Critical Care Medicine

01

Shock

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Universal Features

Altered mentation · cap refill >2s · lactate >3 · hypotension · mottled skin · tachycardia · tachypnea · UO <0.5 mL/kg/h

Hemodynamic Profiles

The classic five-phenotype framework

Type	CO	PCWP	SVR	Clinical Picture
Cardiogenic	↓	↑	↑	↑ CVP · S3 · pulmonary crackles · edema · CVD RF · MI most common cause
Hypovolemic	↓	↓	↑	Volume loss: hemorrhage · dehydration · vomiting · diarrhea
Obstructive	↓	↕	↑	Cardiac tamponade · PE · tension pneumothorax
Anaphylactic	↑	→	↓	Rash · urticaria · angioedema · wheezing · stridor
Septic	↑ → ↓	↕	↓	Infection

02

Sepsis

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Sepsis = infection + organ dysfunction.

SIRS Screen (≥2)

HR >90 · T >38 or <36 · RR >20 · PaCO₂ <32 · WBC >12 or <4

ICU required › admission ≤6h
Hypotension › rapid administration ≥30 mL/kg crystalloid within 3h › central line › norepinephrine 0.05–0.5 mcg/kg/min › vasopressin 2.4 units/hr · target MAP ≥65
- Fluid responsiveness: 10–15% ↑ SV or CO after 500 mL IVF
- Cardiac dysfunction › dobutamine 2.5–10 mcg/kg/min
- Elderly › target MAP 60–65
BCs › broad-spectrum antibiotics within 1h · cover MRSA / MDR / fungal if RF
- Source control · culture potential sites of infection · CXR · URM
- Glucose target 7.8–10
- PCT <0.5 › DC antibiotics

Septic Shock

Sepsis + persistent hypotension requiring vasopressors to maintain MAP ≥65 + lactate >2.

› ≥2 antibiotics from different classes. Norepinephrine ≥0.25 mcg/kg/min for >4 hrs › IV hydrocortisone 200–400 mg/day.

03

Acute Respiratory Failure

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Hypoxemic respiratory failure: V/Q mismatch › HFNC › NIV › MV

ARDS — Berlin Criteria

Onset <1 week · non-cardiogenic pulmonary edema · bilateral infiltrates on CXR/CT/US · SpO₂/FiO₂ <315 + SpO₂ ≤97%

ARDS Severity

Severity	PaO₂/FiO₂	Support
Mild	201–300	NIV/CPAP PEEP ≥5 or HFNC >30 L/min
Moderate	101–200	PEEP ≥5
Severe	≤100	PEEP ≥5

Etiology: pneumonia, drowning, thoracic trauma, hemorrhagic shock, smoke/toxic inhalation, fat emboli, post lung transplant, severe sepsis, TRALI, shock, pancreatitis
MV: A/C-VC · Vt 4–8 mL/kg PBW · Pplat <30 cm H₂O
Target SpO₂ 88–92% or PaO₂ 55–80 mmHg · permissive hypercapnia · pH >7.25
Moderate/severe › high PEEP, prone positioning >12h/d
Severe › neuromuscular blockade, VV-ECMO (PaO₂/FiO₂ <80)
Dexamethasone 20 mg IV × 5d then 10 mg IV × 5d, started within 24–48h

Hypercapnic Respiratory Failure

Etiology: COPD, BA, MG, ALS, MS, chest wall skeletal disorders, obesity, opioids, sedatives › ABG › BiPAP.

Neuromuscular weakness: >20% FVC decrease while supine · MIP <−60 cm H₂O or <50% predicted · MEP <40 cm H₂O or <50% predicted.

Nocturnal hypoventilation › polysomnography. CO₂ narcosis › somnolence, myoclonic jerks. BA exacerbation with normal/high PaCO₂ › impending respiratory arrest.

Inhalation

Smoke Inhalation

Wheezing, cough, dyspnea, 12–36h after exposure. CO, cyanide › pneumonia (Staphylococcus, Pseudomonas).

Visibly damaged airway / stridor › immediate intubation.

Cyanide › ↑ serum lactate › hydroxocobalamin.

Trauma

Fat Embolism Syndrome

Long bone fracture › respiratory insufficiency · neurologic dysfunction · petechial rash.

04

Principles of Critical Care

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Indications: COPD exacerbation · cardiogenic pulmonary edema · neuromuscular disease · recently extubated high-risk patients · OHS
CI: respiratory arrest · inability to protect airway · excessive secretions/nausea/vomiting · agitation/lack of cooperation · facial surgery · facial trauma · airway obstruction · hemodynamic instability
No improvement ≤2h › consider intubation

↓ PaCO₂

↑ RR, ↑ Vt

↑ SpO₂

↑ FiO₂, ↑ PEEP, ↑ inspiratory time

PIP

Airway resistance + lung compliance · <35 cm H₂O

Pplat

Lung compliance · <30 cm H₂O

PEEP

Pressure at end of respiratory cycle

Driving pressure

Pplat − PEEP · <15

High RR + auto-PEEP › hypotension
Difficult ventilation: bronchospasm · secretions · obstructing mucus plug · agitation with dyssynchrony with MV

Daily SAT › stop all sedatives and analgesia and observe patient
Weaning criteria: reversal of reason for intubation · PaO₂ >60 · FiO₂ <40% · PEEP <8 · ability to perform work of breathing (normal CO₂, normal pH, adequate cardiac function, adequate diaphragm function)
Extubation criteria: adequate cough · minimal secretions · alert · following commands · no sedation · no increased risk of airway obstruction · SpO₂ >90% · FiO₂ ≤50% · PEEP <5 · pH >7.3
SBT: PSV 30 min
- Failure: tachypnea · ↑ WOB · tachycardia · hypotension · desaturation
- RSBI = RR / Vt >105 › predictor of extubation failure

MV › RASS −2 to +1 (light sedation) › propofol or dexmedetomidine
- Dexmedetomidine › bradycardia, hypotension
Daily sedation interruption · nurse-driven titration
Analgesia › opioids › respiratory depression, delirium, dependence
- Adjuncts: paracetamol, NSAIDs
- Post-op › low-dose ketamine
- Neuropathic › gabapentin, pregabalin, carbamazepine
Non-pharmacological analgesia: cold therapy · relaxation · music · massage

Sleep: reduce noise, light, and nighttime disruptions › melatonin
- MV › assist-control overnight
Peripheral wide-bore IV catheter › highest flow rate
Undifferentiated shock › POCUS
Remove unneeded catheters and drains

RF: transfusions · aged ≥70y · dementia · prior coma · emergency surgery/trauma · high APACHE/ASA scores · h/o delirium · vision/hearing impairment · poor nutritional status · poor functional status · multiple medical comorbidities · kidney disease · alcohol use disorder · depression · polypharmacy
Triggers: poorly controlled pain · deliriogenic drugs (benzodiazepines, anticholinergics, opioids) · disruption of sleep-wake cycle · constipation · dehydration · urinary retention · severe illness · infection · hypoxia · surgical stress · urinary catheter · sensory deprivation
Screening: CAM-ICU
Early mobility · promote sleep · optimize hearing/vision · frequent reorientation · reduce deliriogenic drugs/transfusions · engage family members · allow sunlight · redirect with calm tones · manage pain. Avoid physical restraints.
Severe agitation/hallucinations/distress › haloperidol or sedation
MV › dexmedetomidine
Benzodiazepines: alcohol withdrawals, seizures
↑ Risk of cognitive impairment and ICU length of stay

Enteral nutrition preferred · initiate at 24–48h
- Gradually increase over 3–7 days
TPN › GI mucosal atrophy · translocation of gut bacteria into bloodstream › infection
- Do not start <7d from acute illness

05

Disorders of Consciousness

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Neuroprognostication Post Cardiac Arrest

Absent pupillary reflex at 72h
Status myoclonus <7d
EEG bilaterally absent N20
CT brain ≤72h: reduced gray-white matter differentiation
MRI brain ≤72h: high DWI

Death Determination

DCC · Circulatory

Invasive arterial BP pulse pressure <5 mmHg for 5–10 min + continuous ECG.

Death Determination

DNC · Neurologic

Absence of consciousness (supraorbital notch + peripheral stimulation) + absence of brainstem function (pupillary, corneal, cough, gag, vestibulo-ocular reflexes) + absence of capacity to breathe (no respiratory effort, pH ≤7.28, pCO₂ >60, pCO₂ ↑ >20).

Prerequisites: mechanism causing devastating brain injury, neuroimaging, absence of confounders (core T ≥36, <48h after arrest, drugs, shock, metabolic disorders).

Neurological injuries › intubation if GCS <8 · head of bed >45° · normothermia · euglycemia · normocapnia · IVF NS

Increased ICP

Hypertonic 3% saline 250 mL bolus or mannitol 0.25–1 g/kg q6–8h · hyperventilation CO₂ 26–30 · ICP monitoring <20 mmHg · optimize sedation · CPP >60 · EVD for hydrocephalus · consider decompressive craniotomy.

Unexplained coma › thiamine, glucose if hypoglycemic, naloxone if opioid OD suspected

06

ICU-Acquired Weakness

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Risk Factors

Hyperglycemia · sepsis · multiple organ dysfunction · SIRS

Three Patterns of Weakness

Differential by distribution, sensation, and reflexes

Pattern	Distribution	Sensation / Reflexes	Association
Critical illness myopathy	Flaccid quadriparesis · proximal > distal · normal CNs · weak facial muscles · failure to wean	Sensation spared · normal or hyporeflexia	Steroid use. CK may be ↑. Dx: NCS, EMG.
Critical illness polyneuropathy	Flaccid quadriparesis · failure to wean · normal CNs	↓ Distal pin prick/touch · hyporeflexia	Severe sepsis
Glucocorticoid-induced myopathy	Gradual onset 1–3 months · proximal muscles · lower > upper	Normal sensation · normal reflexes	Cushing's syndrome: DM, mood alteration, skin fragility, osteoporosis. ↓ steroids › improvement in 3–4 weeks.

Prevention: early mobility · physical therapy · occupational therapy · avoidance of early parenteral nutrition · glucose control.

07

Toxicology

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Initial Workup & Calculations

Labs

Anion gap, osmolar gap, drug levels (paracetamol, salicylates, EtOH), βhCG

Anion gap

Na − Cl − HCO₃ · <12

Osmolar gap

Measured − calculated osmolality · <10

Calc. osm

2 × Na + Glucose + BUN

Consult poison control. Intentional OD › consult psychiatry.

Features: blurry vision, mydriasis, flushed skin, hyperthermia, dry mouth, urinary retention, shaking, tachycardia, absent bowel sounds, hypotension, seizures, ↓LOC, agitation, psychosis, delirium, arrhythmia
ECG › wide QRS › VT/VF
≤2h › activated charcoal 1 g/kg (max 50 g)
QRS >100 › NaHCO₃ 1–2 mEq/kg IV + infusion · pH 7.5–7.55 › IV MgSO₄ › lidocaine infusion
Refractory + unstable › lipid emulsion, VA ECMO

Features (1–2h): tinnitus, nausea, vomiting, hyperventilation, fever › coma, seizures, pulmonary edema, arrhythmia, thrombocytopenia, AKI
Toxic level >2.9–3.6 mmol/L · q2–4h
Respiratory alkalosis › HAGMA
≤2h › activated charcoal 1 g/kg (max 50g)
NaHCO₃ infusion · pH 7.4–7.55, urine pH 7.5–8
HD indications: level >7.2 · hypoxemia · altered LOC · renal failure + level >6.5 · hemodynamic instability · persistent electrolyte/acid-base derangement (pH <7.2) · hepatic compromise + coagulopathy · volume overload preventing NaHCO₃ infusion

Toxic: >250 mg/kg or >12 g in ≤12h · >350 mg/kg › severe liver toxicity
Stage I (30 min–24h): nausea, vomiting, diaphoresis, pallor, lethargy, malaise, asymptomatic
Stage II (24–72h): RUQ pain, jaundice, oliguria, ↑ AST/ALT
Stage III (72–96h): jaundice, hepatic encephalopathy, marked ↑ AST/ALT, coagulopathy, bili >68, hypoglycemia, lactic acidosis, hyperammonemia, bleeding, renal failure
Stage IV (96h–14d): recovery; hepatic necrosis may develop
Paracetamol level at 4h. ≤4h › activated charcoal 1 g/kg (max 50g)
NAC indications: level above treatment line on R-M nomogram · single ingestion >7.5 g (150 mg/kg) · unknown ingestion time + concentration >66 µmol/L · liver injury
NAC infusion reactions: mild flushing/urticaria › antihistamine or steroid; severe anaphylaxis/angioedema › stop infusion
DC NAC: INR <1.3 + ALT <100 + paracetamol level <132

MetHb Levels & Features

MetHb	Features
3–15%	SpO₂ 90–95%, slate gray skin
15–20%	Cyanosis, chocolate brown blood, SpO₂ 85%
20–50%	Dizziness, syncope, fatigue, headache, weakness, dyspnea
>50%	Coma, seizures, metabolic acidosis, arrhythmias, death

HbO₂ dissociation curve left-shifted · PaO₂ high, SpO₂ low (mismatch)
Causes: benzocaine, lidocaine, dapsone, nitrates, chloroquine, sulfonamides, hemolysis, Hb M, NADH MetHb reductase deficiency
Methylene blue 1–2 mg/kg CI G6PD, serotonin syndrome

Features: N/V, diarrhea, dizziness, lethargy, slurred speech, ataxia, tremor, myoclonic jerks, hypernatremia
ECG › TW flattening · QT prolongation · bradycardia. WBC 15–20.
Whole bowel irrigation: SR formulation, symptomatic, unknown amount, >40 mg/kg, <6h, rising levels
HD indications: arrhythmias, seizures, severely abnormal mental status, level ≥5 mmol/L, level ≥4 mmol/L + Cr >176
IVF NS at 1.5× maintenance

Features: N/V, abdominal pain, delirium, fatigue, visual disturbances (blurred, halos), seizures, bradycardia, arrhythmias
≤1h › activated charcoal
Digoxin-specific Fab (Digibind, Digifab) indications: dysrhythmias, hemodynamically unstable, K >5, severe GI symptoms, >10 mg, renal failure, altered LOC

Decontamination · FiO₂ 100%
Muscarinic (DUMBELS): diaphoresis · diarrhea · urination · miosis · bronchospasm · bradycardia · bronchorrhea · emesis · lacrimation · salivation
Nicotinic (MATCH): muscle weakness/fasciculations · adrenergic stimulation (mydriasis) · tachycardia · CNS (lethargy, seizures, coma, resp depression) · HTN
Delayed neuropathy 1–3 weeks › painful stocking-and-glove paresthesia, symmetrical motor polyneuropathy
Atropine: 2 mg IV, double q3–5 min until pulmonary symptoms relieved + infusion

Opioid OD: miosis, respiratory depression, lethargy, confusion, hypothermia, bradycardia, hypotension › naloxone, repeat PRN
Benzodiazepine OD: CNS depression › supportive care. Flumazenil › seizures.
Sympathomimetic (cocaine, amphetamines, MDMA): tachycardia, HTN, diaphoresis, agitation, seizures, mydriasis, hyperthermia › MI, rhabdomyolysis, renal failure, liver failure, CVA
- Agitation / HTN › benzodiazepines
- Cocaine + chest pain › ASA + nitroglycerin
- MDMA/amphetamines › hyponatremia

Alcohol poisoning: AKI, metabolic acidosis › NaHCO₃ infusion · pH 7.35
- HD: end-organ dysfunction (seizures, coma, visual defects, renal failure), pH ≤7.15, persistent acidosis, high AG, very high parent alcohol level
Ethylene glycol: ↓LOC, frank hematuria, flank pain, oliguria, hypocalcemia, CN palsies, tetany, high AG and OG › fomepizole or ethanol + thiamine 100 mg IV + pyridoxine 50 mg IV
- URM › calcium oxalate crystals
- ECG › prolonged QTc (hypocalcemia)
Methanol: ↓LOC, blindness, afferent pupillary defect, mydriasis, retinal sheen, optic disc hyperemia, high AG and OG › fomepizole or ethanol + folic acid 50 mg IV QDS
Isopropyl alcohol / ethanol (raised OG, NAGMA) › supportive care

CO poisoning: HbO₂ curve left-shifted · SpO₂ overestimates 100% · HAGMA · lactic acidosis › remove source, ventilate, HFNC or MV FiO₂ 100%
- Early (<4h): flu-like symptoms, frontal headache, lightheadedness, difficulty concentrating, nausea
- End-organ hypoxia: arrhythmias, myocardial ischemia, CM, confusion, delirium, syncope, coma, dyspnea, pulmonary edema, cherry red skin, skin bullae, retinal hemorrhages
- COHb >10% abnormal · CT/MRI › bilateral globus pallidus opacities
- Hyperbaric O₂: within 6h exposure, COHb ≥25%, seizure/coma, syncope, persistent neuro deficits, pregnancy, cardiac ischemia
Cyanide: abrupt onset, bitter almonds smell, high VBG and ABG SaO₂, HAGMA, severe lactic acidosis › hydroxycobalamin 5 g IV over 15 min SE: anaphylactoid, HTN · acidosis › NaHCO₃

08

Hyperthermia & Hypothermia

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The Hyperthermia Syndromes

Differential by onset, rigidity, and reflexes

Syndrome	Onset	Tone / Reflexes	Trigger	Antidote
Serotonin syndrome	<24h	Hypertonia, hyperreflexia, clonus, bilateral babinskis	Antidepressants, amphetamines, cocaine, MDMA, levodopa, tramadol, meperidine, St John's wort, valproate, triptans, ergotamine, fentanyl, buspirone	Benzodiazepines › cyproheptadine
Neuroleptic malignant	Days–weeks	Lead-pipe/cogwheel rigidity, hyporeflexia, catatonia	Antipsychotics, domperidone, metoclopramide, prochlorperazine, L-dopa withdrawal	Benzodiazepines › dantrolene or bromocriptine
Malignant hyperthermia	Intra-op	Rigidity, hyporeflexia, rhabdomyolysis	Inhaled volatile anesthetics (halothane, isoflurane), succinylcholine, decamethonium. RYR1 gene. ↑ EtCO₂, ↑ T >1°C.	Dantrolene + rapid cooling
Heat stroke	Exposure	Variable · ± rhabdomyolysis · AKI	Anticholinergics, sympathomimetics, diuretics, athlete, age >70y. Criteria: T >40°C + CNS abnormalities.	Rapid cooling to `<39°C`

Hyperthermia Universal Steps

Stop offending agent · cool · supportive care. Genetic testing (RYR1) and muscle biopsy for MH.

Hypothermia Staging

Stage	Temp	Features	Management
Mild	32–35°C	Tachycardia · hypertension · tachypnea · shivering · alert · poor judgment	Warming, supportive
Moderate	28–32°C	Bradycardia · hypotension · ↓ RR · ↓ CO · ↓ AKI · somnolence · no shivering · supraventricular arrhythmia	Active external warming · 42°C crystalloid fluids
Severe	<28°C	Coma · absent reflexes · apnea · ventricular arrhythmia · asystole	ECMO or cardiopulmonary bypass · peritoneal/pleural lavage

ECG › Osborn waves
Cardiac arrest › prolonged CPR + active external warming

09

Anaphylaxis

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Clinical Picture

Pruritus · flushing · hives · conjunctival pruritus · angioedema · dyspnea · stridor · hypoxemia · wheeze · vomiting · diarrhea · cramping abdominal pain · hypotension · syncope · incontinence. Mediated by IgE and mast cells.

Triggers: foods, medications, insect stings, radiocontrast, perioperative agents, exercise, seminal fluid, idiopathic

Epinephrine IM 0.01 mg/kg (max 0.5 mg), repeat q5–15 min PRN. (1:1000 = 1 mg/mL)

IV: 0.05–0.1 mg over 5 min, then infuse 2–10 mcg/min titrated to BP (1:10,000 = 0.1 mg/mL)
Adjuncts: inhaled SABA, antihistamines, supplemental O₂, IV crystalloid fluids, vasopressors, corticosteroids
Observation ≥12h · prescribe self-administered epinephrine at discharge

A study guide to critical care.

Shock

Hemodynamic Profiles

Sepsis

Acute Respiratory Failure

ARDS Severity

Smoke Inhalation

Fat Embolism Syndrome

Principles of Critical Care

Disorders of Consciousness

DCC · Circulatory

DNC · Neurologic

ICU-Acquired Weakness

Three Patterns of Weakness

Toxicology

MetHb Levels & Features

Hyperthermia & Hypothermia

The Hyperthermia Syndromes

Hypothermia Staging

Anaphylaxis

No Stalking
Allowed!

This Is Not
A Café.