








































Anesthesia eJournal
Volume 4 - Issue 1 2016

AEJ

Educated Hand Publishing LLC 
“The Science Behind the Art”  

 Anesthesia eJournal - Online
ISSN 2333-2611

Page 16

Postoperative Residual Curarization: A Case Report
Clay Freeman, CRNA, DNP

INTRODUCTION
A 67-year-old male was admitted with chronic hepatitis C and signs of cirrhosis. He presented with pitting edema 

scored as a plus one and mild jaundice. During an ultrasound screening and hepatic evaluation, a 1-cm mass on the 
liver was discovered. Initial clinical assessment and diagnostic imaging indicated suspicion for hepatocellular carcinoma 
with possible arterial and venous involvement. A laparoscopic ultrasound-guided biopsy and radiofrequency ablation 
of his liver lesion was planned after overnight observation. The procedure was planned to be converted to an open 
laparotomy if necessary intraoperatively.

In addition to chronic hepatitis C, the patient’s history was significant for hypertension, hyperlipidemia, and 
coronary artery disease. His overall body habitus was considered frail with a height of 175 cm, weight of 71 kg, and 
body mass index of 23. Home medications included lisinopril, aspirin, amlodipine, atenolol, and simvastatin. He denied 
any history of a stroke, but mild ataxia was present along with an unsteady gait related to hip dysfunction. He had 
used a walker for ambulation for the past several years and lived at home by himself. He displayed general weakness 
but stated that he was able to complete his activities of daily living without assistance. He had a prior history of heavy 
alcohol abuse for “many years” but denied current alcohol intake, with his last use approximately 5 years ago. He 
maintained a 20-pack-year smoking history. He denied any shortness of breath or difficulty breathing, although he 
stated that he did have a chronic cough. The patient’s lung sounds were clear to auscultation. His oxygen saturation was 
94% on room air in the preoperative holding area.

Past surgical history included an uneventful triple-vessel coronary artery bypass graft surgery in 2001 with no chest 
pain since that time and a laparoscopic cholecystectomy, which was also uneventful and free of anesthetic complication. 
Previous anesthesia records from these procedures were not available. The patient’s current liver function tests indicated 
hepatic damage as demonstrated by the following values: alanine aminotransferase (ALT), 100 U/L; aspartate 
aminotransferase (AST), 91 U/L; and partial thromboplastin time (pTT), 14.9 s. Laboratory values prior to surgery 
included the following: hemoglobin, 13.7 g/dL; hematocrit, 40.2%; platelets, 288,000; and international normalized 
ratio, 1.2. The patient had no known drug allergies.

Abstract
An elderly frail male patient with a history of liver disease presented for a laparoscopic ablation of a liver mass. 

Nondepolarizing neuromuscular blockade agents were used to maintain a train-of-four count of 1 to 2 twitches 
throughout the surgery. At the conclusion of the operation the patient’s neuromuscular blockade was assessed via train-
of-four at the corrugator supercilii, and the patient was given neuromuscular blockade reversal agents. Approximately 
10 minutes after his arrival to the recovery unit, the patient presented with symptoms suggestive of postoperative 
residual curarization. This case report demonstrates the importance of objective assessment strategies when evaluating 
neuromuscular blockade. Monitoring twitches at the adductor pollicis at the end of surgery gives the practitioner better 
evidence of a more complete neuromuscular blockade recovery. The dosing and timing of neuromuscular blockade reversal 
agents should be especially prudent to ensure adequate patient recovery and safety postoperatively.



Anesthesia eJournal                         www.anesthesiaejournal.com
Volume 4 - Issue 1 2016 Page 17

CASE SUMMARY 
The patient was brought into the operating room and assisted 

onto the operating table, standard monitors were applied, and 
preoxygenation with 100% oxygen was initiated. A standard 
induction sequence with intravenous (IV) fentanyl 100 mcg, 
lidocaine 100 mg, propofol 130 mg, and rocuronium 50 mg was 
performed through the patient’s existing 20-gauge peripheral 
IV line. Mask ventilation was easily accomplished with an oral 
airway in place. Intubation with a size 8.0 endotracheal tube was 
achieved with direct laryngoscopy grade 1 view. Sevoflurane was 
titrated to an end tidal concentration of 2.0%. A 16-gauge IV 
line was placed following induction and connected to a hot line 
with a fluid warmer. A peripheral nerve stimulator (PNS) was 
utilized to assess neuromuscular blockade (NMB) throughout the 
procedure. Vecuronium at a dose of 0.5 to 1 mg was administered 
approximately every 20 to 30 minutes upon recognition of a 
train-of-four (TOF) count at 2 or 3 with the goal to maintain 1 
to 2 twitches on TOF.

The surgical procedure was initiated and proceeded without 
incident. The patient’s vital signs remained stable throughout the 
procedure and ventilation was adequately achieved with a volume 
control mode, tidal volume of 500, rate of 12, 50% fraction of 
inspired oxygen (FiO2), and positive end expiratory pressure of 5 
cmH2O. A total of 11 mg of vecuronium, 7 mg of morphine, and 
200 mcg fentanyl were given during the 3-hour case, with the last 
dose of 1 mg vecuronium given 1.5 hours before surgical closure.

Upon closure of the 5 laparoscopic incisions, twitches were 
assessed at 2 twitches out of 4 at the corrugator supercilii muscle. 
A reversal of NMB, 2 mg neostigmine along with 0.4 mg 
glycopyrrolate, was administered. The patient began to initiate 
respirations and was taken off the ventilator. He was able to 
maintain adequate tidal volumes at this time. Morphine 2 mg was 
then slowly titrated intravenously to achieve a respiratory rate of 
10 to 12 breaths per minute. Sevoflurane was discontinued and 
shortly thereafter the patient was extubated awake after observing 
the patient was able to sustain a head lift of greater than 5 s 
upon command. The patient was then transported to the post-
anesthesia care unit (PACU) without oxygen. His vital signs upon 
arrival were as follows: blood pressure, 166/79 mmHg; heart rate, 
95 in sinus rhythm; 100% oxygen saturation; respiratory rate, 17; 
and temperature, 36.60C per external monitor. The patient was 
awake and following commands without signs of distress. He 
denied any pain or other complaints at the time of arrival to the 
PACU.

Approximately 10 minutes later, the nurse anesthetist, the 
resident nurse anesthetist, and an anesthesiologist were paged 
to the PACU to evaluate the patient. He appeared to be having 
difficulty breathing and swallowing, with overall anxiety. His 
blood pressure was 210/110 mmHg with tachycardia of 120 beats 
per minute. He was unable to verbalize but nodded appropriately 
when asked if he was short of breath. His breath sounds were 
diminished bilaterally on auscultation. His oxygen saturation 
remained greater than 92%. Respirations were then assisted 
at a rate of approximately 20 breaths per minute with a self-
inflating resuscitator and 100% FiO2. Labetalol 10 mg was given 
intravenously to decrease his blood pressure. An additional dose 
of NMB reversal, 2 mg neostigmine and 0.4 mg glycopyrrolate, 
was administered. After approximately 5 minutes of assisted 

ventilation, the patient demonstrated significant improvement in 
respirations. His vital signs returned to baseline and he was able 
to breathe effectively on his own. A 12-lead electrocardiogram 
and chest x-ray were ordered and the findings were unremarkable 
for acute events. The patient was later discharged to the 
intensive care unit, as planned preoperatively. Upon assessment 
the next day, the patient denied any concerns or complaints of 
anesthetic complications. The patient was discharged several 
days later without further incidents. He was seen in the clinic 1 
week later with no reports of significant events throughout his 
hospitalization.

REVIEW OF THE CURRENT EVIDENCE
Residual paralysis from NMB is a serious and underrecognized 

problem postoperatively. Historically, residual paralysis has been 
identified as postoperative residual curarization (PORC) since 
it was first noticed after the use of curare. The occurrence of 
PORC remains under-estimated among practitioners.1 Indeed, 
the decision to use reversal agents after NMB varies among 
international communities and even individual practitioners.1 
Much of the debate is likely due to the high degree of variability 
in monitoring for the degree of NMB. A number of ways 
exist to measure NMB but none are more prevalent than the 
PNS.1,2 However, the use of the PNS intraoperatively has not 
demonstrated a decreased incidence of PORC when compared 
with more subjective measures such as a patient-sustained head 
lift.2-4

Important in the use of the PNS is how it is utilized and how 
the results are interpreted by the provider. The different sites used 
for TOF monitoring produce variable results.5-9 The corrugator 
supercilii muscle and adductor pollicis muscle are 2 frequently 
monitored sites. The corrugator supercilii muscle demonstrates 
a recovery time comparable with that of the diaphragm.5,7,8 The 
adductor pollicis has a more delayed recovery time than that of 
the corrugator supercilii muscle.2,5,6 The adductor pollicis is in 
fact one of the muscles that is part of the last group of muscles to 
recover from NMB.5,7

Interpretation of TOF is also a crucial aspect in evaluating the 
degree of neuromuscular recovery. A TOF ratio of at least 0.7 was 
previously believed to be an acceptable criterion for determining 
patient readiness for extubation.1,2,4,6 However, several studies 
have evaluated whether this criterion is satisfactory enough to 
avoid adverse events in the postoperative recovery period. Further 
evaluation has demonstrated a TOF value of 0.9 or greater to 
be preferable to lessen the likelihood of respiratory compromise 
in patients who received NMB.3-6 This is best appreciated in the 
demonstration that even healthy volunteers complain of some 
difficulty breathing with a TOF ratio of 0.7 and even up to 0.9.3-

5,7,8 Although the diaphragm is functional at a TOF of 0.7, some 
of the upper airway and esophageal muscles remain weak.3-5,10 
Such aspects predispose the patient to increased risk of aspiration, 
airway obstruction, atelectasis, pneumonia, and hypoxia.3,7 
Complicating matters when determining adequate reversal is the 
realization that many of the subjective measures still demonstrate 
some degree of NMB.2 Subjective criteria such as a sustained 
head lift, purposeful hand grip, and adequate patient tidal 
volumes can still be present with a TOF ratio of 0.5.4-6,8

The use of NMB antagonism also remains debated owing to 



mixed understandings of neuromuscular blocking agents and 
NMB antagonists. The occurrence of PORC has been assumed 
to have decreased in part due to the addition of intermediate-
acting paralytics such as rocuronium and cisatricurium.11,12 Upon 
experimentation, however, studies have not revealed this to be 
true.4,5 Differences in incidences of PORC are seen only when 
long-acting paralytics such as pancuronium are compared with 
paralytics like vecuronium, which is intermediate-acting.11,12 
Evidence suggests that practitioners are also underestimating 
the time necessary for full recovery after a single dose of an 
intermediate-acting agent.1,5,12 Residual muscle weakness of 
clinical significance may continue for more than 2 hours.1,3,5 

Understanding recovery time is especially prudent when 
considering the sometimes unpredictable nature of steroid-based 
neuromuscular blocking agents.1,5

Reversal agents exert their effects by increasing acetylcholine 
at the neuromuscular junction and inhibiting cholinesterase, 
thereby indirectly competing with neuromuscular blocking agents. 
Reversal agents are most effective when given at 2 twitches or 
greater.3,4,12 Giving neostigmine before the patient has 2 twitches 
can result in delayed recovery and incidence of PORC.3,4,12

DISCUSSION
How to best reverse the neuromuscular blocked patient is 

clearly a subjective decision at this time.1,7,8 The NMB in the 
present case report was monitored, maintained, and reversed 
according to typical practices by anesthesia providers. The 
criteria used to determine readiness for extubation are also 
considered typical within the anesthesia community.1,7,8 Our 
patient demonstrated what appeared to be an adequate count 
of twitches on TOF prior to administration of the reversal 
agent. Afterward, a TOF count of 4 twitches was achieved and 
the patient was extubated awake after a sustained head lift was 
confirmed. Spontaneous ventilation tidal volumes were around 
5 mL/kg. However, the patient presented evidence of PORC 
in the PACU. Assessment of patient vital signs, respiratory rate, 
and pupillary size decreased suspicion of respiratory compromise 
due to opioids or benzodiazepines. Although visual assessments 
are not conclusive, differential diagnoses were quickly reduced 
to likely PORC. The identification of PORC was reinforced 
by patient improvement 5 minutes after administration of a 
repeat dose of neostigmine. The patient’s improvement in motor 
function correlated with the onset time of the reversal effects of 
neostigmine. The patient again showed clinical signs of adequate 
recovery (sustained head lift to command, adequate tidal volumes, 
ability to cough) and was extubated.

Considering what appeared to be a typical anesthetic case 
utilizing NMB, reflection on this case discloses the limitations 
in current practices. More specific and detailed assessment may 
have prevented this scenario of PORC. The site of monitoring 
for twitches can demonstrate a noticeable difference in measured 
outcomes. This patient’s twitches were examined at the corrugator 
supercilii muscle. A more appropriate evaluation should be 
made by moving the PNS to the ulnar nerve and monitoring the 
adductor pollicis muscle at the conclusion of surgery, because 
the adductor pollicis is one of the last muscle groups to recover 
from NMB. Monitoring at sites that recover more quickly puts 
the patient at greater risk for PORC. The patient may still be 

compromised in respiratory function even when he or she can 
sustain a head lift of greater than 5 s.4,7,8 It is also preferable 
if a patient’s motor function has spontaneously returned with 
greater than 2 twitches on TOF count before a NMB antagonist 
is administered. Additionally, dosing NMB antagonism on 
the basis of the degree of neuromuscular recovery is of critical 
importance to avoid PORC. Upon recovery of 2 TOF twitches, 
an ideal dose of neostigmine is 0.05 mg/kg.4,5 With these doses 
in mind, the patient in this case was optimally antagonized only 
after his second administration of neostigmine in the PACU. All 
these measures are especially pertinent in high-risk patients. The 
patients who are likely to recover neuromuscular function more 
slowly than anticipated are the elderly, the obese, and those with 
kidney or liver malfunction.1,12 With respect to the patient’s age, 
history, and the procedure being performed, a high degree of 
awareness for possible PORC should be suspected.

Much can also be gained in the understanding of residual 
NMB across the entire anesthesia practice from studying 
scenarios such as these and what the literature suggests. The 
American Association of Nurse Anesthetists standard V states, 
“When neuromuscular blocking agents are administered, monitor 
neuromuscular response to assess depth of blockade and degree 
of recovery.”7 While the literature does not suggest an increased 
incidence of PORC whether neuromuscular monitoring is used 
or not,4,5 standards set forth by professional organizations are 
encouraged. Clearly more teaching and discussion are needed 
across the entire anesthesia practice to decrease the disparity 
among practitioners. Such disparities include appropriate 
neuromuscular monitoring, the interpretation of monitoring 
results, length of time until spontaneous NMB recovery, and 
timing of reversal agents. Understanding these facets is vital to 
improving patient care and increasing the quality of anesthesia 
care. PORC is a true risk for post-anesthetic patients that can 
result in delayed recovery, increased morbidity, and increased risks 
of aspiration and other adverse respiratory events. These risks 
should demonstrate to anesthesia practitioners that appropriate 
care of patients is also about ensuring appropriate postoperative 
recovery. 

Anesthesia eJournal                         www.anesthesiaejournal.com
Volume 4 - Issue 1 2016 Page 18



Anesthesia eJournal                         www.anesthesiaejournal.com
Volume 4 - Issue 1 2016 Page 19

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