A comparison of interscalene and supraclavicular approaches with brachial plexus block during shoulder surgery suggests that using larger volumes of local anesthetic does not provide a longer duration of effect.
According to the study’s authors, when compared with the interscalene approach, the supraclavicular approach provided similar post operative pain control along with a lower incidence of phrenic nerve dysfunction.
“The rather unconventional approach for shoulder surgeries of supraclavicular block with local anesthetic volumes lower than 20 cc was proven adequate to provide postoperative anesthesia and analgesia, compared to the more conventional interscalene approach using higher volumes of local anesthetic,” said Hesham M. Ezz, MD, an anesthesia research fellow at Yale University School of Medicine, in New Haven, Conn.
“Even after stratifying our patients into higher or lower volumes of local anesthetic, the supraclavicular approach was proven to be safer in terms of phrenic nerve dysfunction compared to the interscalene approach,” Dr. Ezz added.
While both supraclavicular and interscalene approaches to the peripheral nerve block have been proven to provide safe and effective perioperative anesthesia and analgesia for upper extremity surgery, there are possible complications, including phrenic nerve involvement leading to hemidiaphragmatic dysfunction (Anesth Analg 2005;101:1663-1676; Can J Anaesth 2007;54:662-674). As Dr. Ezz reported at the American Society of Regional Anesthesia and Pain Medicine 2016 annual meeting (abstract 2861), hemidiaphragmatic dysfunction can be well tolerated in healthy patients, but in older or obese patients, or those with chronic obstructive pulmonary disease, it may result in dyspnea, anxiety and decreased oxygen saturation (Anaesth Intensive Care 1979;7:285-286).
Incentive Spirometry Device Assesses Phrenic Nerve Dysfunction
In this observational prospective study, Dr. Ezz and his colleagues attempted to answer the following clinical objectives in 110 patients undergoing shoulder surgery:
Would larger volumes of local anesthetic provide longer block duration?
Is the interscalene or supraclavicular approach safer?
What are the implications of different volumes of local anesthetic on patient safety?
The researchers used an incentive spirometry device to evaluate the influence of phrenic nerve dysfunction on inspiratory flow of patients before and 15 minutes after brachial plexus block for shoulder surgery. The use of incentive spirometry can assess the ability of a patient to take a deep breath, and is able to quantify the flow rate per second by the numbers of balls being moved (one ball, 600 cc per second; two balls, 900 cc per second; and three balls, 1,200 cc per second).
After block placement, phrenic nerve dysfunction was defined as an at least 30% reduction in the number of balls elevated, labored breathing and/or pain experienced in the midaxillary lower chest on the block side during deep breaths. Phrenic nerve dysfunction was confirmed clinically by reduction of air entry on the block side.
The block team assessed pain after performing the block, after patient recovery in the PACU and before discharging the patient home after surgery.
As Dr. Ezz reported, both approaches provided similar and adequate quality of anesthesia and postoperative analgesia, but phrenic nerve dysfunction was more prevalent with the interscalene versus supraclavicular approach (68% vs. 27%, respectively).
Using more than 20 cc of local anesthetic volume also resulted in a higher incidence of phrenic nerve dysfunction without prolonging block duration. In the supraclavicular group, 10 of 20 patients who received more than 20 cc of local anesthetic (50%) experienced phrenic nerve dysfunction, whereas only seven of 43 patients (16.3%) who received no more than 20 cc experienced the same. In the interscalene group, 25 of 33 patients (76%) receiving more than 20 cc of local anesthetic experienced phrenic nerve dysfunction, compared with seven of 14 patients (50%) receiving less than 20 cc.
In addition, there was no significant correlation between volume of local anesthetic used and duration of postoperative blockade, said Dr. Ezz, who also noted that phrenic nerve dysfunction is a temporary side effect.
“Patients who did receive more than 20 cc of local anesthetics during interscalene block usually return to their baseline level after five to seven hours postoperatively,” he said.
Moderator James C. Eisenach, MD, president and CEO of the Foundation for Anesthesia Education and Research, in Schaumburg, Ill., inquired as to whether any of the study participants experienced chronic phrenic nerve dysfunction after surgery.
“We didn’t do long-term follow-up,” Dr. Ezz said, “but all of our patients were followed up, either before discharge from the hospital or with a second-day call by a nurse. We also monitored patients by phone to ensure function was regained, so I would say that none of the patients had more than several hours’ weakness or numbness.”
“As you probably know,” Dr. Eisenach said, “Dr. Quinn Hogan has written a couple of somewhat controversial editorials about this topic, and considers the phrenic nerve to be a very fragile nerve, susceptible to the effects of local anesthetics. According to [Dr. Hogan’s] research, inflammation after an interscalene approach can lead to chronic palsy of the phrenic nerve, and there are now increasing reports of chronic dysfunction for months after surgery, but you have to look for it to see it.”