The simple addition of ultrasound guidance to traditional thoracic paravertebral blockade does not necessarily add safety and technical ease. According to a recent comparative analysis, a modified ultrasound-guided proximal intercostal block in women undergoing breast surgery offers sonoanatomic and technical advantages over the traditional ultrasound-guided paravertebral block, without compromising pain-related outcomes.
“Our findings demonstrate that the proximal intercostal block approach allows a clearer simultaneous visualization of block needle, parietal pleura, bony landmarks and injectate spread,” said Kristin Schreiber, MD, PhD, an anesthesiologist and clinical researcher at Brigham and Women’s Hospital, in Boston. “It also looks as though we were able to achieve comparable analgesia with this technique.”
As Dr. Schreiber explained, an ideal ultrasound technique would be easy to perform, avoiding neuraxial injection and lung injury while permitting real-time visualization of the needle tip and injectate spread. Although thoracic paravertebral blockade is an accepted technique to provide analgesia both during and after breast surgery, its use with ultrasound guidance is not well studied. Many anesthesiologists have been trained in the use of landmark-based paravertebral placement, Dr. Schreiber noted, but there has been a recent institutional push for the use of ultrasound with this technique. Nevertheless, there are safety concerns.
“We had noticed [with the paravertebral approach] that with the traditional parasagittal view over the transverse process, it can be difficult to visualize the pleura and your needle because of bony shadowing,” Dr. Schreiber said. “We noticed that with a slightly more lateral parasagittal approach over the proximal intercostal space, the ribs cast a narrower shadow and the pleura and needle were easier to see.”
Thus, Dr. Schreiber and her colleagues proposed a modified ultrasound-guided proximal intercostal block approach at the level of the proximal ribs as an alternative to the traditional paravertebral approach at the level of the transverse processes.
Rating Scale for Ultrasound Imaging
To determine whether targets are better visualized with the proximal intercostal block approach or traditional paravertebral blockade, the researchers devised an ultrasound image rating scale based on visualization of the parietal pleura, bony landmarks, relevant ligaments, the block needle and injectate spread. Ultrasound images were obtained before and after needle placement, including video recording of the injection of the local anesthetic.
The study’s primary outcome was overall ultrasound imaging score (0-18), as determined by an independent reviewer. Secondary outcomes included block performance times, postoperative pain scores (measured at one hour and 24 hours) and opioid consumption during the first 24 hours after surgery. The Student t test or Mann-Whitney test was used to compare groups, as appropriate. Women undergoing total mastectomy were randomly assigned to receive a paravertebral block (n=10) or proximal intercostal block (n=8) preoperatively at two to four block sites with a total of 2.5 mg/kg ropivacaine.
As Dr. Schreiber reported at the International Anesthesia Research Society 2017 annual meeting (abstract 1461), overall image rating scores were superior for the proximal intercostal block compared with paravertebral blockade.
“There was definitely more variability in image rating scores with the traditional paravertebral block, and we had a few patients that were very difficult to see with this technique,” Dr. Schreiber said. “Although there was also variability with the proximal intercostal approach, scores were clustered towards the top of the visual ratings.”
According to the researchers, when broken down by different elements, better visualization of bony landmarks and pleura contributed to the higher overall score for the proximal intercostal approach. Although the study was not statistically powered to see a difference in analgesic outcomes, postoperative pain scores and opioid consumption were low for both block techniques, Dr. Schreiber reported, and noted that technical performance times were similar for both blocks. Somewhat unexpectedly, however, the investigators observed that needle depth at the skin was actually greater for the proximal intercostal block.
“Perhaps we’re coming at a shallower angle with the needle because we have more space in between to work with,” Dr. Schreiber speculated.
Moderator of the session, Richa Wardhan, MD, assistant professor of anesthesia at the University of Florida College of Medicine, in Gainesville, observed that she was not surprised by the better visibility recorded with the proximal intercostal block.
“In the sagittal plane and in bigger patients especially, the view of the paravertebral space is very poor,” Dr. Wardhan said. “Rather than putting your probe in the sagittal plane, however, a transverse visualization of this space may provide a better view, and you would probably have a longer path there.”
“The resistance of some practitioners to the lateral to medial transverse approach is the potential for placement of the catheter in the epidural space,” Dr. Schreiber said.