Article Figures & Data
Figures
- Figure 1
Shown are examples of postoperative scans and videoendoscopic views of patients with incidental durotomy and neurological complications following gravity-irrigated interlaminar full-endoscopic spinal endoscopy. The left column shows a postoperative sagittal and an axial magnetic resonance imaging of the cervical spine of a 52-y-old female patient demonstrating hemorrhage spreading anteriorly and laterally distant from the posterior decompression site. The head computed tomography (CT) revealed massive blood in the subarachnoid space and the basal cisterns, the III, IV, and lateral ventricles, and ventricular dilatation consistent with hydrocephalus and arterial subarachnoid Fisher grade IV hemorrhage. However, the CT angiography of the head via femoral catheterization did not reveal any bleeding from possible vascular malformation such as an aneurysm or angioma or any source suggesting that the blood traveled with the irrigation fluid rostrally and intracranially. The center column shows head CT images of ar male patient who underwent lumbar L4-L5 interlaminar gravity-irrigated full-endoscopic decompression surgery with an incidental lumbar durotomy. This patient developed intraoperative seizures, cardiac arrhythmia, and hypotension. His head CT showed intracranial air entrapment. Both illustrated patients were medically stabilized and discharged from the hospital 10 and 3 days postoperatively, respectively. Images in the right column show an exemplary incidental lumbar durotomy that was recognized in the second patient. Consistent with the observed pressure gradients, injury to an epidural vein typically may not cause much bleeding compared with bleeding from an injured arterial vessel.
- Figure 2
The hydrostatic pressure of a static fluid column varies with the height of the liquid column (h), the viscosity or density (d) of the fluid, and the force of gravity (g). It does not depend on area (A) or the shape of the liquid column. For the intraoperative hydrostatic pressure measurements during full-endoscopic lumbar spinal surgery, 2 L bags of physiological saline were hung 2.30 m above the patient and 3.50 m above the floor, considering the height of the operating table of 1.20 m. The fluid bags were connected with flexible tubing via a 2-way connector to the endoscope (Panoview Plus 25°, length 165 mm, working channel Ø 4.1 mm Richard-Wolf Vertebris). The Baxter transducer assembly was registered at the height of the physiological saline bags at 3.50 m. An irrigation pump was not used to ensure that the hydrostatic pressure column remained constant throughout the intraoperative epidural hydrostatic pressure measurements.
- Figure 3
The difference in the hydrostatic pressure measurement between the measurement on the back of the patient (103 mm Hg) and the average epidural pressure measured of 24.5 mm Hg is due to the occurrence of a Venturi effect, which is illustrated in the top panel as a reduction in fluid pressure that results when a fluid flows through a constricted section (or choke) of a pipe (top panel). In a typical gravity-assisted tubing set-up for spinal endoscopy, this occurs as the fluid runs from the back through the tubing system into the narrow irrigation channel of the spinal endoscope and then into the epidural space and from there runs out through the larger working channel of the endoscope (Ø 4.1 mm). Considering the choked flow in an open system gravity-assisted irrigation setup during spinal endoscopy, various diameter changes occur as the fluid runs through it, and the fluid velocity approaches the local speed of sound. When a liquid system is in a state of choked flow, a further decrease in the downstream pressure environment will not increase velocity unless the fluid is compressed. Our measurements revealed an average drop of 78.5 mm Hg from the initial hydrostatic pressure of 103 mm Hg at the patient level before entering the spinal endoscope down to 24,5 mm Hg in the epidural space. The average epidural hydrostatic pressure of 24.5 mm Hg was higher than the reported intradural cerebrospinal fluid (CSF) or intravenous pressures (bottom panel).
- Figure 4
Seven hundred sixty-six spine surgeons accessed the online survey. Forty-four submitted a valid survey recording in English at the completion rate 43.1% (A—top panel). Two hundred submitted a valid survey recording at a completion rate of 44.0% (B—bottom panel).
Tables
- Table 1
Hydrostatic epidural pressure measurements in patients who underwent routine L4-L5 and L5-S1 interlaminar full-endoscopic discectomy.
Patient Gender Age, y Weight, kg Measured Hydrostatic Pressure, mm Hg 1 M 54 82 26.5 2 M 62 71 20.0 3 F 46 131 22.5 4 M 65 92 26.0 5 M 72 86 23.0 6 F 58 61 29.0 7 F 51 65 20.0 8 F 46 90 28.0 9 M 39 78 23.5 10 M 40 89 21.0 11 M 36 70 29.0 12 M 52 62 25.5 Abbreviations: F, female; M, male.
Question n % Cumulative % What is your postgraduate training background? Missing response 1 0.4 .4 Not applicable 2 0.8 1.2 Neurosurgeon 16 6.6 7.8 Orthopedic surgeon 211 86.5 94.3 Pain management 14 5.7 100.0 Total 244 100.0 What percentage of your practice is endoscopic spine surgery? 0% 3 1.2 1.2 1%–5% 26 10.7 11.9 5%–20% 61 25.9 70.5 21%–40% 59 24.2 36.1 41%–60% 23 9.4 45.5 61%–80% 34 13.9 84.4 81%–100% 38 15.6 100.0 Total 244 100.0 What is your practice setting? Employed by large physician group 5 2.0 2.0 Hospital employed 187 76.6 78.7 Private practice 30 12.3 91.0 Private practice with academic appointment 12 4.9 95.9 University employed 10 4.1 100.0 Total 244 100.0 Question n % Cumulative % Years performing spinal endoscopy 0 3 1.2 1.2 1–4 50 20.5 21.7 5 53 21.8 43.5 6 23 9.4 52.9 7 20 8.2 61.1 8 25 10.2 71.3 9 9 3.7 75.0 10–32 y 60.0 25.0 100.0 Total 244 100.0 Country Missing response 6 2.5 2.5 Angola 1 0.4 2.9 Brazil 19 7.8 10.7 Canada 1 0.4 11.1 Chile 2 0.8 11.9 China 191 78.3 90.2 Colombia 3 1.2 91.4 Croatia 1 0.4 91.8 Ecuador 1 0.4 92.2 Germany 5 2.0 94.3 Mexico 6 2.5 96.7 South Korea 1 0.4 97.1 Thailand 3 1.2 98.4 United Kingdom 1 0.4 98.8 United States 3 1.2 100.0 Total 244 100.0 - Table 4
Adverse events and complications related to irrigation during lumbar spinal endoscopy reported by responding spine surgeons.
Adverse Events or Complications n % Cumulative % None 172 70.5 70.5 Headaches and seizures Headache 11 4.5 75 Headache and seizure 2 0.8 75.8 Headache and seizure, and abdominal pain 1 0.4 76.2 Headache and seizure, nerve root injury 1 0.4 76.6 Headache, neck pain 3 1.2 77.8 Neck pain and seizures Neck pain 12 5 82.8 Neck pain and seizure 1 0.4 83.2 Neck pain and seizure, soft tissue edema 1 0.4 83.6 Neck pain and stiffness 1 0.4 84 Neck pain, delirium 1 0.4 84.4 Nerve damage and neurological deficit Nerve root injury 3 1.2 85.6 Nerve root injury, infection 1 0.4 86 Nerve root injury, seizure 1 0.4 86.4 Dural edema 1 0.4 86.8 Numbness in lower extremities 2 0.8 87.6 Durotomy 5 2 89.6 Cauda equina syndrome 1 0.4 90 Autonomic dysreflexia with hypertension Autonomic dysreflexia with hypertension 17 7.2 97.2 Durotomy, headache, and autonomic dysreflexia with hypertension 1 0.4 97.6 Paralysis, autonomic dysreflexia with hypertension 1 0.4 98 Other adverse events Prolonged wakeup from general anesthesia 1 0.4 98.4 Prolonged postoperative recovery due to hypovolemia 17 0.4 98.8 Soft tissue edema 2 0.8 99.6 Epidural hematoma 1 0.4 100 Missing response 1 0.4 100.4 Total 244 100.0 a The cumulative total exceeds 100 due to rounding.
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