Humanity is facing an unprecedented health crisis because of COVID-19 pandemic . Concern has been raised because of the fact that up to 80% of COVID-19 positive patients are asymptomatic  yet can present ground-glass opacities in chest CT scan , interstitial (i.e. ‘walking’) pneumonia  and significant hypoxemia , reflecting considerable (and mostly undiagnosed) underlying pulmonary compromise. Unfortunately, up to 30% of infected patients will be reported as free of the virus with recommended perioperative tests at present . According to a recent multinational observational cohort study involving 1128 patients who had surgery in 24 countries, postoperative pulmonary complications occur in half of the patients with perioperative COVID-19 infection and are also associated with high mortality. Of note and worrisome, these pulmonary complications and mortality rates are greater than those reported for even the highest risk patients before the pandemic .
To date, the impact of COVID-19 in healthcare providers (HCP) and surgeries worldwide is still evolving, with many centers resuming elective procedures with variable rates of community spread worldwide. HCP are susceptible to viral contamination after exposure to aerosol-generating medical procedures (AGMPs), and recommendations to avoid airway management procedures commonly performed in the perioperative period have been issued [8▪]. Nevertheless, given that COVID-19 can also severely impair lung function, regional anesthesia techniques avoiding phrenic nerve paralysis may become increasingly relevant in the anesthetic management of patients undergoing shoulder and clavicle surgery. This review will focus on updating the most recent information on diaphragm-sparing regional anesthesia techniques that can be useful for these surgical procedures in the context of the COVID-19 pandemic.
ANALGESIA FOR CLAVICLE FRACTURES
Clavicle fractures are associated with severe pain  and surgical management is usually indicated . Sensitive innervation of the clavicle and surrounding skin is controversial. Contributions from the supraclavicular nerves not only from the superficial cervical plexus but also from the brachial plexus (BP) via subclavian, suprascapular, long thoracic nerves, and lateral pectoral nerve have been described [11,12]. Therefore, interscalene block (ISB) complemented with a superficial cervical plexus block (SCPB) has been classically suggested .
Clavipectoral fascial plane (CPFP) block described by Valdés-Vilches et al. consists of an ultrasound-guided infiltration using 10–15 ml of local anesthetic deep to the fascia that covers the clavicle and separates it from the minor pectoral muscle, blocking bone innervation to the clavicle . Complementary SCPB is suggested to anesthetize the skin, nevertheless, this block can potentially involve the phrenic nerve if the injection is not performed accurately in the proper subcutaneous plane and using low volumes . Another option to avoid any risk of diaphragm involvement with SCPB will be to directly infiltrate the clavicle surrounding skin. Currently, CPFP has been documented both as an analgesic block and as an individual anesthetic technique in isolated case reports [15,16]; however, diaphragm-sparing potential and anesthetic/analgesic effectiveness of this new block for clavicle surgery still need to be evaluated in future randomized studies.
IN SEARCH OF THE IDEAL BLOCK FOR SHOULDER SURGERY
Shoulder surgery is related to severe postsurgical pain with opioid requirements comparable to that of a thoracotomy . Regional anesthesia is associated with lower pain scores and greater patient satisfaction . The 2019 procedure-specific postoperative pain management (PROSPECT) approach guidelines for rotator cuff repair surgery by Toma et al. recommend that the analgesic regimen for rotator cuff repair should include an arthroscopic approach and the use of a regional anesthesia technique as a component of perioperative multimodal analgesia that only includes opioids as rescue analgesia. Continuous regional anesthesia techniques over a single shot approach and use of dexamethasone are also discussed as highlighted recommendations to contribute to prolonging analgesic benefits and preventing rebound pain.
The gold standard regional anesthesia technique for shoulder surgery is ISB . However, it is related to the highest incidence of transient (3.5/1000) and permanent (2.5/1000) nerve damage . Also, it is greatly associated with phrenic nerve block producing undesirable diaphragm paralysis . Although this is usually not clinically significant in healthy individuals, it can lead to respiratory failure in patients with compromised pulmonary function. Paradoxically, effective regional anesthesia analgesia with reduced opioid consumption is highly desirable in these patients, thus posing a dilemma for clinicians.
Given the aforementioned risks, there is an increased interest in finding a shoulder block that offers a superior safety profile, capable of providing reliable and reproducible shoulder analgesia/anesthesia comparable with ISB, but that also grants the privilege of lung function preservation by its diaphragm-sparing effect (Table 1).
Superior trunk block
Superior trunk block (STB) is performed where the C5 and C6 nerve roots are coming together to conform the superior trunk, and very importantly, before the suprascapular nerve leaves the trunk .
A careful approach to ultrasound-guided STB may prevent the possibility of potential injuries to the dorsal scapular and long thoracic nerves by avoiding passing the needle close to them [24,25]. Also, as it is performed where the trunk is already formed, it reduces possible failures in patients with anatomical C5 variability, which can be found in up to 30–35% of the population . Anatomically, STB is performed further away from the phrenic nerve, which has the theoretical advantage of minimizing the risk of nerve injury as there is more epineurium at this level .
Two studies report that STB is an effective regional anesthesia alternative to the ISB in preserving lung function while providing comparable surgical anesthesia and analgesia. Kim et al.[27▪] performed STB and ISB for surgical anesthesia and reported 71.4% full diaphragmatic paralysis for the ISB versus only 4.8% for STB with no report of partial paralysis with STB. In the study by Kang et al. partial diaphragm compromise was reported in 97.5% of ISB and 76.3% of STB, with full paresis in 72.5% of cases for the ISB versus only 5.3% for STB.
Anterior suprascapular nerve block
Described by Siegenthaler et al., anterior suprascapular nerve block (ASNB) consists on blocking the suprascapular nerve as it moves away from the superior trunk, posterior to the lower belly of the omohyoid muscle (subomohyoid approach) and before traveling to reach the supraspinous fossa of the scapula. Wiegel et al. found comparable analgesia to ISB with less motor function compromise. Abdallah et al.[31▪] compared subomohyoid ASNB versus ISB for shoulder arthroscopic surgery finding noninferiority of ASNB in terms of achieved postoperative pain control in the first 24 h. They also quantified the frequency of sensory-motor block in C5-C6 dermatome finding a consistent block of the superior trunk. Interestingly, a recent cadaver study showed that after only 5 ml of dye injection, 20% of cases had phrenic nerve staining . They also found that 90% of the specimens had dye staining the superior trunk, 80% of the middle trunk, and 30% of the lower trunk, which could also explain the comparable analgesia to ISB.
Regarding phrenic nerve involvement, Ferré et al.[33▪] evaluated hemidiaphragmatic paralysis following axillary nerve block with ASNB versus posterior suprascapular nerve block (PSNB) for shoulder surgery, finding it in 41% of the patients with the ASNB (33% partial and 7% complete) and 2% with the PSNB (0% partial and 2% complete). The authors also describe higher opioid consumption in the PSNB group, supporting previous studies reporting the analgesic inferiority of this approach to ISB in the immediate period after arthroscopic shoulder surgery [34,35].
This block was described by Karmakar et al. as an alternative approach to infraclavicular block also suitable for perineural catheter placement . Aliste et al.[38▪] compared the costoclavicular bloc (CCB) to ISB for arthroscopic shoulder surgery using 20 ml of local anesthetic, finding equivalent analgesia with complete diaphragm paralysis in 100% of the ISB group versus 0% in the CCB group. Sivashanmugam et al.[39▪] reported an incidence of 5% of complete diaphragm paralysis with CCB using the same volume of 20 ml, despite that his study was performed for upper arm surgery and not for shoulder or clavicle procedures. Similarly, Oh et al. report an incidence of 2.5% of complete diaphragm paralysis with CCB.
Infraclavicular block with suprascapular block
Aliste et al. compared ICB and PSNB with the ISB, reporting a lower pain score at initial 30 min with ISB, and comparable analgesia thereafter. Nevertheless, ISB was associated with lower opioid consumption. Diaphragmatic paralysis was found in 90% of ISB patients versus 0% in the ICB and PSNB. Of note, a previous study reported an incidence of 3% complete hemidiaphragmatic paralysis when using ICB .
Taha et al. compared ISB with ICB and ASNB, finding no difference in analgesia duration, opioid consumption, or patient satisfaction. However, diaphragmatic paralysis was found in 88.9% of ISB versus 5.6% in ASNB. The usefulness of adding ICB to ASNB is questionable as it has been shown that ASNB alone produces comparable analgesia to ISB.
Erector spinae plane block
Case reports have described its use in shoulder surgeries with the potential advantage of diaphragm-sparing [44,45,46▪]. Tsui et al. reports using ESP as continuous regional analgesia for shoulder surgery at the T2 level moving a stimulating catheter in a cephalic direction obtaining a deltoid response. Nevertheless, the impact of ESP block in hemidiaphragmatic function has not been established. The analgesic role and safety profile of ESP block in shoulder surgery is currently under active research.
REGIONAL ANESTHESIA CONSIDERATIONS FOR SHOULDER AND CLAVICLE SURGERY DURING THE COVID-19 PANDEMIC
Anesthetic management strategies during the COVID-19 pandemic are a matter of ongoing discussion. Given the fact that all patients (even those asymptomatic) during the mitigation phase should be considered infected unless proven otherwise [8▪], expert opinion from the American Society of Regional Anesthesia and Pain Medicine (ASRA) and European Society of Regional Anesthesia and Pain Therapy (ESRA) recommends the use of regional anesthesia over general anesthesia whenever feasible, to minimize the need of exposure of HCP to AGMPs and reduce the potential risk of perioperative pulmonary complications [48▪▪].
Furthermore, different groups around the world have published their practical considerations for performing regional anesthesia during the COVID-19 pandemic [49–51] emitting expert opinion based on available context-specific scientific evidence. Innovative recommendations have been wisely suggested and they might contribute to developing effective and adaptable anesthetic plans under high standards of efficiency, while strictly preserving HCP and patient safety. Some of these recommendations include individualizing each clinical scenario; planning of human resources giving high priority to expertise; adapting the clinical environment to enhance safety; preparing necessary and suitable equipment and drugs in advance; selecting and assuring appropriate personal protective equipment (PPE) for HCP; providing adequate oxygen therapy with pertinent sedation without increasing risk of contamination; planning for safely performing regional anesthesia procedures; and, monitoring during the conduct of anesthesia and postanesthetic care.
Individualizing patient care after risk/benefit consideration of regional anesthesia techniques is paramount. For shoulder and clavicle surgery, regional anesthesia techniques like ISB can be considered for surgical anesthesia in COVID-19 negative patients without respiratory compromise, but in the context of patients with clinical signs of respiratory involvement (i.e. dry cough, shortness of breath, decreased SpO2) and scheduled for an urgent procedure, a diaphragmatic-sparing technique needs to be ensured if at all to be used. On the other hand, even if regional anesthesia is performed only as an adjunct to general anesthesia for analgesic purposes, a block with phrenic nerve-sparing qualities is desirable for most patients as it has the potential of reducing the amount of opioid requirements to control postoperative pain. For this, ASNB [31▪], combined ICB with suprascapular nerve , CCB [38▪] and STB [27▪,28] may be considered valid alternatives for analgesia, whereas surgical anesthesia has only been reported with STB [27▪]. Regarding these blocks reporting similar analgesia to ISB, none of them ensure the absence of phrenic nerve compromise. In the case of axillary nerve block with PSNB ('shoulder block’), Ferré et al.[33▪] reported a 2% incidence of complete diaphragmatic paralysis with an analgesic profile inferior to ISB. This unexpected finding is surprising as the mechanisms by which such distal block could potentially cause diaphragmatic paralysis merits further research to rule out a potential reproducible pathway of local anesthetic dissemination versus a misplaced injection of local anesthetic in the context of a block considered technically challenging. In the same way, future research on the role of ESP and clavipectoral blocks for shoulder and clavicle surgery and their impact on phrenic nerve function is warranted.
Careful reasoning and interdisciplinary collaboration with the surgical team is essential to balance the benefits and potential risks of aiming for an anesthetic block, as its failure will need an emergency conversion to general anesthesia. This undesirable scenario will defeat the initial purpose of using regional anesthesia to reduce the possibility of exposure during AGMPs, and perhaps, may even increase the risk of HCP contamination as airway management will be approached under suboptimal, uncomfortable, and stressful conditions.
COVID-19 pandemic has become an opportunity for regional anesthesia to stand up as an essential tool for anesthesiologists. Recent developments in diaphragm-sparing nerve blocks for shoulder and clavicle surgery acquire increased relevance in patients with respiratory compromise as they may help minimize deleterious respiratory effects of phrenic nerve paralysis. Opioid-sparing effective perioperative analgesia added to lung function preservation capability is also of utmost importance. Unfortunately, an optimal approach remains elusive.
In the context of suspected/confirmed COVID-19 patients, meticulous individualized breakdown of risks and benefits should be debated. Except for STB, all regional anesthesia techniques discussed have been studied only for analgesia and not for surgical anesthesia, reporting various degrees of phrenic nerve involvement, and their use is recommended as part of a multimodal analgesic approach that includes general anesthesia. Further research on the real clinical impact of complete/partial phrenic nerve paralysis after the regional anesthesia techniques reviewed is warranted.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
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