Prolonged mivacurium neuromuscular block in children

The authors report two cases of prolonged neuromuscular block after administration of mivacurium in children with previously undiagnosed plasma cholinesterase deficiency related to homozygous atypical genotype. Their anaesthetic management is described as well as determination of the phenotype of both children and their family.

Halothane and isoflurane decrease alveolar epithelial fluid clearance in rats

BACKGROUND

Active sodium transport is the primary mechanism that drives alveolar fluid clearance. In the current study, the effects of exposure to halothane and isoflurane on alveolar fluid clearance in rats were evaluated.

METHODS

Rats were exposed to either halothane (0.4% for 6 h or 2% for 2 h) or isoflurane (0.6% for 6 h or 2.8% for 2 h). Reversibility of halothane effects was assessed after 2 h of exposure to 2% halothane. Alveolar and lung liquid clearance were measured by intratracheal instillation of a 5% albumin solution with 1.5 microCi of 125I-albumin, during mechanical ventilation with 100% FiO2 and the halogenated agent. The effect of terbutaline (10(-4) M) added to the albumin solution was tested after 2 h of exposure to 2% halothane. The increase in protein concentration in the airspaces over 1 h was used to evaluate alveolar liquid clearance. Lung liquid clearance was calculated gravimetrically.

RESULTS

Alveolar liquid clearance rates were decreased by 24%, 30% and 40% compared with controls (P < 0.05) after 2 h of exposure to halothane, 6 h of exposure to halothane, and 6 h of exposure to isoflurane, respectively. After 2 h of exposure to isoflurane, alveolar liquid clearance did not change. In the 2-h halothane exposure group, alveolar liquid clearance returned to the control value 2 h after withdrawal of halothane. Terbutaline increased alveolar liquid clearance by 50% and 89% in the control and 2-h halothane exposure groups, respectively. In all experiments, the same results were obtained for alveolar and lung liquid clearance.

CONCLUSIONS

Halothane and isoflurane caused a reversible decrease in alveolar epithelial fluid clearance. Two hours of exposure to halothane did not alter the stimulatory effect of terbutaline on alveolar liquid clearance.

Susceptibility to upper airway obstruction during partial neuromuscular block

BACKGROUND

Airway obstruction after anesthesia may be caused or exaggerated by residual neuromuscular block, with loss of muscle support for collapsible upper airway structures.

METHODS

Six male volunteers were studied before treatment, during stable partial neuromuscular block with vecuronium at a mean train-of-four (TOF) ratio of 50% (95% CI, 36-61%), and after reversal by neostigmine. Catheter-mounted transducers were placed in the pharynx and esophagus to estimate, respectively, the upper airway resistance, and the work of breathing (calculated as the time integral of the inspiratory pressure developed by the respiratory muscles, esophageal pressure time product) during quiet breathing, during breathing 5% carbon dioxide, and while breathing with an inspiratory resistor. Breathing with pressure at the airway opening held at pressures from -5 to 40 cm H2O were also tested to assess airway collapsibility.

RESULTS

Although breathing through a resistor increased upper airway resistance from 1.2 (0.67, 1.72) cm H2O x l(-1) x s to 2.5 (1.32, 3.38) cm H2O x l(-1) x s, and carbon dioxide stimulation reduced resistance to 0.8 (0.46, 1.33) cm H2O x l(-1) x s, no effect of partial neuromuscular block (mean TOF ratio, 52%) on upper airway properties could be shown.

CONCLUSIONS

Neuromuscular block with a TOF ratio of 50% can be present yet clinically difficult to detect in patients recovering from anesthesia. This degree of block has no effect on airway patency in volunteers, even during challenge. Airway obstruction during recovery from anesthesia thus is more likely to be caused by residual effects of general anesthetic agents or centrally acting analgesics, either alone or perhaps in concert with residual neuromuscular block.

Intubating conditions using cisatracurium after induction of anaesthesia with thiopentone

We studied tracheal intubation conditions produced by the muscle relaxant, cisatracurium, following induction of anaesthesia with fentanyl (2 micrograms.kg-1) and thiopentone (6 mg.kg-1). Sixty patients were randomly assigned to receive cisatracurium in a single bolus dose of either 0.15 or 0.20 mg.kg-1. Tracheal intubation was commenced 120 s after injection of the relaxant. The mean (SD) time taken to achieve intubation was significantly shorter in the 0.20 mg.kg-1 group (137 (16) s) than the 0.15 mg.kg-1 group (149 (12) s; p < 0.05). The intubating conditions were better after the larger dose. Our results suggest that when anaesthesia is induced using thiopentone, a dose of 0.20 mg.kg-1 of cisatracurium is recommended to ensure satisfactory intubating conditions.

Comparison of the effects of mivacurium on the diaphragm and geniohyoid muscles

Although subjects often report difficulty with swallowing shortly after receiving neuromuscular blocking agents, difficulty with swallowing during recovery from neuromuscular blocking agents appears to be infrequent. We have used electromyography to compare onset and recovery at the diaphragm and geniohyoid airway muscles after an intubating dose of mivacurium (0.2 mg kg-1) to determine if the geniohyoid muscles were particularly sensitive to neuromuscular blocking agents. Twelve adults undergoing elective surgery were anaesthetized with propofol and fentanyl and the trachea intubated without neuromuscular blocking agents. The left hypoglossal and right phrenic nerves were stimulated with percutaneous needle electrodes and the electromyogram recorded with surface electrodes. EMG responses were measured after a bolus dose of mivacurium 0.2 mg kg-1. Recordings were also made of the mechanical response of the adductor pollicis to supramaximal ulnar nerve stimulation. There was no difference in the rate of onset of block for geniohyoid muscles and the diaphragm, but recovery to 25% and 90% of the control response was shorter at the diaphragm (median 14.5 (95% confidence limits 12.9-15.3) min and 23.8 (21.7-26) min) than at the geniohyoid muscle (19.4 (15.6-20.1) min and 29.2 (26.3-31.4) min), respectively (P < 0.05). When the train-of-four ratio of the mechanical response of the thumb reached 70%, the diaphragm and geniohyoid muscles had recovered completely in all patients.

A comparison of the neuromuscular blocking effects of atracurium, mivacurium, and vecuronium on the adductor pollicis and the orbicularis oculi muscle in humans

Both the orbicularis oculi (OO) and the adductor pollicis (AP) muscles have been used to indirectly quantify the extent of neuromuscular block of the respiratory muscles. To clarify any differences in response of these muscles to neuromuscular blocking drugs, the effects of two different doses of atracurium, mivacurium, and vecuronium on the AP and OO were studied. A new technique was used to measure the evoked mechanical response of the OO with accelerometry. Fifty premedicated patients were anesthetized with 5-8 mg/kg thiopental and 2 micrograms/kg fentanyl intravenously (i.v.). They were randomly allocated to receive a single dose of either 300 or 500 micrograms/kg atracurium, 150 or 250 micrograms/kg mivacurium, or 60 or 100 micrograms/kg vecuronium i.v. After orotracheal intubation, anesthesia was maintained with nitrous oxide 60% in oxygen, isoflurane 0.5%-1.5% end-tidal, and 1-2 micrograms/kg fentanyl boluses as required. The evoked response of the AP after ulnar nerve stimulation was measured using a force transducer, and that of the OO after facial nerve stimulation was measured with accelerometry using a piezoelectric probe fixed to the eyelid. The following variables were recorded for each muscle: the maximum depression of the first twitch response to the train-of-four (EMAX), the time to achievement of EMAX (TMAX), the time to recovery of the first twitch response to 25%, 50%, 75%, and 90% of control value (TH25, TH50, TH75, and TH90, respectively) and the time to recovery of the train-of-four response to a ratio of 70% (TOF 0.7). The smaller dose of each relaxant was significantly less potent than the larger dose at the OO. TMAX was shorter for the OO than for the AP at the larger dose of each drug. TH 25 was shorter at the OO than at the AP with 0.5 mg/kg atracurium, but there was no significant difference with 0.25 mg/kg atracurium. TH25 and TH50 were both faster at the OO than at the AP with mivacurium, but there was no difference with vecuronium. TOF 0.7 was shorter with the smaller dose of each drug, but there was no difference with the higher doses. It is concluded that it is possible to record the mechanical response of the OO muscle using a noninvasive method. There are differences between the responses of the OO and the AP to neuromuscular blockers that depend upon both the specific drug itself and the dose used.

End-tidal carbon dioxide during cardiopulmonary resuscitation in humans presenting mostly with asystole: a predictor of outcome

OBJECTIVE

To determine whether continuous semiquantitative assessment of end-tidal CO2 could provide a highly sensitive predictor of return of spontaneous circulation during cardiopulmonary resuscitation (CPR).

DESIGN

Prospective, clinical study.

SETTING

Prehospital CPR.

PATIENTS

One hundred twenty patients, during nontraumatic cardiac arrest.

INTERVENTIONS

End-tidal CO2 values were measured continuously after tracheal intubation, and were categorized as the initial value, and as minimal and maximal values during the first 20 mins.

MEASUREMENTS AND MAIN RESULTS

Presenting rhythm was asystole in 22 of the first 24 patients. Return of spontaneous circulation occurred in eight patients. Initial, minimal, and maximal end-tidal CO2 values were significantly (p < .01) higher in these patients than in the patients without return of spontaneous circulation. Cutoff values providing a 100% sensitivity and the highest specificity in predicting return of spontaneous circulation were found to be 10 torr for initial and maximal end-tidal CO2 values, and 2 torr for the minimal end-tidal CO2 value. The number of patients required to reject (with a risk error of <.05) the hypothesis of an actual sensitivity of < or = 90% for an observed sensitivity of 100% was found to be 95. In the second part of the study, this hypothesis was prospectively tested for initial and maximal end-tidal CO2 values in the subsequent 96 patients. Presenting cardiac rhythm was asystole in 87 patients. Return of spontaneous circulation was obtained in 30 patients. The cutoff value of 10 torr for maximal end-tidal CO2 during the first 20 mins after tracheal intubation provided an observed sensitivity of 100% in predicting return of spontaneous circulation with a specificity of 67%. This result allows rejection of the hypothesis of an actual sensitivity of < or = 90% (p = .042). By contrast, the observed sensitivity of initial end-tidal CO2 was only 87%.

CONCLUSIONS

End-tidal CO2 represents a valuable tool for monitoring patients presenting with asystole during prehospital CPR. Fluctuations in end-tidal CO2 during CPR and the utility of end-tidal CO2 in detecting return of spontaneous circulation justify its continuous measurement. In addition, a high sensitivity (>90%) in predicting return of spontaneous circulation is prospectively demonstrated using the maximal end-tidal CO2 during the first 20 mins after tracheal intubation, with a cutoff value of 10 torr. Such a prognostic indicator could be used for a more rational approach to prolonged CPR.

Neostigmine reversal of vecuronium neuromuscular block and the influence of renal failure

The duration of clinical relaxation induced by vecuronium and reversal by neostigmine was studied in 40 patients with renal failure (RF) and 40 patients with normal renal function (NL) under general anesthesia. Patients were premedicated with flunitrazepam, and anesthesia commenced with fentanyl 1-2 micrograms/kg, thiopental 5-8 mg/kg, and vecuronium 0.1 mg/kg. Anesthesia was maintained with 60% nitrous oxide in oxygen, isoflurane 0.3%-1.0% end-tidal concentration, and 1 microgram/kg fentanyl every 20-30 min. Neuromuscular block was reversed by the administration of intravenous neostigmine 40 mg/kg at the time of reappearance of either two or four responses to the train-of-four (TOF) stimulation. Monitoring of neuromuscular function consisted of supramaximal TOF stimulation of the ulnar nerve and the evoked thumb response was registered using a force transducer. Spontaneous recovery time, reversal time, and the time to recovery of TOF ratio to 0.7 were recorded. RF did not prolong the vecuronium neuromuscular blocking effect, reversal was achieved at the same rate in NL as in RF, and the duration of reversal of neuromuscular blocking effect of vecuronium was not influenced by the time of administration of neostigmine. Therefore, the neuromuscular blocking effect of a tracheal intubating dose of vecuronium can be reversed at the same rate in patients with end-stage RF as in patients with normal kidney function.

Intubating conditions following 1R CIS, 1'R CIS atracurium (51W89). A comparison with atracurium

51W89 besylate, a new intermediate acting non-depolarising muscle relaxant, consisting of a single stereo-isomer of the commercial preparation of atracurium has been assessed in respect of intubating conditions during nitrous oxide-propofol-isoflurane anaesthesia. Intubating conditions at 2 min were acceptable in 67% of patients following a dose of 0.1 mg.kg-1 and in 90% of patients following a dose of 0.15 mg.kg-1. Intubating conditions at 1.5 min were acceptable in 76% of patients following a dose of 0.2 mg.kg-1. In comparison, intubating conditions at 2 min were acceptable in 95% of patients following 0.5 mg.kg-1 of atracurium. The intubating conditions at 2 min following a dose of 0.1 mg.kg-1 51W89 besylate were significantly worse than the other three groups (p < 0.05); however, there was no significant differences between the scores in the other three groups. There was no clinical evidence of histamine release in the groups receiving 51W89 besylate compared to two out of the 19 patients who had cutaneous flushing following the administration of atracurium. Our results suggest that 51W89 besylate provides acceptable intubating conditions at 2 min following a dose of 0.15 mg.kg-1 and may prove to be an acceptable alternative to atracurium if studies in progress confirm its greater cardiovascular stability and reduced propensity to release histamine than its parent compound.

Comparison of duration of neuromuscular blocking effect of atracurium and vecuronium in young and elderly patients

In a controlled, randomized study, we evaluated duration of neuromuscular block in 80 patients undergoing routine abdominal surgery. Forty patients were aged 18-50 yr (control group) and 40 patients were more than 65 yr (elderly group). All patients had normal plasma creatinine concentrations. After induction of anaesthesia, patients were allocated randomly to receive either atracurium 0.5 mg kg-1 or vecuronium 0.1 mg kg-1 to facilitate tracheal intubation. Monitoring of the evoked response of the adductor pollicis muscle to supramaximal single twitch ulnar nerve stimulation every 10 s was performed and measured with a strain gauge. Repeat doses of atracurium 0.1 mg kg-1 or vecuronium 0.02 mg kg-1 were administered when the adductor pollicis response recovered to 25% of the control twitch height. We found that the duration of action of the initial dose of atracurium was similar in the control and elderly groups, and it did not vary after repeated doses. However, the initial dose of vecuronium caused a significantly longer period of clinical block in the elderly group compared with the controls, and the duration of action of repeated doses was longer in the elderly group. We conclude that as there is a risk of prolonged effect of vecuronium in the elderly, monitoring of neuromuscular function is recommended in this group. Alternatively, atracurium should be preferred for prolonged surgery in elderly patients.

Comparison of the neuromuscular blocking effect of atracurium and vecuronium on the adductor pollicis and the geniohyoid muscle in humans

BACKGROUND

Residual paralysis of suprahyoid muscles may occur when the adductor pollicis response has completely recovered after the administration of a neuromuscular blocking agent. The response of the geniohyoid muscle to intubating doses of muscle relaxants is evaluated and compared to that of adductor pollicis.

METHODS

Sixteen patients undergoing elective surgery under general anesthesia were given 5-7 mg.kg-1 thiopental and 2 micrograms.kg-1 fentanyl intravenously for induction of anesthesia. Eight (half) patients then received 0.5 mg.kg-1 atracurium, and the other eight received 0.1 mg.kg-1 vecuronium. The evoked response (twitch height, TH) of the adductor pollicis was monitored by measuring the integrated electromyographic response (AP EMG) on one limb and the mechanical response, using a force transducer (AP force), on the other. The activity of geniohyoid muscle (GH EMG) was measured using submental percutaneous electrodes. The following variables were measured: maximal TH depression; onset time for neuromuscular blockade to 50%, 90%, and maximal TH depression (OT50, OT90, and OTmax); times between administration of neuromuscular blocking agent and TH recovery to 10%, 25%, 50%, 75%, and 90% of control; and time for return of train-of-four ratio to return to 0.7.

RESULTS

The principal findings were (1) OTmax was significantly (P < 0.01) shorter for geniohyoid than for adductor pollicis after either atracurium or vecuronium (OTmax was 216, 256, and 175 s for AP force, AP EMG, and GH EMG, with atracurium and 181, 199, and 144 s with vecuronium, respectively), and (2) the evoked EMG of geniohyoid recovered at the same speed as the EMG of adductor pollicis after an intubating dose of atracurium or vecuronium (recovery of TH to 75% of control at 50, 48, 42 min with AP force, AP EMG, and GH EMG with atracurium and 46, 45, and 42 min with vecuronium, respectively).

CONCLUSIONS

Once the adductor pollicis response has returned to normal values after a single intubating dose of atracurium or vecuronium, the risk of residual depression of the TH of the geniohyoid muscle, one of the principal muscles contributing to airway patency, appears unlikely.

Onset of neuromuscular block is the same if the ipsilateral or contralateral limb to the injection site is used for monitoring

We studied 40 healthy adult patients undergoing elective surgery who were premedicated with flunitrazepam. Before induction of anaesthesia, one of the upper limbs was cannulated and an i.v. infusion of 0.9% saline commenced. Patients were given fentanyl and thiopentone for induction of anaesthesia and then 50% (20 patients) received atracurium 0.5 mg kg-1 and the other 50% vecuronium 0.1 mg kg-1. Neuromuscular block (maximum degree of depression of the elicited first twitch and the onset time of depression of twitch height to 50%, 90% and 100% of control) and skin temperature (at the thenar eminence) were monitored in both the limb with the i.v. infusion and the non-cannulated upper limb. There was no difference in onset time and degree of neuromuscular block between the two upper limbs. Skin temperature was not significantly different between the two upper limbs. We conclude that each upper limb, irrespective of whether an i.v. infusion is in progress, may be used for monitoring onset of neuromuscular block.

Recovery of the swallowing reflex after propofol anesthesia

The swallowing reflex is depressed by anesthetics. During recovery from anesthesia the rapid return of laryngeal and upper airway reflexes is important to protect the lower airway from aspiration. This study measures the recovery of the swallowing reflex after propofol anesthesia. Fifteen patients undergoing a colonoscopy under general anesthesia were studied. No premedication was given. Anesthesia was induced with propofol 2 mg/kg followed by an infusion of 10 mg.kg-1.h-1. The swallowing reflex was measured every 3 min after the end of propofol infusion for 30 min. To initiate swallowing, 0.3 mL of distilled water was injected into the pharynx at two different speeds: a slow injection over 3 s, and a bolus injection. The swallowing reflex was determined by measuring the latency period (i.e., time from water injection to start of electromyographic (EMG) activity measured in the glossal muscles). Swallowing activity was determined by integration of the EMG (EMGi) of the glossal muscles during swallowing. The latency periods after slow and bolus injections were significantly increased for the first 12 min after the end of the propofol infusion and returned to control (preanesthetic values) at 24 min. The EMGi was significantly decreased over the first 12 min and returned to control at 21 min. Propofol depresses the swallowing reflex, but complete recovery is rapid. This study suggests that the oral intake could be allowed early after recovery from anesthesia when propofol is used as the sole anesthetic.

Neuromuscular effects of rocuronium on the diaphragm and adductor pollicis muscles in anesthetized patients

BACKGROUND

Rocuronium has properties that may make it suitable for rapid-sequence intubation. However, its neuromuscular effects have been studied only on the adductor pollicis. This study compares the neuromuscular effect of rocuronium on the diaphragm and adductor pollicis in humans.

METHODS

The forces generated by the diaphragm and the adductor pollicis during supramaximal single-twitch stimulation of the phrenic and ulnar nerves, respectively, were studied during thiopental, fentanyl, and nitrous oxide-oxygen anesthesia. In 6 patients, cumulative doses of 0.15, 0.25, 0.35, 0.45, and 0.60 mg.kg-1 rocuronium were given over a 9-min period. The doses for 50% (ED50) and 95% (ED95) depression of twitch height were calculated. In another 12 patients, the times for maximal effect and 10%, 25%, 50%, 75%, and 90% recovery of the twitch height were calculated after a bolus dose of 0.60 mg.kg-1 rocuronium.

RESULTS

ED50 and ED95 were higher for the diaphragm (0.26 +/- 0.07 and 0.50 +/- 0.20 mg.kg-1, respectively) than for the adductor pollicis (0.14 +/- 0.05 and 0.24 +/- 0.04 mg.kg-1). Rocuronium 0.60 mg.kg-1 produced 100% paralysis of the adductor pollicis in all patients and of the diaphragm in 9 of 12 patients. The onset time for muscle relaxation after 0.6 mg.kg-1 rocuronium was shorter for the adductor pollicis than for the diaphragm (80 +/- 20 vs. 120 +/- 62 s). Times for 10%, 25%, 75%, and 90% recovery of twitch height were 34 +/- 10, 40 +/- 13, 56 +/- 20, and 64 +/- 21 min, respectively, for the adductor pollicis, and significantly shorter for the diaphragm: 17 +/- 10, 23 +/- 9, 33 +/- 13, and 35 +/- 10 min, respectively.

CONCLUSIONS

The diaphragm is more resistant than the adductor pollicis to rocuronium, as shown by greater ED50 and ED95 and faster recovery of the twitch height. The intubating dose of 0.60 mg.kg-1 is close to the ED95 of 0.50 mg.kg-1 for the diaphragm.

Plasma and cerebrospinal fluid concentrations of morphine and morphine glucuronides after oral morphine. The influence of renal failure

BACKGROUND

In patients with renal failure, morphine may cause prolonged narcosis and respiratory depression. Accumulation of the pharmacologically active metabolite morphine-6-glucuronide (M-6G) may explain this effect of morphine in patients with renal failure. After a single oral dose, morphine and its conjugates were measured in the plasma and the cerebrospinal fluid (CSF) in patients with renal failure.

METHODS

Eight patients with normal renal function and six patients with renal failure requiring dialysis were studied after operation under spinal anesthesia. Plasma and CSF concentrations of morphine, morphine-3-glucuronide (M-3G), and M-6G were measured by high-pressure liquid chromatography every 4 h for 24 h after an oral dose of 30 mg morphine.

RESULTS

The area under morphine plasma concentration-time curve from 0 to 24 h increased from 38 +/- 4 ng.ml-1 x h in patients with normal renal function to 110 ng.ml-1 x h in those with renal failure (P < 0.01). In patients with renal failure, plasma concentrations of M-3G and M-6G were higher at 4 h and remained at an increased level until the end of the study. The peak CSF concentration of morphine at 8 h was similar in those with renal failure or normal renal function, 1.8 +/- 0.4 and 2.0 +/- 0.6 ng.ml-1 respectively. M-3G and M-6G in CSF reached a maximum at 12 h in patients with normal renal function, whereas in those with renal failure the concentrations gradually increased so that the highest concentrations were observed at 24 h. At 24 h, CSF M-6G concentration was 15 times greater in patients with renal failure than in those with normal renal function.

CONCLUSIONS

We conclude that M-3G and M-6G readily cross the blood-brain barrier in patients with normal renal function or with renal failure. In patients with renal failure, the retention of plasma M-6G induces a progressive accumulation of this active metabolite in CSF; this accumulation may explain the increased susceptibility to morphine in patients with renal failure.

Pharmacokinetics and pharmacodynamics of rocuronium in patients with cirrhosis

BACKGROUND

Rocuronium, like other steroidal nondepolarizing muscle relaxants, may in part be eliminated by the liver. To determine the influence of liver disease on its neuromuscular blocking effect, we studied the pharmacokinetics and pharmacodynamics of rocuronium in patients with cirrhosis.

METHODS

Eighteen patients undergoing elective surgery, 10 with cirrhosis and 8 with normal liver function, were studied. Anesthesia was induced with intravenous thiopental 5-7 mg.kg-1 and maintained with 60% nitrous oxide in oxygen and repeated doses of fentanyl 2 micrograms.kg-1. The force of thumb adduction in response to supramaximal ulnar nerve stimulation was monitored and recorded. An intravenous bolus of rocuronium 0.6 mg.kg-1 was administered and venous blood sampled at frequent intervals for 6 h. Plasma concentrations of rocuronium was measured by high-pressure liquid chromatography. Data were fitted to both a pharmacokinetic and a pharmacodynamic model by using a two-compartment open model and an effect compartment model. Data were analyzed by least-squares regression.

RESULTS

The onset of neuromuscular blockade was longer (P < 0.01) in patients with cirrhosis (158 +/- 56 s) than in normal patients (108 +/- 33 s). Recovery of the thumb twitch to 75 and 90% of its control value was 77 +/- 25 and 88 +/- 29 min in cirrhotic patients versus 57 +/- 11 and 64 +/- 13 min, respectively, in normal patients (P < 0.05). The central volume of distribution of rocuronium was 104 +/- 21 in cirrhotic patients and 78 +/- 24 ml.kg-1 in normal patients (P < 0.05). No significant difference in elimination kinetics was observed between the two groups. The elimination half-life was 87.5 +/- 17.5 min in normal patients and 96.0 +/- 36.8 min in cirrhotic patients (difference not significant). This increased onset time was linearly correlated to the increased central volume of distribution of rocuronium in cirrhosis.

CONCLUSION

Rocuronium onset time is longer in cirrhotic patients than in those with normal liver function; this can be explained by an increase in the volume in which rocuronium initially distributes. Although elimination kinetics are unchanged in patients with cirrhosis, rocuronium recovery time is prolonged in cirrhotic patients.

Effect of epinephrine on end-tidal carbon dioxide pressure during prehospital cardiopulmonary resuscitation

This prospective study was designed to quantify the effect of epinephrine on end-tidal PCO2 (PetCO2) during prehospital cardiopulmonary resuscitation (CPR) in humans. It included 20 patients (age range, 26 to 90 years) who presented in ventricular asystole on arrival of the prehospital medical team. Protocol began 5 minutes after tracheal intubation and during chest compressions. Mechanical ventilation was applied at constant rate and tidal volume. PetCO2 was measured before and 3 minutes after peripheral intravenous (IV) injection of 2 mg epinephrine. No other resuscitative drugs were administered during the study period. Mean PetCO2 decreased from 16.7 +/- 9.3 mm Hg before epinephrine to 12.6 +/- 7.1 mm Hg after epinephrine. The mean change in PetCO2 was 4.15 +/- 3.5 mm Hg (P < .0001). Four patients exhibited return of spontaneous circulation (ROSC). The decrease in PetCO2 was similar between the patients who exhibited ROSC and those who did not. There was a significant relationship between the epinephrine-induced change in PetCO2 and the PetCO2 value before epinephrine injection (r = .760; P < .0001). This study demonstrates a variable decrease in PetCO2 after IV epinephrine injection during CPR. Isolated PetCO2 readings may be misleading in assessing CPR efficacy or predicting outcome, and continuous measurement is recommended.

Midazolam/propofol but not propofol alone reversibly depress the swallowing reflex

General anaesthetics depress swallowing and this is a reason to delay oral intake after general anaesthesia. The swallowing reflex was studied 2 h after general anaesthesia for patients undergoing colonoscopy. Forty-one patients were anaesthetized with midazolam 75 micrograms.kg-1 followed by a continuous infusion of propofol and 39 patients with propofol 1.5 mg.kg-1 bolus followed by an infusion. Swallowing reflex was measured by electromyography 2 h after induction of anaesthesia, before and 5 min after the administration of flumazenil (0.2 mg) or placebo. Two h after anaesthesia, the state of consciousness was almost normal in all patients and did not change after flumazenil. At two hours, the latency times for the swallowing reflex in patients treated with propofol alone were of 1.4 +/- 0.4 s and were significantly shorter (P < 0.05) than the value of 1.9 +/- 0.8 s observed in patients who received midazolam with propofol. In the latter group the latency time of the swallowing reflex was significantly reduced following the administration of flumazenil but not placebo. In patients who received propofol without midazolam, the administration of flumazenil or placebo was not associated with significant changes in the latency times. There were also no significant differences in the latency times in the subgroup that received midazolam followed by flumazenil and the propofol alone groups that did or did not receive flumazenil. These results suggest that midazolam still exerts a depressive effect on the swallowing reflex 2 h after its administration despite the recovery of normal consciousness.