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Biomedical subjects

E P McCoy

Publications and source records attributed to E P McCoy.

At least 19 recordsLinked to original sources
PubMed2006

A serious and repeatable electrical hazard--compressed electrical cord and an operating table.

We describe a previously unreported hazard resulting from compression of an electrical cable by an operating theatre table. This resulted in a live wire contact to the operating table. Intermittent connection of the table to earth during a procedure resulted in triggering of a residual current device mitigating the effects of the hazard. The actual cause was not readily identified as the devices connecting the table to earth were considered most likely to be the source of the current. There was potential for significant injury to the patient and theatre staff which would have been diminished if staff had had a better understanding of the electrical safety equipment in use. We examine the underlying causes of the accident, discuss electrical safety and correct use of safety devices in the operating theatre, and propose guidelines for appropriate management.

Aged↗
PubMed1997

Accidental bronchial intubation. An analysis of AIMS incident reports from 1988 to 1994 inclusive.

Accidental bronchial intubation was examined in the first 3947 cases reported to the Australian Incident Monitoring Study and was found to have accounted for 154 (3.7%) of the total incidents reported. Most incidents were detected in the operating theatre (93.5%) and during maintenance of anaesthesia (77.9%), by unexplained oxygen desaturation alone (63.6%). Capnography remained normal or unremarkable during 88.5% of the episodes. One-third of cases were associated with head or neck surgery and possible flexion of the patient's head. A RAE tube was used in 20% of incidents, a greater frequency than occurred in the study overall. A third party was implicated in 36 (23.4%) of cases. Ninety per cent of cases were considered preventable. Major morbidity occurred in three cases and unplanned intensive care admission was required in a further five. Almost two-thirds (61.1%) of the incidents might have been avoided by the proposed markings on the tracheal tube. We conclude that when arterial desaturation occurs at any stage during anaesthesia the possibility of bronchial intubation must be considered. Asymmetrical ventilation may be difficult to detect clinically and in most cases there is no change in capnography.

Australia↗
PubMed1996

Duration of stabilization of control responses affects the onset and duration of action of rocuronium but not suxamethonium.

The effect of the duration of stabilization of control responses on the onset and duration of clinical relaxation of suxamethonium 1 mg kg-1 and rocuronium 0.6 mg kg-1 were investigated in 90 patients. The control responses were allowed to stabilize for 1, 5, 10, 15 or 20 min prior to administration of rocuronium and for 1, 5, 10 or 15 min prior to suxamethonium. The mean onset time for rocuronium decreased from 150 to 46 s as the duration of stabilization increased from 1 to 20 min (P < 0.001) although the maximal effect was observed within the first 5 min. The average duration of clinical relaxation also increased from 25 to 40 min (P < 0.001). No effect was observed for either variable in the case of suxamethonium.

Adolescent↗
PubMed1996

Pharmacokinetics of rocuronium after bolus and continuous infusion during halothane anaesthesia.

We have studied the pharmacokinetics of a single bolus of rocuronium (Org 9426), followed by an infusion, in eight patients during anaesthesia with halothane and nitrous oxide in oxygen. Neuromuscular block was monitored using train-of-four (TOF) stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered as an initial bolus dose of 0.45 mg kg-1 followed by an infusion adjusted manually to maintain T1 (first response in the TOF) at 10% of control. Mean onset time and time to recovery of T1 to 10% were 72 (SD 19.6) s and 27 (9.6) min, respectively. The infusion rates were stable in 19.8 (6.5) min. The mean requirement for rocuronium for steady state 90% block of T1 was 528 (163.3) micrograms kg-1 h-1. After cessation of surgery the infusion was stopped and patients were allowed to recover spontaneously. The times to attain a T1 of 90% and a TOF ratio of 0.7 were 31 (11.7) min and 36 (7.3) min, respectively. Blood samples were collected for 390 min after cessation of infusion and concentrations of rocuronium and its putative metabolites measured using HPLC. A two-exponential equation was used to describe the pharmacokinetic data. The rate of clearance, mean residence time and volume of distribution at steady state were 3.3 (0.77) ml kg-1 min-1, 67.2 (18.8) min and 212.5 (40.1) ml kg-1, respectively. The distribution (T1/2 alpha) and elimination (T1/2 beta) half-lives were 7.5 (3.33) min and 85.6 (18.4) min, respectively. These values were not significantly different from previously published data for a single bolus dose of rocuronium.

Adolescent↗
PubMed1996

A comparison of the forces exerted during laryngoscopy. The Macintosh versus the McCoy blade.

The forces exerted at laryngoscopy with the McCoy and Macintosh blades have been compared in 40 patients. The variables measured were the duration of laryngoscopy, the three maximally-applied forces and the mean force. The mean (SD) forces recorded were 18.9 (7.82) and 10.1 (5.33) N, respectively, with the Macintosh and the McCoy blades (p < 0.001) with a similar duration of laryngoscopy. There was a significant positive correlation between the mean force and patients' weight, height and body mass index for the Macintosh blade but only for weight and height for the McCoy blade. It is concluded that the use of the McCoy blade results in significantly less force being applied during laryngoscopy. This may be the reason for the reduction in the stress response reported previously with the use of the McCoy blade.

Adolescent↗
PubMed1995

Nondepolarizing neuromuscular blocking drugs and train-of-four fade.

The aim of this study was to examine differences in prejunctional effects of different relaxants by measuring the train-of-four (TOF) fade during the onset and recovery of neuromuscular block. The relaxants studied were atracurium (225 micrograms.kg-1), mivacurium (65 micrograms.kg-1) rocuronium (300 micrograms.kg-1) and vecuronium (40 micrograms.kg-1). The TOF ratios were measured at approximate heights of T1 (first response in the TOF) of 90, 75, 50, and 25%. The TOF fade (as shown by lower TOF ratios) increased with a decrease in the T1 during onset of neuromuscular block. Although there was a slightly greater fade with atracurium and rocuronium during the onset of block, the differences among the relaxants were insignificant. It is concluded that the relative prejunctional effects of these relaxants are similar.

Adult↗
PubMed1995

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

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

Adult↗
PubMed1995

The influence of the duration of control stimulation on the onset and recovery of neuromuscular block.

The onset of action of atracurium 450 micrograms/kg, mivacurium 160 micrograms/kg, and vecuronium 80 micrograms/kg was measured after train-of-four (TOF) stimulation had been applied for 1, 5, 10, 15, or 20 min in groups of 10 patients each during anesthesia with thiopental, nitrous oxide-oxygen, and fentanyl. TOF stimulation was applied to the ulnar nerve at 2 Hz every 12 s and the force of contraction of the adductor pollicis muscle recorded. There was a progressive and significant reduction in the time to onset of maximum block with increasing times of control stimulation with all three relaxants (P < 0.0001). The mean +/- SD times to onset of maximum block decreased from 224 +/- 103 to 73 +/- 28 s with atracurium, 239 +/- 81 to 101 +/- 33 s with vecuronium, and 198 +/- 72 to 106 +/- 23 s with mivacurium as the period of control stimulation increased from 1 to 20 min. The time to recovery of T1 (first response in the TOF stimulation) to 25% of control (duration of clinical relaxation) increased from 33 +/- 5.7 to 52 +/- 13.4 min with atracurium, 25 +/- 7.6 to 38 +/- 9.4 min with vecuronium, and 13 +/- 2.5 to 18 +/- 3.5 min with mivacurium with the period of control stimulation increasing from 1 to 20 min. The differences were significant for atracurium and vecuronium (P < 0.05-0.0001). We conclude that increasing periods of control stimulation are associated with decreasing time to onset of neuromuscular block with atracurium, vecuronium, and mivacurium at the adductor pollicis muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade.

The cardiovascular changes and catecholamine concentrations were compared in 20 patients before and after laryngoscopy with either the Macintosh or the McCoy laryngoscope blades. Following induction with fentanyl and thiopentone and muscle relaxation with vecuronium the vocal cords were visualised for 10 s with either the Macintosh or McCoy blade, chosen at random. Heart rate, arterial blood pressure and plasma noradrenaline and adrenaline concentrations were measured before, and at, laryngoscopy, and 1, 3 and 5 min later. There was a significant increase in both heart rate (33%) and arterial blood pressure (27%) after laryngoscopy using the Macintosh blade (p < 0.01). Use of the McCoy blade did not result in any significant change in either heart rate or arterial blood pressure. There was a slight increase (p > 0.05) in plasma noradrenaline concentrations using the Macintosh blade which persisted for 5 min after laryngoscopy. This was not observed with the McCoy blade. There was no change in plasma adrenaline concentrations with either blade during the 5 min after laryngoscopy when compared to the values before laryngoscopy. It is concluded that the stress response to laryngoscopy is less marked with the use of the McCoy blade and is probably due to a reduction in the force necessary to obtain a clear view of the larynx.

Adolescent↗
PubMed1995

Dose-responses for edrophonium during antagonism of vecuronium block in young and older adult patients.

The dose-response relationship for edrophonium during antagonism of vecuronium-induced neuromuscular blockade was studied in two groups of adult patients of mean (SD) age 35 (10.0) years (n = 42) and 77 (5.4) years (n = 42) respectively. Neuromuscular block was monitored by recording the force of contraction of the adductor pollicis muscle following train-of-four stimulation. Six patients in each age group received 0.1, 0.3, 0.5, 0.7, 1.0, or 1.5 mg.kg-1 of edrophonium, or normal saline at 10% recovery of T1 (first response in the train-of-four) after a single dose of vecuronium 0.08 mg.kg-1. The train-of-four ratios were recorded continuously over the next 10 min and the values at 1 min intervals from 5 min onwards were used to construct the dose-response curves. The dose-response curves showed no significant difference between the two age groups except at 10 min. The estimated dose of edrophonium required for attaining a train-of-four ratio of 0.7 at 10 min was 0.9 and 1.3 mg.kg-1 in the younger and older groups, respectively (p < 0.05).

Adolescent↗
PubMed1995

The TOF-Guard neuromuscular transmission monitor. A comparison with the Myograph 2000.

The TOF-Guard neuromuscular monitor uses an accelerometer to measure the response to nerve stimulation. In this study, we have compared it to a standard mechanomyographic monitor, the Myograph 2000, for neuromuscular monitoring in 28 subjects. A train-of-four mode of stimulation was used in both cases. The times taken for onset of block, and for the recovery of T1 (the first response in the train of four) to 25% of control, the time from recovery of T1 from 25-75% and for the recovery of the train of four ratio to 0.7 were compared with the two monitors. There was a good correlation between the two devices for both onset and recovery times. However, differences were highlighted when the data were analysed by the method of Bland and Altman. The 95% limits of agreement for the T1 recovery to 25%, as measured by the TOF-Guard, ranged from 5 min less to 8 min more than when measured by the Myograph 2000. For recovery of the train of four ratio to 0.7, the limits of agreement were approximately 6 min in either direction. The 95% limits for the TOF-Guard measured train of four ratio were from 0.47 to 0.99, at the Myograph reading of 0.7. We recommend that information from the TOF-Guard and the Myograph 2000 should not be used interchangeably. However, the TOF-Guard is likely to improve considerably on tactile evaluation of the responses to stimulation.

Anesthesiology↗
PubMed1995

A new device for measuring and recording the forces applied during laryngoscopy.

In characterising the forces exerted during laryngoscopy it is accepted that the significant force component is that which is parallel to the axis of the laryngoscope handle. This paper describes a new method of evaluating the forces exerted at laryngoscopy. A laryngoscope handle has been redesigned, incorporating a force-displacement transducer on the handle at the end opposite to where the blade is attached. The device is designed specifically to sense the axial component of force. The blade attachment block has been detached from the sleeve and connected to a steel shaft which forms the new battery compartment. This allows the axial force exerted at the blade during laryngoscopy to be transmitted along this shaft to the sensing transducer. Linear ball bearings have been introduced between the new shaft and the handle sleeve (outer casing). The rolling friction has been reduced to less than 0.1% by diamond-lapping the precision ground surface-hardened rod to produce a mirror finish. Thus, the force transmitted to the transducer is essentially constant regardless of where the load is applied along the blade. The output from the system is directly downloaded to a laptop computer and the data analysed almost instantaneously to determine the duration of laryngoscopy, the peak forces applied, the mean force with its standard deviation and graphic display of the data. Provision has been made for data entry checks, recording patient details and study data, and creating a data base for the storage and retrieval of the study details.

Adult↗
PubMed1995

Comparison of the effects of neostigmine and edrophonium on the duration of action of suxamethonium.

Rapid sequence induction of anaesthesia necessitating the use of suxamethonium may occasionally be needed soon after antagonism of neuromuscular block with anticholinesterase agents. The onset and duration of action of 1 mg kg-1 of suxamethonium was recorded in groups of 10 patients each, 5 or 10 min after the administration of edrophonium 1 mg kg-1 or neostigmine 40 micrograms kg-1 given for the antagonism of atracurium-induced neuromuscular block. Plasma cholinesterase activity was measured before, and 5 and 10 min after the administration of the anticholinesterases. A further 10 patients received suxamethonium 1 mg kg-1 without prior atracurium or anticholinesterase administration to serve as controls. The onset of action of suxamethonium was significantly prolonged when administered 5 min after both anticholinesterases, compared to the control group (P < 0.01). Recovery of suxamethonium block was delayed significantly after neostigmine, compared to both the edrophonium and the control groups (P < 0.05-0.001). Plasma cholinesterase activity was significantly reduced with the use of neostigmine but not with edrophonium (P < 0.001).

Adult↗
PubMed1994

Neuromuscular and haemodynamic effects of mivacurium in elderly and young adult patients.

We have studied the neuromuscular effects of mivacurium and changes in heart rate and arterial pressure in 40 elderly (aged 70 yr) and 20 young adult (aged 18-40 yr) patients anaesthetized with thiopentone, fentanyl, nitrous oxide in oxygen and halothane. Neuromuscular block was monitored by train-of-four (TOF) stimulation of the ulnar nerve and recording of the force of contraction of the adductor pollicis muscle using a force displacement transducer and a neuromuscular function analyser (Myograph 2000, Biometer Ltd). Twenty elderly and 10 young adults received single doses of mivacurium 0.15 mg kg-1 and spontaneous recovery was recorded. The other 20 elderly and 10 adults received the same dose but an infusion was started at T1 (first response in TOF) of 10% and the block maintained at this level. Haemodynamic effects were studied after administration of mivacurium over 15 or 5 s in elderly (n = 10 each) and over 5 s in adult (n = 10) patients. Onset of maximum block occurred at a mean time of 122 (SD 32) and 125 (49) s in elderly and young adults, respectively. Recovery of T1 to 25% occurred in 22.0 (5.7) and 17.2 (4.4) min, and T1 to 90% in 32.8 (6.9) and 24.4 (5.8) min in elderly and adult subjects, respectively. Recovery of the TOF ratio to 0.7 occurred in 32.8 (7.1) and 26.0 (15.0) min in the elderly and young subjects, respectively (all P < 0.05 between young and elderly).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Administration of rocuronium (Org 9426) by continuous infusion and its reversibility with anticholinesterases.

The use of rocuronium (Org 9426) as a single bolus followed by an infusion was assessed in 50 patients under anaesthesia with nitrous oxide-oxygen and halothane. Neuromuscular block was monitored using train-of-four stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered in an initial bolus dose of 0.45 mg.kg-1 followed by an infusion adjusted manually to maintain the T1, the first response in the train-of-four, at 10% of control. Following cessation of rocuronium infusion the patients were either allowed to recover spontaneously (n = 10) or were given neostigmine 50 micrograms.kg-1 or edrophonium 1 mg.kg-1 at 10 or 25% recovery of the T1 (n = 10 for each group). Adequate antagonism was defined as attaining a sustained train-of-four ratio of 0.7. Rocuronium requirements showed marked variation among individual patients but were relatively constant in individual patients. The mean (SD) time to attain stable infusion rates was 17.4 (10.9) min. The mean (SD) requirement of rocuronium for steady state 90% block of T1 was 572 (190) micrograms.kg-1.h-1 (range 242-1104 micrograms.kg-1.h-1). The mean (SD) time to attain a train-of-four ratio of 0.7 in the group allowed to recover spontaneously was 36.1 (7.3) min. This interval was 7.5 (1.9), 9.3 (7.0), 4.6 (1.9) and 1.9 (0.9) min respectively in the groups receiving neostigmine at T1 of 10%, edrophonium at T1 of 10%, neostigmine at T1 of 25% and edrophonium at T1 of 25%. The antagonism was significantly faster in those reversed at 25% (p < 0.05). Three patients in the group receiving edrophonium at T1 of 10% and one in the group receiving neostigmine at T1 of 25% failed to attain a train-of-four ratio of 0.7. It is concluded that rocuronium can be administered as a continuous infusion for stable neuromuscular block. Neostigmine may be a more reliable antagonist of deep block, whereas edrophonium is advantageous when there is a greater spontaneous recovery.

Adult↗