Subarachnoid block with Taylor's approach for surgery of lower half of the body and lower limbs: A clinical teaching study.

BACKGROUND: Subarachnoid anesthesia is used as the sole anesthetic technique for below umbilical surgeries, but patients with deformed spine represent technical difficulty for its establishment. This study was aimed to find out whether training of Taylor's approach to residents on normal spine is beneficial for establishing subarachnoid block in patients with deformed spine.
MATERIALS AND METHODS: The total of 174 patients of ASA I-III with normal and deformed spine of both genders scheduled for below umbilical surgeries under the subarachnoid block and met the inclusion criteria, were enrolled for this two-phased clinical teaching study. All participating residents have performed more than 100 subarachnoid block with the median and paramedian approach. Residents were randomized into two equal groups. During the first phase program, Group I was taught Taylor's approach by hands on method for the subarachnoid block while Group II kept on observation for the technique. During the second phase of program, Group II was also taught Taylor's approach for establishing the subarachnoid block. Block success was defined according to clinical efficacy.
RESULTS: The results of teaching of Taylor's approach were encouraging. Initially, the residents faced difficulty for establishing the subarachnoid block in deformed spine but after learning by observation and practical hands on, both groups had successfully performed the subarachnoid block by Taylor's approach in one or more attempts in patient with deformed spine with the acceptable failure rate of 15%.
CONCLUSION: Taylor's approach for establishing subarachnoid block in deformed spine should be taught to residents on normal spine.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Central neuraxial anesthesia greatly expands the anesthesiologist armentarium providing the alternative to general anesthesia, and reduces the incidence of major perioperative complications including deep vein thrombosis, pulmonary embolism, blood loss, and respiratory complications. Subarachnoid anesthetic techniques have proved to be extremely safe and require a small volume of drug, virtually devoid of systemic pharmacologic effects, to produce profound, reproducible sensory analgesia, and motor blockade. Even epidural anesthesia necessitate the use of large mass of local anesthetic drug that produces pharmacologically active systemic blood levels, which may be associated with side effects and complications unknown with spinal anesthesia.[1-3] But the acquisition of this skill can be especially challenging for the residents as it requires more highly developed motor and visual skills.

Patients with deformed spine due to scoliosis, kypho-scoliosis, or arthritis (osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis) are challenging for anesthesiologist due to technical difficulty for establishing the successful subarachnoid block because of rotation of spine, limited articular mobility, obliteration of the interspinal spaces, and impossibility to position the patients adequately. In many patients accurately determining the optimal puncture site is impossible. The abnormal interspace shows asymmetry of bony structures, with asymmetric articular process. Abnormal anatomy can be present in patients for reasons other than obesity and scoliosis. The paramedian technique may be selected in patients who cannot be positioned easily due to skeletal deformity and a modification of paramedian technique by Taylor's approach has provided a reliable and less traumatic alternative in deformed spine for establishing the subarachnoid block.[4-6]

This study was aimed to teach Taylor's approach for establishment of the subarachnoid block to residents on patients with normal spine to benefit the patients with deformed spine.

MATERIALS AND METHODS

After approval of Institutional Ethical Committee and written informed consent, 150 patients of normal spine and 24 patients of deformed spine of both genders with ASA physical status I to III scheduled for below umbilical surgeries under the subarachnoid block were enrolled for this two-phased clinical teaching study. Patients who are receiving cardiovascular medication, on anticoagulants and antiplatelet drugs, hypersensitivity to local anesthetic or having contraindication to regional anesthesia were excluded from the study. All patients were evaluated clinically with routine investigations preoperatively. The radiographs of the spine were reviewed before attempting the subarachnoid block by median, paramedian or Taylor's approaches.

All participating eight residents have already performed more than 100 subarachnoid blocks and were well versed with median and paramedian approaches. These residents were randomly divided into two groups by chit method for teaching the establishment of the subarachnoid block in normal spine. During the first phase of teaching, Group I was taught Taylor's approach for establishing the subarachnoid block by hands on training while Group II was kept on observation only. During the second-phase teaching program, Group II was also given hands on training. The objective measure used to define the degree of success was obtaining cerebrospinal fluid during attempted spinal anesthesia.

After arrival in the operation theater, standard monitoring including heart rate, continuous electrocardiogram, pulse oximetry, and noninvasive measurement of arterial blood pressure, cycled at 3 min intervals were done and Ringer lactate infusion was stared at rate of 15 mL/min in nondominant forearm. The lumber puncture was performed with 24 gauge quincke spinal needle in the sitting position under all strict aseptic precautions at L2-L3 or L3-L4 interspace using median or paramedian approaches in patients with normal spine. After identification of correct needle placement by free flow of cerebrospinal fluid, the subarachnoid block was established and patient turn to the supine position.

Taylor's approach technique: a variation of the paramedian approach, described by Taylor was carried out at the L5-S1 interspace, the largest interlaminar interspace of the vertebral column. A spinal needle is inserted in a cephalo-medial direction through a skin wheel raised 1 cm medial and 1 cm caudal to the lowermost prominence of the posterior iliac spine. The posterior superior iliac spines may be located immediately anterior to the “skin dimples” often found overlying the superior aspect of sacrum [Figures 1 and 2]. If bone is encountered on initial needle insertion, the needle is walked off the sacrum to enter the subarachnoid space. After cerebrospinal fluid (CSF) is obtained, the subarachnoid block is carried out.

Figure 1

Patient showing lumbar scoliosis

Figure 2

Showing Taylor's approach for the subarachnoid block

The first 10 blocks by Taylor's approach were performed under direct supervision by the consultant anesthesiologist, there after the residents continued independently but with a consultant anesthesiologist present in the operation theater and on call for help at any time. The block success was defined as the correct identification of proper space followed by obtaining the free flow of cerebrospinal fluid. Other outcome measures such as onset, intensity, or extent of the block were not recorded. The number of skin puncture and time taken to perform the block were all recorded as secondary end points. The numbers of procedures performed until attainment of acceptable failure rates.

At the beginning of the teaching, residents were instructed about criteria for failure and success of Taylor's approach for establishing the subarachnoid block. Outcomes were measured on a binary variable, 1 representing success and 0 representing failure. Consultant took over procedure after two unsuccessful attempts or at any time if judged appropriate for the patient's comfort or safety. In that case, the outcome was rated as a failure. The acceptable failure rate at the space chosen was 15%.

No sample size calculation was performed due to lack of analysis methods for comparing the learning curves. No attempts were made to select cases according to predicted difficulty criterion for establishing the subarachnoid block.

RESULTS

Total of 174 patients of both gender, with ASA I to III scheduled for below umbilical surgical procedures under subarachnoid block were enrolled for this clinical teaching study. The 150 patients were of normal spine and 24 patients were of deformed spine due to scoliosis or arthritis. The groups were similar with regards to preoperative patient's demographic profiles. The mean number of procedures per residents was 34.13 ± 8.9. No statistical inference could be made about the performance of residents because the number of participating residents was quite less. The results of teaching Taylor's approach on normal spine for establishing the subarachnoid block were encouraging.

Initially, the residents faced difficulty for instituting the subarachnoid block in deformed spine but after learning by observation and practical hands on they were well versed with the technique. Group I has successfully established the subarachnoid block in deformed spine by paramedian approach (2 patients) or by Taylor's approach (10 patients) in first or second attempts with 92% success rate, while Group II residents could establish subarachnoid block in 5 out of 12 patients with deformed spine by paramedian approach and in rest seven patients they could not during the first phase of training program. Those subarachnoid blocks were later given by consultant anesthesiologist. Later on during the second phase of training program, Group II was also taught Taylor's approach to establish the subarachnoid block on normal spine. They could also perform the technique with 15% acceptable limit of the failure rate.

Resident who learned the Taylor's approach technique expressed that it was easy for them to performed subarachnoid anesthesia to the patients with deformed spine as they have already learned Taylor's approach on patients with normal spine and hence they were confident and could easily perform the technique.

DISCUSSION

The spinal anesthesia can be used to provide surgical anesthesia for all procedures carried out on the lower half of the body, lower limbs, pelvis, genitals, and perineum. The concept of spinal anesthesia is simple enough but the pertinent anatomy must be kept in mind while inserting the spinal needle for establishing the subarachnoid block.[1-3] Patients with deformed spine due to scoliosis, kypho-scoliosis, or arthritis (osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis) represent specific challenges to the anesthesiologist due to anatomical and technical difficulty for establishing the successful subarachnoid block.[4-6] Kypho-scoliosis is characterized by anterior flexion and lateral rotation of vertebral column. Spinal curvature of more than 40° is considered severe and is likely to be associated with physiological derangements in the cardiac and pulmonary function. Regional anesthesia is difficult in these patients with an increased incidence of complications and failure to obtain satisfactory analgesia.[7] General anesthesia can also be difficult in view of the antecedent risk factors associated with these diseases.

The anatomic midline approach is the technique of first choice because it is often easier to appreciate and requires anatomical projection in only two plans-sagittal and horizontal and provides a relatively avascular plane. When difficulty in needle insertion is encountered due to scar tissue, arthritic changes or scoliosis of spine, one option is to use the paramedian route. It does not require the same level of patient cooperation and reversal of lumbar lordosis for success of lumber puncture. The paramedian approach requires an additional oblique plane to be considered.[8]

A variation of the paramedian approach is the lumbo-sacral approach, described by Taylor. This technique is carried out at the L5-S1 interspace by inserting the spinal needle in a cephalo-medial direction, 1 cm medial and 1 cm caudal to the lowermost prominence of the posterior iliac spine. Jindal et al. successfully used Taylor's approach to establish the spinal anesthesia in an ankylosing spondylitis patient posted for percutaneous nephrolithotomy.[9]

Subarachnoid block at L5-S1 interlaminar space offers distinct advantages. It is lowest and widest available lumber space, so the chances of trauma to spinal cord are negligible. This space is least affected by arthritic and degenerative changes; hence, Taylor's approach is better alternative than a midline approach for establishing the subarachnoid block with adequate sensory and motor blockade for the surgical procedure. The acquisition of knowledge and skills pertinent to the use of Taylor's approach for establishing the subarachnoid block is an important part of learning. The teaching of procedures facilitates the learning curve and increases safety. It shortens the duration of procedure and increases the comfort due to reduced number of attempts and subsequent trauma.

Several methods have been developed for measuring competence at important aspects of training, such as cognitive knowledge, judgment, communication skills, and adaptability by means of written or oral examination. However, resident's aptitude at procedural skill is not routinely quantified. As a consequence, how and when residents achieve their level of proficiency is not exactly known. An easily obtainable quantitative measure of performances would help objective evaluation of resident performance, contributing to a better training.

Kopaiz et al. by using the pooled cumulative success rate concluded that a 79.3% success rate at spinal anesthesia was achieved after 41 attempts.[10] Konrad et al. Using a least square fit model and Monte Carlo procedures demonstrated that 90% success rate at spinal anesthesia was achieved after mean 71 attempts.[11] In this study, we have randomized those residents who have experience of performing more than 100 subarachnoid blocks successfully. Success at spinal anesthesia was defined as good surgical anesthesia after subarachnoid block at first chosen intervertebral space.

Wide variability exists in the regional anesthesia practice to which residents are exposed during the training. The number of attempts at various blocks before the trainee resident becomes proficient at performing these regional anesthetic techniques is not known. It is desirable to keep the average number of procedures low to detect failure rates, so that corrective measures can be taken at relatively short intervals. The patient's variables may also influence the success rates of individual. Approximately 20 to 25 procedures are necessary before improvement in the technique of spinal anesthesia. Training in anesthetic procedures is made under regressive supervision, that is the more proficient the resident becomes at a given technique, the less supervision is provided by the consultant. We recommend a close supervision for at least the first 15 blocks performed by residents. The initial learning phase of residents acquiring the method for the first time is not the terminal success rate or the level of proficiency of experts. Improvement in the technique may be continued beyond the first 20 to 25 blocks due to the constant technique refinement that may improve the final success rate to a much higher level.

CONCLUSION

Subarachnoid anesthesia has the potential to provide excellent operating conditions with fewer side effects but patients with deformed spine due to scoliosis, severe arthritis, or prior spine surgery represent challenges due to anatomical and technical difficulty for establishing the successful subarachnoid block. Taylor's approach could provide a reliable and less traumatic alternative to midline approach for lumber puncture in deformed spine and should be taught to residents on normal spine to facilitate the learning curve.