| Ultrasound Innovation Award |
| Online Abstract Submission |
| (Author: Malcolm Watson ) |
| Abstract |
| Type: New equipment design |
| Title: The development, fabrication and clinical evaluation of a novel ultrasound probe to guide the insertion of central neuraxial anesthesia and analgesia in obese women for elective section |
| Disclosure Statements |
| My research & development of my invention is supported by a commercial company |
| Abstract |
| We hypothesized that ultrasound guidance of central neuraxial anesthesia would allow the rapid, safe and effective administration of central neuraxial anesthesia and analgesia in morbidly obese parturients. The prevalence of obesity in the UK is increasing; 24% of all adult females are now defined as clinically obese and obesity is linked to more than half of all maternal deaths in the UK audit of maternal mortality1. Co morbid obesity often results in multiple attempted needle insertions and a delay in operative delivery or the provision of analgesia which is traumatic for the parturient and potentially detrimental to the neonate. Central neuraxial anesthesia represents the ‘gold standard’ for all parturients requiring operative or assisted delivery or analgesia during labor and provides a low risk alternative general anesthesia. Palpation of the boney landmarks to guide insertion of epidural and spinal anesthesia is the current clinical standard but it has been shown to be inaccurate in 71%2 and 63.6%3 of cases. We felt that the available ultrasound technology did not readily facilitate ultrasound guided neuraxial anesthesia. The aims of this project were to design, fabricate to good manufacturing practice, safety test (to achieve MHRA device approval) and clinically trial a novel ultrasound probe in obese parturients. The primary end point of the trial was the time taken to site a combined spinal epidural needle in obese parturients with a median BMI of 42. In order to design and build a novel ultrasound probe to guide insertion of spinal and epidural needles the key steps were: (i) Determination of the optimal acoustic configuration (ii) Changing the mechanical design of a traditional ultrasound probe to assist with acceptance and use by obstetric anesthetists and adapting the probe to withstand use within the labor wards and operating room environment. (iii) The inclusion of a channel and epidural needle guide into the ultrasound transducer array (iv) Comparative image testing to ensure that lumbar spine imaging of the novel ultrasound probe was at least comparable with available ultrasound technology. The final challenge was a clinical trial of the split array probe to evaluate the administration of combined spinal epidural anesthesia in obese parturients scheduled for elective section. We recruited 42 (trial powered for 46 patients) obese parturient to the clinical trial during 24 months. The results of the clinical trial indicate that the learning curve was longer (16 patients) than envisaged but that it is significantly shorter than the generally accepted learning curve for traditional epidural administration in normal parturient guided by feeling the bones (>100 patients)4 and short axis ultrasound guided needle techniques using traditional ultrasound probes(104 patients)5 . The UK medical devices regulations6 prohibit the use of the new device outside a clinical trial and therefore prevent a user from gaining experience in the new procedures associated with any novel device. The operator used in the clinical trial was very experienced (>2000 procedures) in using palpation to guide the insertion of central neuraxial anesthesia and despite having no previous experience of ultrasound outside the clinical trial, after only 16 procedures a trend towards decreased time taken to administer combined spinal epidural anesthesia was observed. References: 1 Lewis, G (ed) 2007. The Confidential Enquiry into Maternal and Child Health (CEMACH). Saving Mothers’ Lives: reviewing maternal deaths to make motherhood safer - 2003-2005. The Seventh Report on Confidential Enquiries into Maternal Deaths in the United Kingdom. London: CEMACH. 2 Broadbent C.R., Maxwell WB, Ferrie R, Wilson DJ, Gawne-Cain M, Russell R. Ability of anesthetists to identify a marked lumber interspace. Anaesthesia 2000; 55:1122-1126 3 Schlotterbeck H., Schaeffer R., Dow W.A., Touret Y., Bailey S., and Diemunsch P. Ultrasonographic control of puncture level for lumbar neuraxial block in obstetric anesthesia. British Journal of Anaesthesia 2008;100(2): 230-4. 4 Filho G. R. d. O., Helayel P. E., , Conceição D. B. d., Garzel I. S., Pavei P., and Ceccon M. S., Learning Curves and Mathematical Models for Interventional Ultrasound Basic Skills. Anesthesia and Analgesia 2008; 106:568-573 5 Kestin I.G., A statistical approach to measuring the competence of trainees at practical procedures. British journal of Anaesthesia 1995;75:805-809 6 The Medical Devices Regulations 2002, ISBN 0 11 042317 8 7 www.nice.org.uk/ip403overview |
| Clinical Significance |
| The technology developed in this project may provide clinicians with a simple method of using ultrasound imaging to quickly and accurately site central neuraxial anesthesia in technically difficult patients in accordance with NICE guideline 249. Nice issued guideline 249 in January 2008: ‘Evidence on ultrasound-guided catheterization of the epidural space is limited in amount, but suggests that it is safe and may be helpful in achieving correct placement.’ 7 The use of ultrasound to guide the insertion of epidural or spinal anesthesia should be considered in all obese pregnant women as this work has indicated that ultrasound technology has the potential to: 1. reduce the time taken to provide anesthesia for operative delivery of the fetus. 2. increase patient safety due to reduction in the use of general anesthesia 3. improve neonatal outcomes due to rapid provision of safe, accurate central neuraxial anesthesia to allow the delivery of any fetus showing signs of distress. 4. increased maternal satisfaction due to a reduction in the time and number of attempts taken to provide analgesia or regional anesthesia during child birth |
| Ultrasound Equipment |
| Manufacturer: not applicable |
| Model: not applicable |
| Probe Used |
| Type: linear array |
| Size: 8cm in length |
| Frequency: broadband median frequency 3.75Mz |
| Files |
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1. Filename: split array.bmp 2. Filename: split array with sheath and clip.JPG
3. Filename: clips.JPG
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