Question help...

[cockblockandrun]

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Here were some questions that stumped me from the old ITEs on the ABA website. i put the answers from the key but would appreciate if someone would give an explanation to these qns. Thanks.

1. An endobronchial Robertshaw tube is inserted for resection of a midesophageal tumor under isoflurane, oxygen, pancuronium anesthesia. Forty minutes into a planned two-hour resection, ABG values are reported as PO2 45mmHg, PCO2= 45 mmHg, pH= 7.33. Ten minutes earlier the values were PO2= 210mm Hg, PCO= 41 mmHg and pH= 7.39. The first action should be to:
a. reposition the Robertshaw tube
b. apply PEEP to the ventilated lung
c. reinflate and ventilate the nonventilated lung
d. increase minute ventilation
e. repeat the ABG analysis

ANS: C


2. During total cardiopulmonary bypass, metabolic acidosis and decreasing mixed venous oxygen saturation are noted. The most likely cause is:
a. hypothermia
b. hypoperfusion
c. hypocarbia
d. rewarming
e. light anesthesia

ANS: B

 

[Idiopathic]

1. the first step would usually be to apply CPAP to the non-dependent lung (deflated lung), since that isnt an option, i assume you are wondering why it wouldnt be B, which is the only other reasonable option. i think this worsens the shunt in cases such as this where the hypoxemia is near-critical,(which is also another reason to ventilate the deflated lung, since the sats are probably about 75%)

2. seems completely reasonable, id like to hear why you dont think it could be B

 

[IlDestriero]

1. the first step would usually be to apply CPAP to the non-dependent lung (deflated lung), since that isnt an option, i assume you are wondering why it wouldnt be B, which is the only other reasonable option. i think this worsens the shunt in cases such as this where the hypoxemia is near-critical,(which is also another reason to ventilate the deflated lung, since the sats are probably about 75%)

2. seems completely reasonable, id like to hear why you dont think it could be B

Idio's on the money. Part of question 1 is likely recognizing that a PO2 of 45 is in the shiiter and needs some immediate attention.

 

[countingdays]

Here were some questions that stumped me from the old ITEs on the ABA website. i put the answers from the key but would appreciate if someone would give an explanation to these qns. Thanks.

1. An endobronchial Robertshaw tube is inserted for resection of a midesophageal tumor under isoflurane, oxygen, pancuronium anesthesia. Forty minutes into a planned two-hour resection, ABG values are reported as PO2 45mmHg, PCO2= 45 mmHg, pH= 7.33. Ten minutes earlier the values were PO2= 210mm Hg, PCO= 41 mmHg and pH= 7.39. The first action should be to:
a. reposition the Robertshaw tube
b. apply PEEP to the ventilated lung
c. reinflate and ventilate the nonventilated lung
d. increase minute ventilation
e. repeat the ABG analysis

ANS: C

C is correct. I think the point they are making with this question is that a PO2 of 45/ sat 80% is no joke. Don't play around with PEEP. Get the sat up now with two lung ventilation, then try the PEEP to stop it dropping so far when you go back on OLV.

There are also a lot of questions where the answer is to give Epi or start chest compressions. Not hesitating to bring out the big guns when needed seemed to be a recurrent theme when I did retired questions.

 

[Yo GabbaPentin]

2. During total cardiopulmonary bypass, metabolic acidosis and decreasing mixed venous oxygen saturation are noted. The most likely cause is:
a. hypothermia
b. hypoperfusion
c. hypocarbia
d. rewarming
e. light anesthesia

ANS: B

Regarding question #2, you can easily rule out several of the answers based on knowledge of metabolic acidosis with no knowledge whatsoever of SVO2. Hypothermia, hypocarbia, rewarming and light anesthesia will not cause a metabolic acidosis.

You can also figure this question out with a little knowledge about SVO2. To simplify, the main causes of SVO2 changes are Cardiac output, O2 consumption, Amount of Hb, Loading of hemoglobin and Saturation of hemoglobin (C.O.A.L.S.). Also seen in the equation:

SvO2 = SaO2 - (VO2/1.39 X Hb X C.O.)

A decrease in C.O. (aka hypoperfusion) will result in a lower SvO2. None of the other answers make sense. Tell the perfusionist to increase the damn flow.

 

[pgg]

C is correct. I think the point they are making with this question is that a PO2 of 45/ sat 80% is no joke. Don't play around with PEEP. Get the sat up now with two lung ventilation, then try the PEEP to stop it dropping so far when you go back on OLV.

This question or one just like it was on every single ITE I took, and my written exam.

Sat 70-80% during OLV? Reinflate the down lung. Futzing with PEEP/CPAP is not a crisis management drill.

There are also a lot of questions where the answer is to give Epi or start chest compressions. Not hesitating to bring out the big guns when needed seemed to be a recurrent theme when I did retired questions.

You're right, these are crisis recognition questions. Others that leap immediately to mind.

Don't be afraid to reheparinize and go back on CPB.

Epinephrine not neo or ephedrine or atropine or fluid for the high spinal with hypotension and bradycardia.

ACLS! Every single exam ...


Same thing with the oral exam. You don't want to let the examiners think your plan leans too far toward wait-hope-see conservative action.

 

[cockblockandrun]

Thanks everyone for the explanations.

CB