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1

What does hydrogen ion concentration give us?

pH

2

What do we know if the H+ ion concentration exceeds hydroxyl ions?

Solution is acidic

3

What do we know if the H+ ion concentration is less than the hydroxyl ions?

Solution is aklalotic

4

Which substances dissociate or dissolve into their component parts in water?

Those with polar bonds

5

What determines whether a substance is a strong acid or strong base?

The degree of dissociation in water

6

What is the Law of Mass Action?

Rate of chemical reaction is proportional to product of masses of the reacting substances

7

Which three rules must be followed for acid and base balance?

1. Electrical neutrality
2. Dissociation equilibrium which follow the law of mass action
3. Mass conservation

8

What are pH alterations due to that lead to metabolic acidosis or alkalosis?

Abnormal bicarbonate reabsorption and hydrogen ion elimination by the kidneys

9

What are pH alterations due to that lead to respiratory acidosis or alkalosis?

Altered respiratory drive and CO2 levels

10

Do respiratory and metabolic disorders occur independently?

Rarely, you can have mixed or complex acid-base disorders

11

What is the degree of water dissociation and hydrogen ion concentration affected by in the modern approach to acid-base balance?

Strong ions, weak acids and carbon dioxide

12

Which approach to acid-base disorders is explained by the effect of PCO2, SID, Atot?

Stewart Approach

13

How do you calculate the SID?

(Na+ + K+ + Ca2+ + Mg2+) - (Cl- + lactate-)

(strong cations - strong anions)

14

Changes in SID will cause changes in what two concentrations?

Hydrogen ion and hydroxyl ion concentrations

15

Which ions dissociate completely leading to a direct affect on acid-base balance?

Na+ and Cl-

16

What does increased SID indicate?

alkalosis and presence of unmeasured cations

17

What does decreased SID indicate?

acidosis and presence of unmeasured anions

18

Describe SID in ECF

It is positive and 40-44 mEq/L

19

What is the degree of dissociation determined by for weak acids?

Temperature and pH

20

Give an example of two weak acids

albumin and phosphate

21

What does an increase in weak acid concentration indicate?

acidosis

22

What does a decrease in weak acid concentration indicate?

alkalosis

23

Describe SID and total weak acids in relation to the presence of acid base disorders

They are independent variables and are inversely related in the presence of acid base disorders

24

What does the Boston approach use for ABG analysis?

acid-base maps and the relationship between CO2 and bicarb

25

5 questions we ask when analyzing ABGs?

1. What is the suspected or actual cause?
2. Does my physical assessment support these findings?
3. How do I treat the disorder?
4. Do I treat the disorder?
5. Did I cause it preoperatively?

26

What is the first thing we should ask when looking at any acid-base disorder?

Is the patient hypoxic

27

What lab value change do we see in respiratory alkalosis?

decreased PCO2 and increased pH

28

What do we see in the Stewart approach with respiratory alkalosis?

decreased PaCO2

29

Primary cause of respiratory alkalosis?

Increased minute ventilation/mechanical hyperventilation

30

Symptoms of respiratory alkalosis? (5)

1. Vasoconstriction
2. Lightheadedness
3. Visual disturbances
4. Dizziness
5. Possible hypocalcemia

31

Other causes of respiratory alkalosis? (6)

1. Abnormal respiratory drive from stimulants or toxins such as anxiety or pain
2. CNS abnormalities
3. Pulmonary insult/injury such as PE
4. Liver failure
5. Sepsis
6. Pregnancy

32

What do we expect to see in the HCO3- with acute compensation of respiratory alkalosis?

HCO3- will decrease 2 mEq/L for every 10 mmHg decrease in PCO2 down to a 20 mmHg decrease

33

What do we expect to see in the HCO3- with chronic compensation of respiratory alkalosis?

HCO3 will decrease 5 mEq/L for every 10mmHg decrease in PCO2 down to a 20 mmHg decrease

34

Treatment for respiratory alkalosis?

decrease minute ventilation/ventilator change, treat cause

35

What lab value change do we see in respiratory acidosis?

Increased PaCO2 and decreased pH

36

Primary cause of respiratory acidosis?

Failure of the lungs to eliminate CO2/hypoventilation

37

Symptoms of respiratory acidosis? (3)

1. Vasodilation
2. Narcosis
3. Cyanosis

38

Other causes of respiratory acidosis? (5)

1. Drug associated respiratory depression
2. Neurologic injury
3. Lung injury/disease
4. Neuromuscular and musculoskeletal disease
5. Inadequate NMBD reversal

39

What change in HCO3 would we expect to see in acute compensation of respiratory acidosis?

HCO3 will increase 1 mEq/L for every 10 mmHg increase in PCO2 > 40mmHg

40

What change in HCO3 would we expect to see in chronic compensation of respiratory acidosis?

HCO3 will increase by 4 mEq/L for every 10 mmHg increase in PCO2 > 40 mmHg

41

Treatment for respiratory acidosis?

increase minute ventilation/ventilator changes, treat cause

42

Which acid-base disorder do you anticipate in a patient who has poor mechanical ventilation, narcosis and/or incomplete reversal of neuromuscular blockade?

respiratory acidosis

43

What lab value changes would we expect to see in metabolic alkalosis?

increase in bicarb and increased pH

44

What would the Stewart approach show in metabolic alkalosis?

Increased SID, increased concentration of cations vs anions

45

What does metabolic alkalosis result from?

net loss of hydrogen ions and or addition of bicarb

46

What is the most common cause of metabolic alkalosis?

GI acid loss from vomiting or NG suctions causing chloride loss

47

Symptoms of metabolic alkalosis? (4)

1. Widespread vasoconstriction
2. lightheadedness
3. Tetany
4. Paresthesia

48

Other causes of metabolic alkalosis? (4)

1. Diuretics
2. Third spacing
3. Bleeding
4. Hypokalemia

49

Expected PCO2 compensation in metabolic alkalosis?

0.7 x HCO3 + 20

50

Treatment for metabolic alkalosis?

Hypoventilation, fluid replacement, treat cause

51

What lab value changes would we expect to see in metabolic acidosis?

Decreased bicarb and decreased pH

52

Symptoms of metabolic acidosis? (5)

1. Vasodilation
2. Hypotension
3. Diminished muscular performance esp heart
4. Arrhythmias
5. Can lead to shock

53

How does the oxyhemoglobin dissociation curve shift in metabolic acidosis and what does it cause?

To the right causing increase oxygen delivery to tissues

54

Causes of metabolic acidosis? (9)

1. Renal injury/failure
2. DKA
3. Sepsis
4. Drugs/toxins
5. Lactic acidosis
6. GI losses with a normal AG
7. Diarrhea
8. Carbonic anhydrase inhibitor use
9. Renal tubular acidosis

55

What is the expected PCO2 in acute compensation of metabolic acidosis?

Winter's Formula is (1.5 X HCO3) + 8 +/- 2

56

What does the anion gap represent?

The total serum concentration of unmeasured anions and is the difference between measured cations minute measured anions, this is used to investigate metabolic acidosis

57

Conventional AG calculation?

(Na+ + K+) - (HCO3- + Cl-) = 14-18 mEq/L

58

Modern AG calculation?

(Na+ + K+) - (HCO3- + Cl- + lactate) = 14-18 mEq/L

59

What does an abnormal or increased AG indicate?

Metabolic acidosis is caused by unmeasured anions

60

What does a normal AG indicate?

Metabolic acidosis is caused by lactate build up or hyperchloremia such as excess normal saline use preoperatively

61

What issue do critically ill patients usually have in the presence of metabolic acidosis and a normal AG?

Hypoalbuminemia

62

Which have a far greater impact on the anion gap and why?

UMA because they are found in higher concentrations

63

What is the delta anion gap or delta ratio equation?

(Measured AG - Normal AG) / (Normal HCO3 - Measured HCO3)

64

What does the delta ratio dictate?

If the AG is normal, HCO3 decreases and the ratio will be less than 0.4 or low, supporting hyperchloremic metabolic acidosis; if the ratio is between 1 and 2 the acidosis is likely from UMAS and anticipate an abnormal AG

65

When might the Boston approach to ABG analysis be deficient?

Metabolic disorders

66

Which two approaches to ABG analysis are often combined to incorporate the sum of the difference in charge of the common ECF ions?

AG and Boston

67

What is a normal base excess?

-2 to +2

68

What does full compensation of acid-base imbalance yield?

normal pH

69

Expected HCO3 in acute respiratory acidosis?

24 + [(PaCO2 - 40)/10]

70

Expected HCO3 in chronic respiratory acidosis?

24 + 4[(PaCO2 - 40)/10]

71

Expected HCO3 in acute respiratory alkalosis?

24 - 2[(40 - PaCO2)/10]

72

Expected HCO3 in chronic respiratory alkalosis?

24 - 5[(40 - PaCO2)/10] range +/- 2

73

What is lactic acidosis a product of?

Production of lactate > the liver's ability to clear it and is a product of glucose metabolism

74

What levels of lactate are significant? Severe?

> 2mEq/L is significant, > 5 mEq/L with metabolic acidosis is severe

75

What is Type A lactic acidosis?

Seen in hypovolemic or hemorrhagic shock with inadequate oxygen delivery

76

What is Type B lactic acidosis?

Occurs despite normal oxygen delivery

77

Causes of metabolic acidosis from wide AG (unmeasured anions) (4)

1. Hypoperfusion
2. Lactic acidosis
3. DKA
4. Renal failure

78

Causes of metabolic acidosis from measured anions (4)

1. Hyperchloremia
2. Normal saline and saline containing fluids
3. Renal tubular acidosis
4. Bladder reconstructions

79

Causes of metabolic acidosis from free water excess such as hyponatremia and dilation acidosis? (6)

1. Hypotonic fluid administration
2. Sodium loss
3. Diarrhea
5. Hyperosmolar fluids such as mannitol and alcohol
6. Hyperproteinemia

80

Causes of metabolic alkalosis?

1. Hyperventilation of patient with hx of CO2 retention such as COPD
2. Sodium gain from things such as sodium bicarb and massive transfusions
3. Chloride loss such as in NGT suctioning

81

Does sodium bicarb improve long term outcomes?

It has not been shown to

82

What would be an example of a metabolic disorder that we may intentionally cause?

Acidosis caused by permissive hypercapnia to prevent ventilator related lung injury because treatment may cause reverse effects

83

What is the A-aDO2 equation?

FIO2 (760-47) - PaCO2/0.8

84

What does A-aDO2 approximate?

Partial pressure of oxygen in the alveoli

85

What does A-aDO2 allow for the calculation of?

Alveolar-arterial gradient of oxygen and the amount of respiratory/cardiac shunt

86

What is a normal A-aDO2?

5-10mmHg, although age or chronic lung disease may cause an increase

87

What is the required cardiovascular monitoring and frequency?

BP and HR monitoring every 5 minutes

88

When is thermoregulation monitoring required?

When clinically significant changes in body temp are anticipated or suspected or for SCIP protocol

89

What must be done if we omit a standard of care?

Reason for omission must be charted

90

What does the beer-lambert equation describe?

The law of absorption

91

What is the law of absorption in relation to pulse oximetry?

If a known intensity of light illuminates a chamber of known dimensions then the concentration of a dissolved substance can be determined

92

What must light absorption be measured at?

Wavelengths equal to the number of solutes
(More solutes such as oxygen = more absorption)

93

4 variations of hemoglobin?

1. Oxyhemoglobin (HbO2)
2. Deoxyhemoglobin
3. Methemoglobin (metHb)
4. Carboxyhemoglobin (COHb)

94

What is the gold standard number of wavelength for pulse-oximetry?

4 wavelengths

95

What does more wavelengths give us in pulse-oximetry?

Greater assurance of looking at HbO2 and Deoxyhemoglobin

96

What are the 5 layers that light is transmitted through for pulse-oximetry?

1. Skin
2. Soft tissue
3. Venous blood
4. Arterial blood
5. Capillary blood

97

What type of movement increases length of the light path and increases absorbency?

Pulsatile expansion of the artery

98

How was the problem of ambient light solved for pulse-oximetry?

alternating red/infared light

99

How do we solve low perfusion issues with pulse-oximetry readings?

signal amplified, but the artifact is also amplified

100

Describe venous blood pulsations

longer signal averaging time, slower to report changes

101

What is an intervention we utilize that can also absorb light from a pulse-ox?

Intravenous dyes

102

What is the definition of SaO2?

Ratio of oxyhemoglobin to all hemoglobin

103

What are fingers relatively sensitive to?

vasoconstriction

104

Where is the detection of desaturation and resaturation slower on a pulse-ox?

Peripherally

105

Which finger do we avoid placing the pulse-ox?

index finger

106

What is a more reliable place for a pulse-ox with epidural blocks?

Toes due to vasodilation

107

What are three other areas for pulse-ox placement that are less affected by vasoconstriction and reflect desaturation quicker?

tongue, cheek, forehead

108

How accurate is a pulse-ox?

+/- 2% when measured against ABGs if sat is >70%

109

Do anesthetic vapors affect pulse-ox?

no

110

What type of pressures do pulse-oximeters have difficulty detecting?

high partial pressures

111

At what wavelength range does carboxyhemoglobin absorb as much light as oxyhemoglobin?

660 nm

112

What is the effect of carboxyhemoglobin on SpO2?

Falsely elevates SpO2; for every 1% increase COHb will increase SpO2 by 1%

113

What is the COHb of many smokers?

>6%

114

Who invented the sphygmomanometer?

Samuel von Basch

115

What are korotkoff sounds produced by?

turbulent flow beyond the partially occluding cuff

116

Phase 1 korotkoff sound?

The most turbulent/audible (SBP)

117

Phase 2-3 korotkoff sound?

Sound character changes, turbulent flow decreases

118

Phase 4-5 korotkoff sound?

muffled/absent sounds (DBP)

119

4 limitations to auscultation of blood pressure?

1. Decreased peripheral flow
2. Changes in vessel compliance
3. Shivering
4. Incorrect cuff size

120

What is the maximum cuff pressure for adults? neonates?

300 mmHg for adults; 150 mmHg for neonates

121

Cuff bladder standards for BP monitoring?

40% of arm circumference
80% of length of upper arm

122

4 Descriptors of automatic non-invasive techniques for BP?

1. Maximal amplitude is MAP
2. SBP and DBP calculated from algorithm
3. SBP usually 25-50% of MAP amplitude
4. DBP is least accurate

123

When is automatic non-invasive techniques for BP measurement rough equal to arterial pressure?

when MAP is 75 mmHg or lower

124

Standards of non-invasive BP monitoring?

+/- 5 mmHg, can be larger depending on the circumstances

125

Non-invasive BP measuring of MAP during hypertension?

underestimation

126

Non-invasive BP measuring of MAP during hypotension

overestimation

127

What is the more reliable way to determine blood pressures from non-invasive monitoring?

trends

128

Clinical limitations of non-invasive BP monitoring?

extremes of heart rate and pressure

129

4 trauma factors related to frequent cycling of non-invasive blood pressure?

1. Coagulopathies
2. Peripheral neuropathies
3. Arterial/venous insufficiency
4. Compartment syndrome

130

What is the most common monitoring site for arterial blood pressure?

Radial, it is easy to access and complications are uncommon

131

4 steps to the Allens' test?

1. Examiner compresses radial and ulnar artereis
2. Patient makes a tight fist which exsanguinates the palm
3. Patient opens hand
4. Examiner releases ulnar artery and color to the palm should return in less than 10 seconds

132

What is the diagnostic accuracy of the Allens' Test?

80%

133

What is unique about the transfixion technique of arterial line placement?

Front and back walls are punctured intentionally and the catheter is withdrawn until pulsatile blood flow appears

134

Is the transfixion technique of arterial line placement associated with more frequent complications?

no

135

5 other common sites of arterial blood pressure monitoring?

1. Brachial: not the best collateral flow
2. Posterial tibial
3. Axillary
4. Dorsalis pedis: smaller and more difficult
5. Femoral: higher complication rate

136

Describe the automatic flush function of A-lines

1. 1-3 mL/hr to prevent thrombus formation
2. lack of dextrose
3. lack of heparin

137

Where do we typically level an A-line?

Midchest/midaxillary line to look at the aortic root

138

How is the waveform maximized with A-lines?

limit stopcocks, limit tubing length, and non-distensible tubing

139

What is distal pulse amplification due to?

Due to impedance changes along vascular tree

140

What are the changes in A-line as pressure wave moves to periphery?

1. Arterial upstroke steeper
2. Systolic peak higher
3. Dicrotic notch later because longer for wave to transmit
4. End-diastolic pressure lower

141

What is the summation of sine waves?

fundamental wave + harmonic wave = typical pressure wave (fourier analysis)

142

What does the square wave test occur from?

From compressing fast flush, rapid rise in pressure and waiting for it to respond

143

What should we see post square wave form test?

1-2 rebound oscillations at bottom of square

144

What does the damping capability of A-line systems do?

1. Decreases system resonance
2. Prevents exaggerated waveforms

145

What do we see with an underdamped A-line?

Systolic pressure elevated, more exaggerated movement and steeper systolic upstroke

146

What issues could we have with an underdamped A-line?

tubing too long, wrong tubing

147

What issues could we have with an overdamped A-line?

air bubble, tubing too long, pressure bag empty

148

What do we see with overdamped A-lines?

1. Systolic pressure decreased
2. Decreased pulse pressure
3. Loss of detail

149

7 pathology that can cause A-line waveform changes?

1. Age: loss of distensibility
2. Atherosclerosis
3. Embolism
4. Arterial dissection
5. Shock
6. Hypothermia
7. Vasopressor infusions

150

When compared with central aortic pressure, peripheral arterial waveforms have a _____ pulse pressure?

Wider pulse pressure because higher SBP and lower DBP in periphery

151

What initially occurs as a result of increased lung volume from the ventilator delivering a breath? (5)

1. Compression of lung tissue
2. Increased LV preload
3. Increases intrathoracic pressure
4. Decreases afterload
5. Increased LV stroke volume

152

What occurs as intrathoracic pressure continues to increase as the ventilator delivers a breath?

1. Reduction in venous return and right heart preload
2. Increased PVR causes increased R heart afterload
3. R heart stroke volume drops
4. Left heart preload falls
5. Arterial BP declines

153

What is systolic pressure variation (SPV)?

Increase or decrease in systolic pressure in relation to end-expiratory presssure

154

What is normal SPV in ventilated patients?

7-10 mmHg

155

With SPV what is the normal increase?

2-4 mmHg

156

With SPV what is the normal decrease?

5-6 mmHg

157

What does increased SPV indicate?

early hypovolemia

158

What is the pulse pressure variation (PPV)?

Utilizes maximum and minimum pulse pressures over entire respiratory cycle

159

What is a normal PPV?

13-17%

160

How do you calculate PPV?

[(PPmax-PPmin)/(PPmax+PPmin)]/2

161

What does an increase in PPV indicate?

Patient could benefit from fluids

162

What is stroke volume variation (SVV)?

Computer analysis of arterial pulse pressure waveform to correlate resistance and compliance based on age and gender to calculate SV

163

What is the equation for SVV?

SV max - SV min / SV mean

164

What is a normal SVV?

10-13%

165

What is required to calculate SVV?

ventilated patient with stable RR and Vt 8cc/kg

166

When is SVV not accurate?

Severe tachycardia and dysrhythmias

167

2 descriptors of non-diverting sampling?

1. Gas is not removed from the circuit
2. Also called main-stream

168

2 descriptors of diverting sampling?

1. Gas IS removed from the circuit for analysis elsewhere
2. Also called side-stream

169

4 challenges of mainstream sampling?

1. Water vapor
2. Secretions
3. Blood
4. More interfaces for disconnections

170

4 challenges of sidestream sampling?

1. Kinking of sampling tube
2. Water vapor
3. Failure of sampling pump
4. Leaks in the line

171

What is Dalton's Law?

The total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of each gas

172

What is mass spectrometry?

Concentration determined according to mass

173

How many gases can mass spectrometry calculate?

Up to eight different gases

174

What can mass spectrometry calculate?

Partial pressure from measured proportion (%)

175

What is the total partial pressure from ventilated patients?

713 mmHg

176

What is normal ETCO2?

35.65 mmHg

177

What does infared analysis calculate?

The number of molecules based on absorption of IR radiation (partial pressures)

178

What does more molecules mean with infrared analysis?

more IR radiation is absorbed and the more motion from IR (or partial pressure)

179

How must gas monitoring be calibrated?

For high and low concentrations

180

What does gas monitoring sampling inside the inspiratory limb give us? (2)

1. Ensures oxygen delivery
2. Analyzes hypoxic mixtures

181

What does gas monitoring sampling on the expiratory side give us? (2)

1. Ensures complete pre-oxygenation "denitrogenation"
2. ET O2 above 90% is adequate

182

Is there oxygen monitoring at auxiliary sites?

no

183

3 reasons for the low alarm with gas monitors

1. Pipeline crossover
2. Incorrectly filled tanks
3. Failure of a proportioning system

184

2 reasons for high alarms with gas monitors

1. Premature infants
2. Chemotherapeutics drugs such as bleomycin

185

What does airway pressure monitoring assess?

Patients mechanical and or spontaneous ventilation

186

What does airway pressure monitoring determine?

Presence of PEEP

187

3 descriptors of mechanical airway pressure gauges?

1. No recording data so no trends
2. No alarm system
3. Must be continually scanned

188

2 descriptors of electronic pressure gauges?

1. Built within ventilator or anesthesia machines
2. Alarm system is integrated

189

When are low peak inspiratory pressure alarms on?

When the ventilator is on

190

When does a low peak inspiratory pressure alarm go off?

When pressure does not exceed a preset minimum

191

Causes of low peak inspiratory pressure alarms? (5)

1. Disconnects
2. Apnea
3. Vent failure
4. Leaks in system
5. OGT in lung on suction

192

What do you want to do if you see a low peak inspiratory pressure alarm?

Start at one end of circuit and trace it to another, the most common causes is for something to get disconnected

193

When is a high pressure alarm non-functional?

Pressure controlled ventilation

194

What is a high pressure alarm usually fixed at?

50-80 cmH20

195

3 causes of high pressure alarms?

1. Obstructions
2. Reduced compliance
3. Coughing/straining

196

Describe sustained elevated pressure alarms

Pressure that remains elevated during respiratory cycle

197

3 causes of sustained elevated pressure alarms?

1. Improperly adjusted APL valve
2. Activation of oxygen flush system
3. Malfunctioning PEEP

198

What type of pattern does the reaction of a single muscle fiber to a stimulus follow?

all-or-none pattern

199

What does the repose of the whole muscle depend on?

How many muscle fibers are activated

200

4 most common patterns of nerve stimulation?

1. Single
2. TO4
3. Tetanic Stimulation
4. Post-tetanic stimulation

201

How many Hz is usually used for single twitch nerve stimulation?

0.1-1.0 Hz

202

What type of muscle relaxants do we see fade with?

Non-depolarizers such as Rocuronium

203

What is the TOF ratio?

4th twitch/1st twitch

204

What would be the issue with having no twitches?

Will be unable to reverse and giving something such as neostigmine could actually cause the block to be deeper

205

What do we expect to see with surgical blocks?

A couple of twitches

206

Describe the diaphragm and resistance to both types of NMBD? (3)

1. Needs up to 2x as much drug for identical block
2. Recovers faster than periphery
3. Onset of blocks is faster than adductor pollicis

207

What do we consider if we see the diaphragm moving before the thorax after NMBD reversal?

This does not indicate adequate ventilation!

208

What are the most sensitive muscles to paralysis?

Orbicularis occuli, masseter, upper airway

209

What most closely reflects laryngeal adductor muscle?

Corrugator supercilli of facial nerve

210

What does the EEG show us?

Summation of excitatory and inhibitory PSP's

211

How are electrodes placed for EEGs?

So that surface anatomy relates to cortical regions

212

Where are the odd numbers found with EEGs?

all are on the left side of the cranium

213

What does the "z" indicate with EEG electrodes?

midline along the central sulcus

214

EEG beta signal Hz for Awake?

> 13 Hz

215

EEG alpha signals Hz for Eyes closed?

8-13 Hz

216

EEG theta and delta signals showing depressed EEG?

Theta: 4-7 Hz
Delta: <4 Hz

217

What is a processed EEG a combination of?

16 channel EEG to 2-4 channels

218

What does an ideal EEG show?

Bilateral hemispheres

219

What does the BIS monitor do?

Processes EEG signal to monitor LOC

220

What is the lag time of BIS monitors?

20-30 seconds

221

What was BIS monitor use proposed for?

To prevent intraoperative awareness

222

3 facts of the B-Unaware trial

1. Multicenter
2. Compared age-adjusted end-tidal MAC
3. to BIS 40-60, no significant difference

223

What is temperature mainly regulated by?

Hypothalamus

224

What is temperature control mediated by? (4)

Dopamin, norepinephrine, acetylcholine, prostaglandins

225

What nerve fibers generally detect cold?

a-delta fibers

226

What nerve fibers generally detect warmth?

c fibers

227

What does temperature vary by?

1. Sex
2. Exercise
3. Food intake
4. Thyroid function
5. Drugs such as alcohol, nicotine, anesthetics

228

Describe heat transfer significance in surgery as radiation

Major type of loss in surgical patients

229

Describe heat transfer significance in surgery as conduction

negligible, patients are on thick foam pads

230

Describe heat transfer significance in surgery as convection

negligible, rate of air speed in OR small

231

Describe heat transfer significance in surgery as evaporation

less than 10% in the absence of sweating

232

Initial temperature in GA?

rapid decrease

233

What is the initial rapid decrease of temperature in GA due to? (3)

1. Volatiles causing direct vasodilation
2. Increases heat loss
3. Preferentially distributes more heat to periphery than core

234

Continual temperature drop due to GA occurs when and because of what

1. Heat loss exceeds production
2. Occurs hour 2-4

235

Describe the plateau phase of hypothermia with GA?

1. thermal steady state
2. Heat loss equals heat production leading to being unable to warm-up
3. Occurs 3-4 hours after anesthesia
4. Vasoconstriction prevents loss of heat from core but peripheral heat continues to be lost

236

5 factors associated with hypothermia in regional anesthesia such as epidural and spinals?

1. Decreases the threshold that triggers vasoconstriction
2. Induces vasodilation in the periphery below area of the block
3. Redistributes heat to periphery similar to GA
4. Decreases shivering threshold
5. Sedatives also inhibit thermoregulatory control

237

What is normal core temp?

37 degrees celsius or 98.6 F

238

5 complications associated with hypothermia

1. 3x the incidence of morbid cardiac outcome
2. 3x the incidence of wound infection
3. Impairs platelets, PT, and PTT function
4. Increase need for transfusion by 20%
5. Increases duration of NMB

239

4 benefits of hypothermia

1. Improved outcome during recovery from cardiac arrest
2. Protective against cerebral ischemia
3. More difficult to trigger MH
4. Reduces metabolism 6% per degree C

240

4 common sites for core temperature monitoring

1. Nasopharynx
2. Esophagus
3. Pulmonary artery
4. Tympanic membrane

241

5 factors associated with nasopharynx monitoring of temperature?

1. Close to hypothalamus
2. Not affected by inspired gas if intubated
3. Easy to find
4. Sensor must contact posterior wall
5. Epistaxis

242

Where do we place esophageal monitoring for temperature?

lower 1/4 to 1/3 of esophagus between the heart and descending aorta

243

What temperature monitoring site could we have maximal heart sounds?

esophageal

244

5 not so good sites of core temperature monitoring?

1. Oral
2. Axillary
3. Rectal
4. Bladder
5. Skin

245

What is considered room temp?

70 degrees F = 21 degrees C
65 degrees F = 18 degrees C

246

What does a single blanket reduce heat loss by? 3 blankets?

1 = 30% reduction in heat loss
3 = 50% reduction in heat loss

247

What do we do with our ETCO2 to approximate PaCO2?

Add about 4 mmHg

248

What would be the issue with with approximating PaCO2 from ETCO2 in COPD patients?

COPD patients would have a higher PaCO2 than approximated due to increased alveolar dead space

249

5 physiological effects from hypercarbia?

1. Respiratory acidosis
2. Increase cerebral blood flow due to cerebral vasodilation
3. Increases ICP in susceptible patients
4. Increased pulmonary vascular resistance
5. Potassium shifts from intracellular to intravascular

250

4 physiological effects from hypocarbia?

1. Respiratory alkalosis
2. Decreased CBF
3. Potassium shifts to the intracellular space
4. Blunts normal urge to breathe

251

6 other things that ETCO2 informs us of other than ventilation

1. Pulmonary blood flow
2. Aerobic metabolism
3. ETT/LMA placement
4. Integrity of breathing circuit
5. Adequacy of cardiac output
6. VD to Vt

252

What is Bohr's equation?

VD/Vt = (PaCO2 - PeCO2)/(PaCO2)

253

What is capnometry?

The measurement and quantification if inhaled/exhaled CO2

254

What is capnography?

The method of measurement but also the graphic display or time of inhaled/exhaled CO2

255

What is the best method to confirm endotracheal intubation?

Detection of carbon dioxide breath-by-breath

256

Describe what you would see on a monitor to confirm ETT placement?

3 successive CO2 waveforms of the same height

257

3 descriptors of chemical indicators of ETT placement

1. Semi-quantitative
2. Color change of pH sensitive paper
3. A type of capnometer, doesn't give waveform but does give quantitative information

258

Relate CO2 concentration to IR reaching the detector

The greater the CO2 in the sample, the less IR that reaches the detector

259

What is the issue with sidestream analyzers of CO2?

They have a delay time and rise time

260

4 CO2 monitor requirements?

1. CO2 reading within +/- 12% of actual value
2. Manufacturers must disclose interference caused by ethanol, acetone,, halogenated volatiles
3. Must have a high CO2 alarm for inhaled and exhaled CO2
4. Must have an alarm for low exhaled CO2

261

Two reasons for low exhaled CO2 alarm

1. D/c
2. No pulse

262

CO2 production/Delivery to Lungs causes of Increased PetCO2 (7)

1. Increased metabolic rate
2. Fever/Sepsis
3. Seizures
4. MH
5. Thyrotoxicosis
6. Increased cardiac output
7. Bicarb admin

263

Equipment malfunction causes of increased PetCO2 (3)

1. Rebreathing
2. Exhausted CO2 absorber
3. Faulty inspiratory/expiratory valves

264

Alveolar ventilation causes of increased PetCO2 (5)

1. Hypoventilation
2. Respiratory center depression
3. Neuromuscular disease
4. High spinal anesthesia
5. COPD

265

Equipment causes of decreased PetCO2 (4)

1. Ventilator disconnect
2. Esophageal intubation
3. Complete airway obstruction
4. Leak around ETT

266

CO2 Production/Delivery to lungs causes of decreased PetCO2 (5)

1. Hypothermia
2. Cardiac arrest
3. Pulmonary embolism
4. Hemorrhage
5. Hypotension

267

Alveolar ventilation cause of decreased PetCO2?

Hyperventilation

268

What is the simple and most widely used technique for monitoring exhaled CO2?

Time capnogram

269

What does the time capnogram display?

inspiratory and expiratory phases over time

270

Phase 1 of capnogram? (3)

1. Baseline
2. Exhalation of dead space from central conducting airways
3. Essentially no CO2

271

Phase 2 of capnogram? (3)

1. Expiration
2. Sampling of gases at transition of airway and alveoli
3. Normally steep

272

Phase 3 of capnogram? (3)

1. Plateau phase
2. Normally representative of CO2 in alveolus
3. Can be representative of ventilation heterogeneity

273

Phase 0 or 4 of capnogram? (2)

1. Inspiration of Fresh gas flow (FGF)
2. Remaining CO2 washed out

274

Where is ETCO2 measured?

End-point of phase 3 at the beta angle

275

Characteristics of capnogram of inadequate seal around ETT or faulty inspiratory valve (3)

1. Reduced plateau phase 3
2. No beta angle
3. Sloped phase 4 inspiratory phase

276

Characteristics of capnogram of hyperventilation (2)

1. Reduced inspiratory phase and expiratory phase over time
2. Seen during induction

277

Characteristics of capnogram of hypoventilation (3)

1. Increased expiratory upstroke
2. ETCO2 increases, alveoli will eventually collapse causing an increased risk of hypoxemia
3. Seen as the case goes on

278

Characteristics of capnogram of increased airway resistance (4)

1. P3 slope increased
2. P2 upstroke decreased
3. Beta angle and inspiratory phase normal at beginning but reduced over time
4. Shark fin appearance of wave

279

3 causes of increased airway resistance and which is the most common?

1. Bronchospasm
2. Increased Secretions
3. COPD (most common)

280

What type of patients is it normal to see cardiac oscillations on capnogram?

Skinny people

281

Characteristics of capnogram of patients re-breathing or soda lime exhaustion (2)

1. Doesn't return to baseline CO2
2. Should not be rebreathing CO2

282

Characteristic of capnogram for NMBD's wearing off?

Curare cleft, the patient doesn't finish inspiring like normal

283

How do you differentiate esophageal intubation/cardiac arrest capnogram waveform from patient disconnect?

Esophageal intubation/cardiac arrest will have a slow decline, disconnect will show a flatline and immediate drop