Surgical pleth index: prediction of postoperative pain in children?

Background

Surgical Pleth Index (SPI) is a non-invasive, dimensionless score (0-100) aimed to allow an estimate of intraoperative nociception. Thus, it may be a useful tool to guide intraoperative analgesia. However, no optimum SPI target range for the use in children has yet been defined. It was the aim of this study to define a clinically appropriate SPI target to predict moderate-severe postoperative pain in children.

Methods

After ethics approval 105 children (2-16 yr) undergoing elective sevoflurane/opioid-based anaesthesia were included. SPI was recorded directly before the end of surgery and compared with acute postoperative pain (age appropriately assessed on different pain scales in the age groups two to three yr, four to eight yr and nine to16 yr) in the postoperative acute care unit (PACU).

Results

Data of 93 children were analysed. A significant negative correlation was found between age and SPI (r=-0.43; P=0.03). The SPI cut-off value with the highest sensitivity (76%) and specificity (62%) in all children combined was 40. The negative predictive value for SPI ≤ 40 to predict the absence of moderate-severe pain in PACU was 87.5%. The commonly used SPI cut-off (50) published in all related studies had neither any clinically relevant sensitivity nor specificity to predict the presence or absence of acute pain in PACU.

Conclusions

The results suggest that a lower (≤ 40) than previously published (50) target for SPI may be more appropriate in studies investigating SPI guided anaesthesia in children, if the avoidance of moderate-severe postoperative pain is the main goal.

Clinical trial registration

ACTRN12616001139460.

Surgical pleth index: prediction of postoperative pain and influence of arousal

BACKGROUND

There are conflicting reports concerning the outcome after anaesthesia guided by the surgical pleth index (SPI; GE Healthcare, Helsinki, Finland). One potential explanation may be the lack of evidence for the selection of SPI cut-off values. The aim of this trial was to investigate the correlation between SPI, arousal, and postoperative pain and to define a cut-off value for SPI to predict moderate-to-severe pain.

METHODS

After obtaining ethical approval and written informed consent, 70 patients undergoing non-emergency surgery were enrolled. Data relating to SPI, heart rate, mean arterial pressure, and state entropy were recorded every 10 s for the last 10 min of surgery (state entropy <60 at all times). Subsequently, recordings continued during the phase of arousal. After recovery room admission, pain scores (numerical rating scale 0-10) were obtained every 3 min for 15 min.

RESULTS

Data from 65 patients were analysed. Receiver-operating characteristic curve analysis revealed an optimal intraoperative cut-off SPI value of 30 to discriminate between numerical rating scale scores 0-3 and 4-10. For this value, the negative and positive predictive values to discriminate between numerical rating scale scores 0-3 and 4-10 were 50 and 89.7%, respectively. The SPI was significantly affected by arousal, and SPI scores obtained during this phase were not predictive of postoperative pain.

CONCLUSIONS

Surgical pleth index values are predictive of postoperative pain only if obtained before patient arousal. In contrast to previous studies, a relatively low SPI, >30, appears to predict pain with a high positive predictive value and may therefore be suggested for future studies of SPI-guided anaesthesia.

CLINICAL TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12615000804583.

The effect of deep muscle relaxation on the force required during Latissimus Dorsi dissection for breast reconstructive surgery: results of a prospective, double-blinded observational pilot study

BACKGROUND

The use of neuromuscular blocking agents has previously been suggested to facilitate the dissection of the latissimus dorsi muscle during breast reconstructive surgery. The aim of this study was to quantify the influence of deep muscle relaxation on the force required to lift the latissimus dorsi muscle during flap preparation.

METHODS

After ethics approval and written informed consent 15 patients scheduled for elective breast reconstruction with a latissimus dorsi pedicled flap (muscle flap, not myocutaneous flap) under general anaesthesia were prospectively included. Midway through the muscle dissection a sterile cotton tape was slung around the mid portion of the muscle and connected with a sterile strain gauge stably positioned just above the patient. Thereafter, the muscle was lifted by moving the strain gauge vertically upwards until a muscle tension similar to that created manually during muscle dissection was achieved. The force (N) and distance required to tension the muscle were recorded and the tension released. In a randomized and blinded crossover design either rocuronium (0.6 mg.kg-1) or normal saline were given intravenously, and the tension protocol was repeated 2 min after each drug administration.

RESULTS

Muscle relaxation significantly reduced the force for flap tensioning (median [percentiles] - 22 [-32/-13] %; P = 0.011) in 10/15 patients. However, in the remaining 5 patients no significant effect was measured. Normal saline had no effect on the measured force.

CONCLUSIONS

Deep muscle relaxation significantly reduces the force required to manually elevate the latissimus dorsi muscle during its dissection in the majority of but not all patients.

TRIAL REGISTRATION

The study was retrospectively registered on [17.6.2014] with the Australian and New Zealand Clinical Trials Registry. ACTRN12614000637640.

Sugammadex: What do we Know and What do we Still Need to Know? A Review of the Recent (2013 to 2014) Literature

Since its launch in 2008, sugammadex has been considered one of the most significant developments in anaesthesia-related pharmacology. With almost 500 sugammadex-related publications and over nine million patient exposures worldwide, user experience and scientific data have grown exponentially. However, several important questions are yet to be answered. This article reviews the sugammadex-related literature in 2013 and 2014 to determine which of these questions have been answered more fully over the last 18 months and which questions require more information and research.

Unrestricted access to sugammadex: impact on neuromuscular blocking agent choice, reversal practice and associated healthcare costs

Sugammadex is known to rapidly and completely reverse the effects of amino-steroidal neuromuscular blocking agents. However, the high costs of sugammadex have so far prevented its introduction as the standard reversal agent in most healthcare systems. At the Royal Perth Hospital, sugammadex was recently introduced as an unrestricted alternative to neostigmine for the reversal of amino-steroidal neuromuscular blocking agents. The aim of this retrospective observational audit was to investigate the impact of this change on clinical practice and associated healthcare costs. Data from all patients intubated during a one-month period in April to May 2010 and for a similar period in 2011 were retrospectively collected and the use of neuromuscular blocking agents and reversal agents were identified and the associated costs were calculated. More steroidal neuromuscular blocking agents and sugammadex (+743%), but less glycopyrrolate and neostigmine (-48%) were used in 2011. Using the manufacturer's list price, muscle relaxation and reversal costs increased from about A$42 per case to about A$127 per case. Between the investigated time periods no differences were found for anaesthesia time, operating time or time spent in the post anaesthesia care unit. However, there was a statistically significant decrease in the time between surgery and discharge (median 2.0 vs 2.2 days). While the design of the audit was such that no inferences can be made about the cause of this change, this is an interesting observation worthy of further investigation.

Successful use of Rocuronium and Sugammadex in an Anticipated Difficult Airway Scenario

Neuromuscular blocking agents are often avoided in anticipated difficult airway scenarios. However, to facilitate jet ventilation, muscle relaxants are useful. We report a case of a potentially threatened airway in a 21-year-old with a large infraglottic pedunculated polyp. In this case rocuronium was used on induction to facilitate subsequent jet ventilation and periglottic laser ablation of the tumour. As the duration of the surgery was not predictable, the intention was to use sugammadex at the end to ensure complete reversal of muscle relaxation. This strategy also provided a quick rescue option if there was a sudden loss of the airway.

Skin conductance as a means to predict hypotension following spinal anaesthesia

BACKGROUND AND OBJECTIVE

Hypotension following spinal anaesthesia (SA) is common, especially in the elderly. Elevated sympathetic tone has been shown to correlate with severe hypotension after SA. The aim of this prospective trial was to investigate skin conductance (SC), as a measure of sympathetic tone, to predict hypotension after SA.

METHODS

After ethical approval and written informed consent, 30 patients undergoing SA were included. Baseline measurements of SC [number of fluctuations per second (reflecting the firing rate of skin sympathetic nerves), area under the curve (AUC) A and B (reflecting the magnitude of the sympathetic impulse)], blood pressure and heart rate were recorded. After administration of SA, all parameters were assessed every 2.5 min for a total of 15 min. Baseline readings of SC were compared with the lowest blood pressure within the study period.

RESULTS

Data from 30 subjects [73 (8) years] were analysed. After SA, the mean arterial blood pressure declined an average of 21.3 (11.3) mmHg. A cut-off value of 0.35 microSs for baseline AUC B allowed prediction of more than mild hypotension (>15% from baseline) after SA with a sensitivity of 72.5% and a specificity of 77.5%.

CONCLUSIONS

AUC B, as a parameter of SC, may predict severe arterial hypotension after SA in the elderly.

Changes in heart rate variability may reflect sympatholysis during spinal anaesthesia

BACKGROUND

To investigate if changes in low-to-high frequency ratio (LF/HF), low frequency (LF) and high frequency (HF) heart rate variability reflect autonomic regulation during spinal anaesthesia (SA) in pregnant women scheduled for elective Caesarean section.

METHODS

Prospective clinical trial. Systolic blood pressure (SBP) and heart rate variability were analysed at baseline, 5 min after SA and 15 min after SA. Patients were assigned by baseline LF/HF. Group LF/HF < 2.5 (n= 52) was compared to group LF/HF > 2.5 (n= 48). Non-parametric tests for statistical analysis.

RESULTS

Group LF/HF > 2.5 showed a significant decrease in LF/HF and LF as well as an increase in HF during SA (median, range): baseline LF/HF [4.0 (3.2/4.8)] decreased to 2.3 (1.3/3.4) at event 15 min after SA (P < 0.001). Baseline LF = 59(43/71)% decreased to 40 (27/55)% at event 15 min after SA (P < 0.05). Baseline HF = 15(13/22)% increased to 26(15/41)% at event 15 min after SA (P < 0.05). In contrast, group LF/HF < 2.5 demonstrated only moderate changes in LF/HF, LF and HF during SA. SBP decreased significantly in group LF/HF > 2.5 (median and range) lowest SBP group LF/HF > 2.5: 80 (50/127 mmHg vs. group LF/HF < 2.5: 109 (104/142) mmHg, P < 0.001. Decrease of SBP before and after SA was correlated with a decrease in LF/HF, LF, and HF, respectively: LF/HF - SBP: r= 0.30, r(2)= 0.09, P < 0.001; LF - SBP: r= 0.25, r(2)= 0.06, P < 0.05, HF, NS.

CONCLUSIONS

Changes in heart rate variability parameters in the course of SA may reflect a decrease in sympathetic activity and relative increase in parasympathetic activity as a result of the block. In the course of SA, the more pronounced the changes in heart rate variability were the more distinct the hypotension.

The assessment of postoperative pain by monitoring skin conductance: results of a prospective study

The number of fluctuations of skin conductance per second correlates with postoperative pain. The aim of this prospective study was to test the cut-off value for the number of fluctuations of skin conductance per second obtained from a previous study. Seventy-five patients were asked to quantify their level of pain on a numeric rating scale (0-10) in the recovery room. The number of fluctuations of skin conductance per second was recorded simultaneously. The number of fluctuations of skin conductance per second was different between patients with no (0.07), mild (0.16), moderate (0.28) and severe pain (0.33); p < 0.001. The tested cut-off value for the number of fluctuations of skin conductance per second (0.1) distinguished a numeric rating scale </= 3 from > 3 with 88.5% sensitivity and 67.7% specificity. The number of fluctuations of skin conductance per second may be a useful means of assessing postoperative pain.

New parameters of skin conductance compared with bispectral index ® monitoring to assess emergence from total intravenous anaesthesia

BACKGROUND

Arousal after total i.v. anaesthesia (TIVA) has been reported to be detectable by monitoring the number of fluctuations per second (NFSC), a parameter of skin conductance (SC). However, compared with monitoring of the bispectral index (BIS), the predictive probability of NFSC was significantly lower. The aim of this study was to determine the value of the two new, not yet published parameters of SC, area under the curve (AUC) methods A and B, for monitoring emergence from TIVA compared with monitoring of NFSC and BIS.

METHODS

Twenty-five patients undergoing surgery were investigated. NFSC, AUC A, AUC B, BIS, and haemodynamic parameters (mean arterial pressure and heart rate) were recorded simultaneously. The performance of the monitoring devices in distinguishing between the clinical states 'steady-state anaesthesia', 'first clinical reaction', and 'extubation' were compared using the method of prediction probability (Pk) calculation.

RESULTS

BIS showed the best performance in distinguishing between 'steady-state anaesthesia' vs 'first reaction' (Pk BIS 0.95; NFSC 0.73; AUC A 0.54; AUC B 0.62) and 'steady-state anaesthesia' vs 'extubation' (Pk BIS 0.99; NFSC 0.73; AUC A 0.71; AUC B 0.67). However, the time from first BIS>60/SC>0 to a first clinical reaction was significantly shorter for BIS (median BIS((R)) 180 s; NFSC 780 s; AUC A 750 s; AUC B 690 s; P < 0.001).

CONCLUSIONS

AUC A and AUC B did not improve accuracy of SC monitoring in patients waking after TIVA.

Monitoring of skin conductance to assess postoperative pain intensity

BACKGROUND

Pain is known to alter the electrogalvanic properties of the skin. The aim of this pilot study was to investigate the influence of postoperative pain on skin conductance (SC) readings.

METHODS

After obtaining ethical approval and written informed consent, 25 postoperative patients were asked to quantify their level of pain on a numeric rating scale (NRS, 0-10) at different time points in the recovery room. As a parameter of SC, the number of fluctuations within the mean SC per second (NFSC) was recorded. Simultaneously, the NRS was obtained from patients by a different observer who was blinded to the NFSC values.

RESULTS

Data from 110 readings of 25 patients (14 female, 11 male; 21-67 yr) were included. NFSC showed a significant correlation with the NRS (r=0.625; P<0.01), whereas heart rate and blood pressure showed no or very weak correlation with the NRS. NFSC was significantly different between patients with no (NRS=0), mild (NRS=1-3), moderate (NRS=4-5) and severe (NRS=6-10) pain (no: 0.047, mild: 0.089, moderate: 0.242, severe: 0.263; P<0.0001). Post hoc, a cut-off value for NFSC (0.1) was calculated above which a pain score >3 on the NRS was predicted with sensitivity of 89% and specificity of 74%.

CONCLUSIONS

The severity of postoperative pain significantly influences SC. Using cut-off values, NFSC may prove a useful tool for pain assessment in the postoperative period.

Skin conductance monitoring compared with Bispectral Index to assess emergence from total i.v. anaesthesia using propofol and remifentanil

BACKGROUND

Arousal after sevoflurane anaesthesia has been detectable by monitoring changes in skin conductance (SC) with similar accuracy as monitoring Bispectral Index (BIS). As SC monitoring detects changes in sympathetic tone, the measurements might be confounded by the sympatholytic properties of propofol, a component of total i.v. anaesthesia (TIVA). Therefore in this study, monitoring of SC during emergence from TIVA was compared with the monitoring of BIS.

METHODS

Twenty-five patients undergoing plastic surgery were investigated. The number of fluctuations of SC per second (NFSC), BIS and haemodynamic variables [systolic blood pressure (SBP) and heart rate (HR)] were recorded simultaneously. The performance of the monitoring devices in distinguishing between the clinical states 'steady-state anaesthesia', 'first clinical reaction' and 'extubation' were compared using the method of prediction probability (Pk) calculation.

RESULTS

BIS((R)) showed the best performance in distinguishing between 'steady-state anaesthesia' and 'first reaction' (Pk BIS 0.99 vs NFSC 0.80; P<0.01), and 'steady-state anaesthesia' and 'extubation' (Pk BIS) 1.00 vs NFSC 0.91; P<0.05); the time from first change of BIS or NFSC to a first clinical reaction was significantly longer for NFSC (median BIS 135 s vs NFSC 191 s; P<0.05). BIS and NFSC performed better in distinguishing between the investigated clinical states than SBP and HR.

CONCLUSIONS

In this study, BIS was found to predict arousal with a higher probability but slower response times than NFSC in patients waking after TIVA.

Bronchial mucus transport velocity in patients receiving anaesthesia with propofol and morphine or propofol and remifentanil

In vitro morphine does not reduce cilia beat frequency, a key factor determining bronchial mucus transport velocity. There are no reports about the effect of remifentanil on bronchial mucus transport. We compared the bronchial mucus transport velocity in patients having total intravenous anaesthesia with either propofol and morphine, or propofol and remifentanil. Twenty patients scheduled for elective surgery were randomly allocated to the two groups. Fifteen minutes after insertion of the laryngeal mask airway, bronchial mucus transport velocity was assessed by fibreoptic observation of the movement of methylene blue dye applied to the right main bronchus. Compared with morphine, bronchial mucus transport velocity was significantly reduced in patients receiving remifentanil (morphine mean (SD) 9.2 (5.8) vs remifentanil 4.2 (3.0) mm.min(-1), p = 0.028). Anaesthesia with remifentanil may lead to significantly impaired bronchociliary clearance in comparison to morphine. This could have clinical implications, in particular in patients at risk.

Skin conductance monitoring compared with bispectral index ® monitoring to assess emergence from general anaesthesia using sevoflurane and remifentanil

BACKGROUND

Changes in skin conductance have previously been reported to correlate well with plasma levels of stress hormones and awakening stimuli. In this study, monitoring of skin conductance during emergence from general anaesthesia was compared with the monitoring of bispectral index (BIS).

METHODS

Twenty-five patients undergoing minor elective surgery were investigated. The number of fluctuations in mean skin conductance (NFSC), BIS and haemodynamic parameters were recorded simultaneously. The performance of the monitoring devices to predict and distinguish between the clinical states 'steady-state anaesthesia', 'first reaction' and 'extubation' were compared using the method of prediction probability (P(K)) calculation.

RESULTS

Both monitors showed similar performance in distinguishing between 'steady-state anaesthesia' vs 'first reaction' (P(K) NFSC 0.89; BIS 0.94) and 'steady-state anaesthesia' vs 'extubation' (P(K) NFSC 0.96; BIS 0.96). The response times of the monitors, to indicate the likelihood of 'first reaction', were not significantly different.

CONCLUSIONS

NFSC, as a parameter of skin conductance, performed similarly to BIS in patients waking after a general anaesthetic.

Pseudocholinesterase activity increases and heart rate variability decreases with preoperative anxiety

BACKGROUND AND OBJECTIVE

The objective of this study was to determine the influence of preoperative anxiety on the activity of plasma cholinesterase and heart rate (HR) variability.

METHODS

A total of 50 subjects were studied, 25 male patients one day preoperatively and 25 male volunteers without surgical intervention as a control group. Blood samples were taken to determine plasma cholinesterase activity. HR variability was recorded for a period of 256 beat-to-beat intervals and analysed by frequency domain analysis into very low frequency (VLF: 0.02-0.04 Hz), low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-0.4 Hz). LF/HF ratio and total power over the 0.02-0.4 Hz range were calculated. Anxiety levels were assessed using the hospital anxiety and depression scale, the self-rating anxiety scale and a visual analogue scale.

RESULTS

The patient group had significantly higher anxiety scores. Plasma cholinesterase activity was significantly higher in patients vs. controls (6646 vs. 5324 units L(-1)). Total power, LF and HF were significantly lower in the patients (1489 vs. 2581 ms2; 656 vs. 1186 ms2; 491 vs. 964 ms2, respectively).

CONCLUSIONS

Preoperative anxiety increases plasma cholinesterase activity and decreases HR variability.

Neuromuscular block and relative concentrations of mivacurium isomers under isoflurane versus propofol anaesthesia

BACKGROUND AND OBJECTIVE

The augmentation of the effect of neuromuscular blocking drugs with volatile anaesthetics is well documented, but the mechanism remains unclear. The pharmacological interaction and relative plasma concentrations of mivacurium isomers were investigated during either propofol- or isoflurane-maintained anaesthesia.

METHODS

Forty-four patients were randomly assigned to one of two groups: isoflurane or propofol. All patients received an initial dose of mivacurium 0.1 mg kg(-1). After recovery of the first twitch (T1) response measured by acceleromyography to 5%, a T1 depression of 90-99% was maintained by infusion. After a steady state was reached, blood samples were taken after 10 and 30 min for analysis of mivacurium isomers. Recovery times for T1 to 251/50/75/90% (TW25-90), train-of-four ratio 25/70% and recovery index (time TW25-75) were recorded after stop of infusion.

RESULTS

In the isoflurane group, lower infusion rates were needed (3.0 +/- 1.6 versus 3.6 +/- 1.6 microg kg(-1) min(-1)) and there was a slower recovery (significant for train-of-four ratio 70%: 21.9 versus 17.9 min). The plasma concentrations of mivacurium and its trans-trans isomer (in percentage of the total) were significantly higher in the isoflurane group (10 min: 52.6 versus 25.8%; 30 min: 49.6 versus 23.2%).

CONCLUSIONS

For mivacurium, the phenomenon of 'potentiation' of the effect of muscle relaxants by volatile anaesthetics could be due to an increase in the plasma concentration of the potent trans-trans isomer.

The influence of fentanyl vs. s-ketamine on intubating conditions during induction of anaesthesia with etomidate and rocuronium

BACKGROUND AND OBJECTIVE

In the present study, we investigated the combination of etomidate and s-ketamine with regard to its suitability for modified rapid-sequence induction using rocuronium for muscle relaxation.

METHODS

In a prospective, randomized and double-blinded study, 90 patients were assigned to one of three groups for induction of anaesthesia in combination with etomidate (0.3 mg kg-1) and muscle relaxation with rocuronium (0.6 mg kg-1). The groups were as follows: (a) control, i.e. placebo; (b) fentanyl, fentanyl (1.5 microg kg-1); (c) ketamine, s-ketamine (0.5 mg kg-1). Tracheal-intubating conditions after 1 min were classified as excellent, good or poor. During the induction of anaesthesia, arterial pressure and heart rate were measured every 60 s.

RESULTS

Intubating conditions were best using etomidate and s-ketamine (23 excellent, 7 good, 0 poor) compared with the control (8, 16, 6 respectively) and fentanyl groups (7, 21, 2 respectively) (P < 0.01). While heart rate and arterial pressure remained stable in the control and fentanyl groups during induction, both significantly increased in the ketamine group (P < 0.01).

CONCLUSIONS

The combination of etomidate and s-ketamine for anaesthesia induction produces mostly excellent intubating conditions after 60 s using only 0.6 mg kg-1 of rocuronium. This combination of drugs may be a useful alternative, if succinylcholine needs to be avoided, for modified rapid-sequence induction.

Minimum local analgesic dose of plain ropivacaine vs. ropivacaine combined with sufentanil during epidural analgesia for labour

We have used the up-and-down allocation technique to assess the relative analgesic potencies of epidural ropivacaine alone and ropivacaine combined with sufentanil 0.75 microg.ml-1 in 42 women requesting epidural analgesia in the first stage of labour. Parturients were randomly allocated to one of the two epidural solutions in a double-blind manner. The concentration of local anaesthetic was determined by the response of the previous parturient: an effective concentration (pain < or = 10 mm on a 10-cm visual analogue pain score within 30 min) resulted in a 0.01% decrease in the concentration of ropivacaine for the next parturient, an ineffective concentration resulted in a 0.01% increase. Minimum local analgesic concentration of ropivacaine alone was 0.13% (95% CI 0.12-0.13%) compared with 0.09% (95% CI 0.08-0.1%) for ropivacaine with sufentanil (p < 0.00001).

[Augmentation of the neuromuscular blocking effect of mivacurium during inhalation anesthesia with desflurane, sevoflorane and isoflurane in comparison with total intravenous anesthesia]

To evaluate the enhancement of mivacurium-induced neuromuscular block by potent inhalational anaesthetic agents, dose-effect curves for mivacurium were determined in 84 patients scheduled for minor elective surgery during anaesthesia with 1.5 MAC (70% N2O) desflurane, sevoflurane and isoflurane and compared with those under total intravenous anaesthesia (TIVA). Acceleromyography (TOF-Guard) and train of four (TOF) stimulation of the ulnar nerve were used (2 Hz every 12 s). Mivacurium was administered in increments of 25 micrograms kg-1 until a depression of T1 > 95% was reached. ANOVA was used for statistical analysis (alpha = 0.05, beta = 0.2). The depression of T1 during potent inhalational anaesthesia was enhanced compared with TIVA. The ED50 and ED95 of mivacurium were 27 +/- 11 (SD) and 58 +/- 26 micrograms kg-1 for desflurane; 28 +/- 10 and 64 +/- 23 micrograms kg-1 for sevoflurane; and 27 +/- 13 and 55 +/- 27 micrograms kg-1 for isoflurane and were significantly lower than the 35 +/- 7 and 71 +/- 20 micrograms kg-1 for TIVA. The duration 25% revealed a significant difference between the volatile anaesthetic groups (10 +/- 2, 11 +/- 3, 11 +/- 3 min respectively) and the TIVA control group (8 +/- 3 min). The recovery index 25/75 and TOFO.80 were significantly prolonged by desflurane, sevoflurane and isoflurane compared with TIVA (RI25/75 9 +/- 4, 9 +/- 4, 10 +/- 5 respectively vs. 5 +/- 2 min; TOFO.80 27 +/- 10, 28 +/- 9, 29 +/- 9 respectively vs. 18 +/- 4 min). We conclude that the neuromuscular blocking effect of mivacurium is enhanced during anaesthesia with desflurane, isoflurane and sevoflurane compared with TIVA. The duration of action and the recovery time are prolonged. The dose of mivacurium used should be reduced if anaesthesia is maintained with volatile anaesthetics.

Neuromuscular blocking effects of rocuronium during desflurane, isoflurane, and sevoflurane anaesthesia

PURPOSE

To determine the magnitude of the potentiation of rocuronium by desflurane, isoflurane and sevoflurane 1.5 MAC anaesthesia.

METHODS

In a prospective, randomised, study in 80 patients, the cumulative dose-effect curves for rocuronium were determined during anaesthesia with desflurane, sevoflurane and isoflurane (with N2O 70%, 15 min steady state) or total intravenous anaesthesia (TIVA) using propofol/fentanyl. Neuromuscular block was assessed by acceleromyography (TOF-Guard) after train-of-four (TOF) stimulation of the ulnar nerve (2 Hz every 12 sec, 200 microseconds duration). Rocuronium was administered in increments of 100 micrograms.kg-1 until first twitch (T1) depression > 95%.

RESULTS

Rocuronium led to more pronounced T1 depression with desflurane or sevoflurane anaesthesia than with TIVA. The ED50 and ED95 were lower during desflurane (95 +/- 25 and 190 +/- 80 micrograms.kg-1) and sevoflurane (120 +/- 30 and 210 +/- 40 micrograms.kg-1) than with TIVA (150 +/- 40 and 310 +/- 90 micrograms.kg-1) (P < .01), while the difference was not significant for isoflurane (130 +/- 40 and 250 +/- 90 micrograms.kg-1). Following equi-effective dosing (T1 > 95%) the duration to 25% T1 recovery, recovery index (25/75), and TOF0.70 was: 13.2 +/- 1.8, 12.7 +/- 3.4, and 26.9 +/- 5.7 min during anaesthesia with desflurane; 15.5 +/- 5.0, 11.4 +/- 3.8, and 31.0 +/- 6.0 min with sevoflurane; 13.9 +/- 4.7, 10.7 +/- 3.3, and 26.3 +/- 8.9 min with isoflurane; and 13.9 +/- 3.9, 11.3 +/- 5.7, and 27.5 +/- 8.2 min with TIVA anaesthesia (P: NS).

CONCLUSION

Interaction of rocuronium and volatile anaesthetics resulted in augmentation of the intensity of neuromuscular block but did not result in significant effects on duration of or recovery from the block.

Augmentation of the neuromuscular blocking effects of cisatracurium during desflurane, sevoflurane, isoflurane or total i.v. anaesthesia

We have evaluated the enhancement of cisatracurium-induced neuromuscular block by potent inhalation anaesthetic agents, by constructing dose-effect curves for cisatracurium in 84 patients during anaesthesia with 1.5 MAC (70% nitrous oxide) desflurane, sevoflurane, isoflurane or total i.v. anaesthesia (TIVA). Acceleromyography (TOF-Guard) and train-of-four (TOF) stimulation of the ulnar nerve were used (2 Hz every 12 s). Cisatracurium was administered in increments of 15 micrograms kg-1 until depression of T1/T0 > 95% was reached. ANOVA was used for statistical analysis (alpha = 0.05, beta = 0.2). Depression of T1/T0 during potent inhalation anaesthesia was enhanced compared with TIVA. ED50 and ED95 values of cisatracurium were 15 (SD 5) and 34 (10) micrograms kg-1 for desflurane; 15 (4) and 32 (7) micrograms kg-1 for sevoflurane; and 15 (5) and 33 (9) micrograms kg-1 for isoflurane. These were significantly lower than the values for TIVA (21 (4) and 51 (13) micrograms kg-1) (P < 0.01 in each case). After equi-effective dosing, times to T1/T0 = 25% were similar in all groups (19 (7), 19 (5), 20 (5) vs 16 (4) min). Recovery index25-75% and time to a TOF ration of 0.70 were prolonged significantly by desflurane and sevoflurane compared with TIVA (18 (5), 19 (8) vs 12 (4) min and 43 (11), 44 (10) vs 35 (5) min, respectively), whereas the difference was not significant for isoflurane (14 (6) and 41 (7) min).