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.
Nursing math & unit conversions
Metric steps
1 kg = 1000 g, 1 g = 1000 mg, 1 mg = 1000 mcg, 1 L = 1000 mL
Weight and length
1 kg = 2.2 lb, 1 lb = 16 oz, 1 in = 2.54 cm, 1 ft = 12 in
Household measures
1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 8 fl oz = 240 mL
Write the given quantity with its unit and the unit you want.
Pick the equivalent: 1000 between kg, g, mg and mcg or L and mL; 1 kg = 2.2 lb; 1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 240 mL.
Write it as a fraction so that the unwanted unit cancels; for a rate, use one fraction per unit that changes.
Check the direction: a smaller unit gives a bigger number.
Round only the final answer, to the precision the question names.
2Practice problems
1.Clinical assessment scoresMedium
Practice exercise (made-up values, not clinical guidance). A patient has a pulse of 117/min and a blood pressure of 73/44 mmHg. Find the shock index SI = HR/SBP. Round to two decimal places.
HR 117/minBP 73/44 mmHg
SI =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). The team aims for a mean arterial pressure of at least 70 mmHg. A patient’s systolic pressure is 116 mmHg. Using MAP = (SBP + 2·DBP)/3, what is the lowest diastolic pressure DBP that still gives a MAP of 70 mmHg?
MAP 70 mmHgSBP 116 mmHg
DBP = mmHg
3.Arterial blood gas interpretationMedium
Practice values: Na⁺ 150 mmol/L, glucose 16.8 mmol/L and urea 10.4 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 150 mmol/Lglucose 16.8 mmol/Lurea 10.4 mmol/L
Osm = mOsm/kg
4.Arterial blood gas interpretationHard
A practice gas shows a metabolic acidosis: pH 7.22, PaCO₂ 20 mmHg (2.7 kPa), HCO₃⁻ 8 mmol/L. Compare the measured PaCO₂ with Winter’s formula. Click your interpretation.
pH 7.22PaCO₂ 20 mmHg (2.7 kPa)HCO₃⁻ 8 mmol/L
1appropriate compensation
2added respiratory acidosis
3added respiratory alkalosis
5.Nursing fundamentalsMedium
A patient asks to see their own health records. What is correct in the UK?
AOnly doctors are allowed to see health records
BPatients have a legal right to request access to their records
CPatients can only see their records once they have been discharged
DPatients can see their records only with a court order
6.Nursing fundamentalsHard
Which postoperative finding should be reported most urgently?
APain score of 4/10 at the wound site when moving
BRespiratory rate 8/min and difficult to rouse
CTemperature 37.4 °C on the first day
DUrine output of 50 mL in the last hour
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A dose calculation for a small injection gives 0.62706 mL. The rule in this exercise is that volumes below 1 mL are rounded to the nearest hundredth of a mL. What value x do you record?
0.62706 mL
x = mL
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). During a shift a patient takes 2 cups of tea, 6 fl oz of juice, 3 tbsp of liquid supplement, ½ tsp of cough syrup. Using the equivalents given, find the total oral intake V in mL.
1 cup = 8 fl oz = 240 mL1 fl oz = 30 mL1 tbsp = 15 mL1 tsp = 5 mL
V = mL
3Solutions
1.Clinical assessment scores
Answer: SI = 1.6
Blood pressure values: pulse pressure PP = SBP − DBP. Mean arterial pressure MAP ≈ (SBP + 2·DBP)/3 = DBP + PP/3, an estimate based on the heart spending about two thirds of each beat in diastole at a normal heart rate (less accurate when the heart rate is fast); a MAP of at least about 65 mmHg is a common target for organ perfusion. The shock index SI = heart rate/SBP is normally about 0.5–0.7; a value above about 1 is a warning sign of shock.
Shock index
SI = 117/73 = 1.603 ≈ 1.6
Answer
SI = 1.6
1 or more: a warning sign of shock in this practice case.
2.Clinical assessment scores
Answer: DBP = 47 mmHg
Blood pressure values: pulse pressure PP = SBP − DBP. Mean arterial pressure MAP ≈ (SBP + 2·DBP)/3 = DBP + PP/3, an estimate based on the heart spending about two thirds of each beat in diastole at a normal heart rate (less accurate when the heart rate is fast); a MAP of at least about 65 mmHg is a common target for organ perfusion. The shock index SI = heart rate/SBP is normally about 0.5–0.7; a value above about 1 is a warning sign of shock.
Rearrange
DBP = (3·MAP − SBP)/2
Substitute
DBP = (3·70 − 116)/2 = 94/2 = 47 mmHg
Answer
DBP = 47 mmHg
3.Arterial blood gas interpretation
Answer: Osm = 327 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 = 2·150 + 16.8 + 10.4 = 327.2 ≈ 327 mOsm/kg
Answer
Osm = 327 mOsm/kg
4.Arterial blood gas interpretation
Answer: appropriate compensation
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
1.5·8 + 8 = 20 → 18–22 mmHg
Compare
measured: 20 mmHg → appropriate compensation
Answer
appropriate compensation
5.Nursing fundamentals
Answer: B · Patients have a legal right to request access to their records
Why this is the answer
Under data protection law, patients can request access to their health records. The nurse explains the local process for making a request.
Answer
B · Patients have a legal right to request access to their records
6.Nursing fundamentals
Answer: B · Respiratory rate 8/min and difficult to rouse
Why this is the answer
A low respiratory rate with reduced consciousness may mean opioid toxicity or deterioration and threatens the airway. The other findings are common after surgery and can be managed routinely.
Answer
B · Respiratory rate 8/min and difficult to rouse
7.Nursing math & unit conversions
Answer: x = 0.63 mL
Rounding: look at the digit just after the place you round to: 5 or more rounds up, 4 or less leaves the digit as it is. Round only the final answer, never the steps. Typical exam rules: volumes of 1 mL or more to the nearest tenth, volumes below 1 mL to the nearest hundredth, drip rates to whole drops and weights to one decimal place; always follow the rule the question states.
Digit in the hundredths place
0.62706 → 2
Only the next digit decides
0.62706 → 7
7 is 5 or more, so round 2 up.
The digits after it (06) are ignored: round once, never step by step.
Round
x = 0.63 mL
Answer
x = 0.63 mL
8.Nursing math & unit conversions
Answer: V = 707.5 mL
Household measures and weight: nursing exams use rounded equivalents: 1 teaspoon (tsp) = 5 mL, 1 tablespoon (tbsp) = 15 mL = 3 tsp, 1 fluid ounce (fl oz) = 30 mL = 2 tbsp, and 1 cup = 8 fl oz = 240 mL. For weight, 1 kg = 2.2 lb and 1 lb = 16 oz; for length, 1 inch = 2.54 cm. Set the conversion up so that the unit you do not want cancels out.