Anesthesia: A Clerkship Pocket Guide (2020-2021) PDF

Print: ISBN 978-1-927565-27-8 E-book: ISBN 978-1-927565-28-5 1 2 Anesthesia: A Clerkship Pocket Guide 2020 - 2021 3 GLOBAL OBJECTIVES: To create a free, peer-reviewed practical resource for learners that is both physically accessible in the...

Print: ISBN 978-1-927565-27-8 E-book: ISBN 978-1-927565-28-5 1 2 Anesthesia: A Clerkship Pocket Guide 2020 - 2021 3 GLOBAL OBJECTIVES: To create a free, peer-reviewed practical resource for learners that is both physically accessible in the OR and in hospital, and educationally-appropriate for a clerk’s back- ground level of knowledge and experience. To cover the required McMaster core anesthesia clerkship learning objectives and Essential Clinical Encounter (ECE) topics so that students can review concepts and questions that may arise during the rotation. To provide a sufficient scope of knowledge that clerks may integrate information learned from this core to other specialties (internal medicine, emergency medicine, critical care medicine, OBGYN, family medicine, etc.). To encourage a better understanding of the pharmacology behind common drugs en- countered in anesthesia including their indications, mechanism of action, considerations for usage, and effects. HOW TO USE THIS RESOURCE This resource is grounded in the McMaster core anesthesia clerkship learning objectives and Essential Clinical Encounters (ECEs; a list of high-priority topics and probing ques- tions that students should be exposed to longitudinally during their clerkship). We suggest using this pocket guide as an accessible adjunct to your clerkship rotation. It cannot substitute for your time in the OR with an anesthesiologist, which will provide in- valuable experiential learning, or the required modules, tutorials, and simulation activities. This resource does not attempt to contain the depth of knowledge required to gain a comprehensive understanding of any topic covered. If you are interested in learning more about a particular topic, references are provided at the end of each section. Additionally, if something here differs from the practice by the staff in front of you, consider that many practices in all areas of medicine can vary by hospital and by physician — an- esthesia is no different. Being curious about the nuances can lead to valuable discussions and learning opportunities. We sincerely hope you enjoy and learn as much as possible from your anesthesia clerkship rotation! If you have any suggestions or comments, please email [email protected]; we would love to hear your thoughts and feedback! Disclaimer Though this resource has been reviewed to the best of our ability, we fully acknowledge the rapidly changing nature of medicine as well as human error. The scope of what this resource can offer is of a general nature only. Those associated with creating this resource are not responsible for errors or omissions or for any consequences which may arise from the use of this resource. Funding The development, printing, and distribution of this book was generously supported by WRC Research at the Michael G. DeGroote School of Medicine Waterloo Regional Campus, McMaster University. 4 Contributors Author and Editor-in-Chief Grace M Xu, BHSc Michael G DeGroote School of Medicine McMaster University Section Reviewers Jared Cohen, BSc Yvgeniy Oparin, BHSc Michael G DeGroote School of Medicine Michael G DeGroote School of Medicine McMaster University McMaster University Ellen N Connelly, HBSc Lauren Riehm, BSc Michael G DeGroote School of Medicine Michael G DeGroote School of Medicine McMaster University McMaster University Gwendolyn Lovsted, BAS Misha Virdee, BSc Michael G DeGroote School of Medicine Michael G DeGroote School of Medicine McMaster University McMaster University Senior Reviewers Denise Darmawikarta, MD, MPH David Parsons, MD Department of Anesthesia Department of Anesthesia McMaster University McMaster University Dillon Horth, MBChB Jacob Salituri, MD, CCFP (FPA) Department of Anesthesia Department of Anesthesia McMaster University Associate Staff, Orillia Soldiers’ Memorial Hospital Russell Lenferna, MD Department of Anesthesia Janice Yu, MD University of Saskatchewan Department of Anesthesia McMaster University Natalie Lidster, MD Department of Anesthesia Songbo Zheng, MD, CCFP (FPA) McMaster University Catherine Moores, MD Department of Anesthesia McMaster University 5 Staff Reviewers Rafik Bolis, MBBCh, MSc, CCFP, FRCPC David Lagrotteria, MD, FRCPC Assistant Clinical Professor, Dept. of Assistant Clinical Professor, Dept. of Anesthesia, McMaster University Anesthesia, McMaster University Director of Bariatric Anesthesia, Under- Staff Anesthesiologist, Niagara Health graduate Site Coordinator, St. Joseph’s Healthcare Hamilton Kevin Latchford, MD, PhD, FRCPC Assistant Clinical Professor, Dept. of Daniel Cordovani, MD, MSc Anesthesia, McMaster University Associate Professor, Dept. of Anesthesia, Staff Anesthesiologist, Grand River McMaster University Hospital/St Mary’s General Hospital Director, Anesthesia Undergraduate Program Amanda Whippey, MD, FRCPC Staff Anesthesiologist, Hamilton Health Assistant Clinical Professor, Dept. of Sciences Anesthesia, McMaster University Pediatric Anesthesiologist, Hamilton Health Sciences Illustrator Adhora Mir, BSc Michael G DeGroote School of Medicine McMaster University Many thanks to WRC Research, including: Graham Campbell Andrew Costa, MD, PhD Lindsay Krahn Connor MacAlpine Sarah Penhearo 6 Table of Contents Contributors 5 Pre-operative assessment 10 Goals of pre-op assessment 11 Investigations and optimization 11 Immediate pre-op assessment 12 Previous surgical/anesthetic/family hx 12 Mallampati classification 13 Obstructive sleep apnea (OSA) 14 Severe obesity 14 Diabetes mellitus 14 COPD 15 Post-operative nausea/vomiting 15 PACU handover 16 Complications & emergencies 17 Malignant hyperthermia 17 Pseudocholinesterase deficiency 17 Orientation to the monitors and anesthetic machine 19 CAS standard monitoring guidelines 20 Basics of mechanical ventilation 22 Complications & emergencies 23 Auto-PEEP/dynamic hyperinflation 23 Myocardial ischemia/infarction 23 The anesthetic machine 24 Preparing the OR: SOAP-IM 26 Airway management, intubation, and emergencies 28 Bag-mask ventilation 29 Indications for intubation/mechanical ventilation 31 Direct laryngoscopy and intubation 31 Elective induction 33 Rapid sequence induction 33 Supraglottic airway vs endotracheal tube 34 Ventilation vs oxygenation 35 Hypoventilation and hypoxemia 35 Criteria for extubation 36 Complications & emergencies 36 Anaphylaxis 36 Aspiration 37 Bronchospasm 37 Laryngospasm 37 Status asthmaticus 38 Pneumothorax 38 Can’t intubate, can’t oxygenate 38 Fluid management and resuscitation 42 Definitions 43 Blood therapy and related definitions 44 Vascular access sites 45 Starting a peripheral IV 46 Starting an arterial line 46 Preoperative volume status 47 Intraoperative volume status 47 Intraoperative BP management 47 7  Classical fluid management 48 Complications & emergencies 49 Intraoperative hypotension 49 Intraoperative hypertension 50 Managing trauma 50 Massive transfusion 52 Pain control 55 Definitions 56 Managing pain using the anesthetic ladder approach 57 General anesthesia 59 Regional anesthesia 59 Obstetrical anesthesia 61 Physiological changes in pregnancy 62 Neuraxial vs general anesthesia for c-section 63 Epidural analgesia and anesthesia 64 Spinal anesthetic 64 Complications & emergencies 67 Supine hypotension syndrome 67 Pre-eclampsia/eclampsia 67 Amniotic fluid embolus 67 Post-partum hemorrhage 67 Local anesthetic systemic toxicity 68 High regional block/total spinal 68 Post-dural puncture headache (PDPH) 68 Pediatric anesthesia 71 Anatomic differences in children 72 ETT sizing 73 Complications & emergencies 74 Laryngospasm 74 Basic pharmacology in anesthesia 76 Goals of anesthesia 77 Phases of anesthesia 77 Definitions 77 Paralytic/neuromuscular blocking agents (NMBAs) 79 Quick drug reference 82 Anxiolytics 84 Midazolam Lorazepam Induction agents 86 Propofol Ketamine Etomidate Volatile anesthetics 89 General volatile anesthetic properties Sevoflurane Desflurane Isoflurane Nitrous oxide Opioid analgesics 92 General opioid properties Morphine Hydromorphone 8  Fentanyl Remifentanil Meperidine Sufentanil Naloxone Non-opioid analgesics 96 Acetaminophen Ibuprofen Ketorolac Local anesthetics 99 Lidocaine Bupivicaine Paralytics 101 Rocuronium Succinylcholine Cis-atracurium Dantrolene Vasoactive & autonomic drugs 105 Ephedrine Phenylephrine Epinephrine Norepinephrine Vasopressin Esmolol Labetalol Hydralazine Nitroglycerin Reversal agents and anticholinergics 115 Neostigmine Atropine Glycopyrrolate Sugammamdex Post-operative nausea/vomiting 119 Dexamethasone Ondansetron Dimenhydrinate/diphenhydramine Metoclopramide Miscellaneous 123 Amiodarone Magnesium sulfate Oxytocin 9  Pre-operative assessment Section reviewer: Yvgeniy Oparin Senior reviewer: Janice Yu, MD Staff reviewer: Daniel Cordovani, MD Knowledge-based objectives: Describe the role of the preoperative anesthetic assessment with regards to optimizing patient risk. Explain the presentation and management of malignant hyperthermia as an example of the hypermetabolic state. Explain the presentation and management of pseudocholinesterase deficiency (plasma cholinesterase) as an example of a pharmacogenetic disease. Essential Clinical Encounters objectives: List 3 comorbidities that may be more commonly seen in the obese patient. How can OSA impact a patient’s disposition post-operatively? Think of strategies to minimize OSA related complications post-operatively. How might a patient’s hypoglycemic therapy may need to be adjusted perioperatively? For a patient with COPD/asthma, think of strategies to prevent bronchospasm perioper- atively. Describe the components of a pre-anesthestic airway exam. Describe the Mallampati classification system. Describe the ASA classification system. Skills objectives: Assess a patient who has an ASA class I or II classification with regards to their readiness for anesthesia by taking an appropriate history and performing a relevant physical examination. Assess the patient’s airway for ease of mask ventilation, SGA insertion, or ETT. 10 GOALS OF PRE-OP ASSESSMENT Identify and quantify concerns to adapt your anesthetic management: Identify CC/HPI and operation Identify pre-op conditions/risk factors Quantify and characterize conditions/risk factors with hx and appropriate investigations Optimize pt if possible Adapt anesthetic technique to promote pt safety and stability throughout perioperative period (e.g. general vs regional anesthetic, ETT vs SGA, RSI, monitoring, drug properties) Advanced care planning where appropriate (i.e. medical directives) Post-operative disposition plan (i.e. home / wards / step-down unit / ICU) INVESTIGATIONS AND OPTIMIZATION May be ordered in pre-op to assess pt condition and potential ways to optimize before surgery. Labs can be redone just prior to surgery if indicated. Always consider if pre-op testing is truly beneficial to pt care before ordering, especially for asymptomatic pts undergoing low-risk surgery. See https://choosingwiselycanada.org/anesthesiology for details. Investigations and indications for pre-optimization Investigation Indications CBC Major surgery requiring group & screen or match Malignancy Chronic CV, respiratory, renal, hepatic disease Suspected or known anemia or coagulopathy Pt 24h without surgery 6 Declared brain dead Organ donor awaiting transplant ✷ E added if emergent surgery (e.g. ASA 3E) MALLAMPATI CLASSIFICATION Mallampati classification: what can be visualized? 1 2 3 4 Faucial Faucial pillars, Soft palate Hard palate pillars, soft palate only only soft palate, partial uvula entire uvula Figure 1: Mallampati classification 13 OBSTRUCTIVE SLEEP APNEA (OSA) Definition: Decreased or complete cessation of breathing during sleep. Sleep study showing apnea-hypopnea index (AHI) ≥15/hr, or ≥5 with symptoms or CV comorbidities. Signs/symptoms: ↓ SpO2, intermittent hypoxia/hypercapnia. Complications/comorbidities: Systemic/pulmonary HTN, LVH, arrhythmias, cognitive impairment, increased susceptibility to respiratory depression, obesity hypoventilation syndrome. Risk factors: STOP-BANG (≥ 3 = high likelihood of OSA) Snoring Tired (daytime somnolence) Observed periods of apnea Pressure (HTN) BMI > 35 Age > 50 Neck circumference > 40cm Gender (male) Pre/intra-operative management: Supplemental O2 and adequate pre-oxygenation, CPAP/BiPAP therapy preoperatively (ask pt to bring their own machine), opioid-sparing multimodal/regional techniques, reverse Trendelenburg positioning, extubation when awake. Post-operative management: Careful monitoring for apnea and cardiorespiratory complications (may require continuous oximetry monitoring overnight before discharge), supplemental O2, CPAP/BiPAP therapy, semi-upright or lateral position, opioid-sparing analgesia. SEVERE OBESITY Definition: BMI ≥35 Physiological changes: ↑CO, ↑GFR, ↑ total body weight/volume, ↑ metabolic rate, ↑ oxygen demands. Complications: Difficult BMV, rapid desaturation on induction, ↓ lung volumes, ↓ chest wall/diaphragm compliance (esp with Trendelenburg, pneumoperitoneum), obesity hypoventilation syndrome, OSA. Pre/intra-operative management: Continue CPAP/BiPAP if used at home, consider inherent risk of proposed surgery and assess cardiorespiratory status with appropriate investigations, avoid respiratory depressants, be aware of lipophilic drugs that may have delayed clearance in obese people (e.g. desflurane vs sevoflurane). Post-operative management: Extubate when awake, optimal positioning, CPAP if used at home, careful monitoring for respiratory complications. DIABETES MELLITUS Physiological changes: Autonomic dysfunction (orthostatic HTN, hypothermia), HTN, CAD, PVD, CKD, ↓ gastric motility, stiff joint syndrome, hypoglycemia. Complications: Silent MI, poorer wound healing, autonomic/peripheral neuropathy, stiff joint syndrome, “full” stomach. Pre-operative management: Take comprehensive hx (type I or II, glucose control, insulin-dependence, evidence of end-organ/autonomic dysfunction, airway exam, meds), 14 measure glucose frequently, insulin infusion for more aggressive glycemic control, con- sider RSI if gastroparesis present, hold hypoglycemic agents while NPO and may need to reduce dose the night before procedure. Post-operative management: Measure glucose frequently, monitor for post-op compli- cations associated with end-organ damage, ensure basal insulin levels, dextrose infusion if hypoglycemic. COPD Physiological changes: Obstructive lung disease, ↑ compliance, ↑ mucus secretions, V/Q mismatch, alveolar hypoventilation, ↓ gas transfer, pulmonary HTN. Complications: Bronchospasm, laryngospasm, hemodynamic instability, baro/ volutrauma, auto-PEEP, post-op complications (e.g. infections, respiratory failure). Pre/intra-operative management: Assess exercise tolerance and severity of disease, counsel on smoking cessation perioperatively, continue puffers until day of surgery, consider regional anesthesia, obtain baseline room air ABG pre-operatively, consider art line (serial ABGs for high-risk pts; comparison to baseline may help guide timing for extubation), positive pressure during preoxygenation. Post-operative management: Respiratory support and close monitoring, suctioning and physiotherapy to avoid sputum plugging, high risk pts should be monitored with ABGs and compared to baseline. POST-OPERATIVE NAUSEA/VOMITING Chemoreceptor trigger zone (CTZ): Area of the brainstem which is stimulated through opioid, serotonin (5HT3), histamine, dopamine, and muscarinic ACh receptors. Adequate stimulation will communicate signaling to initiate vomiting. Simplified Apfel score for PONV: Other risk factors: Female Younger age Hx of PONV or motion sickness Volatile anesthetics Non-smoker Surgery >2h Post-operative opioids Pregnancy Abdomen, breast, ENT/ophthalmic, neurosurgery Score from 0-4 (% incidence of PONV): 0 – 10% 1 – 20% 2 – 40% 3 - 60% 4 - 80% PONV prophylaxis usually involves 1-2 drugs: Ondansetron Dexamethasone Dimenhydrinate Haloperidol (See Quick Drug Reference: Post-operative nausea/vomiting.) Other preventative strategies: Multimodal analgesic approach to minimize opioid use Regional/local anesthesia 15  Use propofol for induction and maintenance of general anesthesia rather than volatile anesthestics Euvolemia (adequate hydration) Metoclopramide/H2 receptor antagonist/PPI PACU HANDOVER General ID (age / sex) Procedure and type of anesthetic Most responsible physician Allergies Significant PMHx/medications Anesthetics Anesthetics given NMBA reversed? (Y / N) Intubation (easy / hard, # of attempts) Other Significant intra-op events Abx given/time Fluids (in: pRBC, crystalloids; out: UOP, EBL) Foley? (Y / N) Lines (gauge / location) Post-op pain management 16 COMPLICATIONS & EMERGENCIES MALIGNANT HYPERTHERMIA Definition: A rare autosomal dominant genetic condition that can be triggered by certain anesthetic agents leading to ↑↑ Ca2+ release, sustained muscle contraction, and hyper- metabolic crisis. Triggers: Succinylcholine, volatile agents (except N2O). Signs/symptoms: Early: ↑ ETCO2, ↓ SpO2, ↑ HR, ↑ RR, masseter spasm Late: HTN, total body rigidity, severe lactic acidosis, hyperthermia, rhabdomyolysis. Complications: Hyperthermia, hyperK+, arrhythmias, DIC, AKI, cerebral edema, compart- ment syndrome, cardiac arrest, death. DDx: Light anesthesia, insufflation with CO2, thyroid storm, sepsis, pheochromocytoma, serotonin-syndrome, neuroleptic malignant syndrome. Risk factors: F/Hx of MH, unexplained fever/cramps/weakness, myopathies. Prevention: Identify at-risk pts through F/Hx, book as first case of the day, replace circuit/ CO2 absorbers, remove vaporizers and flush machine, remove succinylcholine vials from cart, TIVA, carefully monitor ETCO2 and temperature, have dantrolene available. Management: Stop succinylcholine/volatile agents, 100% FiO2, push dantrolene, treat K+ abnormalities and acidosis, increase minute ventilation, cool pt, supportive care; consider muscle biopsy/genetic testing post-op. PSEUDOCHOLINESTERASE DEFICIENCY Definition: An autosomal recessive genetic condition in which there is a deficiency in the enzyme that breaks down certain anesthetic drugs. Triggers: Succinylcholine, mivacurium. Signs/symptoms: Prolonged respiratory paralysis/apnea. Complications: Prolonged mechanical ventilation, respiratory failure if extubated early. DDx: Diaphragmatic paralysis, hypoK+, hyperMg2+. Risk factors: Use of succinylcholine, F/Hx of pseudocholinesterase deficiency or unex- plained extended paralysis under general anesthesia. Prevention: Identify at-risk pt and avoid triggering agents. Management: Continue mechanical ventilation and hemodynamic support until paralysis self-resolves; record condition in pt chart. 17 References: Adriano, A., & Skanchy, J. (2018). 2018 CA-1 tutorial textbook (12th ed.). Retrieved from http://ether.stanford.edu/ca1_new/Final- 2018 CA-1 Tutorial Textbook.Smartphone or Tablet.pdf Barash, P., Cullen, B., Stoelting, R., Cahalan, M., Stock, M.C., Ortega, R., … Holt, N. (2017). Clinical anesthesia (8th ed.). Philadelphia: Wolters Kluwer Butterworth, J. F., Mackey, D. C., & Wasnick, J. D. (2018). Morgan & Mikhail’s Clinical Anesthesiology. New York: McGraw-Hill Education. Dobson, G., Chong, M., Chow, L., Flexman, A., Kurrek, M., Laflamme, C.,... & Thiessen, B. (2018). Guidelines to the practice of anesthesia–revised edition 2018. Canadian Journal of Anesthesia/Journal canadien d’anesthésie, 65(1), 76-104. doi:10.1007/s12630-017- 0995-9 Gan et al. (2014). Consensus Guidelines for the Management of Postoperative Nausea and Vomiting. Anesthesia & Analgesia, 118(1), 85-113. doi: 10.1213/ ANE.0000000000000002 OpenAnesthesia. (n.d.). Retrieved from https://www.openanesthesia.org Pardo, M., & Miller, R. D. (2017). Basics of Anesthesia (7th ed.). Elsevier Health Sciences. Raymer, K. (2012). Understanding anesthesia: A learner’s guide (1st ed.). McMaster University. Sullivan, P. (2012). The Ottawa anesthesia primer. Toronto: Echo Book Publishing. Wainwright, N., Lidstar, N., & Cordovani, D. (2018). The pre-operative assessment [E-mod- ule]. Retrieved from https://medportal.litmos.com/course/1715751. 18  Orientation to the monitors and anesthetic machine Section reviewer: Yvgeniy Oparin Senior reviewer: David Parsons, MD Staff reviewer: Daniel Cordovani, MD Knowledge-based objectives: Describe at least 3 systems (i.e. circuits) for delivering oxygen to patients. Explain common mechanical ventilation parameters (volume control and pressure control ventilation, respiratory rate, tidal volume, pressure and PEEP). Describe how we measure patient ventilation and oxygenation and how to determine if they are adequate. Demonstrate appropriate use of the circuit and ventilator with minimal assistance. Essential Clinical Encounters objectives: List 5 anesthetic considerations for laparoscopic surgery. Why can end tidal CO2 increase during laparoscopic surgery? If a patient’s condition raises concerns of cardiovascular instability intraoperatively, how could you adapt your technique in terms of monitoring? How would you detect and manage an intraoperative myocardial infarction? According to the Canadian Anesthesiologists’ Society, which monitors must be continu- ously used intraoperatively? According to the Canadian Anesthesiologists’ Society, which monitors must be immedi- ately available if needed? Skills objectives: Place appropriate monitoring devices prior to induction (ECG, NIBP, SpO2). 19 CAS STANDARD MONITORING GUIDELINES Required continuously: Available for use without delay: Oxygenation Temperature probe 1. Pulse oximeter Peripheral nerve stimulator Stethoscope Ventilation Available without undue delay: 2. ETCO2 capnography Spirometer for tidal volume 3. Agent-specific anesthetic gas Manometer for ETT cuff pressure monitor Circulation 4. ECG 5. NIBP (q3-5m) PULSE OXIMETRY Provides an estimate of arterial oxygenation expressed as percent saturation Tracing can be used to assess HR, perfusion status, volume status (plethysmography variation index) Falsely-low SpO2: Methemoglobin (SpO2 approaches 85%; may be falsely higher or lower), nail polish, shivering, ↓ perfusion, misplaced sensor, IV dyes such as methylene blue. No effect on SpO2: HbF, HbS, bilirubin. Falsely-high SpO2: Carboxyhemoglobin, red nail polish. NON-INVASIVE BP May be used with invasive monitoring techniques (e.g.art-line) ECG Usually 3 or 5 electrodes; defaults to monitoring lead II 3 electrode: “White on the right, smoke (black) over fire (red).” 5 electrode: “Snow (white) over trees (green); chocolate (brown) close to the heart.” White = R arm Black = L arm Red = L leg Green = R leg Brown = V5 CAPNOGRAPHY Waveform and numerical measurement of end-tidal concentration of CO2. ETCO2 is ~2-5mmHg lower than PaCO2 in healthy lungs (normal PaCO2 is 35- 45mmHg). This gradient is due to mixing with anatomic, alveolar, or mechanical dead space air; the gradient is increased in diseased lungs and in cases of poor pulmonary perfusion. Reasons for increased ETCO2: Hypermetabolic states (e.g. MH, sepsis), sudden release of tourniquet, insufflation with CO2 (e.g. laparoscopic surgery), hypoventilation, rebreathing, saturated CO2 absorber. Reasons for decreased ETCO2: Hypometabolic states (e.g. hypothermia), decreased pulmonary blood flow (e.g. PE), hyperventilation, tubing leakage/kink, low cardiac output states. 20 Figure 2: Examples of capnography waveforms 21 BASICS OF MECHANICAL VENTILATION (See also Airway management, intubation, and emergencies.) Pressure control: Set inspiratory pressure applied per breath. Volume control: Set tidal volume per breath. Trigger: What initiates the breath (i.e. pressure vs flow)? Limit: What determines the volume given (i.e. patient vs ventilator)? Cycle: What determines the end of a breath (i.e. flow vs time)? Tidal volume: The volume of air expired in one breath (typically ~6mL/kg). Minute ventilation: The total volume of air inhaled or exhaled in one minute. Tidal volume x RR. I:E ratio: Ratio of time spent in inspiratory phase:expiratory phase. Normally 1:2 but can be decreased (e.g. 1:3) for pts with obstructive lung disease to reduce risk of hyperinfla- tion. Positive End-Expiratory Pressure (PEEP): Maintains patency of small airways with positive pressure at the end of exhalation; ↓ preload, ↑ ICP. Compliance: ΔVolume/ΔPressure BASIC VENTILATION SETTINGS Volume Control (VC): Set VT and RR; machine delivers this minute ventilation at a constant flow rate. Advantages: Delivers a guaranteed tidal volume. Disadvantages: Associated with higher inspiratory pressures and barotrauma Pressure-Control Ventilation (PCV): Set Inspiratory pressure and RR; machine delivers this pressure for a specified inspiratory time. Advantages: Associated with lower inspiratory pressures and lowers barotrauma risk. Disadvantages: Tidal volume varies with changing lung compliance (e.g. insufflation, patient positioning, changes in muscle relaxation). Pressure Control Ventilation with Volume Guarantee (PCV-VG): Machine delivers set tidal volume at minimum required inspiratory pressure and is adjusted breath-by-breath. Guarantees a minimum minute ventilation while minimizing risk of barotrauma. Common ventilation mode intraoperatively. Synchronized Intermittent Mandatory Ventilation (SIMV): Machine synchronizes with pt’s breathing pattern and delivers ventilator breaths between pt-triggered breaths to achieve a minimum minute ventilation. Ventilator breaths can be delivered with volume or pressure control. Advantages: Pt can breathe spontaneously, allows gradual weaning from ventilation. Disadvantages: Fatigue, chest wall/MSK disorders that compromise inspiratory strength, L ventricular dysfunction, ventilator dyssynchrony. Pressure-Support Ventilation (PSV): Ventilator supports each pt-triggered breath with set pressure; machine does not initiate breaths (prolonged periods of apnea will lead trigger safety-net ventilator-initiated breath). Can be used with CPAP for improved alveolar recruitment. Advantages: Can be used for pts who can spontaneously breathe but require intuba- tion (e.g. altered mental status, intra-op procedures where mechanical ventilation is not required), prior to extubation/transitioning from mechanical ventilation to spontaneous ventilation. Disadvantages: Not appropriate for unstable/fatigued/apneic pts. 22 COMPLICATIONS & EMERGENCIES AUTO-PEEP/DYNAMIC HYPERINFLATION Definition: Occurs when the lungs do not fully deflate and leads to air-trapping; this increases the dead space ventilation and V/Q mismatch. Signs/symptoms: Expiratory flow does not reach zero, ↓ BP, ↓ SpO2, ↓ ETCO2, wheezing. Complications: Hemodynamic instability, baro/volutrauma, ↑ work of breathing DDx: Bronchospasm (especially in asthma, COPD pts), pulmonary edema, pneu- mothorax, aspiration/ secretions, obstructed filters/tubing, ↑ RR. Risk factors: Asthma, COPD, short expiratory time in ventilatory settings. Management: Check for circuit malfunction, immediately disconnect pt from the ventilator and allow full expiration before reconnecting, ↓ tidal volume and ↑ I:E, treat underlying cause. MYOCARDIAL ISCHEMIA/INFARCTION Definition: Decreased blood flow to the heart from CAD or oxygen-demand mismatch leading to myocardial ischemia. Signs/symptoms: ST elevation/depression, unexplained ↑ HR or ↓ BP, arrhythmias, new Q waves, new LBBB. Complications: Cardiogenic shock, cardiac arrest. DDx: Cardiac tamponade, arrhythmia, PE. Risk factors: CAD/CHF and associated risk factors, vascular surgeries, major abdominal/ thoracic/ENT surgeries, significant bleeding. Prevention: Identify pts at risk, perform appropriate pre-op optimization, risk-stratify CVS complications, 5 or 12 lead ECG, consider invasive BP monitoring. Management: Varies significantly based on many factors such as reason for surgery/ urgency, type of surgery, pt condition and PMHx, timing and severity of ischemic event (e.g. before incision vs open abdomen), possible reasons for myocardial ischemia (and whether management would change), among others. General principles include maximizing myocardial oxygenation and decreasing demand. Consult cardiology for disposition and follow-up care if possible. Two very simplistic examples: e.g. ASA2, pre-incision, post-intubation, elective operation, new ECG changes  consult with cardiology, surgical team regarding best management plan (e.g. proceed or reschedule surgery, disposition) e.g. ASA5E, trauma surgery  pt would not survive without surgical intervention regardless; optimize myocardial and hemodynamic stability while minimizing surgical insult/time if possible. Management of acute ischemia/infarction most likely will occur after the surgery with cardiology in CCU/ICU. 23 The following material and images are adapted with permission from Dr David Parsons. THE ANESTHETIC MACHINE Accurately mixes air, oxygen, and anesthetic gases; scavenges/recycles unconsumed gases Delivers gases to the pt in a monitored and precise manner Enables various ventilation strategies Operates as a semi-closed circuit: Fresh gas flow enters the circuit from the wall supply and can be controlled by the anesthesiologist. The concentration and flow rate of the gases (oxygen, anesthetic gases) can be set separately (fresh gas control) or determined automatically by the machine if end-tidal concentrations are set (end-tidal control). Inspired concentrations of gases from the circuit is what is inhaled by pt. This is determined by addition of gases to the circuit (the concentration and flow rate of the fresh gas flow), and by the elimination of gases by the patient (i.e. utilization of O2, redistribution of anesthetic gases to body tissues). End-tidal concentrations of gases (CO2, anesthetic agents (i.e. MAC)) entering the circuit are measured in the pt’s exhalation. When fresh gas flow rate is high, the gas in the circuit will be similar to the fresh gas flows, since it equilibrates quickly. When the fresh gas flow rate is low, the gas concentrations in the circuit (thus the inspired concentration) may be quite different from the fresh gas flow since it may be consumed/eliminated by the pt faster than is being added to the circuit. Note: Depending on the machine model, the specific layout/components may vary. Components of the machine: (see labelled images following) Bellows: Pushes air through the circuit when the ventilator is ON. Some models may not have visible bellows. Ventilator switch: Turns ventilator on/off. May be integrated into the monitors on some machines. MAN/SPON (left) – Used for spontaneously breathing pts or when bagging manually. VENT (right) – Ventilator is on. Adjustable pressure-limiting (APL) valve: Controls the maximum circuit pressure when the ventilator is OFF (i.e. set to MAN/SPON). Spontaneously-ventilated pts: 0cm H2O Bagging by mask: 7, ETCO2 0.9) 5. Airway protection (obey simple commands, cough/gag reflex) 6. Other: stable acid-base, lytes, volume, temp Other considerations for extubation: Suction for secretions Bite block (to avoid pt obstructing tubing) Oropharyngeal airway if neeed Oxygen mask for transport and PACU COMPLICATIONS & EMERGENCIES General strategies for anticipated difficult intubation: Have a plan and be ready to call for help immediately; have backup equipment in room. Use an alternative anesthetic technique (i.e. regional, local) if appropriate. Perform awake intubation (pt maintains own airway until intubated). (See Vortex approach and ASA difficult airway algorithm.) Reasons for rapid deterioration/sudden cardiac arrest while intubated/ventilated: DOPES D - Displaced ETT O - Obstruction of ETT (secretions/mucous plug) P - Pneumothorax / PE E - Equipment failure S - Stacking breaths (hyperinflation in asthma/COPD pts) Diagnostic steps (process of elimination to determine source). Correlate clinically and with other monitors. 1. Turn FiO2 to 100%. 2. Switch off ventilator and initiate manual ventilation (equipment malfunction). 3. Inspect entire circuit from anesthetic machine to patient ETT (leaks, kinks). 4. Auscultate breath sounds bilaterally (pneumothorax, breath stacking). 5. Suction down ETT (secretions/mucous plug). 6. Disconnect ETT circuit (auto-PEEP; allow full exhalation). ANAPHYLAXIS Definition: A systemic allergic/hypersensitivity reaction to antigen leading to sudden release of inflammatory mediators by mast cell/basophil degranulation. Signs/symptoms: ↓↓ BP, ↑ HR, ↓ O2, ↓ ETCO2, high peak airway pressures, shark fin (obstructive) waveform on capnography, dyspnea/wheezing, rash/urticaria. Complications: Shock, cardiac/respiratory arrest. Potential antigens: NMBAs, abx, sugammadex, latex products, blood products, IV contrast. Management: Remove potential causal agents, epinephrine (10-100mcg IV bolus, increase dose q2min until clinical improvement), adequate fluid resuscitation, treat bron- chospasm (SABAs, 4-8 puffs), early intubation (if not already and signs of angioedema/ severe anaphylaxis), hemodynamic and ventilatory support and monitoring. 36 ASPIRATION Definition: Inhalation of gastric contents into the trachea and lung. Signs/symptoms: ↓ O2, ↓ HR, laryngospasm, bronchospasm. Complications: Chemical pneumonitis, pneumonia, empyema, ARDS, cardiac arrest. Risk factors: Emergency surgery, GERD, pregnancy, trauma, DM, recent food intake, bowel obstruction, obesity. Prevention: Abide by NPO guidelines, ↑ gastric motility (e.g. metoclopromide), ↓gastric acidity (e.g. ranitidine), prophylactic anti-emetics, RSI, NG tube. Management: Suction pharynx/trachea, R tilt to limit spread, 100% FiO2, CPAP/PEEP with lung protective strategies, bronchodilators; empiric abx NOT indicated unless signs of infection are evident. BRONCHOSPASM Definition: A reversible involuntary smooth muscle contraction in the bron- chi leading to narrowed airways mediated by vagal innervation. Signs/symptoms: ↓ O2, ↓ ETCO2, high peak airway pressures, shark fin (obstructive) waveform on capnography, dyspnea/wheezing, ↑ expiratory time, ↓ tidal volumes if pressure control ventilation. Complications: Breath stacking/auto-PEEP (bronchospastic pts who devel- op sudden ↓↓ BP may be air-trapping). Risk factors: Asthma, smoking, cold air, inhaled irritants, tracheal intubation/extubation. Prevention: Pre-op prophylactic SABA/steroids, adherence to COPD/asthma therapy, topical lidocaine, ensure adequate anesthesia during intubation/extubation. Management: 100% FiO2 with manual bag ventilation, change I:E ratio to allow for ade- quate exhalation, nebulized SABA (salbutamol, 6-8 puffs), IV steroids (e.g. methylprednis- olone 1mg/kg IV), deepen anesthetic (ketamine and sevo/isoflurane have bronchodilatory properties). LARYNGOSPASM Definition: Partial/complete airway obstruction from laryngeal closure reflex (despite inspiratory attempts) due to chemical or mechanical stimuli. Signs/symptoms: ↓ O2, ↓ HR, suprasternal indrawing, accessory muscle use, paradoxical breathing, stridor or silent chest. Complications: Negative pressure pulmonary edema, cardiac/respiratory failure. Risk factors: Pediatric pts, recent URTI, cigarette smoke exposure, emergency surgery, insufficient depth of anesthesia (higher risk during induction and emer- gence), oropharyngeal secretions. Prevention: Consider delaying elective surgery 2-3w after URTI, apply topical lidocaine, ensure adequate anesthesia before intubation, extubate when deep or fully awake. Management: Continuous positive airway pressure with 100% FiO2 with well-fitting mask and jaw thrust, suction secretions, deepen anesthetic with propofol, use paralytic (succi- nylcholine IV or IM), provide ventilatory support (consider reintubation if needed). 37 STATUS ASTHMATICUS Definition: Extreme asthma exacerbation that is unresponsive to SABAs. Signs/symptoms: ↓ O2, ↑↑ RR, ↑HR, prolonged expiration, stridor/wheeze/silent chest, accessory muscle use, suprasternal indrawing. Complications: Altered mental status, pneumothorax, cardiac/respiratory failure. Risk factors: PMHx hospitalization/ED for asthma, signs of inadequately-controlled asth- ma, URTI, cold air, inhaled irritants. Management: 100% FiO2, IV SABAs, IV steroids, IV magnesium sulfate, ketamine or sevo/isoflurane, Heliox, monitor lytes (K+) and fluids. (Intubation is often not required in status asthmaticus and irritates the airway; it is usually reserved for impending respiratory failure.) PNEUMOTHORAX Definition: Gas in the pleural space leading to compression/collapsing of the lung. Signs/symptoms: ↑ peak inspiratory pressures, ↓ O2, ↓ BP, ↑ HR, narrowed pulse pres- sure, decreased/asymmetrical breath sounds, tracheal deviation. Complications: Tension pneumothorax, cardiac/respiratory arrest. Risk factors: Trauma, COPD, spine or thoracic surgery. Management: Check for mainstem intubation, 100% FiO2, stat U/S for lung sliding or CXR, needle decompression if hemodynamically unstable, thoracostomy, watchful waiting/ supportive care if stable. CAN’T INTUBATE, CAN’T OXYGENATE Definition: A difficult airway that is unable to be intubated or ventilated by BMV. Signs/symptoms: Failed intubation and ventilation, ↓ O2, cyanosis, respiratory failure. Complications: Brain damage, death. Risk factors: Hx of difficult BMV/airway, predictors of difficult BMV/airway. Prevention: Identify at-risk patients, announce airway plan to team; have a Plan A (laryngoscopy), Plan B (alternate intubating technique), Plan C (supraglottic airway), Plan D (surgical airway) or wake pt if possible. Have all airway equipment available and ready. Management: Limit intubation attempts (usually 3 attempts to minimize airway trauma), optimize between attempts (e.g. change position, call for expert, change blade/device), attempt SGA insertion, optimize BMV, oral/nasal airway, surgical airway (cricothyrotomy). (See Vortex approach and ASA difficult airway algorithm.) 38 VORTEX APPROACH TO EMERGENCY AIRWAY MANAGEMENT “The Vortex implementation tool is based on the premise that there are only three upper airway ‘lifelines’ (non-surgical techniques) by which alveolar oxygen delivery can be es- tablished and confirmed: face mask, supraglottic airway and endotracheal tube. If a ‘best effort’ at each of these three lifelines is unsuccessful then a can’t intubate, can’t oxygenate situation (CICO) situation exists and ‘CICO Rescue’ (emergency front-of-neck access) must be initiated. “Completion of a ‘best effort’ at any of the three upper airway lifelines without being able to restore alveolar oxygen delivery mandates spiral movement inward towards the next lifeline. The circular arrangement of the three lifelines on the tool means that airway management can be initiated using any lifeline and proceed to the remaining ones in whatever sequence is judged most appropriate in the clinical circumstances. A list of five categories of optimisation, applying equally to each of the three lifelines, is provided to prompt consideration of the available options for maximising success during a best effort at any lifeline. “Completion of best efforts at all three lifelines without restoring alveolar oxygen delivery culminates in spiral movement to the centre zone of the tool, representing the need to initiate CICO Rescue. Conversely, confirmation of alveolar oxygen delivery using any of the three lifelines, results in outward movement into the circumferential ‘Green Zone’. The Green Zone prompts recognition of the opportunity to re-oxygenate, gather resources and develop a strategy, that arises whenever alveolar oxygen delivery is able to be established. The Green Zone is also visible in the centre of the tool to remind clinicians that, when all three lifelines have been unsuccessful, CICO Rescue also restores alveolar oxygen delivery and provides the same opportunities.” Read more at http://vortexapproach.org 39 ASA DIFFICULT AIRWAY ALGORITHM 40 References: Adriano, A., & Skanchy, J. (2018). 2018 CA-1 tutorial textbook (12th ed.). Retrieved from http://ether.stanford.edu/ca1_new/Final- 2018 CA-1 Tutorial Textbook.Smartphone or Tablet.pdf Barash, P., Cullen, B., Stoelting, R., Cahalan, M., Stock, M.C., Ortega, R., … Holt, N. (2017). Clinical anesthesia (8th ed.). Philadelphia: Wolters Kluwer Butterworth, J. F., Mackey, D. C., & Wasnick, J. D. (2018). Morgan & Mikhail’s Clinical Anesthesiology. New York: McGraw-Hill Education. Chrimes , N. (n.d.). The Vortex Approach. Retrieved from http://vortexapproach.org/ Miller, R. D., Cohen, N. H., Eriksson, L. I., Fleisher, L. A., Wiener-Kronish, J. P., & Young, W. L. (2015). Miller’s anesthesia. Philadelphia, PA: Elsevier/Saunders. OpenAnesthesia. (n.d.). Retrieved from https://www.openanesthesia.org Operating room crisis checklists [PDF document]. Retrieved from https://www.ariadnelabs. org/areas-of-work/surgery-or-crisis-checklists/resources/ Pardo, M., & Miller, R. D. (2017). Basics of Anesthesia (7th ed.). Elsevier Health Sciences. Practice Guidelines for Management of the Difficult Airway: An Updated Report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98(5):1269-1277. Raymer, K. (2012). Understanding anesthesia: A learner’s guide (1st ed.). McMaster University. Stanford Anesthesia Cognitive Aid Group (2016). Emergency Manual: Cognitive aids for perioperative critical events. Retrieved from http://emergencymanual.stanford.edu Sullivan, P. (2012). The Ottawa anesthesia primer. Toronto: Echo Book Publishing. 41  Fluid management and resuscitation Section reviewer: Gwen Lovsted Senior reviewer: Catherine Moores, MD Staff reviewer: Kevin Latchford, MD Knowledge-based objectives: Describe how you would assess a patient’s volume status. List potential sites for vascular access and complications associated with each site. Explain how euvolemia can be disturbed/altered in the preoperative period and how these alterations are managed. Describe appropriate uses for the following crystalloids: NS, RL, D5W, D5NS. Describe the rational use of blood product therapy. Explain the complications of massive transfusions. What information can be obtained from an arterial line? What happens when the arterial line transducer is too high or too low? Think of reasons you might decide to place an arterial line on a patient. Why are arterial lines sometimes done prior to induction and sometimes after induction? Describe the determinants of CO. Explain the relationship between myocardial oxygen supply and demand and how we can alter each aspect perioperatively. Define shock and explain how shock can be classified (type and degree). Describe potential treatments for the patient in shock, including the rational use of vasoactive and intrepid medications. Essential Clinical Encounters objectives: Think of the potential challenges the anesthesiologist encounters when formulating an anesthetic plan for a patient coming for an emergency procedure. How can the surgical team facilitate that process? Skills objectives: Prepare the equipment and supplies needed to insert an IV in an adult patient. Insert and IV in a conscious or unconscious adult patient or appropriate simulation device with minimal assistance. Determine the proper function of the IV line. Replace crystalloid solutions demonstrating sterile techniques and without air. Assess a patient’s fluid/volume status (using history, physical exam, available monitors and laboratory investigations). 42 DEFINITIONS Crystalloid: Solutions with electrolytes that expand overall extracellular volume. ~1/3 volume stays in intravascular space; ~2/3 redistributed to interstitial space. Normal saline (0.9% NS): Indications: Simple fluid replacement, use with blood products, hypoNa+, con- traction alkalosis, traumatic brain injury. Cautions/contraindications: Metabolic acidosis, hyperCl-, renal dysfunction Lactated Ringer’s (RL): Indications: Simple fluid replacement, less risk of metabolic acidosis/hyperCl-. Cautions/contraindications: Theoretical coagulation risk with blood products. Dextrose 5% (D5W): Indications: Give with insulin for ketoacidosis or hyperK+, hypoglycemia, hyperNa+. Cautions/contraindications: Uncontrolled DM, traumatic brain injury, hypoK+. Colloid: Solutions containing large-weight particles that exert oncotic pres- sure in the plasma. Used less often than crystalloids. Albumin: Indications: Severe malnutrition, hepatic failure, burns, intravascular volume depletion. Cautions/contraindications: Circulatory overload, renal dysfunction, severe anemia. Synthetic starches (dextran, hydroxyethyl starch): Indications: (Rare usage) Hypovolemia, shock. Cautions/contraindications: Coagulopathies (↓vWF, VIII), CHF, renal disease. May cause renal toxicity and affect hemostasis/coagulation even without prior disease. (mEq/L) Na+ K+ Cl- Lactate pH Osmolarity Physiologic ECF 140 4 103 100 7.4 295 (average) 0.9% NS 154 0 154 0 5.5 308 LR 130 4 109 28 6.5 273 5% albumin 130-16 45y. O- for F of childbearing age, pts 3s, dry mucous mem- branes/axilla, intense thirst. Labs: ↑ Hct, hyperNa+, ↑ BUN:Cr, ↑ Cr Hypervolemia Causes: AKI/CKD, cirrhosis, CHF, urinary tract obstruction Sign/symptoms: Pitting edema, stigmata of liver disease, ascites, crackles, wheez- ing, ↑ JVP Investigations: ↑ Pulmonary markings on CXR INTRAOPERATIVE VOLUME STATUS Consider: HR/BP trends Fluid balance: consider maintenance requirement, deficit, and replacement given; ins/outs prior to/during surgery INTRAOPERATIVE BP MANAGEMENT Classical management of intraoperative hyper/hypotension is to maintain BP within 20% of preoperative BP; however, some literature suggests that absolute BP limits may also be useful in preventing poor outcomes. ✷ Perfusion of organs generally requires MAP >65. However, must consider specific pt and procedure (e.g. BP cuff/arterial line transducer location relative to required surgical position, pts with chronic HTN, shifts in cerebral autoregulation). ✷ Always treat the underlying cause in addition to immediate temporary hemodynamic stabilization. CO = HR x SV (SV depends on preload, contractility, afterload) MAP = CO x SVR MAP ≈ 2/3 DBP + 1/3 SBP Pulse pressure = SBP - DBP Normal PP ≈ 40 at rest. Causes of widened PP (>40): aortic regurg, atherosclerosis, thyrotoxicosis, pregnancy, anxiety. Causes of narrowed PP (8, gag/cough/swallow intact)  if not, consider intubation ✷ Consider early intubation in pts with airway burns, oral trauma/bleeds, penetrating/ blunt neck trauma. Assume full stomach and use RSI if intubation is indicated Make plans for difficult/failed intubation B - Breathing and oxygenation Listen for bilateral breath sounds, inspect for chest rise, RR, colouring, monitor with pulse oximetry Inspect for open chest wounds, flail chest, unilateral chest movement, tracheal deviation Tension pneumothorax requires immediate needle decompression followed by chest tube placement 50 C - Circulation and hemorrhage control Control obvious hemorrhage Ensure IV access (two 14-16G peripheral catheters) Assess for circulatory compromise suggesting hemorrhagic shock: cool, mottled skin, weak pulses, hypotension, tachycardia Simultaneously assess and manage as necessary with fluid resuscitation and blood products Assess potential spaces for bleeding with POCUS: thoracic (cardiac tamponade, pleural effusion), abdominal, retroperitoneal/pelvic cavities For high volume transfusion, first rapidly infuse 1L warmed isotonic fluid followed by balanced transfusion (1:1:1 ratio for plasma:plts:pRBCs SNS overstimulation from injury may mask intravascular depletion D - Disability Rapid neurological assessment (PERLA, GCS) Assess for signs of basal skull fracture (raccoon eyes, Battle’s sign, otorrhea) Consider neurogenic shock E - Exposure Fully expose pt to complete inspection (complete log roll, maintaining C-spine precautions) Avoid hypothermia by using warm blankets or bair hugger, warm fluids Secondary survey: A full H&P after primary survey and adequate resuscitation is com- plete; pt must be hemodynamically stable. Assess particularly for trauma, MSK, neuro, chest and abdo. Inspect for signs of injury, stabbing or GSW, electrical entry/exit wounds Seat belt sign from MVC AMPLE Hx: A – Allergies M – Medications P – PMHx L – Last meal/NPO status E – Events Insert foley catheter to monitor fluid status if necessary (unless there is suspected urethral injury) Tertiary survey: 24h after initial presentation, reassess all results from H&P. Look at lab results, final imaging reports Look for any missed injuries, smaller injuries 51 MASSIVE TRANSFUSION The replacement of a pt’s total blood volume or 10u in Intercostal > Caudal > Epidural > Plexus (brachial) > Subcutaneous. Incidence ~0.04-1 in 1000. Signs/symptoms: CNS: Early: Tinnitus, blurred vision, slurred speech, dizziness, agitation, muscle twitching, seizures Late: Drowsiness, unconsciousness, apnea. CVS: Early: ↑ HR, ↑ BP Late: ↓↓ BP, ↓↓ HR (conduction block, long PR, wide QRS), ventricular dysrhyth- mias, cardiac arrest. DDx: Anaphylaxis, cocaine toxicity, tricyclic antidepressants, anxiety Prevention: Use minimum effective dose, aspirate prior to injection, incremental injections, added epinephrine may be warning, monitor pt and ask about symptoms. Management: Stop local anesthetic administration, treat seizures, 20% lipid emulsion infusion (Intralipid), hemodynamic and ventilatory support. HIGH REGIONAL BLOCK/TOTAL SPINAL Definition: Unintended spread of anesthetic affecting spinal nerves above T4; a total spinal is the intracranial spread of anesthetic. Symptoms usually show within 1-5min. Incidence ~1 in 4300. Signs/symptoms: Total spinal: Slurred speech, dizziness, rapid rising sensory block, loss of conscious- ness. C3-C5: Respiratory distress, ↓O2, symmetric shoulder weakness. C6-C8: Respiratory distress, symmetric arm/hand weakness, paresthesia. T1-T4: ↓ BP, ↓ HR, N/V. DDx: Isolated spinal hypotension, local anesthetic systemic toxicity. Prevention: Use low dose anesthetics and consider the level of block needed, aspirate before injection, consider giving epidurals in divided doses, inject slowly. Management: Stop neuraxial anesthetic administration, 100% FiO2 or RSI, left lateral tilt, monitor fetal HR, establish large bore IVs and temporize bradycardia/hypotension appro- priately, hemodynamic management and ventilation until block wears off. POST-DURAL PUNCTURE HEADACHE (PDPH) Definition: A headache due to leakage of CSF, intracranial hypotension, and venodilation from a puncture of the dura during a neuraxial technique. Symptoms typically self-resolve within 1-2wk. Incidence ranges from 2-10% depending on technique/needle in obstetric pts. 68 Signs/symptoms: Radiating dull headache (exacerbated by movement/sitting or standing, relieved by lying down), neck ache, backache, N/V, vertigo, dizziness, tinnitus, hearing loss. DDx: Intracranial hemorrhage/hematoma, migraine, tumour, meningitis, central venous thrombosis, non-specific headache. Prevention: Fine-gauge (25-27G) needles, pencil point tip, avoid inadvertent puncture of the dura (operator expertise). Management: Supportive therapy (e.g. bed rest, NSAIDs, rehydration), pharmacologic/ interventional therapy (caffeine, epidural blood patch). 69 References: Barash, P., Cullen, B., Stoelting, R., Cahalan, M., Stock, M.C., Ortega, R., … Holt, N. (2017). Clinical anesthesia (8th ed.). Philadelphia: Wolters Kluwer Butterworth, J. F., Mackey, D. C., & Wasnick, J. D. (2018). Morgan & Mikhail’s Clinical Anesthesiology. New York: McGraw-Hill Education. McNeill, M., DeTina, A., & Cordovani, D. (2018). Anesthesia for the obstetrical patient [E-module]. Retrieved from https://medportal.litmos.com/course/1715751. Miller, R. D., Cohen, N. H., Eriksson, L. I., Fleisher, L. A., Wiener-Kronish, J. P., & Young, W. L. (2015). Miller’s anesthesia. Philadelphia, PA: Elsevier/Saunders. OpenAnesthesia. (n.d.). Retrieved from https://www.openanesthesia.org Operating room crisis checklists [PDF document]. Retrieved from https://www.ariadnelabs. org/areas-of-work/surgery-or-crisis-checklists/resources/ Raymer, K. (2012). Understanding anesthesia: A learner’s guide (1st ed.). McMaster University. Stanford Anesthesia Cognitive Aid Group (2016). Emergency Manual: Cognitive aids for perioperative critical events. Retrieved from http://emergencymanual.stanford.edu Sullivan, P. (2012). The Ottawa anesthesia primer. Toronto: Echo Book Publishing. 70  Pediatric anesthesia Section reviewer: Jared Cohen Senior reviewer: Russell Lenferna, MD Staff reviewer: Amanda Whippey, MD Knowledge-based objectives: Describe the main physiologic differences between pediatric and adult patients and explain their implication on anesthetic management. Explain the fluid management issues of the pediatric patient. Calculate appropriate ETT size for pediatric patients. Essential Clinical Encounters objectives: NA Skills objectives: NA 71 ANATOMIC DIFFERENCES IN CHILDREN Area Anatomic changes Implication Head Larger occiput Sniffing position is often best achieved in neutral position or using a shoulder roll Epiglottis Shorter, floppier, omega- Larynx more cephalad (C3-4) shaped, angled over laryn- than adults (C5-6) geal inlet May use Miller (straight blade to directly lift epiglottis) instead of Mac blade Airway Narrower and shorter trachea Smaller ETT needed ↑ risk of endobronchial intubation Higher airway resistance = ↑ work of breathing and risk of fatigue More prone to obstruction ↑ airway reactivity Laryngospasm more common (3x more likely in neonates) Narrow subglottic region ETT should always be care- fully sized regardless of being cuffed/uncuffed to minimize occurrence of subglottic edema and postop stridor PHYSIOLOGIC DIFFERENCES IN CHILDREN System Physiological Implication/risks changes Cardiovascular Stiffer ventricles; Difficulty increasing stroke volume CO is dependent to compensate for ↓ HR leading on HR to ↓ BP ↑ vagal tone Typically ↓ HR in response to noxious stimuli (e.g. hypoxia, Immature sympathetic laryngoscopy) nervous systems (