Glenn S. Murphy

Residual neuromuscular block: lessons unlearned. Part I: definitions, incidence, and adverse physiologic effects of residual neuromuscular block.

In this review, we summarize the clinical implications of residual neuromuscular block. Data suggest that residual neuromuscular block is a common complication in the postanesthesia care unit, with approximately 40% of patients exhibiting a train-of-four ratio <0.9. Volunteer studies have demonstrated that small degrees of residual paralysis (train-of-four ratios 0.7–0.9) are associated with impaired pharyngeal function and increased risk of aspiration, weakness of upper airway muscles and airway obstruction, attenuation of the hypoxic ventilatory response (approximately 30%), and unpleasant symptoms of muscle weakness. Clinical studies have also identified adverse postoperative events associated with intraoperative neuromuscular management. Large databased investigations have identified intraoperative use of muscle relaxants and residual neuromuscular block as important risk factors in anesthetic-related morbidity and mortality. Furthermore, observational and randomized clinical trials have demonstrated that incomplete neuromuscular recovery during the early postoperative period may result in acute respiratory events (hypoxemia and airway obstruction), unpleasant symptoms of muscle weakness, longer postanesthesia care unit stays, delays in tracheal extubation, and an increased risk of postoperative pulmonary complications. These recent data suggest that residual neuromuscular block is an important patient safety issue and that neuromuscular management affects postoperative outcomes.

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.

Optimal Perfusion During Cardiopulmonary Bypass: An Evidence-Based Approach

In this review, we summarize the best available evidence to guide the conduct of adult cardiopulmonary bypass (CPB) to achieve “optimal” perfusion. At the present time, there is considerable controversy relating to appropriate management of physiologic variables during CPB. Low-risk patients tolerate mean arterial blood pressures of 50–60 mm Hg without apparent complications, although limited data suggest that higher-risk patients may benefit from mean arterial blood pressures >70 mm Hg. The optimal hematocrit on CPB has not been defined, with large data-based investigations demonstrating that both severe hemodilution and transfusion of packed red blood cells increase the risk of adverse postoperative outcomes. Oxygen delivery is determined by the pump flow rate and the arterial oxygen content and organ injury may be prevented during more severe hemodilutional anemia by increasing pump flow rates. Furthermore, the optimal temperature during CPB likely varies with physiologic goals, and recent data suggest that aggressive rewarming practices may contribute to neurologic injury. The design of components of the CPB circuit may also influence tissue perfusion and outcomes. Although there are theoretical advantages to centrifugal blood pumps over roller pumps, it has been difficult to demonstrate that the use of centrifugal pumps improves clinical outcomes. Heparin coating of the CPB circuit may attenuate inflammatory and coagulation pathways, but has not been clearly demonstrated to reduce major morbidity and mortality. Similarly, no distinct clinical benefits have been observed when open venous reservoirs have been compared to closed systems. In conclusion, there are currently limited data upon which to confidently make strong recommendations regarding how to conduct optimal CPB. There is a critical need for randomized trials assessing clinically significant outcomes, particularly in high-risk patients.

Residual neuromuscular block: lessons unlearned. Part II: methods to reduce the risk of residual weakness.

The aim of the second part of this review is to examine optimal neuromuscular management strategies that can be used by clinicians to reduce the risk of residual paralysis in the early postoperative period. Current evidence has demonstrated that frequently used clinical tests of neuromuscular function (such as head lift or hand grip) cannot reliably exclude the presence of residual paralysis. When qualitative (visual or tactile) neuromuscular monitoring is used (train-of-four [TOF], double-burst, or tetanic stimulation patterns), clinicians often are unable to detect fade when TOF ratios are between 0.6 and 1.0. Furthermore, the effect of qualitative monitoring on postoperative residual paralysis remains controversial. In contrast, there is strong evidence that acceleromyography (quantitative) monitoring improves detection of small degrees (TOF ratios >0.6) of residual blockade. The use of intermediate-acting neuromuscular blocking drugs (NMBDs) can reduce, but do not eliminate, the risk of residual paralysis when compared with long-acting NMBDs. In addition, complete recovery of neuromuscular function is more likely when anticholinesterases are administered early (>15–20 minutes before tracheal extubation) and at a shallower depth of block (TOF count of 4). Finally, the recent development of rapid-onset, short-acting NMBDs and selective neuromuscular reversal drugs that can effectively antagonize deep levels of blockade may provide clinicians with novel pharmacologic approaches for the prevention of postoperative residual weakness and its associated complications.

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.

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.

Small-dose dexamethasone improves quality of recovery scores after elective cardiac surgery: a randomized, double-blind, placebo-controlled study.

OBJECTIVES The use of steroid therapy in cardiac surgical patients remains controversial. The aim of this clinical investigation was to determine the effect of small-dose dexamethasone therapy on patient-perceived quality of recovery (QoR) scores in elective cardiac surgical patients. In addition, the authors assessed the impact of dexamethasone on the incidence of common adverse events after cardiopulmonary bypass (CPB). DESIGN A prospective, randomized study. SETTING University hospitals. PARTICIPANTS One hundred seventeen patients undergoing cardiac surgery with CPB and anticipated early tracheal extubation. INTERVENTIONS Subjects were randomized to receive either dexamethasone (dexamethasone group, 8 mg at the induction of anesthesia and at the initiation of CPB) or placebo (control group, saline). MEASUREMENTS AND MAIN RESULTS The QoR was assessed using the QoR-40 scoring system preoperatively and on postoperative days (PODs) 1 and 2. Secondary outcome measures assessed in the postoperative period included nausea, vomiting, fatigue, febrile responses, shivering, pulmonary gas exchange, and analgesic requirements. Global QoR-40 scores (median [range]) were higher in the dexamethasone group compared with the control group on POD 1 (167 [133-192] v 157 [108-195]; p < 0.0001) and POD 2 (173 [140-196] v 166 [122-196]; p = 0.001). In the dexamethasone group, improved QoR was observed in the QoR-40 dimensions of emotional state (p = 0.002), physical comfort (p = 0.0001-0.006), and pain (p < 0.0001). The incidences or severity of postoperative fatigue (p < 0.0001), febrile responses (p < 0.0001), and shivering (p = 0.001) were reduced in the dexamethasone group. CONCLUSIONS Patient-perceived postoperative QoR in cardiac surgical patients is enhanced significantly by small-dose dexamethasone treatment.

Residual Neuromuscular Block in the Elderly: Incidence and Clinical Implications.

Background:Elderly patients are at increased risk for anesthesia-related complications. Postoperative residual neuromuscular block (PRNB) in the elderly, defined as a train-of-four ratio less than 0.9, may exacerbate preexisting muscle weakness and respiratory dysfunction. In this investigation, the incidence of PRNB and associated adverse events were assessed in an elderly (70 to 90 yr) and younger cohort (18 to 50 yr). Methods:Data were prospectively collected on 150 younger and 150 elderly patients. Train-of-four ratios were measured on arrival to the postanesthesia care unit (PACU). After tracheal extubation, patients were examined for adverse respiratory events during transport to the PACU, for 30 min after PACU admission, and during hospital admission. Postoperative muscle weakness was quantified using a standardized examination, and PACU and hospital lengths of stay were determined. Results:The incidence of PRNB was 57.7% in elderly and 30.0% in younger patients (difference, −27.7%; 99% CI, −41.2 to −13.1%; P < 0.001). Airway obstruction, hypoxemic events, signs and symptoms of muscle weakness, postoperative pulmonary complications, and increased PACU and hospital lengths of stay were observed more frequently in the elderly (all P < 0.01). Within each cohort, most adverse events were observed in patients with PRNB. Younger patients with PRNB received larger total doses of rocuronium than did those without it (60 vs. 50 mg, P < 0.01), but there were no differences in rocuronium dose between elderly patients with PRNB and those without it (both 50 mg). Conclusion:The elderly are at increased risk for PRNB and associated adverse outcomes.

The effect of single low-dose dexamethasone on blood glucose concentrations in the perioperative period: a randomized, placebo-controlled investigation in gynecologic surgical patients.

BACKGROUND:The effect of single low-dose dexamethasone therapy on perioperative blood glucose concentrations has not been well characterized. In this investigation, we examined the effect of 2 commonly used doses of dexamethasone (4 and 8 mg at induction of anesthesia) on blood glucose concentrations during the first 24 hours after administration. METHODS:Two hundred women patients were randomized to 1 of 6 groups: Early-control (saline); Early-4 mg (4 mg dexamethasone); Early-8 mg (8 mg dexamethasone); Late-control (saline); Late-4 mg (4 mg dexamethasone); and Late-8 mg (8 mg dexamethasone). Blood glucose concentrations were measured at baseline and 1, 2, 3, and 4 hours after administration in the early groups and at baseline and 8 and 24 hours after administration in the late groups. The incidence of hyperglycemic events (the number of patients with at least 1 blood glucose concentration >180 mg/dL) was determined. RESULTS:Blood glucose concentrations increased significantly over time in all control and dexamethasone groups (from median baselines of 94 to 102 mg/dL to maximum medians ranging from 141 to 161.5 mg/dL, all P < 0.001). Blood glucose concentrations did not differ significantly between the groups receiving dexamethasone (either 4 or 8 mg) and those receiving saline at any measurement time. The incidence of hyperglycemic events did not differ in any of the early (21%–28%, P = 0.807) or late (13%–24%, P = 0.552) groups. CONCLUSIONS:Because blood glucose concentrations during the first 24 hours after administration of single low-dose dexamethasone did not differ from those observed after saline administrations, these results suggest clinicians need not avoid using dexamethasone for nausea and vomiting prophylaxis out of concerns related to hyperglycemia.