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 with heart failure starts spironolactone in addition to an ACE inhibitor. Which blood result needs close monitoring?
AHaemoglobin, because both drugs can cause bleeding
BCalcium, because both drugs can lower it
CGlucose, because both drugs can cause hypoglycaemia
DPotassium, because both drugs can raise it
2.Med-surg: cardiovascular & respiratoryHard
A patient with a confirmed pulmonary embolism has BP 78/50 mmHg despite fluids, and the right ventricle is dilated on echocardiography. Which treatment is most likely?
AOral apixaban only, started next week
BAn inhaled bronchodilator
CCompression stockings and bed rest
DSystemic thrombolysis
3.Med-surg: neuro, endocrine & renalMedium
A patient has hypertension that is hard to control and a persistently low potassium, without taking diuretics. Which condition should be considered?
ACranial diabetes insipidus
BPrimary hypothyroidism
CPrimary hyperaldosteronism (Conn's)
DPrimary adrenal insufficiency (Addison's)
4.Med-surg: neuro, endocrine & renalHard
Which task can the registered nurse delegate to a trained healthcare assistant (nursing assistant)?
ADeciding the dose of correction insulin from the glucose result
BChecking pre-meal glucose and reporting results out of range
CTeaching a new patient how to inject insulin
DAssessing a confused patient whose glucose is 2.6 mmol/L (47 mg/dL)
5.Med-surg: GI, perioperative & oncologyMedium
How should pancreatic enzyme replacement capsules usually be taken?
AOnly on days with abdominal pain
BOnce a day at bedtime
COne hour after meals, on an empty stomach
DWith every meal and snack
6.Med-surg: GI, perioperative & oncologyHard
A nurse teaches a patient with chronic pancreatitis. Which statement shows a need for further teaching?
A"I should not drink any alcohol."
B"Oily, floating stools may mean my dose needs changing."
C"I'll report increased thirst or passing urine more often."
D"I'll take my enzyme capsules at bedtime."
7.Clinical nursingMedium
A patient with type 1 diabetes has blood glucose of 25 mmol/L, deep rapid breathing and ketones in the urine. What is the likely diagnosis?
ANormal glucose fluctuation
BHypoglycaemia
CDiabetic ketoacidosis
DHyperosmolar hyperglycaemic state without ketones
8.Clinical nursingHard
A patient with a central venous catheter suddenly becomes breathless and hypotensive while the line is being disconnected with the patient sitting up. What complication is most likely?
AAir embolism
BPneumonia
CHypoglycaemia
DPhlebitis
9.Lab values & electrolytesMedium
A patient has a sodium of 124 mEq/L, a headache and new confusion. Which nursing measure is most appropriate?
AGive the next dose of the prescribed thiazide diuretic early
BEncourage the patient to drink plenty of plain water
CPut seizure precautions in place and monitor neurological status
DKeep the patient flat and limit neurological checks to once a shift
10.Lab values & electrolytesHard
During an IV magnesium sulfate infusion, which assessment best detects toxicity early?
ABowel sounds and abdominal girth
BBlood glucose and pupil size every hour
CSkin color and capillary refill every hour
DKnee reflexes, respiratory rate and urine output
11.Arterial blood gas interpretationMedium
A practice gas shows PaCO₂ 49 mmHg (6.5 kPa). Use the rule that in acute respiratory acidosis HCO₃⁻ rises by 1 mmol/L for every 10 mmHg that PaCO₂ is above 40, starting from HCO₃⁻ 24 mmol/L, to find the expected HCO₃⁻.
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
2supraventricular tachycardia (SVT)
3ventricular tachycardia
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
1torsades de pointes
2ventricular fibrillation
3ventricular tachycardia
4asystole
15.Prioritization & delegationMedium
A patient’s peripheral IV site is swollen, pale and cool, and the infusion has slowed. What should the nurse do first?
AIncrease the infusion rate to overcome the resistance
BStop the infusion and remove the cannula
CApply a tight bandage over the site to reduce swelling
DFlush the cannula hard to clear the blockage
16.Prioritization & delegationHard
A patient has full-thickness burns all the way around the chest and is finding it harder to breathe, although the airway is clear. What does this suggest?
AThe burns are healing and the skin is tightening normally
BThe patient has had too little IV fluid and needs a fast bolus to improve the breathing
CThe tight burned skin is restricting chest movement, so an escharotomy may be needed
DThe patient is anxious and only needs reassurance
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: D · Potassium, because both drugs can raise it
Why this is the answer
ACE inhibitors reduce aldosterone production and spironolactone blocks its receptor, so both reduce potassium excretion. Together they can cause dangerous hyperkalaemia, especially with impaired renal function. Potassium and renal function are monitored, and potassium supplements are usually avoided.
Answer
D · Potassium, because both drugs can raise it
2.Med-surg: cardiovascular & respiratory
Answer: D · Systemic thrombolysis
Why this is the answer
A PE causing sustained hypotension is high-risk and usually treated with thrombolysis to dissolve the clot quickly, unless contraindicated, when surgical or catheter removal may be used. Stable patients are usually treated with anticoagulation alone.
Answer
D · Systemic thrombolysis
3.Med-surg: neuro, endocrine & renal
Answer: C · Primary hyperaldosteronism (Conn's)
Why this is the answer
Excess aldosterone causes sodium and water retention (hypertension) and potassium loss (hypokalaemia). Primary hyperaldosteronism is a common secondary cause of hypertension and is screened for with the aldosterone-to-renin ratio. Addison's disease causes the opposite pattern.
Answer
C · Primary hyperaldosteronism (Conn's)
4.Med-surg: neuro, endocrine & renal
Answer: B · Checking pre-meal glucose and reporting results out of range
Why this is the answer
Trained assistants can measure and record glucose and report abnormal results. Dose decisions, teaching and the assessment of an unstable patient need the registered nurse.
Answer
B · Checking pre-meal glucose and reporting results out of range
5.Med-surg: GI, perioperative & oncology
Answer: D · With every meal and snack
Why this is the answer
Pancreatic enzymes digest fat, protein and carbohydrate, so they are taken with meals and snacks. The dose is adjusted to reduce steatorrhoea and support weight gain.
Answer
D · With every meal and snack
6.Med-surg: GI, perioperative & oncology
Answer: D · "I'll take my enzyme capsules at bedtime."
Why this is the answer
Pancreatic enzymes must be taken with meals and snacks to digest them. Alcohol must be avoided, steatorrhoea suggests under-replacement, and thirst or polyuria can signal diabetes from loss of islet cells.
Answer
D · "I'll take my enzyme capsules at bedtime."
7.Clinical nursing
Answer: C · Diabetic ketoacidosis
Why this is the answer
High glucose, ketones and acidosis with Kussmaul breathing indicate DKA. It is treated with fluids, insulin and close potassium monitoring.
Answer
C · Diabetic ketoacidosis
8.Clinical nursing
Answer: A · Air embolism
Why this is the answer
Air embolism can occur when a central line is open to air. Clamp the line, lay the patient on the left side with head down if possible, give high-flow oxygen and call for help.
Answer
A · Air embolism
9.Lab values & electrolytes
Answer: C · Put seizure precautions in place and monitor neurological status
Why this is the answer
Hyponatremia can cause cerebral edema and seizures. The nurse monitors neurological status, takes seizure precautions and reports the result. Extra water and thiazides can lower the sodium further.Checked against:Low blood sodium · MedlinePlus (NIH) (2025)
Answer
C · Put seizure precautions in place and monitor neurological status
10.Lab values & electrolytes
Answer: D · Knee reflexes, respiratory rate and urine output
Why this is the answer
Loss of the knee reflex is an early warning sign of magnesium toxicity and appears before slowed breathing. Magnesium is cleared by the kidneys, so falling urine output increases the risk. IV calcium gluconate counteracts magnesium toxicity.Checked against:Magnesium Toxicity · StatPearls (NCBI Bookshelf) (2026); Magnesium Toxicity · StatPearls (NCBI Bookshelf)
Answer
D · Knee reflexes, respiratory rate and urine output
11.Arterial blood gas interpretation
Answer: HCO₃⁻ = 24.9 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
|49 − 40| = 9 mmHg → 0.9 × 10 mmHg
Expected HCO₃⁻
HCO₃⁻ = 24 + 1·0.9 = 24.9 mmol/L
Answer
HCO₃⁻ = 24.9 mmol/L
12.Arterial blood gas interpretation
Answer: AGc = 18.25 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.
Anion gap
AG = 138 − (102 + 20) = 16
Correction for albumin
16 + 0.25·(40 − 31) = 18.25 mmol/L
Answer
AGc = 18.25 mmol/L
Above about 12 after correction: a high anion gap.
13.ECG rhythm strip interpretation
Answer: supraventricular tachycardia (SVT)
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. Narrow-complex tachycardia and pauses: supraventricular tachycardia (SVT) is a regular tachycardia at about 150–250/min with narrow QRS complexes; the P waves are usually not visible because they are hidden in the QRS complex or the T wave. Sinus tachycardia in an adult at rest is usually below about 150/min and has a visible P wave before every QRS; atrial flutter with 2:1 conduction often runs at about 150/min and shows sawtooth waves. In sinus arrest the sinus node stops firing for a moment: a pause with no P wave and no QRS whose length is not a whole number of P–P cycles (a pause of exactly two or three cycles points to sinus exit block instead).
Five steps
1. Rate: R–R = 10 small boxes, 1500 ÷ 10 ≈ 150 per minute.
2. Rhythm: regular, every R–R is 0.40 s.
3. P waves: none visible; at this rate they are hidden in the QRS complexes or the T waves.
4. PR interval: not measurable.
5. QRS: 0.06 s, narrow (below 0.12 s), so the rhythm starts above the ventricles.
Interpretation
supraventricular tachycardia (SVT)
Answer
supraventricular tachycardia (SVT)
14.ECG rhythm strip interpretation
Answer: ventricular fibrillation
Ventricular rhythms: ventricular tachycardia is a run of three or more wide (0.12 s or more) complexes in a row at more than 100/min, usually 150–250/min, regular, without related P waves. Ventricular fibrillation is a chaotic, irregular waveform with no identifiable P waves, QRS complexes or T waves and no countable rate. Asystole is an almost flat line with no ventricular activity; a flat line is always confirmed by checking the patient, the leads and the gain and a second lead. In resuscitation guidelines VF and pulseless VT are the shockable rhythms and asystole is not.
Five steps
1. Rate: no countable ventricular rate.
2. Rhythm: chaotic, no repeating pattern.
3. P waves: none identifiable.
4. PR interval: not measurable.
5. QRS: no QRS complexes.
Interpretation
ventricular fibrillation
Answer
ventricular fibrillation
In resuscitation guidelines VF and pulseless VT are the shockable rhythms. This is identification practice only.
15.Prioritization & delegation
Answer: B · Stop the infusion and remove the cannula
Why this is the answer
A cool, pale, swollen site suggests infiltration. The nurse stops the infusion, removes the cannula, elevates the limb and restarts the IV at another site as needed.
Answer
B · Stop the infusion and remove the cannula
16.Prioritization & delegation
Answer: C · The tight burned skin is restricting chest movement, so an escharotomy may be needed
Why this is the answer
Circumferential full-thickness burns form stiff eschar that can stop the chest expanding. An escharotomy, cutting through the eschar, may be needed urgently to allow breathing.
Answer
C · The tight burned skin is restricting chest movement, so an escharotomy may be needed