Mod1: Monitoring for Cardiac Surgery - RENAL FUNCTION - NEUROLOGIC OUTCOME Flashcards
INDICATIONS
Acute kidney injury (AKI) is a prevalent complication following bypass surgery. How often does it occur? What factor influences its occurence?
15-30%
Occurrence depends on complexity of procedure
INDICATIONS
What percentage of cardiac surgery pts suffer Dialysis dependent AKI? What’s it mortality rate?
2-5% of cardiac surgery patients
Dialysis dependent AKI carries mortality rate of 50%-80%
Associated with significant increase in hospital costs
INDICATIONS
Which three things is the renal failure resulting from impaired renal oxygenation that occurs during bypass is thought to be independently associated with?
Renal vasoconstriction
Hemodilution during cardiopulmonary bypass with cell-free solutions (e.g., crystalloids)
Non-physiologic state of nonpulsatile flow upsets renal blood flow autoregulation
INDICATIONS
T/F: Studies have shown that even with maintaining a mean perfusion pressure of 50 to 75, which has been shown to be adequate for maintaining systemic oxygen delivery, there is still a redistribution of blood away from the kidneys that occurs with bypass
True
INDICATIONS
T/F: During bypass, kidney function as well as kidney oxygen requirements are reduced?
False
Kidney function during bypass is maintained, as well as its oxygen requirements
INDICATIONS
During bypass, renal oxygen delivery is reduced by 20%. What’s responsible for this?
The combination of normal oxygen demand with reduced oxygen supply
INDICATIONS
What’s a negative outcome of the use of diuretics in CPB (e.g., mannitol)?
Hemolysis may occur
INDICATIONS
Why must U/O be maintained during CPB, especially when diuretics are used?
To avoid renal tubule damage
Removal of excess free water due to deliberate hemodilution induced with onset of CPB
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
Which neurologic complications occur following adult cardiac surgery?
Stroke 1-3%
Encephalopathy
Cognitive dysfunction
Etiology of these complications is complex, but multifactorial
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
T/F:
There is a statistically significant difference in occurence of neurologic complications between patients who have undergone on pump bypass vs off pump bypass surgeries
False
There is No statistically significant difference between patients who have undergone on on pump bypass vs off pump bypass surgeries
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
Which neurologic complication affect more patients than all other neurologic complications?
Cognitive dysfunction
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
T/F:
Cognitive dysfunction is more prevalent at 1 month vs at 6 months after surgery
True
30-65% patients affected at 1 month
20-40% patients affected at 6 months
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
What are possible causes of neurologic complications during CPB?
Cerebral emboli
Global cerebral hypoperfusion
Systemic inflammatory response
Genetic predisposition
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
Microemboli responsible for Cerebral emboli during CPB are of which two types?
Gasses or particulates
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
Where do Macroemboli responsible for Cerebral emboli during CPB originate?
Atheromatous
Calcific debris from the aorta
Cardiac valves
Great vessels
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
We’ve discussed the importance of cerebral protection during CPB, and the importance of cooling and rewarming during the various phases of bypass.
What are indications for CNS monitoring?
Known diagnosis of cerebral ischemia or one that develops during the course of the procedure
Assess depth of anesthesia which is very important during the rewarming phase (prevent intraoperative awareness)
Spinal cord protection (thoracic aneurysm repair)
To confirm adequate cooling/hypothermic arrest
- Pre-existing neurologic disease*
- Diagnosis of embolic phenomenon*
NEUROLOGIC OUTCOME FOLLOWING CARDIAC SURGERY
Which adverse neurologic outcome could come from inadequate arterial flow on CPB or Aortic cannula malposition during CPB?
Cerebral ischemia
ELECTROENCEPHALGRAM
What does the EEG reflects?
The EEG reflects metabolic activity of the brain
ELECTROENCEPHALGRAM
Why is the EEG rarely used during cardiac surgery to confirm the adequacy of cerebral oxygenation?
Because there are simpler methods for monitoring
ELECTROENCEPHALGRAM
What does the EEG records?
The electrical activity of cells in the cerebral cortex
ELECTROENCEPHALGRAM
Which EEG waves are often found in the resting adult with eyes closed?
Alpha waves
Frequency: 9-12Hz
Explanation: Medium frequency, higher amplitude, awake but eyes closed (EEG seen in occipital lobes)
ELECTROENCEPHALGRAM
Which EEG waves are found in concentrating adults, and sometimes in adults undergoing anesthesia?
Beta waves
Frequency: 13-30Hz
Explanation: High frequency, low amplitude, awake state
ELECTROENCEPHALGRAM
Which EEG waves are found with brain injury, deep sleep and anesthesia?
Delta waves
Frequency: 0-4Hz
Explanation: Very low frequency, depressed functions (coma, deep anesthesia, hypoxia, ischemia, infarction, poor metabolism)
ELECTROENCEPHALGRAM
Which EEG waves are found in sleeping individuals and those undergoing anesthesia?
Theta waves
Frequency: 4-8Hz
Explanation: Low frequency, seen under general anesthesia
ELECTROENCEPHALGRAM
What does slowing of electrical brain activity and decrease in signal amplitude on EEG indicate?
Cerebral ischemia
ELECTROENCEPHALGRAM
T/F: EEG requires experienced personel to interpret data
True
BIS MONITOR
What is BIS monitor indicated and used for?
Commonly used to indicate wakefulness
Used to measure the depth of anesthesia
More easily interpreted and utilized
BIS MONITOR
Why can’t BIS monitor be used to assess global ischemia?
Because the monitor is placed on the forehead
BIS MONITOR
T/F: BIS is a type of processed EEG
True
BIS MONITOR
In BIS power spectrum analysis how is EEG data processed?
By Fast Fourier Analysis …
into a single power versus time spectral array
Data reduced via proprietary method to a single number and scaled
BIS MONITOR
What does a BIS number of 100 indicate?
Alert/wakefulness
BIS MONITOR
What does a BIS number of 90-70 indicate?
Light to moderate sedation
BIS MONITOR
What does a BIS number of 70-60 indicate?
Deep sedation
Low probability of explecit recall
BIS MONITOR
What does a BIS number of 60-40 indicate?
General or adequate depth of Anesthesia
BIS MONITOR
What does a BIS number of 40-10 indicate?
Deep hypnotic state
BIS MONITOR
What does a BIS number of 10-0 indicate?
Flat line on the EEG
Electrical silence
EVOKED POTENTIALS
In which surgical cases do monittoring Somatosensory (SSEPs) & Motor evoked potentials (MEPs) become very important?
In cases where maintaining spinal cord blood flow is crucial
SSEPs and MEPs are used to monitor integrity of spinal cord during surgery of the descending aorta (thoracic aneurysm where blood flow to spinal cord may be compromised)
EVOKED POTENTIALS
Why do many of the thoracic aneurysm cases hold a very high incidence of paraplegia?
Incrased risk of hypoperfusion of the spinal cord following surgery
EVOKED POTENTIALS
How are Evoked Potentials measured?
A stimulus is applied to peripheral nerve while the brain activity is quantified
EVOKED POTENTIALS
What are the two different methods of assesing Evoked Potentials?
Visual evoked potentials
Brain stem audio evoked potentials
EVOKED POTENTIALS
T/F: Evoked Potentials Do not have routine clinical application in cardiac surgery
True
CEREBRAL OXIMETRY
Cerebral oximetry is increasingly used in the perioperative period of cardiac surgery. What technology does is use?
Infrared spectroscopy (NIRS)
It is a noninvasive technology that monitor the regional oxygen saturation of the frontal cortex
CEREBRAL OXIMETRY
What’s a benefit of the preoperative use of cerebral oximetry?
Can stratify patients preoperatively according to their risk
CEREBRAL OXIMETRY
What are benefits of using cerebral oximetry Intraoperatively?
Continuous information about brain oxygenation
Allows the use of the brain as an organ that indexes overall organ perfusion and injury
CEREBRAL OXIMETRY
What’s the similarity of cerebral oximetry with pulse ox?
Oxygenated and deoxygenated hemoglobin absorb light at different frequencies
CEREBRAL OXIMETRY
Unlike pulse oximetry, cerebral oximetry cannot identify pulsatile arterial components. Why not?
Because it reflects absorption of venous hemoglobin
CEREBRAL OXIMETRY
What are normal ranges of cerebral oximetry prior to anesthesia?
60-80%
Lower values of 50-60% have been seen
CEREBRAL OXIMETRY
What might regional saturation less than 40% or changes from baseline greater than 25% indicate
Neurological events secondary to decreased cerebral oxygenation
It’s important however to make sure that Pre-sedation values are captured to make accurate comparison with the post-sedation values
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
What does jugular bulb venous oximetry monitor?
Cerebral metabolic function
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
How does jugular bulb venous oximetry measure cerebral metabolic function?
Via fiberoptic catheter
Akin to measuring SVO2 via PA catheter
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
Why is jugular bulb venous oximetry not routinely used in cardiac surgery?
Because of it invasiveness, and
Less invasive monitors are available
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
What factors influence Cerebral O2 consumption?
Cerebral blood flow
O2 extraction from brain
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
How does Decreased cerebral blood flow affect jugular O2 saturation?
Decreased cerebral blood flow => Increases O2 extraction
=> Decrease jugular O2 saturation
CEREBRAL JUGULAR BULB VENOUS OXIMETRY
T/F: Trend monitoring yields more info than individual measurements
True
