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
How is the jugular venous pressure usually assessed?
APatient standing with the neck flexed forward
BPatient sitting upright with the arms raised above the head
CPatient lying completely flat with the head turned to the right
DPatient reclined at 45° with the head turned slightly to the left
2.Med-surg: cardiovascular & respiratoryHard
A patient with pneumonia on high-flow nasal oxygen at 50 L/min with FiO₂ 0.6 has SpO₂ 90%, RR 34/min and is using accessory muscles. What is the most appropriate action?
AEscalate urgently to critical care for review of respiratory support
BContinue the same support and recheck in four hours
CLay the patient flat so they can rest the breathing muscles
DChange to a nasal cannula at 4 L/min to reduce nasal dryness
3.Med-surg: neuro, endocrine & renalMedium
Which Glasgow Coma Scale score usually suggests that a patient may not be able to protect their own airway?
A11 or above
B8 or below
C15
D13 or below
4.Med-surg: neuro, endocrine & renalHard
An older patient with type 2 diabetes has glucose 48 mmol/L, osmolality 365 mOsm/kg, no significant ketones and confusion. What is the first priority?
AA large IV insulin bolus to bring glucose to normal within an hour
BOral glucose to prevent hypoglycaemia during treatment
CCareful IV fluids with close checks of osmolality, sodium and glucose
DStrict fluid restriction to avoid cerebral oedema
5.Med-surg: GI, perioperative & oncologyMedium
Which statement about fatigue during radiotherapy is correct?
AIt often builds during the course and can last for weeks
BIt is caused by the patient becoming radioactive
CIt occurs only after the first session and then disappears completely
DIt means the radiotherapy has failed
6.Med-surg: GI, perioperative & oncologyHard
Which patient is at highest risk of respiratory depression from a postoperative opioid PCA?
AA patient whose pain score is 8/10 and who is wide awake and alert
BA patient with no other medical problems who receives paracetamol
CAn opioid-naive older patient with sleep apnoea who also takes a sedative
DA young patient who has used opioids regularly for many months
7.Clinical nursingMedium
Within which time window is IV thrombolysis generally given for acute ischaemic stroke?
AWithin 48 hours of the onset of symptoms
BWithin 4.5 hours of symptom onset
CAt any time within a week
DOnly after 24 hours
8.Clinical nursingHard
Which action is correct when caring for a chest drain with an underwater seal?
AKeep the drainage bottle below the level of the chest
BRemove the water from the bottle to prevent spills
CLift the bottle above the patient to empty it
DClamp the tube routinely during every transfer or bed move
9.Lab values & electrolytesMedium
A patient’s white cell count is 16 × 10³/µL with a high proportion of immature neutrophils (bands). What does this most likely indicate?
AA normal result
BAn acute bacterial infection
CA chronic viral illness only
DIron-deficiency anemia
10.Lab values & electrolytesHard
During surgery under general anesthesia, a patient develops a rising end-tidal CO2, muscle rigidity and tachycardia, then a high potassium and a rising temperature. Which condition is most likely?
AAcute hemolytic transfusion reaction
BHypovolemic shock
CMalignant hyperthermia
DHypoglycemia from fasting
11.Arterial blood gas interpretationMedium
Practice values: Na⁺ 145 mmol/L, glucose 9.8 mmol/L and urea 6.8 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 145 mmol/Lglucose 9.8 mmol/Lurea 6.8 mmol/L
Osm = mOsm/kg
12.Arterial blood gas interpretationHard
At sea level, a practice gas taken on 35% oxygen shows PaO₂ 72 mmHg (9.6 kPa) and PaCO₂ 57 mmHg (7.6 kPa). Use PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 to find the A–a gradient.
Measure the QT interval on this lead II strip, in seconds.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
QT = s
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
1atrial fibrillation
2ventricular tachycardia
3ventricular fibrillation
4asystole
15.Prioritization & delegationMedium
During an IV antibiotic infusion, a patient develops hives, wheezing and a hoarse voice. What does the nurse do first?
ADocument the reaction in the chart
BStop the infusion
CSlow the infusion to half the rate
DGive oral diphenhydramine
16.Prioritization & delegationHard
A child who had a tonsillectomy this morning is swallowing again and again while asleep. What should the nurse suspect?
ABleeding from the operation site
BA sore throat from the breathing tube
CNormal swallowing during sleep
DHunger after fasting for surgery
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: D · Patient reclined at 45° with the head turned slightly to the left
Why this is the answer
With the patient at 45°, the vertical height of the pulsation in the right internal jugular vein above the sternal angle is estimated. A height above about 3–4 cm suggests raised right-sided pressure, as in right heart failure or fluid overload.
Answer
D · Patient reclined at 45° with the head turned slightly to the left
2.Med-surg: cardiovascular & respiratory
Answer: A · Escalate urgently to critical care for review of respiratory support
Why this is the answer
High oxygen requirements with tachypnoea and increased work of breathing despite high-flow oxygen indicate worsening respiratory failure. Early critical care review is needed for escalation such as CPAP, NIV or intubation. Reducing support or waiting risks a respiratory arrest.
Answer
A · Escalate urgently to critical care for review of respiratory support
3.Med-surg: neuro, endocrine & renal
Answer: B · 8 or below
Why this is the answer
A GCS of 8 or less usually indicates coma and a risk that the patient cannot maintain or protect the airway, so urgent senior and anaesthetic review is needed. The score ranges from 3 to 15, and the components (E, V, M) should be reported separately.
Answer
B · 8 or below
4.Med-surg: neuro, endocrine & renal
Answer: C · Careful IV fluids with close checks of osmolality, sodium and glucose
Why this is the answer
HHS is managed first with IV fluids, which alone often lower glucose. Rapid falls in osmolality risk cerebral oedema, so it is lowered gradually. Insulin is added at a low rate if ketones are present or glucose stops falling with fluids. VTE prophylaxis is important because of the high clot risk.
Answer
C · Careful IV fluids with close checks of osmolality, sodium and glucose
5.Med-surg: GI, perioperative & oncology
Answer: A · It often builds during the course and can last for weeks
Why this is the answer
Radiotherapy fatigue usually increases as treatment continues and may persist for weeks or months afterwards. Pacing, light exercise and good sleep and nutrition help.
Answer
A · It often builds during the course and can last for weeks
6.Med-surg: GI, perioperative & oncology
Answer: C · An opioid-naive older patient with sleep apnoea who also takes a sedative
Why this is the answer
Risk factors include opioid-naive status, older age, obstructive sleep apnoea, obesity, renal or hepatic impairment, lung disease and concurrent sedatives (benzodiazepines, gabapentinoids). These patients need closer monitoring of sedation, respiratory rate and saturation, sometimes continuously.
Answer
C · An opioid-naive older patient with sleep apnoea who also takes a sedative
7.Clinical nursing
Answer: B · Within 4.5 hours of symptom onset
Why this is the answer
Thrombolysis with alteplase is generally given within 4.5 hours of onset after a scan excludes haemorrhage. Knowing when the patient was last seen well is therefore essential.
Answer
B · Within 4.5 hours of symptom onset
8.Clinical nursing
Answer: A · Keep the drainage bottle below the level of the chest
Why this is the answer
The bottle stays below chest level so fluid and air cannot return to the pleural space. Routine clamping can cause a tension pneumothorax.
Answer
A · Keep the drainage bottle below the level of the chest
9.Lab values & electrolytes
Answer: B · An acute bacterial infection
Why this is the answer
A raised white count with more bands (a “left shift”) suggests that the marrow is responding to an acute bacterial infection or severe inflammation. The result is read together with the patient’s signs, such as fever.
Answer
B · An acute bacterial infection
10.Lab values & electrolytes
Answer: C · Malignant hyperthermia
Why this is the answer
Malignant hyperthermia is a genetic hypermetabolic reaction to volatile anesthetics or succinylcholine. Muscle cells release calcium, producing CO2, heat, rigidity, hyperkalemia and very high CK. It is treated with dantrolene and stopping the trigger.
Answer
C · Malignant hyperthermia
11.Arterial blood gas interpretation
Answer: Osm = 307 mOsm/kg
Derived values: calculated serum osmolality is 2·Na⁺ + glucose + urea with all values in mmol/L (2·Na⁺ + glucose/18 + BUN/2.8 with glucose and BUN in mg/dL); normal is about 275–295 mOsm/kg. The P/F ratio is PaO₂ divided by FiO₂ as a fraction. The alveolar oxygen pressure is PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 mmHg at sea level, and the A–a gradient is PAO₂ − PaO₂.
Calculated osmolality
Osm = 2·145 + 9.8 + 6.8 = 306.6 ≈ 307 mOsm/kg
Answer
Osm = 307 mOsm/kg
12.Arterial blood gas interpretation
Answer: A–a gradient = 106.3 mmHg
Derived values: calculated serum osmolality is 2·Na⁺ + glucose + urea with all values in mmol/L (2·Na⁺ + glucose/18 + BUN/2.8 with glucose and BUN in mg/dL); normal is about 275–295 mOsm/kg. The P/F ratio is PaO₂ divided by FiO₂ as a fraction. The alveolar oxygen pressure is PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 mmHg at sea level, and the A–a gradient is PAO₂ − PaO₂.
QT and QTc: the QT interval runs from the start of the QRS complex to the end of the T wave. It shortens as the heart rate rises, so it is corrected for rate with the R–R interval in seconds: Bazett QTc = QT/√RR and Fridericia QTc = QT/∛RR. Bazett is the formula most textbooks use; it over-corrects at fast rates, where Fridericia is preferred. Limits differ between references: a QTc above about 0.45 s in men or 0.46 s in women is usually called prolonged, and above 0.50 s markedly prolonged.
Measure
9.5 small boxes from the start of the QRS to the end of the T wave
Convert
QT = 9.5 × 0.04 s = 0.38 s
Answer
QT = 0.38 s
A rough rule: at normal rates the QT should be less than half the R–R interval (here R–R = 0.76 s).
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
Why this is the answer
Stopping the drug stops further exposure to the allergen. The nurse then calls for help and prepares epinephrine as prescribed for anaphylaxis. Slowing the infusion still gives more of the drug, and documentation comes later.
Answer
B · Stop the infusion
16.Prioritization & delegation
Answer: A · Bleeding from the operation site
Why this is the answer
Frequent swallowing after tonsillectomy is a classic sign of bleeding. The nurse checks the throat with a light, looks at vital signs and reports at once.