bluuebunny/crossref_metadata_2025 huggingface dataset:
What Can Frogs Teach Us about Resilience? Adaptive Renewal in Amphibian and Academic Ecosystems
Authors: Byrne Allison Q
Published: May 2024

Synopsis

Examples of resilience in nature give us hope amid a growing biodiversity crisis. While resilience has many definitions across disciplines, here I discuss resilience as the ability to continue to adapt and persist. Naturally, as biologists, we seek to uncover the underlying mechanisms that can help us explain the secrets of resilience across scales, from individuals to species to ecosystems and beyond. Perhaps we also ponder what the secrets to resilience are in our own lives, in our own research practices, and academic communities. In this paper, I highlight insights gained through studies of amphibian resilience following a global disease outbreak to uncover shared patterns and processes linked to resilience across amphibian communities. I also reflect on how classical resilience heuristics could be more broadly applied to these processes and to our own academic communities. Focusing on the amphibian systems that I have worked in—the Golden Frogs of Panama (Atelopus zeteki/varius) and the Mountain Yellow-Legged Frogs of California (Rana muscosa/sierrae)—I highlight shared and unique characteristics of resilience across scales and systems and discuss how these relate to adaptive renewal cycles. Reflecting on this work and previous resilience scholarship, I also offer my own thoughts about academia and consider what lessons we could take from mapping our own adaptive trajectories and addressing threats to our own community resilience.
On the singularity point in acoustic orthorhombic media
Authors: Stovas Alexey
Published: May 2024

The acoustic orthorhombic model is widely used in seismic modeling and processing of P-wave data. However, the anisotropic acoustic models have so called S-wave artifacts (1 artifact in transversely isotropic acoustic medium and two artifacts in orthorhombic acoustic medium). I show that S-wave artifacts can have one singularity point that results in complications in polarization field and the group velocity surface. The conditions of the existence of this point are defined in terms of anellipticity parameters. This singularity point and its group velocity image are the objects of my analysis.
Neck Anatomy
Authors: Pan Wenyu , Malik Tariq M.
Published: May 2024

The anatomy of the neck is essential for anesthesia practice, including airway management, central venous catheter cannulation through the internal jugular vein, nerve blocks for regional anesthesia, and cervical sympathetic block for pain syndromes. The anatomy of the neck is divided into the anterior and posterior neck triangles by the sternocleidomasoid muscle. The anterior triangle contains airway structures, thyroid, and major vessels of the neck, while the posterior triangle contains most nerves of interest that are blocked for postoperative analgesia of shoulder and arm. This chapter reviews the major landmarks of the neck and important learning points related to its anatomy. Airway innervation, implications of nerve injury, and anatomy of the cricothyroid membrane are reviewed. Major vascular structures of the neck, bony landmarks, and application in central venous access and nerve blocks are delineated.
Principles of Ultrasound
Authors: Young Emily , Zaky Sherif
Published: May 2024

Ultrasound is a safe and noninvasive tool that uses sound waves to produce a real-time image of organs and tissues. Medical ultrasound uses high frequency waves between 2 000 000–15 000 000 Hz (2–15 MHz). As the ultrasound beam travels through the body, it is attenuated by the tissues via absorption, reflection, and scattering. Reflection of ultrasound waves depends on the difference in the acoustic impedance between two substances. Acoustic impedance of a substance depends on its density and the propagation speed of ultrasound through this substance. When an ultrasound beam reflects at the interface between two materials, it creates an “echo” which can be described as hyperechoic, hypoechoic, or anechoic. Anesthesiologists can compensate for attenuation by adjusting overall gain or gain at certain depth (time gain compensation). Spatial resolution (axial and lateral) refers to the ability to distinguish between two objects in space as separate echoes. Temporal resolution is the ability to distinguish between two events in time. Penetration refers to the ability of ultrasound waves to reach deep structures. The higher the frequency, the more the ultrasound beam is attenuated as it travels, and the less distance it can penetrate.
Principles of Doppler Ultrasound
Authors: Young Emily , Zaky Sherif
Published: May 2024

Doppler ultrasound is a modality that can be used to examine the direction, velocity, and pattern of blood flow in a vessel. This imaging modality uses the principles of the Doppler effect to detect movement within body tissues. It is most often used to examine the direction, speed, and pattern of blood flow in a target vessel or across a valve. Doppler ultrasound works by detecting shifts in frequency that occur when sound waves reflect off a moving surface. If an object is moving toward the ultrasound probe, the reflected frequency of the ultrasound beam is shifted higher. If an object is moving away from the ultrasound probe, the reflected frequency is shifted lower. The transducer detects these positive and negative shifts and uses them to display information about detected blood flow as a waveform or a color image. Continuous wave Doppler emits a continuous sound beam and receives all returning signals. It detects all signals along its path. Pulsed wave Doppler sends out a sound beam in short pulses. An “electronic gate” can be set to evaluate only Doppler signals from a certain target depth. Color flow Doppler assigns a color hue to moving objects based on their direction and speed. The color flow image is superimposed on a traditional gray-scale image, allowing for real-time assessment of blood flow within specific anatomical structures. Power Doppler detects subtle, low-volume flow. It uses the amplitude of the returning Doppler signals to generate an image without providing information about direction of flow.
Vaporizer Types and Safety Features
Authors: Aquino Ben
Published: May 2024

The vaporizer is a key component of any anesthesia machine and any gas-based anesthetic, using oxygen and other carrying gases to deliver vaporized volatile anesthetic gas to the patient via the anesthesia circuit—in a predictable, consistent, easily controlled, and safe way. The vaporizers in use today include the variable-bypass vaporizer, dual-circuit vaporizer, and cassette vaporizer. The variable bypass vaporizers are used for sevoflurane and isoflurane. The high vapor pressure and low boiling point of desflurane make it unusable in a variable bypass vaporizer at normal room temperature. As a result, it is dispensed via its own unique dual-circuit vaporizer, where it is heated in one circuit and then the vaporized gas is added to the carrier gas mixture in the other circuit. Modern-day vaporizers have multiple structural and schematic features that ensure safe delivery of volatile anesthetic to the patient. These safeguard against potential problems, such as overfilling or tipping the vaporizer, filling the vaporizer with the wrong gas, or leaking.
Toxicity of Inhaled Anesthetics
Authors: Drennen Zachary , Cormican Daniel S.
Published: May 2024

Inhalational anesthetics are ubiquitous, reliable agents with which a patient can be placed under general anesthesia. Although rare, there are documented toxicities associated with the use of these agents. Older agents such as methoxyflurane, halothane, and enflurane are no longer used, due in large part to their associated toxicities. Newer agents such as isoflurane, sevoflurane, and desflurane are not without risk of toxicities of their own. Despite being vital to human life, oxygen is also associated with neurological, respiratory, and ocular toxicities through the formation of reactive oxygen species. The toxicities associated with inhaled agents and oxygen are discussed further herein.
Heart Functions
Authors: Noor Nazir , Viswanath Omar
Published: May 2024

The American Society of Anesthesiologists (ASA) has five standard monitors which are intended to provide critical physiologic monitoring for the anesthetized patient. Additional monitoring, whether invasive or noninvasive, depends on the condition of the patient and the procedure they are scheduled to undergo. One of the most important organ systems to monitor is the heart. Three important approaches in monitoring the heart function include the physical exam and auscultation of the heart tones, the electrical activity of the heart via electrocardiography (EKG), and assessing the motion of the heart walls via transesophageal echocardiography (TEE). These three approaches in assessing the heart function of the perioperative patient are the topic of discussion in this chapter.
Mechanical Ventilators
Authors: White Peggy , Giordano Chris
Published: May 2024

Mechanical ventilators have substantially evolved over the last half century to facilitate the management of respiratory decompensation. They have transitioned from operating room and intensive care units to transport and noninvasive options. To appreciate these options, the healthcare provider needs to recognize the forces applied to the pulmonary system and the resulting pulmonary mechanics for the safe delivery of anesthesia. Dynamic and static compliance impacts the efficacy of gases that the ventilator delivers. Ventilator scalars (flow, pressure, or volume as functions of time) provide a graphical understanding of the ventilator-pulmonary interface. By applying the information from scalars, anesthesia professionals can optimize patient-ventilator synchrony.
Drug Absorption and Distribution
Authors: Parker Nicholas M.
Published: May 2024

Two important components of pharmacokinetics are absorption and distribution. Absorption depends on the route of administration and chemical properties of the drug. Intravenous administration bypasses the absorption step completely, while absorption after oral administration requires a complex series of events that many molecules cannot survive. Distribution refers to drugs moving from the bloodstream to tissues throughout the body, and depends on local blood flow, protein binding, and chemical factors like the drug’s partition coefficient. Impairments in absorption or distribution may necessitate a change in dose and/or route to attain the desired effect; such changes are common in the operating room given conditions like fluctuating blood pressure and administration of blood products.
Tolerance and Tachyphylaxis
Authors: Zaky Sherif , Hozian Nicholas
Published: May 2024

Tolerance is defined as the progressive diminished response to a drug at a certain dose following repeated exposure, thus requiring increased dosage on subsequent administrations to achieve the same effect. It is a state of adaptation in which exposure to a certain dose of a drug for a long duration of time leads to diminished drug effects. Tachyphylaxis is a type of tolerance that develops acutely within only a few doses of a drug. Both terms involve biological responses to certain dosages of drugs and include similar cellular mechanisms but differing rates of desensitization. Cellular mechanisms of tolerance and tachyphylaxis involve pharmacokinetic (absorption, distribution, metabolism, and elimination) and pharmacodynamic (receptor adaptive changes, recruitment of opposing mechanisms, and downregulation) changes. Management of such conditions can be difficult and can involve increasing dosage and frequency, drug rotation, and gradual weaning of the drug of concern to allow for restored pharmacological response to the drug in the future.
Hepatic Blood Flow
Authors: Jones Courtney R.
Published: May 2024

The liver receives nearly a quarter of the cardiac output every minute and serves as a large reservoir of blood. It is unique in that it has a dual supply of oxygenated blood from the portal vein and the hepatic artery. The interaction between the two sources of blood supply is complex, and the two work together to maintain nearly constant hepatic blood flow; the hepatic arterial buffer response is one of the specialized mechanisms that allow for regulation in hepatic arterial flow in response to the portal venous flow. Anesthesiologists should also be aware that the hepatic blood flow is affected by general anesthesia, neuraxial anesthesia, inhalational anesthetics, and intravenous anesthetics. The physiology of hepatic blood flow is often manipulated during liver transplantation to modulate portal venous flow and improve the graft outcome.
Propofol
Authors: Ferguson Kris , Papapetrou Peter
Published: May 2024

Propofol is one of the most common intravenous anesthetic agents. It rapidly crosses the blood-brain barrier for quick onset of action at the GABA A receptor. Termination of action is through liver metabolism and diffusion. Propofol is a short acting medication that can induce and maintain general anesthesia. Sedation is dose dependent, and effects can range from sedation with varying levels of amnesia to general anesthesia. Propofol decreases postoperative nausea and vomiting. Propofol has been shown to be safe in children as an induction dose. Long-term, continuous infusion of propofol can cause propofol infusion syndrome, which involves metabolic acidosis, rhabdomyolysis, heart failure, and kidney failure. This combination of metabolic deragements can be fatal if not appropriately treated.
Calcium Channel Blockers
Authors: Sprowell Andrew , Sharma Archit
Published: May 2024

Calcium plays an important part in various bodily processes, such as blood coagulation, esophageal tone, enzyme systems, muscle contraction, bone metabolism, synaptic transmission, myocardial contractility, and conduction, as well as vascular smooth muscle reactivity. Due to these effects, this group has found widespread application in treatment of arrhythmias, angina, pulmonary hypertension, achalasia, and esophageal spasm. Hence, it can be anticipated that any drug interfering with the action of calcium could have widespread effects. This chapter emphasizes the effects that calcium channel blockers have and the anesthetic implications of managing a patient that is using these medications.
Guidelines for Perioperative Cardiovascular Evaluation
Authors: Hanna Rewais B. , Abd-Elsayed Alaa
Published: May 2024

In 2014, the American College of Cardiology/American Heart Association Task Force introduced guidelines for perioperative cardiovascular evaluation in an attempt to minimize the risk of major cardiac events during surgery. The preoperative evaluation of a patient should include (1) assessment of perioperative risk, (2) determination of the need for changes in management, and (3) identification of cardiovascular conditions or risk factors requiring longer-term management. Lastly, the objective of preoperative evaluation is to encourage shared decision-making between providers and patients about their cardiovascular risk prior to surgery.
ASA Classification
Authors: Patel Sheetal , Abd-Elsayed Alaa
Published: May 2024

ASA classification is widely used for preoperative risk assessment and prediction of postoperative complications of surgical patients. It is also useful to predict perioperative risks when used with other factors such as type of surgery, functional status of the patient, and frailty. Higher ASA class is associated with a substantial increase in risk. ASA classification is popular among all other available tools to predict risks for the patient for the surgery due to its simplicity and quickly assessment.
Uremia
Authors: Walia Anureet , Sharma Archit
Published: May 2024

Uremia refers to high levels of urea in the blood, which usually occur during renal failure due to the inability of the kidneys to excrete urea in the urine. Renal failure leads to the patient having constitutional symptoms, nausea, tremors, and encephalopathy. Extracellular fluid overload from sodium retention, in association with increased cardiac demand from anemia, leads to these patients being prone to congestive heart failure. Prolonged severe uremia can lead to pericarditis and pleural effusion, as well as uremia-induced platelet dysfunction and malnutrition. Treatment involves providing supportive care, maintaining renal perfusion by fluid resuscitation or vasopressors, avoiding nephrotoxic agents, and eventually hemodialysis, if all other means fail.
Obstructive Sleep Apnea
Authors: Varshney Shivani , Yuan Adam Yu
Published: May 2024

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder seen in the surgical population. It is an independent risk factor for increased morbidity and mortality during the perioperative period. Patients with OSA present complex challenges to the anesthesiologist with compromised cardiopulmonary reserves, increased sensitivity to anesthetic drugs, and a potentially difficult airway. These patients tend to be obese and often have other associated comorbidities such as hypertension, diabetes, and heart failure. Preoperative recognition of at-risk patients, perioperative utilization of continuous positive airway pressure (CPAP) therapy, and a well-designed anesthetic plan will improve outcomes in patients with OSA.
Hypertension
Authors: Dagher Talia H. , Beck Lauren
Published: May 2024

Hypertension is a prevalent disease that affects all aspects of perioperative care. Hypertension is typically managed with diet, exercise, and antihypertensive medications, including calcium channel blockers, beta blockers, ACE-inhibitors, and diuretics. Preoperative optimization is key, with the goal of normotension prior to surgery; however, this is not always feasible. Intraoperative blood pressure may be labile in this patient population, and appropriate management of both hypertension and hypotension is important to reduce morbidity and mortality. The risk of postoperative hypertension is also increased in this patient population. Intravenous labetalol and hydralazine are the most commonly used antihypertensive agents in the post-anesthesia care unit if this occurs.
Anesthetic Management of Patients with Allergies
Authors: Girma Brook , Kaye Alan D.
Published: May 2024

Adverse drug reactions are an unfortunate occurrence during anesthesia. Prior to surgery the anesthesiologist should gather any clinical or past medical history to assess whether the patient is at risk for a possible drug allergy. The most effective management to prevent an allergic reaction is to avoid the allergen itself. Prophylactic treatments include corticosteroids alone or in combination with an H1 antagonist.
Prophylactic Cardiac Risk Reduction
Authors: Gibson Christina , Cormican Daniel S.
Published: May 2024

This chapter focuses on perioperative cardiac risk assessment and evaluation. The ACC/AHA have published guidelines for perioperative testing and management, including revascularization and medical therapy, focusing on beta-blocking agents, antiplatelet agents, statins, and angiotensin converting enzyme (ACE) inhibitors. If noninvasive test results will not change patient management, then further testing is not warranted. Patients who may benefit from stress testing include those who have at least one risk factor or elevated risk with poor or unknown functional capacity. The ACC/AHA guidelines indicate the role of preoperative revascularization and timing of elective surgery following stent placement, based on the type of stent and the antiplatelet therapy utilized. Evidence suggests that patients who undergo revascularization prior to surgery show no benefit over those who are medically optimized. Patients with stable coronary artery disease and multiple cardiac risk factors are likely to benefit from beta-blocker therapy. Beta blockers should be initiated several weeks prior to surgery and titrated to appropriate heart rate and blood pressure levels to minimize adverse effects in the perioperative period. Patients on chronic beta-blocker therapy should continue their medication perioperatively. Perioperative statin therapy should also be continued and is recommended for all vascular surgery patients. ACE inhibitors are associated with perioperative hypotension; however, no increased risk of adverse cardiovascular events has been shown. Antiplatelet agents result in increased risk of bleeding. Therefore, the risk of bleeding versus thrombosis needs to be weighed in the context of the surgical procedure and discussed with each patient.
Airway Devices
Authors: Schmitt Ben , Jani Jai
Published: May 2024

This chapter explores commonly used devices for placement of endotracheal tubes, including direct laryngoscopy techniques, fiberoptic devices, video laryngoscopy, and transillumination. The focus is on how the device works, and unique aspects of each technique. Direct laryngoscopy relies upon creating a line of sight from mouth to larynx to visualize insertion of an endotracheal tube. Video and fiberoptic technologies rely on indirect visualization (either through viewing lens or video screen) and do not require alignment of oral, pharyngeal, and laryngeal axis. Transillumination relies upon the anterior positioning of the trachea, and ability to see a bright light emitted from inside the trachea as a red glow on the patient’s neck.
Types of Endotracheal Tubes
Authors: Jindal Aparna , Sharma Archit
Published: May 2024

Endotracheal tubes serve the function of securing the airway and acting as a conduit between the ventilator and the patient to assist with gas exchange. Different types of tubes are used in different situations, based on their properties, patient size, and the type of surgery being performed. These are commonly used devices that are critical for patient safety, so it is important to understand their design and use. Modifications were made to the initial design to accomplish tasks, such as minimizing aspiration, isolating a lung, providing a clear facial surgical field during general anesthesia, monitoring laryngeal nerve damage during surgery, preventing airway fires during laser surgery, and administering medications. This chapter discusses the various kinds of endotracheal tubes and their clinical applications.
Colloids
Authors: Watt Stacey , D’Auria Anthony
Published: May 2024

The textbook Basic Anesthesia Review examines the anesthesiologist’s role in intravenous fluid administration as an integral component of an anesthesiologist’s responsibilities and surveys the efficacy, benefits, and potential deleterious effects on the use of the colloid solutions: albumin, hetastach, and pentastarch. This chapter reviews the differences between crystalloid and colloid solutions in terms of intravascular volume expansion, colloid reactions, the effects of albumin on sodium concentration, and the effects of hydroxyethyl starches (HESs) on coagulation, and renal dysfunction. It also reviews intravascular and extravascular volume and a brief description of the glycocalyx layer. This chapter is targeted for anesthesiology residents in preparation for Basic Exam Review.
Acetylcholinesterase-Inhibitor Toxicity
Authors: Guz David , Johnson Angela
Published: May 2024

The use of acetylcholinesterase-inhibiting agents (AChI) is widespread and particularly relevant to the perioperative physician, who will commonly encounter patients on chronic AChI therapy and also frequently will administer these drugs as a component of typical anesthetic management. The events leading up to the development of AChI medications for therapeutic purposes was fraught with reports of cholinergic toxicity, which is the mechanism behind many commonly used pesticides and chemical nerve agents. As with any medication, therapeutic effects of AChI must be weighed against the potential for toxicity, and it is paramount that the perioperative physician is well equipped to recognize and manage this situation. This chapter will review acetylcholinesterase inhibitors, cholinergic toxicity, and its treatment.
Opioids
Authors: McGinty Lauren
Published: May 2024

Opioids are widely used to treat somatic, visceral, and neuropathic pain associated with a variety of medical conditions. This chapter reviews the indications, mechanisms of action, therapeutic effects, adverse effect profiles, and special precautions associated with different agents. It addresses significant drug interactions and available routes of administration for different opioids. Finally, this chapter highlights unique advantages and disadvantages associated with the agents in this medication class.
Spinal Cord Reflexes
Authors: Woodrow Alex , Sharma Archit
Published: May 2024

Many functions of the spinal cord are controlled by the brain, but certain functions also executed independently, such as spinal reflexes. Spinal reflexes include the stretch reflex, the Golgi tendon reflex, the crossed extensor reflex, and the withdrawal reflex. Pathway for any reflex action is known as reflex arc. These spinal reflexes allow for faster reflex response to occur by activating spinal motor neurons, and also contribute to normal muscle tone. Reflex tests are an important component of a neurological exam, to confirm integrity of the spinal cord or to diagnose the presence and location of spinal cord injury. This chapter reviews the various spinal reflexes and their clinical implications.
Psychological, Social, and Vocational Influences on Pain Perception
Authors: Rushmer Timothy , Abd-Elsayed Alaa
Published: May 2024

The understanding of pain and the factors that influence it has come a long way from the strictly biological perspective of the past. Now, experts agree, pain is best understood with a biobehavioral or biopsychosocial model. These models integrate the physiological, social, and psychological components that influence pain and its perception across the lifetime of the patient. This is a broad and expanding area of study, but this chapter will focus on the highlights of these influences.
Termination of Action
Authors: Stedman Robin B.
Published: May 2024

This chapter discusses the termination of action of the neurotransmitters of the sympathetic and parasympathetic nervous systems. This includes termination of action of norepinephrine, the neurotransmitter of the postganglionic adrenergic fibers, of epinephrine released by chromaffin cells, and of acetylcholine, the neurotransmitter of the postganglionic cholinergic fibers and autonomic ganglia.
Heat Loss Mechanisms
Authors: MacCormick Samuel , Kohan Lynn
Published: May 2024

This chapter covers intraoperative heat loss mechanisms leading to hypothermia. Hypothermia is an important physiologic mechanism with many perioperative risks affecting both morbidity and mortality. Identifying potential sources of heat loss, specifically related to anesthetic techniques and the environment, is integral to the prevention and management of hypothermia. There are three phases associated with heat loss while under general anesthesia. The first phase accounts for the majority of heat loss and encompasses redistribution of body heat as anesthetics induce vasodilation and the core body temperature rapidly drops. The second phase includes environmental losses (radiation, convection, conduction, evaporation), and phase three is the equilibrium phase. Management strategies in the preoperative, intraoperative, and postoperative periods include both passive and active warming techniques. However, prevention of hypothermia remains the most important and effective strategy.
Effect of Drugs/Anesthetic Technique on Temperature Regulation
Authors: Guruswamy Jayakar , Angappan Santhalakshmi
Published: May 2024

This chapter on the effect of drugs/anesthetic technique on temperature regulation gives an overview of the impact of both general anesthetic drugs and neuraxial techniques on thermoregulation. General anesthesia decreases the metabolic rate by 20%–30%. General anesthesia inhibits any behavioral and autonomic responses to temperature fluctuations. The interthreshold range increases up to 10-fold, from 0.2°–0.4°C to 2°–4°C. Volatile anesthetics such as sevoflurane or nitrous oxide and intravenous anesthetics such as propofol and opioids impair thermoregulatory control. Sedatives like midazolam have minimal effects on thermoregulation. Neuraxial anesthesia inhibits central thermoregulatory control. Behavioral responses are impaired by neuraxial anesthesia. The effects of general anesthesia and regional anesthesia on thermoregulation are additive.
Blood Supply
Authors: Abdallah Rany T. , Villatoro-Lopez Jasmin
Published: May 2024

The spinal cord is located in the vertebral cavity and runs from the foramen magnum to the second lumbar vertebra (L2). The blood supply of the spinal cord derives from two sets of branches from the dorsal aorta. The main blood supply of the spinal cord is via the single anterior spinal artery (ASA), providing blood to the anterior two-thirds of the spinal cord, along with the two posterior spinal arteries, which provides blood to the posterior one-third of the spinal cord. Anterior spinal cord syndrome within the region of the lumbar spinal cord and vertebral artery dissection may occur; however, both can be treated.
Regulation of Airway Caliber
Authors: Lapkouski Vadzim , Jamroz Tatiana
Published: May 2024

Neural control of airway diameter is predominantly via the parasympathetic system with afferent and efferent fibers in the vagus nerve. Stimulation by foreign bodies in the airway or inhalation of cold air or irritant pollutants stimulates reflex bronchoconstriction acting via release of acetylcholine and activation of M3 cholinergic receptors. Once stimulated, M3 receptors activate a Gq protein, which in turn activates phospholipase 3 to produce inositol triphosphate, which causes release of calcium from the airway smooth muscle sarcoplasmic reticulum. Humoral control of airway diameter is dominated by the effects of circulating adrenaline acting on the plentiful β-2 adrenoreceptors found on airway smooth muscle. The mechanism of action of the β-2 receptor is clearly elucidated, and involves the agonist binding within the core of the protein, stabilizing the molecule in its activated state. In this state the β-2 receptor stimulates a linked Gs protein to activate adenylate cyclase to produce cyclic adenosine monophosphate (cAMP), which inhibits calcium release from intracellular stores and causes the actin-myosin contractile units to become less calcium sensitive.
Ventilation/Perfusion
Authors: Farela Andrea , Jamroz Tatiana
Published: May 2024

Lung ventilation and pulmonary perfusion are essential components of the normal function of the lung, but it is their ratio (V/Q) that determines adequate gas exchange. This chapter on ventilation/perfusion defines the main concepts about gas exchange in the lungs and different factors involved in its variability throughout the lung. It reviews the concepts of dead space and shunt, and its effects on V/Q, as well as the mechanisms involved in V/Q mismatch. It also mentions the most common pathologies that exemplify dead space and shunt. A typical example of pathology causing V/Q mismatch secondary to increased dead space is pulmonary embolism, while acute lobar atelectasis, extensive acute lung injury, pulmonary edema and pneumonia are pathologic states that increase shunt fraction.
Alveolar Gas Equation
Authors: Teixeira Camila , Jamroz Tatiana
Published: May 2024

The alveolar gas equation (AGE) was created to estimate the partial pressure of oxygen inside the alveoli (PAO2). The equation relates PAO2 to three major variables: inspired oxygen tension (PiO2), alveolar partial pressure of carbon dioxide (PACO2), and respiratory quotient (R). The variation or manipulation of any variable quantity has a significant impact on PAO2 values, eliciting different clinical responses. In the clinical practice, the AGE is used to calculate the alveolar-arterial O2 gradient (A-a gradient). The simplified equation has its application limited to a steady state condition. The elaborated version of the AGE has an extra term within brackets which is given to compensate a larger O2 uptake than O2 elimination over the alveolar capillary membranes.
Carbon Dioxide Response Curves
Authors: Cornwell Drew , Kohan Lynn
Published: May 2024

Building upon earlier discussions of peripheral and central chemoreceptors, this chapter discusses the carbon dioxide and oxygen response curves. Additional discussion is held regarding the changes in alveolar ventilation that occur in response to commonly seen clinical influences and scenarios. A linear relationship exists between PaCO2 and alveolar ventilation. When graphically represented, predictable changes in the slope and position of this relationship can be seen with inhaled anesthetics >1 MAC, opioids, CNS depressants, and hypoxia. A strong understanding of this concept is an effective clinical tool in the administration of an anesthetic.
Perioperative Smoking and Caffeine Use
Authors: Swanson David E.
Published: May 2024

Preoperative smoking can increase the length of hospital stay, infection, pulmonary, neurological and wound complications, as well as the odds of an intensive care admission and mortality. If patients can stop smoking 4 weeks ahead of surgery, this will decrease the reactivity of the airways and lessen the chance for bronchospasm, laryngospasm, hypoxia, and wound-healing complications. The perioperative discussion of smoking cessation is an important window when patients are thinking of their health. Many patients are also addicted to caffeine, and withdrawal headaches may occur. Tobacco smoking and likely vaping nicotine have significant effects on the cardiopulmonary systems at the cellular and subcellular level, putting these patients at higher risk of morbidity and warranting heightened vigilance in their care. Caffeine is an effective adjunct for treating many types of headaches and has long been touted for mild post-dural puncture headaches without solid evidence of significant benefit.
Anticholinergics
Authors: Markatos Sheridan , Manders Larry
Published: May 2024

Anticholinergics block the neurotransmitter acetylcholine in the brain and peripheral tissues. Inhaled anticholinergics, including ipratropium bromide and tiotropium bromide, are important medications in the management of COPD and severe asthma. They have slower onset of action than beta agonists and are therefore used for long-term management rather than acute exacerbations. However, inhaled anticholinergics can be useful in the perioperative setting to mitigate the parasympathetic response to airway instrumentation. This chapter briefly discusses the mechanism of action on anticholinergics and briefly outlines the two major drugs in this class and possible side effects.
Synchronicity of Pressure
Authors: Ahmed Muhammad Fayyaz , Ahmed Furqan
Published: May 2024

The cardiac physiology relies on a synchronized series of events that occur with every heartbeat. They are characterized by electrical and mechanical events. The mechanical events consist of phases of systole (isovolumetric contraction and ejection) and diastole (isovolumetric relaxation and ventricular filling). Associated with these phases are the valvular actions of valve opening or closing. The changes in pressure in the heart chambers create a pressure wave in the central venous system, which can be of diagnostic assistance in certain pathologies.
Impulse Propagation
Authors: Dakhlallah Nadeen , Manders Larry
Published: May 2024

The heart’s pumping capabilities are regulated by an electrical conduction system that coordinates contraction of the chambers of the heart. The main components of the heart’s electrical conduction system are the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers. This chapter summarizes impulse propagation and discusses the electrophysiology of the heart.
Venous Return
Authors: Nowatzke Ryan , Manders Larry
Published: May 2024

The venous system is a high capacitance system containing ~70% of the total blood volume. Change in central venous pressure (CVP) can dramatically alter the volume of blood return to the heart. A complex regulatory system governs venous capacitance. In times of stress, the volume stored within the venous system can be recruited to increase cardiac output via increase input from the sympathetic nervous system. Further complicating the subject, blood volume in the venous system differs by age, sex, and underlying medical comorbidities. This chapter summarizes venous return to the heart, the factors that govern it, and the various physiological changes commonly experienced in anesthesia.
Heart Conduction System
Authors: Pellicer Robert , Abd-Elsayed Alaa
Published: May 2024

The cardiac conduction system is a specialized collection of cells that generate and propagate action potentials throughout the heart in order to facilitate the synchronized contraction of myocardium. The system consists of the sinoatrial (SA) node, the atrioventricular (AV) node, and the His-Purkinje system. The SA node acts as the heart’s pacemaker, generating action potentials at a rate determined by the “funny current,” a mixed sodium-potassium current that may be modulated by the autonomic nervous system. As impulses are generated along the conduction system, they pass through the AV node, where a brief delay prevents simultaneous atrial and ventricular contraction. As the action potential reaches the ventricles, the His-Purkinje system ensures synchronized ventricular depolarization in order to maximize cardiac output. Action potentials propagated along the conduction system are exquisitely regulated by varying physiologic states and neural mediators.
Vasopressors and Inotropes
Authors: Sohn Jacqueline , Pesa Nicholas
Published: May 2024

Inotropes are pharmacologic agents that increase contractility of the heart. Vasopressors are pharmacologic agents that cause vasoconstriction. Not all adrenergic agents are pure inotropes because some of them have vasopressor effects also. This chapter reviews the basic physiology and pathways of vasopressors and inotropes. It also discusses specific pharmacological agents categorized by either their structure or function: endogenous catecholamines, synthetic catecholamines, sympathomimetics, PDE-inhibitors, vasopressors used in obstetric anesthesia, and others. Each pharmacologic agent’s mechanisms of action, common uses, and side effects are also discussed.
Vasodilators
Authors: Besada Stefan , Nguyen Christina T.
Published: May 2024

This chapter provides an overview of the current and commonly used vasodilators in anesthesia practice today. Nitrovasodilators, adrenergic antagonists, dopamine agonists, and calcium channel blockers are discussed, including the pharmacokinetics and pharmacodynamics of each drug, dosing, and suggested uses. Included in this chapter is a table readily outlining dose, onset, and elimination half-life of each of the vasodilators, which serves as a useful quick reference. It becomes readily apparent that each one of these agents has their own specific clinical indications. This chapter also outlines the heavily tested topics of adverse reactions associated with these agents, such as cyanide toxicity, methemoglobinemia, reflex tachycardia, or rebound hypertension.
Synthetic and Recombinant Hemoglobins
Authors: Tillmans Samuel , Watt Stacey
Published: May 2024

This chapter on synthetic and recombinant hemoglobins discusses hemoglobin-based oxygen carrier blood substitutes that one may encounter during the practice of anesthesiology. It will also discuss the impact these substiutions have on the longevity of storage and potential impact the use of these symthetic and recombinant hemoblobins may have on patient care. Recombinant hemoglobin and synthetic blood are extremely important in light of blood shortages, possible contaminants, limited donor blood shelf life, donor blood storage issues, and ethical issues involving blood donation. This chapter addresses specific advantages, disadvantages, costs, and other aspects of these artificial hemoglobins to our healthcare systems.
Thyroid Gland
Authors: Chamu Jauhleene , Johnson Angela
Published: May 2024

This chapter identifies relevant anatomy and physiology of the thyroid gland while describing thyroid gland disorders and the perioperative considerations necessary to adequately manage patients with thyroid disease. The physiology of iodine utilization to make thyroid hormone and the negative feedback system between the hypothalamus, pituitary, and thyroid gland to control thyroid hormone production are described. Etiologies and treatment for both hypothyroidism and hyperthyroidism can be found. This chapter also provides management strategies for the clinical manifestations of severe hyperthyroidism and hypothyroidism-thyroid storm and myxedema coma, respectively. Furthermore, it explores the preoperative, intraoperative, and postoperative considerations for a patient with thyroid disease undergoing surgery.
Adrenal Cortex Anatomy and Physiology
Authors: McCafferty Brendan , Pesa Nicholas
Published: May 2024

The adrenal gland is a structure that sits on the superior pole of the kidneys bilaterally. It is composed of two distinct glands with unique anatomy and physiology. This chapter will focus on the outer layer of the adrenal gland, the adrenal cortex. This layer produces hormones that are vital to life, such as cortisol and aldosterone. The adrenal cortex can be further separated into three layers: zona fasciculata, zona glomerulosa, and zona reticularis. Each layer is associated with the production of specific hormones. Pancreatic anatomy is discussed briefly at the end of the chapter.
Protein Synthesis, Structure, and Function
Authors: Stuckey Ryan , James Dominika Lipowska
Published: May 2024

Proteins are large and complex biomolecules that play an essential role in structure and regulation of function within an organism. Twenty different amino acids are utilized as building blocks in the creation of polypeptide chains in the process of protein formation. These polypeptide chains undergo conformational changes to create functional proteins. Protein function is highly dependent on its structure; change to the polypeptide chain sequence may alter protein’s function. Absence or dysfunction of proteins can lead to a disease state. Proteins are the most structurally diverse biological molecules and are involved in a vast array of functions within an organism, including structural support to organelles, cells, and tissues; selective transport of molecules and ions across the cellular membrane; cellular communication; and as enzymatic activity–intracellular metabolic catalysts. All proteins except antibodies and clotting factor VIII are formed in the liver.
Cyclic Adenosine Monophosphate (CAMP) and Cyclic Guanosine Monophosphate (CGMP)
Authors: James Dominika Lipowska , Unnithan Ajay S.
Published: May 2024

Human physiology is highly dependent on a well-coordinated system of communication between cells. A multitude of external signals, including hormones, neurotransmitters, and other molecules, interact with cells via specific cell-surface receptors. This signal-receptor interaction can subsequently trigger a cascade of secondary events within the cell, including activation of intracellular second messenger systems that coordinate the cell’s response to the initial stimulus. Two important molecules involved in this second messenger cascade are cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). A wide range of physiological processes utilize these second messenger systems. These intracellular processes are involved in the regulation of a vast number of physiological processes, including metabolism and everything from endocrine, gastrointestinal, and immune function to cardiovascular homeostasis.
Physician Impairment and Disability
Authors: Saad Ramsey , Hanna Joseph Salama
Published: May 2024

Physician impairment is defined as the inability to practice medicine with reasonable skill and safety to patients by the reason of psychiatric or general medical conditions. In order to be a board certified anesthesiologist, a physician would be required to complete medical education followed by residency and possibly fellowship, board certification exams in addition to fulfilling Maintenance of Certification in Anesthesiology (MOCA) requirements. In order to ensure safe anesthesia care as well the anesthesiologist, and possibly his or her coworkers need to be aware of signs and symptoms of physician impairment. This chapter outlines the various methods of detecting this, in addition to the ethical and legal challenges which face the practitioner and institution regarding safe return to work.
Medical Errors
Authors: Hanna Joseph Salama , Saad Ramsey
Published: May 2024

This chapter reviews previously suggested definitions of medical errors and adverse events. It discusses various types of errors, including action-based like accidental placement of a needle in the carotid artery during central venous cannulation or endotracheal tube placement in the esophagus instead of the trachea., decision-based which are mainly secondary to faulty knowledge or judgment, and communication-based errors which occurs commonly in the operating room setting and are the leading root cause of serious adverse events that result in patient harm. It enumerates possible methods of prevention for such medical errors.
LGBTQ
Authors: Goldstein Mark A. , Goldstein Myrna Chandler
Published: May 2024

LGBTQ individuals experience unique health disparities, and each of the LGBTQ populations has their own health concerns that may be further impacted by race, ethnicity, socioeconomic status, age, and other factors. LGBTQ youth are at increased risk for depression and suicidal ideation. Among LGBTQ youth, rates of substance use may be higher than heterosexual youth; homelessness is a significant issue for LGBTQ youth. LGBTQ youth are targets of increased levels of violence, victimization, harassment, and stigmas. Many LGBTQ adolescents use social media as a primary means to interact with other LGBTQ adolescents; social media does provide a communication opportunity, but LGBTQ youth also face online harassment. While schools are a domain where homophobia may exist, there are also strategies that have been shown to promote the safety and well-being of LGBTQ youth in the school setting.
Bereavement and Mortality
Authors: Goldstein Mark A. , Goldstein Myrna Chandler
Published: May 2024

The death of a parent is probably the most traumatic event that may occur to an adolescent. Close to three percent of adolescents have lost a parent to death by age 18. This loss challenges adolescents with short-term grief and long-term emotional and economic support issues. Prolonged grief after the loss may increase an adolescent’s risk for anxiety, depression, suicidality, or substance use. Brief interventions may help prevent adolescents from developing more severe problems after the loss of a parent. The Family Bereavement Program, a 12-month intervention for parentally bereaved children and adolescents, demonstrated results in reducing internalizing and externalizing problems in females. The Writing for Recover intervention confirmed that writing about traumatic experiences might alleviate grief symptoms in bereaved adolescents.
Pain and Adverse Childhood Experiences
Authors: Katzman William G. , Fabbro Anilla Del
Published: May 2024

In this chapter, the effects of childhood trauma on mental and physical pain are explored. The chapter begins with a discussion regarding the relationship between physical and psychological pain in the context of trauma. Subsequently, a focus is given to adverse childhood experiences (ACEs) with regard to their defining principles, correlates with other social determinants of health, and their effects on psychological and physical pain. Within this discussion, it is clear that the effect of ACEs frequently leads to subsequent pain, which can manifest in a number of different disorders and diseases. This often stems from the way that these early traumas have effects on an individual’s biology, psychology, and social capacities. Finally, the chapter explores pain-based interventions, including primary, secondary, and tertiary strategies, and it highlights an array of interventions that health care providers must consider to improve the mental and physical health of individuals with both experiences of pain and childhood trauma.