Alfentanil during rapid sequence induction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg: tracheal intubation conditions.

BACKGROUND: Opioids have become an integral part of anaesthesia induction. We aimed to determine the dose of alfentanil needed to obtain perfect tracheal intubation conditions during rapid sequence induction with standard doses of thiopental and rocuronium, where laryngoscopy was initiated 55 s after commencement of drug administration. The influence of covariates (sex, body weight, age, alfentanil plasma concentration at laryngoscopy) was tested. METHODS: Eighty-four healthy individuals were randomly assigned to receive one of the seven assessor-blinded alfentanil doses (0, 10, 20, 30, 40, 50 and 60 µg/kg) in conjunction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg. For drug administration, 15 s was allowed. Laryngoscopy was initiated 40 s after rocuronium and tracheal intubation concluded within 70 s after commencement of drug administration. Alfentanil doses associated with 50%, 90% and 95% probability of perfect intubation conditions were determined with logistic regression. Multiple logistic regressions were used to test the influence of covariates. The relationship between alfentanil dose and concentration at laryngoscopy was analysed with linear regression. The effects of covariates on plasma concentrations of alfentanil were tested with multiple linear regressions. RESULTS: Perfect intubation conditions of 95% probability was obtained with 56 µg/kg (confidence intervals 44-68). None of the covariates were significant predictors of perfect intubation conditions. Alfentanil plasma concentration correlated with dose and increased with increasing body weight (1.7 ng/ml/kg). CONCLUSION: Perfect intubation conditions during rapid sequence induction can be obtained with clinically relevant doses of alfentanil in most healthy patients anaesthetized with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.

Sex-related differences in the relationship between acceleromyographic adductor pollicis train-of-four ratio and clinical manifestations of residual neuromuscular block: a study in healthy volunteers during near steady-state infusion of mivacurium.

BACKGROUND: Studies in volunteers suggest that train-of-four (TOF) ratios >0.9 are needed to retain normal function of muscles involved in upper airway patency, swallowing, and vital capacity breathing. We determined if sex-related differences exist in the relationship between adductor pollicis (AP) TOF ratio and measures of neuromuscular function commonly used to assess recovery from neuromuscular block. METHODS: In 10 males and 10 females, three steady-state levels of neuromuscular block were achieved with mivacurium infusions. TOF ratio was measured with acceleromyography at the AP. Hand grip strength and the ability to clench the teeth, raise the head >5 s, swallow, protrude the tongue, and open the eyes were tested at each stable block level and reconciled to uncorrected and normalized (pre-paralysis values) TOF measures. These relationships were compared between sexes. RESULTS: The ability to clench teeth and head raise >5 s was lost at a significantly greater TOF ratio in males than females. The percentage decrease in handgrip strength with decreasing TOF ratio was proportionally greater in males than females. Forty per cent of the males were unable to clench the teeth at an uncorrected TOF ratio >0.9. When TOF ratios were normalized, clinical functions showed no decrement at TOF ratio >0.9 in any volunteer. CONCLUSIONS: Sex-related differences exist in the relationship between AP TOF ratio and clinical measures of muscle function used to assess recovery from neuromuscular block. Normalization of AP TOF ratios is recommended because a non-normalized TOF ratio of 0.9 does not guarantee adequate reversal of neuromuscular block.

Dose of alfentanil needed to obtain optimal intubation conditions during rapid-sequence induction of anaesthesia with thiopentone and rocuronium.

BACKGROUND: The primary aim of the present study was to determine the dose of alfentanil that must be added to a rapid-sequence induction (RSI) regimen using thiopentone and rocuronium to obtain optimal intubation conditions in >95% of the individuals. METHODS: A total of 60 ASA I patients were randomly allocated to five different alfentanil dose groups (0, 15, 30, 45, or 60 microg kg-1). A blinded dose of alfentanil followed by thiopentone 4 mg kg-1 and rocuronium 1 mg kg-1 was administered in rapid succession, and tracheal intubation was attempted 40 s thereafter. The relationship between the alfentanil dose and the probability of optimal intubation conditions was determined by non-linear logistic regression analysis. Blood pressure (BP) changes were recorded continuously using an intra-arterial catheter. RESULTS: The success rate of optimal intubation conditions increased with increasing doses of alfentanil. The alfentanil dose needed to obtain optimal intubation conditions in >95% of the patients was 36.4 (CI 33.4-39.4) microg kg-1. In 12 patients, the systolic BP declined to <90 mm Hg during the 3 min immediately after intubation. CONCLUSION: Adding 36-40 microg kg-1 alfentanil to a regimen of thiopentone and rocuronium during RSI of anaesthesia may significantly increase the success rate of optimal intubation conditions. Significant hypotension requiring vasopressor treatment may occur.

A comparison of train-of-four monitoring: mechanomyography at the thumb vs acceleromyography at the big toe.

BACKGROUND: It is not known if the information on neuromuscular function obtained from the hand is interchangeable with that of the foot. In the present study the agreement of thumb mechanomyography with acceleromyography of the big toe was studied. METHODS: Ten healthy patients scheduled for oral surgery were studied. Anaesthesia was induced with fentanyl 2 micrograms kg-1 and propofol 2 mg kg-1, and maintained with propofol 100-175 micrograms kg-1 min-1, nitrous oxide 60-70%, and fentanyl 1-2 micrograms kg-1 h-1. Vecuronium 0.1 mg kg-1 was used for muscle relaxation. Mechanomyography (MMG) of the thumb (Myograph 2000) and acceleromyography (AMG) of the big toe (TOF-Guard) were recorded simultaneously in all patients, and onset, period of no-twitch response, duration of action, and spontaneous recovery time obtained from both muscle groups. The agreement between methods was tested by calculation of bias and limits of agreement. RESULTS: The onset time and duration of action were significantly shorter (87 s vs 154 s, and 35 min vs 38 min, respectively), and the spontaneous recovery time significantly longer in the thumb than in the big toe (32 min vs 19 min). Period of no-twitch response was not significantly different in the two muscle groups. Limits of agreement (thumb big toe) were -21 to -113 s, -7 to 1 min, and -9 to 35 min, for onset time, duration of action, and spontaneous recovery time, respectively. CONCLUSIONS: We conclude that clinically acceptable agreement between thumb mechanomyography and big toe acceleromyography was found for the period of no-twitch response, suggesting that the timing of supplemental doses of vecuronium can be guided by AMG at the big toe. However, the spontaneous recovery time agreement (to TOF ratio = 0.75) between the thumb and the big toe was poor.

Anaphylactic reactions during induction of anaesthesia using rocuronium for muscle relaxation: a report including 3 cases.

Anaphylaxis during induction of anaesthesia is a dreaded complication with a mortality rate of 3-6%, most frequently associated with the use of muscle relaxants. Current knowledge on this matter is reviewed in relation to the presentation of 3 cases of anaphylaxis and bronchospasm associated with the use of the recently released nondepolarizing muscle relaxant rocuronium. Bronchospasm may be the sole sign of a serious drug reaction, triggered by precipitation of insoluble thiopental crystals when mixed with a muscle relaxant in the intravenous (iv) line. It is recommended that these drugs are administered via different injection ports. The hypotension requires immediate treatment with oxygen, epinephrine and large amounts of iv fluids. Epinephrine infusion may be needed for hours. It is recommended that serum tryptase is measured approximately 2 h after debut of the serious drug reaction. Allergy testing should be performed for all the drugs the patient was exposed to, 4-8 weeks after the incident, and due to cross-reactivity, including all available muscle relaxants. Doctors are urged to inform their patients, and systematically register adverse drug reactions.

Awareness in anaesthesia: incidence, consequences and prevention.

Awareness during anaesthesia is a state of consciousness that is revealed by explicit or implicit memory of intraoperative events. Although large clinical surveys indicate an incidence of explicit awareness of < 0.3% during anaesthesia for general surgery, this adverse effect should be a great concern, because patients may be permanently disabled by the experience of being awake during surgery. Prevention of awareness during anaesthesia starts with an appropriate preoperative visit to the patient. The anaesthetic delivery machines must be properly checked before and during anaesthesia. The anaesthetic depth should be assessed by observation of movement responses, and consequently a minimum of muscle relaxants used. Because the anaesthetic depth can be controlled by determination of endtidal drug concentration, volatile inhaled anaesthesia may be associated with a lower frequency of awareness than other anaesthetic regimens.

Rapid tracheal intubation with large-dose rocuronium: a probability-based approach.

UNLABELLED: There are situations in anesthesia in which it may be desirable to achieve rapid tracheal intubation with perfect conditions, i.e., no coughing or straining. To determine the dose of rocuronium that gives a high probability of achieving perfect conditions for rapid (within 60 s) tracheal intubation, we administered a range of doses of rocuronium, some larger than used previously. Sixty adults, anesthetized with thiopental 4 mg/kg IV and alfentanil 10 microg/kg IV, received rocuronium 0.4 to 2.0 mg/kg IV. We used logistic regression to define the relationship of rocuronium dose to probability of achieving perfect intubation conditions. We estimated the doses giving 90% and 95% probability of achieving perfect intubation and used resampling to determine confidence limits for these estimates. Rocuronium 1.85 and 2.33 mg/kg gave, respectively, 90% and 95% probability of perfect intubation conditions. The confidence limits (5th and 95th percentile) for these estimates were 1.15 to 2.31 and 1.23 to 3.22 mg/kg, respectively. In conclusion, it is possible to achieve perfect intubation conditions with large doses of rocuronium, but the long duration of action and expense may limit the usefulness of the technique. IMPLICATIONS: We found that it is possible to have a 90% probability of achieving perfect conditions for rapid tracheal intubation with large (up to 2.0 mg/kg) doses of rocuronium. These large doses of rocuronium may be useful in, for instance, head trauma or open globe injuries if succinylcholine is contraindicated.

Atracurium compared with suxamethonium for outpatient laparoscopy.

I.v. atracurium 0.3 mg kg-1 and suxamethonium 1.6 mg kg-1 plus infusion were compared for use in outpatient laparoscopy. Thirty patients were randomly assigned to receive one of the two blocking drugs. Both drugs proved suitable for use in outpatient laparoscopy, but atracurium may have advantages if the operation proceeds directly to laparotomy.

Rocuronium and cisatracurium-positive skin tests in non-allergic volunteers: determination of drug concentration thresholds using a dilution titration technique.

BACKGROUND: Muscle relaxants are believed to be responsible for 2/3 of the cases of anaphylactic reactions during anesthesia. This assumption is based mainly on positive skin tests obtained in individuals that have experienced anesthesia-related anaphylaxis. A positive skin test is supposed to be associated with mast cell degranulation of vasoactive amines. In the present study we tested the frequency of positive skin tests with two commonly used muscle relaxants, rocuronium and cisatracurium, in a selected group of volunteers with low potential for allergic reactions. METHODS: Thirty healthy volunteers without known allergy or previous exposure to muscle relaxants were studied. Low potential for allergic reactions was determined prior to inclusion in the study, using various allergy tests. Each individual was tested with intradermal and skin prick tests, and molar drug concentration thresholds for positive skin reactions were determined using a dilution titration technique. The presence or absence of mast cell degranulation was tested by electron microscopic investigation of skin biopsies obtained from positive and negative skin reactions. RESULTS: None of the volunteers had a positive skin prick test. More than 90% of the volunteers had a positive intradermal test with both rocuronium and cisatracurium. The highest molar drug concentration that was not associated with a positive intradermal test was 10(-6) M (rocuronium) and 10(-7) M (cisatracurium), equivalent to vial dilution 1 : 1000 for both drugs. In none of the volunteers was mast cell degranulation detected. CONCLUSION: Non-mast-cell-mediated positive intradermal skin reactions are frequently occurring with rocuronium and cisatracurium, even at vial dilution 1 : 1000. A clinically applicable test technique is needed that is able to separate positive skin tests associated with mast cell degranulation from non-mast-cell-mediated reactions.

The effects of clonidine on human digital vasculature.

Large concentrations of alpha(2) agonists cause vasoconstriction. However, the threshold of the vasoconstrictive effect in humans is not known. We studied seven volunteers to determine the lower limit of the vasoconstrictive effect of clonidine. Subjects were studied while they were awake, and they were anesthetized with propofol/alfentanil/N(2)O. Arterial blood pressure was continuously monitored via radial arterial catheter and vasoconstriction via finger volume plethysmography measuring infrared light transmitted through a fingertip (LTF). Clonidine was administered, targeting plasma clonidine concentrations of 0.3, 0.45, 0.68, 1.0, 1.5, and 2.25 ng/mL. The maximum change from preclonidine values for systolic blood pressure (SBP) and LTF was analyzed by using repeated measures analysis of variance. In awake subjects, clonidine (2.25 ng/mL) decreased LTF by 14%+/-13% and SBP from 141+/-7 to 110+/-15 mm Hg (P<0.0001). In contrast, clonidine (2.25 ng/mL) increased LTF in anesthetized subjects by 21%+/-16% and SBP from 91+/-7 to 106+/-19 mm Hg (P<0.0001). We conclude that the same dose of clonidine that decreased blood pressure and caused vasodilation in awake subjects had the opposite effect in anesthetized subjects with reduced sympathetic tone, increasing blood pressure and causing vasoconstriction in human digital vasculature. Our findings suggest that the lower threshold for clonidine-induced vasoconstriction in human digital vasculature is 1.0 ng/mL.

Mild intraoperative hypothermia does not change the pharmacodynamics (concentration-effect relationship) of vecuronium in humans.

To investigate the effect of mild hypothermia on the neuromuscular junction sensitivity to vecuronium, we determined the pharmacodynamics (concentration-effect relationship) of vecuronium in 10 patients (ASA physical class I or II; age range, 21-46 yr; weight range, 54-104 kg), during isoflurane-nitrous oxide-fentanyl anesthesia. Five were cooled to a mean temperature of 34.4 degrees C and five were maintained normothermic at a mean temperature of 36.8 degrees C. Neuromuscular function was monitored by measuring the evoked mechanical response of the adductor pollicis muscle after supramaximal train-of-four stimulation of the ulnar nerve at the wrist. Vecuronium, 3 micrograms.kg-1.min-1, was infused for 10 min, venous blood sampled for 60 min, and twitch tension and plasma concentration data were used to determine pharmacodynamic variables in each patient. Results for the hypothermic and normothermic groups were compared by Mann-Whitney U-test. There were no differences in any pharmacodynamic variable between the hypothermic and normothermic patients. For the hypothermic and normothermic patients, respectively, steady-state plasma concentrations of vecuronium producing 50% neuromuscular block (Css50) were 73 +/- 13 ng/mL (mean +/- SD) and 79 +/- 31 ng/mL; the rate constants for equilibration of vecuronium between the plasma and the neuromuscular junction (Keo) were 0.27 +/- 0.14 per min-1 and 0.26 +/- 0.11 per min, and the power functions representing the slope of the concentration-effect relationship (gamma) were 5.7 +/- 1.9 and 4.4 +/- 1.8.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoregulatory vasoconstriction during isoflurane anesthesia minimally decreases cutaneous heat loss.

The authors tested the extent to which thermoregulatory vasoconstriction decreases cutaneous heat loss during isoflurane anesthesia. Thermoregulatory vasoconstriction was provoked by central hypothermia in five nonsurgical volunteers given isoflurane anesthesia. Peripheral arteriovenous shunt flow was quantified using forearm-fingertip skin-surface temperature gradients and volume plethysmography. Capillary blood flow on the chest was evaluated using laser Doppler flowmetry. The central temperature triggering peripheral vasoconstriction (the thermoregulatory threshold) was 34.6 +/- 0.4 degrees C. Central body temperature decreased less than or equal to 0.2 degrees C in the period from 1 h preceding onset of significant vasoconstriction until 1.5 h afterward. Chest skin-surface blood flow decreased 21% during the period from 2 h before to 1 h after significant fingertip vasoconstriction. In contrast, fingertip blood flow decreased approximately 50-fold in the same period. The correlation between fingertip blood flow and skin-temperature gradient was excellent. Total heat loss decreased approximately 26% (25.3 +/- 3.9 W) in the period from 2 h before significant peripheral vasoconstriction to 1 h afterward. Loss from the arms and legs (upper arm, lower arm, thigh, and calf) decreased approximately 24% in the same period. Heat loss from the trunk and head decreased only 14%; in contrast, loss from the hands and feet decreased approximately 57%. There were no clinically important changes in blood pressure or heart rate during vasoconstriction, but oxyhemoglobin saturation (measured by pulse oximetry) increased slightly. These data suggest that thermoregulatory vasoconstriction only minimally decreases cutaneous heat loss.

The effect of hypothermia on adductor pollicis twitch tension during continuous infusion of vecuronium in isoflurane-anesthetized humans.

The effect of total body cooling on force of contraction of the adductor pollicis was determined during a constant rate infusion of vecuronium. Anesthesia was induced with thiopental and maintained with isoflurane/nitrous oxide in eight volunteers (study group) and seven surgical patients (control group). After train-of-four (TOF) stimulation of the ulnar nerve, we measured the amplitude of the first response (T1) in the train and the ratio of the fourth-to-first response (TOF ratio). Vecuronium was then administered as an intravenous (i.v.) bolus, 25 micrograms/kg, followed by continuous i.v. infusion, 25 micrograms.kg-1 x h-1; central body (core) temperature was maintained stable for 60 min, at the end of which T1 and TOF responses were constant. In the study group, core temperature was then reduced (using circulating-water blankets) by a mean of 2.6 degrees C, decreasing the T1 and TOF ratio, respectively, by 19% and 18% per degrees C reduction in adductor pollicis temperature. Normothermia was maintained in the control group for a mean of 111 min, with no significant change in T1 and TOF responses. We conclude that, during a constant-rate infusion of vecuronium, the magnitude of neuromuscular block increases significantly when adductor pollicis temperature decreases secondary to core cooling.

[Intraspinal hematoma after thoracic epidural analgesia]. / Intraspinal bløning etter torakal epidural smertebehandling.

In one year three patients were operated on for spinal haematomas following thoracic epidural analgesia. All three patients experienced back pain and developed progressive paraparesis, one in connection with insertion of the catheter and two after its removal. A spinal block was visualized using MRI in two patients and myelography in one. The patients were operated on with posterior decompression. In two patients an epidural haematoma was evacuated. Both patients recovered neurologic function, one completely. The third patient, who had a subarachnoidal hemorrhage and an intramedullar haematoma, remained paralytic.

1 MAC-incision sevoflurane prevents explicit awareness during surgical skin incision and tracheal intubation.

BACKGROUND: This study tested the hypothesis that 1 MAC-incision anesthesia secures unconsciousness during surgical skin incision and tracheal intubation. METHODS: Twenty patients scheduled for gynecological laparotomy were anesthetized with sevoflurane as the sole agent. At 1 MAC-incision steady-state conditions, the patients were observed for autonomic/movement responses and wakefulness (response to verbal commands) in the 1-min period following surgical skin incision and tracheal intubation. RESULTS: Blood pressure and heart rate increased significantly secondary to both stimuli, and significantly more after tracheal intubation than skin incision. Ten and 19 patients moved in response to skin incision and tracheal intubation, respectively. None of the patients showed wakefulness. CONCLUSION: It is concluded that 1MAC-incision sevoflurane secures unconsciousness during surgical skin incision and tracheal intubation.

Mild intraoperative hypothermia increases duration of action and spontaneous recovery of vecuronium blockade during nitrous oxide-isoflurane anesthesia in humans.

We compared the duration of action and recovery times for vecuronium in normothermic and mildly hypothermic patients. Ten patients were actively cooled to a central body temperature near 34.5 degrees C, and ten were maintained at a normothermic central temperature (greater than 36.5 degrees C); temperature was measured in the distal esophagus. Vecuronium 0.1 mg/kg was administered as an intravenous (iv) bolus to all patients, and the evoked mechanical response to train-of-four stimulation was recorded. Five hypothermic and five normothermic patients were allowed to recover spontaneously. In the remaining five in each group, neostigmine (40 micrograms/kg) and atropine (20 micrograms/kg) was administered when the first twitch (T1) height spontaneously recovered to 10% of control (T1 = 10% of the pre-vecuronium twitch tension). Vecuronium's duration of action (from injection of drug until T1 = 10%) was 28 +/- 4 and 62 +/- 8 min during normothermia and hypothermia, respectively (P less than 0.05). The corresponding values for spontaneous recovery from T1 = 10% to TOF ratio greater than 75% were 37 +/- 15 and 80 +/- 24 min (P less than 0.05), and for neostigmine-induced recovery were 10 +/- 3 and 16 +/- 11 min (difference not significant). We conclude that mild hypothermia increases the duration of action of and time for spontaneous recovery from vecuronium-induced neuromuscular blockade.

Does discontinuation of desflurane at the time of neostigmine administration speed recovery from cisatracurium block compared to that with a propofol-based technique?

BACKGROUND: Volatile anaesthetics are known to influence the effect of neostigmine as an antagonist of neuromuscular block. The aim of the present study was to investigate whether discontinuation of desflurane at the time of neostigmine administration shortens reversal time from cisatracurium block, compared to that with a propofol-based anaesthesia. METHODS: Ten volunteers were studied twice. For one study, anaesthesia was induced with alfentanil and propofol and maintained with nitrous oxide 70% and propofol 150 microg. kg-1. min-1. For the other study, experimental conditions were replicated except that desflurane 6% was administered and the dose of propofol was only 50 microg. kg-1. min-1. The evoked mechanical response of the adductor pollicis to train-of-four (TOF) stimulation was recorded. Neuromuscular block was induced with cisatracurium 0.2 mg. kg-1. When the magnitude of the first TOF response (T1) had recovered to 10%, the block was antagonized with neostigmine 70 microg. kg-1. At this time, propofol was decreased to 50 microg. kg-1. min-1, or the desflurane was discontinued. RESULTS: There were no significant differences between the two techniques of anaesthesia in the rate of neostigmine-induced recovery of the TOF ratio. The times (mean+/-SD) to achieve TOF ratios of 0.7, 0.8, and 0.9 were (propofol first, desflurane second) 6.1+/-2.2 and 6.5+/-1.6 min; 10.4+/-4.2 and 9.6+/-2.7 min; 17.1+/-6.9 and 21.0+/-13.0 min, respectively. CONCLUSION: Discontinuing desflurane does not speed neostigmine-induced recovery from cisatracurium neuromuscular block, when compared to that during propofol-based anaesthesia.

The effect of local surface and central cooling on adductor pollicis twitch tension during nitrous oxide/isoflurane and nitrous oxide/fentanyl anesthesia in humans.

This study aimed to determine whether: 1) the method of cooling the hand (i.e. central [total body] vs. local surface [hand only]) influences the relationship between the adductor pollicis temperature and twitch tension; and 2) decreased evoked twitch response during hypothermia is due to reduced muscle temperature and/or the anesthetic drug used. First, the effect of local surface cooling on adductor pollicis twitch tension during isoflurane anesthesia was determined in 15 patients, while central body temperature was not allowed to decrease. Adductor pollicis temperature and twitch tension decreased in a linear manner (P less than 0.05). However, the magnitude of the decreased response was only 43% of that observed during central cooling in the authors' previous study under otherwise similar experimental conditions. Second, the effect of central cooling on adductor pollicis twitch tension during nitrous oxide/fentanyl anesthesia was determined in five patients. The twitch tension did not decrease until the adductor pollicis temperature decreased below 35.2 degrees C. Below this temperature, twitch tension decreased 16%/degrees C reduction in muscle temperature. These results are similar to those obtained in the authors' previous study in patients anesthetized with nitrous oxide/isoflurane anesthesia. The authors conclude that both central and local surface cooling of the adductor pollicis muscle reduces twitch tension and that the decrease in adductor pollicis twitch tension is the same during nitrous oxide/isoflurane and nitrous oxide/fentanyl anesthesia.

The relationship between adductor pollicis twitch tension and core, skin, and muscle temperature during nitrous oxide-isoflurane anesthesia in humans.

Temperature and volatile anesthetic agents influence neuromuscular transmission. Because mild hypothermia is common during general anesthesia, the authors sought to determine the relationship between the core temperature, adductor pollicis muscle temperature, and the twitch response of the adductor pollicis muscle, during isoflurane anesthesia in 15 patients undergoing elective surgery in which muscle relaxants were not required. Five patients were allowed to cool spontaneously, five were cooled actively, and normothermia was maintained actively in the remaining five. In the normothermic patients (core greater than 36.5 degrees C, muscle greater than 35.7 degrees C), the twitch response of the muscle remained unchanged from control values. In the patients who were cooled passively or actively, a muscle temperature threshold was observed (35.2 degrees C), below which twitch response of the muscle diminished by 10-15%/degrees C decrease in muscle temperature. To ensure that the adductor pollicis muscle temperature remained above 35.2 degrees C, the core temperature had to be maintained above 36 degrees C. A significant linear relationship (P less than 0.05) was found between the adductor pollicis muscle temperature and twitch tension below the threshold for each individual patient in the cooled groups (correlation coefficient range, 0.80-0.99). Thus, there is a temperature-related decrease in adductor pollicis twitch response during isoflurane anesthesia, and the temperature of this muscle should be maintained above 35-35.5 degrees C during studies of neuromuscular transmission. This can be achieved by maintaining core temperature above 36 degrees C.

Hemoglobin desaturation after succinylcholine-induced apnea: a study of the recovery of spontaneous ventilation in healthy volunteers.

BACKGROUND: Because of the rapid recovery of neuromuscular function after succinylcholine administration, there is a belief that patients will start breathing sufficiently rapidly to prevent significant oxygen desaturation. The authors tested whether this belief was valid. METHODS: Twelve healthy volunteers aged 18-45 yr participated in the study. After preoxygenation to an end-tidal oxygen concentration greater than 90%, each subject received 5 mg/kg thiopental and 1 mg/kg succinylcholine. Oxygen saturation (SaO2) was measured at both a finger and an ear lobe (beat to beat). During the period of apnea and as they were recovering, the volunteers received continuous verbal reassurance by the investigators. If the SaO2 decreased below 80%, the volunteers received chin lift and, if necessary, assisted ventilation. The length of time the subject was apneic and level of desaturation were related by linear regression analysis. One hour after recovery and again 1 week later, subjects were asked a series of questions regarding their emotional experience. RESULTS: In six volunteers, SaO2 decreased below 95% during apnea; in four, SaO2 decreased below 80%, necessitating chin lift and assisted ventilation in three. Apnea time was significantly longer in volunteers who reached SaO2 less than 80% than in those who did not (7.0+/-0.4 and 4.1+/-0.3 min, respectively), and there was a significant correlation between the length of time the subject was apneic and the magnitude of desaturation. CONCLUSIONS: Spontaneous recovery from succinylcholine-induced apnea may not occur sufficiently quickly to prevent hemoglobin desaturation in subjects whose ventilation is not assisted.