Critical Care Medicine - Medical School Crash Course

Critical Care Medicine

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TABLE OF CONTENTS: Quick Overview .................................................................................. 1 Introduction ...................................................................................... 2 Chapter 1: Introduction to Critical Care ..............................................7 Approach to the unstable patient ..........................................................................7 Shock .................................................................................................................... 8 Adult Resuscitation .............................................................................................10 Pediatric Resuscitation........................................................................................ 11 Key Takeaways .................................................................................................... 13 Review Questions ................................................................................................ 14 Chapter 2: Acid Base Disorders ........................................................ 16 Acidosis ................................................................................................................ 16 Alkalosis ............................................................................................................... 17 Key Takeaways .................................................................................................... 19 Review Questions ............................................................................................... 20 Chapter 3: Pulmonary ..................................................................... 23 Asthma & COPD ................................................................................................. 23 Pneumonia.......................................................................................................... 25 Pleural Effusions .................................................................................................27 Acute Respiratory Distress Syndrome- ARDS ................................................... 29 Aspiration ........................................................................................................... 29 Pulmonary Embolism......................................................................................... 30 Ventilator Management ...................................................................................... 31

Key Takeaways ................................................................................................... 35 Review Questions ................................................................................................37 Chapter 4: Cardiovascular Diseases ................................................. 40 Myocardial Infarction......................................................................................... 40 Arrhythmias........................................................................................................ 43 Ventricular Arrhythmias .................................................................................... 44 Bradycardia ........................................................................................................ 45 Long QT Syndrome ............................................................................................ 46 Congestive Heart Failure.....................................................................................47 Aortic Dissection .................................................................................................47 Abdominal Aortic Aneurysm.............................................................................. 48 Key Takeaways ................................................................................................... 50 Review Questions ............................................................................................... 52 Chapter 5: Nephrology & Electrolyte Disorders ................................55 Acute Renal Failure .............................................................................................55 Potassium ........................................................................................................... 56 Calcium ................................................................................................................ 57 Sodium ................................................................................................................ 58 Rhabdomyolysis ................................................................................................. 58 Hemodialysis ...................................................................................................... 59 Key Takeaways ................................................................................................... 62 Review Questions ............................................................................................... 63 Chapter 6: Gastrointestinal Disorders ............................................. 65 Diarrhea .............................................................................................................. 65

Gastrointestinal Bleeding ................................................................................... 66 Mesenteric Ischemia ...........................................................................................67 Pancreatitis ......................................................................................................... 68 Key Takeaways ................................................................................................... 69 Review Questions ............................................................................................... 70 Chapter 7: Neurology ........................................................................ 73 Delirium ...............................................................................................................73 Transient Ischemic Attack ..................................................................................74 Ischemic Stroke ................................................................................................... 75 Intracranial Hemorrhage ................................................................................... 78 Guillain Barré Syndrome.................................................................................... 80 Status Epilepticus ............................................................................................... 80 Key Takeaways ................................................................................................... 82 Review Questions ............................................................................................... 84 Chapter 8: Endocrine Disorders ...................................................... 87 Diabetic Ketoacidosis ......................................................................................... 87 Blood Sugar Disorders ....................................................................................... 89 Thyroid Disorders ............................................................................................... 91 Thyroid Storm ..................................................................................................... 91 Myxedema Coma ................................................................................................ 92 Adrenal Crisis ..................................................................................................... 93 Pheochromocytoma ............................................................................................ 94 Key Takeaways ................................................................................................... 95 Review Questions ............................................................................................... 96

Chapter 9: Infectious Diseases......................................................... 99 Sepsis .................................................................................................................. 99 Septic Shock...................................................................................................... 100 Nosocomial Infections....................................................................................... 101 Malaria ............................................................................................................... 105 Endocarditis ......................................................................................................106 Meningitis .......................................................................................................... 107 Necrotizing Fasciitis ......................................................................................... 108 Fever and Neutropenia......................................................................................109 Key Takeaways ................................................................................................... 111 Review Questions .............................................................................................. 113 Chapter 10: Toxicology ....................................................................117 Alcohol ............................................................................................................... 119 Acetaminophen ................................................................................................. 121 Aspirin ............................................................................................................... 123 Benzodiazepines ................................................................................................ 123 Beta Blockers and Calcium Channel Blockers .................................................. 124 Organophosphates ............................................................................................ 124 Anticholinergic Poisoning ................................................................................. 125 Cocaine .............................................................................................................. 125 Opiates ............................................................................................................... 126 Key Takeaways .................................................................................................. 127 Review Questions .............................................................................................. 129 Chapter 11: Trauma ........................................................................ 132

Head injuries ..................................................................................................... 133 Neck Injuries ..................................................................................................... 136 Spine Injuries .................................................................................................... 137 Chest Injuries ....................................................................................................138 Abdominal Injuries ...........................................................................................140 Extremity Injuries ............................................................................................. 141 Burns ................................................................................................................. 142 Drowning ........................................................................................................... 143 Key Takeaways .................................................................................................. 145 Review Questions .............................................................................................. 146 Chapter 12: Nutrition in the ICU ..................................................... 149 Enteral Nutrition ............................................................................................... 149 Parenteral Nutrition .......................................................................................... 151 Key Takeaways .................................................................................................. 153 Review Questions .............................................................................................. 154 Chapter 13: Special Topics in Critical Care Medicine....................... 157 Accidental Hypothermia ................................................................................... 157 Therapeutic Hypothermia ................................................................................. 158 Tumor Lysis Syndrome ..................................................................................... 159 Transfusion Therapy and Adverse Reactions ...................................................160 Toxic Shock Syndrome ...................................................................................... 161 Shock Liver ........................................................................................................ 162 Serotonin Syndrome.......................................................................................... 162 Neuroleptic Malignant Syndrome ..................................................................... 163

Preeclampsia ..................................................................................................... 164 Eclampsia .......................................................................................................... 165 HELLP Syndrome ............................................................................................. 166 Key Takeaways .................................................................................................. 167 Review Questions .............................................................................................. 169 Summary........................................................................................ 172 Final Test ....................................................................................... 175 Answers to Questions ..................................................................... 199 Chapter 1. ........................................................................................................... 199 Chapter 2. ..........................................................................................................201 Chapter 3. ......................................................................................................... 202 Chapter 4. ......................................................................................................... 204 Chapter 5. ......................................................................................................... 206 Chapter 6. ......................................................................................................... 208 Chapter 7. ..........................................................................................................210 Chapter 8. .......................................................................................................... 212 Chapter 9. .......................................................................................................... 214 Chapter 10. ........................................................................................................ 216 Chapter 11. .........................................................................................................218 Chapter 12. ........................................................................................................ 220 Chapter 13. ........................................................................................................ 222 Final Test .......................................................................................................... 224

QUICK OVERVIEW This course provides an overview of critical care medicine. Critical care specialists treat the sickest patients in the hospital who are admitted to intensive care units, or ICUs. These patients suffer from severe medical illnesses, injuries, or surgical complications. Critical care specialists are routinely called upon to perform invasive but life saving procedures. This course discusses a general approach to evaluating and treating these critically ill patients. It also reviews diseases associated with the various organ systems that are important to the practice of critical care medicine. Specific organ systems covered are pulmonary, cardiovascular, renal, gastrointestinal, neurological, and endocrine. Additionally, special topics like acid-base disorders, toxicology, traumatic injuries, and nutrition are discussed.

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INTRODUCTION Critical care medicine is a medical subspecialty focused on treating patients with life-threatening illnesses and injuries. These patients are treated in special critical care units of the hospital, commonly referred to as intensive care units or ICUs. They often require mechanical and pharmacologic support to maintain organ system functions and close hemodynamic monitoring of their vital signs. ICUs have a low staff to patient ratio, allowing for close monitoring, complicated therapies, and quick intervention when required. Patients are transferred to these ICUs after initial stabilization in the emergency department, following surgeries, or from the hospital wards if their condition worsens. ICUs include the medical intensive care unit or MICU, the coronary intensive care unit or CCU, the neuroscience critical care unit or NCCU, the pediatric intensive care unit or PICU, the neonatal intensive care unit or NICU, and the surgical intensive care unit or SICU. Post operative recovery units are also considered critical care units since patients here are emerging from anesthesia and are at risk for a variety of post operative complications. Emergency departments also routinely care for these critical patients. In the emergency department, care is supervised by emergency physicians often with the support and assistance of the critical care specialists who will take over care when the patient is transferred to the ICU. Critical care specialists working in an ICU perform a variety of life-saving procedures including intubation and ventilator management, central venous catheterization, thoracostomy or chest-tube placement, and resuscitation during cardiopulmonary arrest. The most common pathway to becoming a critical care specialist is to complete a three-year internal medicine residency followed by a pulmonary and critical care medicine fellowship. Critical care fellowships may also be undertaken following a pediatric, surgical, emergency medicine, or anesthesiology residency. Some ICUs are staffed by anesthesiologists who have not completed an additional fellowship in critical care medicine.

The first recognized intensive care unit was developed in 1952 in response to a 2

massive polio outbreak in Denmark. Faced with hundreds of patients suffering from respiratory muscle paralysis, Danish anesthesiologist Dr. Bjorn Ibsen enlisted a small army of over fifteen hundred medical students working in shifts to manually ventilate patients who had tubes placed down their trachea to maintain their airways. His efforts reduced mortality for these patients from eighty seven percent to less than fifteen percent. He later established a specialized intensive therapy unit at the Municipal Hospital of Copenhagen and developed protocols to treat other diseases requiring intensive monitoring and therapy, including tetanus, in a critical care setting. Since then, the concept of intensive care units staffed by critical care specialists has grown to become its own specialty and key resource in caring for a hospital’s sickest patients. The specialty and practice has evolved alongside cutting edge monitoring technologies and the availability of new medications that can be utilized to stabilize and maintain organ system functions.

According to a study published by the Society of Critical Care Medicine, an estimated six million patients a year are cared for in intensive care units in the United States. Common conditions in adult ICU patients include cardiac, neurologic, respiratory, and infectious diseases. Respiratory diseases are the most common admission diagnosis in pediatric ICU’s. There are an estimated five thousand seven hundred adult ICU’s and more than four hundred pediatric ICU’s in the United States Critical care units today are equipped with a variety of technologies including mechanical ventilators, cardiac telemetry monitors, and a variety of invasive monitoring approaches that often use catheters in veins and arteries to monitor blood pressure and other cardiac functions. The care approach is interdisciplinary with a low staff to patient ratio. In addition to the critical care physician at the helm, specially trained nurses, consulting physicians from other specialties, physician assistants, nurse practitioners, respiratory therapists, technicians, pharmacists, and nutritionists work together to care for and manage intensive care unit patients.

These health providers often have to deal with a variety of ethical dilemmas 3

related to patients in critical care settings. These ethical issues often pertain to end of life care, determination of brain death, withdrawal of medical support to sustain life, and advanced directives related to patients’ desire for cardiopulmonary resuscitation. These issues are complicated in the absence of formal advanced directives from the patient, especially in scenarios where family members disagree on the level of care to be provided. The approach of intensive care unit staff is often criticized as being too intensive, and may border on medical futility if patient life is prolonged without additional quality or hope of recovery, but at great financial and manpower expense.

This course provides an overview of the specialty of critical care medicine. It provides a general approach to evaluating and treating critically ill patients. It also reviews specific diseases associated with the various organ systems that are important to the practice of critical care medicine.

Chapter one provides an introduction to critical care and includes discussions on unstable patients, shock, and resuscitation in general. The general approaches to critically ill patients presented in this chapter are applicable both to the intensive care unit and to other care settings when treating patients.

Chapter two presents acid-base disorders relevant to critical care medicine including metabolic and respiratory acidosis and metabolic and respiratory alkalosis. Acid base disorders are common complications of a variety of illnesses affecting nearly every possible organ system, so it is important to consider these disorders when evaluating and treating all patients with critical illnesses.

Chapter three discusses pulmonary diseases including asthma, pneumonia, acute respiratory distress syndrome, and pulmonary embolisms. The chapter also outlines ventilator management guidelines and commonly used settings. Severe pulmonary disease is a common scenario treated in the intensive care unit.

Chapter four covers cardiovascular diseases managed in the intensive care unit.

These include myocardial infarctions, commonly referred to as heart attacks, arrhythmias or irregular heartbeats, congested heart failure or CHF, and aortic dissections. Given the relative instability of cardiac patients, many severe cardiac

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illnesses must be evaluated and treated in a critical care setting.

Chapter five discusses nephrology and the electrolyte disorders that are usually related to kidney dysfunction. Specific topics include acute renal failure, elevated or low potassium, and calcium and sodium abnormalities. The chapter also discusses rhabdomyolysis, which is a consequence of muscle breakdown. Muscle breakdown byproducts can subsequently cause damage to the kidneys.

Indications for hemodialysis in critical care patients will also be discussed.

Chapter six presents information on gastrointestinal disorders including diarrhea, gastrointestinal bleeding, and pancreatitis. The gastrointestinal system regulates digestion and several other bodily functions and is relevant to critical care patients both in terms of primary diagnoses and complications of critical care therapy.

Chapter seven discusses neurology related to critical care patients. Relevant neurologic diseases include ischemic stroke, intra-cerebral hemorrhages, and status epilepticus, also known as uncontrolled seizures.

Endocrine disorders related to critical care patients are discussed in Chapter eight. Topics include diabetic ketoacidosis, other blood sugar disorders, adrenal crisis, pheochromocytoma, and thyroid diseases.

Chapter nine presents a discussion on infectious diseases in the ICU. Topics include sepsis and septic shock, meningitis, necrotizing fasciitis, nosocomial infections, and fever associated with neutropenia.

Chapter ten provides information on toxicology and poisoned patients. Toxins discussed in this chapter include alcohol, acetaminophen, aspirin, Beta-blockers, calcium channel blockers, cocaine, and opiates.

Chapter eleven presents the topic of traumatic injuries. Key injuries discussed in this chapter include head injuries, neck and spinal injuries, chest injuries, abdominal injuries, extremity injuries, drowning, and burns.

Chapter twelve provides an overview of nutrition related to intensive care unit patients. This chapter discusses both enteral and parenteral nutrition approaches.

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Finally, Chapter thirteen presents special topics in critical care medicine not covered in the previous chapters. These include therapeutic hypothermia and tumor lysis syndrome.

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CHAPTER 1: INTRODUCTION TO CRITICAL CARE In this chapter we will discuss three key themes related to critical care medicine including the general approach to unstable patients, diagnosis and treatment of shock, and resuscitation of adult and pediatric patients.

APPROACH TO THE UNSTABLE PATIENT This first section will discuss an approach to the unstable patients. When evaluating and treating critically ill and injured patients, it is helpful to follow the algorithm of airway, breathing, circulation, and disability prior to diagnosing and addressing specific disease pathologies. The algorithm is ordered as such in order to focus clinician efforts on the most life-threatening aspects of a patient’s condition. It allows for a systematic approach that avoids distractions while preserving critical organ system functions needed for survival.

The algorithm begins by assessing the airway. The airway should be cleared of any secretions or foreign objects with suctioning and the patient should be provided with supplemental oxygen via a nasal cannula or face mask. If the patient is not breathing, oxygen and airflow must be delivered by a bag valve mask. If the patient cannot be ventilated with a bag valve mask then their airway may be obstructed buy a foreign object or soft tissue swelling. A so-called definitive airway can be established with the placement of an endotracheal tube through the trachea or a surgical airway in the neck, known as a cricothyroidotomy.

Next, breathing through the established airway is further evaluated via auscultation of breath sounds in bilateral lung fields. Absent breath sounds on one side may indicate a pneumothorax or fluid collection. Vital signs relevant to this phase of the evaluation include the respiratory rate and the pulse oximetery.

If the respiratory rate is zero, alse known as apnea, the patient will need to be intubated and placed on mechanical ventilator. If the respiratory rate is low, the 7

patient may need to be stimulated with medications or evaluated for intubation.

The respiratory rate is too high, the critical care physicians should worry about the patients tiring out and progressing to respiratory arrest. A low pulse oximetry, less than 90%, can be the result of damage to the lung tissue, infection, a low respiratory rate, or a combination of factors.

Circulation is then evaluated buy checking a patient’s blood pressure, peripheral pulse, and peripheral capillary refill. A pulse-less patient requires immediate chest compressions. Patients with a low blood pressure or delayed capillary refill may require intravenous fluids or pharmacologic vasopressors. Commonly used vasopressors include intravenous dopamine and intravenous norepinephrine.

Vital signs monitored during this phase of evaluation include the pulse and blood pressure. Additionally, a patient’s capillary refill can be evaluated. Elevated blood pressure, or hypertension, can cause damage to the brain, kidneys, and heart.

Low blood pressure can cause hypoperfusion of peripheral organs and lead to tissue damage. Similarly, both a fast heart rate and a slow heart rate can be dangerous for a patient and cause organ damage or failure.

Complete the evaluation by evaluating a patient’s disability. The evaluation and treatment of disability includes evaluation for injuries, neurological deficits, and hypothermia (low temperature) or hyperthermia (high temperature). In addition to checking the patient’s temperature, they should be completely undressed to look for wounds, infections, or foreign bodies. A complete neurological exam should be performed. The neurological exam should include an evaluation of the patient’s level of alertness, movement in all extremities, mental status, and pupils.

SHOCK This section will discuss the concept of shock. Shock is a life-threatening condition whereby circulation is inadequate to ensure blood flow to peripheral organs. All types of shock are characterized by low blood pressure which leads to hypoperfusion. This results in end organ damage and the buildup of waste

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products like lactic acid in the bloodstream. Shock requires immediate recognition and rapid treatment, otherwise it can be fatal.

Hypovolemic shock is caused by low body levels of blood or fluid. It can be caused by severe dehydration or blood loss associated with injuries for gastrointestinal bleeding. Treatment of hypovolemic shock depends on fluid resuscitation and the administration of blood products if needed. In patients who are actively bleeding, the source of the bleeding must also be found and dealt with to treat the patient’s underlying condition.

Anaphylactic shock occurs as a result of exposure to allergens including foods, medications, and insect bites or stings. Common signs and symptoms include redness, rash, swelling, and dizziness. Treatment includes removal of exposure to the offending agent and intramuscular epinephrine, also known as adrenaline.

Additional treatments include diphenhydramine, intravenous fluids, and steroids. Anaphylactic shock is a medical emergency is can lead to death if not treated rapidly. In the United States alone up to one thousand people die per year from an anaphylactic reaction. Prevention efforts include providing susceptible patients epinephrine auto injectors and proper food labeling to avoid inadvertent exposures.

Cardiogenic shock occurs when the heart is unable to pump blood to peripheral organs. It is commonly associated with weakened cardiac muscles. This often occurs as a result of heart attacks or irregular heart rhythms known as arrhythmias. Treatment for cardiogenic shock includes intravenous fluids to increase the preload, or fuel in the tank, and vasopressor medications to stimulate the heart and contract peripheral blood vessels. Medications can also be provided to reverse arrhythmia when present.

Neurogenic shock occurs as a result of injuries to the spinal cord or brain. It is caused by a disruption in the autonomic nervous system’s regulation of the heart and peripheral blood vessels. This results in a decreased heart rate and dilation of peripheral blood vessels, which together result in low blood pressure and poor perfusion or peripheral organs.

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Septic shock occurs as a result of severe, life-threatening infections. It can be a result of an infection with a bacteria, virus, or fungus. It can affect anyone at any age, but more commonly affects the very young, the very old, and patients with a compromised immune system. Survival depends on early recognition of the condition and aggressive treatment with intravenous fluids and antibiotics.

An approach to septic shock introduced by Dr. Emmanuel Rivers in 2001, known as early goal directed therapy, presents a screening and treatment protocol that is now commonly used. It screens for patients with hypotension, a suspected infection, and a serum lactate level greater than four. These patients are initially treated with an aggressive intravenous fluid bolus and broad spectrum antibiotics. If after this bolus the patient is persistently hypotensive or if the lactate is still greater than four, then a central line is placed with central venous pressure monitoring initiated. Fluids are infused until the CVP reads between eight and twelve mm of Hg. Vasopressors are initiated to maintain blood pressure and improve perfusion. While some recent studies have questioned the value of the entire package of early goal directed therapy, the lessons imparted related to screening and aggressive initial therapy have made a concrete impact on improving sepsis care around the world.

ADULT RESUSCITATION Adult resuscitation follows the principles and protocols outlined by the ACLS guideline, known as advanced cardiac life support. This guideline outlines a sequence of algorithms to treat cardiac arrest, bradycardia, tachycardia, stroke, and other critical presentations. The protocol discusses chest compressions, oxygen ventilation, cardioactive medications like epinephrine, and the use of a manual electrical defibrillator. Unlike the basic life support, or BLS course, which is open to all types of students including members of the public, ACLS is only available to health providers. These include physicians, pharmacists, nurses, dentists, respiratory therapists, paramedics, physician assistants, and nurse practitioners. The ACLS course requires that students are able and qualified to intubate patients, start intravenous lines, read an electrocardiogram, and 10

administer emergency resuscitation medications. The BLS course focuses only on chest compressions, basic airway interventions, and the use of an automatic external defibrillator. The ACLS course was first launched in 1974 and have been updated in 1980, 1986, 1992, 2000, 2005, 2010, and most recently 2015.

Pulseless patients require immediate initiation of chest compressions. The ACLS protocol outlines when and how often to give epinephrine and when to check the monitor for a shockable rhythm. If a pulseless patient has ventricular tachycardia or ventricular fibrillation, they should be defibrillated, or shocked, to increase their chances of converting to a normal cardiac rhythm that can sustain life.

Adult patients who are severely dehydrated or volume depleted should be resuscitated with isotonic intravenous fluids like normal saline. The usual resuscitation fluid bolus dose is twenty to thirty milliliters per kilogram. Patients who are anemic or who have suffered blood loss from injuries should also be resuscitated with appropriate blood products including packed red blood cells.

While moving through the ACLS algorithm for a cardiac arrest patient, it is also important to check for the so called “H’s” and “T’s” of reversible causes and to take appropriate action if one is found. The H’s include hypoglycemia, hypovolemia, hypoxia, hydrogen ions or acidosis, hyper or hypo kalemia, and hypothermia. The T’s include toxins, cardiac tamponade, tension pneumothorax, thrombosis causing a myocardial infarction, thrombo embolism, and trauma.

PEDIATRIC RESUSCITATION The resuscitation of children similarly follows the principles and protocols outlined by the PALS guideline, known as pediatric advanced life support. This guideline outlines the sequence of algorithms to treat respiratory arrest, shock, and arrhythmias that commonly present in children. The protocol discusses chest compressions, oxygen ventilation, are vaso-active medications like epinephrine and atropine, and electrical defibrillation. The key difference between PALS and ACLS is the focus on respiratory interventions in PALS since children are more likely to suffer from respiratory problems.

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Neonatal resuscitation involves the care for newborn infants over their first hours of life. This care is covered by be the NALS protocol, or neonatal advanced life support.

Dehydrated pediatric patients should be resuscitated with isotonic fluids like normal saline using a bolus dose of twenty milliliters per kilogram. Patients who are anemic or who have suffered significant blood loss should be resuscitated with appropriate blood products like packed red blood cells. Packed red blood cells can be administered using an initial dose of ten milliliters per kilogram.

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KEY TAKEAWAYS •

Critically ill and injured patients should be evaluated and treated following the algorithm of airway, breathing, circulation, and disability. Each stage of the algorithm should be completed and addressed before moving on the subsequent stage.

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Shock is a life-threatening condition associated with low blood pressure and poor perfusion of peripheral structures. It can be life threatening if not recognized and treated quickly. Different types of shock include hypovolemic, anaphylactic, cardiogenic, septic, and neurogenic.

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Adult resuscitation follows protocols outlined by the ACLS guideline. This guideline outlines a sequence of algorithms to treat cardiac arrest, bradycardia, tachycardia, stroke, and other critical presentations. The protocol discusses chest compressions, oxygen ventilation, cardioactive medications like epinephrine, and the use of a manual electrical defibrillator. Unlike the basic life support, or BLS course, which is open to all types of students including members of the public, ACLS is only available to health providers.

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Pediatric resuscitation follows protocols outlined by the PALS guideline.

This guideline outlines the sequence of algorithms to treat respiratory arrest, shock, and arrhythmias that commonly present in children. The protocol discusses chest compressions, oxygen ventilation, are vaso-active medications like epinephrine and atropine, and electrical defibrillation.

The key difference between PALS and ACLS is the focus on respiratory interventions in PALS since children are more likely to suffer from respiratory problems.

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Dehydrated and volume depleted adults and children should be resuscitated with intravenous isotonic fluids like normal saline. Anemic or bleeding patients should be resuscitated with appropriate blood products including packed red blood cells.

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