Anesthesia Monitoring in the Operating Room and ICU

Anesthesia Monitoring in the Operating Room and ICU Dr. Mahmoud Al-mustafa

Monitoring in the Past

Monitoring in the Past n n n Visual monitoring of respiration and overall clinical appearance Finger on pulse Blood pressure (sometimes

ASA Monitoring Guidelines n STANDARD I Qualified anesthesia personnel shall be present in the room throughout the conduct of all general anesthetics, regional anesthetics and monitored anesthesia care.

ASA Monitoring Guidelines n STANDARD II During all anesthetics, the patient’s oxygenation, ventilation, circulation and temperature shall be continually evaluated.

Oxygenation Ensure adequate oxygen concentration in inspired gas and blood Methods § § § inspired gas oxygen analyzer with alarms (GA) pulse oximetry exposure to assess color

Pulse Oximetry q Theory § two wavelengths (660 and 960 nm) § calculates functional saturation (physiologic saturation) q Limitations § dyes or other hemoglobin species (carboxy, met, fetal, etc) § motion § low perfusion states § electrocautery § ambient light

Pulse Oximetry q Optical plethysmography § detects pulsatile changes in blood volume q Spectrophotometry § measures pulsatile hemoglobin saturation q Assumptions § all pulsation is arterial § light passes through pulsatile beds

Ventilation n Objective n n ensure adequate ventilation of patient Methods qualitative clinical signs Ø Ø Ø chest excursion observation of reservoir bag auscultation of breath sounds quantitative measurement Ø Ø Ø end tidal carbon dioxide volume of expired gas continuous circuit disconnect monitor for mechanical ventilation

Ventilation q General Anesthesia § qualitative clinical signs adequate § quantitative methods encouraged § endotracheal tube or laryngeal mask placement Ø § continual end tidal carbon dioxide identification continuous disconnect alarm mandatory during controlled ventilation q Regional Anesthesia and Monitored Anesthesia Care § continual qualitative clinical signs (minimum)

Capnography q Theory § main or sidestream sampling § several technical methods available q Applications § confirmation of intubation § monitoring for circuit disconnection § identification of airway obstruction § rebreathing/metabolic monitoring

Circulation q Objective § ensure adequacy of circulatory function q Methods § continuous electrocardiogram monitoring § arterial blood pressure and heart rate q 5 min § during GA one additional continual parameter

Temperature q Objective § aid in maintaining appropriate body temperature q Application § readily available method to continuously monitor temperature if changes are intended, anticipated or suspected q Methods § thermistor § temperature sensitive chemical reactions § location

Monitoring Temperature n n n Potential heat loss or risk of hyperthermia necessitates continuous temperature monitoring Normal heat loss during anesthesia averages 0. 5 - 1 C per hour, but usually not more that 2 - 3 C Temperature below 34 C may lead to significant morbidity

Monitoring Temperature n n n Hypothermia develops when thermoregulation fails to control balance of metabolic heat production and environment heat loss Normal response to heat loss is impaired during anesthesia Those at high risk are elderly, burn patients neonates, spinal cord injuries

Monitoring Temperature n n Hyperthermia Causes Malignant hyerthermia Endogenous pyrogens Excessive environmental warming Increases in metabolic rate secondary to: Thyrotoxicosis n Pheochromocytoma n

Monitoring Temperature Monitoring Sites n n n Tympanic Esophagus Bladder Rectum Blood (PA catheter) Skin

Noninvasive Blood Pressure q Methodology § § § oscillometric algorithms automated reproducible q Limitations § cuff size Ø oversize erroneously low measurements Ø to small erroneously high

Electrocardiogram q 3 vs. 5 electrode system § three versus seven leads for diagnostic purposes q Heart rate measurement § R wave counting (any lead) q Ischemia Monitoring § lead II and V 5 are 90% sensitive § lead II, V 5 and V 4 up to 98% sensitive q Arrhythmia monitoring § lead II or esophageal for supraventricular arrhythmias § all leads for ventricular arrhythmias

Neuromuscular Function Evaluation of Reversal of Blockade q. Clinical Criteria § head lift > 5 seconds § sustained hand grip § negative inspiratory force Ø at least -55 cm. H 2 O for adults Ø at least -32 cm. H 2 O for children § vital capacity 15 ml/kg § absence of nystagmus or diplopia

Invasive monitoring n n n Arterial line Central venous pressure Pulmonary artery catheterization

Arterial Line n Indications: n n n Rapid moment to moment BP changes Frequent blood sampling Circulatory therapies: bypass, IABP, vasoactive drugs, deliberate hypotension Failure of indirect BP: burns, morbid obesity Pulse contour analysis: SPV, SV

Radial Artery Cannulation n Technically easy Good collateral circulation of hand Complications uncommon except: n n vasospastic disease prolonged shock high-dose vasopressors prolonged cannulation

Alternative Sites n Brachial: n n Use longer catheter to traverse elbow joint Postop keep arm extended Collateral circulation not as good as hand Femoral: n n Use guide-wire technique Puncture femoral artery below inguinal ligament (easier to compress, if required)

THE ARTERIAL WAVEFORM

Central Venous Line n Indications: n n n n CVP monitoring Advanced CV disease + major operation Secure vascular access for drugs: TLC Secure access for fluids: introducer sheath Aspiration of entrained air: sitting craniotomies Inadequate peripheral IV access Pacer, Swan Ganz

Central Venous Line: RIJ n n n n IJ vein lies in groove between sternal + clavicular heads of sternocleidomastoid muscle IJ vein is lateral + slightly anterior to carotid Aseptic technique, head down Insert needle towards ipsilateral nipple Seldinger method: 22 G finder; 18 G needle, guidewire, scalpel blade, dilator + catheter Observe ECG + maintain control of guide-wire Ultrasound guidance; CXR post insertion

Advantages of RIJ n n n Consistent, predictable anatomic location Readily identifiable landmarks Short straight course to SVC Easy intraop access for anesthesiologist at patient’s head High success rate, 90 -99%

Types of Central Catheters n n Variety of lengths, gauges, composition + lumens depending on purpose Introducer sheath (8 -8. 5 Fr): n Permits rapid fluid/blood infusion or Swan Trauma triple-lumen (12 Fr): n Rapid infusion via 12 g x 2; 16 g for CVP monitoring MAC 2: (9 Fr): n Rapid infusion via distal port; 12 g for CVP n Also allows for Swan insertion n More septations + stiffer plastic

Alternative Sites n Subclavian: n n External jugular: n n n Easier to insert v. IJ if c-spine precautions Better patient comfort v. IJ Risk of pneumo- 2% Easy to cannulate if visible, no risk of pneumo 20%: cannot access central circulation Double cannulation of same vein (RIJ) n Serious complications: vein avulsion, catheter entanglement, catheter fracture

CVP Monitoring n n n Reflects pressure at junction of vena cava + RA CVP is driving force for filling RA + RV CVP provides estimate of: n Intravascular blood volume n RV preload Trends in CVP are very useful Measure at end-expiration Zero at mid-axillary line

CVP Waveform Components

Pulmonary Artery Catheter n n n Introduced by Swan + Ganz in 1970 Allows accurate bedside measurement of important clinical variables: CO, PAP, PCWP, CVP to estimate LV filling volume, + guide fluid / vasoactive drug therapy Discloses pertinent CV data that cannot be accurately predicted from standard signs + symptoms

Complications n n n Minor in 50%, e. g. , arrhythmias Transient RBBB- 0. 9 -5% n External pacer if pre-existing LBBB Misinformation Serious: 0. 1 -0. 5%: knotting, pulmonary infarction, PA rupture (e. g. , overwedge), endocarditis, structural heart damage Death: 0. 016%

Summary n Invasive monitoring routinely performed n n n Permits improved understanding of BP, blood flow, + CV function Allows timely detection of hemodynamic events + initiation of treatment Requires correct technique + interpretation Complications occur from variety of reasons Risk: benefit ratio usually favorable in critically ill patients

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