Residual Muscle Weakness after Succinylcholine Infusion: Clinical Presentation, Diagnosis and Treatment

Case Report

Austin J Anesthesia and Analgesia. 2014;2(4): 1022.

Residual Muscle Weakness after Succinylcholine Infusion: Clinical Presentation, Diagnosis and Treatment

Geng Li and Jingping Wang*

Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, USA

*Corresponding author: Jingping Wang, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.

Received: February 24, 2014; Accepted: April 04, 2014; Published: April 10, 2014


Here we report 2 cases of succinylcholine infusion for short surgical procedures, complicated by clinical presentation of upper airway obstruction in the immediate postoperative period, likely due to residual muscle weakness. In both cases, patients were extubated in OR. The presentation of residual muscle weakness in PACU was supported either with oxygen supplement via nasal cannula or with CPAP. No reintubation was needed. Lab work showed decreased pseudocholinesterase level in one of the patients. Literature review does not support an absolute number of total succinylcholine dosage or total administration time of succinylcholine infusion as a reliable predictor of progression into phase II block. Lab test of pseudocholinesterase function is not routinely performed. Therefore it is prudent to apply neuromuscular monitoring during succinylcholine infusion even when the surgery is considered a short procedure.

Keywords: Succinylcholine infusion; Pseudocholinesterase activity; Phase II neuromuscular block; Train-of-four nerve stimulation


Succinylcholine is the only depolarizing neuromuscular block agent that possesses the unique features of a rapid onset of effect and an ultra short duration of action. Continuous succinylcholine infusion is commonly used in most of laparoscopic cholecystectomy cases performed by a single surgeon at our institution. Administration of 1mg⁄kg of succinylcholine results in complete suppression of neuromuscular activity in approximately 60 seconds, and it takes 9-13 minutes to recover 90% muscle strength in patients with normal pseudocholinesterase activity (also known as plasma cholinesterase or butyrylcholinesterase) [1,2]. Here we present 2 cases of succinylcholine infusion with postoperative complaints consistent with prolonged residual muscle weakness.

Case Presentation

Case 1: 35yo ASAI female, without significant past medical history but mild asthma and allergy to augmentin, presented for umbilical hernia repair. She was 60 inches in height and 50kg in weight. She was induced with 150mcg Fentanyl, 100mg Propofol and 80mg Succinylcholine and intubated smoothly. 6 minutes after initial dose of Succinylcholine, Succinylcholine infusion was started at 100mcg⁄kg⁄min. The infusion was stopped at the end of surgery with total infusion time of 16min. The patient was able to follow commands and establish spontaneous breathing with RR 15-20⁄min and tidal volume reaching 300ml before extubation, which was about 7 minutes after succinylcholine infusion was stopped. She was sent to post–anesthetic recovery unit (PACU) where she soon complained of difficulty in swallowing. She has maintained normal SpO2 level through the course with no complaints of difficulty in breathing. Her symptoms resolved spontaneously and she was able to be discharged home directly from PACU the same day. Her pseudocholinesterase level was found to be within normal limits.

Case 2: 35yo ASAII male presented for ileostomy closure. He has past medical history significant for rhabdomyosarcoma of the psoas s⁄p radiation therapy and recent rectal cancer s⁄p low–anterior resection with diverting ileostomy. He was 69 inches in height and 60kg in weight. He was induced with 150mcg Fentanyl, 150mg Propofol and 100mg Succinylcholine and intubated smoothly. 12 minutes after intubation, Succinylcholine infusion was started at 100mcg⁄kg⁄min and was titrated up to 140mcg⁄kg⁄min till the end. 3 boluses of total 100mg succinylcholine were given intraoperatively to achieve adequate surgical muscle relaxation. The total Succinylcholine infusion time was 70min. His emergence was complicated by residual muscle weakness as shown by low tidal volume during pressure support ventilation. He adequately followed command and was extubated about 30min after succinylcholine infusion had stopped. He was observed in OR with SpO2 99–100% throughout. After he was brought to PACU, he complained of difficulty breathing although his SpO2 level never reached below 90%. CPAP was initiated and his symptoms resolved. No reintubation was needed. His pseudocholinesterase level was found to be low at 2485 with normal range of 3100–6500.


Residual muscle weakness in PACU unfortunately has remained common. Despite the efforts to limit the degree of residual paralysis with pharmacological reversal of non–depolarizing NMBDs, still up to 33–64% of patients manifest inadequate neuromuscular recovery on arrival to PACU [3,4]. In addition, factors that could contribute to prolonged neuromuscular blockade by succinylcholine [5,6] (Table 1) should not be overlooked. Situations such as pseudocholinesterase deficiency, succinylcholine–induced phase II block should be considered [7,8] (Table 2).