Induction — Critical Care

Use: Classify infection-related illness severity.

• Sepsis = identifiable source of infection + SIRS
• Severe sepsis = sepsis + organ dysfunction
• Septic shock = sepsis + cardiovascular collapse (requiring vasopressor support)

• Sepsis = life-threatening organ dysfunction caused by a dysregulated host response to infection
• Septic shock = vasopressors needed for MAP >65 mmHg + lactate >2.0 mmol/L despite adequate fluid resuscitation
• Abandoned: SIRS criteria for identifying sepsis; "severe sepsis" term

Use: Identify systemic inflammatory response. ≥2 criteria required.

• Temperature: ≥38°C or ≤36°C
• Heart rate: ≥90 bpm
• Respiratory rate: ≥20/min OR PaCO₂ ≤32 mmHg (or mechanical ventilation)
• WBC: ≥12,000/µL OR ≤4,000/µL OR ≥10% band forms

Use: Bedside screening tool to identify patients at risk of poor outcome from infection. Score ≥2 → start sepsis care pathway.

• Respiratory rate >22/min
• Altered mental status
• Systolic BP <100 mmHg

Limitation: Poor sensitivity — likely excludes its use as an early sepsis screening tool on its own.

Use: Predicts mortality risk for ICU patients based on lab and clinical data. A score of ≥2 is associated with a 10% or greater increase in mortality.

System	Parameter
Respiratory	PO₂ / FiO₂
Coagulation	Platelets / mm³
Liver	Bilirubin (mg/dl)
Cardiovascular	MAP and requirement for vasopressors (Dopamine, Epinephrine, Norepinephrine)
CNS	Glasgow Coma Scale
Renal	Creatinine (mg/dl) and Urine output (ml/d)

Use: Within the first hour of sepsis recognition. Key stat: 7.6% mortality increase for every hour delay in giving antibiotics.

• Supplemental Oxygen (high flow 15 L/min via non-rebreathe, target sats >94%)
• Establish IV access and start crystalloid (30 ml/kg)
• Insert a urinary catheter (hourly output monitoring)
• Draw a blood culture before starting antibiotics
• Administer empirical antibiotics
• Determine a lactate level

Ensure Hb >7 g/dl. Consider vasopressors if hypotensive after fluid resuscitation. Control the source of sepsis.

• Measure lactate level
• Obtain blood cultures prior to administration of antibiotics
• Administer broad-spectrum antibiotics
• Administer 30 ml/kg crystalloid for hypotension or lactate ≥4 mmol/L

• Apply vasopressors (for hypotension that does not respond to initial fluid resuscitation) to maintain MAP ≥65 mmHg
• In persistent hypotension despite volume resuscitation or initial lactate ≥4 mmol/L: measure CVP and central venous oxygen saturation (ScvO₂)
• Remeasure lactate if initial lactate was elevated

• CVP ≥8 mmHg
• MAP ≥65 mmHg
• Urine output ≥0.5 ml/kg/h
• ScvO₂ ≥70%
• Normalisation of lactate

Use: Supports clinical suspicion of necrotising soft tissue infection. Score ≥6 → high suspicion (PPV 92%, NPV 96%).

• Total WBC count
• Haemoglobin
• Sodium
• Glucose
• Serum creatinine
• C-reactive protein

• WBC ≥15,400/µL
• Serum sodium <135 mEq/L

Limitation: Failed to distinguish those with or without septic shock/death — should not be solely relied on for diagnosis.

Use: Classify severity of haemorrhagic shock by physiological parameters.

Param	Stage 1	Stage 2	Stage 3	Stage 4
% Blood loss	<15%	15–30%	30–40%	>40%
Cap refill	<2s	>2s	5s	>5s
Peripheries	Warm	Cool	Colder	Coldest
Heart rate	<100	>100	>120	>140
Blood pressure	Normal	Normal or narrow pulse pressure	Low	Very low
Resp rate	14–20	20–30	30–40	>35
Urine output (ml/hr)	>30	20–30	5–15	Negligible
Consciousness	Slightly anxious	Agitated	Confused/lethargic	Unresponsive

Compensation sequence: peripheral vasoconstriction → tachycardia → postural hypotension → recumbent hypotension

BP is the LAST parameter to drop — normal BP does NOT rule out significant blood loss.

Use: Activate massive transfusion protocol (e.g., dial 2222). Communication via SBAR. Nominate a coordinator/scribe.

• Replacement of entire blood volume in 24 hours
• Total transfusion >8–10 packed RBC units in 24 hours
• Replacement >50% blood volume in 3 hours
• Blood loss ≥150 ml/min
• Transfusion of ≥4 RBC units in 1 hour with ongoing haemorrhage
• Patient predicted to need ≥8 packed RBC units within 2 hours

Component ratio PRBC : FFP : Platelets = 1:1:1. Use permissive hypotension. Don't over-fluid (dilutes coagulation factors).

TXA (Tranexamic Acid): 1g bolus over 10 min then 1g infusion over 8h. Every 15-min delay decreases survival by 10%.

Use: Vertical approach for trauma resuscitation. For multiple trauma patients, use a horizontal approach (simultaneous, team-based task execution with delegated roles).

• A — Airway
• B — Breathing
• C — Circulation
• D — Disability (neurological assessment — GCS, pupils, lateralising signs, blood glucose)
• E — Exposure / Environment (remove clothing, logroll, prevent hypothermia, keep dignity, remove spine board ASAP)

Adjuncts: e-FAST, CXR, PXR, ± lateral cervical spine, ± whole-body CT, ± angiography/IR; analgesia (pharmacological, psychological, physical).

Planning round (STOP): all life-threats identified? all investigations done? analgesia given? what is the Plan? non-essential team disbanded? relatives informed?

Use: Concise medical history during trauma secondary survey, performed only when all immediately life-threatening conditions have been treated.

• A — Allergies
• M — Medications
• P — Past medical history
• L — Last meal
• E — Events leading to presentation

Use: Bailey & Love umbrella classification of shock into 5 categories, with causes of the main types

• Hypovolaemic
• Cardiogenic
• Obstructive
• Distributive
• Endocrine

• Cardiogenic - primary: infarction, arrhythmia, myocardial depression
• Cardiogenic - secondary (obstructive): cardiac tamponade, pulmonary embolism
• Hypovolaemic - loss of blood, plasma or extracellular fluid
• Distributive (low resistance) - vasogenic septic: endotoxin release + activation of cellular and humoral immune components
• Distributive (low resistance) - neurogenic: failure of sympathetic outflow (bradycardia)
• Distributive (low resistance) - anaphylactic: histamine release

Use: Estimate blood-loss volume and severity of haemorrhagic shock from clinical parameters (Class I-IV)

• Blood loss (mL): I up to 750; II 750-1500; III 1500-2000; IV >2000
• Blood loss (% blood volume): I up to 15; II 15-30; III 30-40; IV >40
• Pulse rate (per minute): I <100; II 100-120; III 120-140; IV >140
• Blood pressure: I normal; II normal; III decreased; IV decreased
• Pulse pressure (mmHg): I normal or increased; II decreased; III decreased; IV decreased
• Respiratory rate (per minute): I 14-20; II 20-30; III 30-40; IV >35
• Urine output (mL/hour): I >30; II 20-30; III 5-15; IV negligible
• CNS / mental status: I slightly anxious; II mildly anxious; III anxious, confused; IV confused, lethargic

Use: Bedside physiological deterioration score for surgical patients; a modification of the Early Warning Score

• Respiratory rate — e.g. <9 or ≥30
• Heart rate — <40 or ≥130
• Systolic BP — <70 or ≥200
• Temperature — <35 or ≥38.5
• AVPU (conscious level)

• Score ≥3 = needs urgent assessment
• Score ≥5 = likely critical care / HDU / ICU

Use: Clinical staging of shock progression

• Stage I — Compensation: skin + splanchnic vasoconstriction; signs minimal but recognisable
• Stage II — Decompensation: mechanisms fail to sustain tissue perfusion despite working at full capacity; urgent intervention needed
• Stage III — Essentially irreversible: prolonged shock → severe major-organ damage

Use: Compare cardiac index, SVR, venous capacitance, CVP/PCWP and SvO2 across shock types

• Cardiac index ↓
• SVR ↑
• Mixed venous O2 saturation (SvO2) low
• Base deficit high

• Cardiac index ↓
• SVR ↑
• Mixed venous O2 saturation low
• Base deficit high

• Cardiac index ↑ in hyperdynamic, ↓ in hypodynamic stage
• CVP/PCWP ↑ in hyperdynamic, ↓ in hypodynamic stage
• Mixed venous O2 saturation high
• Base deficit high

• Cardiac index ↑
• SVR ↓
• Venous capacitance unchanged
• CVP/PCWP ↓
• SvO2 ↓

Use: Classify timing of surgical intervention. NCEPOD = National Confidential Enquiry into Patient Outcome and Death.

Class	Definition & timing	Example
Immediate	Life/limb/organ saving; resuscitation simultaneous with surgery; within minutes	Rapid bleeding (trauma, aneurysm)
Urgent	Life/limb/organ threatening; within hours	Perforated bowel or less urgent bleeding
Expedited	Early surgery within a day or two	Large bowel obstruction, closed long bone fracture
Elective	Timing to suit patient and hospital	Joint replacement, unobstructed hernia repair, cataract

Use: American Society of Anesthesiologists physical status classification.

Class	Definition	Mortality
I	A normally healthy patient	0.05%
II	Mild systemic disease, not limiting activity	0.4%
III	Severe systemic disease that limits activity but not incapacitating	4.5%
IV	Incapacitating systemic disease, constant threat to life	25%
V	Moribund; not expected to survive 24h with or without operation	50%

Use: Risk stratification for surgical patients. POSSUM = Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity.

Composition: 12 physiological + 6 operative parameters.

• Age, cardiac, respiratory, ECG, systolic BP, pulse rate, haemoglobin, WBC, urea, sodium, potassium, GCS

• Operation type, number of procedures, operative blood loss, peritoneal contamination, malignancy status, CEPOD (timing)

Use: Airway assessment based on visible oropharyngeal structures.

Class	Visible structures
I	Uvula, fauces, soft palate, pillars visible
II	Uvula, soft palate, fauces visible
III	Base of uvula visible; soft palate visible
IV	Only hard palate visible

Three axes to align for intubation: oral, pharyngeal, laryngeal. Mr Douglas airway-difficulty factors: rheumatoid arthritis; cervical spine surgery; limited mouth opening.

Use: Predict difficulty of intubation. Score range 0–14 (higher = greater predicted difficulty).

Criterion	0 pts	1 pt	2 pts
Interincisor gap	>4 cm	4 cm	Cannot open mouth
Mallampati	Class I	Class II	Class III
Head/neck movement	>90°	=90°	<90°
Buck teeth	Can prognath or edentulous	Can approximate teeth only	Cannot approximate teeth
Thyromental distance	>6.5 cm	6.0–6.5 cm	<6.0 cm
Body weight	<90 kg	90–110 kg	>110 kg
Difficult intubation hx	None	Questionable	Definite

Use: Predict perioperative cardiac risk. Strong predictor.

• Walking endurance: Can the patient walk a mile?
• Stair tolerance: Can they climb a flight of stairs?
• Day-to-day function: Activities of daily living
• Severity & stability of comorbidities; current medications; previous surgery & anaesthetics (problems? family history?)

Intake type	Minimum fasting
Clear liquids (water, clear tea, black coffee, carbonated, fruit juice w/o pulp)	2 h
Breast milk	4 h
Non-human milk / light meal (infant formula; toast + clear liquids)	6 h
Regular or heavy meal (fried/fatty food, meat)	8 h

• Correct the correctable (low Hb, low potassium, high INR)
• Stabilise/improve medical co-morbidities
• Explain & sign informed consent
• Premedication (as appropriate)
• Cross match & save blood
• Antibiotic & DVT prophylaxis
• Check for LATEX allergy

Medication rule: Continue preoperative medications. Exceptions: insulin; oral hypoglycaemics; ACE inhibitors (sometimes); anti-coagulants.

Hip fracture timeframe: Standard time-to-fix = 48 hours. Risks of delay >48h: DVT, pneumonia. Specialist consultation: cardiologist & pulmonologist (goal: optimise).

Use: Grade systemic disease severity to determine peri-operative mortality/morbidity risk

• Grade I — healthy individual, no systemic disease — 0.05%
• Grade II — mild systemic disease not limiting activity — 0.4%; e.g. hypertensive on medication, controlled
• Grade III — severe systemic disease that limits activity but not incapacitating — 4.5%; e.g. same hypertensive but NOT controlled
• Grade IV — incapacitating systemic disease, constantly life-threatening — 25%
• Grade V — moribund, not expected to survive 24 hrs with or without surgery — 50%; e.g. big aortic aneurysm (~50% survival with surgery, ~50% mortality without)

Use: Point-based prediction of intubation difficulty (range 0–14)

• Interincisor gap — >4 cm / <4 cm / cannot open mouth
• Mallampati — Class I / Class II / Class III
• Head-neck movement — >90° / =90° / <90°
• Buck teeth — can prognath or edentulous / can approximate teeth only / cannot approximate teeth
• Thyromental distance — >6.5 cm / 6.0–6.5 cm / <6.0 cm
• Body weight — <90 kg / 90–110 kg / >110 kg
• History of difficult intubation — none / questionable / definite

• 0 = easy intubation
• 7 = medium
• 14 = difficult intubation

Use: Classify the intensity of care a patient requires, from ward-based to intensive care

• Level 0 — requires hospital admission; ward-based care
• Level 1 — additional monitoring, clinical input or advice (outreach); or recently discharged from ICU
• Level 2 — single-organ monitoring and support; advanced monitoring
• Level 3 — advanced organ support; or two or more organ system failures

Use: Bundled components used to prevent surgical site infection

• Antibiotic name
• Timing of administration
• Weight-based dose
• Re-dosing (for longer procedures)
• Discontinuation
• Antibiotic stewardship program and committee

• Ensure pre-operative skin antisepsis
• Develop standardized peri-operative skin antiseptic practices

• Standardized procedure to ensure normothermia
• Protocols to optimise glucose control
• Supplemental oxygen during pre-, intra- and post-operative periods
• Screen and/or decolonize selected patients with MRSA

• Adhere to established guidelines (e.g. HICPAC, AORN) to ensure basic aseptic techniques — traffic control, attire, audit
• Utilize a Safe Surgery Checklist to drive a culture of safety
• Establish a system where SSI data is analysed and shared

Use: Determine whether the primary acid-base problem is respiratory or metabolic.

• Respiratory Opposite — pH and CO₂ move in opposite directions
• Metabolic Equal — pH and CO₂ move in the same direction

Disorder	pH	CO₂	HCO₃
Respiratory acidosis	↓	↑	Normal
Respiratory alkalosis	↑	↓	Normal
Resp acidosis + metabolic compensation	↓ / ↔	↑	↑
Resp alkalosis + metabolic compensation	↑ / ↔	↓	↓

Compensation always goes in the same direction as the primary problem. CO₂ is an acid. Remember: ABG steps = Oxygenation → pH → pCO₂ → HCO₃ → Compensation → Anion Gap.

Use: Common causes of respiratory alkalosis.

• Anxiety / panic (including panic attacks)
• Pregnancy
• Early sepsis
• Mechanical ventilation at excessive rate or volumes

Use: Assess cause of hypoxaemia - separates normal-gradient from high-gradient causes

• A-a gradient = PAO2 (calculated, alveolar gas eq.) - PaO2 (measured on ABG)
• PAO2 (mmHg) = (FiO2 x 713) - (PaCO2 x 1.2)
• PAO2 (kPa) = (FiO2 x 93.8) - (PaCO2 x 1.2)

• Normal A-a gradient 12-20
• Increases by ~1 mmHg per decade of age

• Low inspired O2 content (low FiO2 or low PiO2)
• Hypoventilation (drugs or CNS depression)
• High altitude

• V/Q mismatch (pulmonary embolism)
• Atelectasis
• COPD
• Pneumothorax

Use: Oxygenation-adequacy quick check - is the patient hypoxic for the given FiO2?

• Expected PaO2 = FiO2 x 500
• e.g. 100 = 0.2 x 500 (room air)
• Check SpO2 and PaO2 against FiO2 to decide if patient is hypoxic

Use: Correct measured sodium for hyperglycaemia

• Corrected Na = measured Na + (glucose / 4) - all values in mmol/L

• Normal glucose 3.9-5.8 mmol/L (70-105 mg/dL)
• mmol x 18 = mg/dL

Use: Systematic order for interpreting an arterial blood gas

• 1. Oxygenation
• 2. pH
• 3. pCO2 (respiratory component)
• 4. HCO3 (renal/metabolic component)
• 5. Compensation
• 6. Anion gap

Use: Baseline daily fluid + electrolyte prescription for a patient with no extra losses.

• H2O - 30 ml/kg
• Na+ - 1.5 mmol/kg/day
• K+ - 1.0 mmol/kg/day

Use: Three interchangeable ways to estimate daily water need.

• Metabolic rate: 1 ml/kcal
• Body surface area: 1.5 L/m2
• Weight: 30 ml/kg

Use: Hourly maintenance fluid rate in children by weight.

• 4 ml/kg/hr for first 10 kg
• 2 ml/kg/hr for next 10 kg
• 1 ml/kg/hr subsequently
• Example (25 kg child): 4x10=40 + 2x10=20 + 1x5=5 = 65 ml/hr

Use: Framework for the total volume to prescribe over 24 h.

• Total = basal maintenance + pre-existing deficits + ongoing losses

• Haemorrhage, drains, fistulae, NG aspirate, insensible, 3rd space

Use: Estimating water lost that you cannot measure directly.

• H2O lost by evaporation from skin and lungs
• Excludes sweat (a salty exocrine secretion)
• Allow 50 ml/hr in unstressed patients
• Increases by 10% per degree of pyrexia

Use: Distribution of total body water across compartments.

• Total body water 42 L = 60% body weight (range 45-75%)
• ICF 28 L
• ECF 14 L
• - intravascular / plasma 3 L
• - interstitial / tissue fluid 11 L

Use: Predicts how much of an infused litre stays in the plasma.

• Diffuses to all compartments: 67% -> ICF, 33% -> ECF (333 ml)
• Of ECF: 2/3 -> ISF, 1/3 stays in plasma = only 111 ml

• Confined to ECF: 2/3 -> ISF, 1/3 stays in plasma = 333 ml

Use: Match replacement fluid to the fluid being lost (mmol/L Na/K/Cl/HCO3).

• Plasma: 140 / 4 / 100 / 25
• Saliva: 20 / 10 / 30 / 30
• Gastric: 20 / 10 / 140 / 0
• Bile: 150 / 10 / 80 / 35
• Ileal: 130 / 5 / 100 / 30

Use: Reference compositions of the common crystalloids.

• 150 mmol/L NaCl, isosmotic, pH 5 ('nothing normal about it')

• Glucose 50 g/L, 200 kcal/L, isosmotic
• Rapidly metabolised to CO2 + H2O = effectively just water

• Na+ 131, K+ 5, Ca2+ 2, Cl- 111, lactate 29 (-> HCO3- in liver)

Use: Small particles exerting osmotic pressure across endothelium.

• Gelofusine = 4% succinylated gelatin
• Haemaccel = 3.5% urea-linked gelatin
• Inexpensive; might cause allergy

• MW 250-450K Daltons
• Can impair coagulation; low incidence of allergy; more expensive

• Albumin, dextrans

Use: Titrate fluid to stroke volume (oesophageal Doppler measures blood flow by ultrasound).

• Measure stroke volume -> give a fluid challenge
• SV rises? Yes -> repeat the challenge
• SV rises? No -> monitor SV
• Monitored SV falls? Yes -> give another challenge

Use: Structured work-up of a patient with a suspected fluid deficit.

• NBM duration, vomiting, diarrhoea, pyrexia, blood loss, surgery

• History - symptoms of dehydration
• Examination - signs of reduced perfusion
• Investigation - blood + urinalysis

Use: Classifies intensity of inpatient care by monitoring and organ-support needs

• Level 0 — requires hospital admission; ward-based care
• Level 1 — additional monitoring, clinical input or advice (outreach); or recently discharged from ICU
• Level 2 — single-organ monitoring and support; advanced monitoring
• Level 3 — advanced organ support; two or more organ-system failures

Use: When to escalate from non-invasive to invasive (intubation + mechanical) ventilation

• Life-threatening hypoxaemia
• Failure of NIV
• Depressed conscious level — GCS <8
• Airway protection (e.g. burns)
• Severe dyspnoea

Use: Targets vasoactive therapy to the deranged haemodynamic variable

• BP = CO × TPR
• CO = SV × HR
• ∴ BP = (SV × HR) × SVR
• Values measured via cardiac-output monitoring

• Low SV → fluids
• Low SVR → vasopressors
• Low CO despite fluids → inotropes

Use: Systematic initial assessment of any critically ill patient; underpins the Assess – Treat – Reassess concept

• A – Airway
• B – Breathing
• C – Circulation
• D – Disability
• E – Exposure

• Complete initial assessment
• Treat life-threatening problems (as you find them, before moving on)
• Reassessment
• Assess effects of treatment / interventions
• Call for help early

• Personal safety
• Patient responsiveness

• Assess – Treat – Reassess loop
• Emphasis on early recognition of the deteriorating patient

Use: Rapid Disability (D) consciousness assessment; alternative to GCS

• A – Alert
• V – responds to Voice (verbal)
• P – responds to Pain
• U – Unresponsive

Use: Disability (D) module of ABCDE – assessment and treatment

• AVPU or GCS
• Pupils
• Random blood sugar

• ABC
• Blood glucose – if < 4 mmol/L (70 mg/dl) give glucose
• Treat underlying cause
• Check drug chart

Use: Airway (A) step of ABCDE – causes, recognition, management

• CNS depression
• Blood
• Vomit
• Foreign body
• Trauma
• Infection
• Inflammation
• Laryngospasm
• Bronchospasm

• Talking
• Difficulty breathing, distressed, choking
• Shortness of breath
• Noisy breathing – stridor, wheeze, gurgling
• See-saw respiratory pattern, accessory muscles

• Airway opening – head tilt, chin lift, jaw thrust
• Simple adjuncts – oropharyngeal, nasopharyngeal airway
• Advanced techniques – e.g. LMA, tracheal tube
• Remember: oxygen and removal of any secretions

Use: Breathing (B) step of ABCDE – causes, recognition, treatment

• Decreased respiratory drive – CNS depression
• Decreased respiratory effort – muscle weakness, nerve damage, restrictive chest defect, pain from fractured ribs
• Lung disorders – pneumothorax, haemothorax, infection, acute exacerbation COPD, asthma, pulmonary embolus, ARDS

• Look – respiratory distress, accessory muscles, cyanosis, respiratory rate, chest deformity, conscious level
• Listen – noisy breathing, breath sounds
• Feel – expansion, percussion, tracheal position

• Airway
• Oxygen
• Treat underlying cause – e.g. drain pneumothorax
• Support breathing if inadequate – e.g. ventilate with bag-mask
• Establish continuous monitoring – SpO2, respiratory rate, capnography

Use: Circulation (C) step of ABCDE – causes, recognition, treatment

• Primary – acute coronary syndromes, arrhythmias, hypertensive heart disease, valve disease, hereditary cardiac diseases
• Secondary – asphyxia, hypoxaemia, blood loss, hypothermia, septic shock, (drugs), (electrolyte / acid-base abnormalities)

• Pulse – tachycardia, bradycardia, regularity
• Peripheral perfusion – capillary refill time
• Blood pressure
• Organ perfusion – mental state, urine output
• Bleeding, fluid losses

• Airway, Breathing
• Oxygen
• IV/IO access, take bloods
• Establish ECG monitoring
• Treat cause
• Fluid challenge
• Haemodynamic monitoring
• Inotropes / vasopressors

Use: Classify a relative/absolute deficiency of cellular oxygen by mechanism

• Hypoxaemic — low arterial partial pressure
• Anaemic — low / abnormal haemoglobin
• Ischaemic — low cardiac output / interrupted blood supply
• Histotoxic — e.g. cyanide poisoning, CO

Use: Four mechanisms of low arterial PO2

• Low inspired O2 (FiO2) — O2-depleted environment, dilution of inspired O2, altitude
• Alveolar hypoventilation
• Impaired pulmonary diffusion
• V/Q mismatch / shunt — intrapulmonary vs extrapulmonary (PE, shunt)

Use: Split causes of hypoventilation by central vs peripheral

• Drugs
• Hypocapnia (low CO2)
• Intracranial pathology — head injury, tumour
• Removal of hypoxic drive / COPD

• Airway obstruction
• Restriction — pain, obesity, ascites, bandaging
• Muscular / neurological — spinal injury, MND, muscular dystrophy, drugs
• Mechanical — flail chest, pneumothorax, COPD

Use: Recall causes of impaired pulmonary diffusion

• Pulmonary oedema
• Drowning
• Pulmonary fibrosis

Use: Predict O2 affinity/unloading from curve shifts

• Decreased temperature
• Decreased 2,3-DPG
• Decreased H+
• CO

• Increased temperature
• Increased 2,3-DPG
• Increased H+

• Sigmoid curve from positive cooperativity
• Hb A = 2 alpha + 2 beta chains; each subunit binds 1 O2

Use: Match O2 concentration to the clinical setting

• All emergencies → high concentration
• Correct hypoxia → known concentration
• Pre-operative → 100%
• Post-operative supplement → ~30%
• Therapeutic hyperoxia → high concentration / hyperbaric (chamber gives higher-than-normal O2 to improve recovery)

Use: Pick delivery device by target FiO2 and performance

• Nasal prongs — set at 2 L/min, low conc 24-35%
• Variable-performance oxygen mask — 35-60%
• HAFOE / Venturi mask — fixed performance, delivers prescribed concentration irrespective of respiratory pattern
• Hudson + non-rebreathing bag — 60-80+%, short-term
• Anaesthetic mask & circuit — only way to deliver 100% O2

Use: Recall the harms of oxygen therapy

• Oxygen toxicity — lung, brain, eye
• Respiratory depression / CO2 narcosis
• Drying effect
• Fire hazard — facial burns and deaths reported when patients smoke during O2 therapy

Use: Detect and monitor inadequate oxygenation

• Increased respiratory rate
• Increased pulse rate
• Confusion, agitation or reduced conscious level
• Cyanosis (unreliable)

• Observation of clinical state
• Pulse oximetry
• Arterial blood gases

Use: Structured assessment & multimodal treatment of acute pain. Analgesia = relief from pain; anaesthesia = insensitivity to pain; sedation = reduced level of consciousness.

• Transduction — nociceptors detect damage (injury, temperature, chemical, mechanical); sensitised by prostaglandins, K⁺, histamine, bradykinin
• Transmission — Aδ fibres (fast, sharp) & C fibres (slow, dull)
• Perception — thalamus, limbic system, cortex
• Modulation — descending inhibitory pathways (GABA/glycine, brainstem projections); gate control theory at the dorsal horn; sensitisation (peripheral & central) increases excitability

• Acute (superficial/somatic/visceral) vs chronic (persists >3 months, impacts quality of life)
• Nociceptive (somatic vs visceral) vs neuropathic (nervous-system lesion/dysfunction — shooting, burning, numbness)
• Cancer pain — infiltration, obstruction, inflammation, or treatment

• Physiological — autonomic (BP, HR, RR)
• Patient-reported — verbal (mild/mod/severe), visual analogue scale (10 cm line), verbal numerical rating scale (0–10); record with each set of vital signs
• FLACC — for non-verbal patients

Untreated pain harms: hyperventilation (resp. alkalosis), ↑O₂ demand (→ metabolic acidosis, MI), impaired lung expansion (post-op chest infection), neuroendocrine stress, immune suppression, delayed mobilisation, ↑DVT risk, longer stay.

Step up: non-opioid (± adjuvant) → weak opioid + non-opioid → strong opioid + non-opioid. Combine drug treatment with regional analgesia, physical methods (TENS, nerve blocks) and psychological methods for an additive, opioid-sparing effect.

Drug	Mechanism	Notes / dose	Key side effects
Paracetamol	Inhibits CNS prostaglandin synthesis	Analgesic + antipyretic; 1 g every 6 h (adult); PO/PR/IV	Low incidence — rash; liver impairment in overdose
NSAIDs	Inhibit COX → ↓ prostaglandins	Ibuprofen, diclofenac, naproxen, aspirin, indomethacin; COX-2 selective: celecoxib, meloxicam	GI ulceration, renal impairment, asthma (~10% NSAID-sensitive), bleeding (platelet inhibition)
Strong opioids	Agonist at μ/δ/κ opioid receptors	Morphine (gold standard), fentanyl, oxycodone, diamorphine, pethidine, hydromorphone, buprenorphine	N&V, sedation, respiratory depression, constipation, pruritus, tolerance/addiction, urinary retention
Weak opioids	Partial receptor binding — ceiling effect	Codeine 60 mg qds, dihydrocodeine 30 mg qds, tramadol 50 mg qds	As opioids (milder)
Compound	Paracetamol + weak opioid	Co-codamol, co-dydramol, co-proxamol	Combined
Local anaesthetics	Block Na channels (stop impulse propagation)	Lidocaine, bupivacaine, levobupivacaine, ropivacaine; topical/infiltration/epidural/nerve block	Toxicity: early — peri-oral tingling, tinnitus, metallic taste, confusion; late — blurred vision, dysrhythmias, convulsions, arrest
Entonox	50% N₂O + 50% O₂	Self-administered; short sharp procedures; rapid on/off; strong analgesic, weak anaesthetic	Few side effects
Adjuvants	Various	Neuropathic: TCA (amitriptyline), anticonvulsant (gabapentin); also ketamine, clonidine, baclofen, buscopan, sumatriptan	Per agent

Morphine dosing: <70 y — 10 mg IM/SC, 20 mg oral; >70 y — 5 mg IM/SC, 10 mg oral. Water-soluble; titrate to pain; can be 2-hourly; addiction rarely an issue in acute pain.

• Patient-controlled analgesia (PCA) — post-op/trauma/pancreatitis/failed epidural; morphine 1 mg bolus, 5 min lockout; needs a loading dose; fentanyl if opioid SE or renal failure; no other opioids alongside PCA
• Epidural — continuous infusion (fentanyl + bupivacaine, or plain bupivacaine); patient-controlled epidural analgesia (PCEA) improves pain relief, lowers cumulative dose & side effects
• Spinal (intrathecal) — lower volume than epidural; diamorphine good; SE nausea, urinary retention, sedation/respiratory depression
• Nerve blocks — targeted, opioid-sparing, part of multimodal approach; orthopaedic surgery, rib fractures, gynae, hernias; risk of motor block, sensory loss, nerve damage, LA toxicity

CBT (distraction, education, reassurance, imagery, relaxation, hypnosis); physical (counter-stimulation, mobilisation/immobilisation, hot/cold, massage, TENS, acupuncture).