M&M NonCardiac Monitoring Flashcards
Mandatory monitor for any anesthetic, including moderate sedation, no contraindications
pulse oximetry
Where is the pulse ox sensor applied?
A sensor with a light source and detector is placed across the tissue, that can be transilluminated.
Oxygenated hgb absorbs more
Infrared light (940nm)
Deoxygenated hgb absorbs more
RED light (660 nm)
What is the basis of oximetric determinations?
Change in light absorption
How does the pulse oximetry?
Microprocessor analyzes the ration of red to infrared absorptions. to provide O2 saturation.
Pulse ox , arterial pulsations, identified by
Plethysmography, allows for correction for absorption by nonpulsative venous blood and tissue.
Clinically detectable cyanosis requires
5 g of desaturated hgb and corresponds to an SPO2 of less than 80%
Usually goes undetected by pulse ox in the absence of lung disease or low FiO2
Bronchial intubation
Methemoglobin has the
Same absorption coefficient at both red and infrared wavelengths.
Red and infrared with methemoglobin absorps in what ratio?
1:1
1:1 absorption ration seen with methemoglobin corresponds to a saturation reading of
85%
Things causes pulse ox artifact.
Methylene blue dye
low perfusion
malpositioned sensor
leakage of light from the light emiting diode to the sensor.
What is required to obtain mixed venous blood oxygen saturation
Pulmonary artery catheter with fiberoptic sensor to determine SvO2
Noninvasive brain oximetry
monitors regional O2 saturation of Hg in the brain.
In contrast to pulse ox, brain oximetry measures
Venous
Capillary
Arterial saturation
thereby providing oxygen saturation of all regional hemoglboin
What can dramatic decrease regional oxygen saturation (rSO2)
Cardiac arrest
Cerebral embolization
Deep hyothermia
Severe hypoxia
Capnographs rely on the absorpition of
Infrared light by CO2
Capnography: Nondiverting (mainstream)
Measure Co2 passing through an adpator placed in the breathing circuit.
Capnography: Diverting (aspiration)
Continously suction gas from the circuit into a sample cell in the monitor.
Capnography: Diverting (aspiration): HIGH ASPIRATION rates
defined as up to 250ml/min and low dead-space sampling tubing usualy increase SENSITIVITY and decrease lag time.
Capnography: Diverting (aspiration): Low ASPIRATION rates
50ml/min can underestimated ETCO2 during rapid ventilation.
Capnography : diverting (sidestream) units are prone to
Water precipitation that can cause obstruction of the sampling line and erroneous readings.
How is expiratory valve malfunction determined
Detected by the presence of CO2 in inspired gas.
Capnographs reliably indicate ______Intubation but do not reliably detect ______intubation
Esophageal intubation ; bronchial intubation
May indicated a circuit disconnection is
Sudden cessation of CO2 during expiratory phase of the capnograph
A marked rise in ETCo2 may be caused by
the increased metabolic rate associated with MH
The PaCo2-ETCO2 gradient is usually
2-5 mmHg reflects alveolar dead space (alveoli that ventilated but not perfused)
What are the 3 phases of capnography and what do they mean?
Phase I : Dead space
Phase II: Dead space and alveolar gas
Phase III: Alveolar gas plateau
Characteristic of capnograph with no plateau before inspiration
COPD , shark fin
COPD on the ETCO2 and arterial CO2 gradient
Increases the gradient
Any depression during phase III (plateau) indicates
SPONTANEOUS respiratory effort.
Failure of the inspired CO2 to return to zero may indicate?
Incompetent expiratory valve or exhausted Co2 absorbent
Persistence of exhaled gas during the inspiratory phase signals the presence of
an incompetent inspiratory valve
2 ways anesthetic gas are analyzed
Infrared absorption
Piezoelectric Analysis
Infrared absorption is based on this law
Beer-Lambert law
Do not absorbed infrared light must be measure by other means
N2 and O2
What does the BEER-LAMBERT law states:
The absorption of infrared light passing through a solvent (inspired or expired gas) is proportional to the amount of unknown gas.
Piezoelectric analysisi uses
oscillating quartz crystals one of which is covered in lipid.
In piezoelectric analysis, Volatile anesthetic dissolve in the
Lipid layer, and their concentration is determined by the change in oscillation frequency. This method cannot distinguish different anesthetic agents.
3 ways OXYGEN is analyzed?
Galvanic cell
PARAMAGNETIC ANALYSIS
Polarographic electrode
Galvanic cell for the analysis of oxygen explain?
Galvanic cell hydroxyl ions are formed at the gold cathode and react with lead anode.
Galvanic cell for the analysis of oxygen An
electrical current is produced that is proportional to the amount of oxygen being measured
Oxygen is a nonpolar gas that is paramagnetic and expands when placed in a magnetic field. By switching the field on and off, the volume change can be used to measure O2 content. which concept of O2 analysis?
PARAMAGNETIC ANALYSIS concept
A semipermeable membrane separates gold cathode and silver anode . A voltage is applied and OH- are formed from O2; resulting current is proportional to the amount of O2. which concept of O2 analysis?
Polarographic electrode concept
SPIROMETRY: Low and HIGH peak inspiratory pressure:
Indicates circuit disconnect or airway obstruction, respectively
SPIROMETRY: Minute ventilation
Obtained by measuring Vt and breathing frequency.
Altered by certain diseases and events such as obstruction and bronchial intubation?
Spirometric loops and waveforms.
EEG is a recording of
Electrical potentials generated by cells in the cerebral cortex that can be used during cerebrovascular surgery to confirm adequate cerebral oxygenation.
Waves found in resting adult with eyes closed
Alpha waves
Waves found in concentrating individuals and at times under anesthesia
Beta waves
Wave found in brain injury, deep sleep and anesthesia
Delta waves
Found in deep sleep and anesthesia
Theta waves
Frequencies of alpha and beta waves
8-13 Hz
Theta waves frequency
4-7 Hz
Delta waves frequency
0.5 - 4 Hz
Frequencies from HIGH to low
Alpha
Beta
Theta
Delta
EEG waves are characterized by their _____and are examined for ______
Amplitude; left - right symmetry
Inhalational agents cause initial ______
beta activation , then slowing, burst suppresion, and isolectricity.
Used to detect EEG isoelectricity during hypothermic arrest?
EEG.
BIS examined what components
4 EEG components
What are the 4 EEG components examined by BIS
Low frequency (deep anesthesia)
High Frequency (light anesthesia)
Suppressed EEG waves
Burst suppression.
BIS values of 65-85 indicates
Sedation
BIS values recommended for GA
40-65
Evoked potentials (EP) assess
neural function
Evoked potentials (EP) assess neural function by measuring what/
Elecrophysiologic responses to sensory or motor pathway stimulation.
Commonly monitored EPs are
Brainstem Auditory Evoked responses (BAEPs)
SomatoSensory evoked potentials (SSEPs)
Motor Evoked potentials (MEPs)
For SEPs electrical current is applied to a
Sensory or MIXED PERIPHERAL nerve by electrodes . if the intervening pathway is intact, the action potential will be transmitted to the CONTRALATERAL sensory cortex to produce an EP that is detected by scalp electrodes.
EPs are plotted as
Voltage vs time
EPs waveforms are analyzed by their
poststimulus latency
peak amplitude
Indications for EP monitoring
procedures associated with possible neurologic injury such as spinal fusion, spinal cord tumor resection, brachial plexus, epilepsy surgery and cerebral tumor resection.
Used to monitor cerebral cortex ischemia
EPs
Motor EVOKED potentials contraindicated in
after seizures
skull defect
implantable devices.
Concern with MEPs are
repetitive stimulation of the cortex
inducement of seizures
Nitrous and opioid and EP
Caused minimal changes with EPs
Volatile agents and EPs
BEST AVOIDED or used at a low dose.
SEP identify _____________ damage but not necessarily identify __________
Dorsal spinal cord sensory pathway
Motor pathway damage
From most to least sensitive
VEP, SSEP, BAEP (very, somewhat, barely)
MEPs are sensitive to
VA High dose benzodiazepines moderate hypothermia (less than 32C)
MEP monitor the
Ventral spinal cord and are more sentitive to spinal cord ischemia than SSEPs.
Cerebral oximetry uses
NEAR-INFRARED SPECTROSCOPY (NIRS)
Cerebral oximetry NIRS work
Near infrared light is emitted by a scalp probe, which receptors positioned to detect the reflected light from intracranial structures.
For cerebral oximetry saturation ________ on NIRS measures reflect decreased cerebral O2
less than 40
For cerebral oximetry changes of _________may refelct decreased Cerebral O2
greater than 25%
Jugular venous bulb saturation explain? Where should brain oxygen tension be?
Probe placed in IJ and directed toward the brain to determine the brain oxygen tension, which should be kept at 20 mmHg or greater.
Interventions to improve brain tissue oxygen content include
Increasing fiO2, hemoglobin,
adjusting CO
Decreasing Oxygen demand
Complications with temperature probes are caused by
Probe placement trauma
Hypothermia definition
Less than 36C
Risk factors for unintentional perioperative hypothermia
Extremes og f age
abdominal surgery
procedures of long duration
cold ambient OR temperature
When does HYPOTHERMIA helpful?
Protective during time of cerebral or cardiac ischemia
Postop HYPOTHERMIA IMPORTANT IMPLICATIONS
Increases O2 consumption as much as fivefold and is correlated with an increased in MI and angina
Anesthesia induced vasodilation causes what with temperature
Redistribution of heart from WARM CENTRAL COMPARTMENTS to COOLER peripheral tissues.
Anesthesia and hypothalamic function
GA inhibits hypothalamic function, reducing the body’s compensatory response to hypothermia.
Solution to prevent GA hypothermia
Prewarming with forced-air warming blankets
Administering warm IV fluids
raising OR temperature room.
Where should foley catheter be
below the bladder to min urine reflux and the risk of infection.
Only reliable way to monitor UO
Catheterization
Indications for foley catheter?
CHF Renal failure hepatic disease shock Procedures associated with large fluid shift or diuretic admnistration
Benefit of a foley catheter as far at temp
ability to include a thermistor in the tip to measure bladder temperature.
Inadequate UO is
Less than 0.5ml/kg/h
Aid in differential dx of oliguria: 3 things
Urine electrolyte composition
osmolality
Specific gravity
2 indications of PNS
monitor paralysis with admin of NMB
locate nerve to be blocked by regional anesthesia.
Contraindications of PNS
Atrophied muscles caused by Hemiplegia or nerve damage may appear refractory to NMBA because of receptor proliferation, which can lead to potential overdosing of NMBA.
PNS delivers current _______ mA
60-80 mA
PNS stimulates the ulnar nerve at which muscle?
Adductor policis
PNS stimulates the facial nerve at which muscle?
Orbicularis oculi
Avoid what with placing electrodes?
Avoid direct muscle stimulation such as placing electrodes directly over the muscle
Last muscle to recover
Adductor policis
Muscles that recover before the adductor policis
Diaphragm, rectus abdominis, laryngeal adductors, and orbicularis oculi muscles.
Indicators of recovery include
Sustained head lift (>5sec)
Generation of INSPIRATORY PRESSURE of at least -25 cm H2O
Forceful hand grasp.
Train of four are
4 successive 200 microseconds stimuli in 2 s (2 Hz)
Twitches fade progressievly as
relexation increases
Sensitive indicator of NMBA relaxation:
Ratio of first (T1) and fourth (T4) twitches (T1/T4)
Loss of fourth twitch represents
75% block
Loss of third twitch represents
80% block
Loss of second twitch represents
90% block
Clinical relaxation from NMB requires
75-95% NMB
Tetany applied at
50-100Hz
Sensitive test of NM function: aside from TOF
Tetany at 50-100Hz
With tetany , what indicates adequate, but NOT NECESSARILY complete reversal from NMB
Sustained contraction for 5 seconds
