Continuous Erector Spinae Plane Blocks for Rib Fractures

Rib fractures are one of the most common injuries in trauma patients. These fractures are associated with significant pain as well as decreased ability to inspire deeply or cough to clear secretions, which together lead to complications of the lungs and breathing which leads to risks of further injury and even death.

One recent study found that the ability to move air into and out of the lungs practically doubled with the administration of a single-injection Erector Spainae Plane Block (ESPB) while pain levels nearly halved. However, a single-injection nerve block lasts less than 24 hours while a perineural local anesthetic infusion (also termed a "continuous peripheral nerve block") may be administered for multiple days. This entails inserting a tiny tube through the skin and into the area around the nerves, after which more local anesthetic may be administered prolonging the numbing effects.

The possibility of extending the duration of a ESPB with local anesthetic administration via a perineural catheter has not be investigated. We therefore are conducting a randomized, triple-masked, placebo-controlled, parallel-arm study to investigate the addition of a continuous ESPB to a single-injection ESPB following traumatic rib fractures.

The primary outcome of this study will be the maximum inspired volume measured by incentive spirometry on the afternoon following the nerve block procedure. We hypothesize that the maximum inspired volume will be significantly increased in the afternoon following the procedure with the addition of a continuous ESPB to a single-injection ESPB.

Rib fractures are one of the most common injuries in trauma patients. These fractures are associated with significant pain as well as decreased ability to inspire deeply or cough to clear secretions, which together lead to complications of the lungs and breathing which leads to risks of further injury and even death.

The erector spinae plane block (ESPB) is a nerve block that covers multiple rib fractures with a single injection. This block entails injecting local anesthetic in the back superficial to the vertebral bodies. One study found that the ability to move air into and out of the lungs practically doubled with the administration of a single-injection ESPB while pain levels nearly halved.

A single-injection nerve block lasts less than 24 hours while a perineural local anesthetic infusion (also termed a "continuous peripheral nerve block") may be administered for multiple days. This entails inserting a tiny tube through the skin and into the area around the nerves, after which more local anesthetic may be administered prolonging the numbing effects. The possibility of extending the duration of a ESPB with local anesthetic administration via a perineural catheter has not be investigated.

We therefore are conducting a randomized, tripe-masked, placebo-controlled, parallel-arm study to investigate the addition of a continuous ESPB to a single-injection ESPB following traumatic rib fracture. Subjects will be individuals who present with rib fracture(s) and significant pain. Those who consent to participate in this study will have an ESP catheter inserted using ultrasound-guidance on the ipsilateral side at the level of the inferior-most fracture. For bilateral fractures, a second catheter will also be inserted on the remaining side. The single-injection ESPB will be administered to each catheter with 20 mL of ropivacaine 0.5% (with epinephrine).

Subjects with an accurately-inserted catheter based on visualization of local anesthetic spread will be allocated to one of two possible perineural treatments stratified by unilateral vs. bilateral fractures (1:1 ratio in blocks of 2):

1. active (ropivacaine 0.3%)
2. placebo (normal saline)

Computer-generated randomization lists will be created by the UCSD Investigational Drug Service which will keep the randomization lists and not release them to the investigators until the study is completed, at which time they will provide lists of subjects who received "Treatment A" and "Treatment B" so that the statistician can analyze the data. Only after the analysis is complete will "Treatment A" and "Treatment B" be defined for the investigators for manuscript preparation [producing a triple-masked study]. Of note, for bilateral catheters the treatments on both sides will always be identical: each subject will be randomized to a single treatment and not each side of bilateral cases.

Subjects will receive a basal infusion of study fluid (ropivacaine vs. placebo) 1 mL/h to keep the catheter lumen patent as soon as the infusion pump is initiated with a 500 mL reservoir. In addition, intermittent boluses (13 mL programmed automatic bolus every 2 hours) will begin 5 hours after pump initiation. For bilateral catheters, a 6-hour delay for one of the pumps will ensure that the pair of pumps alternate sides for the bolus doses each hour. This protocol will provide nearly 71-72 hours of study fluid administration.

Following local anesthetic reservoir exhaustion, subjects or their caretakers will remove the catheters with instructions provided by phone. This is standard at UC San Diego for all ambulatory continuous peripheral nerve blocks and will not be unique to study participation. The catheter is disposable in the trash and the infusion pump will be returned using a pre-addressed and postage-paid envelope provided to subjects prior to leaving the hospital.

Subjects will be contacted by telephone to collect study data on post procedure days 1, 2, 7, and at months 0.5, 1, 1.5, 2, 3, 6, and 12.

The ultimate objective of the proposed line of research is to determine if the addition of a continuous ESPB to a single-injection ESPB prolongs analgesia following traumatic rib fractures; and, if this analgesic intervention improves pulmonary mechanics measured with incentive spirometry.

Specific Aim 1: To determine if the addition of a continuous ESPB to a single-injection ESPB improves maximum inspiratory volume following traumatic rib fracture(s).

Hypothesis 1a: The maximum inspired volume will be significantly increased in the afternoon following the procedure [primary endpoint] as well as at other time points following the procedure [secondary end points] with the addition of a continuous ESPB to a single-injection ESPB [measured with an incentive spirometer].

Hypothesis 1b: The maximum inspired volume as a percentage of the baseline will be significantly increased in the afternoon following the procedure [secondary endpoint of greatest interest], as well as at other time points following the procedure [secondary end points] with the addition of a continuous ESPB to a single-injection ESPB [measured with an incentive spirometer].

Specific Aim 2: To determine if the addition of a continuous ESPB to a single-injection ESPB decreases the pain associated with rib fracture(s).

Hypothesis 2a: The severity of rib fracture pain at rest will be significantly decreased within the 12 months following the procedure with the addition of a continuous ESPB to a single-injection ESPB [measured using the Numeric Rating Scale for pain].

Hypothesis 2b: The severity of rib fracture pain when using the spirometer or coughing will be significantly decreased within the 12 months following the procedure with the addition of a continuous ESPB to a single-injection ESPB [measured using the Numeric Rating Scale for pain].

Hypothesis 2c: The incidence of chronic rib fracture pain will be significantly decreased 6 and 12 months following a rib fracture with the addition of a continuous ESPB to a single-injection ESPB [measured using the Numeric Rating Scale for pain].

Hypothesis 2d: The severity of chronic rib fracture pain will be significantly decreased 6 and 12 months following a rib fracture with the addition of a continuous ESPB to a single-injection ESPB [measured using the Numeric Rating Scale for pain].