RESPIRATORY PATHOPHYSIOLOGY modules 15-23 Flashcards
List the monitors of venous air embolism from most sensitive to least
TEE
Precordial doppler
EtCO2
CVP
List the positions that increase the risk of venous air embolism from greatest to least
Sitting
Supine
Prone
Lateral
Signs and symptoms of venous air embolism
Air on TEE Mill wheel murmur on precordial doppler Decreased EtCo2 HoTN Dysrhythmias Hypoxia Cyanosis CV collapse
What is the treatment for venous air embolism
100% FiO2 Flood the surgical field D/C insufflation Left lateral decubitus positioning Air aspiration via CVC Hemodynamic support
How does a venous air embolism occur
Air is entrained into bloodstream via an open vessel above the level of the heart
Increased risk in spontaneously ventilating patients
What are consequences of air trapped in the pulmonary circulation
- Increased PA pressure
- Increased RV stroke work index
- RV failure
- Decreased pulmonary venous return
- Decreased LV preload
- Decreased CO
- Asystole and CV collapse
How does air trapped in the pulmonary circulation affect the left side of the heart?
- Decreases LV preload
- Decreases CO
- Leads to asystole and CV collapse
What interventions reduce pulmonary vascular resistance
Hyperventilation
Nitric oxide
NTG
What interventions increase pulmonary vascular resistance (5)
Hypoxia Hypercarbia N2O hypothermia PEEP
What is PAP in pulmonary HTN
PAP > 25 mmHg
What pathophysiologic alterations increase pulmonary vascular resistance
Increased vascular smooth muscle tone
Vascular cell proliferation
Pulmonary thrombi
What effects can pulmonary HTN have on RV workload
Increases
Progression to RV failure (cor pulmonale)
Anesthetic considerations for patients with pulmonary HTN
- Give medications for PVR reduction preoperatively
- Preload dependent d/t fixed CO
- Aggressive HoTN treatment
- Epidural over spinal anesthesia
- Inhaled nitric oxide
- Jet ventilation
Describe the process of LV preload dependence in the patient with pulmonary HTN
Increased RV afterload causes RV dilation, hypertrophy and systolic failure
Decreased output from RV
HoTN d/t decreased LV preload
Intraventricular septum bowing into LV compromises filling
How does tricuspid regurgitation occur d/t pulmonary htn
Increased RV volume at end diastole d/t decreased RV stroke volume
Stretches tricuspid annulus leading to regurg
Causes of pulmonary HTN
COPD Hypoxemia & Hypercarbia left heart dysfunction MV disease CHD Connective tissue disorders Thromboembolism Portal HTN
What is the normal pulmonary vascular resistance
150-250 dynes-sec-cm5
Equation for PVR
PVR = ([mean PAP - PAOP]/CO x 80)
What can increase pulmonary vascular resistance
Hypoxemia Hypercarbia Acidosis SNS stimulation Pain Hypothermia Increased intrathoracic pressure Mechanical ventilation PEEP Atelectasis N2O Ketamine Desflurane
Anesthetics that increase pulmonary vascular resistance
N2O
Ketamine
Desflurane
Drugs that decrease pulmonary vascular resistance
Nitric oxide NTG PDE inhibitors PGE1/2 CCB ACE inhibitors
What can decrease pulmonary vascular resistance
Increased PaO2 Hypocarbia Alkalosis Decreased intrathoracic pressure Spontaneous ventilation Avoid coughing/straining NO NTG PDE inhibitors PGE1/2 CCB ACE-i
How is preload managed in the patient with pulmonary HTN
Requires adequate preload, therefore treat HoTN aggressively
In a gravid patient with pulmonary HTN, what are the CV effects of uterine contractions and the treatment
Effects = Too much preload, PA HTN, RV dysfunction
Treatment = NTG
Hgb has an affinity for carbon monoxide that is ___ times greater than O2
200 times
Carbon monoxide shifts the oxyhemoglobin dissociation curve which direction
Left
What is the treatment for carboxyhemoglobinemia?
Supplemental O2
How does soda lime affect carbon monoxide levels
If it is desiccated the risk of CO formation is greatest
What type of metabolism is a result of carboxyhemaglobinemia
Anaerobic metabolism because O2 is not released at tissues
This leads to metabolic acidosis due to impaired oxidative phosphorylation and reduced ATP production
Hyperbaric O2 is indicated if CoHgb exceeds what percent of total hgb?
25%
When treating CoHgb, 100% O2 should be administered until the CoHgb is less than __%
5%
What are strong indications for mechanical ventilation VC \_\_ Inspiratory force \_\_ PaO2 \_\_ A-a gradient \_\_ PaCO2 \_\_ RR \_\_
VC <15 mL/kg Inspiratory force <25 cmH2O PaO2 <200 mmHg on 100% FiO2 A-a gradient >450 mmHg on 100% FiO2 PaCO2 >60 mmHg RR >40 or <6 bpm
What drugs can be administered via an ETT
NAVEL Narcan Atropine Vasopressin Epinephrine Lidocaine
What is the normal A-a gradient
<10 - 15 mmHg
What are the benefits of endotracheal intubation
- Patent airway
- Controlled ventilation
- Ventilate with high airway pressure
- Secure airway
- Removal of secretions
- Lung isolation
- Medication administration
What are the best predictors of postop pulmonary complications for patient undergoing pulmonary surgery
FEV1 __
DLCO __
VO2 max __
FEV1 <40% predicted
DLCO <40% predicted
VO2 max <15 mL/kg/min
What are the 3 categories of predictors of postop pulmonary complications following pulmonary surgery.
Lung parenchymal function (gas exchange) Respiratory mechanics (airflow) Cardiopulmonary reserve
If a VO2 max is not available to assess postop pulmonary complications, what question can give similar information
Ask if patient can climb 2 flights of steps
If no, the patient is at risk
What are the 3 categories for absolute indications for OLV
Isolation to avoid CONTAMINATION
Control of ventilation distribution
Unilateral bronchopulmonary lavage
What are absolute indications for OLV
Infection Massive hemorrhage Bronchopleural fistula Surgical opening of major airway Large unilateral cyst/bullae Hypoxemia d/t lung dz Pulmonary alveolar proteinosis
What high priority relative indications for OLV and surgical exposure
Thoracic aortic aneurysm Pneumonectomy Thoracoscopy Upper lobectomy Mediastinal exposure
DLT size for males and females based on height
Female:
<160 cm = 35 french
>160 cm = 37 french
Male:
<170 cm = 39 french
>170 cm = 41 french
Approximate DLT insertion depth for males and females
Males = ~29 cm Females = ~27 cm
What data can aid in choosing the proper DLT size
CXR and CT to assess for abnormalities in tracheobronchial anatomy
At what age do we use DLT for pediatric patients
at 8 years
Why are DLT not manufactured for pediatric patients <8 yo
Because the lumens would be so narrow that resistance to airflow would be incredibly high
What are the options for lung isolation in children <8 years
Bronchial blocker
Single lumen ETT in mainstem bronchus
What is the cause of shunt during OLV.
What does this cause
Mixing blood from non-dependent (non-ventilated) lung and dependent (ventilated) lung
Causes hypoxemia
Which lung is better ventilated in the lateral decubitus position
Non-dependent lung (which is not ventilated)
Which lung is better perfused in the lateral decubitus position
The dependent (ventilated) lung
What is the cause of V/Q mismatch in the lateral decubitus position for OLV
The non-dependent lung is better ventilated but poorly perfused and it is also the non-ventilated lung
Mechanical ventilation considerations for OLV initiation FiO2 \_\_ Vt \_\_ RR \_\_ PEEP \_\_
FiO2 100%
Vt 6-8 mL/kg ibw
RR 12-15 bp,
PEEP 5-10 cmH2O
What maneuver is helpful before initiating OLV
Alveolar recruitment maneuver
How can the I:E ratio be adjusted to improve OLV
Adjust if the patient has an expiratory air flow limitation
i.e. increase I:E to allow for full exhalation
What type of anesthetic may be beneficial for OLV
TIV because volatile anesthetics can inhibit the HPV response
What steps are taken to address hypoxemia in OLV
- 100% FiO2
- Confirm position of DLT w/ fiber
- r/o physiologic causes (mucus plug, PTX etc)
- Apply CPAP to NON-dependent lung
- PEEP 5-10 cm H2O to DEPENDENT lung
What steps may be taken if initial efforts to address hypoxemia are unsuccessful
- Intermittently reinflate non-dependent lung
- Ligate pulmonary artery
- Eliminate drugs that inhibit HPV response
What is the result of the DLT being in too far
Upper lobe is NOT ventilated, increasing hypoxemia
What is the result of DLT not being deep enough
Failure to achieve lung separation
BS bilateral
What is the result of DLT in the wrong bronchus
The wrong lung is collapsed
How does hypoxemia affect the A-a gradient
INCREASES gradient
How does PPV affect V/Q mismatch
PPV increases alveolar pressure and makes it part of West zone 1, increasing dead space
What is seen when confirming DLT placement with a fiber bronchoscope
Tracheal lumen = incomplete C-rings open posteriorly Blue cuff -in correct bronchus -not herniating Right bronchus has 3 takeoffs Left bronchus has 2 takeoffs
Left-sided DLT confirmation by auscultation
Clamp TRACHEAL lumen with both cuffs inflate
Describe BS in each condition: Correct In too far (left) In trachea In too far (right)
Correct:
left = yes, right = no
In too far (left):
left = yes, right = no
In trachea:
left = yes, right = yes
In too far (right):
left = no, right = no
Left-sided DLT confirmation by auscultation
Clamp BRONCHIAL lumen with both cuffs inflate
Describe BS in each condition Correct In too far (left) In trachea In too far (right)
Correct:
left = no, right = yes
In too far (left):
left = no, right = no
In trachea:
left = no, right = no
In too far (right)
left = no, right = no
Left-sided DLT confirmation by auscultation
Clamp BRONCHIAL lumen and deflate cuff
Describe BS in each condition Correct In too far (left) In trachea In too far (right)
Correct
Left = yes, right = yes
In too far (left):
left = yes, right = no
In trachea:
left = yes, right = yes
In too far (right):
left = no, right = yes
Steps for lung isolation with OLV
- Inflate bronchial cuff
- Clamp lumen distal to y-piece of operative lung
- Open lumen to operative side
- Adjust FiO2
- Vt 6 ml/kg to keep PIP20
- Adjust RR to maintain PaCO2 35-45
- Perform alveolar recruitment before OLV
- Check ABG
- Add PEEP
- Adjust I:E for COPD pts
- Limit volatile gas to <1.5 to prevent HPV impairment
How does PEEP improve FRC in the OLV pt
It increases FRC by pushing the lung up the alveolar compliance curve
Is hypoxemia during OLV more common during surgery on the right or left lung?
Right lung
There is less are for gas exchange when the left lung is the only one ventilated
How do the DLT and bronchial blockers differ (5)
- BB cannot prevent contamination
- BB cannot ventilate isolated lung
- BB cannot suction
- BB can be used in peds <8 yo
- BB can be used with NT tubes
Advantages of using a BB over DLT
Don’t need to be reintubated
Can be used with NT tubes
Can be used in kids <8 y
Which lung is ventilated when using a bronchial blocker?
The lung on the opposite side of the BB
What are the uses of the lumen in the BB
- Insufflating O2 into non-ventilated lung
2. Suctioning air (NOT secretions) from non-ventilated lung
What are the 2 most common and serious complications of mediastinoscopy
Hemorrhage
PTX
What is an absolute contraindication to mediastinoscopy
Prior mediastinoscopy
Where should pulse oximetry and NIBP be placed when monitoring a patient having mediastinoscopy and why
Pulse ox = RUE
NIBP = LUE
pulse ox/a-line are on RUE. The waveform will dampen or disappear if the innominate artery is compressed during mediastinoscopy
What are indications for tracheal resection
Tracheal stenosis Tracheomalacia Tumor Vascular lesions Congenital malformation
A patient is 2 days s/p tracheal anastomosis and requires reintubation. What is the best technique and why
Use flexible fiberoptic bronchoscopy
Pts neck must maintain flexed position so extension for intubation is contraindicated
Complications of mediastinoscopy include injury to which structures
Thoracic aorta = hemorrhage and bradycardia
Innominate artery = decreased carotid BF, decreased CBF
Trachea = airway obstruction
Thoracic duct = chylothorax
Phrenic/RLN = paresis
What are 3 relative contraindications for mediastinoscopy
- Tracheal deviation
- Thoracic aortic aneurysm
- SVC obstruction
What patient history considerations must be assessed prior to an anesthetic for mediastinoscopy
- Type of lung CA. Eaton-Lambert syndrome means sensitivity to SUX and ND-NMBD
- CV disease
- History of stroke
During mediastinoscopy, what can result if the innominate artery is compressed?
Compromises right carotid and therefore cerebral blood flow
Importance of proper IV access in patients undergoing mediastinoscopy
Large bore LE access helps avoid loss of fluids or blood through vascular injury
You are pre-oping a patient for tracheal resection, what are important history and assessment considerations
- Are there airflow limitations
- Is there a CT to review
- Evaluate flow-volume loops
What type of induction would be appropriate for a patient undergoing tracheal resection and why
Awake intubation or inhaled induction
Obstruction during induction can occur.
Must preserve spontaneous ventilation to prevent obstruction
Which artery is at risk for compression during tracheal resection
Innominate (brachiocephalic) artery
What lung protective methods are taken in mechanically ventilating a patient with ARDS
- Low Vt
2. PEEP
What is the cause of ARDS
Inflammatory injury that leads to diffuse alveolar destruction
What are 4 key pathophysiologic features of ARDS
- Protein-rich pulmonary edema
- Loss of surfactant
- Hyaline membrane formation
- Possible long-term lung injury
Mechanical ventilator setting for a patient with ARDS Setting \_\_ Vt \_\_ PEEP \_\_ Plateau pressure \_\_ RR \_\_ I:E \_\_ O2 goal \_\_
Setting = pressure control Vt = 4-6 ml/kg ibw PEEP = titrate to keep FiO2<50% Plateau pressure <30 cmH2O RR = 6 - 35 bpm I:E = 1:1 - 1:3 O2 goal = PaO2 55-80 mmHg
What is ARDS
A form of non-cardiogenic pulmonary edema
What etiologies contribute to ARDS
Pulmonary causes:
PNA, COVID, aspiration, smoke inhalation injury, near-drowning
Extra-pulmonary causes:
SEPSIS, hematologic, trauma/shock, burns
What are the 3 stages of ARDS
Exudative = initial injury and inflammatory cascade
Proliferative = pathophysiologic process continues but body is trying to heal itself
Fibrotic = changes that cause irreversible damage to lung architecture and pulmonary HTN
How are PA pressures affected by cor pulmonale
They aren’t
PA pressures should be normal
Cor pulmonale is d/t pulmonary HTN not LV failure
A patient in the PACU exhibits signs of recurarization despite reversal with neostigmine and glycopyrrolate. What patient assessment can contribute to impaired reversal
Hypoventilation
Respiratory acidosis potentiates NMB and reduces efficacy of anticholinesterase worsening hypoventilation
Describe fluid management recommendations for patient undergoing pneumonectomy
Since pt is dependent on a single lung, it is best to limit crystalloid to replacement of volume deficit and maintenance requirement
Recommendations <3 L in 24 hours