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Biomedical subjects

A F Kopman

Publications and source records attributed to A F Kopman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Relationship of the train-of-four fade ratio to clinical signs and symptoms of residual paralysis in awake volunteers.

BACKGROUND: Recovery of the train-of-four (TOF) ratio to a value > 0.70 is synonymous with adequate return of neuromuscular function, but there is little information available concerning the subjective experience that accompanies residual neuromuscular block wherein the TOF ratio is in the range of 0.70 to 0.90. METHODS: Ten American Society of Anesthesiologists' (ASA) physical status 1 volunteers were studied. Control measurements including grip strength in kilograms and ability to perform a 5-s head- and leg-lift. In addition, a standard wooden tongue depressor was placed between each subject's incisor teeth, and he or she was told not to let the investigator remove it. All subjects were easily able to retain the device despite vigorous attempts to dislodge it. Neuromuscular function was monitored with a Datex (Datex Medical Instrumentation, Inc., Tewksbury, MA) 221 electromyographic (EMG) monitor. TOF stimulation was given every 20 s, and the measured TOF fade ratio was continuously recorded. A 5 mg/kg bolus of mivacurium was then administered, and an infusion at 2 mg.kg-1.min-1 was begun. The infusion was continued until the TOF ratio decreased to < 0.70 and was adjusted to keep it in the range of 0.65 to 0.75. Signs and symptoms of weakness were recorded when the TOF ratio had been stable +/-0.03 for at least 10 min during an interval when there were no adjustments in the infusion. All tests noted previously were repeated at this time. The TOF ratio was then allowed to recover to 0.85-0.90. When stable at this level, all tests were repeated, and the infusion was discontinued. TOF measurements were continued until a ratio of 1.0 was attained and until a final set of observations was recorded. RESULTS: The TOF ratio in all subjects was reduced to < 0.70. No volunteers required intervention to maintain a patient airway, and the hemoglobin oxygen saturation while breathing air was > or = 96% at all times. TOF ratios < or = 0.90 were accompanied by diplopia and difficulty in tracking moving objects in all subjects. The ability to strongly oppose the incisor teeth did not return until the TOF ratio (on average) exceeded 0.85. A sustained 5-s head-lift was not achieved until the TOF ratio averaged 0.60 (range, 0.45-0.75). At a TOF ratio of 0.70, grip strength averaged 59% of control (range, 50-75%). With certain exceptions (vision, ability to clench the teeth tightly), there was wide variation in symptomatology between patients for any given TOF ratio. It is impossible to give reliable TOF break-points at which symptoms and signs will be present or absent. CONCLUSIONS: All subjects had significant signs and symptoms of residual block at a TOF ratio of 0.70; none considered themselves remotely "street ready" at this time. The authors believe that satisfactory recovery of neuromuscular function after mivacurium-induced neuromuscular block requires return of the TOF ratio to a value > 0.90 and ideally to unity.

Adult↗
PubMed1996

Residual postoperative paralysis. Pancuronium versus mivacurium, does it matter?

BACKGROUND: Based on a train-of-four (TOF) ratio greater than 0.70 as the standard of acceptable clinical recovery, undetected postoperative residual paralysis occurs frequently in postanesthesia care units. In most published studies, detailed information regarding anesthetic management is not provided. The authors reexamined the incidence of postoperative weakness after the administration of long- and short-acting neuromuscular blockers because few, if any, such comparative studies are available. METHODS: Ninety-one adult patients were studied. In group 1 (mivacurium, n = 35), anesthesia was induced with propofol/ fentanyl and maintained with nitrous oxide, desflurane, and opioid supplementation. The response of the adductor pollicis to ulnar nerve stimulation was estimated by palpating the thumb. Mivacurium (0.20 mg/kg) was administered for tracheal intubation, and an infusion was adjusted to maintain the TOF count at 1. When surgery was completed, the infusion was discontinued. When a second twitch could be detected, 7.0 micrograms/kg atropine and then 0.5 mg/kg edrophonium were administered. At 5 and 10 min, the mechanical TOF response was measured. Additional measurements were recorded if possible. Patients were tracheally extubated and discharged from the operating room when they could respond to verbal commands and no TOF fade was palpable. In group 2 (pancuronium-desflurane anesthesia, n = 29), the protocol was identical to that of group 1, except that 0.07 mg/kg pancuronium was administered for tracheal intubation. Additional increments (0.5 to 1 mg) were given as needed. Antagonism was accomplished with 0.05 mg/kg neostigmine and 0.01 mg/kg glycopyrrolate. In group 3 (pancuronium propofol-opioid, n = 27), the protocol was identical to that of group 2, except that anesthesia was maintained with nitrous oxide and a propofol-alfentanil infusion. In all groups, patients were assessed until a TOF ratio of 0.90 or more was achieved. RESULTS: All of the patients in group 1 had TOF ratios greater than 0.80 on arrival in the postanesthesia care unit. Twenty of 35 patients had TOF ratios 0.90 or more while they were still in the operating room. Thirty-three of 35 patients had TOF ratios 0.90 or more within 30 min of reversal, and this value was reached in all patients by 45 min. Recovery parameters in groups 2 and 3 did not differ from each other. Hence data from these groups were pooled. Fifty-four of 56 patients who received pancuronium had TOF values of 0.70 or more, the remaining two patients had values of 0.6 to 0.7. In contrast to the mivacurium group, however, only four patients achieved a TOF ratio of 0.90 or greater while still in the operating room. Finally, eight of these patients did not achieve this degree of recovery within 90 min of reversal. CONCLUSIONS: These results suggest that if nondepolarizing neuromuscular blockers are administered using tactile evaluation of the TOF count as a guide, critical episodes of postoperative weakness in the postanesthesia care unit should occur infrequently even with long-acting relaxants. Nevertheless, if full recovery is defined as return to a TOF ratio of 0.90 or more, then short-acting agents would appear to offer a wider margin of safety.

Adult↗
PubMed1996

Re-establishment of paralysis using mivacurium following apparent full recovery from mivacurium-induced neuromuscular block.

Recent published data suggest that despite apparently satisfactory recovery from nondepolarising block (train-of-four ratios in excess of 0.90), even very small doses of additional relaxant may re-establish significant paralysis. We sought to verify this observation and quantify its magnitude. Twelve adult patients were studied under nitrous oxide-propofol-opioid anaesthesia and neuromuscular block was monitored electromyographically. Train-of-four stimuli were delivered to the ulnar nerve every 20 s throughout the period of observation. After baseline stabilisation, an initial bolus of mivacurium 25 micrograms.kg-1 was administered and the twitch depression noted. When the twitch was stable for two consecutive stimuli, a second bolus, calculated to produce approximately 90% twitch depression, was administered. Recovery was then allowed to proceed spontaneously until the train-of-four ratio reached 0.95. At that time a second 25 micrograms.kg-1 dose was administered and the effect on twitch height recorded. Using the slope for the log-dose/logit dose-response relationship of mivacurium (5.5), it was possible to estimate any change in the ED50 of mivacurium. The control ED50 of mivacurium (calculated from the initial dose of mivacurium) averaged 43 micrograms.kg-1. When the same dose of drug was given at 95% recovery of the train-of-four ratio, the ED50 was reduced to 19 micrograms.kg-1 (p < 0.0001). Hence, there remains a considerable reduction in the neuromuscular margin of safety even at a train-of-four ratio of 0.95.

Adolescent↗
PubMed1995

The influence of changes in hand temperature on the indirectly evoked electromyogram of the first dorsal interosseous muscle.

The evoked EMG response commonly decreases in amplitude during the first few minutes of anaesthesia. The purpose of this study was to determine if a relationship exists between changes in hand temperature, which are known to occur with induction of anaesthesia, and drift in the EMG signal. The indirectly evoked response of the 1st dorsal interosseous muscle was measured using a Datex Relaxograph in 15 patients undergoing elective surgery. The test arm was wrapped in towels in order to minimize heat loss. Core body temperature, hand temperature, and T1 were recorded at two minute intervals for the next 30 min. Patients then received a bolus of mivacurium 0.08 mg.kg-1 and additional doses were given as needed. Complete recovery was defined as a TOF ratio > 0.90. Regression analysis plotting delta temperature against delta T1 was performed for each individual. The slope of the regression line for the relationship between delta degree C and delta T1 was then used to calculate a correction factor (CF) which might be used to "fine tune" the last measured T1. The initial hand temperature averaged 30.8 +/- 1.4 degrees C and this increased by 4.1 +/- 1.2 degrees C over the next 30 min. During this period T1 decreased by 24.8 +/- 5.9% or -6.05%/degrees C. The final mean T1 value at the end of anaesthesia (uncorrected) was 70.6 +/- 7% of control. The average corrected T1 value was 94.7 +/- 8.5% (range, 83-111%). It is concluded that there was a correlation between delta degree C and delta T1 during the first 30 min of anaesthesia (r2 = 0.77, P < 0.0001). However, in 5 of 15 individuals it was not possible to "temperature correct" the final T1 value to within +/- 10% of control. Hence, while changes in muscle temperature probably play a major role in the T1 drift seen with the Datex monitor, other factors remain to be identified.

Adolescent↗
PubMed1994

Antagonism of mivacurium-induced neuromuscular blockade in humans. Edrophonium dose requirements at threshold train-of-four count of 4.

BACKGROUND: Mivacurium's rapid rate of recovery has led to the suggestion that routine reversal of its residual effects may be unnecessary once signs of spontaneous recovery are evident. When antagonism is attempted at 90% twitch depression, the time saved to return to train-of-four (TOF) ratios > 0.70 compared to control has been reported to average < or = 8 min. This study was an attempt to determine whether similar savings in time could be achieved once spontaneous recovery was well underway. Also investigated was the ability of a TOF count of 4 to serve as a marker that might predict the dose of edrophonium necessary for satisfactory antagonism of mivacurium. METHODS: Fifty-eight adult patients were studied under nitrous oxide/propofol/opioid anesthesia. Neuromuscular block was monitored electromyographically and maintained by infusion of mivacurium at a level sufficient to abolish any palpable response of the thumb. TOF stimuli were delivered to the ulnar nerve at the wrist every 20 s throughout the period of observation. When the infusion was terminated, an observer was asked to note the time when the 1st through the 4th twitches first became detectable. In group 1, recovery to a TOF ratio > 0.90 was allowed to proceed spontaneously. In groups 2, 3, and 4, 0.3, 0.5, and 0.75 mg/kg edrophonium, respectively, was administered when the 4th response to TOF stimulation first became palpable. Times to TOF ratios of 0.70 and 0.90 were recorded in all groups. RESULTS: TOF counts of 1, 2, 3, and 4 first became palpable at 8 +/- 4% (SD), 20 +/- 6%, 33 +/- 9%, and 44 +/- 10% of control twitch height. Fade on TOF stimulation could no longer be detected once the TOF ratio exceeded a value of 0.41 +/- 0.07 (range 0.25-0.51). Once the 1st evoked response was palpable, the 2nd, 3rd, and 4th responses could be detected 2.5 +/- 1.1 (SD), 4.6 +/- 1.6, and 6.1 +/- 1.6 min later. Spontaneous recovery to TOF fade ratios of 0.7 and 0.9 occurred on average 10.7 +/- 2.3 and 16.9 +/- 4.7 min, respectively, after a threshold count of 4. Administration of 0.3 mg/kg edrophonium shortened the recovery process by about 7.5 min. Increasing the dose of edrophonium beyond 0.3 mg/kg did not further accelerate recovery. CONCLUSIONS: After recovery from profound mivacurium-induced neuromuscular block, TOF counts of 1, 2, 3, and 4 approximate 10%, 20%, 30%, and 40% return to control twitch height, respectively. Finally, > or = 0.3 mg/kg edrophonium will accelerate recovery from mivacurium by approximately 7-8 min.

Adult↗
PubMed1993

Laparoscopy explosion hazards with nitrous oxide.

BACKGROUND: During laparoscopic surgery utilizing carbon dioxide as the insufflating agent, nitrous oxide will diffuse into the peritoneal cavity if it is used as part of the anesthetic. Bowel perforation and the subsequent release of volatile bowel gas could create a explosion hazard. METHODS: Two related studies were undertaken. The first quantified the transfer of nitrous oxide, over time, in 19 female patients undergoing laparoscopy. The second established the lower limits of flammability of a range of concentrations of methane and hydrogen diluted with nitrogen (simulated bowel gas) in a range of concentrations of nitrous oxide diluted with carbon dioxide (simulated peritoneal gas). RESULTS: The mean concentrations of N2O at 10, 20, and 30 min from the time of insufflation were 19.9 +/- 4.8%, 30.3 +/- 6.8%, and 36.1 +/- 6.9%, respectively. The maximum reported concentrations of methane and hydrogen in bowel gas are 56% and 69%, respectively. The concentration of nitrous oxide necessary to support combustion of 56% methane is approximately 47%. By contrast, the concentration of nitrous oxide needed to support combustion of 69% hydrogen is approximately 29%. CONCLUSIONS: The authors have shown that it is possible for nitrous oxide to reach concentrations in the peritoneal cavity that can support combustion of bowel gas.

Adult↗
PubMed1991

Tactile evaluation of train-of-four count as an indicator of reliability of antagonism of vecuronium- or atracurium-induced neuromuscular blockade.

Recent evidence suggests that edrophonium is not the agent of choice to reverse profound neuromuscular blockade but remains an efficacious drug when the level of neuromuscular blockade to be antagonized is modest. We studied 90 healthy adults in an attempt to address the questions: 1) How much variability in such neuromuscular parameters as single twitch height and the train-of-four (TOF) fade ratio (T4/T1) exist when the TOF count first returns to four palpable responses? 2) Is edrophonium a reliable antagonist at this measured point of recovery? 3) What is the optimal dose of edrophonium needed to produce prompt (less than 10 min) and satisfactory (T4/T1 greater than 0.7) reversal when the fourth response of the thumb to indirect TOF stimulation just becomes palpable? Patients were given a bolus atracurium or vecuronium (n = 45 in each group) followed by an iv infusion sufficient to maintain single twitch as measured by electromyography at 10-15% of control values. At the end of surgery, the infusion was terminated and spontaneous recovery was allowed to begin. Once the tactile TOF count was four, edrophonium 0.3, 0.5, or 0.75 mg/kg was administered. At a count-of-four the first twitch averaged 37% of control (+/- 8.5% standard deviation; pooled data from all groups) and the mean T4/T1 ratio was 0.14 +/- 0.049. After atracurium neuromuscular blockade, edrophonium 0.3 mg/kg produced adequate antagonism in 10 min. At this time the mean T4/T1 ratio was 0.79 +/- 0.07 and the lowest observed value was 0.67. Increasing the edrophonium dose to 0.75 mg/kg accelerated recovery by 4-5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗