Anesthesia2- Monitoring

CVS, respiratory system, CNS

• ensure that blood flow to tissue is adequate
• ensure adequate oxygen concentration in the patients arterial blood
• ensure that the patients ventilation is adequately maintained
• record monitored variables at regular intervals (minimum every 10 min)
• maintain legal record
• ensure a responsible individual is aware of patient's status at all times during anesthesia and recovery

somatic muscle tone, respiratory patterns, and ocular signs.

ether anesthesia

• Stage I: analgesia
• Stage II: delirium (voluntary followed by involuntary excitement)
• Stage III: surgical (divided into planes 1 through 4)
• Stage IV: respiratory paralysis

• movement in response to surgery
• eye reflexes and position of eye within orbit
• pedal reflex
• anal tone
• EEG- bispectral index

• Too light- blink (LA strong blink)
• Just right- no blink (LA slow blink)
• Too deep- no blink

• awake- central position
• light plane- eye rotated ventromedial or dorsolateral
• moderal surgical anesthetic plane- eye slightly ventral but centrally positioned
• deep anesthetic plane- eye central with dilated pupil

• fully open mouth and determine resistance (loosest=1, tightest=10)
• too light 7-10
• too deep 1-4
• just right 5-7

• fast HR, high BP- too light
• fast HR, low BP- getting deeper
• slow rate, low BP- deep

rate slows with increasing depth, BUT fast and shallow breaths indicate the patient is too deep

• DO2= CO x CaO2
• CO= HR x SV [HR depends on SNS and PNS, SV depends on inotropy, preload, afterload]
• CaO2= (Hb x SpO2 x 1.36) + (PaO2 x 0.003) [depends on amount of Hb, O2 satursation of Hb, minimal effect of O2 dissolved in plasma]

PCV/3

alpha-1 agonists cause intense peripheral vasoconstriction--> any patient pre-meded with an alpha-2 will have pale MMs and prolonged CRT but this does not reflect CV status

• MM color
• CRT
• HR
• BP

• Dogs: sinus rhythm, respiratory sinus arrhythmia
• Cats: sinus rhythm
• Horses: sinus rhythm, 1° or 2° AV block (esp in athletic horses!)

• algorithm in machine looks for biggest deflection in base line and assumes this is the R wave--> counts these as HR
• can be wrong when T waves are really high (double counts--> reports falsely increased HR); can also be wrong in patients with an arrhythmia

• reports systolic pressure only
• requires manual manipulation for blood pressure monitoring
• better to track BP trends rather than absolute values

• accuracy and reliability suspect in smaller patients, LAs, motions, and lower pressures
• best used to track trends

40% of the circumference of the limb

display HR, systolic, diastolic and mean BPs

• mean BP < 60mmHg
• or systolic BP <80-90mmHg

• excessive anesthetic depth
• hypovolemia
• circulatory shock
• sepsis
• acepromazine
• propofol
• inhalants
• histamine release

• inadequate anesthetic depth
• pain
• hypercarbia
• fever
• disease
• catecholamines
• ketamine
• alpha-2 agonists
• hypoxemia (early)

• rhythm
• HR

• inadequate anesthetic depth
• hypotension
• ketamine
• thiopental
• anticholinergics
• sympathomimetics
• hyperthermia
• hypercarbia
• hypoxemia
• anemia
• hyperthyroidism
• anaphylaxis

• excessive inahaltion anesthetic depth
• opioids
• alpha-2 agonists
• pre-existing cardiac disease
• vagal reflexes
• hyperK+
• hypertension
• hypothermia
• terminal hypoxemia
• Cushing's reflex (high intracranial pressure)

• respiratory rate and depth- observe chest wall excursions, observe rebreathing bag, airway thermistor probe
• respirometer
• capnometry
• pule oximetry

• detects the difference in temperature between inspiratory breath and expiratory breath to determine respirations
• over time patient cools down during sx, so this become less reliable as the surgery gets longer

• chest wall movement
• breath sounds through esophageal stethoscope
• breathing bag movement
• airway thermister probe

• capnometry/ capnography
• blood gas analysis
• respirometer

• continuous, non-invasivemeasurement of carbon dioxide concentration in inspired and expired air through infra-red absorption technology
• we care because end-expired CO2 correlates to arterial CO2

• during normal breathing, air is drawn into the chest by negative intrathoracic pressure (which develops due to contraction of diaphragm and intercostals)
• during mechanical ventilation, air is forced into the chest by positive pressure from an external source

• hypoventilation
• dead space rebreathing
• hyperthermia

• airway obstruction
• anesthetic depression
• intracranial disease
• neuromuscular disorders
• thoracic or abdominal restrictive disease
• neuromuscular blockade
• pleural space fluid or air
• severe pulmonary disease

incompetent one-way valves, exhausted soda lime

• hyperventilation (excessive mechanical/ hand ventilation)
• decreased cardiac output/ perfusion

cardiac output and oxygen content of blood

BP, HR, hemoglobin (PCV), SpO2

20%

continuous real time estimates of arterial hemoglobin saturation with oxygen, which can warn of hypoxemia from loss of airway, loss of oxygen supply, inadequate lung function, or circulatory failure.

measures transmission of light at two wavelengths through a pulsatile vascular bed

• low inspired oxygen concentration
• hypoventilation (including airway obstruction)
• pulmonary or pleural space (primary lung disease, pulmonary edema, atelectasis)
• circulatory failure
• abnormal hemoglobin (carboxyhemoglocin, methemoglobin)

• vasoconstriction (hypothermia, drug induced)
• motion
• shivering
• ambient light
• pigmentation
• poor sensor positioning
• carboxyhemoglobin
• methemoglobin

• anemia
• hypoventilation

• pH= 7.4
• SaO2 > 90%
• PaCO2= 35-45 mmHg

• V_T x f
• V_T= tidal volume (normal 10-15mL/kg)
• f= resp rate (normal 8-12/min)

• oxygenation: apnea, PaO2 < 60mmHg on supplemental O2, shunt fraction > 20%, alveolar to arterial gradient more than 350mmHg on 100% FiO2
• ventilation: PaCO2 more than 60mmHg, V_D/V_T  > 0.6
• neuromuscular blocking drugs
• intrathoracic surgery
• anesthetic delivery device in patients that are difficult to keep asleep

• during inspiration, positive pressure i transferred to the intrapleural space, decreasing venous return
• CO and arterial BP are decreased

• increases intrathoracic pressure--> compression of great vessels
• preload= venous return decreases
• afterload= aortic pressure increases
• mechanical ventilation increased intrathoracic pressure--> decreased venous return--> decreased preload--> decreased inotropy--> decreased CO--> decreased aortic BP

• CO2 + H2O <--> H2CO3 <--> H+ + HCO3-
• hyperventilation--> dec CO2--> resp alkalosis--> decreased CBF
• hypoventilation--> inc CO2--> resp acidosis--> CNS depression
• ideal PaCO2= 40mmHg

a predetermined volume, at a predetermined pressure, and a predetermined flow rate for a predetermined period of time [act as an extra pair of hands]

• assist: controls volume or pressure
• controlled: control rate and volume
• assist- controlled: min ventilation rate is operator controlled, ventilatory rate may be triggered by the patient if the spontaneous rate is faster and enough neg pressure is generated than the controlled ventilator rate

patient is tachypneic, panting, or hyperpneic

• dependent lung collapses over time
• increase functional residual capacity open small airways
• improve pulmonary compliance (decrease work of breathing)
• improve ventilation/ perfusion ratio
• [lungs exhibit hysteresis (different pressure at which they collapse and at which they open); by adding PEEP, we can keep the alveoli open a little bit so it never quite collapses, making it easier to reinflate the alveolus--> improved ventilation and oxgenation]

• prophylactic PEEP: used to increase FRC above closing capacity, prevent atelectasis, decrease shunting
• conventional PEEP: indicated if PaO2 <60mmHg with FiO2 >0.5
• high PEEP: used in extreme hypoxemia and no response to conventional PEEP

decreased preload, decreased CO

• 20cm H20 inspiratory force generated by patient
• PaO2 > 80mmHg with FiO2< 0.4
• normal A-a gradient
• PaCO2 <50mmHg

P_aO₂ = 5 x F_iO₂

35-45mmHg