anesthetic monitoring and recovery

  1. best anesthetic machine
    five senses
  2. reasons for monitoring
    • determine physiologic status of P
    • determine EXTENT of compromise to body systems
    • anticipate complications/avert disasters before they occur
    • recognize problems early
    • recognize changes that compromise P's well being
    • determine efficacy of therapy in correcting problems
  3. monitoring of three major body systems
    • Respiratory system: adequate oxygenation and ventilation (O2 and CO2)
    • Cardiovascular system: adequate circulation to maintain perfusion
    • CNS: muscle tone and reflexes to indicate degree of CNS depression
  4. function of cardiovascular system
  5. what to look for in respiratory monitoring
    • smooth and regular - watch chest wall and rebreathing bag
    • normal respiratory sounds almost inaudible on auscultation
    • watch for tachypnea
  6. causes of tachypnea
    • pain or nocioception
    • hypoxemia
    • hypercapnea (or hypercarbia)
    • hyperthermia
    • anesthesia too light
  7. normal air % of O2
    • 21% O2
    • in anesthesia, if Iso is 2%, O2 is 98%
  8. SaO2 or SPO2
    • saturation of O2
    • % Hb saturated with O2 (in arterial blood)
    • detected by pulse oximeter
  9. pulse oximeter
    • detects hypoxemia by measuring SPO2/SaO2
    • Normal is 95-100%
    • attached to tongue or hairless, unpigmented area like lip, toe web, pinna, prepuce or vulva
  10. Partial pressure of O2 in room air
  11. partial pressure
    pressure a gas exerts in a mixture of gasses
  12. <95% SpO2
    significant hypoxemia
  13. <90% SpO2
    • serious hypoxemia.  Cyanosis first clinically apparent (unless anemic, not enough hemoglobin to show signs)
    • equivalent to PaO2 of 60mmHg
    • try repositioning probe or patient, check pulse ox
  14. anemia and the pulse-ox
    severly anemic patients may not appear cyanotic even with low O2--not enough hemoglobin to show signs
  15. tx for hypoxemia
    • if on room air, supplement with 100% O2
    • check O2 supply, anesthesia machine, ET tube and breathing circuit
    • assist or control ventilation (check for apnea)
    • check circulation
  16. How pulse ox works
    • probe emits infrared light
    • light detector measures infrared and red light passing through tissues with PULSATILE flow (arteries) during systole
    • uses dif absorption of deoxy-Hb and Oxy-Hb to calculate percentage of oxy-Hb to total Hb
  17. causes of inaccurate readings of pulse oximetry
    • anything that interferes with accurate measurement of infrared or red light passing through pulsatile tissue
    • environmental light (shield probe from direct light)
    • fur
    • pigmentation (including icterus)
    • motion (including shivering)
    • pressure of clip prevents blood flow to capillaries (reposition frequently)
    • vasoconstriction
    • anemia/carboxyHb/MetHb
    • SpO2<80%
    • HR too low
    • hypotension or arrhythmia
  18. Pulse ox and ventilation
    pulse oximeters do not measure adequacy of ventilation
  19. respiratory rate and ventilation under anesthesia
    • under anesthesia and breathing spontaneously = hypoventilating (still can be well oxygenated, but CO2 too high)
    • most anesthetic agents/analgesic agents decrease respiratory rate, decrease tidal volume
  20. atelectasis and anesthesia
    • anesthesia relaxes skeletal muscles, decreses respiratory rate and tidal volume
    • if alveoli don't expand, leads to atelectasis, causes alveolar dead space (VD)
    • no deep breaths = not expanded fully = alveoli want to collapse
  21. most accurate measure of adequacy of ventilation
    • Levels of CO2 in blood plasma indicated by PaCO2 (arterial blood gas)
    • indicated by hypercapnea (leads to respiratory acidosis, can be fatal)
  22. capnography
    • measures CO2 in inspired and expired air, assesses adequacy of ventilation
    • measures end-tidal CO2 (ETCO2) - amount of CO2 in expired air at end of expiration
    • Can be mainstream (sensor on ET tube, heavy) or sidestream (sensor on side)
    • check ET tube placement
  23. Where ETCO2 is on a capnograph
    Image Upload 1
  24. ETCO2 vs PaCO2
    Partial pressure of O2 in arterial blood gas is always 2-5 mmHg higher than ETCO2 (amt of CO2 in expired air at end of expiration)
  25. normal ETCO2
    • 35-45 mmHg
    • neurosurgery likes 25-27 mmHg
  26. ETCO2 > 45-50 mmHg
    • Hypercapnea and hypoventilation
    • respiratory acidosis
  27. ETCO2 < 30-35
    • Hypocapnea and hyperventilation
    • respiratory alkalosis
  28. Image Upload 2
    • rebreathing expired air
    • CO2 absorber exhausted
  29. Image Upload 3
    nonrebreathing system
  30. esophageal intubation
    0 or very low ETCO2
  31. Image Upload 4
    oscillations due to a strong heartbeat
  32. Image Upload 5
    • hyperventilation
    • hypocapneic, alkylosis
  33. abrupt drop in ETCO2
    • Signals failure to ventilate
    • ET tube/breathing circuit disconnected, ET tube or breathing circuit kinked or blocked, closed pop-off valve, mechanical failure (check capnograph by breathing into it)
  34. Image Upload 6
    • cardiac arrest and circulatory collapse
    • decreased cardiac output, decreased pulmonary perfusion = decreased ventilation
  35. Best way to detect early airway mishaps like apnea
    capnography.  Superior to pulse oximetry and blood gas
  36. only noninvasive monitor of effective CPR
  37. Image Upload 7
    • effective CPR
    • indicated by ETCO2 of at least 14 mmHg
    • first part is cardiac arrest, 2nd part is CPR
  38. Causes of high ETCO2 and hypercapnea
    • hypoventilation
    • rebreathing CO2 - exhausted CO2 absorber, too low O2 flow rate
    • too narrow or too long ET tube
    • one-way valve stuck open
    • insufflation of CO2 during laparoscopy
  39. correction of hypoventilation
    • assist or control ventilation - once you take over you likely have to continue
    • reduce vaporizer setting until anesthetic depth as low as possible for procedure
    • address primary cause
  40. assisted ventilation
    • animal breathes spontaneously but is manually ventilated 1-2 times per minute
    • Helps prevent atelectasis, hypercapnea and respiratory acidosis
    • indicated when ventilatory adequacy is in doubt (>45-50 mmHg)
  41. controlled ventilation
    • breathing is completely controlled manually or by mechanical ventilator
    • indicated in animals that cannot be expected to breathe or are not breathing spontaneously, or when hypercapnia would be particularly detrimental
  42. manual ventilation technique
    • close pop-off, squeeze rebreathing bag, open pop-off.
    • pressure should not exceed 20cmH2O in adults, chest rises like normal/awake
    • I:E ratio of 1:2 seconds
  43. Causes of low ETCO2
    • hyperventilation (too rapid RR, overzealous artificial ventilation)
    • excess dead space in ET tube or breathing circuit
    • ET tube in esophagus or brunchus
    • hypothermia
    • pulmonary embolism
    • cardiopulmonary arrest
  44. anesthetic causes of tachycardia
    • pain
    • light anesthesia (too deep = sevo)
    • hypoxemia
    • hypercapnea
    • decreased BP (fluid therapy, hypovolemia)
    • hyperthermia
    • drugs (isoproterenol, atropine, glyco, ketamine)
  45. anesthetic causes of bradycardia
    • too deep anesthesia
    • increased vagal tone - caused by drugs (alpha2 agonists, opioids, dexdormitor) or surgical manipulations (head, neck, eye, long bones, some organs)
    • heart disease
    • hypothermia
    • acidosis
    • impending arrest
  46. most common perianesthetic complication
    • hypotension
    • most drugs decrease BP
  47. indirect BP monitor
    • cuff placed around limb and inflated until underlying artery compressed.  pressure in cuff > pressure in artery, blood flow stops, deflate cuff slowly, blood flow resumes when pressure in cuff = pressure in artery.  
    • Systolic BP measured as pressure when blood flow first resumes
  48. 2 types of blood pressure
    • oscillometric and doppler
    • Oscillometric = machine and cuff
    • doppler = crystal and bulb
  49. How to choose a BP cuff
    • 40% of limb circumference
    • too wide or too tight = falsely low readings
    • too narrow or too loose = falsely high readings
  50. hypotension under anesthesia
    • due to excessive anesthetic depth
    • caution when using fluid treatment (can cause vascular overload)
    • if peripheral vasodilation causes hypovolemia, decrease anesthetic depth, provide IV bolus of crystalloids, repeat, if not fixed, IV colloid (slow, titrate)
    • vasopressors, etc.
  51. central venous pressure
    • The amount of pressure reflected from the intrathoracic anterior vena cava to a column of water in a plastic monometer or a pressure transducer
    • represents heart's ability to pump venous return
    • measures pressure in vena cava, should be 0-10 cmH2O.  Build up = fluid overload, CHF
    • must take reading at same level as heart
    • jugular vein, cranial vena cava, tip of catheter just outside right atrium
    • take 3-5 readings, average
  52. mucous membrane color
    • determined by Hb concentration, tissue PO2 and blood flow in peripheral capillaries
    • normally pink
    • pale: due to low Hb (anemia), poor perfusion, vasoconstriction
    • blue: hypoxemia
  53. Capillary refill time (CRT)
    • reflects blood flow in capillary beds of mucous membranes
    • normal 1-2 sec
    • < 1 sec indicates vasodilation (fever, pain, hyperthermia, sepsis)
    • > 2 sec indicates vasoconstriction (hypotension)
    • NOT INFALLABLE (may be normal even after cardiac arrest)
  54. causes of peripheral vasoconstriction
    • sympathetic tone
    • drugs
  55. prolonged CRT
    • increased sympathetic tone
    • pain, fear, excitement, hypotension, hypovolemia, hypothermia (baroreceptor reflex)
  56. response to signs of pain under anesthesia
    treat the pain, don't dial up the anesthesia
  57. why body temperature can be a problem after anesthesia
    • anesthesia causes CNS depression, hypothalamus depressed, hypothalamus causes temperature regulation
    • hypothermia: open body cavity loses heat
    • new air in respiration can be cold
    • fluids can be cold
    • prep with alcohol and scrub = wet = cold
    • drugs decrease metabolic rate, decrease muscle tone (can't shiver)
    • vasodilation in cutaneous blood vessels
    • hyperthermia: excitement/fear/pain
    • drugs (ketamine, propofol, opioids), esp in cats
  58. measures to prevent hypothermia
    • external heating sources considered most effective: bair hugger, circulating warm water blankets, AVOID HEATING PADS OR LAMPS (except rodents)
    • warmed IV fluids
    • do not put P on cold surfaces
    • don't use alcohol on pediatric animals
    • keep OR temp at 75F
    • keep patients dry or dry with blow dryer
  59. neuromuscular indicators of anesthesia
    • anesthetic agents decrease muscle tone
    • assess resistance to opening mouth, flexing and extending leg, opening eyelids
    • ketamine increases muscle tone.
  60. Stage I of anesthesia
    • stage of voluntary excitement or voluntary movement
    • from administration of induction agent to loss of consciousness
    • excitement/fear lead to catecholamine release (arrhythmias. Tachycardia needs more O2)
    • Reflexes present
    • normal muscle tone, but ataxia, loss of ability to stand, assumption of lateral recumbancy toward end
  61. stage II of anesthesia
    • stage of involuntary excitement, involuntary movement or delerium
    • begins with loss of consciouness, ends with onset of normal breathing pattern
    • state of unopposed CNS excitation - may vocalize, exhibit rapid limb movement, external stimulation may cause violent reflex movement due to loss of motor control.  Increased HR, risk of arrhythmias
    • jaw tone and reflexes still present
  62. stage III of anesthesia
    • surgical anesthesia, characterized by unconsciousness with progressive depression of reflexes.  
    • Normal intubation stage
    • 4 planes.
  63. Stage III of anesthesia, Plane 1
    • Respiration becomes regular, normal HR, strong pulses, involuntary movement stops
    • movement in response to painful stimulus
    • eye position rolls ventromedial to ventral during surgical plane of anesthesia in most species
  64. Stage III of anesthesia, plane 2
    • light plane of surgical anesthesia adequate for most surgical procedures
    • respiratory and HR increase in response to surgical stimulation or nocioception.  P remains unconscious and immobile in response to skin incision
    • adequate muscle relaxation for most sx, jaw tone moderately relaxed
    • palpebral, patellar, pinna and corneal reflexes present.  Usually have lost pedal reflex (toe pinch)
  65. corneal reflex
    drop saline into eye, eyeball will withdraw a tiny bit
  66. Stage III of anesthesia, plane 3
    • deep surgical anesthesia
    • respiration depressed
    • decreased arterial BP, increased CRT, +/- bradycardia
    • profound muscle relaxation
    • corneal reflex weak, pupillary light reflex weak
    • centered dilated pupil
    • too deep for most procedures
    • Not usually used because we have pain meds instead
  67. Stage III of anesthesia, plane 4
    • respiratory and cardia arrest imminent
    • respiration diaphragmatic, slow and irregular with "rocking boat" pattern (DRAMATIC mvmt of diaphragm)
    • hypotension, bradycardia, pale mucus membranes, prolonged CRT, loss of peripheral pulses
    • reflexes abolished
    • turn off vaporizer, ventilate with 100% oxygen, provide cardiovascular support
    • seen on capnograph.  BAD, but can usually get back
  68. stage IV of anesthesia
    • stage of medullary paralysis
    • respirations stop, pupils dilated and unresponsive, anal and bladder sphincters erlax, muscles flaccid
    • TURN OFF vaporizer, ventilate with 100% oxygen and administer CPR.  PRAY
  69. anesthetic recovery
    • wake up in reverse order
    • closely monitor
    • sternal every 10-15 minutes to prevent BLOOD POOLING (dorsal can cause bloat)
    • maintain venous access (catheter)
    • monitor response to fluid therapy
    • 5 minutes of O2 to flush animal/system
    • vital signs q5min
    • body temp (warm to 99F)
    • monitor for signs of pain
    • post-op diarrhea (lack of GI perfusion)
  70. signs of inadquate fluid therapy
    increased HR, poor pulse quality, hypotension, decreased urine output
  71. signs of over-administration of fluid therapy
    • increased respiratory rate and effort
    • peripheral or pulmonary edema
    • weight gain
    • pulmonary crackles (late sign)
  72. extubation
    • most animals ready upon return of swallowing reflex
    • extubate when see: tongue movement, voluntary limb movement, attempts to remove tube
    • brachycephalics: delay extubation until able to lift head unassisted, sternal.  Monitor continuously until fully conscious
    • Deflate cuff and untie tube prior to extubation.  If vomits, elevate body above head, keep ET tube partially inflated
Card Set
anesthetic monitoring and recovery
VETC 247 surgical nursing, anesthetic monitoring and recovery