Intraoperative Crisis Management in Spine Surgery: What to Do When Things Go Bad

Published on 27/03/2015 by admin

Filed under Neurosurgery

Last modified 27/03/2015

Print this page

This article have been viewed 2678 times

Chapter 203 Intraoperative Crisis Management in Spine Surgery

What to Do When Things Go Bad

Kalil G. Abdullah, Eve C. Tsai, Edward C. Benzel, Michael P. Steinmetz

Complications in spine surgery may occur in spite of the surgeon’s best attempts at prevention. The previous chapters of this text addressed the prevention and management of complications. This chapter addresses the management of catastrophic intraoperative and perioperative complications.

Many types of complications in spine surgery have been reported, but most are not crises. A crisis requires swift and decisive action by the health-care team. The crises outlined in the following discussion refer to those in which action must be taken intraoperatively or during the immediate postoperative period. We do not discuss complications that do not require immediate action (e.g., while a nerve root avulsion is a major complication, it does not require immediate action). Here, we divide crisis management into four sections: (1) anesthesia-related crises, (2) surgical crises, (3) electrophysiologic spinal cord monitoring issues, and (4) neurologic injuries.

Anesthetic Crises

Prone Cardiopulmonary Arrest

Most spine operations are carried out in the prone position. However, this position may present some difficulty for the anesthesiologist by interfering with monitoring techniques, altering respiratory function, and limiting airway and vascular access.¹ Cardiac arrest in patients who undergo surgery in the prone position is very uncommon. The major preoperative risk factor is understandably cardiac disease, while intraoperative factors include hemorrhage, gas embolism, and diminished venous return.² The rare occurrence of cardiac arrest during spine surgery and modern anesthetic techniques nearly obviate the need for cardiopulmonary resuscitation (CPR) in the operating room. Nevertheless, it may be necessary in some circumstances. The prone position substantially complicates cardiopulmonary arrest management for several reasons. First, the time necessary to procure a stretcher and turn the patient to the supine position to perform CPR may delay therapy. The wound must be closed quickly, risking infection and costing valuable time. Interruption of the surgical procedure may also leave the spine unstable, risking further injury. Additionally, spinal implants may not be fully attached or may protrude from the wound.

Turning the patient might not be feasible in some situations, owing to the risk of neurologic injury. In these situations, the resuscitation begins with the anesthesiologist, while the wound is being closed. However, the surgeon must initiate CPR. Two options are available in these situations. Closed CPR in the prone position has been described and is typically used first.¹^–³ If sternal support is present, the surgeon may place his or her hands on either side of the incision at the midthoracic level with the palms placed over the patient’s scapulae¹ (Fig. 203-1). Compression is then initiated. The arterial wave form, blood pressure, and end-tidal CO₂ should be observed to monitor cardiac output and adequacy of resuscitation. If there is no sternal support (e.g., the patient is placed on chest rolls), the surgeon may clench a fist and place it under the patient’s chest over the lower third of the sternum³ (Fig. 203-2). This requires a break in sterility. The surgeon’s other hand (or an associate’s) then compresses at the midthoracic level.

FIGURE 203-1 When sternal support is available, the surgeon may place his or her hands on either side of the spine at the midthoracic level for compressions during CPR. (Copyright Cleveland Clinic Foundation.)

FIGURE 203-2 When there is lack of sternal support, the surgeon or assistant may place a clenched fist on the lower sternum, and the other hand may compress at the midthoracic level during CPR. (Copyright Cleveland Clinic Foundation.)

If the aforementioned techniques are not feasible or are unsuccessful owing to lack of adequate cardiac output or in the presence of spine instability, the surgeon has the option to perform a left dorsal thoracotomy.³ This procedure provides direct access to the heart. Following exposure, open internal cardiac massage or defibrillation may be performed (Fig. 203-3).

FIGURE 203-3 Left dorsal thoracotomy. An incision is made between the ribs. The dissection is taken down to and through the intercostal muscles. The parietal pleura is incised. The heart may now be visualized, and internal cardiac massage may be undertaken. (Copyright Cleveland Clinic Foundation.)

Air Embolism

Intraoperative venous air embolism (VAE) occurs most commonly when patients are in the sitting position. For this reason, surgeons often avoid the sitting position. Negative pressures are greater in the sitting position, owing to the elevation of the head. However, it should be noted that VAE can occur in any position in which the head is elevated at a higher level than the heart. Depending on the type of monitoring technique that is used, the overall incidence of air embolism has been reported to be anywhere between 25% and 50% in surgeries involving the posterior fossa.⁴ The incidence during cervical laminectomy has been estimated at 25%.⁵ In one study in which transesophageal echocardiography was used, 100% of patients in the sitting position demonstrated VAE.⁶ While the occurrence of VAE may be high, its sequelae remain low as long as appropriate measures to treat the embolism are carried out rapidly. During surgery in the sitting position, appropriate monitoring should be used. This includes the use of the electrocardiograph, arterial catheter, right atrial or pulmonary artery catheter, end-tidal CO₂ monitor, and a precordial Doppler (the most sensitive and practical monitor for VAE).

These devices allow for the early detection and treatment of VAE prior to paradoxical air embolism or cardiopulmonary incident. Most frequently, the initial indication of the presence of VAE is the precordial Doppler. A significant VAE elicits audible Doppler indicators and possibly a decrease in end-tidal CO₂, ventricular arrhythmias, and hypotension and/or an increase in pulmonary artery pressure. At the first indication of VAE, the surgeon should flood the operative field with saline, wax all bleeding bone edges, and occlude any visual sources of venous bleeding. Bilateral jugular venous compression by the anesthesiologist increases the central venous pressure and may help in identifying the venous source. If only one jugular vein can be compressed, the right one should be chosen. The anesthesiologist should discontinue nitrous oxide infusion, as this has been shown to enlarge the gas volume of air-containing cavities.^7,⁸ Positive end-expiratory pressure should be discontinued (it may alter right-to-left atrial pressure gradients and facilitate the passage of air across an existing patent foramen ovale), and air should be aspirated by using a right atrial catheter if one is available.^9,¹⁰ These steps should lead to the resolution of VAE-related symptoms. The patient may also be placed in a head-down position with the patient’s right side up in order to trap air in the right atrium to aid in aspiration of the air bolus and minimize pulmonary and cerebral ischemic complications, but this is rarely required.¹¹

If the aforementioned maneuvers resolve the symptoms, the procedure may be completed as planned. If the VAE is severe and does not respond to therapy or continues to progress, then the procedure should be terminated. Surgery may be completed at a later date, with modification of position such as utilizing a prone position rather than a sitting position.

Surgical Crises

Vascular Injuries

Cervical Approaches

Vertebral artery injuries in the cervical spine are uncommon but potentially catastrophic. The ventral approach places both the carotid and vertebral arteries at risk for injury, but the carotid artery is fully visualized during ventral exposure and therefore is rarely injured.¹² If injury does occur, it can be readily identified and controlled with direct pressure, with or without primary vascular repair. Shunting or temporary clamping of the carotid artery may be performed while a primary or patch repair of the artery is performed.

The ventral and dorsal cervical approaches both place the vertebral artery at risk for injury. In the anterior approach, the rate of injury has been estimated to be between 0.3% and 0.5%.¹³^–¹⁷ Injury during the ventral approach can occur because of excessive lateral bone–disc removal, drill use too far off midline into the uncinate processes, subperiosteal elevation of the longus colli muscles, vertebral artery anatomic anomalies, or the softening of bone of the lateral part of the spinal cord owing to pathologic processes.¹⁷ Injury to the vertebral arteries during posterior cervical screw placement in the subaxial spine is considered to be rare and generally due to improper drilling and poor trajectories during placement.¹⁸

The vertebral artery is hidden within the foramen transversarium, and initial injury to the artery is usually announced by the presence of brisk, bright red arterial bleeding. Occasionally, darker venous bleeding may be seen if damage has been done to the neighboring venous plexus. The management of vertebral artery damage in the subaxial spine is diagrammed in Fig. 203-4. First, manual pressure and the use of a hemostatic agent should be employed at the site of suspected injury. When bleeding is under control, time is available for the anesthesiologist to “catch up” with regard to volume replacement and, if necessary, blood transfusion. Proximal and distal control of the artery should be attempted. In either a ventral or a dorsal approach, the transverse process should be dissected to expose the artery one level above and below the injury. A high-speed drill with a diamond tip bur may be used to open the foramen transversarium and expose the artery. An aneurysm clip may be placed to achieve temporary control of bleeding during injury repair.¹⁴ Primary repair of the artery should be considered. If reconstruction of the artery cannot be achieved, it should be ligated proximally and distally.

FIGURE 203-4 Algorithm for the treatment of iatrogenic injury to the vertebral artery during cervical spine surgery. Note this should be viewed in the setting of an inability to control bleeding from an injured vertebral artery. If the bleeding can be stopped with packing and hemostatic agents, a clinical decision may be made to either manage expectantly if the patient remains stable clinically or proceed to angiography for potential endovascular repair or occlusion.

If bleeding can be controlled with packing or hemostatic agents, consideration should be given to completion of the operation. Instrumentation should be placed on the side contralateral to the side of injury with great care, if at all. Consideration must be given to the chance of occlusion or damage of the contralateral vertebral artery and the morbidity and/or mortality that may occur as a result.

Intraoperative angiography may be considered.¹⁷ Once primary control of the bleeding has been attained, the patient can be taken to the endovascular suite and the vertebral artery can be stented or occluded. Perioperative management remains controversial, with some surgeons choosing immediate postoperative angiography while others reserve further intervention to be based on the patient’s observed clinical course.¹⁹

Injury during C1-2 transarticular screw placement has been reported to be as high as 2.2% per screw.¹⁹ As in the subaxial spine, injury to the vertebral artery is often heralded by brisk arterial bleeding seen during drilling or K-wire placement. Control of the hemorrhage can be obtained by placing the transarticular screw into the drill hole or by packing the hole with bone wax. Placing the screw into the drill hole is preferred, as it both plugs the hole and provides stability. The opposite screw should not be drilled or placed. Doing so invites a high risk of disastrous sequelae associated with bilateral vertebral artery injury.

Dorsal Thoracic and Lumbar Approaches

Vascular injury during dorsal thoracic surgery is rare. Therefore, the following discussion is limited to dorsal lumbar approaches. Lumbar disc surgery is one of the most commonly performed spine operations. The incidence of vascular complication has been recently estimated to be 0.14% at the most.²⁰^–²³ The most commonly injured vessels are the common iliac arteries.²⁴ Other potentially injured vessels are the left common iliac vein, median sacral artery, aorta, and inferior vena cava.

Vascular injury is typically caused by aggressive use of a pituitary rongeur that penetrates the ventral anulus fibrosus and causes breach of the vessel wall.²⁵ Neither surgeon experience²⁶ nor amount of disc material removed²⁵ has been demonstrated to affect the incidence of this injury. Brisk bleeding into the interspace is observed in only 25% of these injuries, and so may not be immediately evident to the surgeon.²⁵ When brisk bleeding is observed, it may actually be due to damage to extradural veins and not an arterial injury.²⁶

The injury is usually recognized in the recovery room, although with venous injuries, the symptoms and signs of injury can be delayed. The patient is most often hypotensive and tachycardic and has abdominal distention and pain. Pallor and weak pulses are also usually present. The patient should immediately be taken back to the operating room for laparotomy. Cross-clamping of the aorta can facilitate resuscitation.²⁵ All vessels should be carefully inspected. A tear in a vein may be primarily repaired with suture. The iliac artery may be divided to gain access to an injured vein and then must be reanastomosed. Arterial injuries may be repaired primarily or with an interposition graft. Damage to an internal iliac vessel (artery or vein) may be repaired by ligation if primary repair is not possible.

Ventral Thoracic and Lumbar Approaches

The incidence of vascular injury during the ventral approach to the lumbar spine has recently been estimated to be between 11% and 12%.^27,²⁸ However, the majority of injuries are venous and require only simple suture or clip repair. Major crises occur at a rate of only 2%.²⁷ Injury usually occurs during exposure and is more likely to occur with exposure of L4-5.²⁷ Chances of injury increase with use of preoperative radiation therapy or if osteomyelitis is present. Vessels that potentially can be injured include the left iliac vein, the iliolumbar vein, the middle sacral vessels, and the left iliac artery. During ventral exposure and dissection, the middle sacral vessels (Fig. 203-5A) and iliolumbar vein (Fig. 203-5B) should be identified and ligated. If sudden hemorrhage occurs, direct pressure is applied to the vena cava, and identification of the injured vessel is attempted. A torn lumbar or iliolumbar vein may be clamped and ligated. If an iliac vein injury is suspected, direct pressure should be applied, and then proximal and distal control of the vein should be achieved. The perforation can then be repaired primarily.²⁹ If an artery is injured, proximal and distal control must be attained, and the injury is repaired either primarily or with an interposition graft.