Can final EMG baseline be used as a reference to calculate neuromuscular recovery?

Effects of SZ1677, a new non-depolarizing steroidal neuromuscular blocking drug, and rocuronium on two laryngeal muscles and the anterior tibial muscle in guinea pigs

BACKGROUND

SZ1677 is a new neuromuscular blocking drug structurally related to rocuronium. We compared the effect of an ED(90) of SZ1677 (25 microg/kg) with that of rocuronium (100 microg/kg) in guinea pig laryngeal and peripheral muscles.

METHODS

Electromyography was used to quantify neuromuscular blockade at the posterior cricoarytenoid muscle, the thyroarytenoid muscle and the anterior tibial muscle after SZ1677 (n = 10) and rocuronium (n = 9).

RESULTS

Maximum neuromuscular blockade was similar after SZ1677 and rocuronium (83 +/- 11% vs. 89 +/- 11%; thyroarytenoid muscle: 91 +/- 8% vs. 97 +/- 3%; anterior tibial muscle: 91 +/- 15% vs. 96 +/- 3%, respectively). Onset time of neuromuscular blockade at the laryngeal muscles was similar for the two neuromuscular blocking drugs; it was shorter at the thyroarytenoid muscle (67 +/- 32 s vs. 42 +/- 40 s) than at the posterior cricoarytenoid muscle (101 +/- 26 s vs. 102 +/- 108 s). Onset time at the anterior tibial muscle was longer after SZ1677 (114 +/- 34 s) than after rocuronium (68 +/- 46 s); P < 0.05. Neuromuscular recovery was faster after SZ1677 (interval 25%-75%: posterior cricoarytenoid muscle: 222 +/- 66 s; thyroarytenoid muscle: 192 +/- 92 s; tibial muscle 149 +/- 55 s) than after rocuronium (450 +/- 148 and 464 +/- 183 s, 292 +/- 86 s, respectively); P < 0.05.

CONCLUSIONS

In guinea pigs, SZ1677 offers a rapid onset of neuromuscular blockade at a laryngeal adductor muscle with a shorter duration than rocuronium. Regardless of the drug used, the course of neuromuscular blockade differs not only between peripheral muscles and the larynx but also between antagonistic laryngeal muscles. The differences seem to be species specific.

Spontaneous recovery profile of rapacuronium during desflurane, sevoflurane, or propofol anesthesia for outpatient laparoscopy

We evaluated the spontaneous recovery characteristics of rapacuronium during desflurane-, sevoflurane-, or propofol-based anesthesia in 51 consenting women undergoing laparoscopic tubal ligation procedures. After the induction of the anesthesia with standardized doses of propofol and fentanyl, 1.5 mg/kg IV rapacuronium was administered to facilitate tracheal intubation. Patients were randomized to receive either 1 minimum alveolar anesthetic concentration of desflurane, 1 minimum alveolar concentration of sevoflurane, or 100 microg. kg(-1). min(-1) propofol infusion in combination with 66% nitrous oxide in oxygen for maintenance of anesthesia. Neuromuscular blockade was monitored at the wrist by using electromyography. The degree of maximum blockade and the times for first twitch recovery (T(1)) to 5%, 25%, 50%, 75%, and 90%, as well as the recovery index, were similar in all three anesthetic groups. However, recovery times for the train-of-four ratio to achieve 0.7 and 0.8 were significantly longer with desflurane (44.4 +/- 18.9 and 53.5 +/- 22.4 min) and sevoflurane (44.8 +/- 15.1 and 53.2 +/- 15.8 min) compared with propofol (31.8 +/- 5.3 and 36.5 +/- 6.5 min). Eight patients (16%) required a maintenance dose of 0.5 mg/kg rapacuronium and reversal of rapacuronium residual block occurred in three (6%) patients. We conclude that spontaneous recovery after an intubating dose of 1.5 mg/kg rapacuronium was significantly prolonged by both desflurane and sevoflurane compared with propofol-based anesthesia. Routine monitoring of neuromuscular activity is recommended even when a single bolus dose of rapacuronium is administered during ambulatory anesthesia.

IMPLICATIONS

When administered for laparoscopic surgery, the duration of action of an intubating dose of rapacuronium was prolonged 40%-50% by desflurane and sevoflurane, respectively, (versus propofol). Monitoring recovery of neuromuscular blockade produced by rapacuronium is particularly important when desflurane or sevoflurane is administered to ensure that an adequate recovery (train-of-four > or = 0.8) is achieved by the end of anesthesia.

Onset/offset characteristics and intubating conditions of rapacuronium: a comparison with rocuronium

We compared onset and offset of action and tracheal intubating conditions after rapacuronium and rocuronium in 60 patients in a randomized, assessor-blinded study. Following induction of anaesthesia with propofol 2.5 mg kg-1, either rapacuronium 1.5 mg kg-1 (n = 30) or rocuronium 0.6 mg kg-1 (n = 30) was administered to facilitate tracheal intubation. Anaesthesia was maintained with either a propofol infusion (100 micrograms kg-1 min-1) or sevoflurane (1% end-tidal) with 66% nitrous oxide (N2O), n = 15 in each subgroup. Neuromuscular monitoring was performed using an electromyographic (EMG) device (Datex Relaxograph). The lag times (mean 42 (SD 11) s and 44 (16) s), maximum block (99 (2)% and 98 (3)%) and intubating conditions at 60 s (good-to-excellent in 86% and 84% of patients) were similar for rapacuronium and rocuronium, respectively. The onset time of rapacuronium was shorter than rocuronium (87 (20) vs 141 (65) s, P < 0.001), and the degree of block at 60 s was greater (69 (26) vs 50 (27)%, P < 0.05). Twenty-five per cent recovery was shorter with rapacuronium than rocuronium during propofol (15.0 (3.2) vs 39.1 (14.2) min, P < 0.001) and sevoflurane (15.1 (4.2) vs 47.8 (19.0) min, P < 0.001) anaesthesia. We conclude that rapacuronium 1.5 mg kg-1 had a more rapid onset, similar intubating conditions, and shorter recovery times than rocuronium 0.6 mg kg-1.

Effects of vecuronium and rocuronium in antagonistic laryngeal muscles and the anterior tibial muscle in the cat

BACKGROUND

Adequate vocal cord paralysis and full recovery of laryngeal muscle function are important when muscle relaxants are used perioperatively. This study was designed to compare the effects of vecuronium and rocuronium at the vocal cord abductor and adductor muscles and the anterior tibial muscle in cats.

METHODS

Twelve adult cats were studied under pentobarbitone-N2O/O2-anesthesia. After supramaximal electrical stimulation of the peroneal nerve and the recurrent laryngeal nerve (0.1 Hz and intermittent train-of-four) evoked electromyographic responses were obtained from the anterior tibial muscle, the posterior cricoarytenoid muscle (vocal cord abductor) and two vocal cord adductor muscles, the lateral cricoarytenoid and the vocal muscle. Six cats received bolus doses of increasing size of vecuronium (ED90 22.5 microg x kg(-1)) and six cats rocuronium (ED90 90 microg x kg(-1)).

RESULTS

Equipotent doses of vecuronium and rocuronium caused a similar degree of paralysis in all muscles (vecuronium ED90: 70% blockade at the posterior cricoarytenoid, 83% at the lateral cricoarytenoid, 84% at the vocal muscle and 90% at the anterior tibial muscle; rocuronium ED90: 71% at the posterior cricoarytenoid, 67% at the lateral cricoarytenoid, 78% at the vocal muscle and 90% at the anterior tibial muscle; vecuronium 2 x ED90: 93% blockade at the posterior cricoarytenoid, 95% at the lateral cricoarytenoid, 97% at the vocal muscle and 99% at the anterior tibial muscle; rocuronium 2 x ED90: 89% blockade at the posterior and lateral cricoarytenoid, 93% at the vocal muscle and 100% at the anterior tibial muscle). Onset time was significantly shorter at the posterior cricoarytenoid muscle (290 s) compared to the lateral cricoarytenoid muscle (400 s) after vecuronium ED90 and to the vocal muscle (150 s versus 210 s) after rocuronium ED90. Compared to the anterior tibial muscle (interval 25-75%: 6.5 min after vecuronium 2 x ED90 and 3.3 min after rocuronium 2 x ED90 and to the posterior cricoarytenoid muscle (interval 25-75%: 7 min after vecuronium 2 x ED90 and 4.3 min after rocuronium 2 x ED90), recovery of laryngeal adductor muscle function was markedly delayed with both neuromuscular blocking drugs (interval 25-75% at the lateral cricoarytenoid and vocal muscle: 14 min and 15.8 min after vecuronium 2 x ED90 and 10.3 min and 11.6 min after rocuronium 2 x ED90 respectively).

CONCLUSION

In cats, the time course of neuromuscular blockade after vecuronium and rocuronium differs in antagonistic laryngeal muscles. The protective laryngeal function of glottis closure recovers later than vocal cord abduction after both vecuronium and rocuronium.

Early and late reversal of rocuronium and vecuronium with neostigmine in adults and children

We investigated the influence of the timing of neostigmine administration on recovery from rocuronium or vecuronium neuromuscular blockade. Eighty adults and 80 children were randomized to receive 0.45 mg/kg rocuronium or 0.075 mg/kg vecuronium during propofol/fentanyl/N2O anesthesia. Neuromuscular blockade was monitored by train-of-four (TOF) stimulation and adductor pollicis electromyography. Further randomization was made to control (no neostigmine) or reversal with 0.07 mg/kg neostigmine/0.01 mg/kg glycopyrrolate given 5 min after relaxant, or first twitch (T1) recovery of 1%, 10%, or 25%. Another eight adults and eight children received 1.5 mg/kg succinylcholine. At each age, spontaneous recovery of T1 and TOF was similar after rocuronium and vecuronium administration but was more rapid in children (P < 0.05). Spontaneous recovery to TOF0.7 after rocuronium and vecuronium administration in adults was 45.7 +/- 11.5 min and 52.5 +/- 15.6 min; in children, it was 28.8 +/- 7.8 min and 34.6 +/- 9.0 min. Neostigmine accelerated recovery in all reversal groups (P < 0.05) by approximately 40%, but the times from relaxant administration to TOF0.7 were similar and independent of the timing of neostigmine administration. Recovery to T1 90% after succinylcholine was similar in adults (9.4 +/- 5.0 min) and children (8.4 +/- 1.1 min) and was shorter than recovery to TOF0.7 in any reversal group after rocuronium or vecuronium administration. Recovery from rocuronium and vecuronium blockade after neostigmine administration was more rapid in children than in adults. Return of neuromuscular function after reversal was not influenced by the timing of neostigmine administration. These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated.

IMPLICATIONS

These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated. Although spontaneous and neostigmine-assisted recovery is more rapid in children than in adults, in neither is return of function as rapid as after succinylcholine administration.

Decreased mivacurium requirements and delayed neuromuscular recovery during sevoflurane anesthesia in children and adults

The purpose of this study was to compare the mivacurium infusion requirements and neuromuscular recovery in adults and children during propofol/opioid and sevoflurane anesthesia. Seventy-five adult and 75 pediatric patients were randomized to receive propofol/opioid 0.5 or 1.0 minimum alveolar anesthetic concentration (MAC) (age-related) sevoflurane anesthesia. Plasma cholinesterase (PChE) activity was measured. Neuromuscular blockade was monitored by train-of-four (TOF) stimulation every 10 s and adductor pollicis electromyography. A bolus of 2 x the 95% effective dose of mivacurium (0.25 mg/kg) was followed by an infusion titrated to maintain 90%-95% blockade. Mivacurium doses were recorded every 5 min. At the end of surgery, the infusion was stopped, and recovery from mivacurium was monitored until TOF > or =0.7. PChE concentrations were within the normal range (adults 4-12 KU/L, children 6-16 KU/L) and correlated with mivacurium dose. Mivacurium infusion rates were higher in children than in adults: at 30 min, the rates in children were 13.1 +/- 6.4, 8.1 +/- 4.7, and 5.2 +/- 2.9 microg x kg(-1) x min(-1) at 0, 0.5, and 1.0 MAC sevoflurane, respectively; the corresponding rates in adults were 5.9 +/- 3.1, 4.3 +/- 1.7, and 2.9 +/- 0.7 microg x kg(-1) x min(-1) (P < 0.01). Sevoflurane decreased mivacurium requirements, maximal decreases at 45 min in children and 10 min in adults, and delayed neuromuscular function recovery. Children recovered twice as quickly as adults, achieving TOF > or =0.7 at 9.8 +/- 2.5, 11.4 +/- 2.8, and 19.6 +/- 6.3 min compared with 19.9 +/- 5.4, 26.4 +/- 8.3, and 32.9 +/- 9.8 min in adults (P < 0.0001). In conclusion, mivacurium requirements were correlated with PChE, were greater in children than in adults, and were reduced by sevoflurane. Neuromuscular recovery occurred more rapidly in children and was delayed by sevoflurane.

IMPLICATIONS

The mivacurium infusion requirement to maintain constant 90%-95% neuromuscular block during anesthesia is correlated with plasma cholinesterase activity. It is increased in children and reduced by the inhaled anesthetic sevoflurane. Despite the larger dose administered to children, recovery from block occurred more rapidly in children than in adults and was delayed by sevoflurane.