Read the pH: below 7.35 is acidosis, above 7.45 alkalosis.
Find the value that explains it: PaCO₂ moving opposite to the pH is respiratory, HCO₃⁻ moving with the pH is metabolic.
Look at the other value: normal means uncompensated, abnormal in the compensating direction means partial compensation, and a normal pH with both abnormal means full compensation.
In a metabolic acidosis, compare PaCO₂ with Winter’s formula, 1.5·HCO₃⁻ + 8 ± 2, and calculate the anion gap Na⁺ − (Cl⁻ + HCO₃⁻).
Check a high anion gap with the delta ratio and, when albumin is low, with the corrected gap.
ECG rhythm strip interpretation
Paper (25 mm/s, 10 mm/mV)
1 small box = 0.04 s, 1 large box = 0.20 s, 10 mm = 1 mV
Heart rate, regular rhythm
300 ÷ large boxes = 1500 ÷ small boxes = 60 ÷ RR (s)
Heart rate, irregular rhythm
QRS complexes in 6 s × 10
Normal PR interval
0.12–0.20 s
Normal QRS duration
< 0.12 s
QTc (Bazett)
QT/√RR
QTc (Fridericia)
QT/∛RR
QTc (Framingham)
QT + 154·(1 − RR)
Sinus rates
bradycardia < 60, normal 60–100, tachycardia > 100 /min
Escape rates
junctional 40–60, ventricular 20–40 /min
Fast rhythms
SVT 150–250 /min (narrow), VT > 100 /min (wide)
Method
Rate: for a regular rhythm divide 300 by the large boxes or 1500 by the small boxes between two R waves; for an irregular rhythm count the QRS complexes in 6 seconds and multiply by 10.
Rhythm: compare the R–R intervals. Equal is regular; a repeating pattern is regularly irregular; no pattern at all is irregularly irregular.
P waves: is there an upright P wave in lead II before every QRS, all alike? Look for fibrillatory or sawtooth waves, inverted P waves and P waves without a QRS.
PR interval: from the start of P to the start of the QRS, normally 0.12–0.20 s and constant. Watch whether it lengthens, stays fixed before a dropped beat, or varies at random.
QRS duration: below 0.12 s is narrow; 0.12 s or more is wide. Then name the rhythm, and for the QT use QTc = QT/√RR (Bazett) with times in seconds.
Prioritization & delegation
Method
Ask what will harm the patient soonest if nothing is done.
Apply ABC (C-A-B in cardiac arrest), then Maslow: physiological needs before safety, safety before psychological needs.
Compare the options: acute before chronic, unstable before stable, unexpected before expected, systemic before local, and check each finding against the patient’s baseline.
Assess before you act unless it is an emergency; then choose the step the others depend on.
For delegation, check the five rights: task, circumstance, person, directions and supervision. Assessment, teaching and evaluation stay with the RN.
2Practice problems
1.Med-surg: cardiovascular & respiratoryMedium
A patient has had atrial fibrillation for more than 48 hours and is listed for elective cardioversion. Why is anticoagulation needed beforehand?
AAnticoagulants convert AF back to sinus rhythm
BAtrial clots may be dislodged when sinus rhythm returns
CAnticoagulants reduce the electrical energy needed for the shock
DAnticoagulants make the shock less painful
2.Med-surg: cardiovascular & respiratoryHard
A patient with a confirmed type A aortic dissection is hypertensive and tachycardic while awaiting surgery. Which drug class is usually given first to lower the heart rate and blood pressure?
AAn intravenous thrombolytic
BAn intravenous beta-blocker
CAn intravenous fluid bolus
DOral aspirin
3.Med-surg: neuro, endocrine & renalMedium
Which symptoms are typical of hypokalaemia?
ATingling lips and facial twitching
BMuscle weakness, cramps and palpitations
CExcess thirst and very high glucose
DHeat intolerance and weight loss
4.Med-surg: neuro, endocrine & renalHard
A patient on continuous overnight enteral feeding receives insulin timed to the feed. At 02:00 the tube blocks and the feed stops. What is the main risk, and what should the nurse do?
AHyperglycaemia; give an extra dose of insulin straight away
BHypoglycaemia; check glucose often and follow the plan for glucose cover
CNo risk; the insulin will simply be stored until feeding restarts
DKetoacidosis; stop all insulin until the morning
5.Med-surg: GI, perioperative & oncologyMedium
Why is a pregnancy test often done before surgery in women who could be pregnant?
APregnancy always makes surgery impossible
BAnaesthesia, drugs and some tests may harm a fetus
CPregnant women cannot sign consent forms
DIt is needed to calculate the anaesthetic drug dose
6.Med-surg: GI, perioperative & oncologyHard
After surgery, a patient keeps asking for analgesia before it is due, watches the clock and rates pain 8/10. What is the most appropriate interpretation?
APain may be undertreated; reassess and ask for a review of the plan
BThe patient is addicted and should have analgesia withheld
CThe patient is exaggerating, so the pain scores should be ignored for now
DThe patient needs only distraction and no change in drugs
7.Clinical nursingMedium
Which drug is first-line in an acute asthma attack?
AAn oral beta-blocker
BA nebulised or inhaled short-acting beta2-agonist (salbutamol/albuterol)
CA long-acting inhaled corticosteroid, used alone at a higher dose
DAn oral antihistamine such as cetirizine taken every few hours
8.Clinical nursingHard
Why are liquid medicines for nasogastric tubes drawn up in dedicated enteral (oral) syringes rather than IV syringes?
AIV syringes cannot hold liquid medicines
BEnteral syringes keep the medicine sterile
CTo prevent accidental intravenous administration
DEnteral syringes measure doses less accurately
9.Lab values & electrolytesMedium
A patient has a hot, swollen big toe. The serum uric acid is normal. Which statement is correct?
AGout is still possible, as urate can be normal in an attack
BGout can only be diagnosed with a CT scan of the foot
CGout is certain, as a normal urate proves the diagnosis
DGout is ruled out, as uric acid is always high in an attack
10.Lab values & electrolytesHard
The nurse teaches a patient who is collecting a 24-hour urine sample at home. Which statement shows a need for further teaching?
A"If I forget to save one void, I'll just carry on to the end"
B"I'll ask whether any foods or drugs should be avoided first"
C"I'll keep the container cool as the laboratory told me to"
D"I'll empty my bladder at the end time and add that urine"
11.Arterial blood gas interpretationMedium
A practice gas shows PaCO₂ 22 mmHg (2.9 kPa). Use the rule that in chronic respiratory alkalosis HCO₃⁻ falls by 5 mmol/L for every 10 mmHg that PaCO₂ is below 40, starting from HCO₃⁻ 24 mmol/L, to find the expected HCO₃⁻.
A practice gas shows a metabolic alkalosis with HCO₃⁻ 46 mmol/L. Use expected PaCO₂ = 0.7·HCO₃⁻ + 21 to find the expected PaCO₂.
HCO₃⁻ 46 mmol/L
PaCO₂ = mmHg
13.ECG rhythm strip interpretationMedium
Interpret this lead II rhythm strip. Which rhythm is it? Click your answer.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
1atrial fibrillation
2sinus bradycardia
3normal sinus rhythm
4sinus tachycardia
14.ECG rhythm strip interpretationHard
Identify the rhythm on this lead II strip. Click your answer.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
1asystole
2idioventricular rhythm
3sinus bradycardia
4junctional rhythm
15.Prioritization & delegationMedium
A patient at 35 weeks of pregnancy with high blood pressure calls the clinic. Which symptom needs urgent assessment?
AMild ankle swelling at the end of the day
BBackache after a long walk
CNeeding to pass urine more often
DA severe headache with blurred vision
16.Prioritization & delegationHard
At 08:00 a nurse has four tasks. Which order is best?
AGive routine medications, check the patient with a falling SpO₂, update care plans, give insulin with breakfast
BUpdate care plans, give insulin with breakfast, give routine medications, check the patient with a falling SpO₂
CCheck the patient with a falling SpO₂, give insulin with breakfast, give routine medications, update care plans
DGive insulin with breakfast, update care plans, check the patient with a falling SpO₂, give routine medications
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: B · Atrial clots may be dislodged when sinus rhythm returns
Why this is the answer
After 48 hours of AF, atrial thrombus may be present. Restoring organised contraction can expel it and cause a stroke. Patients are usually anticoagulated for at least three weeks before (or a transoesophageal echo excludes clot) and for at least four weeks afterwards.
Answer
B · Atrial clots may be dislodged when sinus rhythm returns
2.Med-surg: cardiovascular & respiratory
Answer: B · An intravenous beta-blocker
Why this is the answer
In acute dissection, IV beta-blockers are usually given first to reduce heart rate and the rate of rise of pressure, limiting extension of the tear. Vasodilators may follow once the heart rate is controlled. Antiplatelets, anticoagulants and thrombolytics are avoided. Type A dissection needs urgent surgery.
Answer
B · An intravenous beta-blocker
3.Med-surg: neuro, endocrine & renal
Answer: B · Muscle weakness, cramps and palpitations
Why this is the answer
Low potassium causes muscle weakness, cramps, constipation and arrhythmias. ECG changes include flattened T waves and U waves. Tingling and twitching suggest low calcium.
Answer
B · Muscle weakness, cramps and palpitations
4.Med-surg: neuro, endocrine & renal
Answer: B · Hypoglycaemia; check glucose often and follow the plan for glucose cover
Why this is the answer
If a feed stops while insulin given to cover it is still acting, the patient can become hypoglycaemic. The nurse checks glucose frequently, informs the team, restores feeding if possible and follows the prescribed plan (for example IV glucose) until feeding restarts. Basal insulin is not simply stopped in type 1 diabetes.
Answer
B · Hypoglycaemia; check glucose often and follow the plan for glucose cover
5.Med-surg: GI, perioperative & oncology
Answer: B · Anaesthesia, drugs and some tests may harm a fetus
Why this is the answer
Unknown pregnancy can change the decision to operate, the timing, and the choice of drugs and X-rays. Testing is offered with consent, according to local policy.
Answer
B · Anaesthesia, drugs and some tests may harm a fetus
6.Med-surg: GI, perioperative & oncology
Answer: A · Pain may be undertreated; reassess and ask for a review of the plan
Why this is the answer
Clock-watching often reflects inadequate analgesia. The nurse reassesses pain and function, considers multimodal options, and asks the prescriber to review the plan rather than labelling the patient.
Answer
A · Pain may be undertreated; reassess and ask for a review of the plan
7.Clinical nursing
Answer: B · A nebulised or inhaled short-acting beta2-agonist (salbutamol/albuterol)
Why this is the answer
Short-acting beta2-agonists relieve bronchospasm within minutes. Oxygen to target, steroids and other treatments are added according to severity.
Answer
B · A nebulised or inhaled short-acting beta2-agonist (salbutamol/albuterol)
8.Clinical nursing
Answer: C · To prevent accidental intravenous administration
Why this is the answer
Giving an oral or enteral medicine intravenously can be fatal. Enteral syringes with non-IV connectors, such as ENFit, make this wrong-route error much less likely.
Answer
C · To prevent accidental intravenous administration
9.Lab values & electrolytes
Answer: A · Gout is still possible, as urate can be normal in an attack
Why this is the answer
Serum urate can be normal or even low during an acute gout attack. The definitive test is joint aspiration showing needle-shaped urate crystals, which also helps rule out septic arthritis.
Answer
A · Gout is still possible, as urate can be normal in an attack
10.Lab values & electrolytes
Answer: A · "If I forget to save one void, I'll just carry on to the end"
Why this is the answer
A 24-hour collection is valid only if every void in the period is saved; if a void is lost, the nurse or clinic is told and the collection is usually restarted. Keeping the container cool as instructed, adding the final void at the end time and asking about restrictions are correct.
Answer
A · "If I forget to save one void, I'll just carry on to the end"
11.Arterial blood gas interpretation
Answer: HCO₃⁻ = 15 mmol/L
Expected compensation: in metabolic acidosis Winter’s formula predicts PaCO₂ = 1.5·HCO₃⁻ + 8 ± 2 mmHg; a measured value above that range points to an additional respiratory acidosis, below it to an additional respiratory alkalosis. The anion gap AG = Na⁺ − (Cl⁻ + HCO₃⁻), normally about 8–12 mmol/L, separates high-gap from normal-gap metabolic acidosis; low albumin hides a high gap (add 2.5 per g/dL that albumin is below 4.0). The delta ratio (AG − 12)/(24 − HCO₃⁻) between about 0.8 and 2 fits a pure high-gap acidosis (some texts use 1 instead of 0.8), below that an added normal-gap acidosis, and above 2 an added metabolic alkalosis.
Change in PaCO₂
|22 − 40| = 18 mmHg → 1.8 × 10 mmHg
Expected HCO₃⁻
HCO₃⁻ = 24 − 5·1.8 = 15 mmol/L
Answer
HCO₃⁻ = 15 mmol/L
12.Arterial blood gas interpretation
Answer: PaCO₂ = 53.2 mmHg
Expected compensation: in metabolic acidosis Winter’s formula predicts PaCO₂ = 1.5·HCO₃⁻ + 8 ± 2 mmHg; a measured value above that range points to an additional respiratory acidosis, below it to an additional respiratory alkalosis. The anion gap AG = Na⁺ − (Cl⁻ + HCO₃⁻), normally about 8–12 mmol/L, separates high-gap from normal-gap metabolic acidosis; low albumin hides a high gap (add 2.5 per g/dL that albumin is below 4.0). The delta ratio (AG − 12)/(24 − HCO₃⁻) between about 0.8 and 2 fits a pure high-gap acidosis (some texts use 1 instead of 0.8), below that an added normal-gap acidosis, and above 2 an added metabolic alkalosis.
Expected PaCO₂
0.7·46 + 21 = 53.2 mmHg
Answer
PaCO₂ = 53.2 mmHg
The rise has a limit: PaCO₂ rarely goes above about 55 mmHg from compensation alone.
13.ECG rhythm strip interpretation
Answer: sinus tachycardia
Rhythm criteria (lead II): sinus rhythm has an upright P wave before every QRS, a constant PR of 0.12–0.20 s and a narrow QRS: normal sinus rhythm at 60–100/min, sinus bradycardia below 60, sinus tachycardia above 100. Atrial fibrillation: no P waves, a fibrillatory baseline and an irregularly irregular R–R. Atrial flutter: sawtooth flutter waves at about 250–350/min with a fixed conduction ratio such as 2:1 or 4:1. First-degree AV block: sinus rhythm with a constant PR above 0.20 s. Junctional rhythm: narrow QRS at 40–60/min with absent or inverted P waves (PR below 0.12 s, or P after the QRS). A PVC is an early, wide (0.12 s or more), bizarre QRS without a P wave, with the T wave in the opposite direction and usually a full compensatory pause; in bigeminy every second beat is a PVC.
Five steps
1. Rate: R–R = 13 small boxes, 1500 ÷ 13 ≈ 115 per minute.
2. Rhythm: regular, every R–R is 0.52 s.
3. P waves: upright, one before every QRS, all alike.
4. PR interval: 0.12 s, constant, within 0.12–0.20 s.
5. QRS: 0.08 s, narrow (below 0.12 s).
Interpretation
sinus tachycardia
Answer
sinus tachycardia
14.ECG rhythm strip interpretation
Answer: idioventricular rhythm
More ventricular rhythms: torsades de pointes is a polymorphic ventricular tachycardia, usually 150–250/min, in which the wide complexes change in height and twist around the baseline, pointing up for a few beats and then down. Textbooks link it to a prolonged QT interval, and magnesium sulfate is the drug resuscitation guidelines name for it. An idioventricular rhythm is a ventricular escape rhythm: regular, wide QRS (0.12 s or more), no P waves, at 20–40/min (an accelerated idioventricular rhythm runs at 40–100/min). Monomorphic VT has identical wide complexes at more than 100/min. VF is chaotic, without any repeating complex.
Five steps
1. Rate: R–R = 49 small boxes, 1500 ÷ 49 ≈ 31 per minute.
2. Rhythm: regular, every R–R is 1.96 s.
3. P waves: none identifiable.
4. PR interval: not measurable.
5. QRS: 0.18 s, wide (0.12 s or more) and bizarre, with the T wave pointing the other way.
Interpretation
idioventricular rhythm
Answer
idioventricular rhythm
An idioventricular rhythm is an escape rhythm: the ventricles take over because the pacemakers above them have failed.
15.Prioritization & delegation
Answer: D · A severe headache with blurred vision
Why this is the answer
A severe headache and visual changes can be signs of severe pre-eclampsia and a risk of eclampsia. Mild ankle swelling, backache and frequent urination are common in late pregnancy.
Answer
D · A severe headache with blurred vision
16.Prioritization & delegation
Answer: C · Check the patient with a falling SpO₂, give insulin with breakfast, give routine medications, update care plans
Why this is the answer
A falling SpO₂ is a possible breathing problem and comes first. Insulin must be matched to the meal, routine medications have a time window, and documentation such as care plans comes last.
Answer
C · Check the patient with a falling SpO₂, give insulin with breakfast, give routine medications, update care plans