Anesthesia and Respiratory Physiology Quiz

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.