BT_GS 1.56 - Inadequate reversal

Question 1

PORC
Definition

Answer 1

the presence of T4/T1 ratio <0.9 ratio

Question 2

PORC
Influencing factors

Answer 2

Age
Increased incidence in older patients

Gender
Increased incidence in females

Weight
Increased incidence with higher body weight and BMI (body mass index)

Comorbidities
Increased incidence in patients with sleep apnea, neuromuscular disorders, renal or liver dysfunction, and cardiovascular disease

Drug related factors
Medications that affect neuromuscular transmission (eg, anti-seizure medications) Just say they’re higher risk if there is concurrent use of medication that prolongs or potentiates NMB

Anaesthesia-related factors
Duration of anesthesia, type and dose of NMB agent administered, number of muscle relaxants (1 vs. 2 or more), and depth of NMB maintained

Question 3

PORC signs and symptoms

Answer 3

Visual disturbance
Difficulty swallowing
Difficulty speaking or drinking
Generalised muscle weakness

Question 4

PORC clinical consequences

Answer 4

Reintubation in the PACU
Critical respiratory events, including respiratory failure and severe hypoxaemia
Pulmonary complications, including pneumonia
Impairment of upper esophageal and pharyngeal muscles

Question 5

PORC Subjective monitoring techniques

Answer 5

sustained eye opening,
arm lift to the opposite shoulder,
sustained leg lift for 5 seconds,
Sustained head lift for 5 seconds.
Only 50% accurate
can occur at a TOF ratio of 0.7

Question 6

Recovery from blockade occurs when

Answer 6

when the concentration of the NMB is reduced relative to Ach
Two methods of reversal
Increased Ach - AChE inhibitors
Reduced NMB - sugammadex

Question 6

PK reason for PORC

Answer 6

The patient should be closely monitored in the recovery room, since the half-life of the reversal drug might be shorter than that of the muscle relaxant, causing recurarization. E.g. endorphonium used to reverse pancuronium

Question 7

What is the difference between duration of action and offset time

Answer 7

Duration of action is the time for spontaneous recovery of 25% of the baseline twitch height following a standard intubating dose
Offset time is the time taken for spontaneous recovery from 25% twitch height (TOF 3) to 75% twitch height (TOFR 40%)

Question 8

Pulmonary function (RR, TV FEV, FVC) is usually recovered once the TOFR is > ??

Answer 8

TOFR is > 0.6 at the adductor pollicis muscle
However lesser degrees of NMB can adversely affect respiratory function, airway patency, and airway protective reflexes (cough and swallow)

Question 9

Role of genioglossus and its significance in TOF monitoring

Answer 9

Dilates against negative pressures generated
Impaired markedly at even 0.8 TOFR (slight block)
Increased airway collapsibility and reduced air flow
FIV reduced, but FEV maintained with partial paralysis
Impaired swallow - increased risk aspiof ration
Also, impaired upper oesophageal sphincter tone
Susceptibility of upper airway muscles
Not explained by AChR density
Possibly due to high firing rate of neurons at NMJ - 15-25 Hz and hence possibly greater fade than the 2 Hz TOF

Question 10

PORC features at
Slight block (0.8-0.9 TOFR)

Answer 10

Impairs AHVR and increases the risk of upper airway collapse
Reduced upper airway closing pressure
Reduced upper airway dilator muscle function
Reduced airway volume during inspiration
Impaired swallow
TV, VC, lung volumes are typically normal
Residual upper airway block can thus often go undetected

Question 11

PORC features at
Moderate block (0.5 TOFR)

Answer 11

Impaired swallow
Impaired upper airway patency
Reduced AHVR
Often reduced FVC but normal TV