The Medical Student’s Anesthesia Pocketbook
University of Texas Health Science Center Houston
2
Table of Contents
Acknowledgements 2
Anesthesia Overview 3
Introduction 3
Preoperative History and Physical 3
IV’s and Premedication 6
Room Setup and Monitors 6
Induction and Intubation 9
Maintenance 10
Emergence 11
PACU concerns 12
Commonly Used Medications 13
Volatile Anesthetics 13
IV Anesthetics 14
Local Anesthetics 15
Opioids 15
Muscle Relaxants 16
Reversal Agents/ Anticholinergics 16
Pharm Charts 18
Inhalational Anesthetics 18
MAC 18
Intravenous Anesthetics 19
IV Fluids 20
ASA Classification 21
Mallampati Classification 22
Quick Reference/Review 23
Procedure Checklist 26
Intubation 27
IV line placement 27
Bag Mask Ventilation 27
Ventilator Settings 28
Arterial Line Placement 28
Central Line Placement 28
Spinal 29
Epidural 29
Resources 30
Notes 31
Contributors: Trent Bryson MS4, Tanner Baker MS4, Claudia Moreno MS4,
Darrell Wilcox MS3, and Allison DeGreeff MS3Acknowledgements
We the contributors would first and foremost like to thank the faculty at the University of Texas at Houston for their support, guidance, and teachings in helping us create this pocket book. We would also like to thank the residents for their contributions to our learning and skill development as well as in helping us revise the content to be as detailed, succinct, and accurate as possible.
Anesthesia Overview
Adapted from “A Medical Student’s Anesthesia Primer” by Roy G. Soto, MD (roysoto@ucla.edu)
Introduction
In many programs across the country, medical students are only exposed to two weeks of anesthesiology during their third or fourth year. The student often attends daily lectures and might be told to "read Miller's Basics of Anesthesia", but often by the time the student has finally figured out why we are doing what we're doing, the rotation is over, and he or she leaves with only a minimum of anesthesia knowledge.
This primer is intended to give a brief overview of what we do, when we do it, and why we do it for standard, uncomplicated cases ... the types that you are bound to see during your rotation. By no means is the information contained comprehensive, or intended to allow you to practice anesthesia solo, but it is intended to give an overview of the "big picture" in a format that can be quickly read in one sitting, and then referred to as needed. Keep in mind that there are many ways to accomplish the same thing in anesthesia, and you will undoubtedly see techniques that differ from what we've written here, but our goal again is to present you with a simple overview.
Anesthesia is a challenging and exciting specialty, but can also be extremely frustrating if not taught clearly during the short exposure that many medical students get to the field.
Preoperative History and Physical
Unlike the standard internal medicine H&P, ours is much more focused, with specific attention being paid to the airway and to organ systems at potential risk for anesthetic complications. The type of operation and the type of anesthetic will also help to focus the evaluation.
Of particular interest in the history portion of the evaluation are:
Coronary Artery Disease - What is the patient's exercise tolerance? How well will his or her heart sustain the stress of the operation and anesthetic? Asking a patient how he feels (i.e. SOB, CP) after climbing two or three flights of stairs can be very useful as a "poor man's stress test".
Hypertension - How well controlled is it? Intraoperative blood pressure management is affected by preoperative blood pressure control.
Asthma - How well controlled is it? What triggers it? Many of the stressors of surgery as well as intubation and ventilation can stimulate bronchospasm. Is there any history of being hospitalized, intubated, or prescribed steroids for asthma? This can help assess the severity of disease.
Kidney or Liver disease - Different anesthetic drugs have different modes of clearance and organ function can affect our choice of drugs.
Reflux Disease - Present or not? Anesthetized and relaxed patients are prone to regurgitation and aspiration, particularly if a history of reflux is present. This is usually an indication for rapid sequence intubation (succinylcholine + cricoid pressure).
Smoking - Currently smoking? Airway and secretion management can become more difficult in smokers.
Alcohol Consumption or Drug Abuse? - Drinkers have an increased tolerance to many sedative drugs (conversely they have a decreased requirement if drunk), and are at an increased risk of hepatic disease, which can impact the choice of anesthetic agents.
Endocrine:
Steroids – patients with recent steroid use may require preoperative steroids to cover secondary adrenal suppression.
Diabetes - Well controlled? The stress response to surgery and anesthesia can markedly increase blood glucose concentrations, especially in diabetics.
Thyroid – Hypo/Hyper metabolic states affect the cardiovascular system, renal clearance, and thermoregulation.
Medications - Many medications interact with anesthetic agents, and some should be taken on the morning of surgery (blood pressure medications) while others should probably not (diuretics, diabetes medications).
Allergies - We routinely give narcotics and antibiotics perioperatively, and it is important to know the types of reactions that a patient has had to medications in the past. The #1 anesthesia allergen is the non-depolarizing paralytics. The #2 class is antibiotics.
Family History - There is a rare, but serious disorder known as malignant hyperthermia that affects susceptible patients under anesthesia, and is heritable. Another heritable disorder is pseudocholinesterase deficiency which affects succinylcholine duration and may require extended postoperative ventilation.
Anesthesia history - Has the patient ever had anesthesia and surgery before? Did anything go wrong?
Last Meal - Whether the patient has an empty stomach or not impacts the choice of induction technique (another indication for rapid sequence intubation).
While a history of a difficult intubation may be the most reliable predictor of future difficult intubations, the physical exam is also important to help predict potential problems. For the physical exam, the specific areas which are of particular importance to the anesthesiologist include the cardiovascular system, lungs, head/neck/upper airway, signs of preexisting neurological dysfunction, and signs of coagulation dysfunction.
Many tests have been proposed to help predict difficulty with intubation, but no single factor, taken independently, has been able to accomplish this goal. However, when multiple factors are taken together, the predictive value is increased. The following some specific aspects of the head/neck/upper airway exam which can be used to help predict difficulties that may be encountered.
Head/Neck/Upper Airway exam
Facial trauma or deformities- may make it difficult to perform laryngoscopy.
Deviated septum or nasal polyps- can pose difficulty with nasal intubation or with inserting a nasogastric tube, possibly resulting in bleeding.
Neck range of motion- the patient needs to be able to assume the sniffing position (cervical flexion and atlanto-occipital extension) so that the oral, pharyngeal, and laryngeal axes are aligned which will facilitate viewing the glottic opening. Normal patients should achieve 35 degrees or more of atlanto-occipital extension, which can assessed by observing the angle traversed by the occlusal surface of the maxillary teeth when the head is fully extended from the neutral position. Difficulty with intubation may be predicted by a significant reduction in the ability to achieve this degree of extension or if the patient experiences any pain, tingling, or numbness during this movement.
TMJ mobility and degree of mouth opening- this is important for determining the adequacy of space for manipulating the laryngoscope and endotracheal tube. Measure the inter-incisor distance. An opening of < 3 cm or 2 finger breadths will likely not provide adequate space and may result in a difficult intubation. In addition, ask the patient to move the lower incisors as high on the upper lip as possible (upper lip bite test). If the lower incisors do not reach the vermilion border of the upper lip, this may be a sign of inadequate translational movement of the TMJ, which is also necessary for successful laryngoscopy.
Dentition- It is important to note the presence of dentures, poor dentition, loose teeth, or caps, which may not tolerate digital manipulation or may be at risk of damage when the laryngoscopic blade is inserted into the mouth. Dentures should be removed before surgery. In addition, the presence of prominent maxillary incisors may result in obstruction of the view of the glottis. Conversely, edentulous patients are generally easy to intubate, but may pose difficulty with mask ventilation.
Tongue/Oropharynx- Direct laryngoscopy allows visualization of the larynx by displacing the tongue anteriorly into the mandibular space, which moves the tongue out of the line of sight. A normal sized tongue will generally fit easily into the space between the two mandibular rami. However, if the tongue is too large (macroglossia) or the mandible is too small (micrognathia), there will likely be difficulty with proper visualization of the glottis. The Mallampati classification is a method to assess the tongue size in relation to the size of the oropharynx. The test is performed by having the patient sit with their head in the neutral position, and then open their mouth as wide as possible and protrude the tongue as far as possible. They should not phonate, as this can elevate the soft palate and alter the view. A Class 3 or 4 view may be associated with difficult laryngoscopy.
The size of the mandible can be assessed by measuring the thyromental distance. This is the distance from the mentum of the mandible to the thyroid cartilage. A thyromental distance of 6 cm (approximately 3 finger breadths) or less, as often seen in patients with a receding mandible or a short neck, may indicate a possible difficult intubation. Alternatively, the sternomental distance (from mentum to sternal notch) can also be used, which assesses the size of the mandible and neck. A sternomental distance of < 13 cm may also point to difficulty with intubation.
Finally, a physical status classification is assigned, based on the criteria of the American Society of Anesthesiologists (ASA1-5), with ASA-1 being assigned to a healthy person without medical problems other than the current surgical concern, and ASA-5 being a moribund patient, not expected to survive for more than twenty four hours without surgical intervention. An "E" is added if the case is emergent. The full details of the classification scale are also detailed later.
IV’s and Premedication
The two skills you should take the opportunity to practice while on your rotation are IV insertion and airway management/intubation. Every patient (with the exception of some children that can have their IV's inserted following inhalation induction) will require IV access prior to being brought to the operating room. The key to success with IV placement is preparation and patience. All of us have successfully found and cannulated a vein, only to find that we left the bag of IV fluid or the tape across the room. Normal saline, Lactated Ringer's solution, or other balanced electrolyte solutions (Plasmalyte, Isolyte) are all commonly used solutions intraoperatively.
Many patients are understandably nervous preoperatively, and we often premedicate them, usually with a rapid acting benzodiazepine such as intravenous midazolam (which is also fabulously effective in children orally or rectally). Metoclopramide, Bicitra, and/or an H2 blocker are also often used if there is a concern that the patient has a full stomach, and anticholinergics such as glycopyrrolate can be used to decrease secretions.
Room Setup and Monitors
Before bringing the patient to the room, the anesthesia machine, ventilator, monitors, and cart must be checked and set up. The anesthesia machine must be tested to ensure that the gauges and monitors are functioning properly, that there are no leaks in the gas delivery system, and that the backup systems and fail-safes are functioning properly. ...
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