Pharmacology
Cardiovascular
Which of the following drugs is used first line for a bradyarrhythmia with adverse features:
Answer:
If there are adverse features or a risk of asystole, atropine 500 mcg IV bolus should be given. If there is an unsatisfactory response, this can be repeated every 3 - 5 mins up to a maximum dose of 3 mg. Atropine should be used cautiously in the presence of acute myocardial ischaemia or myocardial infarction as the resulting increase in heart rate may worsen ischaemia or increase the size of the infarct.Management of Bradyarrhythmias
Pharmacology / Cardiovascular
Last Updated: 4th August 2021
The approach to the management of bradyarrhythmias should follow the Resuscitation Council guidelines.
If there are no adverse features (shock, syncope, myocardial ischaemia or heart failure) and no risk of asystole (recent asystole, Mobitz II AV block, complete heart block with broad QRS, ventricular pause > 3 seconds), immediate treatment can be delayed and the patient assessed to try and identify the cause of the bradycardia.
If there are adverse features or a risk of asystole, atropine 500 mcg IV bolus should be given. If there is an unsatisfactory response, this can be repeated every 3 - 5 mins up to a maximum dose of 3 mg. Atropine should be used cautiously in the presence of acute myocardial ischaemia or myocardial infarction as the resulting increase in heart rate may worsen ischaemia or increase the size of the infarct.
If bradycardia with adverse features persists despite atropine, consider cardiac pacing. If pacing cannot be achieved promptly, consider the use of second line drugs, seek expert help to select the most appropriate choice e.g. glucagon, aminophylline, isoprenaline, adrenaline, dopamine, glycopyrrolate.
For a patient with bradycardia and adverse features, if there is no response to atropine, or if atropine is contraindicated, transcutaneous pacing should be initiated immediately. In the presence of life-threatening, extreme bradycardia, percussion pacing should be used as an interim measure until transcutaneous pacing is achieved.
Expert help should be sought and ultimately transvenous pacing arranged.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
