Questions and Answers
Which of the following are symptoms of right mainstem intubation?
What is the differential diagnosis (Ddx) of hypoxemia in the operating room?
Obstructed ETT, inappropriate FiO2, bronchospasm, pulmonary edema, atelectasis, pneumothorax, anaphylaxis
What are the effects of MetHb and CO on PaO2 and pulse O2 saturation when O2 is given?
MetHb causes PaO2 to increase but pulse O2 remains 85-90%; CO causes PaO2 to increase and pulse O2 to falsely rise to 100%.
What is the normal PaO2 and SaO2 of MetHb and CO?
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What are the risk factors that predict an increased likelihood of needing mechanical ventilation in myasthenia gravis patients?
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Match the types of heat loss with their descriptions:
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What is the most common etiology of hypothermia in the first hour of induction of anesthesia?
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Which conditions have increased risk for atlantoaxial instability?
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What are the mechanisms of hypothermia in the OR?
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Describe the acute and chronic effects of phenytoin on nondepolarizing NMBD.
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What does ED95 represent?
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Which of the following has the least effect on heat loss during regional or general anesthesia?
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Why do patients usually shiver with general anesthesia?
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What is an effect of muscular dystrophy from general anesthesia or succinylcholine?
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What is the best induction agent to use in a patient with intracranial hemorrhage and high ICP?
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What inhaled anesthetic inhibits DNA synthesis?
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What happens to lung volumes with aging?
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What is the trauma triad of death?
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What are the sequelae of malignant hyperthermia?
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What does high CO2 and low O2 do to the brain versus the lungs/body?
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What is the common side effect of celiac plexus block?
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What is the mechanism of venous air embolism?
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What kind of local anesthetic class is most likely to result in hypersensitivity reactions?
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Study Notes
Heat Loss Mechanisms
- Four types of heat loss in the OR: radiation, convection, conduction, and evaporation.
- Radiation is the primary cause of heat loss, involving infrared radiation transfer without contact.
- Convection occurs with air movement across the skin, while conduction involves heat loss through direct contact with colder surfaces.
- Evaporation happens during sweating, contributing to overall heat loss.
Hypothermia Etiology and Mechanisms
- Most common cause of hypothermia during the first hour of anesthesia: redistribution of body heat from core to periphery, resulting in an average drop of 1.5 degrees Celsius.
- Mechanisms of hypothermia in the OR include impaired thermoregulation due to anesthesia and low ambient temperatures.
NMBD and Phenytoin Effects
- Acutely, phenytoin enhances non-depolarizing muscle relaxants (NMBD), while chronic effects decrease the duration of the block and increase resistance to NMBD.
ED95 Definition
- Defined as the effective dose of NMBD required to reduce twitch height by 95% in 95% of the population.
Atlantoaxial Instability Risk Factors
- Conditions that increase risk include achondroplasia, Down's syndrome, rheumatoid arthritis, and systemic lupus erythematosus (SLE).
- Manual in-line stabilization or fiberoptic intubation may be necessary for patients with these conditions.
Lambert Eaton Myasthenic Syndrome
- Characterized by proximal muscular weakness that alleviates with movement, due to antibodies targeting voltage-gated calcium channels (VGCC) on presynaptic nerve terminals.
Myasthenia Gravis
- Presents with bulbar symptoms such as facial drooping, ptosis, and dysphagia that worsen with activity, caused by antibodies against acetylcholine receptors (ACh-R) on postsynaptic terminals.
Paraneoplastic Syndromes
- Squamous cell carcinoma may secrete parathyroid-related peptide, leading to hypercalcemia and associated muscular weakness.
Midazolam and Thermoregulation
- Midazolam has the least effect on heat loss compared to volatile anesthetics, opioids, and propofol, which can promote heat loss through vasodilation.
Hypothermia During General Anesthesia
- General anesthesia disrupts thermoregulation by impairing hypothalamic function, leading to patients shivering; treatment includes meperidine.
Risks of General Anesthesia in Muscular Dystrophy
- General anesthesia or succinylcholine can lead to complications such as rhabdomyolysis and cardiac arrest.
Intracranial Hemorrhage and Induction Agents
- Etomidate is the preferred induction agent for patients with intracranial hemorrhage and elevated intracranial pressure (ICP); avoid ketamine.
Core Body Temperature Measurement
- The nasopharynx provides the most accurate measurement of core body temperature.
Trauma Triad of Death
- Hypothermia, acidosis, and coagulopathy (HAC) post-massive transfusion lead to a patient being hypotensive and hypothermic, with treatment including adrenergic symptom control.
Malignant Hyperthermia (MH) Management
- Calcium channel blockers are contraindicated during dantrolene treatment for acute MH, with MH sequelae including hypermetabolic states and serious complications like arrhythmias.
Inhaled Anesthetics and DNA Synthesis
- Nitrous oxide (N2O) inhibits DNA synthesis by irreversibly inactivating vitamin B12.
Aging and Lung Function
- Aging increases residual volume and functional residual capacity while decreasing total lung capacity (TLC) and vital capacity (VC).
Rapid Bicarbonate Administration Effects
- Can lead to hypokalemia due to bicarbonate-induced alkalosis and shifts of hydrogen and potassium ions.
Becker vs. Duchenne Muscular Dystrophy
- Becker muscular dystrophy is milder with some dystrophin production, often with greater cardiac involvement compared to Duchenne muscular dystrophy.
Anesthesia Concerns in Amyotrophic Lateral Sclerosis (ALS)
- Increased risk of aspiration and pulmonary complications due to respiratory muscle weakness.
Influence of Carbon Dioxide and Oxygen on Vascular Response
- Elevated CO2 causes vasoconstriction in pulmonary vessels and vasodilation in the brain; effects reverse under hypocapnia and elevated oxygen.
Respiratory Mechanics in Pregnant Women
- Expiratory reserve volume remains unchanged, but residual volume decreases, while inspiratory capacity increases.
Upregulation of Nicotinic Acetylcholine Receptors
- Peaks at 7-10 days post spinal cord injuries, burns, or prolonged immobilization.
Local Anesthetic Hypersensitivity
- Esters (e.g., procaine) are most likely to cause hypersensitivity reactions due to PABA metabolites.
Celiac Plexus Block Effects
- Targets abdominal viscera; common side effect includes orthostatic hypotension from splanchnic vasodilation.
Venous Air Embolism
- Air entering the systemic circulation can cause serious complications such as decreased CO and cardiac arrest, with management involving 100% FiO2 and positioning.
Pediatric Fluid Management
- Recommended perioperative fluid administration is 20-40 ml/kg, with specific maintenance calculations based on weight.
Prophylactic Antibiotics in Cardiac Conditions
- Recommended in patients with prosthetic valves, history of infective endocarditis, unrepaired congenital defects, or regurgitant valvular lesions.
Management of Complex Regional Pain Syndrome (CRPS)
- Diagnostic sympathetic blocks can identify sympathetic-mediated pain, potentially leading to neurolytic therapies or spinal cord stimulators as last resorts.
Differences Between Stellate and Lumbar Sympathetic Blocks
- Both blocks target sympathetic pathways, but differ in injection sites and body regions affected.
Extrapyramidal Symptoms from Antiemetics
- Medications like metoclopramide may cause abnormal movements; treatment includes anticholinergics such as benztropine or diphenhydramine.
Monitored Anesthesia Care (MAC)
- Involves providing sedation while maintaining vital functions, with monitoring similar to general anesthesia and requiring multiple providers.
Melanoma Score Components
- The MELD score is computed using bilirubin, creatinine, sodium, and INR levels, aiding in liver disease prognosis.
Elderly and Lung Function
- With aging, closing capacity increases, leading to a greater risk for airway collapse and decreased elastic recoil in small airways.
Assessing Arterial Blood Gases in Patients
- Different patterns emerge in respiratory alkalosis, acidosis, and metabolic acidosis, each identifiable via specific pH, pCO2, and HCO3 levels.
Anticholinergic Effects of Glycopyrrolate and Atropine
- Commonly result in reduced secretions, tachycardia, and decreased motility, countering SLUDGE symptoms from excess acetylcholine.
Meralgia Paresthetica
- Arises from compression of the lateral femoral cutaneous nerve, commonly seen in pregnancy or during pelvic surgeries due to increased intra-abdominal pressure.
Venous Air Embolism Detection Sensitivity
- TEE is the most sensitive modality, followed by pericardial Doppler and pulmonary artery catheterization.
Right Mainstem Intubation Symptoms
- Results in hypoxemia and elevated airway pressures due to ventilation failure on the left side; observed as unilateral breathing difficulties.
Differential Diagnosis of Hypoxemia in the OR
- Includes obstructed endotracheal tube, bronchospasm, or pulmonary edema, with treatments like needle thoracostomy for pneumothorax.
Methemoglobinemia and Carbon Monoxide Poisoning Effects
- In methemoglobinemia, PaO2 may appear falsely elevated while pulse oximetry remains low; CO leads to falsely elevated oxygen saturation readings despite impaired oxygen delivery.
Predicting Mechanical Ventilation Needs in Myasthenia Gravis Patients
- Factors include duration of disease, co-existing respiratory conditions, and high doses of medication, all of which suggest higher likelihood of requiring mechanical support.
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Description
Test your knowledge on critical anesthesia topics including symptoms of right mainstem intubation, hypoxemia differential diagnoses, and the effects of methemoglobin and carbon monoxide on oxygen levels. Explore the risk factors for mechanical ventilation in myasthenia gravis patients.
