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    Blood Tests & ABGs

    Dr Karan Wadhwa & Dr Tim Coughlin

    www.revise4

    finals.co.uk

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    Objectives

    Discuss

    basic blood tests

    ABGs

    Use some case examples and practicesome sample questions

    Questions

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    Why?

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    Why do blood tests?

    Haematinics

    Nutritional status

    Exposure to toxic substances Markers of infection

    Hydration status

    Renal function

    Baseline before treatment

    Etc

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    What blood tests are available

    to us? Full blood count

    Red cells, white cells, platelets

    Urea and electrolytes Sodium, potassium, urea, creatinine

    Liver function tests Bilirubin, total protein, albumin, ALP,ALT,GGT

    Inflammatory markers CRP, ESR

    Thyroid function tests TSH, T4,T3

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    Others

    Troponin I

    Calcium/magnesium/phosphate

    Glucose

    Amylase

    Clotting/INR/APTT

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    Patterns in disease

    Infective process e.g. Strep Pneumonia WCC - neutrophillia

    CRP Anaemia

    Macrocytic - High MCV

    Microcytic - Low MCV

    Normocytic - Normal MCV

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    Renal dysfunction/dehydration

    Urea

    Creatinine

    Sodium

    Poor nutrition

    Albumin/Protein

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    Liver function

    Clotting

    Jaundice Prehepatic - conjugated bilirubin, Coombs

    Hepatic - ALT

    Post hepatic - ALP/GGT

    Thyroid disease Hyperthyroidism - Low TSH, High T4

    Hypothyroidism - High TSH, Low T4

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    Arterial Blood Gases

    Procedure

    Results

    pH 7.35 - 7.45

    PCO2 4.7 - 6.0 kPa

    PO2 10.0-13.0

    HCO3 - 22.0 - 30.0

    Base excess +2 - -2

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    Logic behind blood gases

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    Metabolic acidosis - pH , CO2 (N) HCO3 With respiratory compensation, CO2 may be

    Metabolic alkalosis - pH , CO2 (N), HCO3 With respiratory compensation, CO2 may be

    Respiratory acidosis - pH , CO2 HCO3 (N)

    With metabolic compensation, HCO3 may be

    Respiratory alkalosis - pH , CO2 , HCO3 (N) With metabolic compensation, HCO3 may be

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    Case studies

    A 60 year old man was admitted with an

    exacerbation of chronic obstructive

    pulmonary disease. His arterial bloodgases on air showed:

    pH 7.29 7.35-7.45

    PaCO2 8.5 kPa 4.7-6.0

    Pao2 8.0 kPa 10-13

    HCO3 30.5 mmol/l. 22-30

    What is the acid-base disturbance and what isthe management?

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    Respiratory Acidosis

    Type 2 failure

    Treatment is nebulisers/steroids/NIV

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    A 45 year old lady with previous peptic ulcerdisease was admitted with persistentvomiting. She looked dehydrated. Her bloodresults were

    sodium 140 mmol/l 135-145

    potassium 2.5 mmol/l 3.5-5.5

    pH 7.5 7.35-7.45

    Paco2 6.0 kPa 4.7-6.0 Pao2 14 kPa 10-13.0

    HCO3 40 mmol/l. 22-30

    What is the acid-base disturbance and why? How

    would you treat this patient?

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    This patient had alkalosis due to a highstandard bicarbonate-metabolic alkalosis.

    The PaCO2 was appropriately low incompensation. This was hypokalaemichypochloraemic metabolic acidosis becauseof potassium and chloride loss from vomiting.

    Treatment was of the underlying cause(pyloric stenosis) and intravenous sodiumchloride with potassium.

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    A 58 year old lady recently underwent a lefthemicolectomy for cancer. 4 days later she

    complained of substernal abdominal pain,wasnauseous and sweaty. Her gases showed: pH 7.1 7.35 - 7.45

    PCO2 - 3.5 4.7 - 6.0

    PO2 - 18.3 10 - 13.0

    HCO3 - 13 22 - 30

    BE - -12 -2 - +2

    What would you do now? How would you

    manage this lady?

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    Practice questions

    79 year old man started on diuretics forhypertension 2 weeks ago presents with

    a seizure. Bloods: FBC, Ca2+ (N) U+Es

    Na 107

    K 3.1

    U 7.2 Cr 122

    Diagnosis?Hyponatraemia secondary to diuretic use

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    17 year old presents with confusion,dehydration, fever. T39.5, HR 120, BP

    100/50. Bloods

    FBC: Hb 13.0, WCC 19.2, Plt 180

    U+Es: Na 147, K 5.1, U 26.2, Cr 208

    Gluc: 34.9

    Diagnosis?

    Diabetic Ketoacidosis

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    47 year old lady presents withabdominal pain. Lost 3 stones over 6

    months. On examination she has apalpable gallbladder. Bloods

    FBC - Hb 8.1, MCV 69, WCC 7.5

    U+Es - Na 135, K 3.4, U 7.2, Cr 145

    LFTs - Bili 190, ALP 360, ALT 55, GGT 450

    Diagnosis?Obstructive Jaundice likely secondary to malignancy

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    28 year old Nigerian man presents tocasualty jaundiced with vomiting,

    diarrhoea. History of flu like symptoms 2weeks previously.

    LFTs - bilirubin 43, ALP 96, ALT 1522,

    GGT 45. INR 1.2Diagnosis?

    Hepatitis A most likely

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    61 year old arteriopath presents havingrecently been started on ACE inhibitors,

    with confusion and pruritis. FBC normal

    U+Es - Na 130, K 7.4, Ur 37, Cr 841

    Diagnosis?

    Renal artery stenosis

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    35 year old presents with diarrhoea,sweating and palpitations.

    FBC (N) U+E (N)

    TFTs: TSH 0.01, T4 250

    Diagnosis?

    Hyperthyroidism- Graves disease