934
5.
6.
7.
8.
9.
10.
11.
12.
| Correspondence
single-penetration, double-injection approach. Br J Anaesth
2015; 115: 792–4
Pandit JJ, Dutta D, Morris JF. Spread of injectate with superficial cervical plexus block in humans: an anatomical study. Br J
Anaesth 2003; 91: 733–5
Valdes-Vilches LF, Sanchez-del Aguila MJ. Anesthesia for clavicular fracture: selective supraclavicular nerve block is the
key. Reg Anesth Pain Med 2014; 39: 258–9
Shin C, Lee SE, Yu KH, Chae HK, Lee KS. Spinal root origins
and innervations of the suprascapular nerve. Surg Radiol
Anat 2010; 32: 235–8
Supraclavicular nerve block. In: Gray AT, ed. Atlas of UltrasoundGuided Regional Anesthesia. Philadelphia: Saunders, 2013; 69–71
Burckett-St Laurent D, Chan V, Chin KJ. Refining the ultrasound-guided interscalene brachial plexus block: the superior trunk approach. Can J Anaesth 2014; 61: 1098–102
Canella C, Demondion X, Delebarre A, Moraux A, Cotten H,
Cotten A. Anatomical study of phrenic nerve using ultrasound. Eur Radiol 2010; 20: 659–65
Steinfeldt T, Schwemmer U, Volk T, et al. Nerve localization
for peripheral regional anesthesia. Recommendations of the
German Society of Anaesthesiology and Intensive Care Medicine. Anaesthesist 2014; 63: 597–602
Hanson NA, Auyong DB. Systematic ultrasound identification
of the dorsal scapular and long thoracic nerves during interscalene block. Reg Anesth Pain Med 2013; 38: 54–7
13. Gadsden JC, Choi JJ, Lin E, Robinson A. Opening injection
pressure consistently detects needle–nerve contact during
ultrasound-guided interscalene brachial plexus block.
Anesthesiology 2014; 120: 1246–53
14. Liu SS, YaDeau JT, Shaw PM, Wilfred S, Shetty T, Gordon M.
Incidence of unintentional intraneural injection and postoperative neurological complications with ultrasound-guided
interscalene and supraclavicular nerve blocks. Anaesthesia
2011; 66: 168–74
15. Cohen JM, Gray AT. Functional deficits after intraneural injectionduringinterscalene block.RegAnesth Pain Med 2010; 35: 397–9
16. Sites BD, Taenzer AH, Herrick MD, et al. Incidence of local anesthetic systemic toxicity and postoperative neurologic
symptoms associated with 12,668 ultrasound-guided nerve
blocks: an analysis from a prospective clinical registry. Reg
Anesth Pain Med 2012; 37: 478–82
17. Lin JA, Lee YJ, Lu HT, Lin YT. Ultrasound standard for popliteal
sciatic block: circular expansion of the paraneural sheath
with the needle in-plane from lateral-to-medial in the ‘reverse Sim’s’ position. Br J Anaesth 2015; (in press)
18. Lin JA, Nakamoto T, Yeh SD. Ultrasound standard for obturator nerve block: the modified Taha’s approach. Br J Anaesth
2015; 114: 337–9
19. Lin JA, Lu HT. A convenient alternative for monitoring opening pressure during multiple needle redirection. Br J Anaesth
2014; 112: 771–2
doi:10.1093/bja/aev384
Large increases in both response and state entropy to awake values
antagonized with administration of incremental rocuronium
A. Puttappa*, K. Sheshadri, J. Boylan and N. Conlon
Dublin, Republic of Ireland
*E-mail: [email protected]
Editor—Depth of anaesthesia (DOA) monitors use processed electroencephalogram (EEG) signals to calculate simple numerical
values to indicate adequacy of anaesthesia. Various extrinsic
and intrinsic factors affecting EEG signals may impair the reliability of these indices.
M-Entropy (GE Healthcare, Finland) indicates DOA through
two parameters, State Entropy (SE) and Response Entropy (RE).
SE is computed over the EEG dominant part of the frequency spectrum (0.8–32 Hz) reflecting the hypnotic component. RE covers
both the EEG and electromyogram (EMG) component of the spectrum (0.8–47 Hz).1 and is the faster reacting of the two parameters.
Increased RE values from EMG interference are not uncommon,
but theoretically SE values should not increase with EMG interference as the frequency spectrum reflects solely the EEG component. RE-SE difference has been variably reported to be a useful
indicator of facial EMG activation or antinociception.2–4
We report our observation of large increases in both RE and SE
to awake values under sevoflurane/rocuronium anaesthesia,
with complete return to deep anaesthesia values with administration of an incremental rocuronium dose.
A 71 yr old male (ASA status II) with carcinoma of the head
of the pancreas underwent a Whipple’s procedure in our
institution. Anaesthesia was induced with midazolam, fentanyl
and propofol. Tracheal intubation was facilitated with rocuronium. Anaesthesia was maintained with sevoflurane/fentanyl/
rocuronium, with target end-tidal sevoflurane of 1.4. Continuous
ECG, plethysmography, invasive bp, end-tidal carbon dioxide and
agent concentrations were monitored. DOA was monitored with
an M-Entropy module (GE Healthcare, Finland) and muscle relaxation was monitored with an NMT module (GE Health Care,
Finland). During the procedure we noted a sudden large increase
in RE and SE (Fig. 1) to awake values (97 and 85 respectively).
There were no autonomic signs of inadequate depth of anaesthesia
or analgesia with heart rate and bp remaining stable. Pupils
were small and central. The NMT monitor showed a train-of-four
(TOF) count of four. An incremental dose of rocuronium was administered and both RE and SE values decreased immediately to <40
(Fig. 2). This exact scenario was repeated several times during the
case. The patient reported no awareness postoperatively.
While an increase in RE can be as a result of EMG interference,
an increase in SE is universally considered to be because of an
increase in level of consciousness. Certainly a sudden increase in
both SE and RE indicates an increase in consciousness towards the
awake state until proved otherwise. Our case illustrates that this
Correspondence
| 935
Fig 2 Entropy response to muscle relaxation with rocuronium.
Fig 1 Increase in both Response entropy (RE) and State entropy (SE) with
wearing of muscle relaxation as indicated by Train-of-Four (TOF) ratio.
increase can in fact be because of EMG interference in the case of
both the RE and SE parameters and titration of anaesthetic agents
should not be based solely using these indices. This observed
artifact in the SE reading is probably because of the fact that
EMG activity contains some frequencies below 32 Hz.5 6
Declaration of interest
None declared.
References
1. Viertio-Oja H, Maja V, Sarkela M, et al. Description of the
entropy algorithm as applied in the Datex-Ohmeda S/5
Entropy Module. Acta Anaesthesiol Scand 2004; 48: 154–61
2. Mathews DM, Cirullo PM, Struys MM, et al. Feasibility study for
the administration of remifentanil based on the difference
between response entropy and state entropy. Br J Anaesth
2007; 98: 785–91
3. Liu N, Chazot T, Huybrechts I, Law-Koune JD, Barvais L,
Fischler M. The influence of a muscle relaxant bolus on bispectral and datex-ohmeda entropy values during propofol–
remifentanil induced loss of consciousness. Anesth Analg
2005; 101: 1713–8
4. Hans P, Giwer J, Brichant JF, Dewandre PY, Bonhomme V. Effect
of an intubation dose of rocuronium on spectral entropy and
bispectral indexTM responses to laryngoscopy during propofol
anaesthesia. Br J Anaesth 2006; 97: 842–7
5. Kawaguchi M, Takamatsu I, Kazama T. Rocuronium dosedependently suppresses the spectral entropy response to tracheal intubation during propofol anesthesia. Br J Anaesth 2009;
102: 667–72
6. Aho AJ, Lyytikainen LP, Yli-Hankala A, Kamata K, Jantti V.
Explaining Entropy responses after a noxious stimulus, with
or without neuromuscular blocking agents, by means of the
raw electroencephalographic and electromyographic characteristics. Br J Anaesth 2011; 106: 69–76
doi:10.1093/bja/aev385
The significant contribution of the partitioning effect in lipid
resuscitation for bupivacaine-induced cardiotoxicity: evaluation
using centrifuged solution in vivo and in isolated hearts
K. Hori*, T. Matsuura, S. Tsujikawa, T. Mori, M. Kuno and K. Nishikawa
Osaka, Japan
*E-mail: [email protected]
Editor—Lipid resuscitation is a standard rescue treatment
against local anaesthetic systemic toxicity, although the
underlying mechanism remains unclear.1–4 The partitioning effect, the trapping of lipophilic local anaesthetics into lipid