anesthetic monitoring and recovery

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anesthetic monitoring and recovery
2014-04-19 23:09:48
vet tech 247
vet tech 247
VETC 247 surgical nursing, anesthetic monitoring and recovery
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  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
  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
    • rebreathing expired air
    • CO2 absorber exhausted
  28. nonrebreathing system
  29. esophageal intubation
    0 or very low ETCO2
  30. oscillations due to a strong heartbeat
    • hyperventilation
    • hypocapneic, alkylosis
  31. 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)
    • cardiac arrest and circulatory collapse
    • decreased cardiac output, decreased pulmonary perfusion = decreased ventilation
  32. Best way to detect early airway mishaps like apnea
    capnography.  Superior to pulse oximetry and blood gas
  33. only noninvasive monitor of effective CPR
    • effective CPR
    • indicated by ETCO2 of at least 14 mmHg
    • first part is cardiac arrest, 2nd part is CPR
  34. 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
  35. 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
  36. 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)
  37. 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
  38. 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
  39. 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
  40. anesthetic causes of tachycardia
    • pain
    • light anesthesia (too deep = sevo)
    • hypoxemia
    • hypercapnea
    • decreased BP (fluid therapy, hypovolemia)
    • hyperthermia
    • drugs (isoproterenol, atropine, glyco, ketamine)
  41. 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
  42. most common perianesthetic complication
    • hypotension
    • most drugs decrease BP
  43. 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
  44. 2 types of blood pressure
    • oscillometric and doppler
    • Oscillometric = machine and cuff
    • doppler = crystal and bulb
  45. 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
  46. 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.
  47. 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
  48. 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
  49. 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)
  50. causes of peripheral vasoconstriction
    • sympathetic tone
    • drugs
  51. prolonged CRT
    • increased sympathetic tone
    • pain, fear, excitement, hypotension, hypovolemia, hypothermia (baroreceptor reflex)
  52. response to signs of pain under anesthesia
    treat the pain, don't dial up the anesthesia
  53. 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
  54. 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
  55. neuromuscular indicators of anesthesia
    • anesthetic agents decrease muscle tone
    • assess resistance to opening mouth, flexing and extending leg, opening eyelids
    • ketamine increases muscle tone.
  56. 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
  57. 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
  58. stage III of anesthesia
    • surgical anesthesia, characterized by unconsciousness with progressive depression of reflexes.  
    • Normal intubation stage
    • 4 planes.
  59. 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
  60. 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)
  61. corneal reflex
    drop saline into eye, eyeball will withdraw a tiny bit
  62. 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
  63. 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
  64. 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
  65. 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)
  66. signs of inadquate fluid therapy
    increased HR, poor pulse quality, hypotension, decreased urine output
  67. signs of over-administration of fluid therapy
    • increased respiratory rate and effort
    • peripheral or pulmonary edema
    • weight gain
    • pulmonary crackles (late sign)
  68. 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