Total hip replacement is often performed under spinal anesthesia, which is the standard at
Thomas Jefferson University Hospital (TJUH) and Rothman Orthopedic Specialty Hospital (ROSH)
for patients without contraindications. Spinal anesthesia involves injecting a numbing
medicine (local anesthetic) into the cerebrospinal fluid that bathes the spinal cord through
a space between two bones in the back. This causes temporary numbness of the legs and hips
and allows surgery to take place without patients feeling pain during surgery. Different
local anesthetics can be used for spinal anesthesia and each works for a different duration
of time. Another factor that affects how spinal anesthesia medications work is the baricity
of the medication, which refers to how dense it is compared to cerebrospinal fluid (CSF).
Medications that are less dense than CSF are hypobaric, those with same density are isobaric,
and those with greater density are hyperbaric. For clinical purposes, this really only comes
into play when positioning the patient immediately after spinal placement as patient position
has different effects on the dermatomal level attained depending on baricity of the local
anesthetic. Bupivacaine is a long-acting local anesthetic that has been used for several
decades for total hip replacement. It is available in both hyperbaric form (with dextrose
added) and isobaric form (with no dextrose added). Mepivacaine is another local anesthetic
that has a shorter duration of action and is also used for spinal anesthesia in total hip
replacement at many centers. All three drugs are used routinely at different centers in the
United States. Despite the differences in duration that have been described from
pharmacokinetic studies, a randomized, controlled study comparing the three drugs in terms of
important outcomes, such as the ability to walk after surgery, has not been published yet.
Therefore, the investigators want to compare the three local anesthetics in a randomized,
controlled fashion to see if more patients are able to walk sooner after receiving
mepivacaine spinal anesthesia than either form of bupivacaine spinal anesthesia.
Patients who are eligible will be called the night prior to surgery and the study will be
explained over the phone. Patients who express interest will be recruited on the day of their
scheduled surgery in the short-procedure unit. Patients will be given consent forms and time
to read them and ask questions.
Preoperative Management All patients without contraindications or allergies will receive oral
gabapentin and acetaminophen in the short procedure unit prior to surgery per routine
practice.
Intraoperative Management The targeted spinal dermatome level to achieve will be T10
(umbilicus). For isobaric drugs, patients will sit after spinal placement for 3-5 minutes to
achieve this level. For hyperbaric bupivacaine, patients will be immediately placed supine
and in Trendelenberg position for 3-5 minutes to achieve adequate level and confirmed with
sensory pinprick testing, which will be performed every 2 minutes beginning at spinal
placement time. After spinal is placed, sedation will be titrated at the discretion of the
anesthesia team to achieve the American Society of Anesthesiology's definition of moderate
sedation (purposeful response to verbal or tactile stimulation, spontaneous ventilation, and
no airway intervention needed) using propofol. All patients will receive tranexamic acid
unless contraindicated (10 mg/kg bolus), as well as multimodal analgesia with a non-steroidal
anti-inflammatory drug (NSAID) and dexamethasone 4 mg IV per routine practice.
Postoperative Management
Sensory and motor assessments will take place every 30 minutes from PACU arrival time until
motor strength is 5/5 in both lower extremities in hip flexion, knee extension, and toe
dorsiflexion or the patient's motor function returns to baseline. The time of return of motor
function will be documented. Physical therapists will visit the patient between 3 and 3.5
hours after spinal placement to assess for ability to ambulate and perform Tinnetti test,
which assesses ambulation and gait and gives a score of 0 through 28 (see attached). Urinary
retention will be assessed through asking the following on postoperative day 1:
1. At what time did the participant first urinate?
2. Did participant require a Foley catheter or straight catheter to drain urine from his or
her bladder?
These questions will be asked along with the following about TNS (transient neurological
symptoms):
1. Does the participant have any pain in his or her lower back that goes into his or her
buttocks and/or down his or her thigh that was not there before surgery?
2. If yes, how would the participant rate that specific pain from 0 (no pain) to 10 (worst
pain imaginable).
3. How would the participant rate his/her overall pain (0 to 10 scale)?
4. How satisfied is the participant with his/her anesthesia experience (0 to 10 scale where
0 is very dissatisfied and 10 is very satisfied)?
TNS will be defined as the new onset (within 24 hours of surgery) of back pain that radiates
into the buttocks, thighs, hips, or distally. Localized back pain will not be included.
Urinary retention will be defined by inability to urinate within 8 hours, a report of
distended or painful bladder occurring on postoperative days 0 or 1, either by patient report
or on assessment by nursing, or the use of a Foley catheter or straight catheter.
Post-discharge phone calls
The following will be asked to patients via phone calls after discharge at 24 and 48 hours
after surgery if not still in the hospital (will be asked in-person otherwise):
1. Does the participant have any back pain that was not present before surgery that goes
into his/her buttocks, thighs, hips, or lower leg?
2. If yes, how would the participant rate that specific pain from 0 (no pain) to 10 (worst
pain imaginable).
3. How would the participant rate his/her overall pain (0 to 10 scale)?
4. How satisfied is the participant with his/her anesthesia experience (0 to 10 scale where
0 is very dissatisfied and 10 is very satisfied)?
Post-discharge data collection Readmissions within 90 days will be recorded for all patients
including the reason for readmission.
General Operating Procedures Patients who agree to participate will then be randomized by a
computer-generated sequence to one of the three study groups. The anesthesiologist and
certified registered nurse anesthetist or resident performing the spinal will be aware of
group allocation and will perform spinal anesthesia according to standard operating
procedures with the assigned local anesthetic. Intraoperative sedation will be with propofol
or dexmedetomidine, at the discretion of the anesthesia team. Patients will remain blinded
and surgeons and those performing postoperative assessments will remain blinded as well. As
all study drugs are standard spinal anesthesia drugs and readily available, the anesthesia
team caring for the patient will be informed of group allocation and the appropriate drug
will be selected. These doses of hyperbaric and isobaric bupivacaine are considered "low
dose" and are lower than those routinely used at TJUH and ROSH. However, existing evidence
shows that low-dose bupivacaine for spinal anesthesia provides adequate anesthesia time for a
total joint replacement. Dosing will be as follows: isobaric bupivacaine 12.5 mg (2.5 cc of
0.5%) for < 74" height and 15 mg (3 cc) for > or = 74" height; hyperbaric bupivacaine 10.25
mg (1.5 cc 0.75%) for < 74" height and 13.125 mg (1.75 cc) for > or = 74" height; and
isobaric mepivacaine 52.5 mg (3.5 cc of 1.5%) for < 74" height and 60 mg (4 cc) for > or =
74" height. Patients with BMI of 35 or greater will also be given the higher dose of each of
the 3 medications listed above.
Intraoperative variables that will be measured include: hypotension (defined as a decrease in
baseline blood pressure of 20% or greater), surgeon rating of intraoperative muscle tension
(0, 1, 2, or 3 where 0 is the most relaxed and 3 is the tightest), and conversion to general
anesthesia.
Postoperative variables that will be measured include: ambulation at 3-3.5 hours (primary
endpoint), time to ambulation, attempts needed to ambulate, episodes of orthostatic
hypotension while trying to ambulate, urinary retention, opioid consumption, pain, incidence
of transient neurological symptoms up to 48 hours postoperatively, discharge readiness, and
length of stay.
Post-discharge phone calls
The following will be asked to patients via phone calls after discharge on postoperative days
1 and 2 after surgery if not still in the hospital (will be asked in-person otherwise):
1. Does the participant have any pain in his/her lower back that goes into his/her buttocks
and/or down his/her thigh that was not there before surgery?
2. If yes, how would the participant rate that specific pain from 0 (no pain) to 10 (worst
pain imaginable).
3. How would the participant rate his/her overall pain (0 to 10 scale)?
4. How satisfied is the participant with his/her anesthesia experience (0 to 10 scale where
0 is very dissatisfied and 10 is very satisfied)?
