PSOAS COMPARTMENT BLOCK: LOWER EXTREMITY BLOCKADE FOR PATIENTS ON LOW MOLECULAR WEIGHT HEPARIN
Danett Maples, MD
Dept of Anesthesiology, University of Florida
Introduction: Psoas compartment blocks are indicated for
operations involving the hip, thigh, and upper leg in cases
where a regional technique is desirable and where, for some
reason, a spinal or epidural anesthetic is contraindicated.
Case Presentation: J.M. is a 73-year-old white gentleman who
fractured his left hip and several ribs on his left side after
he fell in a parking lot. His past medical history is
significant for severe COPD, requiring home oxygen therapy and
chronic steroids, intermittent atrial fibrillation,
hypertension, gastroesophageal reflux disease, depression and
benign prostatic hypertrophy. Due to the patients poor
respiratory status he required optimization of pulmonary
function with intravenous steroids, beta agonists, and
antibiotics prior to surgery on his left hip. The patient was on
low molecular weight heparin (LMWH), lovenox, 30 mg
subcutaneously twice a day, for deep vein thrombus prophylaxis
during the time prior to his surgery. The anesthestic was
managed with a left psoas compartment block because of the
patients significant past medical history and preoperative use
of LMWH. The patient underwent a left psoas compartment block
with 25 ml of 1% ropivicaine as the primary anesthetic technique
for his left hip open reduction and internal fixation with
excellent results.
Technique: After placing an intravenous catheter and basic
monitoring, the patient is placed in the lateral position with
the operative limb uppermost and the thigh flexed at the trunk.
The approach to the psoas compartment, first described by Winnie
and later modified by Dalens, uses the iliac crests and the
posterior superior iliac spine as landmarks. A Teflon coated
stimulating needle is introduced perpendicularly to all
cutaneous planes at the intersection of a transverse line,
between the upper border of the iliac crests, and a longitudinal
line parallel to the spine through the posterior superior iliac
spine. Movements of the quadriceps femoris are used to identify
the lumbar plexus using a nerve stimulator. The stimulus is
titrated from an initial stimulus of 1 mA to a final stimulus
between 0.3 and 0.5 mA at 1 Hz. Local anesthetic is then
injected after negative aspiration at a volume of 25 to 30 ml.
Discussion: Strict guidelines have been recommended for the use
of low molecular weight heparin and neuroaxial blockade because
of the risk, estimated to be 1:3,000 patients, of spinal
hematoma. (1) No such guidelines have been developed for
peripheral nerve blockade. There has been one reported case of a
retroperitoneal hematoma in a patient who underwent psoas
compartment block while receiving prophylactic LMWH. (2) The
patient developed a femoral nerve paresis postoperatively that
resolved over three months. Thus the risk/ benefit ratio for
patients requiring LMWH prophylaxis and lower extremity
anesthesia/analgesia is heavily weighted towards psoas
compartment block versus continuous epidural. Other advantages
of psoas compartment block compared to epidural block include
unilateral lower extremity block, lack of complete sympathectomy,
avoidance of urinary retention, and flexible postoperative pain
management schemes.
Conclusion: Psoas compartment blocks offer several advantages
over spinal or epidural anesthesia. The risk/benefit ratio in
patients requiring LMWH prophylaxis favors psoas compartment
block over epidural block. These unique advantages make the
psoas compartment block the anesthetic of choice for selected
patients.
References:
1.Schroeder DR. Statistics: Detecting a rare adverse drug
reaction using spontaneous reports. RAPM 1998:23(6) Suppl
2:183-189.
2. Klein SM, D'ErcoleF, Greengrass RA, Warner DS. Anes 1997
87:6:1576-1579.
