Blood Tests & ABGs

© Dr Karan Wadhwa & Dr Tim Coughlin

www.revise4finals.co.uk

Objectives

• Discuss – basic blood tests– ABGs

• Use some case examples and practice some sample questions

• Questions

Why?

Why do blood tests?

• Haematinics• Nutritional status• Exposure to toxic substances • Markers of infection• Hydration status• Renal function• Baseline before treatment• Etc…

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

Others

• Troponin I• Calcium/magnesium/phosphate• Glucose• Amylase• Clotting/INR/APTT

Patterns in disease

• Infective process e.g. Strep Pneumonia– WCC - neutrophillia– CRP

• Anaemia– Macrocytic - High MCV– Microcytic - Low MCV– Normocytic - Normal MCV

• Renal dysfunction/dehydration– Urea– Creatinine– Sodium

• Poor nutrition– Albumin/Protein

• 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

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

Logic behind blood gases

• 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

Case studies

A 60 year old man was admitted with anexacerbation of chronic obstructivepulmonary 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 is the management?

• Respiratory Acidosis– Type 2 failure

• Treatment is nebulisers/steroids/NIV

• A 45 year old lady with previous peptic ulcer disease was admitted with persistent vomiting. She looked dehydrated. Her blood results 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? Howwould you treat this patient?

• This patient had alkalosis due to a high standard bicarbonate-metabolic alkalosis. The PaCO2 was appropriately low in compensation. This was hypokalaemic hypochloraemic metabolic acidosis because of potassium and chloride loss from vomiting. Treatment was of the underlying cause (pyloric stenosis) and intravenous sodium chloride with potassium.

• A 58 year old lady recently underwent a left hemicolectomy for cancer. 4 days later she complained of substernal abdominal pain,was nauseous 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?

Practice questions

• 79 year old man started on diuretics for hypertension 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

• 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

• 47 year old lady presents with abdominal pain. Lost 3 stones over 6 months. On examination she has a palpable 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

• 28 year old Nigerian man presents to casualty jaundiced with vomiting, diarrhoea. History of flu like symptoms 2 weeks previously.– LFTs - bilirubin 43, ALP 96, ALT 1522,

GGT 45. INR 1.2

Diagnosis?

Hepatitis A most likely

• 61 year old arteriopath presents having recently 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

• 35 year old presents with diarrhoea, sweating and palpitations.– FBC (N)– U+E (N)– TFTs: TSH 0.01, T4 250

Diagnosis?

Hyperthyroidism- Graves disease