Nursing Fundamentals and Clinical Practice: cram pack

Arterial blood gas interpretation

Normal ranges

pH 7.35–7.45, PaCO₂ 35–45 mmHg (4.7–6.0 kPa), HCO₃⁻ 22–26 mmol/L

ROME

Respiratory: PaCO₂ opposite to pH; Metabolic: HCO₃⁻ equal to pH

Winter’s formula

PaCO₂ = 1.5·HCO₃⁻ + 8 ± 2

Metabolic alkalosis

PaCO₂ ≈ 0.7·HCO₃⁻ + 21

Anion gap

AG = Na⁺ − (Cl⁻ + HCO₃⁻) ≈ 8–12

Albumin-corrected gap

AG + 2.5·(4.0 − alb g/dL) = AG + 0.25·(40 − alb g/L)

Delta ratio

(AG − 12)/(24 − HCO₃⁻)

P/F ratio

PaO₂/FiO₂

Alveolar gas equation

PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8

Serum osmolality

2·Na⁺ + glucose + urea (2·Na⁺ + glucose/18 + BUN/2.8)

Method

1. Read the pH: below 7.35 is acidosis, above 7.45 alkalosis.
2. Find the value that explains it: PaCO₂ moving opposite to the pH is respiratory, HCO₃⁻ moving with the pH is metabolic.
3. 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.
4. In a metabolic acidosis, compare PaCO₂ with Winter’s formula, 1.5·HCO₃⁻ + 8 ± 2, and calculate the anion gap Na⁺ − (Cl⁻ + HCO₃⁻).
5. Check a high anion gap with the delta ratio and, when albumin is low, with the corrected gap.

Clinical assessment scores

Glasgow Coma Scale

GCS = E (1–4) + V (1–5) + M (1–6) = 3–15

APGAR

5 signs × 0–2 = 0–10; 7–10 reassuring, 4–6 moderately abnormal, 0–3 low

Braden scale

5 × (1–4) + 1 × (1–3) = 6–23; ≤ 18 at risk

Morse fall scale

falls 25, diagnosis 15, aid 15/30, IV 20, gait 10/20, mental status 15

NEWS2 risk

0–4 low; single 3 low–medium; 5–6 medium; ≥ 7 high

Mean arterial pressure

MAP = (SBP + 2·DBP)/3 = DBP + PP/3

Pulse pressure and shock index

PP = SBP − DBP, SI = HR/SBP

Body mass index

BMI = kg/m² = 703·lb/in²

Method

1. Find the score sheet that the question uses and its range (GCS 3–15, APGAR 0–10, Braden 6–23, Morse 0–125).
2. Score every item separately, matching the description to its level.
3. Add the item scores and check that the total lies inside the range.
4. Apply the cut-offs: for NEWS2 also look for any single parameter scoring 3.
5. For derived values use MAP = (SBP + 2·DBP)/3, PP = SBP − DBP, SI = HR/SBP and BMI = kg/m².

Enteral & parenteral nutrition calculations

Daily volume

mL = kcal / (kcal/mL)

Continuous feed

mL/h = daily volume / hours of feeding

Bolus feed

mL per feed = daily volume / number of feeds

Energy and protein delivered

kcal = mL × kcal/mL; g = L × g/L

Free water

mL = formula volume × water fraction

Ideal body weight (Devine)

men 50 + 2.3 × (in − 60); women 45.5 + 2.3 × (in − 60); 1 in = 2.54 cm

Body mass index

BMI = kg/m²

Parenteral nutrition

dextrose 3.4 kcal/g, amino acids 4 kcal/g, lipid 20% 2.0 kcal/mL, 10% 1.1 kcal/mL

Nitrogen

g N = g protein / 6.25

Glucose infusion rate

GIR = mg/(kg·min) = % × mL/h / (6 × kg)

Method

1. Write down what is asked: a pump rate, a volume, kilocalories, grams of protein or water.
2. Turn energy into volume with mL = kcal/(kcal/mL), and volume into protein with litres × g/L.
3. Divide by the hours the feed actually runs for a rate, or by the number of feeds for a bolus.
4. For needs, multiply kcal/kg or g/kg by the weight the rule names; find the ideal body weight with Devine: 50 or 45.5 + 2.3 × (inches − 60).
5. For PN, find grams as % × mL/100, then use 3.4 kcal/g for dextrose, 4 kcal/g for amino acids and the stated kcal/mL for lipid.

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

1. 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.
2. Rhythm: compare the R–R intervals. Equal is regular; a repeating pattern is regularly irregular; no pattern at all is irregularly irregular.
3. 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.
4. 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.
5. 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

1. Ask what will harm the patient soonest if nothing is done.
2. Apply ABC (C-A-B in cardiac arrest), then Maslow: physiological needs before safety, safety before psychological needs.
3. Compare the options: acute before chronic, unstable before stable, unexpected before expected, systemic before local, and check each finding against the patient’s baseline.
4. Assess before you act unless it is an emergency; then choose the step the others depend on.
5. For delegation, check the five rights: task, circumstance, person, directions and supervision. Assessment, teaching and evaluation stay with the RN.

Infection control & patient safety

Method

1. Start with standard precautions for every patient: hand hygiene, PPE for the expected exposure, safe sharps.
2. Add precautions by route: contact (gown, gloves), droplet (surgical mask), airborne (N95, negative-pressure room).
3. Keep sterile items sterile: if in doubt, it is not sterile; replace, never wipe.
4. Prevent harm in the environment: fall measures, restraints only as a last resort, RACE and PASS for fire.
5. Check the rights of medication administration, two identifiers and extra safeguards for high-alert drugs; report errors and near misses.

Lab values & electrolytes

Method

1. Compare the value with the laboratory’s own reference range, then with the patient’s baseline and trend.
2. Check the sample: hemolysis, a delay, or blood drawn near an IV can give false results.
3. Link the value to its typical signs and to the drugs and conditions that cause it.
4. Look for interactions: low potassium or magnesium increases digoxin toxicity; dehydration raises lithium.
5. Act on the patient: assess, hold a drug if the level is unsafe, read back critical values and inform the prescriber.