Exam 2: Key Terms Flashcards
What is the potential benefit of inducing deliberate hypothermia during cardiopulmonary bypass?
Improves tissue tolerance of ischemia and protects against cerebral and cardiac ischemia
CNS injury may be higher with normothermic CPB
Why do patients lose heat under anesthesia?
Anesthesia lowers thermoregulatory threshold for shivering and causes vasodilation.
What is the physiologic response to heat loss in adults?
Shivering followed by vasoconstriction, moving the temperature gradient toward the core.
What effect does temperature have on MAC requirements?
Decreases MAC 5% for every 1*C lost
What are some physiologic consequences of hypothermia?
- Impaired immune function
- Decreased oxygen flow to tissue
- Increased incidence of arrhythmias
- Decreased drug metabolism
- Reduced platelet function and activation of clotting cascade (more blood loss)
- Marked increase in O2 consumption (shivering)
What is a potential benefit of monitoring temperature via the auditory meatus?
Theoretically reflects brain temperature because the auditory canal’s blood supply is the external carotid artery
What effect does hypothermia have on metabolic requirements?
For every 1°C below 37°C there is a 5 to 7% decrease in metabolic requirements (BMR & CMRO2)
To what temperature would you have to cool the patient in order for it to be neuroprotective?
< 35°C may be neuroprotective
How do we confirm placement of a double lumen tube?
With a flexible fiber-optic bronchoscope
When using a FFOB to look out of the Murphy Eye in a right-sided double lumen tube what should be seen?
“Mercedes sign”
What are some of the predictors of increased morbidity during thoracic procedures?
PPO < 40% **
Max VO2 <10 mL/kg/min **
Type of surgery (pneumonectomy = highest)
Post-op hemorrhage (20% mortality)
Regardless of the procedure the major anesthetic consideration for patients with esophageal disease is what?
Risk of pulmonary aspiration
How does the lateral decubitus position effect ventilation and perfusion?
Perfusion favors the dependent lung whereas ventilation favors the less perfused upper lung
What are some examples of thoracic procedures?
Lung resection Lung transplantation Pneumonectomy Tracheal resection LVRS Bronchoalveolar lavage Esophageal procedures Mediastinoscopy
According to our lecture notes, what are some absolute indications for one lung ventilation?
Contamination
Bronchoalveolar lavage
Necessary controlled distribution of ventilation
How can we achieve one lung ventilation?
Double lumen tube
Single lumen tube with bronchial blocker
Endobronchial intubation
What is the difference between resectability and operability?
Resectability is determined by the anatomic stage of the tumor
Operability is dependent upon the extent of the procedure and the physiological status of the patient
What factors can inhibit HPV?
Vasodilators Inhalational anesthetics PEEP Calcium channel blockers Hypocapnia High PVR Hypothermia
What are some of the ventilation goals for one lung ventilation?
Optimize oxygenation & ventilation!
6-8 mL/kg to ventilated lung Peak pressure <25 cmH2O Typically use PC \+/- PEEP to ventilated lung (auto peep=bad) \+/- CPAP to non-ventilated lung
What are the two special monitor placement requirements for a mediastinoscopy?
Right sided pulse ox
Left sided BP cuff
What is the most common site for cerebral aneurysms?
At the bifurcation of the large arteries at the base of the brain (Anterior circle of Willis)
What are the normal values for: CBF CMRO2 CSF volume CPP ICP
CBF = 50mL/100g/min (750mL/min) CMRO2 = 3.5mL/100g/min (50mL/min)
CSF volume = 150mL
CPP = 80-100 mmHg ICP = 5-10mmHg
How is intracranial hypertension defined and how does the body naturally compensate?
Sustained ICP > 15mmHg
Compensates by:
- Displacing CSF
- Increasing CSF absorption
- Decreasing CSF production
- Decreasing CBF
What are some risks associated with intracranial hypertension?
Herniation
Ischemia
Hypoxia
Cell death
