The Paramedian Technique: A Superior Initial Approach to Continuous Spinal Anesthesia in the Elderly

Abstract

BACKGROUND: 

Spinal anesthesia in elderly patients is frequently associated with significant technical difficulties. Thus, we compared the classical midline approach to the paramedian approach to perform continuous spinal anesthesia (CSA).

METHODS: 

We prospectively studied 40 patients aged >75 yr who underwent open surgical repair of a hip fracture. These patients were randomly allocated to one of two groups: Group M: midline approach, and Group PM: paramedian approach. Patients were positioned in the lateral decubitus to receive CSA at L4-5 level. CSA was considered successful if cerebrospinal fluid was obtained through the needle. In case of initial failure in either approach, the same approach was repeated by the same operator. If two attempts were unsuccessful, the other anatomical approach was used by the same operator. If both approaches failed, a staff anesthesiologist performed a final attempt. In case of failure or insufficient block, the patient received general anesthesia.

RESULTS: 

The success rate after the first attempt was 85% (17) for Group PM and 45% (9) for Group M (P = 0.02). All catheters were successfully introduced. No patient required general anesthesia. Vascular puncture after needle puncture was observed in six patients in Group M versus 0 in Group PM (P = 0.03), but none were of clinical consequence. No other clinically significant complications were observed.

CONCLUSION: 

In summary, after the initial attempt, the paramedian approach is associated with an increased success rate, compared with the midline approach, during the performance of CSA in elderly patients.

In Brief

IMPLICATIONS: After a single attempt, the paramedian approach is associated with an increased success rate, compared with the midline approach, during continuous spinal anesthesia in elderly patients.

A midline approach is the most common technique when spinal anesthesia is performed (¹). However, this approach is often technically difficult in the geriatric population because of degenerative changes in the structural elements of the spine (²). Thus, a paramedian approach may be more appropriate in this patient population because it is affected less by osteoarthritis changes. However, there is a lack of data directly comparing the two approaches for continuous spinal anesthesia (CSA) in elderly patients.

This study aims to compare the success rates of the midline versus paramedian approach in elderly patients undergoing surgical repair of hip fractures.

METHODS

After approval by the local Ethics Committee, all patients (>75 yr) who provided written informed consent were randomized (sealed envelope) to receive CSA by either a midline (Group M, n = 20) or a paramedian (Group PM, n = 20) approach. Exclusion criteria included the presence of any contraindication to CSA.

Standard monitoring was applied. Patients received 0.5 mg/kg propofol IV before being turned to the lateral decubitus position and the puncture site prepared antiseptically (³). All lumbar punctures were performed by either a resident or staff anesthesiologist experienced in the midline and paramedian approach to CSA. We performed CSA because it creates less hemodynamic instability related to its slow incremental dosing and gradual onset of sympathetic block (⁴).

For the PM Group, a previously described approach was used (⁵). Briefly, to access the intrathecal space, local anesthetic (lidocaine 1% without epinephrine, Aguettant, Lyon, France) was administered at 1 cm lateral to the midline of the L4-5 interspace. A 19-gauge Tuohy needle was inserted perpendicularly to the skin until it contacted bone with a cephalic orientation of the bevel. The needle was then slightly retracted and redirected in a cephalad and medial trajectory at a 10°–15° angle from the midline and inserted through the ligamentum flavum and dura. After cerebrospinal fluid (CSF) was obtained, a 22-gauge catheter (VYGON; Ecouen, France) was advanced 2 cm cephalad into the intrathecal space and secured.

For Group M, a standard approach was used as previously described using the same 19-gauge Tuohy needle as in the paramedian approach (⁴). After CSF was obtained, the 22-gauge catheter was introduced as with the paramedian approach and was taped in place.

In case of unsuccessful attainment of CSF after a single pass (initial failure) in either approach, the same approach was repeated by the same operator. An attempt was considered unsuccessful if the operator removed the stylet and saw no CSF. If two attempts were unsuccessful, the other anatomical approach was used by the same operator. If both approaches failed, a staff anesthesiologist performed a final attempt. The number of needle redirection attempts was at the judgment of the operator. The operator withdrew the stylet when he/she felt the needle at the right place. In case of failure or insufficient block, the patient received general anesthesia. All failures and reattempts were noted by an independent observer at each attempt. The duration of the procedure was defined as needle insertion to withdrawal.

Before the trial, and based on previous studies (^6,7), a power calculation for a 45% difference in the success rate with a probability level of 0.05 and power of 0.80 (1−β) yielded a sample size of 20 patients for each group. Statistical analyses were performed using the Statview® software (version 5.0, SAS Institute, Cary, NC). Data are presented as mean ± sd unless stated otherwise. To compare data between groups, a χ² test or a Student’s t-test was used. P < 0.05 was considered statistically significant.

RESULTS

All 40 patients completed the investigation. There were no significant differences in demographic and surgical characteristics (Table 1).

Table 1: Demographic and Surgical Data

The success rate was 85% (17) for Group PM and 45% (9) for Group M (P = 0.02) after the first attempt (Fig. 1). In three patients in Group PM, CSF was not obtained using the paramedian approach, requiring an attempt at the midline (two by resident, one by staff). Two were successful with the midline approach. The single failure was performed by a resident; thus a senior performed the last attempt by paramedian approach and succeeded. CSF was not obtained in 11 patients in Group M, leading to a paramedian approach (six by resident, five by staff). Ten were successfully performed by the same operator using the paramedian approach. The single failure was performed by a resident, after which a senior successfully performed the last attempt by paramedian approach.

Figure 1.: Success rate after the first attempt (%). PM = paramedian approach; M = median approach; *P < 0.05.

Procedure data are shown in Table 2. All catheters were successfully introduced, and CSA was successful in all patients in the study (no patient required general anesthesia).

Table 2: Procedure Data

Vascular puncture through the needle occurred in six patients in Group M versus zero in Group PM (P = 0.03), but none had clinical consequence.

DISCUSSION

This study, the first prospective randomized investigation comparing midline and paramedian approaches to CSA in the elderly, found a higher initial success rate using the paramedian approach. Performing CSA on the elderly hip fracture patient presents the practitioner with the dual challenge of limited positioning due to pain coupled with age-related anatomical changes to the intervertebral space, both of which may complicate needle insertion. Most practitioners continue to use the midline rather than the paramedian approach (¹).

Previous studies of lumbar epidural rather than CSA catheter placement have shown advantages of the paramedian approach over the midline approach. Effectively, it allowed a faster catheter insertion (⁸), fewer attempts at needle insertion (⁶), and can be performed in an unflexed spine position (⁷).

Although both the paramedian and midline approaches were performed with the patient in the lateral decubitus position, the paramedian approach did not require flexion of the spine, unlike the midline approach. Such positioning can be an additional source of discomfort to the elderly patient with a major fracture and may be yet another advantage of the paramedian approach in these cases; however, our study did not assess patient comfort, as it focused primarily upon technical outcomes.

In summary, this study has demonstrated the effectiveness of the paramedian approach over the midline approach as the technique of choice for CSA in the elderly patient, and its success as a rescue technique. We conclude that further training and proficiency in this technique is warranted.