prolonged (due to decreased fibrinogen) Heparin Normal Prolonged Normal Cause Factors affected Heparin Prevents activation factors 2,9,10,11 Warfarin Affects synthesis of factors 2,7,9,10 DIC Factors 1,2,5,8,11 Liver disease Factors 1,2,5,7,9,10,11OTHER TESTS A 75 year old woman presents to ED Test Result Range with SOB. WCC 15.2 4-11 Hb 160 115-160 A clinical assessment reveals: CRP 1 <5 ◦ A rapid onset of SOB while climbing the stairs, then Naeling 137 125-145 hot and sweaty with progressively worsening breathing ◦ No fever / chest pain / collapse K+ 5.2 3.5-5.3 ◦ Ex-smoker Creat 58 d- dimer 3.1 <0.5 Trop 1144OTHER TESTS A 75 year old woman presents to ED Test Result Range with SOB. WCC 15.2 4-11 Hb 160 115-160 A clinical assessment reveals: CRP 1 <5 ◦ A rapid onset of SOB while climbing the stairs, then Naeling 137 125-145 hot and sweaty with progressively worsening breathing ◦ No fever / chest pain / collapse K+ 5.2 3.5-5.3 ◦ Ex-smoker Creat 58 d- dimer 3.1 <0.5 Trop 1144OTHER TESTS A 75 year old woman presents to ED Test Result Range with SOB. WCC 15.2 4-11 Hb 160 115-160 A clinical assessment reveals: CRP 1 <5 ◦ A rapid onset of SOB while climbing the stairs, then Naeling 137 125-145 hot and sweaty with progressively worsening breathing ◦ No fever / chest pain / collapse K+ 5.2 3.5-5.3 ◦ Ex-smoker Creat 58 d- dimer 3.1 <0.5 Trop 1144VBGs Case 1: pH 7.29 A 25 year old woman presents to ED with dizziness, 3.61 clamminess and abdominal pain.. Lac2 0.79 HCO3 13.1 A clinical assessment reveals: Hb 123 ◦ PMH – T1DM K 3.8 ◦ SHx – Lives in London but here on holiday and forgot 134 her BM monitoring equipment Ionised Ca 1.15 Lac 0.7 Glu 21.9 Creat 67VBGs Case 2: pH 7.22 A 71 year old woman presents with wheeze PvO2 5.6 and pleuritic chest pain. PvCO2 9.2 Bicarb 33 A clinical assessment reveals: K 3.6 ◦ PMH – COPD (previous home NIV), severe Na 131 frailty, T2DM, OSA Lac 1.4 Glu 9.0ABG Interpretation Systematic APPROACH 1. Confirm patient identity 2. Check ABG/VBG details 3. Consider clinical context and identify obvious abnormality 4. Systematically review: ◦ Oxygen ◦ pH ◦ Respiratory component ◦ Metabolic component ◦ Compensation ◦ Other results 5. Consider clinical question Imaghttps://upload.wikimedia.org/wikipedia/commons/1/1b/Implantable_cardioverter_defibrillator_chest_X-CLINICAL CONTEXT ◦ Why has the ABG been done? ◦ How much oxygen is the patient on? ◦ Are there any previous ABGs/VBGs for comparison? Imahttps://commons.wikimedia.org/wiki/File:Pleural_effusion_-OXYGEN Case 1: pH 7.42 (7.35-7.45) Tom is a 65 year old man who is COVID pCO2 5.0 (4.6-6.4) positive presents to ED with SOB. He is on pO2 7.8 (11.0-14.4) room air. HCO3 25.0 (22-26) Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg OXYGEN Case 1: pH 7.42 (7.35-7.45) Tom is a 65 year old man who is COVID positive pCO2 5.0 (4.6-6.4) presents to ED with SOB. He is on room air. pO2 7.8 (11.0-14.4) His ABG shows: HCO3 25.0 (22-26) ◦ Oxygen – Hypoxaemic ◦ pH – NAD ◦ Respiratory component - NAD ◦ Metabolic component - NAD ◦ Compensation - NAD ◦ Other results - NAD Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg OXYGEN Case 1: pH 7.42 (7.35-7.45) Tom is a 65 year old man who is COVID positive pCO2 5.0 (4.6-6.4) presents to ED with SOB. He is on room air. pO2 7.8 (11.0-14.4) His ABG shows: HCO3 25.0 (22-26) ◦ Oxygen – Hypoxaemic ◦ pH – NAD ◦ pCO2 - NAD ◦ Metabolic component - NAD ◦ Compensation - NAD ◦ Other results - NAD Type 1 respiratory failure – GIVE HIM SOME OXYGEN! Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg HYPOXIA Causes: 1. Not enough oxygen in the alveoli – either the concentration is reduced or there is no air at all. 2. Increased diffusion distance – something is in the way eg. fluid (pulmonary oedema/ARDS), pus, fibrosis. 3. Lack of perfusion eg. PE, other emboli. OXYGEN Case 2: pH 7.39 (7.35-7.45) Nigel was admitted to hospital with a pCO2 4.8 (4.6-6.4) SOB and is requiring 60% O2 via a venturi mask. pO2 11.5 (11.0-14.4) HCO3 24.0 (22-26) His ABG shows: ◦ Oxygen – requiring supplementary oxygen ◦ pH – NAD ◦ pCO2 – NAD ◦ HCO3 - NAD ◦ Compensation - NAD Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgOXYGEN Case 2: Later in the evening, Nigel is now on 15L O2 via a non-rebreathe mask. He’s sat up in bed and appears scared and SOB with a RR 40. Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgOXYGEN Case 2: pH 7.52 (7.35-7.45) Later in the evening, Nigel is now on pCO2 3.0 (4.6-6.4) 15L O2 via a non-rebreathe mask. He’s pO2 8.0 (11.0-14.4) sat up in bed and appears scared and HCO3 25.0 (22-26) SOB with a RR 40. Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg OXYGEN Case 2: pH 7.52 (7.35-7.45) Later in the evening, Nigel is now on 15L O2 pCO2 3.0 (4.6-6.4) via a non-rebreathe mask. He’s sat up in bed pO2 8.0 (11.0-14.4) and appears scared and SOB with a RR 40. His ABG shows: HCO3 25.0 (22-26) ◦ Oxygen – Hypoxic despite maximal O2 ◦ pH – Alkalotic ◦ Respiratory component – Respiratory alkalosis ◦ Metabolic component - NAD ◦ Compensation - NAD ◦ Other results - NAD Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgOXYGEN Case 2: An hour later, Nigel is still on 15L O2 via a non-rebreathe mask but he’s lying back in bed and appears more settled with a RR 25. Imahttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgOXYGEN Case 2: pH 7.39 (7.35-7.45) An hour later, Nigel is still on 15L O2 pCO2 5.2 (4.6-6.4) via a non-rebreathe mask but he’s lying pO2 5.8 (11.0-14.4) back in bed and appears more settled HCO3 25.0 (22-26) with a RR 25. Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg OXYGEN Case 2: pH 7.39 (7.35-7.45) An hour later, Nigel is still on 15L O2 pCO2 5.2 (4.6-6.4) via a non-rebreathe mask but he’s lying pO2 5.8 (11.0-14.4) back in bed and appears more settled HCO3 25.0 (22-26) with a RR 25. Actively dying of respiratory failure Imahttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgCase 3: pH 7.31 (7.35-7.45) A morbidly obese 70 year old woman pCO2 9.9 (4.6-6.4) with chronic back pain is admitted with pO2 6.2 (11.0-14.4) a fall and AKI. She is on room air. HCO3 31.0 (22-26) Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg Case 3: pH 7.31 (7.35-7.45) A morbidly obese 70 year old woman pCO2 9.9 (4.6-6.4) with chronic back pain is admitted with a fall and AKI. She is on room air. pO2 6.2 (11.0-14.4) HCO3 31.0 (22-26) Her ABG shows: ◦ Oxygen – Hypoxic ◦ pH – Acidotic ◦ Respiratory component – Respiratory acidosis ◦ Metabolic component – High Bicarb ◦ Compensation – Partially compensated ◦ Other results - NAD Imaghttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg Case 3: pH 7.31 (7.35-7.45) A morbidly obese 70 year old woman with chronic back pain is admitted with a fall and AKI. pCO2 9.9 (4.6-6.4) She is on room air. pO2 6.2 (11.0-14.4) Her ABG shows: HCO3 31.0 (22-26) ◦ Oxygen – Hypoxic ◦ pH – Acidotic ◦ Respiratory component – Respiratory acidosis ◦ Metabolic component – High Bicarb ◦ Compensation – Partially compensated ◦ Other results - NAD Acute on chronic type 2 respiratory failure Imagehttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg Respiratory acidosis Causes: 1. Drugs 2. CNS disturbance 3. O2 in T2RF 4. Neuromuscular disease 5. Chest wall problems 6. Gas exchange problems 7. Airway obstruction ANYTHING THAT REDUCES VENTILATIONCOMPENSATION ◦ Respiratory compensation is fast, metabolic compensation is slow ◦ Compensation will not overcorrect, at best will make the pH just within the normal range. ◦ A CO2 level above 7.5 will not be achieved by compensation. Imaghttps://commons.wikimedia.org/wiki/File:Pleural_effusion_-Case 4 Case 4: pH 7.33 (7.35-7.45) A 23 year old woman is admitted with pCO2 2.21 (4.6-6.4) abdominal pain and reduced pO2 15 (11.0-14.4) consciousness. HCO3 17 (22-26) Imahttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpg Case 4 Case 4: pH 7.33 (7.35-7.45) A 23 year old woman is admitted with pCO2 2.21 (4.6-6.4) abdominal pain and reduced consciousness. pO2 14 (11.0-14.4) HCO3 17 (22-26) Her ABG shows: ◦ Oxygen – NAD ◦ pH – Acidotic ◦ HCO3 – low, in keeping with metabolic acidosis ◦ pCO2 - low ◦ Compensation – Partial compensation Imahttps://commons.wikimedia.org/wiki/File:X-ray_of_lobar_pneumonia.jpgANION GAP ◦ How? Formula uses Na, Cl, Bicarb and albumin. ◦ Na+ + K+ - (Cl- + HCO3-) ◦ Raised anion gap: excess acid from somewhere 1. Endogenous: ketoacids, lactic acid 2. Exogenous: Ethylene glycol or methanol poisoning. Salicylate overdose ◦ Normal anion gap: 1. Loss of bicarb ◦ GI: diarrhoea, high output stomas, NGTs, fistulae ◦ Renal ◦ Drugs 2. Inability to properly excrete acid ◦ Renal acidosis Imagehttps://commons.wikimedia.org/wiki/File:Pleural_effusion_-Other results ◦ Haemoglobin – Compare it to previous results ◦ Potassium – Could be high or low. ◦ Glucose - Could be high or low, but low is the one you must check for. ◦ Lactate – Marker of severity. Can help explain a metabolic acidosis. Imaghttps://commons.wikimedia.org/wiki/File:Pleural_effusion_-SummaryKey Learning Points ◦ For formal bloods interpretation: ◦ You always have time to look up the guidelines ◦ Prioritise – some things can be left for the day team – or their GP! ◦ Look at the trend ◦ VBGs are more useful than you think ◦ For ABG interpretation: ◦ Use the system in context with the clinical situation. ◦ Increase the oxygen flow if the pO2 is low ( be aware of the risk of worsening a T2RF) ◦ Consider if processing your data would be useful, ie Aa gradient or Anion gap. ◦ Take an overview of it all and make a plan. ◦ Be honest with yourself and ask for advice if you don’t understand or are unsure what to do with the results you have obtained.Questions