test 9

Question 1

Thermoreceptors in the skin

Answer 1

 Causes hypothalamus to trigger sympathetic nervous
system response
 Vasoconstriction of the skin vessels which decreases loss of heat by convection (move it all to core)
 Vasodilation of skeletal muscle vascular beds (shiver)

Question 2

Endocrine

Answer 2

 Oxygen consumption increases
 HR Increases
 CO Increases
 BP Increases

Question 3

why use hypothermia

Answer 3

1. buys time in case you need to stop blood flow

2. safety mechanism if something fails

Question 4

why does hypothermia protect

Answer 4

 Reduces metabolic rate (enzyme rxn slowed)
 Reduces oxygen consumption
 Helps preserve high energy phosphate stores
 Reduces excitatory neurotransmitter release

Question 5

general affects of hypothermia

Answer 5

 Allows lower pump flows
 Better myocardial protection
 Less blood trauma
 Better organ protection

Question 6

mild hypothermia temp range

Answer 6

32-35°

Question 7

moderate hypothermia temp range

Answer 7

28-31°

Question 8

Deep Hypothermia temp range

Answer 8

18-27°

Question 9

Profound Hypothermia temp range

Answer 9

< 18°

Question 10

Alteration to Organ Function

Answer 10

 Decreased blood flow to all organs:
    Greatest: Skeletal Muscle / Extremities
    Kidneys
    Splanchnic Beds
    Heart
    Brain

Question 11

Heart function due to hypothermia

Answer 11

 Heart rate – Decreased
 Contractility – same or increased
 Dysrhythmias

Question 12

Lung function due to hypothermia

Answer 12

 Decrease in ventilation

 Gas exchange is unaffected

Question 13

tepid hypothermia

Answer 13

35-37°

Question 14

surgeries using mild hypothermia

Answer 14

• Aortic valve replacement

- most CABG

Question 15

surgeries using moderate hypothermia

Answer 15

• valve and a CABG
• Mitral valve
• Davinci
• ascending aortic annurysms

Question 16

surgeries from moderate down

Answer 16

-surgeries for kids

Question 17

Kidney function due to hypothermia

Answer 17

 Largest proportional decrease in blood flow
 Decrease in active transport
 Won’t reabsorb water
 Hemodilution and hypothermic bypass improves renal blood flow and protects renal tubules post operatively

Question 18

Liver function due to hypothermia

Answer 18

 Blood flow is reduced in proportion to the reduction in cardiac output
 ⬇ in metabolic and excretory function of the liver
 Drug actions / requirements

Question 19

Hyperglycemia

Answer 19

 Feature of hypothermic CPB
 Decreased insulin production (decrease metabolic function of pancreas)
 Give dextrose to increase glucose levels

Question 20

SVR increases

Answer 20

 Increase in viscocity
 Increase in catecholamines (Epi, NE)
 Hemoconcentration
 Cell Swelling
 Thoroughfare channel
 Further decrease in oxygen delivery to the tissues
 Thrombocytopenia

Question 21

Methods of Hypothermia

Induction

Answer 21

 Surface Cooling
 Core Cooling
 Deep Hypothermic Total Circulatory Arrest

Question 22

When to use Surface Cooling

Answer 22

 Small infants less than 2.5 to 3.0kg

 Myocardial protection on adults and peds

Question 23

when to use Profound hypothermia with arrest

Answer 23

 Repair complex congenital heart defects – small infants
and children
 Operations involving the aortic arch

Question 24

If arrest period longer than 60 minutes

Answer 24

 Use intermittent arrest with brief periods of hypothermic
flow
 Low-flow hypothermic perfusion is safer than total arrest

Question 25

Q10 Principle

Answer 25

 Q10 = relates the increase or decrease in reaction rates or metabolic processes to a temperature change of 10˚C.

Question 26

Reduction in Metabolic Rate

Answer 26

 reduced oxygen demand by 50% for every 7°C drop in temperature

Question 27

as pressure increases what happens to solubility of gas

Answer 27

increases

Question 28

as temperature increases what happens to the solubility of gases

Answer 28

decreases

Question 29

as temp increases, what happens to solubility and partial pressure

Answer 29

- Decreased solubility | - Increased partial pressure

Question 30

Rate of cooling

Answer 30

 Cool at 1°C per minute

Question 31

rate of warming

Answer 31

 Warm at 1°C per 3-5 minutes

Question 32

Consequences of Cooling / Warming too fast

Answer 32

 Development of temperature gradients within tissues  Body cooling after bypass  Exposure to hyperthermia

Question 33

Rate of Cooling / Warming Limitations

Answer 33

 Water temperature in heat exchanger  Blood pressure and systemic vascular resistance  Flow Rate

Question 34

Rewarming

Answer 34

-rewarm slowly so that the peripheral vascular beds open up  Use tools to help you rewarm (after AoXC removal)  Bair Hugger  Warming Blanket