Episode 176: Keywords Part 11: Barbiturates and Bier Blocks

Anesthesia and Critical Care Reviews and Commentary (ACCRAC) Podcast
Anesthesia and Critical Care Reviews and Commentary (ACCRAC) Podcast
Episode 176: Keywords Part 11: Barbiturates and Bier Blocks

In this 176th episode I welcome Dr. Gillian Isaac back to the show to discuss another 2 ABA key words. This time we discuss Barbiturates and Bier Blocks. I also take a moment up front to share some thoughts on the horrible tragedy of George Floyd’s death at the hands of the police and the importance of acknowledging white privilege and fighting for the fact that Black Lives Matter.

CME: https://earnc.me/ucUI9n

Reference: Clinical Anesthesia. Publication Year: 2017. Edition: 8th Ed. Authors/Editor: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; et al.
Outline by Brian Park, MD

Awakening after a single dose of thiopental is caused by redistribution from the brain primarily to which of the following sites?
(A) Fat
(B) Heart
(C) Liver
(D) Lung

Discussion (11:00)

Which of the following is associated with ↑ duration of clinical narcosis following infusion of total dose 10mg /kg thiopental over 3 hrs?
(A) alcoholism in remission
(B) asthma
(C) fever?
(D) obesity
(E) use of appetite suppressants

Discussion (12:11)

Compared with thiopental, methohexital is characterized by:
(A) better absorption after rectal administration
(B) greater protein binding
(C) greater hepatic clearance
(D) larger volume of distribution
(E) more complete biotransformation

Discussion (13:29)

The duration of action of an induction dose of thiopental is determined primarily by its
(A) rate of elimination
(B) rate of metabolism
(C) redistribution from brain to fat
(D) redistribution from brain to muscle
(E) hepatic extraction

Discussion (14:15)

Each of the following affects the induction dose of thiopental EXCEPT
(A) acute ethanol intoxication
(B) chronic use of barbiturates
(C) intravascular volume
(D) rate of hepatic extraction of thiopental
(E) serum albumin concentration

Discussion (14:40)

Which of the following statements about thiopental is true?
(A) Rapid uptake into maternal tissues limits its transfer to the fetus
(B) Its short duration of action is due to its extensive binding to plasma proteins
(C) Accumulation in fat leads to acute tolerance
(D) Alkalinity of solution causes respiratory depression
(E) Uptake into brain is slowed by respiratory acidosis

Discussion (16:22)

A healthy, but obese, 110-kg woman is scheduled for gastric stapling. Compared with that required at her ideal weight, the dose of thiopental required for anesthetic induction would likely be increased because of changes in?
(A) blood volume
(B) muscle mass
(C) circulation time
(D) body fat
(E) metabolic rate

Discussion (17:30)

Pain after 8ml inject of thiopental 2.5% through right radial catheter. Hand remains pink. Most appropriate next step?
(A) Inject lidocaine into catheter
(B) Inject nitroglycerin into catheter
(C) Inject papaverine into catheter
(D) R stellate ganglion block
(E) No intervention

Discussion (19:50)

Which of following barb-protection from cerebral ischemia is true?
(A) May be achieved w/ dose low enough to avoid cardiovascular effects
(B) Linear dose related
(C) Improve neuro outcome following card arrest
(D) Most useful for patients with focal ischemia
(E) Unrelated to EEG activity

Discussion (20:59)

Most likely to increase duration of seizure following ECT using barb and sux for GA?
a) admin atropine
b) change to benzodiazepine for induction
c) change to etomidate
d) add phenytoin to preop med (anti-seizure medication)
e) decrease barb used

Discussion (22:00)

CNS Effects (23:20)

Cardiovascular Effects (23:50)

Respiratory Effects (23:58)

Middle aged 70kg for elective craniotomy for brain tumor. Preop: alert, papilledema present. Induced w/ thiopental 300mg, sux 100mg → intubate → immediate bucking occurs. Best immediate mgt?
a) Admin sux 100mg iv
b) Fentanyl500mcg iv
c) Hyperventilate with isoflurane 2%
d) Admin thiopental 400mg IV
e) Hyperventilate + admin lido 1mg/kg

Discussion (24:22)

50M for emergent crani for evacuation of epidural hematoma. GCS 6. HR 54, BP 190/110. Most appropriate initial management?
a) atropine
b) mannitol
c) nimodipine
d) nitroprusside
e) thiopental

Discussion (27:21)

70kg 46M undergo clipping of cerebral aneurysm w/ N2O , opioid relaxant anesthesia. as surgeon about to enter dura, it’s noted to be tense and bulging. HR 100, MAP 90. PaO2 120, PaCO2 23, pH 7.5. What should be done immediately?
a) hyperventilate to PaCO2 15-20
b) admin furosemide 20mg IV
c) adim mannitol 0.5mg/kg
d) admin thiopental 250 increments
e) add halothane to deepen

Discussion (29:01)

During crani for supratentorial tumor, 28M receives N2O, O2, isoflurane. Vent controlled to maintain PACO2 25. Nasopharyngeal temperature 35.8. On opening dura, surgeon notes dura bulging . Most appropriate management ?
a) ↓ iso conc.
b) hyperventilate further
c) stop N2O
d) thiopental
e) muscle relaxant

Discussion (30:03)

Depression of cerebral O2 requirement below level required to create isoelectric EEG can be achieved by:
a) admin isoflurane
b) admin nimodipine
c) barb-coma
d) hyperventilate
e) hypothermia

Discussion (30:35)

Bier Blocks (32:04)

How to perform (34:00)

MOA (34:00)

Surgery cancelled after 10 min of IVRA with 50ml 0.5% lido. To terminate anesthesia safely, what is most appropriate timing for deflating tourniquet?
a) immediate after benzo admin
b) immediate after ephedrine
c) immediately, followed by inflation/deflation
d) in no less than 20 min after initial injection
e) in no less than 45 min after initial injection

Discussion (35:36)

Primary determinant of duration of IVRA?
a) tourniquet duration
b) capacitance of venous system of extremities
c) local anesthetic agent injected
d) volume of solution
e) method of exsanguinating

Discussion (37:06)

Which of following is true about bier block?
a) useful for postop pain
b) can be used for extremity surgery 2-3hr
c) bupivacaine is an alternative choice
d) lido most commonly used

Discussion (38:51)

All acceptable agents to use of bier block, except
a) 0.5% lido
b) 0.5% bupi
c) 0.25% bupi
d) 0.5% prilocaine

Discussion (39:37)

55kg man scheduled for hand surgery with IVRA w/ 0.5% lido 15 ml. Which of following is true?
a) contraindicated in sickle cell disease
b) mottling of skin after injection didcates abandonment of technique
c) tourniquet discomfort is indication to inject more local
d) bupivacaine0.5% can be substituted to prolong anesthesia
e) epi 1:400,000 should be added to prolong

Discussion (40:27)

Tourniquet with dual bladder used for IVRA for UE. At what point should distal tourniquet be inflated?
a) during injection of local anesthetic
b) after patient complains of tourniquet pain
c) co-inflation with proximal tourniquet
d) after proximal tourniquet deflated
e) prior to exsanguination

Discussion (42:21)

Which of following s/sx of lidocaine toxicity from high levels following IVRA?
a) shivering
b) nystagmus
c) lightheadedness, dizziness
d) tonic-clonic seizures

Discussion (43:11)

11 thoughts on “Episode 176: Keywords Part 11: Barbiturates and Bier Blocks”

  1. from a peds anesthesiologist’s perspective: Pentobarbital (trade name Nembutal) is also used for infants (<12 months old) and neonates (<1 month old) for MRI sedation. Pentobarb is useful for these tiny patients undergoing Brain MRI's, which usually take about 30-45 minutes of in-scanner time. PO (if non-contrast) dose 5-6mg/kg or IV (if +contrast) 4-5mg/kg; very minimal if any cardiovascular and respiratory side effects, especially useful for the extra fragile children w/ congenital cardiac conditions and/or syndromes. Usually pulse ox +/- nasal cannula +/- capnography is sufficient. Provides a very light plane of sedation- so often times these children do not tolerate NIBP + EKG monitoring. By the time the scan is done, they awaken and get on w/ their merry day with no residual side effects! Obviously must still adhere to NPO guidelines for any neonate being offered anesthesia services, regardless of the anticipated plane of sedation.

  2. Can you explain why you wouldn’t perform a stellate ganglion block with an intra-arterial injection of a barbiturate? Wouldn’t you want to do that before crystallization potentially occurred and thus prevent ischemia to the limb?

  3. For the question:

    Pain after 8ml inject of thiopental 2.5% through right radial catheter. Hand remains pink. Most appropriate next step?
    (A) Inject lidocaine into catheter
    (B) Inject nitroglycerin into catheter
    (C) Inject papaverine into catheter
    (D) R stellate ganglion block
    (E) No intervention

    Why wouldn’t you do the stellate ganglion block? I understand that the hand is pink right now, but couldn’t it be affected if the barbiturate causes toxicity to the artery.

    So why wouldn’t you prophylactically perform the block?

    1. I can’t tell you for sure why the answer is E so I’ll defer to anyone else who is more of an expert!

  4. To the tourniquet pain question — while I agree the answer is to deflate when the patient has pain, wouldn’t you want to deflate the proximal and inflate the distal? Because the distal has more anesthetic in it and is the “backup” tourniquet. My understanding was that the proximal remained inflated until the patient had pain and then the distal was the backup.

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