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Volume assessment

1 Why do we administer fluids? What is the most important reason perioperatively? Although there are many reasons to administer fluids to patients (correct electrolyte imbalances, administer drugs, nutrients, antibiotics, etc.), the ultimate goal of perioperative fluid administration is to increase cardiac output in an effort to better perfuse end-organs (e.g., heart, brain, kidneys). This goal can be realized when a fluid bolus increases venous return,…

Perioperative point-of-care ultrasound and echocardiography

1 What is the role of point-of-care ultrasound and echocardiography in the perioperative and critical care setting? Ultrasound is a valuable diagnostic tool capable of providing real-time, rapid evaluation of patients. It is mobile, easy to use, safe, and less expensive than other imaging modalities, making its application pertinent to a variety of clinical environments—perioperative, critical care, emergency department, outpatient clinics, or inpatient wards. Ultrasound is…

Central venous catheterization

1 Define central venous catheterization. A central venous catheter (CVC) or central line is a catheter that is placed into a large vein such that the catheter’s distal orifice is within a central vein. The target central vein for CVCs placed in the internal jugular (IJ) or subclavian is the superior vena cava (SVC), and for the femoral vein, the inferior vena cava (IVC). Please see…

Blood pressure monitoring and arterial catheterization

1 What methods are available to measure blood pressure? Blood pressure (BP) measurements can be divided into direct and indirect methods. Indirect methods include using a cuff or palpation of a pulse, whereas direct methods use an arterial catheter. The most common indirect or noninvasive BP (NIBP) measurement uses a BP cuff, usually on the arm over the brachial artery. An NIBP can be measured using…

Capnography

1 What is capnometry? Capnometry is a monitor which detects and measures expired carbon dioxide (CO 2 ). Capnometry can be qualitative where the device changes color when CO 2 is detected, or quantitative where the device measures the expired CO 2 concentration. The capnogram is a waveform tracing of the quantified CO 2 concentration over time. Interpreting the capnography waveform can be helpful with troubleshooting…

Pulse oximetry

1 Review pulse oximetry Pulse oximetry is a noninvasive method by which arterial oxygenation can be approximated. It is based on the Beer-Lambert law and spectrophotometric analysis. When applied to pulse oximetry, the Beer-Lambert law essentially states that the intensity of transmitted light passing through a vascular bed decreases exponentially as a function of the concentration of the absorbing substances in that bed, and the distance…

Vasoactive agents

1 What are the benefits of vasoactive agents? All major components governing the physiology of cardiac output, such as preload, afterload, inotropy, and chronotropy can be modulated by vasoactive agents. An underlying concept is the Frank-Starling principle, which states that increased myocardial fiber length, or preload, improves contractility up to an optimal state, then decreases with excess preload. Vasoactive agents, such as inotropes, can increase contractility,…

Local anesthetics

1 Discuss the role of local anesthetics in the practice of anesthesiology Because local anesthetics (LAs) reversibly block nerve conduction, they are used to provide intra- and postoperative regional anesthesia for painful surgical procedures. Beyond regional anesthesia, local anesthetics (most notably lidocaine) can be administered intravenously to attenuate the pressor response to tracheal intubation, decrease coughing during intubation and extubation, and act as systemic analgesics. Lidocaine…

Neuromuscular blocking agents

1 Describe the morphology of the neuromuscular junction The neuromuscular junction (NMJ) consists of three cell types: the motor neuron, muscle fiber, and Schwann cell. The motor neuron originates in the ventral horn of the spinal cord or brainstem (in the case of the cranial nerves) and travels uninterrupted to the neuromuscular junction as a large myelinated axon. Upon approaching the muscle, it forms a spray…

Opioids

1 What is an opiate? An opioid? A narcotic? Opiates are analgesic and sedative drugs that contain opium or an opium derivative from the poppy plant ( Papaver somniferum ). Opiates include opium, morphine, and codeine. An opioid is any substance with morphine-like activity that acts as an agonist or antagonist at an opioid receptor (i.e., δ-, κ-, and μ-receptors). Opioids may be exogenous or endogenous…

Intravenous anesthetics

1 What qualities would the ideal intravenous anesthetic agent possess? The ideal intravenous induction would produce amnesia, analgesia, hypnosis, and muscle relaxation. Adverse effects and interactions would be rare. Administration would be painless via multiple routes of delivery. Interindividual dose variability would be low and the agent would have a predictably rapid onset and offset. There would be no cardiac, renal, hepatic, immune system, or central…

Inhaled anesthetics

Questions/Answers 1 What are the most desirable properties of an anesthetic gas? The most desirable properties of an anesthetic gas are predictability in onset and emergence; muscle relaxation, cardiostability, and bronchodilation; nontriggering for malignant hyperthermia or other significant side effects (such as nausea and vomiting); be nonflammable; undergo no transformation within the body; allow easy estimation of concentration at the site of action; and have no…

Perioperative medical ethics

1 What are the four foundational moral values of medical ethics? Respect for autonomy: patients have the right to determine what can and cannot be done to their bodies Nonmaleficence: do no harm, or at least, do more good than harm Beneficence: do what is in the best interest of the patient Justice: scarce healthcare resources should be distributed as justly as possible 2 Why is…

Perioperative patient safety

Allergic Reactions 1 Review the four types of hypersensitivity reactions and their mechanisms See Table 12.1 . Table 12.1 Hypersensitivity Classification Type of Reaction Name Mechanism Examples Type I Allergic reaction Previous exposure to an antigen produces IgE immunoglobulins which binds to mast cells and basophils. Following reexposure, the antigen cross-links two IgE receptors initiating a cascade that ultimately results in release of potent vasodilating mediators…

Transfusion therapy

1 What is the overarching indication for blood transfusion? The overarching indication for transfusing packed red blood cells (RBCs) is to improve oxygen delivery ( D˙O2 D ˙ O 2 ). One of the primary roles of RBCs is to transport oxygen from the lung to tissue to allow aerobic metabolism. D˙O2 D ˙ O 2 is dependent upon the cardiac output (CO) and the arterial…

Coagulation

1 How can you identify a patient at risk for perioperative bleeding? Preoperative evaluation for bleeding risk includes a focused history, physical examination, a review of all medications and dietary supplements, appropriate laboratory testing and a consideration of the bleeding risk inherent to the scheduled surgical procedure. Questions should be asked about prior bleeding in nonsurgical settings (e.g., tendency to form large hematomas after minor trauma,…

Electrolytes

Questions: Electrolytes Sodium 1 How is hyponatremia classified? Classification is primarily based on the patient’s serum osmolality and volume status. Hyponatremia may occur in the presence of low serum osmolality (< 285 mOsm/kg), normal osmolality (285–295 mOsm/kg), or high osmolality (> 295 mOsm/kg). Elevated total body water is more common than a loss of sodium disproportionate to free water losses. This elevation is typically caused by…

Volume regulation and fluid replacement

1 Describe the functionally distinct compartments of body water Total body water comprises approximately 60% of body weight. About two-thirds of body water (40% of body weight) is in the intracellular fluid compartment and one-third (20% of body weight) is in the extracellular compartment. Of the fluid in the extracellular compartment, three-quarters (15% of body weight) is comprised of interstitial fluid and one-quarter (5% of body…

Arterial blood gas analysis

1 What information does an arterial blood gas provide? Arterial blood gas (ABG) machines provide a direct measurement of partial pressure of oxygen in arterial blood (PaO 2 ), partial pressure of carbon dioxide in arterial blood (PaCO 2 ), pH by using electrodes that measure changes in voltage, current, and resistance. It uses this data to calculate bicarbonate ion ( HCO−3 HCO 3 − ),…

Pulmonary physiology

1 Define lung volumes and capacities Tidal volume (TV) = Volume of gas inspired and passively expired with normal breathing Expiratory reserve volume (ERV) = Volume of gas that can be maximally exhaled from rest Residual volume (RV) = Volume of gas remaining in the lung after maximal exhalation Functional residual capacity (FRC) = ERV + RV Inspiratory reserve volume (IRV) = Volume of gas that…