A 52-year-old woman was scheduled for modified radical mastectomy on account of advanced carcinoma of the right breast. The patient was a known hypertensive and diabetic, diagnosed 3 years prior to presentation and also a known asthmatic, diagnosed at childhood. She was being managed with lisinopril, amlodipine, and Mixtard insulin injection. However, she was not compliant on her medications. Three days before the scheduled surgery, her blood pressure (BP) was 170/110 mmHg, and fasting blood sugar was 10.8 mmol/L. Additionally, she suffered an asthmatic attack 2 days prior to surgery. Her regular doses of antihypertensive drugs and insulin(42 IU/day) were increased, while salbutamol inhaler at 2 puffs as required, along with aminophylline and prednisolone tablets were used to manage the mild asthmatic attack. On the evening prior to surgery her vital signs were as follows: pulse rate (PR) 88/minute, BP 130/70 mmHg, respiratory rate (RR) 20/minute and temperature 36.8°C. Her chest was clinically clear and other examination findings were normal. Her packed cell volume (PCV) was 36%. Electrocardiogram (ECG) and chest x-ray findings were suggestive of left ventricular hypertrophy. Other investigation results, including electrolyte, urea, and creatinine were within normal limits. Based on the comorbid conditions, she was assigned class to III of the American Society of Anesthesiologists (ASA) classification scheme. She was counselled for thoracic epidural anaesthesia, as general anaesthesia was considered a more risky alternative, and consent for the procedure was obtained. On the morning of surgery her fasting blood sugar was 8.9 mmol/L and 500 mL of 5% dextrose water infusion, into which 5 mmol of potassium and 5 IU of soluble insulin were added, was set up to run at 100 mL/hour. Additionally, the morning doses of her regular antihypertensive medications were given. In theatre, a multiparameter monitor was attached to the patient, measuring peripheral capillary oxygen saturation and noninvasive BP. Baseline values were as follows: PR 84/ minute, BP 110/70 mmHg, and SpO 2 96%. In the sitting position, a midline thoracic epidural was performed at the T4/T5 interspinous space using a size 18G Tuohy epidural needle and loss of resistance to air technique. The skin epidural depth was 5 cm, and 4 cm of the epidural catheter was left in situ in the epidural space in the cephalad direction, and the catheter adhered to the back with adhesive tape. After a test dose of 3 mL of 1% lidocaine with adrenaline, a loading dose of 7 mL of 2% lidocaine with adrenaline 1:200,000 was given in 4 mL and 3 mL aliquots at 5-minute intervals. The epidural catheter was connected to a syringe pump for continuous infusion of 2% lidocaine-adrenaline at 4 mL/hour. Five minutes later, a sensory block height of T1 to T10 was achieved bilaterally, and the surgery commenced. The breast tissues and tumour were excised en bloc, including fibrofatty tissues of the medial aspect of the right axilla. Oxygen was given via face mask at 4 L/minute througho...