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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