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Kelly Shinkaruk, MD FRCPC HLT 123 October 17, 2009 1 Objectives What is anesthesia? Manual monitoring techniques Inspection Palpation Auscultation Evaluation and maintenance of anesthetic depth using Non-invasive monitors Invasive monitors Nervous system monitors Adjusting medications to maintain anesthetic 2 Objectives What is anesthesia? Manual monitoring techniques Inspection Palpation Auscultation Evaluation and maintenance of anesthetic depth using Non-invasive monitors Invasive monitors Nervous system monitors Adjusting medications to maintain anesthetic 3 What is anesthesia? “…drug induced reversible depression of the central nervous system resulting in the loss of response to and perception of all external stimuli.” Components of anesthesia Unconsciousness Amnesia Analgesia Immobility Attenuation of autonomic response to noxious stimulation 4 Components of General Anesthesia Induction Maintenance Emergence 5 Components of General Anesthesia Induction Maintenance Emergence 6 Goals of Maintenance Responsible for autonomic nervous system Maintenance throughout case of anesthesia amnesia analgesia paralysis (if indicated) In addition Minimize negative effects of anesthetic Fluid maintenance/balance/resuscitation Cardiac output and end organ perfusion 7 Goals of Maintenance Why use monitors? Detect deficit or overdose of anesthetic agents and resolve the aberrancy Early detection of adverse events Prevention of periop critical events Prior to advent of standard monitoring, anesthesia had very high morbidity and mortality Now it’s very low 8 CAS Monitors Required • • • • Pulse oximeter Blood pressure Electrocardiography Capnography, when endotracheal tubes or laryngeal masks are inserted • Agent-specific anesthetic gas monitor Exclusively Available • Apparatus to measure temperature • Peripheral nerve stimulator • Stethoscope • Appropriate lighting Immediately Available • Spirometry 9 CAS Monitors Use monitors to help narrow your differential diagnosis No single monitor can make a diagnosis, must verify one monitor with another! 10 Depth of Anesthesia If monitored vitals change Consider differential diagnosis Simultaneously manage and diagnose ABCs, verify result with another monitor Inspect, palpate, auscultate Make adjustments to medications as appropriate!!! 11 Objectives What is anesthesia? Manual monitoring techniques Inspection Palpation Auscultation Evaluation and maintenance of anesthetic depth using Non-invasive monitors Invasive monitors Nervous system monitors Adjusting medications to maintain anesthetic 12 Manual Monitoring Techniques “The only indispensable monitor is the presence, at all times, of a physician or an anesthesia assistant, under the immediate supervision of an anesthesiologist, with appropriate training and experience.” CAS guidelines 2008 Provides valuable information about Depth of anesthesia Diagnosis of intraoperative complications 13 Manual Monitoring Techniques Inspection (Adequate Lighting) Historically, sole monitor Initial information by observation Inspect for alterations Diaphoresis Spontaneous movement Respiratory rate and pattern esp. when spontaneous Abnormal retractions or indrawing Cyanosis JVP Skin colour and/or rash 14 Manual Monitoring Techniques Palpation Correlate information from inspection Physical contact with patient Palpate for Tracheal position Subcutaneous emphysema Pulsus paradoxus Heart rate, rhythm, contour 15 Manual Monitoring Techniques Ausculation (Stethoscope!!!) Respiratory system Endotracheal tube placement/malposition Wheezes/crackles stridor/decreased air entry Cardiovascular system Murmurs/bruits Changes in quality of heart sounds (S1, S2, decreased heart sounds) 16 Objectives What is anesthesia? Manual monitoring techniques Inspection Palpation Auscultation Evaluation and maintenance of anesthetic depth using Non-invasive monitors Invasive monitors Nervous system monitors Adjusting medications to maintain anesthetic 17 Non Invasive Monitors Pulse Oximetry Blood Pressure Capnography Expired Agents/Gases Non Invasive Monitors Ventilatory Pressures ECG Temperature Monitoring Respiratory Function 18 Non Invasive Monitors Pulse Oximetry Simple, noninvasive, continuous indirectly measures the oxygen saturation of a patient's blood Detect and prevent hypoxemia Affected by dyshemoglobins, vital dyes, nail polish, ambient light, motion artifact, background noise/electrocautery 19 Non Invasive Monitors Pulse Oximetry When sats fall, differential diagnosis Low FiO2 (relative or absolute) Inadequate alveolar ventilation V/Q mismatch Excessive metabolic O2 demand Low cardiac output Treatment? 100% O2 Increase ventilation rate/Vt or change vent mode Recruitment maneuvers 20 Non Invasive Monitors Blood Pressure (via cuff) Indicates adequacy of circulation Minimum monitoring interval - 5min Monitor location – upper arm, leg, forearm 21 Non Invasive Monitors Blood pressure Hypertension diagnosis? ○ ○ ○ Light anesthesia Catecholamine release Laryngoscopy Surgical stimulation Emergence from anesthesia Administration of vasopressors Treatment? ○ ○ Deepen anesthetic d/c vasopressors 22 Non Invasive Monitors Blood Pressure Hypotension differential diagnosis? Is extensive… Hypovolemia Relative overdose of anesthetic agents Treatment? Initially, go through ABCs, inspect for evidence of bleeding, 100%O2, turn down anesthetic Fluid bolus – NS/RL 500-1000mL Vasopressor – Phenylephrine 100mcg or Ephedrine 2-10mg 23 Non Invasive Monitors Electrocardiogram Three or five leads Continuous measurement of heart rate and rhythm Questionable indicator of myocardial ischemia Signs of light anesthesia tachycardia Might notice changes in rhythm Vasovagal episodes Tell surgeon to STOP!!! Atropine 0.4mg or Ephedrine 5-10mg 24 Non Invasive Monitors Expired Agents/Gases The most important objective indicator of depth of anesthesia Monitors the concentration of gas (volatile, CO2, O2) being expired from the patient MAC (minimum alveolar concentration) = 50% of people will not move with surgical stimulus Monitor end tidal concentration of agents 25 Non Invasive Monitors Expired Agents/Gases MAC is affected by many things Intravenous medications – PPF, opioids, benzos Pre-op medications – pregabalin, benzos Age Medical conditions/patient health Hypo/hyperthermia 26 Non Invasive Monitors Expired Agents/Gases If low and patient appears light Increase flow rate Increase percent of volatile delivered from vaporizer Make sure to monitor MAC as can increase rapidly! (and cause hypotension) 27 Non Invasive Monitors Capnography Insp/exp CO2 concentration Vital monitor of physiology Confirm ETT placement Recognize ETT malposition/extubation/disconnection Assess adequacy of ventilation/PaO2 Aids diagnosis of PE, partial A/W obstruction, RAD/bronchospasm Assess efficacy of CPR efforts 28 Non Invasive Monitors Increased ETCO2 Decreased ETCO2 Hyperthermia/Sepsis MH Hypothermia Shivering hypothyroidism Hyperthyroidism Hypoventilation rebreathing Hyperventilation Hypoperfusion Pulmonary embolism 29 Non Invasive Monitors Capnography If increased ETCO2 Check CO2 absorber! Increase minute ventilation (RR or Vt) ?hypermetabolic process? If decreased ETCO2 Sudden vs slow Decrease ventilation Verify other signs of hypoperfusion 30 Non Invasive Monitors Respiratory Function Especially useful in spontaneously ventilating patient Light patient Hyperventilation - increased RR/Vt and hypocapnia Breath holding Bronchospasm/laryngospasm Very deep patient Hypoventilation – decreased RR/Vt and hypercapnia 31 Non Invasive Monitors Increase in respiratory rate Differential mainly light anesthetic and hypoventilation Increase ventilation (RR or Vt) Deepen anesthetic Administer analgesic 32 Non Invasive Monitors Ventilator Pressures Early indication of light anesthetic and other problems! Always check: Breathing circuit ETT Pulmonary compliance Alarms for increased pressure Coughing Insufficient muscle paralysis Bronchospasm Obstruction/pt biting ETT 33 Non Invasive Monitors Ventilatory Pressure elevated Differential diagnosis Manage and diagnose Inspect patient and ETT – biting, blocked, disconnected (if low pressure alarm) Take off machine and verify compliance Auscultate breath sounds – ETT malposition Treatment Deepen anesthetic Paralysis Reposition/Suction/change ETT 34 Non Invasive Monitors Temperature Monitoring Can be monitored via bladder, distal esophagus, ear canal, trachea, nasopharynx, rectum Attempts made to maintain temperature as close to normothermia as possible Situations requiring temp monitoring ○ ○ ○ ○ Long cases Anticipated fluctuations in temperature Bair hugger Malignant hyperthermia patients 35 Invasive Monitors Central Venous Pressure Arterial Line Pulmonary Artery Catheter Echo Invasive Monitors 36 Invasive Monitors Arterial Line Continuous blood pressure measurement Placed in a peripheral artery Radial Brachial Dorsalis pedis Rarely femoral Waveform gives information about intravascular status Help with diagnosis of cardiac tamponade,etc 37 Invasive Monitors Arterial line Indications: induced hypotension, induced hypothermia, major cardiac/thoracic/vascular/neurosurgical procedures Always keep BP cuff in place for verification of arterial BP Used for frequent blood sampling esp. ABGs Be aware that tracing can be damped/positional Flattened waves might be artifactual Verify with BP cuff 38 Invasive Monitors Central Venous Pressure (CVP) Estimates of right atrial/ventricular pressures Serial measurements more useful than single value monitor intravascular volume/fluid status Renal failure patients Difficult IV access Anticipated need for vasopressor infusion/TPN/Hemodialysis Massive transfusion 39 Invasive Monitors 40 Invasive Monitors Pulmonary Artery Catheter (PAC) Rarely indicated, TEE rapidly replacing Inflation in pulmonary artery reflects left atrial filling pressure Can calculate cardiac output High risk of complications PA rupture PVCs/Vtach Hemo/pneumothorax 41 Invasive Monitors 42 Invasive Monitors Transesophageal Echo Echo probe placed in esophagus during GA Uses ultrasound technology Assess cardiac function/filling/valves Replacing PAC technology Requires special equipment 43 Invasive Monitors 44 Invasive Monitors Evaluation of Native valve disease Prosthetic heart valve function/dysfunction Cardiac masses The ICU patient with hemodynamic instability Congenital heart disease Thromboembolic risk in patient with atrial fibrillation and inadequate anticoagulation Detection of Aortic dissection Complications of endocarditis Potential etiologies of stroke Adjunct to Percutaneous cardiac procedures Cardiac surgical procedures 45 Invasive Monitors Heart valve repair Most congenital heart surgery requiring cardiopulmonary bypass Endocarditis, particularly with extensive disease or inadequate preoperative evaluation of disease extent Ascending aortic dissection repair when aortic valve involvement unknown Evaluation of life-threatening hemodynamic disturbances when ventricular function is unknown Heart valve replacement Removal of cardiac tumors Increased risk of myocardial ischemia or hemodynamic disturbances Intracardiac thrombectomy or pulmonary embolectomy Suspected cardiac trauma or for detection of foreign bodies Cardiac aneurysm repair Thoracic aortic dissection repair without suspected aortic valve involvement Pericardial window procedures Evaluation of anastomotic sites during heart and/or lung transplantation Hypertrophic obstructive cardiomyopathy repair Monitoring placement and function of assist devices 46 Nervous System Monitors EEG BIS Nervous System Monitors Evoked Potentials PNS 47 Nervous System Monitors Electroencephalogram (EEG) Represents spontaneous electrical activity of the cerebral cortex Measures amplitude and frequency of discharge Four frequencies: beta, alpha, theta, delta 48 Nervous System Monitors Electroencephalogram (EEG) EEG may be used to detect intraop cerebral ischemia Deep anesthesia and cerebral ischemia decrease or abolish normal alpha/beta; delta/theta predominate 49 Nervous System Monitors Bispectral Index (BIS) A variable derived from the EEG Measure of the hypnotic effect of anesthetic Gives a value between 0 and 100 Decreasing numbers = deeper anesthetic <60 appears to predict unconsciousness Used in trauma, crash OB, cardiac, unstable patient with minimal reserve/anesthetic 50 Nervous System Monitors Evoked Potentials Stimulation of neural structures to evoke responses to monitor integrity of pathways Brainstem Auditory Evoked Responses (BAER) – acoustic neuroma/post fossa Visual Evoked Potentials (VEP) – optic tract Somatosensory Evoked Potentials (SSEP) – stimulate peripheral nerves (median, ulnar, peroneal, posterior tibial), spine surgery (scoliosis) Motor Evoked Potentials (MEP) Facial Nerve Stimulation – parotidectomy Affected by many anesthetic agents 51 Nervous System Monitors Peripheral Nerve Stimulator (PNS) Monitors the depth of neuromuscular blockade and ease of reversibility Electrodes applied over peripheral nerve Ulnar nerve most common Facial nerve and common peroneal 52 Nervous System Monitors Peripheral Nerve Stimulator (PNS) Nerve stimulated and muscle contraction measured Train of Four most commonly measured Maintain one twitch during cases requiring paralysis Rocuronium most common Cisatracurium occasionally Pancuronium very rarely Succinylcholine for RSI Block easily reversible if >1 twitch present 53 Objectives What is anesthesia? Manual monitoring techniques Inspection Palpation Auscultation Evaluation and maintenance of anesthetic depth using Non-invasive monitors Invasive monitors Nervous system monitors Adjusting medications to maintain anesthetic 54 Maintenance Medications IV agents Propofol – the old standby, Vitamin P Light patient, administer 20-30mg bolus May need to repeat Be wary of decrease in BP Midazolam – amnestic Most often for awake patients Occasionally used for unstable patients on minimal maintenance meds 55 Maintenance Medications Analgesics Fentanyl – fast onset, short acting use when suspect patient light and experiencing pain If increased stimulation anticipated (new incision) may give bolus in advance 50mcg boluses Higher doses if patient ventilated and stable Morphine/Hydromorphone – slower onset, longer acting Often titrated to resp rate end of case 56 Maintenance Medications Volatiles (sevo and des) Usually the main maintenance medication In light patient Increase flow rates of O2/Air Increase concentration delivered from vaporizer In patient suspected to be too deep Increase flow rates but make sure to DECREASE vaporizer concentration (turn off) 57 Maintenance Medications Muscle Relaxants NOT anesthetic agents!!!! Do not give muscle relaxants to light patients without another medication Just think about how you’d feel if you were awake and couldn’t move or communicate!!! Very useful in conjunction with Propofol/Analgesics Rocuronium 10-20mg bolus 58 Maintenance Medications Fluids When patient has decreased BP, increased HR, decreased urine output Consider hypovolemia Bolus fluids rapidly and assess response May need a large bolus if patient significantly fluid avid 59 Maintenance Medications Emergency drugs Vasopressors if patient unstable, need to stabilize while confirming diagnosis Phenylephrine 50-100mcg bolus, 40mcg/min infusion Ephedrine 5-10mg bolus Norepi/Epi/Vasopressin YIKES! 60 Maintenance Medications Other meds If patient has epidural, consider increasing or decreasing infusion 61 Questions??? 62