Anesthesia Lab II: Lecture 5 - Hypotension

Question 1

What is the 4-2-1 Rule for maintenance fluid requirement?

Answer 1

+ 4ml/kg/hr for the first 10kg
+ 2ml/kg/hr for the next 10kg
+ 1ml/kg/hr for each kg over 20kgs

Alternatively, take a patient’s weight in kg and add 40 to it if the patient is over 20kg.

Question 2

How much fluid loss is expected for minor surgery?

Answer 2

2-4 ml/kg/hr

Examples include robotic/laparoscopic surgery or hernia repair.

Question 3

What is the expected fluid loss for moderate surgery?

Answer 3

4-6 ml/kg/hr

Question 4

What is the expected fluid loss for major surgery?

Answer 4

6-10 ml/kg/hr

Includes procedures like open abdomen surgery, trauma, or bowel surgery.

Question 5

How is intra-operative blood loss replaced?

Answer 5

With either crystalloid or colloid at a 3:1 or 1:1 ratio.

Question 6

What are the components of fluid management in the 1st hour?

Answer 6

• Hourly maintenance
• 1/2 pre-operative deficit
• Insensible and surgical loss replacement

Question 7

What are the fluid management components for the 2nd and 3rd hours?

Answer 7

• Hourly maintenance
• 1/4 pre-operative deficit
• Insensible and surgical loss replacement

Question 8

What fluid management is required in additional hours?

Answer 8

• Hourly maintenance
• Insensible and surgical loss replacement

Question 9

Calculate the total fluid requirement for a 70kg patient NPO for 8 hours having a laparoscopic appendectomy.

Answer 9

770ml of LR or 0.9% NaCl

Calculation: 70 + 40 = 110; 110 x 8 = 880; 1st hour: 110 (hourly maintenance) + 440 (1/2 pre-op deficit) + 220 (insensible loss).

Question 10

What is the dilution for Phenylephrine?

Answer 10

10mg/ml in 100 ml 0.9% saline bag = 100mcg/ml

Double dilution: 1ml of 10mg/ml in 9ml of saline = 1mg/ml.

Question 11

What is the dosage range for Phenylephrine infusion?

Answer 11

10-50mcg/min

Question 12

What is the mechanism of action for Phenylephrine?

Answer 12

Alpha 1 agonism on vascular smooth muscle causing vasoconstriction and reflex bradycardia.

Question 13

What is the duration of action for Phenylephrine?

Answer 13

5-15 minutes

Question 14

What is the dilution for Ephedrine?

Answer 14

50mg/ml; 1ml in 9ml of 0.9% normal saline = 5mg/ml

Question 15

What is the mechanism of action for Ephedrine?

Answer 15

Indirect alpha 1 and beta 1 agonism due to tissue release of NE.

Question 16

What is the duration of action for Ephedrine?

Answer 16

Up to 1 hour, clinically 5-20 minutes

Question 17

What is the dilution for Vasopressin?

Answer 17

20U/ml in 19ml of saline = 1 unit/ml (bolus)
40 units in 100ml saline bag = 0.4units/ml (infusion)

Question 18

What is the dosage for Vasopressin?

Answer 18

1 unit bolus; 0.03-1 units/min

Question 19

What is the mechanism of action for Vasopressin?

Answer 19

Direct action on V1 receptors of vascular smooth muscle

Question 20

What is the duration of action for Vasopressin?

Answer 20

~20 minutes

Question 21

What is the dilution for Norepinephrine?

Answer 21

4mg/4ml in 250ml = 16mcg/ml

Question 22

What is the dosage for Norepinephrine?

Answer 22

5-15mcg/min

Question 23

What is the mechanism of action for Norepinephrine?

Answer 23

Direct action on alpha 1-2 and beta 1-2, highest for alpha 1

Question 24

What is the duration of action for Norepinephrine?

Answer 24

~5 minutes

Question 25

True or False: Hypovolemic hypotension is characterized by hypotension and tachycardia.

Answer 25

True

Question 26

What should be administered for hypotension if heart rate is greater than 60?

Answer 26

Ephedrine 5mg or Phenylephrine 100mcg

Question 27

What is the next step if hypotension is resolved?

Answer 27

Continue with 2nd hours deficit if foley catheter present and continue down vasodilated flowchart.

Question 28

What is the indication to reduce anesthetic during surgery?

Answer 28

If the surgeon has made an incision.