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). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 28/min, SpO₂ 95% on room air, blood pressure 106/64 mmHg, pulse 126/min, alert, temperature 36.7 °C. What is the NEWS2 total score?
RR 28SpO₂ 95%airSBP 106HR 126AT 36.7 °C
NEWS2 =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 21/min, SpO₂ 99% on room air, blood pressure 222/134 mmHg, pulse 120/min, alert, temperature 39.6 °C. Which clinical risk group does the patient fall into? Click it.
RR 21SpO₂ 99%airSBP 222HR 120AT 39.6 °C
1low
2low–medium
3medium
4high
3.Arterial blood gas interpretationMedium
A practice arterial blood gas shows pH 7.62, PaCO₂ 24 mmHg (3.2 kPa) and HCO₃⁻ 24 mmol/L. The primary disorder is respiratory alkalosis. How far is it compensated? Click your answer.
pH 7.62PaCO₂ 24 mmHg (3.2 kPa)HCO₃⁻ 24 mmol/L
1uncompensated
2partially compensated
3fully compensated
4.Arterial blood gas interpretationHard
A practice gas shows a metabolic alkalosis with HCO₃⁻ 45 mmol/L. Use expected PaCO₂ = 0.7·HCO₃⁻ + 21 to find the expected PaCO₂.
HCO₃⁻ 45 mmol/L
PaCO₂ = mmHg
5.Nursing fundamentalsMedium
Why should insulin injection sites be rotated?
ABecause each site can only be used once
BTo make the insulin work more quickly with each injection
CTo stop the patient getting used to the needle
DTo prevent lumpy fatty swelling that affects absorption
6.Nursing fundamentalsHard
In a patient with sepsis, what does a raised blood lactate suggest?
AThe infection has been cured
BThe patient has eaten recently
CThe tissues are not getting enough oxygen
DThe kidneys are making too much urine
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A dose is charted at 3:10 PM. Which entry is the same time on the 24-hour clock? Click it.
3:10 PM
116:10
203:10
314:10
415:10
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An infusion delivers 5 mcg/min. Express this dose rate D in mg/h.
5 mcg/min1 h = 60 min1 mg = 1000 mcg
D = mg/h
3Solutions
1.Clinical assessment scores
Answer: NEWS2 = 7
NEWS2 (National Early Warning Score 2, Royal College of Physicians 2017): score each of the seven parameters with the chart (respiration rate, SpO₂ on scale 1, air or supplemental oxygen, systolic blood pressure, pulse, consciousness on the ACVPU scale and temperature) and add the scores. Clinical risk: 0–4 low; a score of 3 in any single parameter low–medium; 5–6 medium; 7 or more high. A total of 5 or more needs an urgent response.
Score each parameter
RR 28/min → 3
SpO₂ 95% → 1
on air → 0
SBP 106 mmHg → 1
HR 126/min → 2
alert (A) → 0
T 36.7 °C → 0
Add
NEWS2 = 3 + 1 + 0 + 1 + 2 + 0 + 0 = 7
Answer
NEWS2 = 7
2.Clinical assessment scores
Answer: high
NEWS2 (National Early Warning Score 2, Royal College of Physicians 2017): score each of the seven parameters with the chart (respiration rate, SpO₂ on scale 1, air or supplemental oxygen, systolic blood pressure, pulse, consciousness on the ACVPU scale and temperature) and add the scores. Clinical risk: 0–4 low; a score of 3 in any single parameter low–medium; 5–6 medium; 7 or more high. A total of 5 or more needs an urgent response.
Score each parameter
RR 21/min → 2
SpO₂ 99% → 0
on air → 0
SBP 222 mmHg → 3
HR 120/min → 2
alert (A) → 0
T 39.6 °C → 2
Total and red scores
NEWS2 = 2 + 0 + 0 + 3 + 2 + 0 + 2 = 9
At least one parameter scores 3.
Risk group
high
Answer
high
A total of 5 or more calls for an urgent clinical response.
3.Arterial blood gas interpretation
Answer: uncompensated
Reading a blood gas (ROME): first the pH: below 7.35 is acidaemia, above 7.45 alkalaemia. Then find the value that explains it. PaCO₂ (normal 35–45 mmHg, 4.7–6.0 kPa) is the respiratory part and moves Opposite to the pH in a respiratory disorder; HCO₃⁻ (normal 22–26 mmol/L) is the metabolic part and moves in the same direction as the pH (Respiratory Opposite, Metabolic Equal). The other value shows the compensation: normal means uncompensated; abnormal in the direction that pulls the pH back while the pH is still abnormal means partially compensated; a normal pH with both values abnormal means fully compensated. Ranges differ slightly between laboratories; these are practice values.
ROME, value by value
pH 7.62: alkalaemia (above 7.45)
PaCO₂ 24 mmHg: low (35–45)
HCO₃⁻ 24 mmol/L: normal (22–26)
Compensation
uncompensated
Answer
uncompensated
4.Arterial blood gas interpretation
Answer: PaCO₂ = 52.5 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
0.7·45 + 21 = 52.5 mmHg
Answer
PaCO₂ = 52.5 mmHg
The rise has a limit: PaCO₂ rarely goes above about 55 mmHg from compensation alone.
5.Nursing fundamentals
Answer: D · To prevent lumpy fatty swelling that affects absorption
Why this is the answer
Injecting in the same place causes lipohypertrophy, which makes absorption unpredictable. Patients rotate within an area and check sites for lumps.
Answer
D · To prevent lumpy fatty swelling that affects absorption
6.Nursing fundamentals
Answer: C · The tissues are not getting enough oxygen
Why this is the answer
When tissues are poorly perfused they switch to anaerobic metabolism and produce lactate. A raised lactate in sepsis signals higher risk and the need for urgent treatment.
Answer
C · The tissues are not getting enough oxygen
7.Nursing math & unit conversions
Answer: 15:10
24-hour clock: from 1 PM onwards add 12 to the hour (3:45 PM = 15:45). Midnight to 12:59 AM is 00:00–00:59, and 12:00–12:59 PM stays 12:00–12:59. Going back, subtract 12 from hours 13–23 and add PM; hours 00 become 12 AM. Count time across midnight in two parts: up to 24:00 (00:00), then from 00:00 on.
Convert the hour
3 PM → 3 + 12 = 15
Answer
15:10
Answer
15:10
8.Nursing math & unit conversions
Answer: D = 0.3 mg/h
Dimensional analysis: write the given quantity, then multiply by conversion factors written as fractions (for example 60 min/1 h or 1 mg/1000 mcg) so that each unwanted unit appears once on top and once underneath and cancels. When only the wanted unit is left, calculate. Use the equivalents the question gives and round only the final answer.