Intraoperative hyperthermia: Can surgery itself be a cause?

INTRODUCTION

Hyperthermia is defined as the body temperature of >37.5°C due to failed thermoregulation.[1] Body temperature is controlled by the hypothalamus and even minor deviations from normal can be manifested as cellular and tissue dysfunction.[2] Causes of perioperative hyperthermia include dehydration, fever, premedication with anticholinergic drugs, excessive surgical draping, malignant hyperthermia, thyroid storm, neuroleptic syndrome, septicaemia, allogenic blood transfusion and excessive heat delivery from the radiant warmers. Acute hyperthermia lasting for hours during excision of sellar-suprasellar mass has never been reported before. We report a case of intraoperative hyperthermia in patients with sellar-suprasellar mass.

CASE REPORT

A 40-year-old 51 kg American Society of Anesthesiologists physical status 1 female patient presented with the complaints of headache for 3–4 years and diminution of vision for the past 6 months. There was no history of fever, vomiting, seizures, altered sensorium, drug allergy, weight loss, heat or cold intolerance, chest pain and breathlessness. Her Glasgow Coma Scale was 15 and her general physical examination, systemic, airway and routine haematological investigations were normal. Magnetic resonance imaging of the brain showed a large sellar-suprasellar lesion invading the right cavernous sinus with enlargement of the right internal carotid artery, displacement of right temporal lobe laterally and splaying of optic chiasma [Figure 1] and the patient was scheduled for craniotomy and excision of the intracranial lesion.

Figure 1.

Magnetic resonance imaging showing the sellar suprasellar lesion

A general anaesthesia protocol with propofol, fentanyl, rocuronium, sevoflurane, nitrous oxide and oxygen was used. We monitored electrocardiography, end-tidal CO₂(ETCO₂), pulse oximetry, nasopharyngeal temperature, anaesthetic gases, invasive blood pressure, central venous pressure and urine output throughout the procedure. The patient's temperature was 35.8°C following anaesthesia induction. After 2 h of uneventful surgery, a progressive rise in the nasopharyngeal temperature was observed [Figure 2] and the temperature went up to 38.4°C. Intraoperative serum electrolytes and arterial blood gas analysis findings were within normal range (excepting a marginally increased arterial partial pressure of CO2). There was no change in vitals and the ETCO₂ was marginally increased.

Figure 2.

Image of the monitor showing rising trend of patient temperature

The patient was exposed to the ambient temperature environment as much as possible and intravenous paracetamol was administered. In spite of all our efforts, patient's temperature kept on rising and reached 38.9°C. We infused ice-cold saline through the central venous line, but no significant response was observed. The surgical team was informed about the progressive rise in temperature coinciding with the surgical handling of the hypothalamus due to on-going resection of the tumour adherent to it. The surgeons proceeded further with minimal or no handling of hypothalamus and within next 30 min, the tumour could be removed. Following resection, there was no further rise in body temperature and came down to 36.1°C over next 60–70 min. Rest of the surgery was uneventful and the patient was shifted to neurosurgical Intensive Care Unit (ICU) for elective ventilation. The patient had an uneventful 2 days of ICU stay and was shifted to neurosurgical ward thereafter.

DISCUSSION

Causes of intraoperative hyperthermia are drug reactions, septicaemia, thyroid storm, neuroleptic malignant syndrome, lighter plane of anaesthesia, excessive heat delivery by radiant warmer and malignant hyperthermia. There was no history of any drug reaction in the past and there were no significant haemodynamic changes. The patient was afebrile preoperatively, and she did not have any signs and symptoms of septicaemia. There was no history of intake of drugs known to cause intraoperative hyperthermia.[3] There were no signs suggesting malignant hyperthermia in our patient[4] making it an unlikely cause of the event.

Neurons in the preoptic anterior hypothalamus, posterior hypothalamus and the thermoregulatory centre in the hypothalamus regulate the body temperature. Intraoperative hyperthermia can occur due to hypothalamic injury. Post-traumatic hyperthermia is a non-infectious elevation in body temperature that is frequently mistaken for fever in the patient with traumatic brain injury and is thought to be caused by traumatic injury to hypothalamus resulting in a disruption in the hypothalamic set point temperature which causes an abnormal increase in body temperature. Acute damage to hypothalamus can cause a transient rise in body temperature lasting for 6 weeks and lesions in mid hypothalamus can cause persistent hyperthermia.[5,6] Hence, the most probable cause of hyperthermia in our patient was hypothalamic injury due to hypothalamic handling during surgery and this assumption is further substantiated by normalisation of temperature in the absence of handling of brain tissue in the vicinity of the hypothalamus. Intraoperative hyperthermia is not a universal phenomenon during sellar-suprasellar tumour resection. However, it can occur if the sellar-suprasellar mass lesion is large with extension to surrounding brain areas.

CONCLUSION

Intraoperative hypothalamic handling during sellar-suprasellar surgery can be a cause of intraoperative hyperthermia, and the surgeons must be informed in time so that they can also participate in the management of such a condition in time by careful dissection in the vicinity of the hypothalamic region.

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Conflicts of interest

There are no conflicts of interest.