POST OPERATIVE Chapters 7 and 8 – Learning from Experience

Dr. Vasanthi Vidyasagaran*

Department of Anaesthesiology, Kauvery Hospital, Chennai, Tamilnadu, India

POST-OPERATIVE – Chapter 7

Delayed recovery – Metformin and Lasix for weight reduction

A 45-year-old woman weighing 70 kg was to undergo abdominal hysterectomy for uterine fibroid. Her preoperative examination was normal, all routine investigations, including blood sugar were normal. As per the patient’s request, the surgery was planned under general anaesthesia.

She was premedicated with injection Tramadol 50 mg and Glycopyrrolate 0.2 mg IM half an hr before the procedure. Following preoxygenation, she was induced with Propofol 150 mg and Atracurium 40 mg was used as muscle relaxant, and intubated with 7.5 cuffed endo tracheal tube. For maintenance of anaesthesia a 40:60 mixture of Oxygen and Nitrous Oxide, along with Isoflurane 0.5% to 1% was used. Injection Fentanyl 100 mcg and 1 gm of intravenous Paracetamol were also given during the procedure.

The surgery was completed uneventfully in one and a half hours, with a total relaxant dose of 60mgs. At the end of the procedure, she did not recover as expected. The procedure and anaesthesia was routine and there was no untoward event. Common causes of delayed recovery were ruled out. Temperature was normal, pulse rate was 110/min, blood pressure was 100/60, pupils were normal, and reacting to light. Lungs were clear, oxygen saturation was 100%, and capnography read 30 mm Hg. There were shallow attempts at breathing but she was not waking up. Total intravenous fluid given was one litre of Ringer Lactate. Urine output at the end of the procedure was 100 ml.

All parameters being near normal, the cause of this delay in regaining consciousness was intriguing. Though patient was not a known diabetic, we thought a blood glucose level might clinch the diagnosis. Capillary blood glucose revealed a sugar levels of 38 gm/dl. She was given a bolus dose of 50 ml 25% Dextrose, after which her CBG came up to 90 gm/dl. Recovery was smooth once the hypoglycemia was corrected. Patient was reversed and extubated.

On probing post operatively, she came forth with a history of medication, comprising Metformin and Lasix as part of weight loss regime! And she had been taking it for over 5 years! This was not revealed or recorded in the preoperative check.

Discussion

This case highlights that thorough history taking is very important. Patients may not be willing to reveal history of taking medicines for obesity. Combination of Metformin and Lasix potentiates effect of Metformin and aggravates hypoglycaemic effects and lactic acidosis.

In this scenario, a fasted patient who probably took a dose of Metformin and Lasix, developed hypoglycaemia during surgery. One would anticipate that surgical stress response would combat this and increase blood glucose levels through increase in catecholamines. But it may not happen all the time.

The normal stress response to surgery is characterized by increased secretion of pituitary hormones and activation of sympathetic system. The overall metabolic effect is increased catabolism to provide energy and maintain homeostasis. Decrease in Insulin causing hyperglycaemia is the usual anticipated reaction in surgical patients. However, with the background of chronic intake of potentiating combination of drugs, it ceased to happen in our patient.

Causes of delayed recovery from anaesthesia must be methodically ruled out to arrive at the correct diagnosis. Some of the common causes include:

Medical: Hypoglycaemia, subclinical hypothyroidism, hypothermia, electrolyte imbalances

Prolonged action of anaesthetics and analgesics (check for neuromuscular reversal, opioid effect)

Surgical: Bleeding, acidosis, large fluid shifts

In spite of such an experience, I nearly missed the history of metformin intake in a young 20-year-old during a pre-operative visit. She was to have a maxillary osteotomy, and I saw her a week before the procedure as she was hypothyroid on medication. On completion of history taking, and examination, just as she was about to leave after discussion, she suddenly turned and mentioned that her doctor had prescribed metformin for weight reduction and she had forgotten to mention it when asked! Indiscriminate use of several drugs is on the rise, and it is preferable to ask the patients to bring their prescription and the medicines during the pre-operative visit.

References

1. Standards of Medical Care for patients with Diabetes Mellitus. American Diabetic Association, Diabetes Care, 2007, 30 (Supplement 1):4-41

2. Donnelly, Andrew J, 2009. Anaesthesiology and Critical care book. 8th edition. Ohio: Lexi-Com

3. Metformin and weight loss – Diabetes Daily https://www.diabetesdaily.com › Forum › General › Type 2 Diabetes May 18, 2017 – 10 posts – 6 authors

POST-OPERATIVE – Chapter 8

Delayed Recovery in Infant

A 11 months old boy weighing 9 kg was posted for surgical corrections of congenital hernia. On preoperative evaluation, he had no previous medical or surgical history and all his milestones were achieved appropriately. The investigations done– haemoglobin, bleeding time and clotting time were within normal limits. He was taken up for surgery under general anaesthesia, induced with Propofol 30 mg and intubated with Atracurium 6 mg. Caudal anaesthesia was given with 4 ml of 0.5% Bupivacaine and 2 ml of 1% Lignocaine. For maintenance 50% Oxygen and Nitrous Oxide and1 % Sevoflurane were used. The surgery was completed in about 60 minutes with a total relaxant dose of 8 mg.

At the end of surgery, the boy did not recover as expected. His HR was 128/min, after reversal with Neostigmine 0.5 mg and Glycopyrrolate 0.1 mg, he was semi-conscious, his breathing remained shallow, and his body was limp. The cause of delayed recovery could not be immediately identified.

At that point, a case of undiagnosed myopathy was suspected. However, blood sample was sent to check for serum electrolyte levels and glucose. The result of blood glucose was 41 mg/dl. This hypoglycaemia was corrected with 30 ml of 10% Dextrose over half an hour, after which he regained consciousness, and was extubated successfully. On subsequent follow up and investigations, he was diagnosed to have juvenile diabetes.

Discussion

Hypoglycaemia as a cause for delayed recovery must be suspected, even in paediatric population. Stress normally causes release of sympathomimetic agents and thereby increased glucose levels. However, in susceptible patients, it can cause serious hypoglycaemia, which can be catastrophic.

Risk factors for hypoglycaemia in children:

Long periods of starvation, over hydration with intravenous fluids not containing Dextrose, Neonates born to diabetic mothers, recent sepsis, viral infections, altered metabolism, syndromes including endocrinopathies like hypothyroidism, or hypopituitarism.

Some of the disease patterns recognized with hypoglycaemia include permanent neonatal diabetes, juvenile diabetes, pancreatic syndromes, and asymptomatic hypoglycaemia. This is a reversible cause in terms of recovering the patient from anaesthesia, provided it is recognised on time and treated. Efforts must be taken to maintain adequate glucose levels.