Case 1

A Patient with COPD, SpO2 on air of 93%, underwent transsphenoidal surgery for acromegaly after full preoperative work-up in the high-risk clinic. The surgery was uncomplicated. Post operatively the patient was very drowsy and slow to wake, with a GCS of 9.  Arterial blood gas showed pCO₂ 9.8 at the time and 10.7 two hours later.   The perioperative fluid balance was >2 litres positive.  The pCO₂ remained elevated overnight and the patient remained very drowsy with reduced GCS, but was not reintubated The following day it was noted that a  high dose of fentanyl  had been given intraoperatively. , After naloxone was administered the patient’s conscious level and ventilation improved, and they were discharged to the ward the following day and home 5 days after that.

Case 2

A patient underwent a partial knee replacement, having undergone similar procedures uneventfully at the same hospital previously. Pre-assessment revealed no significant comorbidities – in particular there was no history of chronic respiratory compromise.  Following extubation, the patient required high flow oxygen to maintain oxygen saturations. Auscultation suggested secretions. The patient managed to complete some deep breathing exercises and cough up a significant quantity of infected looking sputum. On questioning the patient gave a history of a dry cough for the past 3 weeks.  Nebuliser therapy and IV antibiotics were continued on the ward and the following day the patient was transferred to the local NHS trust for further monitoring and intervention. The patient’s condition deteriorated requiring intubation and ventilation.  Despite initial improvement the patient did not survive. 

Commentary

Even with optimal preoperative assessment and optimisation, patients with COPD are at increased risk of developing post-operative respiratory complications, including respiratory failure. When mechanical ventilation is required, settings should be adjusted to minimise air trapping with attention paid to fluid management as overload can exacerbate respiratory performance. Prior to extubation, there should be full reversal of neuromuscular block and hypoventilation due to residual volatile anaesthesia/ opioids should be avoided.  Post operative oxygen therapy should be based on arterial blood gas analyses in patients whose ventilatory drive may depend on relative hypoxia.¹

Sometimes patients do not reveal significant medical history pre-operatively, as appears to have been the situation in case 2. In the case of elective surgery, the patient may withhold information because they do not want the surgery to be delayed or cancelled. Even patients with no history of chronic respiratory disease can develop post operative complications such as those outlined here. Direct questioning about acute respiratory tract conditions is recommended.

1. O’Driscoll BR, Howard LS, Earis J, Mak, V on behalf of the British Thoracic Society Emergency Oxygen Guideline Group. BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax 2017 May. 72 ii1-ii90