7 - muscle relaxants - onset and duration of action list

Muscle relaxants	Onset ( minutes )	Duration ( minutes )
Succinyl choline	1-1.5	3-6
Mivacurium	2-4	12-20
Rocuronium	1-2	25-40
Vecuronium	2-4	30-60
Atracurium	2-4	20-35
Cisatracurium	3-6	20-40
Piperacuronium	2-4	50-100
d-tubocurarine	4-6	30-60
Pancuronium	4-6	40-80
Doxacurium	4-8	60-120

So if the question is ?

Q: what is the shortest acting muscle relaxant ?

Answer : succinyl choline .

Q: what is the shortest acting non-depolarising muscle relaxant ?

Answer: mivacurium

Q: what is the longest acting muscle relaxant ?

Answer: doxacurium .

Q: what is the longest acting non-depolarising muscle relaxant ?

Answer: doxacurium .

TRY USING THIS MNEMONIC TO REMEMBER : Suck Me Rosy Victoria's Attractive Sister , Prepare To Please Doctors.

( in PREPARE = Two P s indicate piperacuronium and please indicates pancuronium )

6 - anaesthesia cases mcqs - 1

If malignant hyperthermia is
suspected intraoperatively

a. Complete the procedure but pretreat
with dantrolene prior to future
elective surgery
b. Administer inhalational anesthetic
agents
c. Administer succinylcholine
d. Hyperventilate with 100% oxygen
e. Acidify the urine to prevent myoglobin
precipitation in the renal
tubules

The answer is d. (Schwartz, 7/e, pp 448, 499.)

The cause of malignant
hyperthermia is unknown, but it is associated with inhalational anesthetic
agents and succinylcholine. It may develop in an otherwise healthy person
who has tolerated previous surgery without incident. It should be suspected
in the presence of a history of unexplained fever, muscle or connective
tissue disorder, or a positive family history (evidence suggests an
autosomal dominant inheritance pattern). In addition to fever during anesthesia,
the syndrome includes tachycardia, increased O2 consumption,
increased CO2 production, increased serum K+, myoglobinuria, and acidosis.
Rigidity rather than relaxation following succinylcholine injection may
be the first clue to its presence. Treatment of malignant hyperthermia
should include prompt conclusion of the operative procedure and cessation
of anesthesia, hyperventilation with 100% oxygen, and administration
of intravenous dantrolene. The urine should be alkalinized to protect the
kidneys from myoglobin precipitation. If reoperation is necessary, one
should premedicate heavily, alkalinize the urine, and avoid depolarizing
agents such as succinylcholine. Pretreatment for 24 h with dantrolene is
helpful; it is thought to act directly on muscle fiber to attenuate calcium
release.