Study guide
23.3 Perioperative Critical Care for High-Risk Surgical Patients
ABIM Critical Care Medicine Study Guide Exam
Track your progress as you read
Finished sections get a check mark.
1 Chapter 1: Exam Orientation: Format, Blueprint & Study Strategy
1.1 ABIM Critical Care Medicine Exam: Format, Blueprint & Study Strategy
2 Chapter 2: Acute Respiratory Failure & ARDS
2.1 ARDS Definition, Pathophysiology & Phenotypes 2.2 Lung-Protective Mechanical Ventilation 2.3 Refractory ARDS: Prone Positioning, Neuromuscular Blockade & VV-ECMO
3 Chapter 3: Obstructive Airways, Pulmonary Vascular & Pleural Emergencies
3.1 Severe Asthma & COPD Exacerbations in the ICU 3.2 Massive & Submassive Pulmonary Embolism 3.3 Pulmonary Hypertension & Right Ventricular Failure in the ICU 3.4 Massive Hemoptysis, Complex Pleural Effusions & Thoracic Drainage
4 Chapter 4: Airway, Parenchymal & Nonthrombotic Pulmonary Emergencies
4.1 Airway Management, Upper-Airway Obstruction & Artificial-Airway Complications 4.2 Diffuse Alveolar Hemorrhage, Interstitial Lung Disease, Pulmonary Vasculitis & Noncardiogenic Edema 4.3 Severe Community-Acquired & Viral Pneumonia 4.4 Nonthrombotic Embolism (Air, Fat, Amniotic Fluid, Tumor, Septic) & Acute Chest Syndrome
5 Chapter 5: Mechanical Ventilation Modes, Dyssynchrony & Liberation
5.1 Mechanical Ventilator Modes & Advanced Breath Delivery 5.2 Patient-Ventilator Dyssynchrony & Waveform Analysis 5.3 Ventilator Liberation, Spontaneous Breathing Trials & Post-Extubation Support
6 Chapter 6: Shock Syndromes & Hemodynamic Principles
6.1 Shock Classification, Cellular Pathophysiology & Biomarkers 6.2 Hemodynamic Monitoring: Arterial Lines, CVP & Pulmonary Artery Catheter 6.3 Dynamic Assessment of Fluid Responsiveness & Resuscitation Targets
7 Chapter 7: Vasoactive Therapies & Mechanical Circulatory Support
7.1 Vasopressors & Inotropes: Pharmacology & Clinical Titration 7.2 Temporary Mechanical Circulatory Support: IABP, Impella & TandemHeart 7.3 Venoarterial ECMO (VA-ECMO) & Differential Hypoxemia 7.4 Post-Cardiac Arrest Care, Targeted Temperature Management & Neuroprognostication
8 Chapter 8: Acute Kidney Injury & Renal Replacement Therapy
8.1 KDIGO AKI Classification, Etiologies & Diagnostic Evaluation 8.2 Continuous Renal Replacement Therapy (CRRT) vs Intermittent Hemodialysis 8.3 Indications & Timing for RRT in Critical Illness: AKIKI & STARRT-AKI
9 Chapter 9: Electrolyte, Acid-Base & Endocrine Emergencies
9.1 Severe Dysnatremias: Hyponatremia, Hypernatremia & Osmotic Demyelination 9.2 Potassium, Calcium, Magnesium & Phosphate Disorders 9.3 Complex & Mixed Acid-Base Disorders: Boston vs Copenhagen vs Stewart 9.4 Endocrine Crises: DKA, HHS, Thyroid Storm, Myxedema Coma & Adrenal Crisis
10 Chapter 10: Glycemic Control, Hyperammonemia, Pituitary & Adrenal Disorders
10.1 ICU Glycemic Control & Severe Hypoglycemia 10.2 Non-Hepatic Hyperammonemia & Metabolic Encephalopathy 10.3 Pituitary Emergencies, Adrenal Excess & Critical Illness-Related Corticosteroid Insufficiency
11 Chapter 11: Acute Coronary Syndromes & Cardiac Arrhythmias
11.1 Acute Coronary Syndromes & Mechanical Complications of Myocardial Infarction 11.2 Critical Tachyarrhythmias: Atrial Fibrillation with RVR, VT & VF 11.3 Critical Bradyarrhythmias, Conduction Blocks & Temporary Cardiac Pacing
12 Chapter 12: Acute Heart Failure, Valvular & Pericardial Emergencies
12.1 Acute Decompensated Heart Failure & Cardiogenic Pulmonary Edema 12.2 Acute Valvular Regurgitation & Prosthetic Valve Emergencies 12.3 Pericardial Tamponade & Acute Aortic Syndromes
13 Chapter 13: Myocardial Disease, Hypertensive & Cardiac Device Emergencies
13.1 Fulminant Myocarditis, Stress & Peripartum Cardiomyopathy, and Hypertrophic Cardiomyopathy 13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm 13.3 Implanted Cardiac Devices, LVAD Emergencies & Electrical Storm
14 Chapter 14: Sepsis & Systemic Infectious Diseases
14.1 Sepsis-3 Definitions & Surviving Sepsis Campaign 2026 Guidelines 14.2 Refractory Septic Shock & Adjunctive Therapies 14.3 Multidrug-Resistant Pathogens & Antimicrobial Stewardship in the ICU
15 Chapter 15: ICU-Acquired & Severe Focal Infections
15.1 Hospital-Acquired & Ventilator-Associated Pneumonia 15.2 Central Line-Associated Bloodstream Infections & Catheter-Associated UTIs 15.3 Intra-Abdominal Sepsis, Necrotizing Soft Tissue Infections & CNS Infections
16 Chapter 16: Focal, Special-Host & Systemic Infections
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess 16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections 16.3 Infective Endocarditis, Device Infections & Other Focal Cardiovascular Infections 16.4 Antimicrobial Pharmacokinetics, Allergy, Toxicity & Infection Prevention 16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses
17 Chapter 17: Neurocritical Care & Coma
17.1 Coma, Altered Mental Status & Acute Delirium in the ICU 17.2 Status Epilepticus & Non-Convulsive Status Epilepticus 17.3 Acute Ischemic Stroke & Intracranial Hemorrhage
18 Chapter 18: Cerebrovascular Syndromes, Encephalopathy & Withdrawal States
18.1 Cerebral Venous Sinus Thrombosis, PRES & Reversible Cerebral Vasoconstriction Syndrome 18.2 Alcohol & Sedative Withdrawal, Wernicke Encephalopathy & Drug-Induced Encephalopathy
19 Chapter 19: Intracranial Hypertension & Neuromuscular Weakness
19.1 Intracranial Pressure Monitoring, Cerebral Perfusion & Tiered ICP Management 19.2 Acute Neuromuscular Respiratory Failure, ICU-Acquired Weakness & Brain Death Determination
20 Chapter 20: Traumatic Brain Injury, Spinal Cord Injury & Toxin-Mediated Paralysis
20.1 Traumatic Brain Injury Management & Paroxysmal Sympathetic Hyperactivity 20.2 Acute Spinal Cord Injury, Neurogenic Shock & Autonomic Dysreflexia 20.3 Toxin-Mediated Paralysis & Neuromuscular Crises: Botulism, Tetanus, Tick Paralysis & Myasthenic Crisis
21 Chapter 21: Gastrointestinal, Hepatic & Abdominal Emergencies
21.1 Acute Upper & Lower Gastrointestinal Bleeding in the ICU 21.2 Acute Liver Failure & Severe Acute Pancreatitis 21.3 Abdominal Compartment Syndrome & Acute Mesenteric Ischemia
22 Chapter 22: Luminal GI Emergencies & Complications of Cirrhosis
22.1 Esophageal, Gastric & Bowel Emergencies: Perforation, Obstruction, Ogilvie Syndrome & Colonic Ischemia 22.2 Complications of Cirrhosis: Alcohol-Associated Hepatitis, Hepatorenal Syndrome & Pulmonary Vascular Syndromes
23 Chapter 23: Trauma, Burns & Perioperative Critical Care
23.1 Polytrauma Resuscitation, Damage Control & Massive Transfusion 23.2 Severe Burn Injury, Inhalation Injury & Environmental Emergencies 23.3 Perioperative Critical Care for High-Risk Surgical Patients
24 Chapter 24: Thoracic Trauma, Environmental Injury & Obstetric Critical Care
24.1 Thoracic Trauma: Flail Chest, Pulmonary Contusion, Great Vessel & Tracheobronchial Injury 24.2 Environmental Injury: Drowning, Diving, Altitude, Heat, Cold, Electrical & Radiation 24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy
25 Chapter 25: Transplantation, Donor Management & Post-Cardiac Surgery Care
25.1 Solid Organ Transplant Recipients & Deceased Donor Management 25.2 Post-Cardiac Surgery Critical Care: Bleeding, Tamponade, Low Output & Vasoplegia
26 Chapter 26: Hematologic Emergencies, Toxicology, Critical Ultrasound & ICU Liberation
26.1 Hematologic Emergencies in the ICU: HIT, DIC, TMA & Anticoagulant Reversal 26.2 Critical Care Toxicology, Toxidromes & Specific Antidotes 26.3 Critical Care Point-of-Care Ultrasound (POCUS) 26.4 ICU Liberation, Analgosedation, Goals of Care & Critical Care Ethics
27 Chapter 27: Transfusion Medicine, Hematologic & Oncologic Disorders
27.1 Transfusion Medicine: Products, Thresholds, Reactions & Apheresis 27.2 Red and White Cell Disorders, Hemoglobinopathies, Factor Deficiencies & Hypercoagulable States 27.3 Oncologic Emergencies, Hematopoietic Cell Transplant Complications & Cellular Therapy Toxicity
28 Chapter 28: Clinical Pharmacology, Adverse Drug Reactions & Specific Poisonings
28.1 Pharmacokinetic Principles, Dose Adjustment & Drug Interactions in Critical Illness 28.2 Adverse Drug Reactions: Anaphylaxis, Severe Cutaneous Reactions & Hyperthermic Syndromes 28.3 Specific Poisonings: Sodium-Channel Blockers, Lithium, Valproate, Theophylline, Iron, Sulfonylureas & Methemoglobinemia
29 Chapter 29: Ethics, Research Methods, Administration & Abdominal Ultrasound
29.1 Advance Care Planning, Nonbeneficial Treatment, Informed Consent & Confidentiality 29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement 29.3 Abdominal, Vascular & Procedural Point-of-Care Ultrasound
23.3 Perioperative Critical Care for High-Risk Surgical Patients
Key Takeaways Explain This Topic AI
Perioperative risk assessment using the Revised Cardiac Risk Index (RCRI) and NSQIP calculators identifies patients at elevated risk for major adverse cardiac events, who benefit from goal-directed hemodynamic therapy (GDHT) optimizing stroke volume and tissue perfusion.
Postoperative expanding neck hematoma following cervical spine, thyroid, or carotid surgery causes lethal airway obstruction through laryngeal venous compression and supraglottic edema; immediate bedside wound opening and clot evacuation must precede any endotracheal intubation attempt.
Unexplained persistent tachycardia is the earliest and most sensitive indicator of gastrointestinal anastomotic leak, requiring urgent evaluation with water-soluble contrast CT and prompt surgical or percutaneous intervention before overwhelming sepsis develops.
Extremity compartment syndrome presents with pain out of proportion to exam and pain with passive stretch; a delta pressure (diastolic blood pressure minus compartment pressure) < 30 mmHg mandates immediate removal of constrictive dressings and emergent surgical fasciotomy within 6 hours to prevent irreversible neuromuscular necrosis.
Malignant hyperthermia is an autosomal dominant skeletal muscle channelopathy (RYR1 mutation) triggered by volatile anesthetics or succinylcholine; immediate therapy requires stopping triggers, hyperventilating with 100% O2, infusing IV dantrolene (2.5 mg/kg bolus), and treating hyperkalemia, while calcium channel blockers are strictly contraindicated.
Last updated: October 2026
Perioperative Risk Stratification and Hemodynamic Optimization
Optimizing the high-risk surgical patient in the intensive care unit requires a systematic approach to preoperative risk estimation, dynamic physiological monitoring, and aggressive mitigation of systemic organ failure.
Perioperative Cardiovascular Risk Indices
Revised Cardiac Risk Index (RCRI / Lee Criteria) :
The RCRI remains the most widely utilized validated risk assessment tool for non-cardiac surgery. It assigns 1 point to each of six independent predictors of Major Adverse Cardiac Events (MACE: myocardial infarction, pulmonary edema, ventricular fibrillation or cardiac arrest, complete heart block, or death):
High-Risk Surgery : Intraperitoneal, intrathoracic, or suprainguinal vascular procedures
History of Ischemic Heart Disease : Prior myocardial infarction, positive stress test, active angina, use of sublingual nitroglycerin, or pathological Q waves on ECG
History of Congestive Heart Failure : Prior heart failure decompensation, pulmonary edema, paroxysmal nocturnal dyspnea, S3 gallop, or bilateral rales
- History of Cerebrovascular Disease : Prior stroke or transient ischemic attack (TIA)
- Preoperative Treatment with Insulin : Insulin-dependent diabetes mellitus
Preoperative Renal Dysfunction : Serum creatinine > 2.0 mg/dL > 2.0\text{ mg/dL} > 2.0 mg/dL ( > 177 μ mol/L > 177\,\mu\text{mol/L} > 177 μ mol/L )
MACE Risk Stratification :
- Class I (0 points) : 0.4 % 0.4\% 0.4% risk
- Class II (1 point) : 0.9 % 0.9\% 0.9% risk
- Class III (2 points) : 6.6 % 6.6\% 6.6% risk
- Class IV ( ≥ 3 \ge 3 ≥ 3 points) : ≥ 11.0 % \ge 11.0\% ≥ 11.0% risk
ACS NSQIP Surgical Risk Calculator : A multivariable, procedure-specific tool developed by the American College of Surgeons evaluating 21 patient-specific comorbidities to estimate 30-day complications, pneumonia, surgical site infection, and mortality.
Functional Capacity Assessment : Evaluated in Metabolic Equivalents of Task (METs). An inability to achieve 4 METs 4\text{ METs} 4 METs of functional exercise (e.g., climbing two flights of stairs, walking up a brisk hill, or carrying groceries) identifies poor cardiopulmonary reserve and predicts higher postoperative morbidity.
Goal-Directed Hemodynamic Therapy (GDHT)
Goal-directed hemodynamic therapy utilizes flow-based dynamic parameters rather than static pressures (such as CVP) to optimize tissue oxygen delivery. In mechanically ventilated patients without cardiac arrhythmias, cyclic positive-pressure ventilation induces predictable changes in right and left ventricular preload:
Stroke Volume Variation (SVV) and Pulse Pressure Variation (PPV) : An SVV > 12 % to 13 % \text{SVV} > 12\%\text{ to }13\% SVV > 12% to 13% or PPV > 13 % \text{PPV} > 13\% PPV > 13% indicates that the patient's heart is operating on the ascending limb of the Frank-Starling curve and will augment cardiac output in response to fluid administration.
Incorporating dynamic GDHT protocols to titrate crystalloid boluses, inotropic agents (dobutamine), and vasopressors (norepinephrine) significantly reduces postoperative acute kidney injury, surgical site infections, and intensive care length of stay.
- Critical Postoperative Surgical Emergencies
- 1. Expanding Postoperative Neck Hematoma
Postoperative neck hematoma is a catastrophic emergency seen after thyroidectomy , parathyroidectomy , carotid endarterectomy (CEA) , or anterior cervical discectomy and fusion (ACDF) .
Pathophysiology : Arterial or venous bleeding rapidly accumulates within the deep cervical fascial compartments (bounded by the rigid pretracheal and investing deep cervical fascia). The high tissue pressure compresses the thin-walled internal jugular veins and laryngeal venous drainage networks, triggering rapid, severe supraglottic and glottic mucosal edema . Secondarily, tension directly collapses the anterior tracheal cartilage.
Clinical Presentation : Tense, expanding cervical swelling, localized neck pain, dysphonia ("muffled voice"), tachypnea, inspiratory stridor, and respiratory arrest.
Warning
Immediate Bedside Decompression is Mandatory : Do NOT delay for airway equipment, operating room transport, or video laryngoscopy attempts. Supraglottic and glottic mucosal edema rapidly distorts anatomical landmarks, rendering intubation and mask ventilation impossible. Cutting skin sutures and opening the deep investing fascia at the bedside instantly relieves venous hypertension and tracheal compression, restoring airway patency before securing a definitive airway.
2. Gastrointestinal Anastomotic Leak
Anastomotic dehiscence is a feared complication following esophagectomy, gastrectomy, bariatric bypass, and colorectal resection. It classically manifests between postoperative days 5 and 7 , though it may present earlier.
Earliest Clinical Sign : Unexplained, persistent sinus tachycardia ( > 100 bpm > 100\text{ bpm} > 100 bpm ) is the earliest and most sensitive sign of an anastomotic leak, frequently preceding fever, localized pain, or leukocytosis by 24 to 48 hours.
Progression : Low-grade fever, tachypnea, progressive oliguria, new-onset atrial fibrillation, abdominal distension, localized peritonitis, or purulent/enteric output from surgical drains.
Diagnostic Modality : Abdominal and pelvic computed tomography (CT) with oral water-soluble contrast (e.g., Gastrografin or dilute non-ionic contrast) and intravenous contrast. Barium sulfate is strictly contraindicated ; extravasation of barium into the peritoneal cavity causes catastrophic, irreversible chemical peritonitis and foreign-body granulomatosis.
Management : Immediate broad-spectrum intravenous antibiotics covering enteric gram-negative rods and anaerobes, aggressive crystalloid resuscitation, and urgent surgical re-exploration or CT-guided percutaneous drainage depending on clinical stability and the presence of generalized peritonitis.
3. Extremity Compartment Syndrome
Compartment syndrome develops when elevated interstitial tissue pressure within an inelastic, closed osteofascial muscle compartment compromises microvascular capillary perfusion, causing ischemia and necrosis.
Common Etiologies : Long-bone fractures (tibial shaft [most common], forearm), crush injuries, prolonged surgical lithotomy positioning ("well-leg compartment syndrome"), reperfusion injury following acute arterial embolectomy, circumferential limb burns, and pressurized IV extravasation.
Clinical Presentation: The 6 P's :
Pain Out of Proportion to Exam : Pain that is severe, progressive, and markedly exacerbated by passive stretch of the muscle groups within the compartment (the earliest and most sensitive sign).
Paresthesias : Sensory deficit in the distribution of traversing peripheral nerves (early ischemic sign; e.g., numbness in the first webspace from deep peroneal nerve ischemia in the anterior tibial compartment).
Pallor : Pale, cool extremity (late sign).
Poikilothermia : Inability to regulate limb temperature (late sign).
Paralysis : Loss of active motor function (indicates muscle infarction; late sign).
Pulselessness : Absence of distal arterial pulses ( a very late and ominous finding ; systolic pressure usually exceeds compartment pressure, so palpable pulses are preserved despite lethal tissue ischemia).
Diagnostic Criteria :
In obtunded or intubated patients, direct compartment needle manometry (Stryker device) is required.
Delta Pressure ( Δ P \Delta P Δ P ) : Diastolic Blood Pressure minus Intracompartmental Pressure. Δ P = Diastolic BP − Compartment Pressure \Delta P = \text{Diastolic BP} - \text{Compartment Pressure} Δ P = Diastolic BP − Compartment Pressure
A Δ P < 30 mmHg \Delta P < 30\text{ mmHg} Δ P < 30 mmHg (or absolute compartment pressure > 30 mmHg > 30\text{ mmHg} > 30 mmHg ) is diagnostic of compartment syndrome and mandates emergency intervention.
Management : Immediately cut and remove all circumferential casts, splints, and dressings to the skin (releases up to 85% of external constriction). If Δ P \Delta P Δ P remains < 30 mmHg < 30\text{ mmHg} < 30 mmHg or clinical signs persist, emergent surgical multi-compartment fasciotomy must be performed without delay. Delay beyond 6 hours causes permanent contracture (Volkmann's ischemic contracture), nerve death, and myoglobinuric renal failure.
Postoperative Emergency High-Risk Procedures Earliest / Most Sensitive Indicator Diagnostic Threshold / Pitfall Immediate Life-Saving Action
Postoperative Neck Hematoma Thyroidectomy, parathyroidectomy, CEA, ACDF Progressive cervical tightness, muffled voice, stridor Intubation attempt before opening fascia causes fatal airway loss Immediate bedside clip removal, deep fascial opening & clot evacuation
Anastomotic Leak Colorectal resection, gastric bypass, esophagectomy Unexplained persistent sinus tachycardia ( > 100 bpm > 100\text{ bpm} > 100 bpm ) Barium contrast strictly contraindicated; use water-soluble oral contrast IV broad-spectrum antibiotics, fluid resuscitation, surgical re-exploration / percutaneous drain
Extremity Compartment Syndrome Tibial fractures, prolonged lithotomy, arterial reperfusion Pain out of proportion & severe pain on passive muscle stretch Palpable distal pulses do NOT rule out compartment syndrome Remove all dressings; emergent surgical fasciotomy if Δ P < 30 mmHg \Delta P < 30\text{ mmHg} Δ P < 30 mmHg
Malignant Hyperthermia General anesthesia with volatile gases or succinylcholine Unexplained rapid elevation of EtCO 2 \text{EtCO}_2 EtCO 2 & masseter spasm Temperature spike is a late manifestation; do NOT give CCBs Discontinue triggers, 100% O 2 \text{O}_2 O 2 , IV Dantrolene ( 2.5 mg/kg 2.5\text{ mg/kg} 2.5 mg/kg ), treat K + \text{K}^+ K +
Malignant Hyperthermia: Pathophysiology and Crisis Protocol
Malignant Hyperthermia (MH) is a life-threatening, autosomal dominant pharmacogenetic hypermetabolic skeletal muscle crisis.
Pathophysiology and Genetics
MH is predominantly associated with gain-of-function missense mutations in the ryanodine receptor type 1 gene ( RYR1 ) on chromosome 19q13 (accounting for > 70 % > 70\% > 70% of cases), or less commonly the voltage-gated calcium channel subunit gene ( CACNA1S ). The ryanodine receptor is the principal calcium release channel of the skeletal muscle sarcoplasmic reticulum (SR).
Triggers : Exposure to volatile inhalational anesthetics (sevoflurane, desflurane, isoflurane, halothane) or the depolarizing neuromuscular blocker succinylcholine .
Cascade : In susceptible individuals, exposure triggers uncontrolled, sustained efflux of calcium from the SR into the myoplasm. Intracellular calcium hyper-activates actin-myosin cross-linking and stimulates glycogenolysis and aerobic/anaerobic metabolism. The skeletal muscle consumes vast amounts of ATP and oxygen, generating tremendous heat, lactic acid, and carbon dioxide.
Clinical Manifestations
Earliest Sign : Unexplained, rapid increase in End-Tidal Carbon Dioxide ( EtCO 2 \text{EtCO}_2 EtCO 2 ) that is refractory to doubling or tripling minute ventilation on the mechanical ventilator.
Masseter Muscle Rigidity (MMR) : Jaws clamped tightly shut following succinylcholine administration, preventing laryngoscopy.
Sympathetic Hyperactivity : Sinus tachycardia, tachypnea, labile blood pressure, and peaked T-waves from acute hyperkalemia.
Generalized Rigidity : "Wooden" abdominal wall and generalized skeletal muscle contracture.
Late Sign : Rapidly escalating core hyperthermia ( > 41 ∘ C to 42 ∘ C > 41^\circ\text{C}\text{ to }42^\circ\text{C} > 4 1 ∘ C to 4 2 ∘ C ) , rising as fast as 1 ∘ C 1^\circ\text{C} 1 ∘ C every 5 minutes.
Laboratory Profile : Mixed respiratory and metabolic acidosis (arterial pH < 7.15 \text{pH} < 7.15 pH < 7.15 ), severe hyperkalemia ( > 6.5 mEq/L > 6.5\text{ mEq/L} > 6.5 mEq/L ), serum creatine kinase (CK) elevation ( > 20 , 000 to 100 , 000 U/L > 20,000\text{ to }100,000\text{ U/L} > 20 , 000 to 100 , 000 U/L ), hypermyoglobinuria, and DIC.
Step-by-Step Emergency Management Protocol
Cease Triggering Agents : Immediately shut off volatile anesthetics. Switch to non-triggering total intravenous anesthesia (TIVA with propofol, opioids, and non-depolarizing neuromuscular blockers). Do not stop the surgical procedure if life-saving, but complete it expeditiously.
Hyperventilate with 100% Oxygen : Ventilate with 100 % O 2 100\%\text{ O}_2 100% O 2 at high fresh gas flows ( ≥ 10 to 12 L/min \ge 10\text{ to }12\text{ L/min} ≥ 10 to 12 L/min ) using activated charcoal vapor filters placed on the inspiratory and expiratory limbs to wash out volatile gases.
Administer Dantrolene Sodium :
Dose : 2.5 mg/kg 2.5\text{ mg/kg} 2.5 mg/kg rapid IV push , repeated every 5 to 10 minutes until hypercarbia, tachycardia, and rigidity resolve (cumulative dose often 2.5 to 10 mg/kg 2.5\text{ to }10\text{ mg/kg} 2.5 to 10 mg/kg , up to 30 mg/kg 30\text{ mg/kg} 30 mg/kg ). Once stabilized, continue maintenance dantrolene at 1 mg/kg 1\text{ mg/kg} 1 mg/kg IV every 4 to 6 hours for 24 to 48 hours.
Formulations : Modern Ryanodex formulation contains 250 mg/vial 250\text{ mg/vial} 250 mg/vial and dissolves in 5 mL 5\text{ mL} 5 mL of sterile water within 20 seconds. Traditional formulations (Dantrium / Revonto) contain only 20 mg/vial 20\text{ mg/vial} 20 mg/vial and require 60 mL 60\text{ mL} 60 mL of sterile water per vial (requiring reconstitution of 10 to 15 vials for an adult dose).
Mechanism : Dantrolene directly binds to the ryanodine receptor (RYR1), blocking calcium release from the sarcoplasmic reticulum into the myoplasm and halting the hypermetabolic engine.
Treat Hyperkalemia Aggressively : Administer IV calcium chloride ( 1 g 1\text{ g} 1 g central), regular insulin (10 units) with 50 mL 50\text{ mL} 50 mL 50% dextrose, and sodium bicarbonate ( 1 to 2 mEq/kg 1\text{ to }2\text{ mEq/kg} 1 to 2 mEq/kg ).
Caution
Absolute Contraindication in Malignant Hyperthermia : Calcium channel blockers (such as diltiazem and verapamil) must never be administered to treat tachycardia or arrhythmias in suspected malignant hyperthermia. Co-administration of calcium channel blockers with dantrolene causes severe hyperkalemia, myocardial depression, and fatal cardiovascular collapse.
Active Core Cooling : Infuse cold 4 ∘ C 4^\circ\text{C} 4 ∘ C normal saline, place surface ice packs in the axillae and groin, and perform cold nasogastric or bladder lavage. Halt active cooling when core temperature falls to < 38.5 ∘ C < 38.5^\circ\text{C} < 38. 5 ∘ C to prevent hypothermic undershoot.
Promote Renal Protection : Infuse fluids to maintain urine output > 2 mL/kg/h > 2\text{ mL/kg/h} > 2 mL/kg/h , adding mannitol or furosemide and alkalinizing the urine with bicarbonate to prevent intratubular myoglobin cast precipitation.
- Post-Cardiac Surgery Critical Care
- 1. Vasoplegic Syndrome
Vasoplegic syndrome is a severe form of distributive shock occurring in up to 10% of patients following cardiopulmonary bypass (CPB).
Diagnostic Criteria : Profound arterial hypotension (MAP < 50 to 60 mmHg < 50\text{ to }60\text{ mmHg} < 50 to 60 mmHg ) accompanied by a low Systemic Vascular Resistance Index ( SVRI < 1600 dyn ⋅ s ⋅ cm − 5 ⋅ m 2 \text{SVRI} < 1600\text{ dyn}\cdot\text{s}\cdot\text{cm}^{-5}\cdot\text{m}^2 SVRI < 1600 dyn ⋅ s ⋅ cm − 5 ⋅ m 2 ) despite a normal or elevated Cardiac Index ( CI > 2.5 to 3.0 L/min/m 2 \text{CI} > 2.5\text{ to }3.0\text{ L/min/m}^2 CI > 2.5 to 3.0 L/min/m 2 ) and adequate ventricular filling pressures.
Pathophysiology : Contact of blood with the extracorporeal bypass circuit triggers massive systemic inflammation, activating endothelial inducible nitric oxide synthase (iNOS) and soluble guanylyl cyclase (sGC). The resulting cyclic GMP storm induces refractory vascular smooth muscle relaxation alongside relative neurohormonal vasopressin depletion.
Treatment Ladder :
First-line: Norepinephrine titrated aggressively.
Second-line: Early low-dose Vasopressin ( 0.03 to 0.06 units/min 0.03\text{ to }0.06\text{ units/min} 0.03 to 0.06 units/min ; non-titrated).
Refractory Rescue Adjuncts:
Methylene Blue : 1 to 2 mg/kg 1\text{ to }2\text{ mg/kg} 1 to 2 mg/kg IV over 20 to 30 minutes, followed by a continuous infusion of 0.25 to 0.5 mg/kg/h 0.25\text{ to }0.5\text{ mg/kg/h} 0.25 to 0.5 mg/kg/h . Methylene blue directly inhibits soluble guanylyl cyclase and iNOS, reversing cGMP-mediated vasoplegia. (Caution: risk of serotonin syndrome in patients taking SSRIs).
Hydroxocobalamin : 5 g 5\text{ g} 5 g IV infusion over 15 minutes; acts as a direct nitric oxide scavenger.
Synthetic Human Angiotensin II (Giapreza) : Direct vasoconstrictor stimulating the AT1 receptor.
2. Localized Pericardial Tamponade
Following median sternotomy, blood and thrombi frequently accumulate in regional pericardial gutters or retrocardiac spaces rather than distributing circumferentially around the heart.
Diagnostic Pitfall : Classic signs of circumferential tamponade (Beck's triad, electrical alternans, and systemic pulsus paradoxus) are frequently ABSENT . Instead, localized clot compression typically indents a single compliant chamber—most commonly the right atrium, right ventricular outflow tract, or left atrium.
Clinical Presentation : Unexplained persistent low cardiac output, oliguria, mixed venous oxygen desaturation, and refractory hypotension requiring escalating inotropes and vasopressors in the early postoperative hours.
Note
Diagnostic Pitfall in Postoperative Tamponade : Classic systemic signs of pericardial tamponade (Beck's triad and pulsus paradoxus) are frequently absent following cardiac surgery. Bleeding typically forms localized, loculated retrocardiac or right atrial hematomas. Transesophageal echocardiography (TEE) is vastly superior to transthoracic imaging for detecting regional chamber compression and guiding prompt sternotomy re-exploration.