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Temperature, SPO2, & Hemodynamic Monitors Kathleen Minott, DNAP, CRNA Outline ▪ NIBP ▪ ▪ ▪ ▪ ▪ Operating principles Equipment Advantages Disadvantages SPO2 ▪ ▪ ▪ ▪ ▪ ▪ Operating principles/physiology Equipment Sites Applications Advantages Limitations ▪ Temperature Control ▪ ▪ ▪ ▪ ▪ Monitoring Techn...

Temperature, SPO2, & Hemodynamic Monitors Kathleen Minott, DNAP, CRNA Outline ▪ NIBP ▪ ▪ ▪ ▪ ▪ Operating principles Equipment Advantages Disadvantages SPO2 ▪ ▪ ▪ ▪ ▪ ▪ Operating principles/physiology Equipment Sites Applications Advantages Limitations ▪ Temperature Control ▪ ▪ ▪ ▪ ▪ Monitoring Technologies Monitoring Sites Hazards Warming Devices Hazards to patient warming Noninvasive Blood Pressure (NIBP) Bladder within BP cuff should have a width 40 – 50% of circumference of limb Manual reading = estimated systolic (SBP) and diastolic BP (DBP) Mean arterial pressure (MAP) = [SBP +2(DBP)]/3 Standard q 5 min NIBP NIBP ▪ For every 10 cm of vertical height above or below the heart, 7.7 mm Hg must be added or subtracted from the measurement ▪ Should never be applied over superficial nerve, bony prominence, or joint ▪ Watch out for petechiae, skin breakdown ▪ Contraindications - trauma, AV fistula, PICC line ▪ Relative contraindication - IV NIBP Advantages Disadvantages ▪ Automaticity ▪ Complications ▪ Simplicity ▪ Unsuitable situations ▪ ▪ Noninvasiveness ▪ ▪ No extensive training or maintain ▪ ▪ Less expensive Reliability Patient Discomfort ▪ ▪ Not appropriate for detecting rapid changes Prolonged cycle time Clinical limitations ▪ ▪ ▪ extreme heart rate and blood pressure conditions Arrhythmias Excessive patient movement, ambulance, helicopter Pulse Oximetry ▪ Functions with 2 wavelengths of light ▪ 660 nm = red light absorbed by deoxyhemoblogin (deHgb) ▪ 940 nm = infrared light absorbed by oxyHgb ▪ Beer-Lambert law ▪ Accuracy of 2 – 4% ▪ Accuracy affected by: ▪ Ambient lights, cautery, anemia, dyes, movement, hypothermia, hypotension, scars, nail polish/artificial nails, skin thickness ▪ Detects SaO2, NOT PaO2 Reflectance Pulse Oximetry Pulse Oximetry ▪ Many read averages over a period of time ▪ Longer times may be more accurate ▪ Shorter times may reflect changes quicker ▪ Monitor for oxygenation, desaturation, monitor peripheral circulation, avoid hyperoxemia, monitor BP ▪ Tone – loud enough to hear clearly – Standard of care ▪ Alarms – high & low Plethysmograph https://media.springernature.com/lw685/spr ingerstatic/image/art%3A10.1186%2Fcc341/Media Objects/13054_1999_Article_380_Fig3_HTML. jpg?as=webp Pulse Oximetry ▪ Advantages: ▪ ▪ accuracy not affected by volatiles, dysrhythmias, fast response time, noninvasive, continuous, indicates perfusion, does not require eyes on it, wide variety of probes/ sites Disadvantages: ▪ Poor function with poor perfusion, difficulty detecting high oxygen partial pressures, delayed hypoxic event detection, mispositioned probe, low sats, interference, motion artifact ▪ May need to be covered to protect from ambient light Pulse Oximetry ▪ Measures percentage of O2 saturation of Hgb, but other types of Hgb can impact accuracy ▪ ▪ ▪ Carbon monoxide = sats can be 100% and pt will be hypoxic Methemoglobinemia = sats 85% Sulfhemoglobinemia ▪ Severe anemia can overestimate SpO2, especially at lower saturations ▪ Sickle cell patients may have inaccurate readings ▪ Dyes: indigo carmine, lymphazurin, nitrobenzene, indocyamine green, methylene blue ▪ Underestimates SpO2 (falsely low reading) Temperature ▪ AANA Standard 9d: Thermoregulation When clinically significant changes in body temperature are intended, anticipated, or suspected, monitor body temperature. Use active measures to facilitate normothermia Temperature Monitoring ▪ National Institute for Clinical Excellence recommends at a minimum 1 hour before induction, every 30 minutes intraoperatively, and every 15 minutes in PACU ▪ PQRS outcome measure for all undergoing general or neuraxial anesthesia lasting ≥ 60 minutes, requiring at least one “body temperature” ≥ 35.5°C measured within the interval from 30 minutes before to 15 minutes after the anesthesia end time ▪ By remaining normothermic: ▪ Decrease infection ▪ Decrease bleeding ▪ Decrease myocardial ischemia ▪ Reduced shivering ▪ Normal drug duration of action ▪ Decreased PACU comfort Temperature ▪ During general anesthesia - initial rapid decrease of approximately 0.5 to 1.5°C over first 30 min, then a slow linear reduction of about 0.3°C per hour ▪ Methods of Heat Loss ▪ Radiation – amount of body exposed to environment – loss of heat to the environment ▪ Largest loss ▪ Conduction - direct contact of body tissues or fluids with a colder material ▪ Evaporative - latent heat of vaporization of water from open body cavities and the respiratory tract ▪ ▪ Sweating Convection - loss of heat to air immediately surrounding the body Cutaneous Warming ▪ Increase room temp (esp. Pediatrics, burns, trauma, transplants) ▪ ▪ 23oC for adults, 26oC for peds Limit skin exposure with blankets, plastic drapes, "space blankets" Temperature: Warming Patient ▪ Heating/humidification of inspired gases ▪ Head covering ▪ Fluid Warmers – IVF, blood ▪ Only raises 0.5oC; does prevent further decreases Active Warming Skin surface warming – forced air warmers Circulating water warmer Carbon fiber and carbon polymer heating mattresses Forced air warmers ▪ Large volume of air blown over an electrical element. ▪ Range of temp settings, even to cool ▪ Prevent heat loss by radiation; transfer heat by convection ▪ ▪ Can increase temp 0.75°C per hour Most commonly employed warming device - cost & efficient Temperature Monitoring ▪ Mercury Thermometer ▪ One of oldest, simplest devices ▪ 3 –5 minutes ▪ Must be cleaned and sterilized between patients Thermistors ▪ Disposable, efficient, accurate, and inexpensive ▪ metal-oxide semiconductors that depend on thermally excited electrons as charge carriers and have a strong temperature-dependent conductivity determined by the concentration of charge carriers ▪ Immune from interference ▪ Does require outside power source ▪ Inexpensive, stable, accurate within 0.1 - 0.2oC Thermocouple ▪ Thermocouples - junctions of two different metals in an electrical circuit. ▪ Typically use copper-constantan (copper with 40% nickel) junctions. This combination produces a small temperature-dependent voltage most easily measured with an amplifier. ▪ Probes are less expensive, available in very small sizes. ▪ Stable and accurate to 0.1°C. ▪ can be disposable Liquid Crystal Thermometers ▪ Apply to skin ▪ Use cholesteric liquid crystals ▪ Can be large discrepancy between skin & core temp ▪ Many disadvantages Infrared thermometer ▪ Noninvasive, quick ▪ Collects radiation emitted by a warm object ▪ Ear, Forehead ▪ Used in PACU, not OR Zero-Heat Flux Thermometers ▪ measure tissue temperature approximately 1–2 cm below skin surface ▪ Insulator probe is covered with heater to prevent heat flow through insulator ▪ found to correlate with pulmonary artery temperature Ingestible Telemetric Sensor ▪ patient ingests a silicon-coated “pill’ ▪ micro-battery, quartz crystal, communication coil, and circuit board encapsulated in medical-grade epoxy material ▪ crystal sensor vibrates at a frequency relative to body temperature, producing a magnetic flux and transmitting signals by radio waves to external receiver. ▪ Good correlation with core temp Bladder temperature ▪ Correlates well with core temperature ▪ Easily measured with combination Foley catheter-thermistor probe devices ▪ Extremely dependent on urine flow ▪ Bladder temperature is close to core temperature when urine flow is high, but correlates poorly with core temperature when flow is low