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OBESITY-AN IMPORTANT NEUROSURGICAL COMORBIDITY FOR COMPLEX REASONS.21 September at 11:47 from atlas
Obesity - influence on spinal degeneration and surgical outcome
The WHO definition of overweight status is a Body Mass Index(BMI) of 25-30 kg/sqm and obesity status as BMI above 30 kg/sq m.The WHO further defines 3 Classes of obesity. Class I : BMI 30 - 34.9 : mild: moderate increased morbidity& mortality; Class II : BMI 35- 39.9 :moderate: severe increase in morbidity & mortality ; Class III : BMI 40 :severe(or morbid) ; very severe increase morbidity&mortality.In the 1960's discussions related to weights above 'ideal' body weight.Payne described severe (or morbid) obesity, as body weight 45 ,or more kg above ideal body weight.Nowadays, BMI (and other measures such as abdominal girth) are accepted as verifiable & objective indices of weight status.
Studies have shown a link between obesity and osteoarthritis of the knee & hip joints. Indeed propective studies have shown that the risk of knee OA increases by 15 % for each kg/sq m 27.However, the link between obesity and lumbar degeneration is not so well defined.There is ample evidence of the adverse loading on the spine,particularly the facets in both vertical and ventral planes in obesity.Although obesity is associated with conditions such as meralgia paraesthetica and coccydynia,there is conflicting scientific evidence between obesity and lumbar degeneration / disc herniation.Obesity is not an established cause of low back pain , however, studies have shown increasing vertebral osteophytosis with increasing BMI& obesity.
The link between obesity and poorer general ,and spinal, surgical outcomes however is well established. BMI 30 is associated with a 50 - 100 % increase from premature death of all types.In GI surgery there is a 6.6 % mortality ( normal 2.2 %) and the cause includes not only medical comorbidities linked with obesity, but increased blood loss & operating time,more major complications and positioning/access/exposure issues.
Should elective lumbar spine be performed, or under which circumstance in obesity? Gepstein R et al (Clin Orth Relat Res 2004)found that the obese cases tended to be female, younger & more symptomatic.The authors found that it is reasonable to operate on obese(& elderly) with the appropriate indications.Andreshak et al (J Spin Disord 1997), examined 159 cases of lumbar spine fusion in obesity.Their study found no increased blood loss, complications ,operation duration or outcome change compared with non-obese cases.Conversely. Patel et al ((J Neurosurg Spine 2007) found infection, dural tear,DVT,pneumonia & positioning palsies occurred more frequently in obese spinal surgery.LaCaille et al found complication related treatment costs to double with poorer outcomes as well ( reported by Furukawa et al The Open spine Journal 2010).Garcia et al (J Bone Joint Surg Am 2008) found that lumbar surgical obese patients did not lose weight after surgery ,but at a mean 3 years had increased in weight (by 2.5 kg).
Furukawa et al (2010) reviewed 118 posterolateral lumbar fusions and noted longer operative time,increased operative bleeding, longer distance from skin to posterior vertebral margin, poorer outcome and higher intra- & post-operative complications in severely obese cases (they defined as ).They noted evidence of increased DVT-PE, epidural lipoma as well.They measured depth from skin to posterior vertebral margin (and correlated increased depth (in obesity) measured on preoperative CT or MRI, with poor operative field & operability leading to increased complications such as dural tears, incorrect screw placement & incorrect level surgery.
Edward C Benzel (et al) published the standard text "Spine Surgery:techniques, complications and avoidance" and examines the issue of obesity in spinal surgery.General issues of anaesthetic significance are noted such as impaired gas exchange, CO2 retention (Pickwickian Syndrome) , requirement for 100 ml /min extra cardiac output per EACH extra kg of fat .Diabetes, heart failure, infection, DVT-PE are established risks.
Obesity specifically affects a number of surgical aspects of spinal surgery as well.The surgical approach is affected by the panniculus in terms of incision, retraction, intraoperative imaging etc.Similarly positioning is impacted.In spinal surgery options include prone, supine, lateral decubitus, sitting and kneeling.A standard or Jackson table can be used for the prone approach.The kneeling approach is favoured for obesity as it reduces abdominal (and IVC ) pressure and reduces operative field venous engorgement via Batson's epidural venous plexus and this favourably influences blood loss, dural/nerve injury and improves cardio-respiratory function as well.The detractors to the kneeling position are that it requires an experienced team, is time consuming (1/2 hour +),increases potential for neurovascular contact injury & increases lumbar lordosis making dural exposure more difficult at times.Retractors required include Scoville shoulder type, large Weitlaners, large Harvey-Jacksons and hooks with weights.Attention to eye and face protection is required. The facial dependency associated with this position does increase the risk of eye congestion and visual impairment (temporary or permanent) and cerebral oedema for the same reason.
Difficulties during the actual surgery can occur due to the depth from skin and there is no way of changing this. Lighting, retraction systems and excellent assistance with suction will be beneficial.A good and experienced assistant is required!The amount of bone/facet etc requiring removal is physically demanding.Osteotomes may be called for , but their use at depth increases their danger.Wound closure and haemostasis must be metculous and require experience. identifying the correct level in surgery is difficult in the obese. All the skills of the experienced radiographer may still produce unhelpful intra-operative films (especially in patients 120 kg in my experience).Obese surgical patients have a higher rate of infection, postoperative ooze/bleed and dehiscence. Adipose tissue has a poor blood supply, reduced suture retention strength ( liquifies )and responds poorly to bacterial contamination All the skills of an experienced spinal surgeon are required in obese spinal surgery..positioning, meticulous subperiosteal dissection, avoidance muscle cutting etc are paramount..Experienced patient haemostasis with bipolar coagulation, appropriate bone wax, irrigation and gelfoam/surgicel etc adjuncts is mandatory.. Ensuring normal BP & perhaps an intra-operative Valsalva manoevre to confirm haemostasis pre closing may reduce post-operative bleeding.
Wound closure techniques also require special attention in the obese spine. Minimising dead space with a multi-layered closure, approximating Campers (superficial ) fascia and using appropriately sited (and even multiple) drains will lead to less problems .In the obese the principle of leaving the drain in longer" to do its job"-and not routinely remove as per the pathway, i. e. prevent seromas etc is crucial.Infections and haematomas are difficult to manage in the obese.Antibiotics have poorer penetration. I tend to use 24 hours of cephalosporins in general , and this applies to the obese spine as well.If a dehiscence or infection occurs, then aggressive surgical intervention may be required.Superficial opening, debridement, packing & healing by granulation/ delayed primary closure may all be required depending on the actual case.
Postoperative care is important.Edward Benzel recommends that all obese spinal cases be observed in ICU.Early mobilization, pulmonary toilet, incentive spirometry &chest physio with head of bed elevation are advocated.It should be noted that in the obese complex pulmonary Z zonal AV shunting may occur in an upright position with resultant hypoxia- hence a surgeon requires the assistance of an intensivist, ICU nurse& physio who understand these matters better ! Postoperative Hb (adverse effects on heart& wound healing), BSL, DVT-PE, complexities of analgesia (in a lipophilic body) , CO 2 Pickwickian retention and Obstructive Sleep Apnoea (OSA) are best managed after a complex & often dificult spinal operation in an ICU .
Patient selection is ALWAYS an issue surgeons reflect on -pre & post operatively with great consternation.This is particularly the case in obese spinal surgery.Operating on the spine requires CAREFUL consideration ALWAYS (see my other articles) BUT particularly so in the obese... crucially so in the morbidly obese.Avoiding operation unless there exists an ABSOLUTE spinal surgical indication , such as cauda equina syndrome, malignancy, sepsis (epidural abscess) WILL reduce morbidity& mortality intra and post operatively in these high risk patients.Advising a patient to immediately cease smoking (ALL PATIENTS !) AND that a weight loss of as little as 10-15 kg WILL significantly improve risk, pulmonary function (Benzel) and outcome are the hallmarks of GOOD & EXPERIENCED spinal surgical planning in the obese spinal surgical case, providing the required delay is acceptable neurologically.
Involvement of the patients family doctor, dietitian, GE specialist & early /aggressive endosope gastric balloon or laparoscopic gastric band,with weight loss (& cessation of smoking ofcourse) WILL USUALLY result in LESS major spinal surgical (and anaesthetic) morbidity AND mortality when / if the spinal surgical requirement becomes ABSOLUTE / OR EMERGENT.
Experienced spinal surgeons, anaesthetists, intensivists, OR/Ward&ICU nurses, hospital wardsmen, radiographers,physios& phlebotomists ALL know the complexities & risks associated with obese( particularly morbid) spinal surgery.A good outcome in these cases requires insight, planning, experience, team involvement, patient education and meticulous atttention to detail.