Major Spine Surgery Research Articles

Cerebellar-evoked potentials and nitrous oxide in healthy subjects

INTRODUCTION: Evoked Potential monitoring has become common practice during major spinal surgery. The aim is to alert the surgical team to impending ischaemic damage and avoid permanent neurological injury. The most common modality used is Somatosensory Evoked Potential (SSEP) monitoring. However, SSEPs have some important limitations. They are known to be influenced by commonly used anaesthetic agents.(1). SSEPs are carried via the dorsal columns so monitoring of SSEPs alone may allow a ventral cord defect to go undetected. Cerebellar Evoked Potentials (CEPs) have been reported as a potential monitor of ventral cord integrity. (2,3). A pilot study in the intraoperative setting has suggested that CEPs are robust during general anaesthesia.(4). The purpose of this study is to characterize these evoked potentials and to determine the effect of nitrous oxide in healthy volunteers.

Renal effects of hypotensive anaesthesia in combination with acute normovolaemic haemodilution with hydroxyethyl starch 130/0.4 or isotonic saline

Hypotensive anaesthesia (HA) and acute normovolaemic haemodilution (ANH) are used separately to decrease per-operative blood loss. Reducing blood viscosity by adding ANH to HA may appear profitable in a situation with lowered perfusion pressure and concern about organ ischemia. The aim of this study was to clarify the influence of HA in combination with ANH using crystalloid or colloid as replacement fluid on renal function. Hypotensive anaesthesia was induced in 11 patients referred to major spine surgery using sevoflurane in combination with fentanyl/remifentanil. Acute normovolaemic haemodilution was carried out by drawing venous blood into standard blood bags and replacing it by isotonic saline 0.9% (Group S) or HES 130/0.4 (Group V). Renal function was evaluated before, during and up to 8 h after hypotension as the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) by means of 51Cr-EDTA and 125I-Hippuran clearances. Lowering mean arterial blood pressure decreased GFR and ERPF in both groups. During hypotension ERPF was lower in Group S (n = 5) than Group V (n = 6). Renal function was normalized postoperatively. We found a positive but non-significant correlation between the relative GFR change and the duration of hypotension. In conclusion, our study demonstrated that renal function, assessed by GFR and ERPF, is transiently reduced during the combination of hypotensive anaesthesia and acute normovolaemic haemodilution. A colloid-based fluid regime (HES 130/0.4) used for haemodilution may preserve renal function to a greater extent than a crystalloid-based regime (0.9% saline).

Analysis of nutritional parameters in idiopathic scoliosis patients after major spinal surgery

The aim of the study is to investigate the evolution of nutritional parameters after major spinal surgery in patients with idiopathic scoliosis. This retrospective study included 31 patients with a mean age of 18 y, diagnosed with idiopathic scoliosis. The following variables were analyzed: demographic, surgical (type, number of fused segments, duration, and blood loss), nutritional assessment (proteins, albumin, prealbumin, transferrin, lymphocytes, and body mass index), and duration of hospitalization at different time points. Statistical analyses were performed with the SPSS 6.1 software. Before surgery, nutritional status was normal in all patients. At 24-48 h after surgery, statistically significant decrease with respect to preoperative values was recorded for all the parameters studied: proteins (P < 0.001), albumin (P < 0.001), prealbumin (P < 0.01), transferrin (P < 0.001), and lymphocytes (P < 0.001). Our results showed a significant postoperative decrease in the nutritional parameters analyzed in a previously well-nourished population considered to be at low risk for nutritional depletion.

Epidural analgesia after spinal surgery via intervertebral foramen

Patients undergoing major spinal surgery may experience significant postoperative pain. Epidural analgesia has previously been shown to be safe and effective and may confer some advantages over opioid-based postoperative analgesia. We discuss the case of a 47-yr-old female patient undergoing the prolonged anterior component of a lower thoracic/upper lumbar spine correction involving the stripping of the diaphragm from the lower thoracic spine and retraction of the left lower lobe of the lung. Despite initially planning opioid-based postoperative analgesia, a joint anaesthetic and surgical decision was made to use epidural analgesia in an attempt to avoid potential postoperative respiratory complications. Because of the surgical anatomy of the correction, the catheter was inserted via the T11 intervertebral foramen. A bolus of bupivacaine 0.25% intraoperatively with a postoperative infusion of bupivacaine 0.167% with diamorphine 0.1 mg ml(-1) provided excellent analgesia. The technique was associated with no postoperative complications.

Efficacy of Aprotinin in Reducing Blood Loss in Paediatric Patients Undergoing Major Spinal Surgery.

Blood loss during corrective surgery for scoliosis and the requirement for homologous blood is an important issue in paediatric spinal surgery. This is particularly pertinent in cases of scoliosis secondary to underlying neuromuscular disease where anaemia may be less well tolerated, both intra-operatively and post-operatively, due to multiple organ dysfunction. Despite the introduction of techniques to minimise the necessity to transfuse homologous blood (pre-deposit autologous donation, cell salvage and isovolaemic haemodilution), it is often required. This brings with it the potential risks of allo-immunization and infective complications. In the UK homologous blood is an increasingly precious resource following the recent exclusion of donors who have themselves received blood products in the last ten years in view of the potential risk of new variant CJD.Aprotinin, a serine proteinase inhibitor (now produced by recombinant technology) with antifibrinolytic properties and the ability to preserve platelet function has been shown to reduce blood loss in major cardiac surgery and liver transplantation. Its effectiveness in the orthopaedic setting has generated more varied reports, however in the setting of spinal surgery for idiopathic scoliosis it has recently been shown to reduce intra-operative blood loss and the requirement for homologous transfusion.We report here our experience with the use of aprotinin in a group of paediatric patients undergoing surgery for scoliosis secondary to an underlying neuromuscular disorder and its effect on intra-operative blood loss. 33 successive patients referred to our institution were allocated to receive aprotinin (n=18) or not (n=15). For those who received the drug a test dose of 50,000KIU was followed by a loading dose of 10,000KIU/kg over 30 minutes. A maintenance infusion was set up at 5,000KIU/hour for the duration of the procedure.The demographics of the two groups were not significantly different. The median age of those children receiving aprotinin was 12 years (7–15) and those who did not 13 years (7–17), [p=0.09]. The median weight of the children receiving aprotinin was 40kg (25–55) and those who did not 38.5kg (21–55), [p=0.74]. The procedures undertaken were posterior spinal fusion (n=26), anterior and posterior fusion (n=3), insertion of growing rods (n=2) and correction of kyphoscoliosis (n=2). All procedures were performed by one of three consultants. The operative time in the two groups was not significantly different, 6.5 hours (4.1–8.9) in those who received aprotinin and 5.7 (4.4–7) in those who did not [p=0.54].There was however a significant reduction in blood loss in the group who received aprotinin, with an average reduction of 51.6%. Median losses for those who received aprotinin were 1380ml (380ml–2380ml) and 2849ml (1047ml–4651ml) for those who did not [p=0.01]. No adverse events in the form of allergic reactions were observed in the children who received the drug. We conclude that aptotinin is a safe and effective pharmacological intervention which can be used in spinal surgery to reduce operative blood loss. This should translate into a reduced requirement for homologous blood although this was not determined in this study. Evaluation of this secondary endpoint is ongoing.

Controlled hypotension for spinal surgery.

Controlled, deliberate hypotension during anesthesia for major spinal surgery reduces intraoperative blood loss and transfusion requirement. Hypotension may be achieved with increased doses of volatile anesthetic agents or by continuous infusion of vasodilating drugs. Safe application of this technique requires knowledge of the physiology of hemorrhagic shock and close intraoperative monitoring to avoid vasoconstriction and end-organ ischemia.

Tranexamic acid for major spinal surgery.

Patients who undergo major spinal surgery often require multiple blood transfusions. The antifibrinolytics are medications that can reduce blood-transfusion requirements in cardiac surgery and total knee arthroplasty. The present role of synthetic antifibrinolytics, especially tranexamic acid, in reducing peri-operative blood-transfusion requirements in spine surgery is still unclear. The majority of studies exploring the role of these drugs in spine surgery have limited patient enrollment and report mixed results. The goal of the present review is to discuss the pharmacology of tranexamic acid briefly. A brief synopsis of the studies using the synthetic antifibrinolytics for spine surgery is presented. Finally, the potential risks and the benefits of antifibrinolytics are discussed.

Pulmonary complications in anterior-posterior thoracic lumbar fusions

Background context Surgery for adult spinal deformity may require both an anterior and posterior approach in order to stabilize the spine and achieve the desired correction. These procedures can be associated with significant pulmonary complications, including atelectasis, pneumonia and respiratory failure. The etiology of some of the respiratory complications is clear: poor inspiratory effort from incision pain and previous pulmonary disease. However, for many patients the direct cause of these complications is not obvious. Purpose To delineate the incidence, severity and risks associated with pulmonary complications in the setting of major spine surgery. Study design/setting Retrospective chart review study of adult patients undergoing combined anterior-posterior thoracic, lumbar and sacral fusion spine surgery. Patient sample A total of 60 charts were reviewed for this study. Outcome measures Radiographic abnormalities correlated with clinical findings, postoperative need for ventilation and lengths of hospital stay were used as outcome measures. Methods Perioperative pulmonary complications were assessed for 60 patients with spinal deformities who underwent combined anterior-posterior thoracic, lumbar and sacral fusion over a 2-year period. Results One patient was eliminated from analysis because of multiple surgeries during his hospital course. Of the remaining 59 patients, 38 (64%) developed roentgenographic abnormalities. The most common radiographic finding was an effusion found in 66% of these patients, followed by atelectasis in 53%. Twenty-one percent (8 of 38) had infiltrates. Five (5 of 38) or 13% had evidence of partial or complete lobar collapse; in two bronchoscopy was required because of profound hypoxemia. Two patients had pneumonia requiring antibiotic treatment. All but two patients were extubated within 36 hours of surgery. They were kept intubated because of hemodynamic instability. There was no statistically significant difference in the group of patients with and without roentgenographic abnormalities with regard to age, weight, American Society of Anesthesiologists class, smoking history, pulmonary function test results, blood loss, perioperative blood and crystalloid requirement and length of surgery. Patients with radiographic abnormalities were more likely to have had invasion of their thoracic cavity (p=.02) and had a longer mean hospital stay of 13.5 versus 10.2 days (p=.009). Conclusion Radiographic abnormalities of the lungs are common after major spine surgery involving both an anterior and posterior approach, especially when the thoracic cavity is invaded. In view of the morbidity and longer hospital stay associated with such findings, close monitoring of pulmonary status with aggressive pulmonary toilet are indicated.

Pulmonary complications in anterior-posterior thoracic lumbar fusions*1

Background context Surgery for adult spinal deformity may require both an anterior and posterior approach in order to stabilize the spine and achieve the desired correction. These procedures can be associated with significant pulmonary complications, including atelectasis, pneumonia and respiratory failure. The etiology of some of the respiratory complications is clear: poor inspiratory effort from incision pain and previous pulmonary disease. However, for many patients the direct cause of these complications is not obvious. Purpose To delineate the incidence, severity and risks associated with pulmonary complications in the setting of major spine surgery. Study design/setting Retrospective chart review study of adult patients undergoing combined anterior-posterior thoracic, lumbar and sacral fusion spine surgery. Patient sample A total of 60 charts were reviewed for this study. Outcome measures Radiographic abnormalities correlated with clinical findings, postoperative need for ventilation and lengths of hospital stay were used as outcome measures. Methods Perioperative pulmonary complications were assessed for 60 patients with spinal deformities who underwent combined anterior-posterior thoracic, lumbar and sacral fusion over a 2-year period. Results One patient was eliminated from analysis because of multiple surgeries during his hospital course. Of the remaining 59 patients, 38 (64%) developed roentgenographic abnormalities. The most common radiographic finding was an effusion found in 66% of these patients, followed by atelectasis in 53%. Twenty-one percent (8 of 38) had infiltrates. Five (5 of 38) or 13% had evidence of partial or complete lobar collapse; in two bronchoscopy was required because of profound hypoxemia. Two patients had pneumonia requiring antibiotic treatment. All but two patients were extubated within 36 hours of surgery. They were kept intubated because of hemodynamic instability. There was no statistically significant difference in the group of patients with and without roentgenographic abnormalities with regard to age, weight, American Society of Anesthesiologists class, smoking history, pulmonary function test results, blood loss, perioperative blood and crystalloid requirement and length of surgery. Patients with radiographic abnormalities were more likely to have had invasion of their thoracic cavity (p=.02) and had a longer mean hospital stay of 13.5 versus 10.2 days (p=.009). Conclusion Radiographic abnormalities of the lungs are common after major spine surgery involving both an anterior and posterior approach, especially when the thoracic cavity is invaded. In view of the morbidity and longer hospital stay associated with such findings, close monitoring of pulmonary status with aggressive pulmonary toilet are indicated.

Deep Vein Thrombosis Found Immediately after Lumbar Spine Surgery: A case report

We observed a patient who had a unilateral leg edema soon after lumbar spine surgery in the prone position. Spine patients have a number of risk factors for developing deep vein thrombosis (DVT) after or during surgery. These factors are; lengthy operative procedures, prone positioning on certain frames, and prolonged bed rest after surgery. Like these patients, estrogen users for replacement or contraception are three to four times more likely to develop DVT than non-users. So, anesthesiologist should check the risk factors of DVT in hormone replacement therapy users before major spine surgery, and perform antithrombotic prophylaxis, including elastic stocking, pneumatic compression to the calf and thigh, and careful prone positioning to avoid compression of the inguinal area. A special survey should be performed to evaluate whether postmenopausal women should discontinue hormone use before major spine surgery.

Pharmacologic and physiologic influences affecting sensory evoked potentials: implications for perioperative monitoring.

Pharmacologic and physiologic influences affecting sensory evoked potentials: implications for perioperative monitoring.

Use of epidural analgesia for pain management after major spinal surgery.

This is a retrospective study of the role of postoperative epidural analgesia in major spinal surgical procedures. With the number and complexity of the procedures performed on the spine ever-increasing, this method of analgesia is becoming more important. Results of 74 consecutive cases of major spinal surgeries between January 2000 and January 2001 at the Spine Division, Amritha Institute of Medical Sciences and Research Centre, Kochi, India, were studied. 32 cases were posterior procedures and the other 42 were anterior procedures of the thoracic and lumbar regions. The use of various combinations of local anaesthetic and opioid to control postoperative pain after spinal surgery were analysed. 36 (49%) of 74 patients did not require any parenteral supplements. Of the remaining 38 patients who required supplementary parenteral analgesia in the first 48 hours, 25 (34%) received a single dose and 13 (18%) required more than one dose. The number of patients requiring parenteral analgesia immediately after operation were 11; between 2 and 6 hours were 12; and between 6 and 24 hours were 11. Of the 74 patients, 67 had a sound sleep after epidural administration. There were 2 cases of respiratory depression and 2 of transient hypotension. Most epidural analgesic regimens significantly reduced postoperative pain, and the requirement for supplementary parenteral analgesics was minimal. Adverse effects were rare, yet we recommend that patients treated with this protocol be managed in high-dependency units.

Early Postoperative Respiratory Acidosis After Large Intravascular Volume Infusion of Lactated Ringer’s Solution During Major Spine Surgery

Early Postoperative Respiratory Acidosis After Large Intravascular Volume Infusion of Lactated Ringer’s Solution During Major Spine Surgery

Survey of anesthesia practice in spine surgery patients in the United States.

There is a wide range of anesthetic practice in spine surgery with respect to anesthetic choice, blood conservation, and monitoring. There is no ideal technique with respect to each of these choices. This study was designed to determine the usual practice for members of the Society of Neurosurgical Anesthesia and Critical Care (SNACC), with regard to the use of anesthetic technique, the type of monitoring used (and the person responsible for its application and interpretation), and the blood conservation strategies most often utilized for the management of patients undergoing spinal surgery. A total of 415 questionnaires were mailed to all current members of the SNACC. Of these, 85 (23%) were completed and returned. The majority of the respondents administer general anesthesia for lumbar laminectomy. Somatosensory evoked potential (SSEP) monitoring is available at most of the institutions (94%) but only utilized in 75% of patients undergoing a Harrington rod placement. Motor evoked potential monitoring is available at 50% of the institutions, but utilized 25% of the time for these surgeries. The two most frequent blood conservation strategies utilized are intraoperative salvage and autologous donation. The most frequent monitoring utilized for major spinal surgeries is SSEP. Autologous donation and intraoperative salvage are the most frequent blood conservation methods utilized.

Pulmonary embolism after major spinal deformity corrective surgery in adults

Purpose of study: To determine the incidence of pulmonary embolism (PE) and contributing factors after major spinal deformity corrective surgery in adults. Although pulmonary emboli are known to occur after spinal surgery, there are limited published data on the incidence of PE and its contributing factors following major spinal corrective surgery. Incidence of PE in this patient population has been reported to be as high as 3% to 17%. We report our experience in 417 patients.Methods used: From 1992 to 1999, 417 patients (347 women, 70 men) aged 20 to 87 years, (average, 51 years) underwent spinal deformity corrective surgery (146 primary, 271 revision). Surgical approaches include 23 anterior, 155 posterior, 167 same-day combined and 72 staged combined. All surgeries were performed by the senior author (JPK). Average intraoperative blood loss was 3,100 cc. Comorbidity risk was assessed by ASA score (1, 28; 2, 233; 3, 143; 4, 3; average 2.3). Fusion levels varied as follows: <5, 108; 5 to 10, 192; >10, 107. Prophylaxis included TEDS/SCDS, coumadin, heparin, and low molecular weight heparin. We retrospectively reviewed the patients who had pulmonary emboli on our service and identified possible contributory factors.of findings: the incidence of PE was 2.6% (11 of 417; 2 men, 9 women; aged 26 to 64 years, average, 50 years). Diagnosis by spiral computed tomography or V/Q scan occurred on average on postoperative day 4.4 (range, 1 to 13). Two had prior histories of PE/DVT. Eighty percent were diagnosed on or before post operative day 4. Average INR (2.8) and PTT (3) were elevated at time of diagnosis. Average intraoperative blood loss was 2,700 cc (1,000 to 5,000). Average number of levels was 8.6 (4 to 14). Of the 11, 5 were anterior approaches, 5 were posterior alone and 4 were combined; 7 were revisions. ASA scores averaged 2.6 (range, 2 to 3). Of the 11, 3 died (27%).Relationship between findings and existing knowledge: This is the largest known database of complications to date.Overall significance of findings: the incidence of PE after major spinal corrective surgery in adults is significant. Sex, age, blood loss and revision status were not factors affecting mortality. The majority of PEs were diagnosed early and occurred despite therapeutic laboratory values. The high incidence of mortality in this patient population makes it imperative to further investigate PE in this patient population.Disclosures: No disclosures.Conflict of interest: No conflicts.

Mortality after major spinal deformity corrective surgery in adults

Purpose of study: To determine the incidence of mortality after major spinal deformity corrective surgery in adults and factors that may contribute to postoperative mortality. Incidence of mortality after major spinal deformity corrective surgery has reportedly ranged form 1.4% to 20%. Few studies assess mortality in a large series. We report our experience in 417 patients.Methods used: From 1992 to 1999, 417 patients (347 women, 70 men) aged 20 to 87 years (average, 51 years) underwent spinal deformity corrective surgery (146 primary, 271 revision). Surgical approaches include 23 anterior, 155 posterior, 167 same-day combined and 72 staged combined. Average intraoperative blood loss was 3,100 cc. Comorbidity risk was assessed by ASA score (1, 28; 2, 233; 3, 143; 4, 3; average 2.3). Fusion levels varied as follows: <5, 108; 5–10 192; >10, 107. We retrospectively reviewed the patients who died on our service and identified factors that may have contributed to their demise.of findings: The incidence of mortality was 2.4% (10 of 417; 2 men, 8 women; aged 35 to 70 years, average, 52 years). One death was intraoperative. Death occurred on average on postoperative day 9. Average intraoperative blood loss was 3,699 cc (1,300 to 9,000). Average number of levels was 10.1 (5 to 15). Of the 10, 2 were anterior approaches, 5 were posterior alone and 3 were combined; 5 were revisions. Pedicle subtraction osteotomies were performed in six of eight posterior approaches. ASA scores averaged 3 (range, 2 to 4; 4, 2; 3, 5; 2, 2; 1, 0). Causes of death included pulmonary embolus (3), myocardial infarction, shock, abdominal hemorrhage, seizures, multisystem organ failure, cerebral edema/brain death and ARDS.Relationship between findings and existing knowledge: This is the largest known database of complications to date.Overall significance of findings: The incidence of mortality after major spinal corrective surgery in adults is significant. Sex, age, blood loss and revision status were not factors affecting mortality. Patients who died tended to have higher ASA scores/comorbidities (3 vs. 2.3) and were more likely to have had osteotomies. The high incidence of pulmonary embolus as cause of death makes it imperative to further investigate PE in this patient population.Disclosures: No disclosures.Conflict of interest: No conflicts.

Does the Bispectral IndexTM (BISTM) Result in Decreased Drug Use and Faster Recovery in Patients Undergoing Major Spine Surgery Requiring SSEPs?

Does the Bispectral IndexTM (BISTM) Result in Decreased Drug Use and Faster Recovery in Patients Undergoing Major Spine Surgery Requiring SSEPs?

Early Postoperative Respiratory Acidosis After Large Intravascular Volume Infusion of Lactated Ringer’s Solution During Major Spine Surgery

Early Postoperative Respiratory Acidosis After Large Intravascular Volume Infusion of Lactated Ringer’s Solution During Major Spine Surgery

The Accuracy of Coagulation Testing

In Response: We would like to thank Drs. Cooper and McLeod for their thoughtful letter. Although allocation of groups based on recorded surgical impressions of bleeding could lead to unrepresentative data sampling, observation of the surgical field is the first and most important determinant of the need for transfusion of non-red blood cell products (1). When increased surgical bleeding, defined as recurrent bleeding despite adequate use of electrocautery and suture or decreased clot formation within the field is noted, coagulation tests are performed to confirm the existence of a coagulopathy and to determine which non-red blood cell products are needed to correct the disorder. Conversely, routine assessment of coagulation studies in the absence of a clinical clotting abnormality would have limited usefulness. This later point also explains why only 5% of patients in the group without increased bleeding had coagulation tests performed. We agree that prospective studies are needed to further define the mechanisms of coagulopathy and the role of coagulation testing during major spine surgery. Our retrospective analysis provides direction on which coagulation tests may be most useful in the development of evidence-based guidelines for blood component therapy. Terese T. Horlocker, MD Gregory A. Nuttall, MD

Cardiac arrest during surgery and ventilation in the prone position: a case report and systematic review

We present a case report of successful resuscitation following cardiac arrest in a patient undergoing surgery in the prone position. A systematic review of the literature identified 22 further cases. Risk factors for intra-operative cardiac arrest in patients in the prone position include: cardiac abnormalities in patients undergoing major spinal surgery, hypovolaemia, air embolism, wound irrigation with hydrogen peroxide, poor positioning and occluded venous return. Cardiac arrest is also a risk in the increasing number of patients with acute respiratory distress syndrome ventilated in the prone position. Management of prone cardiac arrest may be improved by identification of high-risk patients, careful patient positioning, use of invasive monitoring and placement of self-adhesive defibrillator paddles. Suitable techniques for cardiopulmonary resuscitation including methods for chest compression, defibrillation and the management of air embolism are discussed.