Proper preparation of the patient is very necessary for the operative procedure. If patient is on any nonsteroidal antiinflammatory agent, it should be discontinued before surgery. In case of females birth control pills should be discontinued 1 month before surgery [Increase the possibility of thrombophlebitis in the postoperative period].
Patient should be evaluated with preoperative radiographic evaluation of the spinal levels. Computed tomography, magnetic resonance imaging, and myelography rule out conditions such as syringomyelia, diastematomyelia, and tethered cord.
In patients with severe curves pulmonary function studies usually are indicated.
Autologous blood donation in preoperative period in patients who are fit for autodonation is good option. Autologous donation reduces the the risks of homologous blood transfusion. Erythropoietin is another good but costly option.
Spinal surgery requires extensive dissection and it may result in severe blood loss. Therefore a large bore intravenous line is necessary in these cases. Following routine gadgets are used for patient monitoring
- Arterial line- continuous monitoring of blood pressure.
- Indwelling urinary catheter – monitor urinary output.
- Blood pressure cuff
- Esophageal stethoscope
- A pulse oximeter
Hypotensive Anesthesia and Other Methods to Reduce Blood Loss
Hypotensive anesthesia is the one in which arterial blood pressure is kept at 65 mm Hg. Hypointensive anesthesia is an effective way to reduce the loss of blood during surgery.
The cell saver is another method where one is able to save 50% of the red cell mass. However, cost could be a deterring factor for usage.
Acute normovolemic hemodilution is another option to decrease loss of red cells. The maximum quantity of blood is withdrawn to reach to a level of 9 g/dL or higher after hemodilution and volume is maintained by crystalloid replacement. The surgery is conducted at normal blood pressure and diuresis of excess fluid is performed after surgery is finished followed by the transfusion of initially removed blood .
Somatosensory evoked potentials involve stimulation of distal sensory proximal to the surgical area and can alert the surgeon to possible alteration of spinal cord transmission. Preoperative baseline can be compared with one during the surgery. Drugs like halothane, isoflurane, diazepam and droperidol should be avoided. False-positive and false-negative results have been reported.
As it measures only the integrity of the sensory system, the use of motor evoked potentials has increased. The combination of motor evoked potentials and somatosensory evoked potentials can provide important information regarding the primary motor and sensory tracts within the spinal cord.
Stagnara wake-up test
Stagnara wake-up test, the anesthesia is decreased or reversed after correction of the spinal deformity. The patient is brought to a conscious level and asked to move both lower extremities. Once voluntary movement is noted, anesthesia is returned to the appropriate level, and the surgical procedure is completed.