Flashcards in Monitors Deck (52)
What are the best places to measure core temperature?
Nasopharynx, tympanic membrane, distal portion of esophagus, or pulmonary artery (via PA catheter)
What is the body's natural core temperature and what range does it regulate itself?
37 C; it regulates within +/- 0.1 C
At what temperature does shivering occur?
A full degree Celsius lower than the vasoconstrictive threshold (which is 36.9 C)
What is true about shivering and the elderly?
They rarely shiver because of their reduced ability for thermoregulatory control
What is the first phase of intraoperative hypothermia?
Redistribution of heat from core to the periphery
What contributes most to the loss of heat in a patient during an operation?
Radiation (transfer of heat from one surface to another via photons - not dependent on temperature differences)
~60% of heat loss
If you have a transection at C7, which of the following would you expect if it has been 1 hour since the accident: risk of hyperkalemia with succinylcholine, risk of autonomic hyperreflexia with foley insertion, need for FOI, increased risk of hypothermia, all of the above
Increase risk of hypothermia below the level of the injury because they lack thermoregulation there
Hyperkalemia after 24 hours
Too fast for autonomic hyperreflexia
How does MAP and SBP differ in the aorta vs. radial artery?
Aorta will have a higher MAP and lower SBP; MAP decreases as pressure wave travels distally (slightly), SBP increases
What factors in an A-line setup can cause overdampening?
Increased length of tubing, decreased stiffness of tubing, multiple cockstops, clots, kinks, and air bubbles (all of which decrease the natural frequency of the system)
What is a good way to prevent an arterial artery thrombosis: propylene catheters, shorter catheter, Allen's test before, larger-gauged catheter, leaving the catheter in for a longer period of time
Larger-gauged (smaller) catheter
How do you adjust for blood pressure if the cuff is above the heart?
For every 1 cm above the heart, increase 0.7 mmHg
When should you be careful about using a PA catheter?
Patients with LBBB since PA catheters can cause RBBB -> complete heart block
What do you suspect if the SaO2 is 92% and the blood looks cherry red?
Carbon monoxide poisoning
Does the Bispectral index scale reduce the incidence of awareness under GA?
What is the neural path for SSEPs?
Peripheral nerve -> dorsal columns of the spinal cord -> sensory cortex
How does etomidate affect SSEPs?
Increases latencies and increases amplitudes
How does propofol affect SSEPs?
Increases latency and minimal effect on amplitudes
To prevent phase I hypothermia during GA, which is more effective: pre-warming the patient with forced air convection or infusing 1L of warmed saline?
Pre-warming the patient with forced air convection
How should you measure core temperature in a patient undergoing a CABG?
Tympanic membrane (esophageal temp is affected by ice in the thorax and pulmonary artery temp will have no flow while on pump)
What situations could you have a falsely low estimation of SpO2?
Severe TR, IABP, or high pressure ventilation (anything that can cause venous pulsations which get mistaken for arterial pulsation by the pulse ox)
How does ambient light affect pulse ox readings?
Falsely increases them
How would the ToF reading compare after non-depolarizing NMB in a patient who is paraplegic?
They have an exaggerated response compared to a normal person; possibly from an increase in extrajunctional ACh receptors and resistance to non-depolarizing NBM
What nerve stimulation pattern best estimates complete reversal of neuromuscular blockade?
Absence of fade on tetanic stimulation at 100 Hz for 5 seconds (66% effective)
What percentage of nicotinic receptors are occupied if a single twitch height is reduced?
What percentage of nicotinic receptors are occupied if the 4th twitch of a ToF is missing?
What do you see on capnography with an incompetent inspiratory valve? Expiratory valve?
Inspiratory: prolonged inspiration given the leak in the valve
Expiratory: Failure of expiration to return to 0 (rebreathing)
What is the normal gradient between PaCO2 and ETCO2 and why does it occur?
Alveolar dead space (ventilated but not perfused)
What would decreased pulmonary blood flow do to the gradient between PaCO2 and EtCO2? Increased CO?
1. Increases the gradient (more V/Q mismatch)
2. Decreases gradient (decreased alveolar dead space and thus V/Q mismatch)
What limbs does lead I display? Lead II? Lead III?
I: Left arm and right arm
II: Left arm and left leg
III: Right arm and left leg