Severe COPD, a Shoulder Arthroscopy, and the Phrenic Nerve

A standard 20 mL interscalene block in this patient is close to a guaranteed hemidiaphragmatic paresis, and his respiratory reserve cannot absorb it.

The physiology: interscalene injection spreads to the C3–C5 roots and the phrenic nerve, producing ipsilateral hemidiaphragmatic paresis in nearly all patients at 20 mL. That reduces forced vital capacity by 25–30%. With a baseline FEV1 of 0.85 L and an FVC of 1.9 L, a 25–30% loss leaves him with an FVC around 1.3–1.4 L while supine in a beach chair with a full abdomen and a sedated airway - and he is already hypercapnic at 6.4 kPa with a compensated respiratory acidosis and home oxygen, so he has no reserve to handle atelectasis or hypoventilation. Add a laryngeal mask (leak, gastric insufflation, poor control of PEEP) and opioid-based analgesia, and this becomes a respiratory failure waiting to happen.

Options, from most to least phrenic-sparing:

• General anaesthesia with multimodal analgesia and a suprascapular nerve block plus an axillary (or subscapular) nerve block, which cover the shoulder and the posterior/superior capsule without touching the phrenic nerve. This is my preference.
• Superior trunk block with 5 mL of 0.5% ropivacaine: less phrenic spread than interscalene (roughly 20–40% versus near 100%) but not zero.
• Low-volume interscalene (5 mL) with a catheter for postoperative titration: useful for a rotator cuff repair, which is genuinely painful, but I would place it in a monitored setting with confirmed diaphragmatic function before relying on it.

I would not use a standard 20 mL interscalene here, and if any phrenic-adjacent block is used, it needs an endotracheal tube rather than an LMA, preoxygenation, and a plan for postoperative non-invasive ventilation.

Preoperative optimisation first: he has had an exacerbation 3 weeks ago and still has a productive cough. Ideally surgery waits 4–6 weeks after an exacerbation; if it cannot, I optimise with regular bronchodilators, continue his inhaled steroid, consider a short prednisolone course, chest physiotherapy, and smoking cessation advice even at this stage. Document that the risk was discussed.

Intraoperative:

• Airway: endotracheal tube, not an LMA - full control of ventilation, PEEP, and a secure seal in a beach-chair patient with a raised intra-abdominal pressure. Preoxygenate for 3 minutes (target end-tidal O2 >90%).
• Induction: propofol with remifentanil, avoiding high-dose opioid and avoiding nitrous oxide; rocuronium for intubation.
• Ventilation: low tidal volume 6–8 mL/kg predicted body weight, PEEP 5–8 cmH2O, respiratory rate adjusted for his baseline bicarbonate (permissive hypercapnia to a pH of ~7.30 is acceptable and expected), I:E ratio 1:2.5 with attention to air trapping, and FiO2 titrated to SpO2 88–92% rather than 100%.
• Monitoring: arterial line (his baseline blood gases give a reference point), capnography, and regular blood gas if the end-tidal CO2 drifts.
• Beach chair: watch for positional hypotension from venous pooling and reduced preload, and keep the head and neck neutral; re-check the shoulder and eye position, and remember cerebral perfusion pressure falls with the head up.
• Analgesia: the two blocks plus paracetamol and a low-dose opioid; avoid NSAIDs if renal function is marginal, and avoid gabapentinoids in a patient at risk of hypercapnia and sedation.

Extubation: reverse neuromuscular blockade fully (sugammadex or neostigmine with a train-of-four ratio >0.9), sit him up, ensure he is awake and following commands, and extubate on the table rather than deep. Have non-invasive ventilation available and a low threshold for CPAP in recovery. Postoperative monitoring on a high-dependency unit for at least the first night is appropriate given his spirometry and hypercapnia.

The differential is opioid-related hypoventilation, atelectasis with a COPD exacerbation, and - importantly - a phrenic-sparing block that may not have spared the phrenic nerve as much as expected, plus a surgical complication.

• Opioid toxicity: even with regional blocks, intraoperative and postoperative opioids plus reduced clearance can accumulate, and he has hypercapnia at baseline, so his CO2 response curve is blunted. Check the drug chart, the PCA history, and the pupil size. Give oxygen, support the airway, and use naloxone in small titrated aliquots (40–80 µg) only if he is not maintaining his airway - a full reversal in a patient in pain causes severe pain and hypertension, and the naloxone will wear off before the opioid does.
• Atelectasis or pneumonia: he has a productive cough, recent exacerbation, and a painful shoulder that limits coughing. Examine the chest, request a chest radiograph and blood gas, start chest physiotherapy, and consider non-invasive ventilation for hypercapnic acidosis rather than simply increasing oxygen, which can worsen CO2 retention.
• Phrenic paresis: suprascapular and axillary blocks are meant to spare the phrenic nerve, but confirm with ultrasound diaphragmatic excursion and a chest radiograph; if the diaphragm is paralysed, sit him up, provide CPAP, and plan for the block to wear off over 12–18 hours.
• The distended abdomen is a red flag: consider a laryngeal mask or airway issue with gastric insufflation if one was used, ileus, urinary retention, or a surgical complication (bleeding, pneumothorax from the arthroscopy, or a brachial plexus injury). Examine, check the surgical site and drain, and get a senior surgical review.

Immediate actions: sit up, high-flow oxygen titrated to his usual target, arterial blood gas, continuous capnography or at least respiratory rate monitoring, and call for senior help. Do not simply increase the oxygen and walk away - this is the exact scenario in which a COPD patient with a shoulder block dies overnight.