Anaesthetic concerns of a pregnant patient with Pott's spine for spine surgery in prone position.

Abstract

Sir, Surgical decompression is the treatment of choice in pregnancy complicated by spinal tuberculosis with neurologic deficit.[1] We report the anaesthetic management of a pregnant patient with Pott's spine in prone position and discuss the various anaesthetic concerns including haemodynamic instability. A 23-year-old multipara, 17 weeks of gestation, weighing 52 kg, with Pott's spine involving T7–T10 segments with progressive neurological deficit was scheduled for decompression and posterior screw fixation. Obstetrician's opinion was sought. Preoperative foetal heart rate (FHR) was documented. Anti-aspiration prophylaxis was administered. Her baseline HR was 112/min and blood pressure (BP) was 132/82 mmHg. Invasive arterial BP monitoring could not be done due to the logistic problems. General anaesthesia was induced with propofol and morphine. Endotracheal intubation was facilitated using vecuronium with size 7.0 orotracheal cuffed tube. Injection glycopyrrolate 0.2 mg was administered as anti-sialagogue. Anaesthesia was maintained with isoflurane in 50% nitrous oxide and oxygen mixture. Soon following positioning, patient developed hypotension i.e., more than 20% fall from the baseline systolic BP (SBP). Fluid replacement and pressure-free abdomen were rechecked but the SBP continued to remain between 90 and 100 mmHg. Initially, hydrocortisone 100 mg was administered intravenously. The oozing from the surgical site resolved following injection tranexamic acid 500 mg. Surgery lasted for 5 h but BP persisted in the same aforementioned range. Blood loss was 1000 ml approximately. Haemodynamics and FHR remained stable post-operatively. The anaesthetic concerns related to spine surgery in pregnant patient include both obstetric and surgery-related i.e., prolonged surgery in prone position, major blood loss, relative hypotension and risk of postoperative visual loss.[2] The risk of radiation is of paramount concern due to the inability to use abdominal shield and the proximity of radiation to the foetus. The additional problem with prone position here includes the inability to perform emergent caesarean section. Technical problems may limit the usefulness of continuous FHR monitoring between 16 and 20 weeks and it is recommended to document FHR before and after surgery which was done in our patient. The American College of Obstetricians and Gynaecologists recommends continuous FHR monitoring in non-obstetric surgery from 18 to 20 weeks of gestation, based on the patient and the surgery to be performed.[3] There has been controversy related to the use of controlled hypotension and intraoperative tests/monitoring to detect spinal cord injury during pregnancy. Invasive arterial BP monitoring must be performed, more so, if controlled hypotension is instituted. Various risk factors for haemodynamic instability in these patients include pregnancy-induced aortocaval compression, massive fluid shift, blood loss and prolonged surgery. In addition, autonomic dysfunction has been reported as the cause for high incidence of intraoperative hypotension in adult patients with thoracic spine tuberculosis.[4] In our patient, vasopressor was not considered to treat hypotension:First, because, as the SBP remained in the acceptable range of 90–100 mmHg, and second, its use could have further led to increased blood loss. Since the hypotension occurred soon after positioning, it could be attributed by factors such as pregnancy-induced aortocaval compression, pre-operative hydration status and autonomic neuropathy related to thoracic spine tuberculosis. The initial two factors were ruled out by ensuring adequate fluid replacement and free and hanging abdomen in prone position. It is also reported that prone position in pregnant patient is associated with lesser risk of aortocaval compression than sitting or lateral position.[5] To conclude, intraoperative haemodynamic stability is of paramount anaesthetic concern in pregnant patients with thoracic spine tuberculosis and autonomic dysfunction must be considered as a potential cause for intraoperative hypotension. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.