The exploration of ultrasound-assisted modified paramedian technique for spinal anesthesia in elderly

doi:10.21203/rs.3.rs-1512666/v1

Background:At present, there are two techniques which are widely applied clinically,

including midline technique and paramedian technique,both of them are difficultfor residents when faced with elderly.We aim to explore the feasibility of ultrasound-assisted modified paramedian technique for spinal anesthesia in elderly,in order to provide clinicians with a new and easy-to-operate technique.

Methods:A total of 150 elderly patients who were scheduled for urology surgery under spinal anesthesia in our hospital were randomly divided into three groups (n=50) : midline technique group ( group M), paramedian technique group ( group P) and modified paramedian technique group ( group PM) with 50 patients in each group.All spinal anesthesia were performed by the same second-year resident.

Results:Compared with groups M and P , group PM had a significantly higher first-attempt success rate (P<0.05,specially in patients aged 65-74 years)，fewer attempts（P<0.05）and higher patient satisfaction score（P<0.05）. Compared with group M,the time taken to perform spinal anesthesia and the number of needle redirections were significantly reduced in group PM (P<0.05), and there was no statistically significant difference between groups PM and P . There were no statistically significant differences in the cases of inconsistency between ultrasound-assisted and landmark-guided location of intervertebral space, the time taken to ultrasound-assisted location,the onset time to pain block at T₁₀,the incidence of hypotension ,anesthesia effect and the incidence of headache, low back pain, nausea and vomiting within 24 hours after surgery.

Conclusions: The modified paramedian technique in spinal anesthesia for elderly patients can significantly improve the first-attempt success rate, reduce the number of attempts and reduce procedure time and the damage to patients’ tissue during operation. Compared with the traditional midline and paramedian techniques, modified paramedian technique achieves complementary advantages of the others,easy to learn,which effectively solves the difficulty of spinal anesthesia during the procedure in elderly patients and provides a new operation path for lumbar puncture.It is worthy of further research and application.

Trial registration:Prospectively registered at China Clinical Trial Registry, registration number ChiCTR2100047635, date of registration: 21/06/2021.

Spinal anesthesia

modified paramedian technique

Ultrasound-assisted location

Elderly

Urological surgery

In the context of the increasingly prominent trend of population aging, the number of elderly who need surgical treatment under spinal anesthesia is increasing.Even the mean age of the spinal anesthesia cohort for Hip Fracture Repair demonstrated a similar increasing trend over time whereas the mean age of the general anesthesia cohort did not^[1].Studies have shown that the risk of most many urinary system diseases (such as benign prostatic hyperplasia, bladder tumors, urethral stricture, etc. ) increase drastically with ageing,even for patients who have undergone urethroplasty, the decline of detrusor function related to age may cause urinate difficulty again^[2-4].In some cases,compared with general anesthesia, spinal anesthesia has been recognized by the majority of anesthesiologists because of providing greater hemodynamic stability, higher patients' satisfaction, lower rate of opioid use and higher rate of opioid-free recovery and lower maximum PACU pain scores^[5-7].

Due to the degeneration of the lumbar spine (bone hyperplasia, ligament calcification, intervertebral space stenosis, spinous process hyperplasia,etc.) caused by aging,spinal anesthesia in elderly patients might be difficult^[8], especially for inexperienced residents .As we all know,there are two traditional techniques for spinal anesthesia(midline technique and paramedian technique), each of which has advantages and disadvantages in terms of operation and application.As a visible technology, ultrasound can be applied safely to spinal anesthesia of elderly patients, but the effect is far from perfect. Park et al.^[9] showed that preprocedural ultrasound can improve the first success rate of spinal anesthesia in elderly patients from 17.5% to 65%.While Rizk et al.^[10] found that a preprocedural US scan did not improve the ease of midline and paramedian for spinal anesthesia in elderly as compared to the conventional landmark technique when performed by junior residents . So how to concentrate the advantages of two traditional methods, improve the success rate of spinal anesthesia , reduce the time taken to puncture and the number of attempts, and facilitate the process of anesthesia in elderly patients is still a clinical problem that needs to be explored.

We hypothesized that ultrasound-assisted modified paramedian technique for spinal anesthesia may concentrate the advantages of both,and result in a preferable effect. So we carried on the prospective, randomized, controlled study in our hospital.

This study was approved by the Ethics Committee of the Second Hospital of Lanzhou University (2021A-106) and registered on 21/06/2021, at the China Clinical Trial Registration Center (http://www.chictr.org.cn/) (registration number: ChiCTR2100047635). Patients with planned for urological surgery under spinal anesthesia were consecutively enrolled at the Second Hospital of Lanzhou University, China, from April 2021 to September 2021. Inclusion criteria were as follows: age≥65 years old; American Society of Anesthesiologists physical status I to III.Patients were excluded if they: refused participation, had contraindications to spinal anesthesia (uncertain neurological disorders,local infections, allergic to local anesthesia, coagulopathy),had spinal deformities, had a history of spinal surgery , were difficulty for tolerating ultrasound scanning or having a communication.

The patients were randomly(using a computer generated randomized number table)allocated into three groups according to different techniques after ultrasound-assisted location: group M, group P and group PM by a doctor who didn’t take part in the study.The related information was placed in an opaque envelope,which was numbered 1-150 according to the order the patient was included, so that the envelopes correspond to the patients one by one.Considering the feasibility of the study,only patients were blinded to the group.

After the patient entered the operating room, invasive or non-invasive blood pressure,pulse oximetry and three-lead electrocardiography were routinely monitored. Meanwhile making sure peripheral venous assess was established.All patients were placed in a standard lateral recumbent position with inhaling face mask oxygen at a flow rate of 2-3L/min.At first, a resident (the physician was also responsible for performing anesthesia throughout the study) palpated the surface anatomical landmarks with the conditional identification(the intersection between the highest point of the iliac crest and the spine is regarded as the L3-4 spinous process space or the L4 spinous process ),and then marked the the site of needle insertion on the surface of the patient’s skin.Next, another senior anesthesiologist who was proficient in the use of ultrasound performed ultrasound-assisted location throughout the study.The Sonosite with a low frequency (2 to 5 MHz) curved array probe and a depth of 9.2cm was applied. The probe was placed at parasagittal oblique (PSO) plane, 1–2 cm to the midline.As we can see from the screen,the sacrum is a continuous bright line of high echo. Then moving the probe upwards from the sacrum,the structure of articular process with a “hump sign” could be seen. When L_3-4 intervertebral space was identified, the probe was slightly tilted until an optimal image of anterior/posterior complex appeared (the anterior complex is the imaging of vertebral body and posterior longitudinal ligament, and the posterior complex is the imaging of ligamentum flavum and dural sac).Shifting the image to the center of the screen, a line which was perpendicular to the midpoint of the long axis of probe was drawn on the surface of the patient's skin with the guidance of M-line.The line was regarded as L_3-4 intervertebral space.Next, the probe was rotated 90° at transverse midline (TM) plane,scanning from cephalic to caudal in the space to determine adjacent spinous processes.The spinous processes, articular processes, anterior and posterior complexes could be visible by adjust the probe slightly. The two points corresponding to the spinous processes were marked on the surface of the skin. The line connecting the points was regarded as posterior midline of spine.Last,the intersection of two connecting lines was identified as the needle insertion point “O” of group M.For group P,the injection site was 1.5cm lateral to the“O”on the right of the midline,and the needle was punctured from the skin at an angel of about 75°.while for group PM,the site was 0.5cm lateral to the“O”on the right of the midline.For both of groups M and PM,the needle was perpendicular to skin.

When the site was identified,all the lines were erased.The resident was supervised to perform strictly an aseptic technique throughout the process.A 22-gage Quincke spinal needle was used to puncture. After making sure the cerebrospinal fluid flowed out smoothly,15mg of 0.75% ropivacaine was injected into subarachnoid space with the slope of needle cephalad at a speed of about 0.2ml/s.After the injection was completed, the patient was placed supine at once.The level of sensory block was adjusted up to T_10-8.During the surgery, the patient's blood pressure was administed within range of±20% of the baseline. The number of attempts> 3 times,the number of needle redirections >10, the replacement of puncturing gap, anesthesiologist and technique of spinal anesthesia or the change of anesthesia method would be recorded as a failure,and the trial was stopped.

Data collection

The primary outcome was the first -attempt success rate . The secondary outcomes were the number of attempts (each time when the needle was returned to the subcutaneous to readjust the direction of the needle to puncture again or the needle leaved the skin to puncture again was considered another separate attempt), the number of needle redirections,the cases of inconsistency between ultrasound-assisted and landmark-guided location of intervertebral space,the time taken to perform spinal anesthesia (the time from the needle puncturing into the skin after local anesthesia to free flow of cerebrospinal fluid), patient satisfaction (1-5 points), the time taken to ultrasound-assisted location, the onset time to pain block at T₁₀, the effect of anesthesia, the incidence of headache, back pain, nausea and vomiting within 24 hours after the operation.All the data was collected by an anesthesiologist who didn’t take part in the administration of patients.

Statistical Analysis

The sample size was counted by PASS15 software(NCSS,America).In our hospital,the first -attempt success rate in elderly with midline technique was 53.6%,and with side-straight technique was 79.3%.According to a previous study^[10],the first -attempt success rate in elderly with paramedian technique for resident was 42.0%.With anαerror of 5%, a β error of 10% (90% power) and dropouts of 10%, a sample size of 50 patients per group was required.

Statistical analysis was performed using SPSS Version 25 (IBM, Armonk, NY). The measurement data were tested for normality at first.Normally distributed data were presented as mean±standard deviation (`x±s), and the comparison between groups was performed by ANOVA test.The non-normally distributed data were described as the Median (M) and Interquartile range (IQR) and were compared between groups using Kruskal and Wallis test.Counting data were presented as numbers and percentage (n,%) and analyzed by Chi square or Fisher’s exact test.P<0.05 is considered statistically significance.

A total of 150 patients were initially enrolled in the study, of which six cases(four in group M,one in groups P and PM ) were excluded due to failure during puncturing .No one was turned into general anesthesia.There were no dropout in our study, and the remaining 144 cases were finally included in analysis. There were no statistically significant differences in age, height, weight, BMI,time of surgery, gender, American Society of Anesthesiologists classification or type of surgery among the three groups of patients (Table 1).

Table 1

Comparisons of characteristic of the three groups

	Group M（n=46）	Group P (n=49)	Group PM (n=49)	P
Age（y）	72.33±7.02	71.49±6.53	72.10±5.53	0.802
Height（cm）	168.78±5.49	169.94±6.64	168.35±5.25	0.380
Weight（kg）	64.15±9.49	65.24±10.30	66.51±10.89	0.534
BMI（kg·m^-2）	22.51±3.08	22.55±3.03	23.42±3.28	0.276
Time of surgery（min）	97.15±47.25	82.12±36.81	98.33±42.93	0.114
Gender M F	46(100) 0(0)	47(95.9) 2(4.1)	46(93.9) 3(6.1)	0.371
ASA I II III	3（6.5） 36（78.3） 7（15.2）	2（4.1） 42（85.7） 5 （10.2）	3（6.1） 42（85.7） 4 （8.2）	0.805
Type of surgery TURP TULIP Ultrasound-guided prostate biopsy Others	21（45.7） 7（15.2） 7（15.2） 11（23.9）	21（42.9） 8（16.3） 10（20.4） 10（20.4）	28（57.1） 8（16.3） 5（10.2） 8（16.3）	0.741
Values are given as mean ± SD or numbers (%) Abbreviations: TURP,Transurethral Resection of Prostate;TULIP,Transurethral Ultrasound-guided Laser Induced Prostatectomy ;SD, standard deviation.

There were no statistically significant differences in the data related to ultrasound-assisted location (Table 2).

Table 2

Comparisons of data related to ultrasound scanning of the three groups

Group M（n=46）

Group P(n=49)

Group PM (n=49)

P

Cases of inconsistency between ultrasound-assisted and landmark-guided location of intervertebral space

Time taken to ultrasound-assisted location

14（30.4）

139.57±31.18

12（24.5）

144.22±36.54

8（16.3）

144.43±33.50

0.266

0.734

Values are given as mean ± SD or numbers (%)

The first-attempt success rate of the three groups was 47.8%, 42.9%, and 77.6%. which was significantly higher in group PM than groups M (P<0.05) and P (P<0.001); the number of attempts in group PM (1[1-1] ) was significantly fewer than groups M (2[1-2]) and P (2[1-2]), P<0.05; The time taken to perform spinal anesthesia in group PM was significantly shorter than group M (P<0.05), but was not different from group P ; The number of needle redirections in group PM (1[0-2]) was significantly fewer than group M (2[1-3.25], P<0.05),but compared with group P (1[1-2]) ,the difference was not statistically significant; In terms of patient satisfaction score during the process of puncturing, group PM (4[4-5]) was respectively higher than groups M (4[3-4], P<0.05) and P (4[3.5 -4], P<0.05). Compared with group M, the time taken to perform spinal anesthesia in group P was significantly reduced (P<0.05), and the other related data during puncturing was showed no statistical significance.There was no statistically significant difference in the onset time to pain block at T₁₀ among the three groups (Table 3).

Table 3

comparisons of data during anesthesia process of the three groups

	Group M（n=46）	Group P (n=49)	Group PM (n=49)	P
First-attempt success rate	22(47.8)	21(42.9)	38(77.6)^ab	0.001
Number of attempts	2[1-2]	2[1-2]	1[1-1]^ab	0.003
Number of needle redirections	2[1-3.25]	1[1-2]	1[0-2]^a	0.003
Time taken to perform spinal anesthesia	116.00[49.75-244.00]	68.00[44.50-129.50]^c	56.00[36.50-106.00]^a	0.001
Satisfaction scores	4[3-4]	4[3.5-4]	4[4-5]^ab	0.001
The onset time to pain block at T₁₀(s)	146.33±26.63	145.08±23.08	146.67±24.35	0.945
Values are given as mean ± SD, median (IQR), or numbers (%). ^a Group PM vs Group M; ^bGroup PM vs Group P; ^cGroup P vs Group M

To explore the influence of age on puncturing related outcome , subgroup analysis was conducted among patients according to different ages. All patients were divided into two groups: 65-74 years old and more than or equal to 75 years old. The results showed that there were no statistical significance in the composition ratio of patients in three groups (P>0.05). For patients aged 65-74 years, the first-attempt success rate in group PM was significantly higher than groups M and P (P<0.05). Compared with group M, the number of needle redirections in group PM was significantly reduced (P<0.05), and the difference was not statistically significant when compared with group P . The number of attempts in group PM was significantly fewer than group P (P<0.05), and the difference was not statistically significant compared with group M. There was no significant difference in satisfaction score among three groups (P>0.05). For patients more than or equal to 75 years old, there were no significant difference in the first-attempt success rate, the number of attempts and the number of needle redirections among three groups,But the patient satisfaction score in group PM was significantly higher than groups M and P. For patients of both ages,the time taken to perform spinal anesthesia in group PM was significantly shorter than groups M (P<0.05), but there was no statistically significant difference when compared with group P (Table 4).

Table 4

Comparison of related data during puncturing in different ages among the three groups

There were no statistically significant differences in the effect of anesthesia and the incidence of nausea or vomiting, headache, and low back pain within 24 hours after surgery among the three groups.(Table 5)

Table 5

Comparisons of the effects of anesthesia and postoperative adverse reactions within 24 hours after surgery among the three groups

Studies have shown that the height and width of the lumbar spinous process increased in elderly when compared with young people, and various anatomical parameters were in dynamic change with advancing age.In addition, the thickening of collagen fiber components of ligaments, cartilage metaplasia and calcification,even the formation of local interspinous ossification further resulted in the irregular shape of the spinous process and the narrowing of spinous process space in elderly patients.On the other hand, the function of extension and bending of spine was restricted because of degenerative changes of spine^[11-13]. In summary, the difficulty of landmark-guided location caused by spinal degeneration may be a major reason for the low success rate of spinal anesthesia in elderly patients. Ultrasound has been successfully applied in spinal anesthesia for elderly with its’ advantages on non-invasiveness, non-radioactivity and low cost. Many studies have shown that preprocedural ultrasound technique could improve the accuracy of localization and the first-attempt success rate of lumbar puncturing as well as reduce the number of attempts in elderly patients^[9,14,15,16]. Therefore, in order to improve the accuracy of location and reduce the effect of anatomical factors on results, we performed ultrasound-assisted location in all patients before anesthesia.As we can see,The difference between ultrasound-guided and landmark-guided location of intervertebral space was 30.4%, 24.5% and 16.3% in each group .

At present, midline technique and paramedian technique are widely applied for spinal anesthesia in elderly. The former is easy for residents to perform, but the needle tip is often stopped by bones and ligaments which results in a low success rate. The latter can bypass supraspinous ligament and interspinous ligament.But for residents, it is often difficult to grasp the optimal angel and depth to puncture. Previous studies have shown that two traditional approaches have their own advantages and disadvantages in clinical application, and there was a difference between resident physicians and senior physicians^[10,17,18], which may be related to operators’ experience. Therefore, we set up a resident as anesthesia operator throughout the study.The results showed that the first-attempt success rate in elderly patients of groups M and P were 47.8% and 42.9%. There were no significant difference in first-attempt success rate, number of needle redirections,number of attempts,patient satisfaction and the incidence of postoperative adverse reactions,only the time taken to perform spinal anesthesia in group M was longer than group P. Rizk et al.^[10] showed that under the premise of ultrasound-assisted localization and resident responsible for operation,compared with paramedian technique group, midline technique group has significantly a higher first-attempt success rate (73% VS 42%) ,fewer number of needle redirections and number of attempts and less puncturing time,which was different from the results of our study. This may lie in the different definitions of the first-attempt success rate and practical abilities of operators in the two studies.

As mentioned above, the trade-off between two traditional techniques sometimes fails to achieve satisfactory results. Therefore,it may be easier to look for a new technique to solve the clinical problem .For nearly ten years of clinical practice, we have found that even in the case of repeated failure for senior anesthesiologists to perform spinal anesthesia in elderly patients with midline technique and paramedian technique, the application of modified paramedian technique often gets success. What’s more,compared with midline technique,operators often feel a significant reduction in resistance in the process of needle insertion, especially in elderly patients. The reason may lie in that modified paramedian technique bypasses calcified supraspinal and interspinous ligament or the dense and tough part of ligaments of elderly patients which reduces the difficulty of puncturing. At the same time, it is especially suitable for residents with less experience. Because the insertion angle and depth of needle are easy to master.By reviewing previous literature^[19-21], for modified paramedian, the needle tip can reach subarachnoid space smoothly theoretically by setting 0.5 cm lateral to the midpoint of L3-4 spinous process space as injection site with the needle perpendicular to skin.A study showed that compared with median sagittal and transverse images, ultrasound scanning in para-midsagittal position could obtain a larger intervertebral space and a clearer field of ligamentum flavum and epidural vessels, thus improving the overall visibility of all structures^[22],which indicated that modified paramedian technique might be beneficial for spinal anesthesia. In conclusion, modified paramedian for lumbar puncture is supported by relevant anatomical theories.

Chen et al.^[23] showed that compared with paramedian approach, modified paramedian approach had a higher first-attempt success rate and patient satisfaction, fewer number of attempts in pregnant,which was a feasible approach for residents.But it’s not clear if it’s be true for elderly.We firstly conducted the randomized controlled study on the application of preprocedural ultrasound modified paramedian technique for elderly, and compared it with two traditional techniques. The results showed the first-attempt success rate was higher significantly in group PM (77.6%) than groups M and P (47.8% and 42.9%). Compared with the latter, group PM had a fewer number of attempts and a higher patient satisfaction.When compared with group M, group PM had a significantly fewer needle redirections and a shorter procedure time.While compared with group P, there were no statistically significant difference.As we thought, modified paramedian technique was easy to learn and operate for beginners without an increasing of postoperative adverse reactions, which was consistent with the previous study^[23]. The reasons may be as follows:1)Compared to paramedian technique,the injection site of modified paramedian technique is closer to the midpoint of spinous process space, and the path of needle insertion is shorter. For residents with less clinical experience, the angle and depth of needle insertion are easier to grasp.2)Compared to midline approach, it bypasses the bony three-dimensional structure of lumbar spine to a certain extent, deviates from spinous process, and weakens the influence of intervertebral space stenosis on puncturing.3)The needle is walked superiorly on the lamina and advanced into the interlaminar space through the ligamentum flavum^[24].As we all know,the distance of lamina space is larger than that of spinous process space in the horizontal direction, so the probability that the needle tip touches bones is reduced.In all,modified paramedian technique combines the advantages of two traditional techniques, making it more feasible to apply in spinal anesthesia for elderly.

In order to explore the effect of three techniques in patients of different age, all patients were divided into two groups according to age for subgroup analysis.We found that the puncturing time in group PM was significantly shorter than group M for all patients , and there was no significant difference between groups PM and P .For patients aged 65-74 years,the number of needle redirections in group PM was significantly fewer than group M,and the number of attempts was significantly fewer in group PM than group P. Compared to groups M and P, the first-attempt success rate was significantly higher in group PM. However, for the above indicators,there was no statistical difference among the three groups in patients aged ≥75 years. This may be related to the uneven distribution of the two age groups. Patients over 75 years old accounted for a small proportion(only about 30% of the total number of patients in each group),resulting in a small sample size. Although there were differences in some results, they were not statistically significant. The satisfaction score of patients in group PM was significantly higher than groups M and P in patients aged ≥75 years, but it wasn’t in patients aged 65-74 years, which may be related to the differences in patients' life experience, education level, psychological quality and other aspects. In addition, through intragroup comparison, we found that under the condition of using the same technique, the first-attempt success rate decreased with the increasing of age, while the number of needle redirections, number of attempts and puncturing time increased. This indicated that there was a certain correlation between age and the difficulty of lumbar puncture in elderly patients, which is consistent with previous research^[25].

Our study has some limitations.Firstly, the injection site was 0.5cm lateral on the right of the midline in the test.Previous studies reported that the thickness and density of ligaments on both sides of the midline were different.Ligamentum flavum was significantly thicker on the right side^[26,27].We did not explore whether it was better to identify the site as 0.5cm lateral on the left of the midline or not,which is worthy of a further study.Secondly,the study did not apply for real-time ultrasound guidance technique, which could be superior to ultrasound-assisted technique because of the advantages of full visualization.Thirdly,we felt the reduced resistance during the procedure of insertion, but we didn’t explore structures that the needle passed through. There has been no consensus in the reason up to now. Lastly,we only collected data about patients’ postoperative adverse reactions within 24 hours after surgery,the chance are that the collected values are less than actual values.

In summary, modified paramedian approach has certain advantages in spinal anesthesia performed by residents for elderly with a higher first- attempt success rate and patient satisfaction, a fewer attempts and a shorter procedure time.We think it can provide a reference for clinical practice. However, there are few related clinical studies on the approach , and further studies are still needed.

Ethics approval and consent to participate

The study was approved by The Ethics Committee of the Second Hospital of Lanzhou University (2021A-106) and registered on 21/06/2021, at the China Clinical Trial Registration Center (http://www.chictr.org.cn/) (registration number: ChiCTR2100047635). All patients provided written informed consent.We carried out the study in full accordance with the Declaration of Helsinki.

Consent for publication

Not applicable.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests

Authors’ contributions

Yi-sa Shi designed the study and conducted the trial. Wei Zeng designed the study, wrote the manuscript and was responsible for performing spinal anesthesia during the study .Qi-hui-Zheng performed ultrasound-assisted location.Sheng-fang Du was responsible for collecting and analyzing the data and a follow-up within 24h after surgery. All authors have read and approved the manuscript.

Funding

This research study was supported by Cuiying Scientific and Technological Innovation Program of Lanzhou University Second Hospital,China.

Acknowledgements

The authors thank the patients who participated in the study and the surgeons(Department of urology, the Second Clinical Hospital of Lanzhou University,Lanzhou City, Gansu, China) for their help and support.

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Reina M A , Lirk P , A Puigdellívol-Sánchez, et al. Human Lumbar Ligamentum Flavum Anatomy for Epidural Anesthesia: Reviewing a 3D MR-Based Interactive Model and Postmortem Samples[J]. Anesthesia and analgesia, 2016, 122(3):903-907.

No competing interests reported.

The exploration of ultrasound-assisted modified paramedian technique for spinal anesthesia in elderly

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Abstract

Background

Methods

Data collection

Statistical Analysis

Results

Discussion

Conclusion

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References

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