Block-Aid Monitor

WLMD ID: akiy
For general anesthesia, muscle relaxants are used to keep the entire body still during surgery. Peripheral nerve stimulators are used to determine the extent to which the drug has taken effect. They are used to stimulate a motor nerve with a mild electrical current, delivered through electrodes or needles, causing the related muscles to contract. The degree of this response is the most accurate guide to the extent of relaxation, called neuromuscular blockade. The English pharmaceutical company, Burroughs Wellcome, developed its Block-Aid Monitor around 1964. This device allowed either intermittent or continuous monitoring of nerve response throughout the surgery.  

Catalog Record: Block-Aid Monitor

Access Key: akiy
Accession No.: 2010-07-20-2 E

Title: ‘ Block-aid’ monitor.

Corporate Author: Burroughs Wellcome and Co.

Title variation: Alt Title
Title: Block-aid monitor.

Title variation: Alt Title
Title: Block aid monitor.

Publisher: Tuckahoe, NY: Burroughs Wellcome & Co.; [1964-1970].

Physical Descript: 1 peripheral nerve stimulator ; metals, plastics, glass : 7.5 x 8 x 17 cm.

Subject: Neuromuscular Monitoring – instrumentation.
Subject: Peripheral Nerve Stimulator.
Subject: Physical Examination – instrumentation.
Subject: Monitoring, Physiologic – instrumentation.
Subject: Neuromuscular Blocking Agents – history.
Subject: Electric Stimulation – instrumentation.

Note Type: General
Notes: The early year [1964] in the date range for the possible year of manufacture
is based on an article by Ronald L. Katz, MD, published in 1965, in which he
wrote, “Approximately one year ago a nerve stimulator (Block-Aid Monitor)
with these characteristics was developed and given to us for clinical testing
” (p. 832). The latest date (1970) in the date range for the possible year of
manufacture is based on the year that Burroughs Wellcome & Co. moved its
headquarters and manufacturing facility to North Carolina (Vogel, 1985).

Note Type: General
Notes: Block-Aid Monitor: an aid in the use of muscle relaxants during general
anesthesia. Tuckahoe, NY: Burroughs Wellcome & Co.; 1965:[1-8].

Note Type: Citation
Notes: Christie TH, Churchill-Davidson HC. The St. Thomas’s Hospital nerve
stimulator in the diagnosis of prolonged apnoea. Lancet. April 12,

Note Type: Citation
Notes: Churchill-Davidson HC. A portable peripheral nerve-stimulator. Anesthesiology

Note Type: Citation
Notes: Katz RL. A nerve stimulator for the continuous monitoring of muscle relaxant
action. Anesthesiology;26(6):823-833.

Note Type: Citation
Notes: Kopman AF. Neuromuscular monitoring: old issues, new controversies. J Crit
Care. 2009;24(1):11-20.

Note Type: Citation
Notes: Moore C. Burroughs Wellcome Fund. NCpedia website. https://ncpedia.
org/burroughs-wellcome-fund. Published 2006. Accessed September 11, 2013.

Note Type: Citation
Notes: Viby-Morgensen J. Neuromuscular monitoring. In: Miller RD, ed. Miller’s
anesthesia. 7th ed. Philadelphia: Churchill Livingston/Elsevier;

Note Type: Citation
Notes: Vogel EF. Comeback, Case by Case: Building the Resurgence of American
Business. New York: Simon and Schuster; 1985:254.

Note Type: Physical Description
Notes: One peripheral nerve stimulator (PNS) measuring approximately 7.5 in height,
8 cm wide and 17 cm deep; The body of the PNS is a rectangular metal box; It
is painted off-white with blue lettering; The controls are located on top,
with an indicator light nearest the side with the ports for the electrode
extensions; Below the indicator light are three controls; The control on the
left is an ON/OFF switch; The control in the center is a dial with unnumbered
graduations from a mark of “LO” to a mark of “HI”; The control on the right
is a switch to change modes from “TWITCH” to “TETANUS”; Below the controls
are manufacturer markings including, “‘BLOCK-AID’ [new line] MONITOR [new
line, the Burroughs Wellcome & Co. logo, and another new line] MADE FOR [new
line] BURROUGHS WELLCOME & CO. (U.S.A.) INC. [new line] TUCKAHOE, N.Y. [new
line] MADE IN U. S. A. [spaces] PAT PENDING”; A sticker below the outlets for
the electrode extensions reads, “NOT EXPLOSION PROOF [new line] PLACE 5 FEET
ABOVE FLOOR [new line] SEE LITERATURE”; Four round rubber ‘feet’ are located
in the corners of the bottom of the PNS.

Note Type: Reproduction
Notes: Photographed by Mr. Steve Donisch on January 17, 2013.

Note Type: Acquisition
Notes: Donated to the WLM by Bradley E. Smith, MD.

Note Type: Historical
Notes: The Block-Aid Monitor is a type of device called a ‘peripheral nerve
stimulator’ (PNS) or ‘neuromuscular monitor.’ These monitors are used by
anesthesiologists to evaluate their patients’ physiological response to
neuromuscular-blocking medications commonly called ‘muscle relaxants’. Muscle
relaxants are sometimes used for the safe insertion of breathing tubes or to
keep automatic muscle reflexes from interfering with surgery. Because the
effects of medications can vary from person to person, anesthesiologists
might use a neuromuscular monitor to assess the patient during anesthesia to
ensure that the patient has received enough medication, or after anesthesia
to verify that the medication’s effects have worn off.

The Block-Aid Monitor, introduced by Burroughs Wellcome & Company around 1965
worked by delivering small volts of electricity to a nerve, often in the
wrist. The anesthesiologist would watch and feel for certain muscle responses
This device could deliver electrical stimulation in two different modes via
electrodes on the skin or through very thin needles just under the skin.

The use of a peripheral nerve stimulator to monitor the effect of muscle
relaxants during and after anesthesia was first suggested in 1958. By 1965 at
least three models of PNS for clinical use were available. Since then,
research performed by a number of anesthesiologists has greatly informed how
PNSs may be used to optimize patient care. Newer devices can operate in a
number of different modes, and some provide operational feedback and record
the physiological responses, which anesthesiologists can use when evaluating

Note Type: Publication
Notes: Burroughs Wellcome & co. : products for use before, during and after
anesthesia and featuring the ‘block-aid’ monitor. Tuckahoe, N.Y.: Burroughs
Wellcome and Company; 1966.

Note Type: Publication
Notes: Kopman AF, Yee PS, Neuman GG. Relationship of the train-of-four fade ratio to
clinical signs and symptoms of residual paralysis in awake volunteers.
Anesthesiology. 1997 Apr;86(4):765-771.

Note Type: Publication
Notes: Ross WT. Comparison of three clinical peripheral-nerve stimulators.
Anesthesiology. 1970;32(2):155-157.

Note Type: Publication
Notes: Zeh DW, Katz RL. A new nerve stimulator for monitoring neuromuscular blockade
and performing nerve blocks. Anesth Analg. 1978;57(1):13-17.

Note Type: Exhibition
Notes: Chosen for the WLM website (noted September 2, 2013).