Antagonism of pancuronium- and pipecuronium-induced neuromuscular block

We have compared the antagonism of neuro muscular block producedby pipecuronium with pancuronium in 80 anaesthetized surgicalpatients using mechanomyography and electromyography. Pancuronium0.1 mg kg or pipecuronium 0.07 mg kg^–1 was given afterinduction of anaesthesia and neuromuscular block was adjustedto 75% twitch depression at the time of antagonism. The followingregimens were used: edrophonium 0.5 and 1.0 mg kg^–1, neostigmine0.04 mg kg^–1 pyridostigmine 0.3 mg kg^–1 and edrophonium0.25 mg kg^–1 with pyridostigmine 0.15 mg kg^–1. Antagonismwas evaluated also by the head lift test. There was no differencebetween the reversibility of neuromuscular block produced bypancuronium or pipecuronium. Edrophonium produced a significantlyfaster antagonism than neostigmine or pyridostigmine but onsetof action was not significantly faster than that of edrophoniumwith pyridostigmine. All regimens produced 100% (or near 100%)antagonism of twitch response within 15 min. However, TOF fadeantagonism was more complete with pyridostigmine, neostigmineand edrophonium 1.0 mg kg^–1 than with edrophonium 0.5mg kg^–1. The head lift test indicated somewhat less antagonismwith edrophonium 0.5 and 1.0 mg kg^–1. Using five monitoringmethods, the rank order of reversal potency was: pyridostigmine neostigmine > edrophonium 1.0 mg kg^–1 edrophonium+ pyridostigmine > edrophonium 0.5 mg kg^–1.     

NEOSTIGMINE AND EDROPHONIUM ANTAGONISM OF MODERATE NEUROMUSCULAR BLOCK INDUCED BY PANCURONIUM OR TUBOCURARINE

Edrophonium and neostigmine are anticholin-esterase drugs usedcommonly to antagonize competitive neuromuscular block. Althoughit has a faster onset of action than neostigmine, edrophoniumis unreliable when used to antagonize deep neuromuscular block.We have compared the antagonist characteristics of these twodrugs when used to antagonize a moderate degree of pancuronium-or tubocurarine-induced neuromuscular block. Forty ASA I orII patients undergoing surgical procedures were allocated randomlyto receive either pancuronium 70 kg^-1 or tubo-curarine 0.5 mgkg^-1, and to receive either edrophonium 0.5 mg kg^-1 or neostigmine0.05 mg kgr^-1. Antagonism was attempted when the first responseto train-of-four (TOF) stimulation recovered spontaneously to25% of the control height. Neuromuscular function was monitoredusing the evoked integrated electromyogram of the first dorsalinterosseous muscle of the hand. Adequate recovery was definedas the achievement of a TOF ratio of 0.70 or greater. Only sevenof 20 patients who received edrophonium demonstrated adequaterecovery 30 min after antagonism. Under the conditions describedin this study, edrophonium 0.5 mg kg7 was less effective asan antagonist than neostigmine 0.05 mg kg^-1. (Br. J. Anaesth.1993; 70: 160–162)     

A comparison of edrophonium and neostigmine for the antagonism of atracurium-induced neuromuscular block

Edrophonium, 0.5 mg/kg, or neostigmine, 0.05 mg/kg, was administered to groups of 20 patients each, for antagonism of atracurium-induced block at varying degrees of spontaneous recovery. Neuromuscular block was studied using train-of-four (TOF) stimulation. Adequate reversal of neuromuscular block (TOF ratio of 0.7) was achieved in all patients given neostigmine but only in 13 of the 20 given edrophonium. The onset of action of edrophonium (23 sec) was significantly more rapid than that of neostigmine (40 sec), as was the time taken to attain a TOF ratio of 0.7 in those in whom adequate antagonism was achieved (68 sec for edrophonium and 246 sec for neostigmine). Five of the seven patients in the edrophonium group who failed to be reversed adequately had shown three or fewer twitches to a TOF stimulation. It is concluded that edrophonium in a dose of 0.5 mg/kg does not consistently antagonize neuromuscular blockade induced by atracurium, particularly if all four responses to a TOF stimulation are not elicited prior to antagonism of the block.     

DOSE-RESPONSE RELATIONSHIPS FOR EDROPHONIUM AND NEOSTIGMINE ANTAGONISM OF MIVACURIUM-INDUCED NEUROMUSCULAR BLOCK

We have studied the dose-response relationships for neostigmineand edrophonium during antagonism of neuromuscular block inducedby mivacurium chloride. Sixty-four ASA group I or II adultswere given mivacurium 0.15 mg kg^–1 during fentanyl-thiopentone-nitrousoxide-iso flurane anaesthesia. Train-of-four stimulation (TOF)was applied to the ulnar nerve every 10 s, and the force ofcontraction of the adductor pollicis muscle was recorded. Whenspontaneous recovery of first twitch height reached 10% of itsinitial control value, edrophonium 0.1, 0.2, 0.4, or 1 mg kg^–1or neostigmine 0.005, 0.01, 0.02, or 0.05 mg kg^–1 wasadministered by random allocation. Neuromuscular function inanother 16 subjects was allowed to recover spontaneously. Spontaneousrecovery from 90% mivacurium block to 95% twitch height andTOF ratio 0.75 occurred within 15 min. This study demonstratedthat the dose-response curves for these two drugs for antagonismof neuromuscular block (first twitch and train-of-four ratio)were parallel. The doses of neostigmine required to achieve50% (ED₅₀) and 70% (ED₇₀) recovery of the first twitch after10 min were 2 (1.5– 2.5) µg kg^–1 and 4.7 (4.1–5.4)µg kg^–1 (mean (95% confidence intervals)), respectively.Corresponding ED₅₀ and ED₇₀ values for edrophonium were 2.8(0.75–10.2) pg kg^–1 and 9.2 (3.6–23.6) µgkg^–1, respectively. These values corresponded to neostigmine:edrophonium potency ratios of 1.4 (0.4–2.4) and 1.95(0.9–2.9) for first twitch ED₅₀ and ED₇₀ height, respectively.The calculated doses producing 50% (ED₅₀ recovery of the TOFratio at 10 min were neostigmine 2.57 (1.8–3.6) µgkg^–1 and edrophonium 26.9 (14.6–49.6) pg kg^–1.These values corresponded to a potency ratio of 10.4 (0.7–20).(Br. J. Anaesth. 1993; 71: 709–714)     

ANTAGONISM OF ATRACURIUM-INDUCED NEUROMUSCULAR BLOCKADE BY NEOSTIGMINE OR EDROPHONIUM

Antagonism of atracurium-induced neuromuscular blockade by neostigmineor edrophonium has been studied using the tetanic (50 Hz) andtrain-of-four (2 Hz) or single twitch responses of the adductorpollicis muscle in 22 anaesthetized patients. A further ninepatients not given an anticholinesterase acted as a controlgroup. In two groups (six patients for each anticholinesterase)in whom antagonism was attempted at 95–98% blockade ofthe tetanic response, recovery of the tetanic response aftertwo or three doses of edrophonium 0.75 mg kg^–1 i.v. wasnot statistically different from that in the control group;recovery after two doses of neostigmine 2.5 mg i.v. was significantlyfaster (P < 0.001). Recovery of the single twitch responseafter antagonism with edrophonium, although longer than thatwith neostigmine (P < 0.01), was significantly shorter thanin the control group (P < 0.05). When edrophonium is givenat the commencement of recovery, the initial rapid antagonismof tetanic block is not sustained, whereas antagonism by neostigmineis more persistent and the recovery phase is significantly shortened.In a further two groups of patients (n = 5) given atracurium0.3 mg kg^–1 i.v. antagonism was not attempted until thepeak height of the tetanic contraction had reached approximately50% of the control value. It was found that recovery of thetetanic and train-of-four responses was significantly faster(P < 0.05–0.001) after antagonism with edrophonium0.75 mg kg^–1 i.v. than with neostigmine 2.5mg i.v. (approx.0.04 mg kg^–1). The train-of-four response recovered moreslowly than did the tetanic response after both agents (P <0.05–0.01). Department of Anaesthetics, University College Hospital, LondonWC1. ^*Clinical Investigation Department, Clinical and Applied researchDivision, The Wellcome Research Laboratories, Beckenham, Kent.     

ELECTRICAL AND MECHANICAL RESPONSES AFTER NEUROMUSCULAR BLOCKADE WITH VECURONIUM, AND SUBSEQUENT ANTAGONISM WITH NEOSTIGMINE OR EDROPHONIUM

Six unpremedicated patients who had given their informed consentwere given vecuronium 0.08 mg kg^–1 before elective surgery.Recovery from neuromuscular blockade was measured electricallyand mechanically. Neuromuscular blockade was antagonized 1 hafter the administration of vecuronium with two doses of neostigmine2.5 mg (three patients) or edrophonium 0.5 mg kg^–1 (threepatients). Although the onset of initial recovery was similar,subsequent recovery was faster when meassured electrically (EMG)than when measured mechanically. Recovery appeared to be fasterin younger patients. Reintroduction of neuromuscular blockadeoccurred after the second dose of neostigmine 2.5 mg, givento antagonize the block. This did not occur after either doseof edrophonium 0.5 mg kg^–1. ^*University College and Middlesex Hospitals, Mortimer Street,London W1 7PN. Department of Anesthesiology, U.C.L.A. Medical School, Los Angeles,U.S.A.     

ANTAGONISM OF VECURONIUM AND ATRACURIUM: COMPARISON OF NEOSTIGMINE AND EDROPHONIUM ADMINISTERED AT 5% TWITCH HEIGHT RECOVERY

In 39 healthy patients antagonism, by neostig-mine 0.07 mg kg^–1or edrophonium 0.8 mg kg^–1, of neuromuscular blockadeinduced by vecuronium or atracurium, was compared. Reversalwas attempted when the height of the single twitch (TH) hadrecovered spontaneously to 5% of the control value. The evokedresponses, initially single twitch, then train-of-four (TOF)were observed until the TOF ratio was 70%. Induced recoveryfrom TH 5% to 25% was shorter following edrophonium than followingneostigmine with both vecuronium (P < 0.05) and atracurium(P < 0.05). The recovery indices and times until TH was 75%of control and until the TOF ratio was 70% were not different.The time from a TH of 75% to a TOF ratio of 70% was shorterfollowing neostigmine than following edrophonium with both vecuronium(P < 0.01) and atracurium (P < 0.01). Edrophonium hada much more variable effect on vecuronium than on atracurium.These results show that although the onset of action of edrophoniumwas faster than that of neostigmine, this did not lead to afaster clinical recovery, and antagonism by edrophonium maybe delayed in a number of patients if vecuronium is the neuromuscularblocker.     

Antagonism of pancuronium and tubocurarine blocks by edrophonium or neostigmine: a comparative study

Edrophonium 0.5 and neostigmine 0.05 mg kg-1 were compared as antagonists of pancuronium and tubocurarine-induced neuromuscular blocks, at varying degrees of recovery, in groups of 20 patients each. Adequate antagonism was defined as attaining a sustained train-of-four (TOF) ratio of 0.7 or more. Administration of edrophonium was associated with a more rapid onset of action (17 s with both relaxants with edrophonium, and 31 s and 29 s with neostigmine with pancuronium and tubocurarine, respectively), and a shorter time to attain a TOF ratio of 0.7 (74 s and 48 s with edrophonium and 230 s and 293 s with neostigmine for pancuronium and tubocurarine blocks, respectively). However, whereas neostigmine administration provided adequate antagonism in all 20 patients given pancuronium and in 19 out of 20 patients given tubocurarine, edrophonium failed to achieve adequate antagonism in six patients after pancuronium and eight patients after tubocurarine. The majority of these patients had shown three or less responses to a TOF stimulation prior to antagonism. Two separate groups of 10 patients each with relatively deeper pancuronium or tubocurarine blocks (three or less responses to TOF stimulation) were given edrophonium in a dose of 1.0 mg kg-1. However, adequate antagonism even with this dose of edrophonium was attained in only two out of 10 patients given pancuronium and in five out of 10 patients given tubocurarine. It is concluded that edrophonium is unreliable for antagonism of relatively deep blocks by pancuronium or tubocurarine and that neostigmine is the preferred and more reliable antagonist.     

ANTAGONISM OF MODERATE DEGREES OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCK BY SMALL DOSES OF NEOSTIGMINE

We have studied the influence of a reduced dose of neostigmineon recovery from vecuroniuminduced neuromuscular block in 26adult patients, using electromyographic responses to train-of-four(TOF) stimulation. Neostigmine 10, 20 or 40 µg kg^–1was administered when the first response had recovered spontaneouslyto 5–10% or 40–50% of control. Antagonism was acceptedas adequate when the first response reached 90% of control andthe TOF ratio reached 0.7. At both degrees of spontaneous recovery,neostigmine 40 µg kg^–1 evoked the most rapid antagonism.Clinical recovery was satisfactory with no differences betweengroups. Block produced by neostigmine was not observed. Thepattern of recovery of the single response and the TOF ratiowas not altered by neostigmine in the range of doses studied.We suggest that the dose of neostigmine should not be reducedbelow 40 µ kg^–1, even when all responses of theTOF are present. ^* present address: Royal Perth Hospital, Western Australia     

ANTAGONISM OF INTENSE ATRACURIUM-INDUCED NEUROMUSCULAR BLOCK IN CHILDREN

Antagonism of intense neuromuscular block induced by atracurium0.5 mg kg^–1 was attempted in four groups of six childrenusing one of two doses of neostigmine (0.05 mg kg^–1 and0.1 mg kg^–1) or of edrophonium (0.5 mg kg^–1 and1.0 mg kg^–1) when the first twitch of the post-tetaniccount (PTC1) was 10% of control. For comparison with normalpractice, a fifth group received neostigmine 0.05 mg kg^–1when the first twitch of the train-of-four was 10% of control.Total recovery time from PTC1 10% to a train-of-four ratio of0.8 was not reduced by early administration of the anticholinesterases,compared with conventional administration of neostigmine atT1 10%. However, recovery from intense block was faster afterneostigmine than edrophonium (P < 0.01). Doubling the dosesof the anticholinesterases did not reduce the recovery timeand had the effect of increasing variability. We conclude thatthere is no clinical advantage in attempting to antagonize intenseneuromuscular block in children using normal or increased dosesof neostigmine or edrophonium.     

DETERMINANTS OF THE REVERSAL TIME OF COMPETITIVE NEUROMUSCULAR BLOCK BY ANTICHOLINESTERASES

We have assessed, in 200 patients, the determinants of the reversaltime of competitive neuromuscular block by anticholinesterasewhen alcuronium and atracurium neuromuscular block were antagonizedby neostigmine 0.04 and 0.08 mg kg^–1 and edrophonium 0.5and 1.0 mg kg^–1. A biexponential relationship was foundbetween the reversal time (time from injection of anticholinesteraseto a train-of-four ratio of 70%) and the degree of neuromuscularblock at reversal (all groups; F ratio, P < 0.05). Reversaltime was determined by two processes: direct antagonism by theanticholinesterase and spontaneous recovery of the neuromuscularblocking agent, with the latter becoming the major determinantat profound levels of neuromuscular block (0–10% of controltwitch height). Neostigmine, in the doses studied, appearedto have a higher "ceiling" of neuromuscular block which it completelyantagonized, although edrophonium had a more rapid onset ofaction. The reversal time for alcuronium became progressivelylonger relative to atracurium as neuromuscular block increasedbecause of the slower spontaneous recovery rate. Avoidance ofprofound neuromuscular block at the completion of surgery isrequired to ensure reliable antagonism of the block within 5–10min by an anticholinesterase. Neostigmine 0.08 mg kg^–1was found to be the most effective agent in antagonizing profoundneuromuscular block.     

INFUSION OF VECURONIUM ASSESSED BY TACTILE EVALUATION OF EVOKED THUMB TWITCH

In 15 patients (ASA I-II) undergoing intra-abdominal gynaecologicalsurgery, muscle paralysis for tracheal intubation and surgerywas achieved by a combined bolus and demand infusion of vecuronium.The initial loading dose of 67 µg kg^–1 and the rateof subsequent infusion were determined by evaluation of thetactile twitch response to train-of-four (TOF) stimulation ofthe ulnar nerve while the neuromuscular blockade obtained wasrecorded blindly for control on the contralateral arm. A maintenancedose of 4.9 mg h^–1 (2.0–7.6mg h^–1) produceda smooth course of blockade with minimum and maximum valuesof twitch height during infusion of 2% and 12%, respectively.A period of 15.9 min elapsed from the end of infusion to a TOF-ratioof 0.7, when neostigmine 2.5 mg was administered at the pointof two palpable twitches to TOF-stimulation. Simple tactileevaluation of peripheral nerve stimulation is sufficient todetermine the infusion rate of vecuronium required to producestable and appropriate neuromuscular blockade during intra-abdominalsurgery.     

Pharmacodynamics and pharmacokinetics of an infusion of Org 9487, a new short-acting steroidal neuromuscular blocking agent

We have evaluated in 10 anaesthetized patients the time courseof action, infusion requirements, reversibility and pharmacokineticsof Org 9487. Org 9487 was administered as a bolus dose of 1.5mg kg^–1 followed by an infusion to maintain a block of75–85% for 60 min. After recovery from the bolus dose,a mean dose of Org 9487 3.4 (SD 1.0) mg kg^–1 h^–1was administered to maintain a mean neuromuscular block of 83(3)%. During the final 15 min of infusion, the infusion requirementswere 2.5 (1.1) mg kg^–1 h^–1 In the five patientswho were allowed to recover spontaneously, a TOF ratio of 0.7was reached 37.9 (12.4) min after stopping the infusion of Org9487. In the five patients who received neostigmine, a TOF ratioof 0.7 was reached after 14.5 (6.1) min. Plasma clearance was8.5 (30%) ml kg^–1 min^–1. Volume of distributionat steady state was 293 (55%) ml kg^–1 Terminal half lifeand mean residence time were 71.7 (34%) and 33.4 (31%) min,respectively. The concentration of the 3-OH metabolite remainedrelatively low. Urinary excretion of Org 9487 and its metaboliteswas 22% in 24 h. In conclusion, a 1-h infusion of the short-actingdrug Org 9487 changed its time course characteristics graduallyfrom that of a short-acting neuromuscular blocking agent tothat of a neuromuscular blocker with an intermediate durationof action.     

ANTAGONISM OF PROFOUND NEUROMUSCULAR BLOCKADE INDUCED BY VECURONIUM OR ATRACURIUM: Comparison of Neostigmine with Edrophonium

The effectiveness of neostigmine 0.07mg kg^–1 and edrophonium0.8 mg kg^–1 as antagonists of profound neuromuscular blockadeinduced by vecuronium 0.1 mg kg^–1 or atracurium 0.5 mgkg^–1 was studied in 59 healthy patients. The antagonistswere administered 5 min after total ablation of the twitch responseand the end-point of recovery was a train-of-four ratio of 70%.In 30 patients given vecuronium the mean time to reach thispoint (duration TOF₇₀) was 66.7min in the control group (noantagonist), 43.5 min in the group given neostigmine and 59.8min in the group given edrophonium. The duration TOF₇₀ was shorterin the neostigmine group than in the control {P < 0.01) andedrophonium (P<0.01) groups. The duration TOF₇₀ did not differfrom control in the edrophonium group. In 29 patients givenatracurium, the durations TOF₇₀ were 66.4, 44.1 and 54.9 minin the control, neostigmine and edrophonium groups, respectively.The durations TOF₇₀ in the neostigmine (P < 0.01) and edrophonium(P < 0.01), groups were shorter than control. The durationTOF₇₀ of the neostigmine group was shorter than in the edrophoniumgroup (P < 0.01). These results show that pro-found neuromuscularblockade cannot be rapidly antagonized by either of these twoagents, but if reversal is required under these circumstances,neostigmine would be the more effective drug. ^*The initial results from the vecuronium group were presentedat the 4th Ludwig Boltzmann Symposium, Vienna, 1984.     

COMPARISON OF THE TRAIN-OF-FOUR FADE PROFILES PRODUCED BY VECURONIUM AND ATRACURIUM

In this double-blind study, we have allocated randomly 40 ASAI-III patients to one of four groups. After a standard anaestheticinduction, patients received vecuronium 0.08 mg kg^–1 or0.10 mg kg^–1, or atracurium 0.4 mg kg^–1 or 0.5 mgkg^–1. Using an electromyogram (Datex Relaxograph) thetrain-of-four (TOF) response was measured during onset of andrecovery from neuromuscular block. A greater degree of fadeof TOF was observed with atracurium during onset of neuromuscularblock than with equivalent doses of vecuronium. During recoveryof neuromuscular transmission, vecuronium was associated withmore fade than atracurium. The differences in the TOF profilesof these two drugs may be important when judging the adequacyof antagonism of neuromuscular block using the TOF response.     

Antagonism of mivacurium block with edrophonium from various degrees of spontaneous recovery

Seventy adult patients received mivacurium 0.15 mg kg^–1during anaesthesia with thiopentone, nitrous oxide and 0.5%halothane. Neuromuscular block was monitored using mechanomyographyand train-of-four stimulation. Edrophonium 0.75 mg kg^–1was administered 5 or 10 min after mivacurium, or when the firstresponse in the TOF (T1) had recovered to 5, 10, 25 or 50% ofcontrol in groups of 10 patients each. A control group was allowedto recover spontaneously. The mean time taken from administrationof mivacurium to attaining a TOF ratio of 0.7 was between 19.3and 24.9 min in the groups given edrophonium, regardless ofthe time of administration, compared with 26.7 min in the spontaneousrecovery group. The differences, however, were not significantamong the groups showing little advantage in antagonizing mivacuriumblock.     

DOSE-RESPONSE RELATIONSHIPS FOR NEOSTIGMINE ANTAGONISM OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCK IN ADULTS AND THE ELDERLY

We have studied the dose-response relationship for neostigminein 36 adult (ages 18-50 yr) and 36 elderly (ages > 70 yr)subjects during antagonism of neuromuscular block induced byvecuronium. All patients received vecuronium 0.08 mg kg^–1and neuromuscular block was monitoredmechanomyo-graphicallyusing the train-of-four (TOF) mode of stimulation. Six patientsof each age group were allocated randomly to receive neostigmine5, 15, 25, 35 or 45 µg kg^–1 or saline at 10% recoveryof T1 (first response in the TOF). TOF ratios were recordedcontinuously over the next 10 min and the values at 1-min intervalsfrom 5 min onwards were used to construct the dose-responserelationships. There was a significant difference (P < 0,05)in the time to spontaneous recovery of T1 to 10% between theadults (24 (SD 5.5) min) and the elderly (33 (7.8) min). Dose-responsecurves for neostigmine were parallel in the two age groups,but those for the. elderly were significantly to the right ofthe curves for the adults. This sggests an apparently lesserrelative potency of neostigmine, or the requirement of a largerdose, in the elderly for attaining antagonism of a moderatelyintense vecuronium block at the same time as in adults.     

EFFECTS OF NEOSTIGMINE AND EDROPHONIUM ON HUMAN ERYTHROCYTE ACETYLCHOLINESTERASE ACTIVITY

Erythrocyte acetylcholinesterase (AChE) activities in vivo weremeasured over 60 min using a spectrophotometric method afteradministration of neostigmine or edrophonium for antagonismof pancuronium-induced neuromuscular block in 31 patients. ErythrocyteAChE activities decreased to 11.3 (SD 1.2) % and 11.4 (0.8)% of baseline values (P < 0.001) within 2 min, then recoveredslowly and were 43.2 (6.2) % and 27.9 (2.9) % (P < 0.001)60 min after administration of neostigmine 0.036 mg kg^–1and 0.071 mg kg^–1, respectively. However, the enzyme activityafter edrophonium 1.43 mg kg^–1 did not change significantlyover 60 min. The results suggest that mechanisms other thanAChE inhibition may be responsible for the anti- curare effectof edrophonium     

Neostigmine and edrophonium as antagonists of atracurium and pancuronium

Edrophonium 0.5 mg/kg or neostigmine 0.04 mg/kg were administered to two groups of 30 patients each for antagonism of atracurium- or pancuronium-induced neuromuscular block at 25% single twitch recovery. Neuromuscular block was studied using both single twitch and train-of-four (TOF) nerve stimulation. The times to 100% single twitch recovery were significantly more rapid for patients receiving edrophonium (P less than 0.01) in both groups (atracurium and pancuronium); the TOF ratios were similar for atracurium, but for pancuronium they were greater after neostigmine than after edrophonium, and only at 25 min were these ratios similar. It is concluded that edrophonium in a dose of 0.5 mg/kg antagonizes neuromuscular blockade induced by atracurium, as does neostigmine in a dose of 0.04 mg/kg, but the former does not consistently antagonize neuromuscular blockade induced by pancuronium even at 25% of single twitch recovery.     

RECOVERY FROM PANCURONIUM BLOCKADE IN THE NEONATAL INTENSIVE CARE UNIT

Neuromuscular blockade with pancuronium and its antagonism wasevaluated in 33 critically ill infants. The evoked contractionof the adductor pollicis from indirect stimulation of the ulnarnerve was measured. The neuromuscular blockade recovered spontaneouslyfrom pancuronium in seven infants, 23 required one or more dosesof atropine 0.02 ng kg^–1 and neostigmine 0.06mg kg^–1.In three infants the blockade railed to reverse. Immature infantsless than 32 weeks did not show any significant difference intheir requirement for pancuronium compared with mature infants.Age and birth weight of the infant, dose of pancuronium andduration of its administration did not affect the requirementsfor reversal. Train-of-four and tetanus:twitch ratios were lower(P<0.05) in infants less than 32 weeks of developmental agereflecting immaturity of neuromuscular transmission.