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In the past few years progress has been made in understanding the
mechanisms and pathways involved in the modulation of pain, as well as in
developing new therapeutic tools to provide satisfactory pain relief after
surgery. The relationship between the intensity of acute postoperative pain
and the duration of the patient's recovery and functional outcome has been
well established. For these reasons, the prevention and treatment of acute
pain had become the focus of great interest for perioperative specialists.
Postoperative pain differs from chronic pain by its shorter duration and its
requirement for immediate relief, which dictate the development of suitable
management protocols. Preemptive and preventive analgesia also represent
concepts that only apply to acute postoperative pain. Finally, it is
important to recognize the role of acute pain in the development of chronic
pain syndrome.
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Irrespective of its nature, pain is not an objective but rather a
subjective symptom. In the surgical as well as medical environment,
intrinsic and extrinsic factors affect individual pain thresholds.
Accordingly, the clinician must be always aware that pain treatment must be
approached using a multimodal and multipharmacologic approach; no one single
technique by itself, including the use of continuous peripheral nerve block,
provides adequate pain relief in all patients and in all circumstances. The
first description of continuous peripheral nerve block was reported in 1946
by Paul Ansbro,1 who described the placement at the
supraclavicular level of a blunt needle secured to the patient's skin using
a cork, through which the needle was inserted before block placement. This
cumbersome apparatus allowed the incremental injection of local anesthetic
in order to prolong the duration of anesthesia in patients undergoing upper
extremity surgery. In their report the authors used a
short-onset/intermediate-duration local anesthetic, like 1% procaine.
After an initial 40-mL bolus the authors injected incremental doses based on
the duration of surgery, up to a final volume ranging between 120 mL for
1.5-h surgery and 220 mL for 4-h surgery. During the following 3 decades
continuous perineural infusion techniques continued to be developed, and
their indications extended; initially they were mainly used for upper
extremity blocks, afterward they were also employed for lower limb blocks.
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In 1977 Selander2 reported on the injection of 30 to 50 mL
of mepivacaine to conduct a continuous axillary block in 137 patients
undergoing hand surgery, and in 1979 Manriquez and
Pallares3 reported on the repeated injection of 20 mL of
0.25% bupivacaine every 6 h to prolong the sympathetic block and pain
control for 4 days.
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In 1982 Matsuda and colleagues4 reported on the use of
either 30 mL of 1% lidocaine with epinephrine followed by 15 mL
intermittently (1.5–2.75 h) or 40 mL of a 0.5% bupivacaine and 1%
lidocaine mixture followed by intermittent injection of 20 mL (1.25–4.3 h)
in 50 patients undergoing upper extremity reimplantation. Subsequently most
of the groups have focused their clinical protocols on the use of low
concentrations ...