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Obstetric Pediatric Cardiothoracic Neuro Outpatient surgery Ketamine clinic Office Based Pain management Critical care History 1864 Morton delivered the first ether anesthetic WW2 is when more modern day practices were established Alice Magaw is known as the 1st nurse anesthetist Consid...

Obstetric Pediatric Cardiothoracic Neuro Outpatient surgery Ketamine clinic Office Based Pain management Critical care History 1864 Morton delivered the first ether anesthetic WW2 is when more modern day practices were established Alice Magaw is known as the 1st nurse anesthetist Considerations Influencing Anesthetic Technique Patient safety Patient comfort Provider Preference Coexisting disease Surgical site Positioning Elective vs Emergence Airway Duration of surgery Patient age Recovery time PACU discharge criteria of facility Ideal Anesthetic Technique Optimal patient safety Patient satisfaction Excellent operating conditions for surgeon Allows for rapid recovery Avoid postoperative side effects Low cost Early transfer or discharge from PACU (costs) Types of Anesthesia General Anesthesia Care Definition Drug induced depression of the CNS resulting in the loss of response to perception of all external stimuli ASA continuum of sedation "is a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation" General Anesthetic Types Inhalation only typically used in pediatric cases Intravenous only (TIVA) used in neuro-monitored cases Combination Inhalation/IV most common --- induction with IV & maintenance with inhalation Components of anesthetic state Unconsciousness no measurement --- only inference through EEG & BIS monitoring Amnesia typically achieved with the use of benzodiazepines Analgesia not always required, i.e. cases with local blocks Immobility does not paralysis, simply means no longer responsive to stimuli Attenuation of autonomic responses to noxious stimuli Phases of General Anesthesia Induction Definition administering anesthetic drugs (Inhaled of IV) to induce a state of anesthesia inducing a state of unconsciousness Typically called "Induction of General Anesthesia" Pre-Induction Monitors routine monitoring includes EKG, NIBP, pulse-ox, CO2, temperature standard monitors should be used as minimum standard for **all anesthetic techniques** AANA Standard IX / ASA Standard II held to these standards regardless of location within the hospital Special monitors Arterial lines when a consistent and continuous monitoring of BP is needed CVP when there is a risk for bleeding or CVP value is needed to guide intra-op fluid management Other examples: BIS, cerebral oximeter, TEE, SWAN, flo-trac, etc Pre-Induction Pre-oxygenation The percent of O2 at room air is 21% Oxygen application prior to the initiation of induction sequence should be performed Purpose - to replace nitrogen in patients functional residual capacity (de-nitrogenation) Why? Buys us time as providers to secure airway and reduce apnea Have patient breath 100% oxygen via face mask (ensure seal) for a period of 3-5 minutes OR instruct patient to take 8 vital capacity breaths **Intravenous Induction of Anesthesia** A single ideal intravenous anesthesia induction drug has yet to be developed Desirable properties for induction agents: Rapid and smooth onset and recovery Analgesia Minimal cardiac and respiratory depression Antiemetic actions Lack of toxicity or histamine release Advantages pharmacokinetics and pharmaceutics IV induction produces a rapid onset of unconsciousness Commonly used anesthetic drugs: Propofol (most commonly used) sedative hypnotic (GABA) Thiopental (barbiturate) Brevital (barbiturate) Commonly used in electro-convulsion therapy as it does not effect the seizure threshold Etomidate sedative hypnotic (GABA) Ketamine (IV/IM) NMDA receptor antagonist - dissociative Opioids Benzodiazepines Generally used for adult patients or patients with a preexisting IV Choice of agent used dependent upon patient comorbidities and situational needs **Standard Induction Sequence** Room setup & Perform machine check Confirm checklist "sam tide" Suction, airway, machine, tape, IV, drugs, equipment Apply monitors Position patient Baseline vital To provide reference, possible stop point prior to proceeding Pre-oxygenation Administration of induction agents (IV/Inhalation/Combination) Eyelid reflex = protective reflex Mask ventilation Neuromuscular blocking agent IF you are planning to use an LMA or perform a MASK case --- no paralytics will be given Airway instrumentation **Rapid Sequence Induction of Anesthesia** "Intravenous injection of anesthetic to produce unconsciousness followed immediately by a neuromuscular blocking drug that produces rapid onset of skeletal muscle paralysis" Room setup & Machine check Confirm checklist "samtide" Suction, airway, machine, tape, IV, drugs, equipment Apply monitors Position patient Baseline vitals To provide reference, possible stop point before proceeding Pre-oxygenation Administration of induction agents (IV/inhalation/combo) Cricoid pressure applied prior to loss of consciousness Used to close the esophagus to lessen the chance of aspiration --- pressure should be maintained until confirmation of CO2 detection for 3 consecutive breaths Eyelid reflex Neuromuscular blocking agent Airway instrumentation - always ETT What situation would necessitate an RSI? Full stomach or any other concern for aspiration Weight-loss drugs that cause delayed gastric emptying Acute abdomen --- appendicitis, bowel perf, small bowel obstruction **Inhalation Induction** Most common method for inducing children in North America who are scheduled for an elective case Why? No IV, pt uncooperative, less traumatic Also known as mask induction Oxygen + volatile agent or oxygen + nitrous oxide + volatile agent Nitrous speeds up the onset of volatile agent Volatile anesthetics: Isoflurane (lipid soluble & slow) Desflurane (irritating) Sevoflurane (most common, non-pungent and non-irritating) Steps: Prime circuit Monitors (pulse ox is most important) Mask application - administration of O2/sevo or O2/N2O/sevo Loss of consciousness Maintain ventilation Remain VIGILANT by monitoring for adequate ventilation (whether spontaneous or controlled) PIV placement +/- IV induction +/- paralytics Airway instrumentation (LMA/ETT) Verify placement **Post-Standard Induction** Assess LOC and loss of lid reflex Tapes eyes closed Provide positive pressure ventilation Via face-mask Asses ease/difficulty of ventilation Can determine extubation technique Maintain oxygenation = LIFE +/- administration of paralytics Airway instrumentation Laryngeal mask airway (no paralytic) Endotracheal tube Endobronchial tube (one lung ventilation) DO NOT perform post induction ventilation during RSI Maintenance Defined as "the management of physiological function and the maintenance of surgical anesthesia following induction and until emergence" Goals - maintain surgical anesthesia, maintain physiologic homeostasis, monitoring is needed to ensure that these goals are met Requires Vigilance Provide: Unconsciousness, amnesia, analgesia, immobility, muscle relaxation, and control of the sympathetic nervous system response to noxious stimuli Valley of Anesthesia - the time after induction but before incision Accomplished by a combination of drugs Inhaled and IV - with or without neuromuscular blocking agents (procedure dependent) Drugs administered on basis of specific goal relevant to pharmacologic effect Prevention of intraoperative awareness **Maintenance of Physiologic Homeostasis** Maintain euvolemia for normotensive patients Patients with long standing uncontrolled HTN will require higher MAP --- goal in to keep MAP within 20% of baseline Fluid management: Traditional vs Goal Directed Replace fluid: NPO, bowel prep? Monitor/chart/estimate and replace blood loss Monitor urine output Titrate, administer, and redose medications as necessary Maintain positioning and monitor pressure points Nerve injury prevention Maintain and monitor adequacy of ventilation Prevent hypothermia Maintenance monitoring **Stay vigilant** of oxygenation, vitals signs, anesthetic depth, level of muscle relaxation, positioning'' **Stages of General Anesthesia** (Intro to Anesthesia Ch 16) Stage I: Analgesia Begins with administration of induction agents Ends with loss of consciousness ness Patients response to pain is altered Encompasses all staged of sedation up to general anesthesia Stage II: Delirium Begins with loss of consciousness Period of involuntary movement Signs: Irregular respirations Periods of apnea, breath holding Dilated pupils and divergent gaze Tachycardia Hypertension Delirium This stage is usually skipped in IV induction Most important during emergence --- NEVER pull tube during stage 2 (highest risk for laryngospasms) Stage III: Surgical Anesthesia Begins with onset of regular breathing Ends with loss of spontaneous respirations Deep sleep not subject to rousing Consists of four planes Most surgical procedures can be safely performed in planes 1 and 2 Plane 1 - loss of lid reflex, respirations regular and deeper than normal pupils reactive, swallowing, retching, vomiting reflexes disappear and reappear in that order, respiratory response to skin incision is decreased, decreased muscle tone Plane 2 - starts when eyeballs become concentrically fixed, regular respirations with decreased tidal volume, respiratory response to skin incision disappears, moderate loss of muscle tone, reflex closure of vocal cords begins to disappear, pupils unreliable Plane 3 - begins with decrease in inter-coastal muscle activity, ends with inter-coastal activity absent and respirations is completely diaphragmatic, diaphragmatic breathing (can be seen as jerking movement), pupils continue to dilate Plane 4 - begins with complete loss of inter-coastal activity, ends with loss of spontaneous respiration, pupils completely dilated, non responsive to light, all muscle tone lost Stage IV: Overdose AKA respiratory paralysis Cessation of respiration due to concentration of anesthetic agent Ends with circulatory collapse Should be lightened IMMEDIATELY Emergence "Is a transition process where a patients goes from general anesthesia to awake and spontaneously breathing" Critical period of recovery from general anesthesia with the return of: Consciousness Neuromuscular conduction Airway protective reflexes A plan for emergence should begin on first patient contact and be developed based on the patient's commorbidities and surgeon's needs **Preparation** Estimate remaining duration of surgical procedure Decrease anesthetic depth (if planning for awake extubation) Assess level of paralysis TOF/Acceleromyography Administer reversal When appropriate for procedure (deep fascia closed) TOF of at least 2, preferably 3-4 twitches Adequate recovery from NMBA should be established prior to extubation, TOF ratio \>90% --- after reversal Awareness possible --- in awake extubation Administer medication to prevent PONV Pain management Opioids Requirements based upon patient weight, procedure, physiological status, and opioid tolerance Respiratory rate can be a useful indicator of adequate analgesia Diffusion hypoxia Occurs when N2O has been used N2O diffuses rapidly from blood into alveoli replace with RA if no on 100% O2 Administer 100% O2 for 5-10 minutes to prevent hypoxia Suction oral/pharyngeal cavity Place oral pharyngeal or nasal pharyngeal airway **Evaluation of signs and stages of anesthesia during emergence** Stage III - deep extubation Stage II - excitement DO NOT EXTUBATE Irregular breathing Possible agitation High risk for laryngospasms and regurgitation Stage I - awake extubation **Awake Extubation Criteria** If high risk for aspiration or difficult intubation --- only extubate the patient when fully awake Patent must be conscious and responding to simple commands such as "open you eyes" or "squeeze my hand" Ensure adequate reversal of NMBA The ability to perform basic actions are not reliable assurance of NMBA recovery --- make the patient left their head off the table and hold it Must be hemodynamically stable and normothermic Adequate spontaneous ventilation with a regular rate, RR \>8 and TV \> 6-8 ml/kg **Deep Extubation Criteria** Chosen when the presence of an ETT is to be avoided during emergence to prevent bucking and straining (open belly/big abdominal surgeries) Anesthetic Stage III Adequate reversal of NMBA Hemodynamically stable and normothermic Adequate spontaneous ventilation with regular rate, RR\>8, and TV 6-8 ml/kg Technique - maintain anesthetic depth, suction airway, place OPA, assess for breath holding, extubate, place face-mask to assess for continued adequate ventilation Monitored Anesthesia Care (MAC) Monitored Anesthesia Care does not describe the continuum of depth of sedation, rather it describes "a specific anesthesia service in which an anesthesiologist has been requested to participate in the care of a patient undergoing a diagnostic or therapeutic procedure" If the patient **loses consciousness and the ability to respond purposefully**, the anesthesia care is a general anesthetic, irrespective of whether airway instrumentation is required. **All monitoring standards must be maintained** The provider of monitored anesthesia care must be prepared and qualified to convert to general when necessary May require varying levels of sedation, analgesia, and anxiolytics Desired end points to provide comfort, maintain cardiopulmonary stability, improve operating conditions and prevent recall of. Unpleasant perioperative events Ideally patient should be able to communicate during the procedure Therapy should be administered to treat pain, anxiety, and agitation Combination of local/MAC are common **During monitored anesthesia care the anesthesia provider performs a number of services** Diagnosis and treatment of clinical problems that occur during the procedure Support of vital functions Administration of sedatives, analgesics, hypnotics, anesthetic agents, or other medication as necessary for patient safety Psychological support and physical comfort Provision of other medical services as needed to complete the procedure safely Local anesthetic Which drug Characteristic Recommended dose Max dose Concentrations With/without preservatives **Who is not a good candidate??** Children, confused, uncooperative, unable to follow commands, patients with tremors, patients who are unable to lie flat "An analysis of the ASA Closed Claims Project database focusing on MAC likewise revealed that over-sedation and respiratory collapse most frequently led to claims **To avoid be VIGILANT, have airway equipment present & be prepared to convert to general** ASA Publication on Sedation Minimal sedation (anxiolytics) A drug-induced state during which patients respond normally to verbal commands Cognitive function and physical coordination may be impaired --- airway, reflexes, ventilatory, and cardiovascular functions are unaffected Moderate sedation/Analgesia (Conscious Sedation) Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation No interventions are required to maintain a patent airway and spontaneous ventilation is adequate. Cardiovascular function is usually maintained Reflex withdrawal from a painful stimuli is NOT considered a purposeful response Deep sedation/analgesia Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated of painful stimulation. The ability to independently maintain ventilatory function may be impaired May require assistance in maintaining a patent airway and spontaneous ventilation may be inadequate Cardiovascular function is usually maintained Monitoring should be on dedicated limbs ETCO2 can be monitored via NC, however ETCO2 does not measure quality of ventilation in an open system --- need a sealed mask to adequately monitor ventilation INTRODUCTION TO REGIONAL ANESTHESIA History The original application of modern local anesthesia is credited to Carl Koller, who demonstrated topical anesthesia of the eye with cocaine in 1884 In late 1884, William Halstead used cocaine for intradermal infiltration and nerve blocks including facial nerve, brachial plexus, pudendal and posterior tibial nerve Spinal anesthesia is credited to Augustus Bier and Theodore Tuffier who in 1898 injected cocaine into the spinal column as a surgical anesthetic technique NEUROAXIAL ANESTHESIA definitions placement of local anesthetic adjacent to the spinal cord Local anesthetics work by blocking signals to and from the nerve --- act through sodium channels to interrupt conduction of the nerve fiber Can be used with or without general anesthesia (spinals are more likely to be used as primary mode of anesthesia) Performed as a single injection (typically spinal) or with a catheter to allow intermittent boluses or continuous infusions (epidural) **Role in Practice** Many operations performed below the neck can be performed under neuroaxial anesthesia --- except those operations that have the possibility of impairing ventilation and that may require an ETT Why use regional? It has been shown that general anesthesia patients have a greater percentage of adverse in-hosptial outcomes than those that received neuroaxial anesthesia Used in a variety of cases, also used to treat acute and chronic pain Typically used as primary mode of anesthesia in procedure performed below the umbillcus **Advantages** --- in relation to general anesthesia Studies have shown regional anesthesia to: Decrease intraoperative blood loss Decrease incidence of venous thrombosis & pulmonary embolism Decrease cardiac complications (high risk patients) Decrease bleeding & transfusion requirements Increase vascular graft patency Earlier return of GI junction/lower incidence of postoperative ileus Reduction of parenteral opioid requirements Blunt the body's stress response to surgery Spinal advantages takes less time to perform than epidurals; more rapid onset, associated with less pain during procedure ANATOMY VERTEBRAL COLUMN (Nagelhout p 677-679) Composed of vertebral bones (33) and intervertebral disks (24) that connect the vertebrae anteriorly Vertebrae (33) 7 cervical 12 thoracic 5 lumbar 5 fused sacral 4 fused coccyx Provides structural support for the body, protection for the spinal cord and nerves, and allows mobility Anteriorly --- concave in thoracic and sacral vertebrae (primary curvature formation that is developed in-utero) & convex in cervical and lumber regions (secondary formation from bearing of weight) Abnormal curvatures Scoliosis - lateral curvature (most common) Kyphosis - excessive posterior curvature (thoracic hump) Lordosis - excessive hollowing of the lumbar vertebrae Kyphoscoliosis - concomitant lateral bending and rotation of the vertebral column It is important to determine if the patient has a history of abnormal curvatures or perform an adequate assessment to identify Vertebral body is supported anteriorly and posteriorly by longitudinal ligaments Supported posteriorly (dorsal) by Supra-spinous ligament Interspinous ligament Ligament flavum Final barrier to a needle before it enters the spinal canal (vertebral foramen) Tougher than the interspinous ligament and east to identify with an epidural needle VERTEBRA Vertebral foramen stacked vertically forms the vertebral column (spinal canal) Features: Large anterior cylindrical vertebral body Vertebral Foramen can be defined as: Anteriorly by vertebral body Laterally by pedicles (2), transverse processes (2), superior articular process & mammillary process, inferior articular process Posteriorly by lamina (2) & spinous process Articular processes are covered in hyaline cartilage because they articulate (touch) other bones creating a facet joint C2-C6 have a bifid spinous process, C7 is normal  LUMBAR THORACIC  SACRUM & COCCYX CERVICAL SPINAL CANAL & SPINAL CORD Spinal canal contains the spinal cord with its coverings (meninges), fatty tissue, and venous plexus Meninges (3 layers) --- pia mater (innermost), arachnoid mater, and dura mater (outermost) Cerebral spinal fluid is found between the pia and arachnoid mater in the subarachnoid space which is continuous with the brain The spinal cord extends from the foramen magnum to the level of L1 in adults and L3 in children (bc the vertebral column growth is more rapid that the spinal cord) Miller "spinal cord ends at the lower border of L1 in adults Nagelhout "from medulla oblongata to the level of L2 vertebra, below L2 in 1% of adults and rarely to L3" Needle puncture below L1 usually avoids potential trauma to the spinal cord There are 31 spinal nerves: 8 Cervical - C1-C7 nerves will exit above it's corresponding vertebrae, C8 has to exit below 12 Thoracic 5 Lumbar 5 Sacral 1 Coccyxgeal Spinal enlargements of the spinal cord are found in certain areas Cervical (C4-T1) --- nerves for upper extremities Lumbar (L2-S3) --- nerves for lower extremities MENINGES Protective covering for the spinal cord and nerve roots Non-nervous - no conduction Dura Mater Outermost layer Composed of dense fibrous tissue with few elastic fibers Attached superiorly to the foramen magnum & inferiorly at its ends at the S1 or S2 vertebra Latin for "tough mother" Arachnoid Mater Closely adherent to the thicker & denser dura mate Thin, spiderweb like covering forming the middle layer Beneath this layer is the subarachnoid space (CSF is found here) Pia Mater Innermost layer Thin and in direct contact with the outer surface of the spinal cord SPINAL CORD AND SPINAL NERVES The end of the spinal cord tapers to the canus medullaris and nerve pathways continue in a collection of rootlets called the cauda equina "horse's tail" contained within the lower dural sac (L1-L5) The filium terminale (an extension of the pia mater) penetrates the dura and extends to the periosteum of the coccyx to create a tether Anterior and posterior nerve roots at each level join and exit the spinal canal through the intervertebral foramina to form the spinal nerve Spinal nerves: Cervical region exit above the corresponding vertebrae except cervical nerve 8 (exits below C7 vertebra) --- Starting at T1 they exit below their corresponding vertebrae Dural sac and subarachnoid space usually extends to S2 in adults and often S3 in children **Dorsal & Ventral Nerve Roots** Anterior/Ventral root is responsible for motor (efferent) & Posterior/Dorsal root carry sensory (afferent) The roots conjoin as they exit the vertebral foramen to create the spinal nerves Local anesthetics exert action on the nerve roots as they exit the cord affecting both sensory and motor "Because the spinal cord ends at L1, lower lumbar and sacral nerve extend for some distance within the spinal canal as the cauda equina before exiting the intervertebral foramina to the sacral epidural space" All spinal anesthetics are placed below L1 into the dural sac at the level of the cauda equina Epidural anesthetics can be placed as any level of the vertebral column (aside from the sacrum) SPACES Epidural space A potential space outside the dural sac but inside the vertebral canal Contains epidural veins, fat, lymphatics, segmental arteries and nerve roots Bordered by the dura anteriorly and the ligamentum flavum posteriorly Often described as a "discontinuous space" (contact may be interrupted) Largest at the midline of the lumbar region (3-5mm) --- thoracic (2-3mm), cervical (1.5-2mm) Subarachnoid space Continuous with the central canal of the spinal cord and the ventricles of the brain Filled with CSF Epidural neuroaxial anesthesia The administration of local anesthetic solution in the space outside of the dura layer (i.e. epi-dura) can be approached at any spinal level --- even cervical (higher the level = higher the risk = more precision required) Spinal neuraxial anesthesia Local anesthetic solution is injected into the subarachnoid space and is always approached below the level of L1 Blocks neural conduction in the nerve roots in the area of its spread in the cerebrospinal fluid LAYERS When a needle is advanced from a posterior approach from skim the spinal cord the layers are: Skin Subcutaneous tissue Supra-spinous ligament Interspinous/Intra-spinous ligament Ligamentum flavum Epidural space --- STOP HERE FOR EPIDURAL Dura mater Subdural space Arachnoid mater Subarachnoid space --- STOP HERE FOR SPINAL Pia mater Spinal cord Distance from skin to epidural space is between (2.5-8 cm) --- on average about 5 cm BLOOD SUPPLY 3 arteries that supply the spinal cord (2 posterior, 1 anterior) Anterior artery is the primary blood supply to the lower 2/3 of the spinal cord The great ventral radicular artery (Artery of Adamkiewicz - T8-T11) is the main blood supply to the anterior spinal artery (do not stop/alter blood flow here) If blood flow is interrupted, anesthetic can be interrupted MECHANISM OF ACTION Principle site of action for neuraxial blockade is the nerve root Spinal Anesthesia LA is injected into the CSF Allows for relatively small dose (\ pooling -\> decreased venous return -\> decreased cardiac output Blocks above T4 result in: Direct interruption of cardiac accelerator fibers which arise at T1-T4, when blocked may cause bradycardia Sympathetic blockade is unavoidable & can ultimately lead to cardiac arrest SPINAL BLOCK Also known as subarachnoid blockade LA injected into the subarachnoid space & mixes with CSF Usually administered as a single injection Onset of action/blockade is almost immediate NEEDLES Pencil point tips Less traumatic - will spread fibers Sprotte & Whitacre Cutting point tips More traumatic - will cut fibers Quincke & Atraucan Large gauge = Less traumatic High risk for posterior puncture HA: \