Misc. Monitoring Flashcards
Febrile temperature
> 38 C
Hypothermia
<36 C
Room temp
23 C
Recommended operating room temperature and why
68 to 75 F (20 to 24 C)
To inhibit bacteria growth)
Who may require warmer temperatures to prevent hypothermia?
Infants, children and burn patients
Temperature monitoring sites
- Blood (from a pulmonary artery catheter)
- Esophageal
- Rectal (less reliable if rectum is not clear)
- Nasal
- Bladder (less reliable if urine output is low)
- Skin/axillary
The best estimate of body temperature
Blood
The most consistently reliable measurement of body temperature
Esophageal
Etiologies of intraoperative temperature loss
- IV fluids (1 unit of blood or 1L of crystalloids can dec temp by 0.25 C)
- Vasodilation
- Blood products (except platelets)
- Volatile agents
Cardiac adverse effects of hypothermia
- Platelet dysfunction and bleeding
- Decreased stroke volumes
- Bradycardia and/or arrhythmias
- Increased blood viscosity
Neuro adverse effects of hypothermia
- Increased cerebral vascular resistance and decreased cerebral blood flow
- for every 1 C drop in temperature, cerebral blood flow decreases 5-7%
Renal adverse effects of hypothermia
- Decreased GFR and impaired tubular function
Respiratory adverse effects of hypothermia
- Respiratory depression
2. L shift of HbO2 dissociation curve
Metabolic adverse effects of hypothermia
- Decreased drug metabolism and delayed emergence from anesthesia
- Decreased wound healing
- Shivering
Shivering is more likely with:
- Lower intraoperative temperature
- longer surgeries
- higher concentrations of volatile agents
Why is shivering concerning?
It increases O2 consumption 5 fold, which is concerning for patients with CAD
Treatments for shivering
- Warm the patient
2. Demerol (25mg IV)
Types of heat loss in OR in order from most to least
- Radiation (60%)
- Evaporation (20%)
- Convection (15%)
- Conduction (5%)
Purpose of esophageal stethoscope
- Measure temperature
2. Listen to heart and lung sounds
Purpose of precordial stethoscope
- Valuable in transport
- Constant heart/lung sounds
- Popular in pediatrics
BIS reading for sedation
65-85
BIS reading for general anesthesia
40-65
BIS reading for too deep anesthesia
<40
Ketamine (increases/decreases) BIS number
Increases
Common situations for the BIS monitor
- Paralyzed patients
- Patients undergoing TIVA who are paralyzed
- Sick patients that require less anesthesia
When can you not monitor vital signs for awareness?
- When B blockers are given
2. When patients cannot mount a normal sympathetic response
Indicator of adequate cardiac output and renal perfusion
Urine output
Common goal for urine output
> 0.5 -1 ml/kg/hr
Ultrasound of cardiac structures, with the probe resting in the esophagus posterior to the heart
Transesophageal Echocardiography (TEE)
What can the TEE estimate?
- Ejection fraction
- Cardiac output
- Patency of heart valves (stenosis vs regurg)
- Pulmonary artery pressure
- The BEST monitor for diagnosing venous air embolism (VAE)
Purpose of evoked potentials
To monitor nerves that are close to the surgical site
Method of evoked potentials
- The nerve is electrically stimulated, which produces a waveform
- Ischemic or damaged nerves produce abnormal waves
Amplitude of evoked potentials
Height of the wave
Latency of evoked potentials
Time from the onset of the wave to the peak of the response
Effects of nerve damage and ischemia on evoked potentials
Decreased amplitude and increased latency
True/false: anesthetics increase amplitude and latency
False. Anesthetics DECREASE amplitude and increase latency
How can an anesthetist intervene if the evoked potential amplitude decreases and/or latency increases intraoperatively?
By increasing the patient’s blood pressure
Effects of propofol and volatile agents on evoked potentials
Decrease amplitude and increase latency
Volatile agents and nitrous oxide have the greatest effects on __evoked potentials
SSEPs
Effects of versed on evoked potentials
Decrease amplitude
No effect on latency
Effects of ketamine and etomidate on evoked potentials
Increases latency
Increases amplitude
Effects of nitrous oxide on evoked potentials
Decreases amplitude
No change on latency
Effects of opioids on evoked potentials
Minimal effect on evoked potentials
Types of evoked potentials
- Somatosensory evoked potentials (SSEPs)
- Motor evoked potentials (MEPs)
- Brainstem auditory evoked potentials (BAEPs)
- Visual evoked potentials (VEPs)
What is purpose of SSEPs?
To monitor the integrity of sensory nerves (dorsal nerve roots)
True/false: muscle relaxants do not affect the sensory pathways for SSEPs
True
Method of motor evoked potentials
Similar to SSEPs, but through the motor nerves instead
Anterior and lateral pathways of the spinal cord
True/false. SSEPs are more sensitive to volatile agents than MEPs
False, MEPs are more sensitive to volatile agents
True/false. Muscle relaxants should not be administered when MEPs are used
True
What does BAEPs measure?
The integrity of the vestibulocochlear nerve (VIII) and the brainstem
Which potentials are least affected by anesthetics?
BAEPs
Which potentials are most affected by anesthetics?
VEPs
What do VEPs measure?
The integrity of the optic nerve, can be used for pituitary tumor resection
Anesthetic management with evoked potentials
- <0.5 MAC volatile agent or use propofol drip or narcotic drip
- Keep anesthetic level as constant as possible
- Avoid muscle relaxants if MEPs are being used
When does propofol have less of an effect on evoked potentials?
Infusions have less of an effect than boluses