Jeffery S. Vender

Residual neuromuscular blockade and critical respiratory events in the postanesthesia care unit

BACKGROUND: Incomplete recovery of neuromuscular function may impair pulmonary and upper airway function and contribute to adverse respiratory events in the postanesthesia care unit (PACU). The aim of this investigation was to assess and quantify the severity of neuromuscular blockade in patients with signs or symptoms of critical respiratory events (CREs) in the PACU. METHODS: We collected data over a 1-yr period. PACU nurses identified patients with evidence of a predefined CRE during the first 15 min of PACU admission. Train-of-four (TOF) ratios were immediately quantified in these patients using acceleromyography (cases). TOF data were also collected in a control group that consisted of patients undergoing a general anesthetic during the same period who were matched with the cases by age, sex, and surgical procedure. RESULTS: A total of 7459 patients received a general anesthetic during the 1-yr period, of whom 61 developed a CRE. Forty-two of these cases were matched with controls and constituted the study group for statistical analysis. The most common CREs among matched cases were severe hypoxemia (22 of 42 patients; 52.4%) and upper airway obstruction (15 of 42 patients; 35.7%). There were no significant differences between the cases and matched controls in any measured preoperative or intraoperative variables. Mean (±sd) TOF ratios were 0.62 (±0.20) in the cases, with 73.8% of the cases having TOF ratios <0.70. In contrast, TOF values in the controls were 0.98 (±0.07) (a difference of −0.36 with a 95% confidence interval of −0.43 to −0.30, P < 0.0001), and no control patients were observed to have TOF values <0.70 (the 95% confidence interval of the difference was 59%–85%, P < 0.0001). CONCLUSIONS: A high incidence of severe residual blockade was observed in patients with CREs, which was absent in control patients without CREs. These findings suggest that incomplete neuromuscular recovery is an important contributing factor in the development of adverse respiratory events in the PACU.

Cerebral Oxygen Desaturation Events Assessed by Near-infrared Spectroscopy During Shoulder Arthroscopy in the Beach Chair and Lateral Decubitus Positions

BACKGROUND: Patients undergoing shoulder surgery in the beach chair position (BCP) may be at risk for adverse neurologic events due to cerebral ischemia. In this investigation, we sought to determine the incidence of cerebral desaturation events (CDEs) during shoulder arthroscopy in the BCP or lateral decubitus position (LDP). METHODS: Data were collected on 124 patients undergoing elective shoulder arthroscopy in the BCP (61 subjects) or LDP (63 subjects). Anesthetic management was standardized in all patients. Regional cerebral tissue oxygen saturation (SctO2) was quantified using near-infrared spectroscopy. Baseline heart rate, mean arterial blood pressure, arterial oxygen saturation, and SctO2 were measured before patient positioning and then every 3 minutes for the duration of the surgical procedure. SctO2 values below a critical threshold (≥20% decrease from baseline or absolute value ⩽55% for >15 seconds) were defined as a CDE and treated using a predetermined protocol. The number of CDEs and types of intervention used to treat low SctO2 values were recorded. The association between intraoperative CDEs and impaired postoperative recovery was also assessed. RESULTS: Anesthetic management was similar in the BCP and LDP groups, with the exception of more interscalene blocks in the LDP group. Intraoperative hemodynamic variables did not differ between groups. SctO2 values were lower in the BCP group throughout the intraoperative period (P < 0.0001). The incidence of CDEs was higher in the BCP group (80.3% vs 0% LDP group), as was the median number of CDEs per subject (4, range 0–38 vs 0, range 0–0 LDP group, all P < 0.0001). Among all study patients without interscalene blocks, a higher incidence of nausea (50.0% vs 6.7%, P = 0.0001) and vomiting (27.3% vs 3.3%, P = 0.011) was observed in subjects with intraoperative CDEs compared with subjects without CDEs. CONCLUSIONS: Shoulder surgery in the BCP is associated with significant reductions in cerebral oxygenation compared with values obtained in the LDP.

Intraoperative acceleromyographic monitoring reduces the risk of residual neuromuscular blockade and adverse respiratory events in the postanesthesia care unit.

Background:Incomplete recovery from neuromuscular blockade in the postanesthesia care unit (PACU) may contribute to adverse postoperative respiratory events. This study determined the incidence and degree of residual neuromuscular blockade in patients randomized to conventional qualitative train-of-four (TOF) monitoring or quantitative acceleromyographic monitoring. The incidence of adverse respiratory events in the PACU was also evaluated. Methods:One hundred eighty-five patients were randomized to intraoperative acceleromyographic monitoring (acceleromyography group) or qualitative TOF monitoring (TOF group). Anesthetic management was standardized. TOF patients were extubated when standard criteria were met and no fade was observed during TOF stimulation. Acceleromyography patients had a TOF ratio of greater than 0.80 as an additional extubation criterion. Upon arrival in the PACU, TOF ratios of both groups were measured with acceleromyography. Adverse respiratory events during transport to the PACU and during the first 30 min of PACU admission were also recorded. Results:A lower frequency of residual neuromuscular blockade in the PACU (TOF ratio ≤ 0.9) was observed in the acceleromyography group (4.5%) compared with the conventional TOF group (30.0%; P < 0.0001). During transport to the PACU, fewer acceleromyography patients developed arterial oxygen saturation values, measured by pulse oximetry, of less than 90% (0%) or airway obstruction (0%) compared with TOF patients (21.1% and 11.1%, respectively; P < 0.002). The incidence, severity, and duration of hypoxemic events during the first 30 min of PACU admission were less in the acceleromyography group (all P < 0.0001). Conclusions:Incomplete neuromuscular recovery can be minimized with acceleromyographic monitoring. The risk of adverse respiratory events during early recovery from anesthesia can be reduced by intraoperative acceleromyography use.

Comparison of the Infusion Requirements and Recovery Profiles of Vecuronium and Cisatracurium 51W89 in Intensive Care Unit Patients

The selection and administration of neuromuscular blocking (NMB) drugs in intensive care unit (ICU) patients remain controversial.We compared the dose-response and recovery pharmacodynamics of a new intermediate-acting NMB drug, cisatracurium besylate, to the intermediate-acting NMB drug, vecuronium (VEC), in a prospective, randomized, double-blind, multicenter study in critically ill adults. After informed consent, 58 mechanically ventilated ICU patients from five medical centers were randomized to receive either cisatracurium or VEC. Fifty-four of the 58 patients received NMB drugs before entering this study but demonstrated at least partial recovery (>or=to one twitch) in the train-of-four (TOF) response before initiation of the NMB study drug. NMB drug infusion was titrated by peripheral nerve stimulation to maintain at least one twitch in the TOF response. NMB drugs were infused for 1-5 days. After discontinuation of NMB drug infusion, recovery of neuromuscular transmission was monitored with an accelerometer. NMB drug infusion for 28 cisatracurium patients averaged 2.6 +/- 0.2 (mean +/- SEM) micro gram centered dot kg-1 centered dot min-1 with a mean duration of 80 +/- 7 h. After discontinuing cisatracurium administration, recovery to 70% TOF ratio averaged 68 +/- 13 min. The mean infusion rate for 30 VEC patients was 0.9 +/- 0.1 micro gram centered dot kg-1 centered dot min-1 with a mean duration of 66 +/- 12 h. Neuromuscular recovery after VEC averaged 387 +/- 163 min, which was significantly longer (P = 0.02) than that after cisatracurium. Prolonged recovery of neuromuscular function after discontinuation of NMB drug infusion (identified by the primary investigator at each medical center) was reported in two cisatracurium patients and 13 VEC patients (P = 0.002), and occurred despite the routine use of neuromuscular twitch monitoring. Seven VEC and one cisatracurium patients died during the infusion of study drug or within 48 h after discontinuation of the NMB drug infusion. In summary, we found recovery of neuromuscular function after discontinuation of NMB drug infusion in ICU patients is significantly faster with cisatracurium than with VEC. In addition, routine neuromuscular monitoring was not sufficient to eliminate prolonged recovery and myopathy in ICU patients. (Anesth Analg 1995;81:3-12)

Residual paralysis at the time of tracheal extubation

Respiratory and pharyngeal muscle function are impaired during minimal neuromuscular blockade. Tracheal extubation in the presence of residual paresis may contribute to adverse respiratory events. In this investigation, we assessed the incidence and severity of residual neuromuscular block at the time of tracheal extubation. One-hundred-twenty patients presenting for gynecologic or general surgical procedures were enrolled. Neuromuscular blockade was maintained with rocuronium (visual train-of-four [TOF] count of 2) and all subjects were reversed with neostigmine at a TOF count of 2–4. TOF ratios were quantified using acceleromyography immediately before tracheal extubation, after clinicians had determined that complete neuromuscular recovery had occurred using standard clinical criteria (5-s head lift or hand grip, eye opening on command, acceptable negative inspiratory force or vital capacity breath values) and peripheral nerve stimulation (no evidence of fade with TOF or tetanic stimulation). TOF ratios were measured again on arrival to the postanesthesia care unit. Immediately before tracheal extubation, the mean TOF ratio was 0.67 ± 0.2; among the 120 patients, 70 (58%) had a TOF ratio <0.7 and 105 (88%) had a TOF ratio <0.9. Significantly fewer patients had TOF ratios <0.7 (9 subjects, 8%) and <0.9 (38 subjects, 32%) in the postanesthesia care unit compared with the operating room (P < 0.001). Our results suggest that complete recovery from neuromuscular blockade is rarely present at the time of tracheal extubation.

Intraoperative acceleromyography monitoring reduces symptoms of muscle weakness and improves quality of recovery in the early postoperative period

Background: The subjective experience of residual neuromuscular blockade after emergence from anesthesia has not been examined systematically during postanesthesia care unit (PACU) stays. The authors hypothesized that acceleromyography monitoring would diminish unpleasant symptoms of residual paresis during recovery from anesthesia by reducing the percentage of patients with train-of-four ratios less than 0.9. Methods: One hundred fifty-five patients were randomized to receive intraoperative acceleromyography monitoring (acceleromyography group) or conventional qualitative train-of-four monitoring (control group). Neuromuscular management was standardized, and extubation was performed when defined criteria were achieved. Immediately upon a patients arrival to the PACU, the patients train-of-four ratios were measured using acceleromyography, and a standardized examination was used to assess 16 symptoms and 11 signs of residual paresis. This examination was repeated 20, 40, and 60 min after PACU admission. Results: The incidence of residual blockade (train-of-four ratios less than 0.9) was reduced in the acceleromyography group (14.5% vs. 50.0% control group, with the 99% confidence interval for this 35.5% difference being 16.4–52.6%, P < 0.0001). Generalized linear models revealed the acceleromyography group had less overall weakness (graded on a 0–10 scale) and fewer symptoms of muscle weakness across all time points (P < 0.0001 for both analyses), but the number of signs of muscle weakness was small from the time of arrival in the PACU and did not differ between the groups at any time. Conclusion: Acceleromyography monitoring reduces the incidence of residual blockade and associated unpleasant symptoms of muscle weakness in the PACU and improves the overall quality of recovery.

Preoperative Dexamethasone Enhances Quality of Recovery after Laparoscopic Cholecystectomy Effect on In-hospital and Postdischarge Recovery Outcomes

Background:The effect of dexamethasone on quality of recovery after discharge from the hospital after laparoscopic surgery has not been examined rigorously in previous investigations. We hypothesized that preoperative dexamethasone would enhance patient-perceived quality of recovery on postoperative day 1 in subjects undergoing laparoscopic cholecystectomy. Methods:One hundred twenty patients undergoing outpatient laparoscopic cholecystectomy were randomized to receive either dexamethasone (8 mg) or placebo-saline. A 40-item quality-of-recovery scoring system (QoR-40) was administered preoperatively and on postoperative day 1 to all subjects. Nausea, vomiting, fatigue, and pain scores were recorded at the time of discharge from the postanesthesia care unit and ambulatory surgical unit. Hospital length of stay was also assessed. Results:Global QoR-40 scores on postoperative day 1 were higher in the dexamethasone group (median [range], 178 [130–195]) compared with the control group (161 [113–194]) (median difference [99% CI], −18 [−26 to −8]; P < 0.0001). Postoperative QoR-40 scores in the dimensions of emotional state, physical comfort, and pain were all improved in the dexamethasone group compared with the control group (P < 0.001). Nausea, fatigue, and pain scores were all reduced in the dexamethasone group during the hospitalization, as were postoperative analgesic requirements (P < 0.05). Total hospital length of stay was also reduced in subjects administered steroids (P = 0.003). Conclusions:Among patients undergoing outpatient laparoscopic cholecystectomy surgery, the use of preoperative dexamethasone enhanced postdischarge quality of recovery and reduced nausea, pain, and fatigue in the early postoperative period.

Postanesthesia care unit recovery times and neuromuscular blocking drugs: a prospective study of orthopedic surgical patients randomized to receive pancuronium or rocuronium.

In this study, we examined the effect of choice of neuromuscular blocking drug (NMBD) (pancuronium versus rocuronium) on postoperative recovery times and associated adverse outcomes in patients undergoing orthopedic surgical procedures. Seventy patients were randomly allocated to a pancuronium or rocuronium group. On arrival to the postanesthesia care unit (PACU) and again 30 min later, train-of-four ratios were quantified by using acceleromyography. Immediately after acceleromyographic measurements, patients were assessed for signs and symptoms of residual paresis. During the PACU admission, episodes of hypoxemia, nausea, and vomiting were recorded. The time required for patients to meet discharge criteria and the time of actual PACU discharge were noted. Forty percent of patients in the pancuronium group had train-of-four ratios <0.7 on arrival to the PACU, compared with only 5.9% of subjects in the rocuronium group (P < 0.001). Patients in the pancuronium group were more likely to experience symptoms of muscle weakness (blurry vision and generalized weakness; P < 0.001) and hypoxemia (10 patients in the rocuronium group versus 21 patients in the pancuronium group; P = 0.015) during the PACU admission. Significant delays in meeting PACU discharge criteria (50 min [45–60 min] versus 30 min [25–40 min]) and achieving actual discharge (70 min [60–90 min] versus 57.5 min [45–61 min]) were observed when the pancuronium group was compared with the rocuronium group (P < 0.001). In conclusion, our study indicates that PACU recovery times may be prolonged when long-acting NMBDs are used in surgical patients.

Pharmacokinetics of midazolam, propofol, and fentanyl transfer to human breast milk.

Lactating women undergoing operations requiring general anesthesia are advised to pump and discard their milk for 24 hours after the procedure. Data on anesthetic drug transfer into breast milk are limited. This study determined the pharmacokinetics of midazolam, propofol, and fentanyl transfer into milk to provide caregivers with data regarding the safety of breast milk after administration of these drugs.

Postoperative residual neuromuscular blockade is associated with impaired clinical recovery.

BACKGROUND:In this investigation, we sought to determine the association between objective evidence of residual neuromuscular blockade (train-of-four [TOF] ratio <0.9) and the type, incidence, and severity of subjective symptoms of muscle weakness in the postanesthesia care unit (PACU). METHODS:TOF ratios of 149 patients were quantified with acceleromyography on arrival to the PACU. Patients were stratified into 2 cohorts: a TOF <0.9 group (n = 48) or a TOF ≥0.9 (control) group (n = 101). A standardized examination determined the presence or absence of 16 symptoms and 11 signs of muscle weakness on arrival to the PACU and 20, 40, and 60 minutes after admission. RESULTS:The incidence of symptoms of muscle weakness was significantly higher in the TOF <0.9 group at all times (P < 0.001), as was the median (range) number of symptoms from PACU arrival (7 [3–6] TOF <0.9 group vs 2 [0–11] control group; difference 5, 99% confidence interval of the difference 4–6) until 60 minutes after admission (2 [0–12] TOF <0.9 group vs 0 [0–11] control group; difference 2, 99% confidence interval of the difference 1–2) (all P < 0.0001). CONCLUSION:The incidence and severity of symptoms of muscle weakness were increased in the PACU in patients with a TOF <0.9.