BASIC PRINCIPLES OF ANESTHESIA P H A R M AC O L O G Y WHAT IS ANESTHESIA? A purposefully induced physiologic state in which the patient is rendered “without feeling” Anesthetics have effects on the spinal cord, the cerebral cortex, and the reticular activating system (RAS) in the brain stem ANESTHESIA WITHOUT SENSATION A state of controlled, temporary loss of sensation or awareness that is induced for medical purposes It may include analgesia, muscular paralysis, amnesia, and unconsciousness Volatile Inhalation anesthetics (sevoflurane, desflurane) Potent narcotics (fentanyl, hydromorphone (dilaudid), sufentanil, remifentanil) Analgesics (acetaminophen (Tylenol), aspirin, ketorolac, celecoxib (Celebrex), anticonvulsants-gabapentin) Benzodiazepines (midazolam, diazepam) Local anesthetics (lidocaine, bupivacaine) IV sedative hypnotic agents (dexmedetomidine (Precedex), ketamine) Induction drugs (diprivan (Propofol), etomidate) Neuromuscular blocking agents (succinylcholine, rocuronium) Adjunct drugs (antiemeticsondanseteron/zofran, PPI’spantoprazole/protonix) • General anesthesia (GA) or general endotracheal anesthesia (GETA) • Total intravenous anesthesia (TIVA) ANESTHETIC TECHNIQUES • Monitored anesthesia care (MAC) • Local with sedation (L&S) • Conscious sedation • Neuraxial also referred to as regional anesthesia (RA) (spinal or epidural) • Peripheral nerve blocks (PNB’s) LEVEL OF CONSCIOUSNESS • Level of consciousness (LOC) and the presence of protective airway reflexes determines the type and “depth” of anesthesia, differentiates between degrees of sedation and general anesthesia • The unconscious patient is unable to protect themselves from aspirating stomach contents (loss of gag reflex) placing them at risk for aspiration pneumonia (mortality rates 21-30%) • With decreased LOC patient is likely to hypoventilate and is at risk of airway obstruction and respiratory arrest • The patient rendered unconscious is also likely to have fluctuations of heart rate and blood pressure What does NPO mean? GENERAL ANESTHESIA • A combination of medications administered to produce a state of unconsciousness with a loss of protective airway reflexes, providing amnesia, analgesia, and immobility • Combination of agents are used to achieve a state of general anesthesia: inhalation anesthetics (gas vapors) delivered through the anesthesia machine breathing circuit, intravenous agents (propofol and ketamine), potent narcotics (fentanyl, dilaudid), and neuromuscular blocking agents/paralytic drugs (vecuronium, rocuronium) • Requires a secured airway to control ventilation and prevent aspiration GENERAL ENDOTRACHEAL ANESTHESIA (GETA) ANESTHESIA MACHINE REGIONAL ANESTHESIA NEURAXIAL • Drugs administered into the spinal space or the epidural space to block sensory and motor innervation from the spinal cord at the level of injection and distally (lower half of the body) • Drugs used include local anesthetics (lidocaine, bupivacaine) and narcotics (fentanyl, morphine) • Ex. Cesarean section, total knee replacement NEURAXIAL PERIPHERAL NERVE BLOCKS • The administration of local anesthetic to nerves innervating a particular area of the body. Blocks sensory and motor innervation. • Drugs administered typically local anesthestic (bupivacaine) • Ex interscalene nerve block provides anesthesia to the arm Peripheral nerve block Abdominal wall T6-L1 Ultrasound guided technique Last 18-24 hrs approx. SEDATION • Drugs administered to relieve anxiety and provide pain relief • Conscious---light--moderate---deep--unconscious • Drugs typically administered for sedation include versed, fentanyl, propofol, precedex, lidocaine, ketamine ANESTHESIA • Anesthetic agents have an additive effect with the majority of drugs leading to varying degrees of dose dependent myocardial and respiratory depression • Maintain physiologic homeostasis and hemodynamic stability through oxygenation, ventilation and perfusion in the anesthetized patient • Deliver oxygen, provide adequate ventilation, administer fluid and blood therapy, manipulate the physiology of the ANS, administration of cardiac and vasoactive medications, alter the neuromodulation of pain, mitigate the stress response to surgery • Provide optimal conditions for the surgeon while providing patient safety, comfort, while preventing iatrogenic harm • Preoperative phase of care; assessment and planning, informed consent PHASES OF ANESTHESIA CARE • Intraoperative phase of care; administration of anesthesia, case management : Induction---maintenance--emergence • Postoperative phase of care; recovery from anesthesia, management of side effects and pain management • Perioperative refers to care surrounding surgery and procedures • The anesthesia technique is determined by the invasiveness of the planned procedure • Consideration is given to the patients age, comorbidities or coexisting diseases • Elective versus emergency surgery CHOICE OF ANESTHESIA TECHNIQUE • Required position for the procedure • Duration of the procedure • Anticipated recovery length/disposition • NPO status/full stomach • Airway evaluation/anticipated difficult airway • Surgeon, patient and anesthesia provider preference MONITORING • All anesthetized patients require monitoring: ECG, BP, Capnography (etCO2 monitor), SpO2 (pulse oximeter), and temperature • All patients require adequate IV access for the purpose of delivering fluid, administering drugs and resuscitation if needed. PHARMACOLOGY • Pharmacology is a branch of science that deals with the study of drugs and their actions on living systems - that is, the study of how drugs work in the body • Pharmacokinetics (PK) refers to the movement of drugs through the body. PK describes a drug's exposure by characterizing absorption, distribution, bioavailability, metabolism, and excretion as a function of time • Pharmacodynamics (PD) refers to the body's biological response to drug, receptor, potency, response curves • Agonist a substance which initiates a physiologic response when combines with a receptor • Antagonist a substance that competes/interferes or blocks the physiologic action of another BENZODIAZEPINES • Benzodiazepines have anxiolytic, sedative, hypnotic, amnestic, and anticonvulsant properties in the CNS • Raise the level of the inhibitory neurotransmitter GABA in the brain • Diazepam (valium), lorazepam (ativan), and midazolam (versed) are three of the most important class members in the practice of anesthesia. • Alprazolam (xanax) and Clonazepam (klonopin) are also commonly prescribed benzo’s for treating anxiety VERSED Supplied: 1mg/ml in 2 or 5ml vials Rapid onset (1-5 min) with relatively short duration (highly lipophylic) max effect 20-60 min, recovery time 2-6 hrs Minimal respiratory depression Dose: adult sedation 1-5mg IV, decrease dose in patients with hepatic or renal impairment IV administration requires specialized care setting/monitoring Reverse with Flumazenil (Romazicon) 0.2mg IV, q 1 min x4 doses OPIOIDS NARCOTICS • Also known as “opioids,” the term “narcotic” comes from the Greek word for “stupor” and originally referred to a variety of substances that dulled the senses and relieved pain • “narcotic” refers to opium, opium derivatives, and their semi-synthetic substitutes. • A more current term for these drugs, is “opioid.” Examples include heroin and pharmaceutical drugs like OxyContin,Vicodin, codeine, morphine, methadone, and fentanyl Adverse Physiologic Effects of Opioids • Ventilatory depression • Muscle rigidity OPIOIDS • Nausea, vomiting • Puritis • Ileus • Hyperalgesia • Tolerance • Addiction FENTANYL CITRATE Brand: Sublimaze Class: Synthetic opioid, 100x more potent than morphine Supplied: 50 mcg/ml in 2 or 5ml vial, po, parenteral, transmucosal, transdermal Opioid agonist used with general, regional and spinal anesthesia, acute and chronic pain management Strong agonist at mu and kappa opiate receptors, mediates analgesia through the perception of pain Rapid onset, relatively short duration 50-100mcg bolus doses IV Respiratory depression Reversed with naloxone (Narcan) 0.4-2mg IV, IM, or SC up to total of 10mg HYDROMORPHONE • Brand: Dilaudid, Class: semisynthetic opioid agonist (oral, rectal, SC, IM & IV), • IV use for immediate release of moderate to severe pain: po extended release for continuous therapy for chronic pain • Rapid onset, dosing for acute pain management, 0.2, 0.5, 1.0 mg IV bolus. • Respiratory depressing effects, decrease HR & BP • Immediate availability of airway support • Reverse with narcan INDUCTION AGENTS • General anesthesia is a medically-induced loss of consciousness with concurrent loss of protective reflexes due to anesthetic agents • Induction of anesthesia can be accomplished through inhalation of gas through a face mask but is commonly achieved through the administration of IV induction agents • An induction dose of an anesthetic drug will render the patient unconscious and apneic requiring airway management and control of ventilation • Induction agents include propofol, etomidate, methohexital, ketamine PROPOFOL • Brand: Diprivan, Class: IV anesthetic • Most common induction agent used, also used in ICU for sedation in mechanically ventilated patients • Sedation, Hypotension, Apnea, • Antiemetic properties • CNS depression decreases CMrO2 and CBF • Supplied: 10/mg/ml in 20,50, or 100 ml glass bottles • Rapid onset with rapid clearance (highly lipophilic) • IV bolus dose 1.5-2 mg/kg, followed by infusion 100-200 mcg/kg/min for GA • ICU sedation range 25-50 mcg/kg/min PROPOFOL INFUSION SYNDROME • Propofol infusion syndrome (PRIS) is a rare syndrome which affects patients undergoing long-term treatment with high doses of the anesthetic and sedative drug propofol. It can lead to cardiac failure, rhabdomyolysis, metabolic acidosis, and kidney failure, and is often fatal • Certain risk factors for the development of propofol infusion syndrome are described, such as appropriate propofol doses and durations of administration, carbohydrate depletion, severe illness, and concomitant administration of catecholamines and glucocorticosteroids • Brand: Brevital, Class: Barbiturate; reduces neuronal activity, CNS depressant, potentiates GABA METHOHEXITAL SODIUM • Used alone as an anesthetic for short procedures that are relatively painless, as an induction agent, or as an adjunct drug. Used in ECT therapy • Rapid onset and ultra short acting (highly lipophilic) Induction dose 1-1.5 mg/kg • Respiratory depression, use with extreme caution in patients with coexisting pulmonary disease ETOMIDATE • Brand: Amidate Class: sedative hypnotic IV anesthetic, CNS depression • Rapid onset and recovery (highly lipophilic) • Supplied 2mg/ml solution in 10 ml single use vials • Dose: 0.2-0.6 mg/kg for induction • Useful due to minimal cardiac and respiratory depression, preserves HR & BP • Adrenocortical suppression KETAMINE HYDROCHLORIDE • Brand: Ketalar Class: Non barbiturate sedative hypnotic • Produces intense analgesia but not amnestic, produces a dissociative state • Eyes open, reflexes and airway intact, preserves HR & BP, cerebral vasodilator, causes increase in secretions • Inhibits the (N-methyl-D-aspartate) NMDA receptor • Similar in structure and action of PCP (phencyclidine) • Supplied 10, 50, or 100 mg/ml vials • Dose: 1-4.5 mg/kg IVP • Alpha-adrenergic agonist (activates alpha CNS receptors) • Hypnotic & analgesic effects • Decreases BP, HR • Minimal respiratory effects • IV infusion • Short term sedation in ICU or adjunct to general anesthesia (GA) • ETOH Withdrawal – adjunctive treatment with benzodiazapine Sevoflurane Desflurane NMB’s are skeletal muscle relaxants for intravenous (IV) administration indicated as an adjunct to general anesthesia, to facilitate tracheal intubation, and to provide skeletal muscle relaxation during surgery or mechanical ventilation Classified as depolarizing or non- depolarizing based on their mechanism of action depolarizers and non-depolarizers Depolarizing - Succinylcholine Brand: Anectine Supplied: 20 mg/ml in 10 ml vials Intubating dose: 1.5-2ml/kg Mimics acetylcholine Rapid onset ~ 30-60 sec (paralysis) Ultra short acting, rapidly metabolized Negative Side effects: • Fasciculation – myalgia • Cardiac dysrhythmia-Hyperkalemia • Increased ICP • Malignant hyperthermia Malignant hyperthermia (MH) is a type of severe reaction that occurs in response to particular medications used during general anesthesia, among those who are susceptible. Hypermetabolic state with calcium release into muscles. Symptoms include muscle rigidity, high fever, and a fast heart rate. Complications can include muscle breakdown and high blood potassium The classic signs of MH include hyperthermia to marked degree, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response Triggered by volatile inhalation anesthetics and succinylcholine RX: discontinue agent, hyperventilate, cool the patient, support hemodynamics (HR & BP support) Dantrolene: (Dantrium, Ryanodex, Revonto) is used to treat the reaction by stopping the release of calcium into the muscle Nondepolarizing- Rocuronium Bromide Brand: Zemuron Supplied: 10 mg/ml in 5 0r 10 ml vials Intubating dose: 0.4-0.6 mg/ml Competes with acetylcholine (postjunctional receptors) Skeletal muscle paralysis (without depolarization) Different onset depending on the dose, slower rate of recovery, metabolism Effects of these drugs monitored during anesthesia Non-depolarizing muscle relaxants can be reversed LOCAL ANESTHETICS “ L O S S O F S E N S AT I O N I N A D I S C R E T E R E G I O N O F T H E B O DY ” • Local anesthetics work by moving inside of the cell membrane and binding to the Na+ channel, blocking the influx of ions, stops the conduction of the nerve impulse and prevents further signals from reaching the brain. Two different classes due to molecular structure: Amides – Lidocaine, Mepivacaine, Bupivacaine, Ropivacaine Esters - Procaine, Chloroprocaine,Tetracaine • Blocking of Na ion flux through plasma membrane • pH of tissue matters • Not an all-or-nothing phenomena LOCAL ANESTHESIA Different sensory or motor blockade Drug deposited around the nerve/s Additive: Epinephrine (typical 5mcg/ml = 1:200 000) decrease breakdown through vasoconstriction Adverse effects – systemic toxicity!! LAST Early: lips tingling, circumoral numbness, hypotension……… • CNS - seizures • Cardiovascular collapse (bupivacaine) • Allergic reactions Treat with infusion of intralipids and hemodynamic support SPINAL OR EPIDURAL ANESTHESIA What’s the difference and why should you care? SPINAL ANESTHESIA Complications: • Less time to perform rapid onset • Hypotension • Better quality of sensory and motor anesthesia • High spinal • Commonly used during c-section, urologic procedures etc • Bradycardia • Post–dural puncture headache (PDH) • Backache • Urinary retention EPIDURAL ANESTHESIA • Advantages: • less hypotension than spinal • ability to prolong the anesthesia through an in dwelling catheter • option to use catheter for post op pain management POSTANESTHESIA CARE • Pain control (pain scales) • Mild to moderate Oral medications/ IV medications Agonist-antagonists NSAIDS • Moderate to severe Parenteral or intraspinal opioids Regional anesthesia Nerve blocks • Pre-emptive Analgesia POSTANESTHESIA CARE Most frequently encountered PACU complications: Need for airway support Hypotension/hypertension PONV Dysrhythmias Altered mental status REPORT & HANDOFF Patients name and age Surgical procedure and anesthesia used Drugs used Preop vital signs Coexisting medical diseases Allergies Estimated blood loss (EBL) Urinary output (UO) Fluid replacement Special instructions Pain management CXR/ Labs AIRWAY MANAGEMENT: SUPPLEMENTAL OXYGEN DELIVERY DEVICES • Nasal cannula • 1L-6L or 24-40 % (R/A = 21%) • FiO2 increases about 4% w/ each liter O2 AI RWAY M AN AG E M E N T: S UP P L E ME NTAL OX YG E N D E L I VE RY D E V I CE S • Simple mask Oxygen flow usually 6-8 L FiO2: 0.40-0.50% • Venturi mask (Entrapment Device) • FiO2: 24-28-35-40-50% AI RWAY M AN AG E M E N T: S UP P L E ME NTAL OX YG E N D E L I VE RY DEVI CES • Partial Rebreather Mask, 8-11 liters FiO2: 50-75% FiO2 • Non-Rebreather Mask 12-15 liters 80-100% FiO2 One-way valve device Highest amount FiO2 delivery POSTANESTHESIA CARE • Discharge Criteria • Determination made by anesthesia dept. • 0bserved for 20-30 minutes post last dose of narcotics • Easily aroused • Full orientation • Ability to maintain and protect airway • Stable vital signs for 15-30 minute • No obvious surgical complications • Regional discharge criteria Secondary but important Controlled post operative pain Controlled PONV Normothermia POSTOPERATIVE NAUSEA AND VOMITING (PONV) Direct relationship between the incidence of PONV and the duration of surgery and anesthesia. • Important patient outcome • Patients report PONV as worse than postop pain • Unanticipated delay in recovery, hospital admission • Prevention includes pretreatment, selection of anesthetics less likely to cause N&V • Antiemetics perioperative (Zofran & Decadron) with rescue plan in PACU • Multiple classes of antiemetics are recommended for high risk patients undergoing high risk procedure procedures Drug Duration Side Effects Route Onset 5-HT3-receptor antagonist IV IM PO/ODT 10 min 41 min – 1 24 h HA, lightheadedness abdominal pain constipation Promethazine Phenergan Phenothiazine IV IM/PO/PR 5 min 20 min 4–6 4–6 h Dry mouth, blurred vision Metoclopramide Substituted benzamide IV IM PO 1–3 min 10–15 min 30–60 min 4 1–2 h EPS, drowsiness, lassitude Patch 4–24 h 1 Ondansetron Class Doses in 24 h Zofran Reglan Transdermal scopolamine Anticholinergic Zofran®, Anzemet®, Phenergan®, Compazine®, Reglan®, and Transderm Scop® prescribing information. HA = headache; EPS = extrapyramidal symptoms. Zofran and Compazine are registered trademarks of GlaxoSmithKline. Anzemet is a registered trademark of Aventis Pharmaceuticals Inc. Phenergan and Reglan are registered trademarks of Wyeth Pharmaceuticals. Up to 24 h Dry mouth, post surgery drowsiness