Timing of Prophylactic Antibiotic

Dr. Vasanthi Vidyasagaran*

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


A 24-year-old woman was posted for a caesarean section. She was an ASA II patient with history of hyperemesis. She had persistent nausea throughout her pregnancy. In spite of explaining the risks involved, the patient preferred general anaesthesia.

The patient was premedicated with injections Ranitidine, Ondansetron and Glycopyrrolate half an hour before surgery. She was induced with Thiopentone 250 mg, and Succinylcholine 75 mg was administered. While holding the mask, just before intubation, there was a hiccup and secretions poured from the mouth. Suction was applied, quick intubation performed, and cuff immediately inflated. The reservoir bag felt tight on ventilation. Injection Hydrocortisone 100 mg was given IV. Subsequent course of anaesthesia, and recovery was uneventful.

On further analyzing the situation, it was revealed that the staff nurse had given 2 g of injection Cefazolin as antibiotic prophylaxis after inducing the patient without informing the anaesthetist. The drug was given when the anaesthetist had turned from the patient to pick up the scope and the tube! She was a case of hyperemesis, and i.v. antibiotic probably had caused the vomiting and fortunately in this case, a major catastrophe was avoided.


Aspiration pneumonitis. There are four types of aspiration pneumonitis.

  1. Chemical,
  2. Bacterial,
  3. Due to inhalation of fumes, or
  4. Due to foreign body in the airway

In Mandelson’s syndrome it is chemical pneumonitis, and the presentation is acute with rales and rhonchi and drop in saturation leading to quite severe hypoxia. Morbidity and mortality can be prevented only if the condition is recognized early and prompt vigorous treatment initiated.


1. Hawn MT, Richman JS, Vick CC, et al. Timing of Surgical Antibiotic Prophylaxis and the Risk of Surgical Site Infection. AMA Surg. 2013.

2. Zhang C, Zhang L, Liu X, Zhang L, Zeng Z, Li L, et al. Timing of Antibiotic Prophylaxis in Elective Caesarean Delivery: A Multi-Center Randomized Controlled Trial and Meta-Analysis. PLoS ONE. 2015;10(7): e0129434.


Unexpected Hypermagnesemia

A 56-year-old man was booked for elective endoscopic nasal polypectomy. He had been living abroad the preceding few years and returned to India recently. He denied any significant medical history. He was on multivitamin supplementation. He was taken up as ASA I patient, body weight of 85 kg, non- smoker, with no known allergies.

Surgery was completed uneventfully under general anaesthesia, maintenance with Sevoflurane/Oxygen/Air. Analgesia given with local infiltration and systemic Fentanyl 100 mcg and Paracetamol 1gm. Atracurium 80 mg was used over a period of 2 hours.

It was 30 minutes since the last dose of Atracurium.

Patient did not make adequate efforts at breathing. After waiting for another 20 minutes, he made reasonable efforts, amounting to tidal volumes of approximately 150 ml. Reversal was then administered. The pattern of breathing was not rhythmic and tidal volume still remained around 200 ml. Hence injection Calcium Gluconate 10 ml was given to the patient over a period of 10 minutes. There was significant improvement in respiratory pattern and response to command. He was then extubated after making sure breathing was adequate.

Post operatively patient was well and vitals were maintained. Looking through the medications he had, it was surprising to know that they were magnesium supplements and not plain multivitamin tablets, and that it was quite commonly used a dietary supplement in the country where he lived. Magnesium levels could not be checked in that setting, and it seemed quite unnecessary, as the patient responded to calcium. Although hypermagnesemia from oral ingestion is rare, the exact reason for his delayed recovery and responding to calcium is also unknown, a diagnosis of hypermagnesemia may be considered.

A fatal case of hypermagnesemia has been reported following use of Epsom salt for halitosis!


Magnesium is the fourth abundant cation in our body and second abundant intracellular electrolyte. It is essential for oxidative phosphorylation, protein synthesis, amino acid activation, glucose use and a dependent cofactor in more than 300 enzyme systems in our body. Magnesium is described as physiological antagonist of calcium.

Relevance in anaesthesia

1. The well-known potentiation of neuromuscular block seen with elevated plasma magnesium concentrations is the result of competition by magnesium for calcium channels in the pre-synaptic nerve terminal, inhibiting acetylcholine release at the motor endplate. Similar inhibition of calcium-mediated neuroendocrine secretion by magnesium has been demonstrated, particularly of the release of catecholamine, with clinically useful effects.

2. Raised magnesium levels cause vasodilation and platelet inhibition, thereby potentiate bleeding during surgery.

3. Magnesium as therapeutic drug may be given to patients with cardiac dysrhythmias, glycoside toxicity, as part of multivitamin tablets, chronic obstructive airway disease, patients with muscle spastic diseases. In these scenarios, there are high chances that serum magnesium levels may cross therapeutic levels and affect other systems. Also, drug interactions make them susceptible to muscle weakness, delayed respiratory function and recovery due to altered calcium balance at cellular level.

Magnesium as a therapeutic, and preventive drug, is very useful in the perioperative period and in critical care unit. Therapeutic uses of magnesium include:

  1. Antihypertensive: Preeclampsia (PIH)
  2. Anticonvulsant: Eclampsia (PIH)
  3. Tocolytic: Uncontrolled severe bronchospasm
  4. Antiarrhythmic: Atrial fibrillation, Torsades de Pointes
  5. Neuroprotective: In subarachnoid haemorrhage
  6. Antispasmic: Tetanus
  7. Sedation and analgesia
  8. Sympatholytic effect: obtund response due to catecholamine
  9. Critical care unit: Maintaining electrolyte balance to ensure appropriate cellular milieu

Magnesium has an important role in anaesthesia and critical care. More research in electrolytes and anaesthesia, particularly the role of Magnesium will be of great use for future practice of anaesthesia.


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  6. Causes and treatment of hypermagnesemia. Up to date.