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 practice patient is assessed with the Braden scale: sensory perception: no impairment; moisture: constantly moist; activity: chairfast; mobility: very limited; nutrition: very poor; friction and shear: no apparent problem. Find the Braden total B.
6–23
B =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). The team aims for a mean arterial pressure of at least 60 mmHg. A patient’s systolic pressure is 94 mmHg. Using MAP = (SBP + 2·DBP)/3, what is the lowest diastolic pressure DBP that still gives a MAP of 60 mmHg?
MAP 60 mmHgSBP 94 mmHg
DBP = mmHg
3.Arterial blood gas interpretationMedium
Practice values: Na⁺ 128 mmol/L, glucose 18.3 mmol/L and urea 18.2 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 128 mmol/Lglucose 18.3 mmol/Lurea 18.2 mmol/L
Osm = mOsm/kg
4.Arterial blood gas interpretationHard
Practice values: Na⁺ 134, Cl⁻ 96 and HCO₃⁻ 13 mmol/L. Calculate the delta ratio (AG − 12)/(24 − HCO₃⁻), using AG = Na⁺ − (Cl⁻ + HCO₃⁻). Give two decimals.
Na⁺ 134 mmol/LCl⁻ 96 mmol/LHCO₃⁻ 13 mmol/L
delta ratio =
5.Nursing fundamentalsMedium
On the first step of the WHO analgesic ladder, which drugs are used?
AGeneral anaesthetic drugs given in low doses
BNon-opioids such as paracetamol (acetaminophen) or an NSAID
CStrong opioids such as morphine
DWeak opioids only, such as codeine
6.Nursing fundamentalsHard
A pressure ulcer shows full-thickness tissue loss with exposed bone. How is it classified?
ACategory 2
BSuspected deep tissue injury
CCategory 3
DCategory 4
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A patient’s temperature is 97.2 °F. Convert it to degrees Celsius T with °C = (°F − 32) × 5/9. Round to one decimal place.
97.2 °F
T = °C
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An infusion starts at 21:45 and finishes at 02:05 the next morning (24-hour clock). How many hours t did it run? Give the answer in hours as a decimal, rounded to two decimal places.
21:4502:05
t = h
3Solutions
1.Clinical assessment scores
Answer: B = 13
Braden scale: six subscales for pressure-injury risk. Sensory perception, moisture, activity, mobility and nutrition score 1 to 4, from the worst level (1) to no problem (4); friction and shear scores 1 to 3. The total runs from 6 to 23, and a lower total means a higher risk. Common bands: 19–23 not at risk, 15–18 mild risk, 13–14 moderate risk, 10–12 high risk and 9 or below very high risk.
Score each subscale
sensory perception: no impairment → 4
moisture: constantly moist → 1
activity: chairfast → 2
mobility: very limited → 2
nutrition: very poor → 1
friction and shear: no apparent problem → 3
Add
Braden total = 4 + 1 + 2 + 2 + 1 + 3 = 13
Answer
B = 13
2.Clinical assessment scores
Answer: DBP = 43 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 = (3·60 − 94)/2 = 86/2 = 43 mmHg
Answer
DBP = 43 mmHg
3.Arterial blood gas interpretation
Answer: Osm = 293 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 = 2·128 + 18.3 + 18.2 = 292.5 ≈ 293 mOsm/kg
Answer
Osm = 293 mOsm/kg
4.Arterial blood gas interpretation
Answer: delta ratio = 1.182
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 = 134 − (96 + 13) = 25
Delta ratio
(25 − 12)/(24 − 13) = 13/11 = 1.182
Answer
delta ratio = 1.182
Between 1 and 2: a pure high anion gap acidosis.
5.Nursing fundamentals
Answer: B · Non-opioids such as paracetamol (acetaminophen) or an NSAID
Why this is the answer
The WHO ladder starts with non-opioids, adds a weak opioid for moderate pain and a strong opioid for severe pain, with adjuvants at any step. It is still widely taught, although current WHO guidance stresses individual assessment over a strict step-by-step approach.
Answer
B · Non-opioids such as paracetamol (acetaminophen) or an NSAID
6.Nursing fundamentals
Answer: D · Category 4
Why this is the answer
Category 4 (Stage 4 in the US NPIAP system) involves full-thickness tissue loss with exposed bone, tendon or muscle. It carries a high risk of osteomyelitis and needs specialist input.
Answer
D · Category 4
7.Nursing math & unit conversions
Answer: T = 36.2 °C
Temperature: °C = (°F − 32) × 5/9 and °F = °C × 9/5 + 32. Subtract 32 before you multiply when going from °F, and add 32 after you multiply when going from °C. A quick check: 37 °C is 98.6 °F, and every 1 °C is 1.8 °F.
Subtract 32
97.2 − 32 = 65.2
Multiply by 5/9
T = 65.2·5/9 = 36.22 ≈ 36.2 °C
Answer
T = 36.2 °C
8.Nursing math & unit conversions
Answer: t = 4.33 h
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.