Monitoring the Anesthetized Patient - 2 Flashcards
How to measure minute ventilation (V)?
TV (tidal volume) x frequency
What is the end product of cellular metabolism?
CO2
What is CO2 transported as in the venous system?
HCO3-
The production and elimination of CO2 is linked to ____, perfusion, and _____.
The production and elimination of CO2 in linked to METABOLISM, perfusion, and VENTILATION.
Capnography is a noninvasive method to measure systemic ____, ____, ____, and cardiac output.
Capnography is a noninvasive method to measure systemic METABOLISM, PULMONARY PERFUSION, PULMONARY VENTILATION, and cardiac output.
If CO2 production (metabolism), cardiac output, and pulmonary perfusion are all constant, but there is a change in the End-tital CO2, what caused the change?
A change in ventiation
EtCO2 monitors exhaled CO2 noninvasively and is an indirect measurement of ____ CO2.
Arterial CO2 (PaCO2)
EtCO2 will be ____ mmHg less than PaCO2.
3 - 5
What is the most useful value for detection of apnea and hypoventilation?
EtCO2
What are the advantages of a sidestream capnography sampling tube?
- Light weight
- Ease of manipulation
- Ability sample other gases
- Small sample chamber
What are the disadvantages of a sidestream capnography sampling tube?
- Need to scavenge aspirated gases
- Plugging of sample line by secretions
- 2-3 second delay
- Dilution of sample from leaks in breathing circuit
What are the advantages of a mainstream capnography sampling tube?
- No scavenging of aspirated gases needed
2. Real-time measurement
What are the disadvantages of a mainstream capnography sampling tube?
- Added dead space
- Weight can cause kinking of the ET tube
- Sensing chamber can be contaminated by secretions
- Patients may be burned by heated cuvette (sensors are heated to prevent condensation of water vapor)
What are 5 specific causes of increased EtCO2 values?
- Metabolism : fever, malignant hyperthermia
- Pulmonary perfusion : increased CO, increased BP
- Alveolar ventilation : hypoventilation, rebreathing
- Technical errors : exhausted soda lime, faulty one-way valves, inadequate fresh gas flow
What are 5 specific causes of decreased EtCO2 values?
- Metabolism : hypothermia, hypothyroidism, muscle relaxants
- Pulmonary perfusion : decreased CO, decreased BP, cardiac arrest, pulmonary embolism
- Alveolar ventilation : hyperventilation, apnea, partial esophageal obstruction
- Technical error : leak in sample line, patient disconnect, high FGF in NRB system
What is the typically difference between EtCO2 and PaCO2 in a horse?
EtCO2 ~ 10-15 mmHg
What is normal blood pH?
7.4
What do you call an increased PaCO2?
Respiratory acidosis
What do you call a decreased PaCO2?
Respiratory alkalosis
What do you call an increased HCO3-?
Metabolic alkalosis
What is PaCO2?
The partial pressure of CO2 in arterial blood
Would a decreased PaCO2 likely be associated with hyperventilation or hypoventilation?
Hyperventilation
Based on the side effects of many of the drugs we give patients for anesthesia, would you most commonly see an increase or decrease in PaCO2?
Increased PaCO2
What is PaCO2 in a normal, awake patient?
35 - 45 mmHg
What value will tell the TRUE PaCO2 - EtCO2 difference?
ABG (arterial blood gas)
What are 3 causes of dark pink mucous membranes?
- Vasodilation
- Endotoxemia
- Increased CO2
There are 5 factors that can affect the function and accuracy of a pulse oximeter. Name 3.
- Movement artifact
- Dark mucous membranes
- Fluorescent light
- Poor peripheral blood flow (hypotension)
- Increased carboxyhemoglobin and methemoglobin levels
Pulse oximetry is most helpful when patients are __1__ or __2__.
- Breathing room air
2. Transitioning (induction, recovery)
What is an ideal SpO2?
> 93-95 %
What is a normal PaO2 in room air?
90-100 mmHg
A normal PaO2 in patients breathing 100% oxygen should be what?
> 250-650 mmHg
There are 5 consequences of hypothermia. Name 3.
- Decreased MAC
- Impaired platelet function
- Decreased coagulation
- Impaired wound healing
- Increased risk of surgical infection
What are the consequences of hyperthermia?
- Increased circulatory work
- Cellular hypoxia
- Increased metabolic rate
How would you treat hyperthermia? (Name 2)
- Active cooling
2. Supplement with O2
What is the purpose of the demand valve for large animals?
Demand valve delivers intermittent positive pressure ventilation
What volume of oxygen does the demand valve deliver each minute?
200 L/min
There are multiple indications for the use of the demand valve. What are 3 of those indications?
- Apnea
- Head trauma
- Significant hypoventilation
- Intra-thoracic surgery
- Horse anesthesia
- Use of neuromuscular blocking agents
What does the bellow take the place of in the breathing circuit?
Reservoir bag
Which animals do you NOT wean from IPPV? What is the exception?
Do not wean horses, except in brain cases (head trauma, tumor, etc.)
What 2 steps are involved in weaning a patient from IPPV?
- Lower the respiratory rate to increase PaCo2
2. Discontinue the inhalant to decrease CO2 set point in the brain