Performing post-tetanic count during rocuronium blockade has limited impact on subsequent twitch height or train-of-four responses.

BACKGROUND: Waiting five to six minutes before measuring a train-of-four (TOF) after a 50-Hz tetanic stimulation or post-tetanic count (PTC) in order to allow the facilitation of transmission to subside is commonly recommended but is based on limited evidence. The purpose of this study was to measure the TOF responses after PTC in one hand and to compare the responses with those in the contralateral (control) hand. METHODS: Twenty-two adult patients undergoing elective surgery under opioid-desflurane anesthesia were fitted with sensors to measure displacement of their thumbs in response to ulnar nerve stimulation. Rocuronium 0.6 mg·kg(-1) was administered and TOF stimulation was applied to both sides. One side was randomized to PTC (50-Hz tetanus followed by a three-second pause and 15 1-Hz stimuli) when the opposite (control) side recovered to 10% first twitch (T1) height. Train-of-four stimulation was continued bilaterally every 20 sec until 30 min after PTC. Comparisons of the T1 and TOF ratio (T4/T1) were made at two, five, ten, 20, and 30 min. RESULTS: The mean (standard deviation [SD]) T1 value in the PTC arm was 11.8 (7.1)% just before PTC. The T1 values were significantly greater in the PTC arm at two, five, and ten minutes, with mean (SD) differences of 6.3 (6.7)%, 9.4 (6.8)%, and 7.4 (3.9)%, respectively (P = 0.008). There were no significant differences in T1 values between groups at 20 and 30 min, and no statistically significant differences in T4/T1 values at any time. CONCLUSION: A small but clinically insignificant increase in T1 is seen for at least ten minutes after PTC without any detectable change in T4/T1 values. The TOF responses are reliable as early as one minute after PTC.

Do we really need sugammadex as an antagonist of muscle relaxants in anesthesia?

PURPOSE OF REVIEW: Sugammadex is a selective relaxant-binding agent that is designed to encapsulate rocuronium and chemically similar steroidal muscle relaxants such as vecuronium. This review summarizes recent information on the use of sugammadex in clinical practice. RECENT FINDINGS: The main advantages of sugammadex when compared with conventional anticholinesterase agents are a much faster recovery time and its unique ability to reverse rapidly and efficiently, for the first time, deep levels of neuromuscular blockade. However, there is paucity of evidence-based studies on the benefit of deep neuromuscular block, and then routine administration of sugammadex to reverse any level of block, for example, during laparoscopic surgery. It appears that reduction of costs depends mainly on organizational factors. Finally it must be remembered that sugammadex only works with steroidal nondepolarizing muscle relaxants; therefore neostigmine should not be withdrawn because it is the only reversal agent effective against atracurium or cisatracurium. SUMMARY: Sugammadex offers a significantly faster and more predictable recovery profile than neostigmine. It is now possible to reverse rapidly and efficiently any level of neuromuscular blockade and to avoid the risk of adverse events because of residual paralysis such as critical respiratory events during recovery from anesthesia.

Replacing a double-lumen tube with a single-lumen tube or a laryngeal mask airway device to reduce coughing at emergence after thoracic surgery: a randomized controlled single-blind trial.

BACKGROUND: Coughing episodes occur frequently at extubation after thoracic surgery, and this may be due in part to the double-lumen tube (DLT). In this study, the DLT was replaced with either a single-lumen endotracheal tube (ETT) or a laryngeal mask airway (LMA) device or left in place, and the incidence of coughing at emergence was compared between the three groups. METHODS: Fifty-eight adults scheduled for thoracic surgery with a DLT were included. Exclusion criteria were an anticipated difficult airway, obesity, and contraindication to the use of an LMA ProSeal™ (LMA-P). After surgery but before emergence, patients were randomized to having the DLT (1) removed and replaced by an LMA-P (LMA-P Group), (2) removed and replaced by an ETT (ETT Group), or (3) left in place (DLT Group). The primary outcome was the number of coughing episodes at extubation. RESULTS: Among 184 patients screened, 124 did not meet inclusion criteria, and two patients, both in the ETT Group, were excluded after randomization, leaving 20, 18, and 20 patients in the LMA-P, ETT, and DLT Groups, respectively. There were fewer coughing episodes (median [quartiles]) in the LMA-P Group than in the DLT Group (0[0-1] vs 2[1-3], respectively; P = 0.01). In the DLT Group, 90% of patients coughed at least once. This incidence was not significantly different in the ETT Group (83%; P = 0.222) but was significantly reduced in the LMA-P Group (35%; P < 0.001). No patient had oxygen desaturation during airway exchange or at extubation. The incidence and severity of hoarseness and sore throat were similar in all groups. CONCLUSION: Coughing at extubation after thoracic surgery can be reduced if the DLT is replaced by an LMA-P before emergence. The number of patients in this trial was too small to evaluate the risks associated with exchanging the airway device. This trial was registered at ClinicalTrials.gov: NCT00925613.

Step-by-step clinical management of one-lung ventilation: continuing professional development.

PURPOSE: The purpose of this Continuing Professional Development Module is to review the issues pertinent to one-lung ventilation (OLV) and to propose a management strategy for ventilation before, during, and after lung isolation. PRINCIPAL FINDINGS: The need for optimal lung isolation has increased with the advent of video-assisted thoracoscopic surgery, as surgical exposure is critical for successful surgery. Continuous positive airway pressure applied to the operative lung or intermittent two-lung ventilation should therefore be avoided if possible. Optimal management of OLV should provide adequate oxygenation and also prevent acute lung injury (ALI), the leading cause of death following lung resection. Research conducted in the last decade suggests implementing a protective ventilation strategy during OLV that consists of small tidal volumes based on ideal body weight, routine use of positive end-expiratory pressure, low inspired oxygen fraction, with low peak and plateau airway pressures. High respiratory rates to compensate for low tidal volumes may predispose to significant air trapping during OLV, so permissive hypercapnea is routinely employed. The management of OLV extends into the period of two-lung ventilation, as the period prior to OLV impacts lung collapse, and both the time before and after OLV influence the extent of ALI. Lung re-expansion at the conclusion of OLV is an important component of ensuring adequate ventilation and oxygenation postoperatively but may be harmful to the lung. CONCLUSIONS: Optimal perioperative care of the thoracic patient includes a protective ventilation strategy from intubation to extubation and into the immediate postoperative period. Anesthetic goals include the prevention of perioperative hypoxemia and postoperative ALI.

Randomized prospective trial comparing two supraglottic airway devices: i-gel™ and LMA-Supreme™ in paralyzed patients.

PURPOSE: Many features can influence the choice of a supraglottic airway device (SAD), including ease of insertion, adequate ventilation pressures and lack of adverse effects. The goal of this randomized prospective trial was to compare the performance of the i-gel™ with that of the LMA-Supreme™. METHODS: One hundred adult patients (American Society of Anesthesiologists I-III) scheduled to undergo elective surgery under general anesthesia were randomized to either an i-gel (n = 50) or an LMA-Supreme (n = 50). The primary objective was to compare ventilation pressures. Secondary objectives included time and number of attempts needed to introduce the device, adverse effects, and repositioning. The endoscopic view of the glottic aperture and the position of the drain tubes in relation to the esophagus were also evaluated. RESULTS: The devices were inserted successfully in 46 (92%) patients in both groups. There was no significant difference in the [mean (SD)] leak pressure [i-gel: 23 (7) cm H2O vs LMA-Supreme: 21 (8) cm H2O; P = 0.14] or peak inspiratory pressure between both devices. Insertion time was shorter with the i-gel than with the LMA-Supreme [19 (7) sec vs 27 (17) sec, respectively; P = 0.003]. The vocal cords were completely visualized more often through the i-gel (70%) than through the LMA-Supreme (50%) (P = 0.007). Esophageal mucosa was easily visualized through the drain port in all but four patients, two patients in each group. There was no difference between groups regarding preoperative or postoperative complications. Postoperative patient discomfort was generally mild and comparable between both devices. CONCLUSION: Both the LMA-Supreme and the i-gel offer similar performance for positive pressure ventilation in paralyzed patients during general anesthesia. The i-gel was associated with a slightly faster insertion time and better fibrescopic visualization of the glottis. This trial was registered at Clinicaltrials.gov: NCT01001078.

Magnetic interference of cardiac pacemakers from a surgical magnetic drape.

Sterile magnetic drapes are frequently used during surgery to hold metal instruments on the sterile field. Magnetic fields may potentially interfere with the function of cardiovascular implantable electronic devices such as pacemakers and implantable cardioverter defibrillators. In this study, we evaluated the potential magnetic interference of magnetic drapes on pacemaker function. A magnetic drape with 70 magnets was placed with its approximate center over the pacemaker of 50 patients during their visit to the cardiology clinic. In those pacemakers that demonstrated magnetic interference, the drape was pulled caudally in 3-cm increments until the interference ceased. If there was no interference, the drape was folded in 2 over the pacemaker. The number of magnets necessary to maintain magnetic interference with the pacemaker was also tested. Magnetic interference was observed in the pacemakers of 47 (94%) patients: 35 with the unfolded drape and another 12 with the folded drape. Patients whose pacemakers had interference with the unfolded drape weighed less (68 ± 15 kg vs 81 ± 19 kg; P = 0.016) than those who had no interference. In 54% of patients, magnetic interference ceased when the drape was pulled 3 cm caudally and at 15 cm, no pacemaker had magnetic interference. Magnetic drapes may cause magnetic interference with cardiac pacemakers, and this interference ceases at a caudal distance of 15 cm. Magnetic interference seems more likely in patients with lower body weight. Careful monitoring of the pulse and electrocardiogram for asynchronous pacing activity should be considered when magnetic drapes are used in patients with cardiovascular implantable electronic devices.

Residual paralysis: a real problem or did we invent a new disease?

PURPOSE: Over the past three decades, many studies have shown a high proportion of patients in the recovery room with residual neuromuscular blockade after anesthesia. The purpose of this Continuing Professional Development module is to present the physiological consequences of residual paralysis, estimate the extent of the problem, and suggest solutions to prevent its occurrence. PRINCIPAL FINDINGS: Residual paralysis is defined as a train-of-four ratio (TOFR) < 0.9 at the adductor pollicis. While tidal volume and, to a lesser extent, vital capacity are well preserved as the intensity of blockade increases, the probability of airway obstruction, impaired swallowing, and pulmonary aspiration increases markedly as TOFR decreases. In recent studies, incidences of residual paralysis from 4-57% have been reported, but surveys indicate that anesthesiologists estimate the incidence of the problem at 1% or less. The decision to administer neostigmine or sugammadex should be based on the degree of spontaneous recovery at the adductor pollicis muscle (thumb), not on recovery at the corrugator supercilii (eyebrow). The most important drawback of neostigmine is its inability to reverse profound blockade, which is a consequence of its ceiling effect. When spontaneous recovery reaches the point where TOFR > 0.4 or four equal twitch responses are seen, reduced doses of neostigmine may be given. The dose of sugammadex required in a given situation depends on the intensity of blockade. CONCLUSION: Careful monitoring and delaying the administration of neostigmine until four twitches are observed at the adductor pollicis can decrease the incidence of residual paralysis. The clinical and pharmacoeconomic effects of unrestricted sugammadex use are unknown at this time.

Review article: video-laryngoscopy: another tool for difficult intubation or a new paradigm in airway management?

BACKGROUND: An adequate airway management plan is essential for patient safety. Recently, new tools have been developed as alternatives to direct laryngoscopy and intubation. Among these, video-laryngoscopy has enjoyed a rapid increase in popularity and is now considered by many as the first-line technique in airway management. This paradigm shift may have an impact on patient safety. PRINCIPAL FINDINGS: Studies show that video-laryngoscopes are associated with better glottic visualization, a higher success rate for difficult airways, and a faster learning curve, resulting in a higher success rate for intubations by novice physicians. Thus, unanticipated difficult intubations may be less frequent if video-laryngoscopy is used as the first-line approach. In addition, on-screen viewing by the operator creates a new dynamic interaction during airway management. The entire operating room team can assess progress in real time, which enhances communication and improves teaching. However, if video-laryngoscopes become standard tools for tracheal intubation, these more costly devices will need to be widely available in all locations where airway management is conducted. Furthermore, algorithms for difficult intubation will require modification, and the question of selecting alternate devices will arise. If the incidence of difficult intubation decreases, the lack of motivation to teach and learn the use of alternative devices might adversely impact patient safety. CONCLUSION: The greater effectiveness of video-laryngoscopes associated with multi-person visualization could enhance overall patient safety during airway management. However, the routine use of video-laryngoscopy also introduces some issues that need to be addressed to avoid potentially dangerous pitfalls.

Antagonism of low degrees of atracurium-induced neuromuscular blockade: dose-effect relationship for neostigmine.

BACKGROUND: Low degrees of residual paralysis (i.e., a train-of-four [TOF] ratio > 0.4) are relatively frequent, difficult to detect, and still potentially harmful. Unfortunately, the appropriate dose of anticholinesterase for this situation has not been determined. This may be of clinical interest because a high dose of neostigmine given at a shallow level of neuromuscular block may produce neuromuscular weakness. The purpose of this study was to investigate the dose-effect relationship of neostigmine to antagonize residual paralysis corresponding to a TOF ratio of 0.4 and 0.6. METHODS: Recovery after 10, 20, 30 microg/kg neostigmine or placebo given at either 0.4 or 0.6 TOF ratio was assessed by acceleromyography in 120 patients undergoing intravenous anesthesia. Time to a 0.9 and 1.0 TOF ratio was measured, and the probability of successful reversal within 10 min after the respective neostigmine doses was calculated. In addition, the dose of neostigmine needed to achieve the recovery targets in 5 or 10 min was also determined. RESULTS: When given at a TOF ratio of either 0.4 or 0.6, time to 0.9 and 1.0 TOF ratio was significantly shorter with any dose of neostigmine than without. The probability of successful reversal after 20 microg/kg neostigmine was 100% when a TOF ratio of 0.9 was the target; for a TOF ratio of 1.0, the probability was 93% and 67%, dependent on whether the dose of neostigmine was given at TOF ratio of 0.6 or 0.4, respectively. With a dose of 30 microg/kg, a TOF ratio of 1.0 is expected to be reached within approximately 5 min. Low doses of neostigmine are required to reach a TOF ratio of 0.9 or to accept an interval of 10 min. CONCLUSION: Reduced doses (10-30 microg/kg) of neostigmine are effective in antagonizing shallow atracurium block. For successful reversal within 10 min, as little as 20 microg/kg neostigmine may be sufficient. These dose recommendations are specific for atracurium and an intravenous anesthetic background.

Rapid sequence induction for appendectomies: a retrospective case-review analysis.

PURPOSE: Rapid sequence induction (RSI) with cricoid pressure is suggested to decrease the risk of aspiration of gastric contents. However, the effectiveness of RSI has been questioned, and the technique may lead to airway and hemodynamic complications. The purpose of this study was to determine the frequency of RSI use in patients with acute appendicitis, the types of drugs administered, and the occurrence of any complications. METHODS: After approval by the Ethics Committee, the charts of patients undergoing appendectomy in a one-year period were examined retrospectively. Information was retrieved on Mallampati airway evaluation, airway device used, preoxygenation, RSI, and drugs at induction. Reported complications were noted, including airway difficulties, hypotension (systolic blood pressure < 80 mmHg) and hypertension (>160 mmHg) in the 20-min period after induction. RESULTS: General anesthesia with tracheal intubation was used in 248 of 250 cases reviewed. The Mallampati airway evaluation, preoxygenation, and RSI were recorded as performed in 95, 94, and 81% of cases, respectively. Opioids, propofol, and neuromuscular blocking agents were given in 98, 98, and 99% of patients, respectively. Succinylcholine use was common (80%), with 96% of these patients receiving rocuronium precurarization. Difficult intubation with successful alternate technique was encountered in three patients (1.2%). Hypotension and hypertension occurred in 27% and 8% of patients, respectively. There were no documented cases of aspiration. Oxygen desaturation was mentioned in one case at induction and in three cases at emergence. CONCLUSION: An RSI with opioid, induction agent, and succinylcholine is the technique of choice for appendectomies at our institution. The frequency of airway complications is too low to recommend a change in practice.

Perception of simulated local shapes using active and passive touch.

This study reexamined the perceptual equivalence of active and passive touch using a computer-controlled force-feedback device. Nine subjects explored a 6 x 10-cm workspace, with the index finger resting on a mobile flat plate, and experienced simulated Gaussian ridges and troughs (width, 15 mm; amplitude, 0.5 to 4.5 mm). The device simulated shapes by modulating either lateral resistance with no vertical movement or by vertical movement with no lateral forces, as a function of the digit position in the horizontal workspace. The force profiles and displacements recorded during active touch were played back to the stationary finger in the passive condition, ensuring that stimulation conditions were identical. For the passive condition, shapes simulated by vertical displacements of the finger had lower categorization thresholds and higher magnitude estimates compared with those of active touch. In contrast, the results with the lateral force fields showed that with passive touch, subjects recognized that a stimulus was present but were unable to correctly categorize its shape as convex or concave. This result suggests that feedback from the motor command can play an important role in processing sensory inputs during tactile exploration. Finally, subjects were administered a ring-block anesthesia of the digital nerves of the index finger and subsequently retested. Removing skin sensation significantly increased the categorization threshold for the perception of shapes generated by lateral force fields, but not for those generated by displacement fields.

Optimizing preoxygenation in adults.

PURPOSE: Preoxygenation increases oxygen reserves and duration of apnea without desaturation (DAWD), thus it provides valuable additional time to secure the airway. The purpose of this Continuing Professional Development (CPD) module is to examine the various preoxygenation techniques that have been proposed and to assess their effectiveness in healthy adults and in obese, pregnant, and elderly patients. PRINCIPAL FINDINGS: The effectiveness of preoxygenation techniques can be evaluated by measuring DAWD, i.e., the time for oxygen saturation to decrease to <90%. Clinically, preoxygenation is considered adequate when end-tidal oxygen fraction is >90%. This is usually achieved with a 3-min tidal volume breathing (TVB) technique. As a rule, asking the patient to take four deep breaths in 30 sec (4 DB 30 sec) yields poorer results. Eight deep breaths in 60 sec (8 DB 60 sec) is equivalent to TVB 3 min. The DAWD is decreased in obese patients, pregnant women, and patients with increased metabolism. Obese patients may benefit from the head-up position and positive pressure breathing. A TVB technique is preferable in the elderly. Failure to preoxygenate is often due to leaks, which commonly occur in edentulous or bearded patients. In cases of difficult preoxygenation, directly applying the circuit to the mouth might be a useful alternative. Supplying extra oxygen in the nasopharynx during apnea might increase DAWD. CONCLUSION: Since ventilation and tracheal intubation difficulties are unpredictable, this CPD module recommends that all patients be preoxygenated. The TVB 3 min and the 8 DB 60 sec techniques are suitable for most patients; however, the 4 DB 30 sec is inadequate.

Low-dose fentanyl-midazolam combination improves sevoflurane induction in adults.

PURPOSE: We investigated the effects of a combination of low-dose fentanyl-midazolam premedication on the speed of inhaled induction with sevoflurane and ProSeal laryngeal mask airway (PLMA) insertion conditions. METHODS: Eighty adult patients undergoing elective surgery were randomized in a double-blind fashion to receive either a normal saline placebo (Group PLAC) or a fentanyl 0.6 microg x kg(-1) and midazolam 9 microg x kg(-1) premedication (Group FM) 5 min before tidal volume sevoflurane 8%/O(2) induction. Anxiety levels, times to loss of eyelash reflex (LER) and PLMA insertion, and cardiorespiratory data were recorded. RESULTS: Times to LER (Group PLAC: 66 +/- 34 sec vs Group FM: 47 +/- 18 sec, P = 0.0027, difference = 19 sec: 95% confidence interval [CI] 7-31 sec) and to PLMA insertion (Group PLAC: 186 +/- 80 sec vs Group FM: 119 +/- 44 sec, P < 0.0001, difference = 68 sec: 95% CI 39-97 sec) were shorter following FM. After PLMA insertion, end-tidal sevoflurane concentration (EtSevo) was lower and end-tidal CO(2) (EtCO(2)) was higher following FM. Respiratory rate (RR) was lower with FM, but there was no difference regarding tidal volume. Adverse events, such as movements and apnea, occurred more often in Group PLAC. Systolic blood pressure (SBP) and heart rate (HR) during induction were both lower with FM. Anxiety level after premedication was lower following FM administration. All participants remembered the face mask being applied in Group PLAC vs 69% in Group FM, P < 0.0001. CONCLUSION: Administration of a low-dose fentanyl-midazolam combination prior to sevoflurane induction decreases time to LER and allows for more rapid and less eventful PLMA insertion. Both SBP and HR were lower when premedication was administered. Patients receiving premedication were less anxious and less likely to remember the face mask. However, premedication was associated with a lower RR and increased EtCO(2) values following PLMA insertion, in spite of lower EtSevo concentrations. (ClinicalTrials.gov ID NCT00723164).