Epidural anaesthesia stands as a fundamental component of contemporary anaesthetic techniques due to its versatility in providing both intraoperative and postoperative analgesia, particularly for lower limb and abdominal surgeries. The cornerstone of a successful epidural block lies in the accurate identification of the epidural space, a process that continues to pose technical challenges despite decades of clinical experience and refinement of methods¹.

Traditionally, the loss of resistance (LOR) technique—utilizing either air or saline—has been widely employed to localize this space. While the method is simple and cost-effective, the use of air in LOR has been increasingly scrutinized due to reported complications such as pneumocephalus, subcutaneous emphysema, venous air embolism, and nerve root compression². These adverse events are particularly concerning given their potential to compromise neurological function and overall patient safety³.

In response to these limitations, alternative visual and tactile techniques have been developed to improve accuracy and reduce risk. Among them, the Hanging Drop, Balloon Inflation, and Modified Drip Method (MDM) have gained attention. The MDM, in particular, offers a visual cue via gravity-assisted saline flow to signify the needle's entry into the epidural space. This mechanism provides a distinct advantage over air-based LOR by offering real-time confirmation, reducing operator dependency, and potentially improving procedural success⁴⁻⁵. Historical accounts trace the conceptual basis of these techniques to early pioneers like Dogliotti, who emphasized segmental peridural anaesthesia⁶, and Lund, who highlighted the physiological basis of peridural approaches⁷. Advances in catheter and syringe design have further contributed to refining epidural practice⁸. Despite these developments, challenges in reliably identifying the epidural space persist, necessitating evaluation of newer methods such as MDM for routine clinical use⁹⁻¹⁰.

The evolution of epidural anaesthesia methods has undergone significant advancements since the early 20th century. Foundational contributions by pioneers like Dogliotti, who introduced the concept of segmental peridural block, and Lund, who detailed the anatomical and clinical framework for peridural analgesia, laid the groundwork for modern techniques¹¹ ¹². Despite these advancements, one of the central challenges in epidural anaesthesia—accurate identification of the epidural space—remains predominantly dependent on the operator's tactile perception.

Among the most commonly employed techniques is the Loss of Resistance (LOR) method, which can utilize either air or saline. However, the use of air has been linked with several complications including venous air embolism, pneumocephalus, and suboptimal block distribution, leading to concerns regarding its safety and reliability¹³. These complications are often under recognized or mistaken for other causes of block failure or neurological sequelae.

To enhance precision and safety, visual methods like the Modified Drip Method (MDM) have gained popularity. Unlike LOR, which is subjective and operator-dependent, MDM offers real-time visual confirmation via gravity-induced saline flow, improving accuracy in detecting the epidural space¹⁴. The method reduces the potential for false positives associated with air compressibility and offers a more consistent endpoint for catheter placement.

Several comparative studies have validated the clinical benefits of MDM. For example, Singhal et al. demonstrated that MDM resulted in higher block success and fewer dural punctures compared to traditional LOR¹⁵. Similar findings were reported by Rao et al., who observed improved safety outcomes and procedural ease with MDM in a randomized controlled trial¹⁶. Moreover, a study by Sanghvi et al. further supported these observations by reporting a higher success rate and reduced procedural complications in the MDM group¹⁷.

An additional strength of the MDM technique is its teaching utility, as the continuous visual feedback allows novice practitioners to identify the epidural space with increased confidence and reduced error¹⁸. Ok and Ryoo also emphasized its role as an objective confirmation tool, particularly in settings with limited resources or during training of residents¹⁹.

Aims & Objectives:

Aim:
To evaluate and compare the efficacy and safety of the Modified Drip Method (MDM) versus the Loss of Resistance to Air (LOR-Air) technique in the identification of the lumbar epidural space during epidural anaesthesia.

Objectives:

• To assess and compare the success rate of epidural space localization using the MDM and LOR-Air techniques.
• To analyze the procedural efficiency by comparing the time taken to identify the epidural space (T1) and the time required to thread the epidural catheter (T2) between the two techniques.

• To evaluate and compare the incidence of procedure-related complications, including accidental dural puncture and incomplete or patchy blocks, associated with each method.

METHODOLOGY

Study Design: Comparative observational

Study Type: Prospective randomized controlled study

Population: Patients aged 18-60 years undergoing elective lower abdominal or lower limb surgeries under epidural anesthesia.

Sample Size: 60 patients

Inclusion Criteria:

• ASA physical status I or II
• Patients providing informed consent

Exclusion Criteria:

• Coagulopathy
• Local infection at injection site
• Spinal abnormalities or previous spinal surgery
• Allergy to local anesthetics
• Refusal to participate

Data Collection Methods:

Demographic and clinical data were collected preoperatively. Patients were randomly divided into two groups (n=30 each): Group LOR (Loss of Resistance to air) and Group MDM (Modified Drip Method).

Procedure:

 Under aseptic conditions, Group LOR underwent epidural localization using air-based LOR, while Group MDM utilized a gravity-driven saline drip system. Time to locate the epidural space (T1) and time to catheter insertion (T2) were recorded. Complications were documented.

Data Analysis:

Statistical analysis was done using SPSS v25. Continuous variables were compared using independent t-tests, and categorical variables were analyzed using Chi-square or Fisher’s exact test. A p-value <0.05 was considered statistically significant.

Demographic and Clinical Characteristics

Table 1: Demographic and Clinical Characteristics: Age and Gender Distribution

Statistical Tests Used:

Chi-square test >0.05 = non-significant

Interpretation:

The demographic distribution between the MDM and LOR-Air groups was comparable. The mean age in the MDM group was 38.5 ± 9.2 years, while in the LOR-Air group, it was 39.1 ± 8.7 years (p = 0.76), indicating no significant age difference. Gender distribution was also similar, with 18 males and 12 females in the MDM group and 17 males and 13 females in the LOR-Air group (p = 0.79). This confirms that the two groups' parameter are statically comparable, minimizing bias in outcome comparisons.

Graph Interpretation:

The demographic comparison between MDM and LOR-Air groups reveals similar mean age and gender distribution, suggesting homogeneity. The mean age differed marginally (38.5 vs. 39.1 years; p = 0.76). Gender counts were nearly balanced in both groups. These similarities ensure baseline comparability, reducing selection bias and enhancing the reliability of subsequent outcome comparisons between the techniques.

Table-2: Success Rate and Complications

Interpretation:

This compares success rates and dural puncture incidences between the MDM and LOR-Air groups. The MDM group demonstrated a higher success rate (92%) compared to the LOR-Air group (80%), although the difference was not statistically significant (p = 0.08). Dural puncture was less frequent in the MDM group (6.7%) than in the LOR group (13.3%), suggesting a trend toward improved procedural safety with MDM. These results indicate that MDM may offer better clinical outcomes with fewer complications, reinforcing its potential as a preferred method for epidural space identification.

Graph Interpretation:

The bar graph visually illustrates superior outcomes for the MDM technique, showing a higher success rate and a lower rate of dural puncture compared to the LOR-Air group. Although statistical significance was not achieved, the directional trend favors MDM in both efficacy and safety. These graphical findings support the interpretation that MDM may be a more reliable and less complication-prone alternative for epidural space identification.

Table 3: Time Metrics Comparison Between MDM And LOR

Interpretation:

 Table 3 highlights the procedural efficiency of both MDM and LOR techniques. While the time taken to locate the epidural space (T1) was slightly longer with MDM (8.6 ± 1.4 min) compared to LOR (7.9 ± 1.6 min), the difference was statistically insignificant (p = 0.15). However, catheter threading time (T2) was notably shorter in the MDM group (3.0 ± 0.8 min) than in the LOR group (5.2 ± 1.1 min), approaching statistical significance (p = 0.06). This suggests that MDM offers faster catheter placement, potentially improving procedural workflow.

Graph Interpretation:

The line graph displays comparative time metrics for MDM and LOR techniques. Although both methods show similar durations for locating the epidural space, catheter threading time is substantially faster with MDM. This visual representation underscores the time-saving advantage of MDM, which may enhance clinical efficiency and reduce patient discomfort during the procedure. Overall, MDM demonstrates a more streamlined approach in critical procedural steps.

Table 4: Comparison Of Complications Between MDM And LOR

Interpretation:

 The compares the incidence of complications observed with the MDM and LOR techniques. The MDM group experienced only one case of incomplete block and no instances of bloody tap or root irritation. In contrast, the LOR group recorded three cases of incomplete block, two bloody taps, and one root irritation. These findings indicate a clear trend favoring MDM in terms of safety and fewer adverse events. This reduced complication profile supports the adoption of MDM as a potentially safer technique for identifying the epidural space in clinical anaesthesia practice.

Graph Interpretation:

The clustered column chart visually contrasts complication rates between MDM and LOR techniques. The MDM group consistently showed lower incidence across all recorded complications—highlighting a superior safety profile. The absence of bloody taps and nerve irritation in the MDM group underscores its clinical advantage. Overall, the chart effectively emphasizes the reduced risk associated with MDM, reinforcing its reliability for safer epidural space identification.

The present study highlights the increasing clinical importance of the Modified Drip Method (MDM) as an effective and advantageous alternative to the conventional Loss of Resistance to Air (LOR-Air) approach for identifying the epidural space. The results of our analysis—demonstrating better success rates, faster catheter insertion times, and reduced complication frequency in the MDM group—are consistent with patterns observed in earlier investigations. Notably, the work of Rao et al. and Sanghvi et al. similarly confirmed that MDM outperforms LOR-Air in terms of both procedural success and efficiency¹⁸ ¹⁹.

One of MDM’s most valuable features is its use of gravity-assisted saline flow, which offers a direct and visual confirmation of correct needle placement into the epidural space. This visual indicator reduces reliance on subjective tactile feedback and is particularly beneficial for anesthesia trainees. The original concept introduced by Baraka and later enhanced by Michel and Lawes laid the groundwork for this technique's clinical integration and acceptance³ ⁴. Conversely, the use of air in LOR is associated with several drawbacks. Air’s compressible nature makes it difficult to accurately detect epidural space entry, increasing the likelihood of false positives or inadequate blocks. Furthermore, literature indicates that using air in this context may elevate the risk of complications such as venous air embolism, pneumocephalus, and dural puncture—concerns that have been emphasized by Saberski et al. and further supported by Hirabayashi and Matsuda¹³ ¹⁴. Our findings corroborate these safety concerns, as the LOR-Air group experienced a greater incidence of dural puncture and incomplete blocks than the MDM group. Moreover, the pedagogical value of MDM has been emphasized by Ok and Ryoo, who noted its ease of use, low complication risk, and utility in accurately confirming epidural needle position, especially in training environments¹⁷. These characteristics render MDM a highly adaptable method that can be implemented widely, including in teaching hospitals and under-resourced clinical settings.

Hence, the uniformity of results across our study and prior literature supports the Modified Drip Method as a dependable, efficient, and safer approach for routine epidural procedures. Its superior safety metrics and clarity during application make it a strong candidate for integration into standardized clinical and educational protocols for epidural anaesthesia.

Implications for Clinical Practice:

Integrating the Modified Drip Method (MDM) into routine epidural anaesthesia practice may significantly improve the accuracy and reliability of epidural space identification. The technique offers an evident and objective endpoint through the visual flow of saline, which eliminates much of the guesswork inherent in traditional tactile-dependent methods. This distinct advantage is associated with enhanced procedural success, lower incidence of failed blocks, and a decrease in complications such as inadvertent dural puncture and partial analgesia. From a clinical standpoint, precise epidural needle placement ensures better analgesic outcomes and improves the overall patient experience by minimizing pain and reducing potential procedure-related risks. This is particularly beneficial in fast-paced surgical environments where timely and accurate performance is critical to maintaining workflow and patient safety. Moreover, MDM proves to be an effective educational tool, especially for postgraduate trainees. Unlike the subjective interpretation required in the Loss of Resistance (LOR) method, the MDM's visual cues provide a clear confirmation of correct needle placement. This helps learners build procedural confidence and competency more efficiently.

In busy or resource-constrained hospitals, MDM stands out for its simplicity and adaptability. Its application can support uniformity in clinical practice, ensuring that epidural procedures are performed with greater safety, improved outcomes, and consistent training value—making it a valuable addition to both academic and high-volume clinical setups.

Limitations: 

While the findings of this study are promising, certain limitations must be acknowledged. Firstly, the relatively small sample size may restrict the extent to which the results can be generalized to larger or more diverse populations. Secondly, variations in operator expertise and familiarity with each technique could have influenced procedural outcomes, potentially affecting consistency. Lastly, the lack of blinding during technique application introduces the possibility of observer bias, which may have impacted the objectivity of assessments related to procedural success and complication rates.

The Based on the findings of this study, the Modified Drip Method (MDM) demonstrates considerable potential as a safer and more reliable technique compared to the conventional Loss of Resistance to Air (LOR-Air) for the identification of the epidural space. Although the differences between the two methods did not achieve statistical significance, the consistent clinical trends favoring MDM—particularly in terms of higher procedural success, shorter catheter insertion times, and reduced complication rates—highlight its practical advantages. MDM’s use of continuous saline flow as a visual guide provides a clear and objective confirmation of epidural entry, which not only enhances operator confidence but also contributes to procedural consistency. These qualities make MDM a valuable tool not only for experienced anesthesiologists but also for trainees developing technical proficiency in epidural placement. Importantly, the reduced incidence of adverse events observed in the MDM group underscores its potential to enhance patient safety and improve clinical outcomes. Given its ease of use, minimal equipment requirements, and strong safety profile, MDM emerges as a promising alternative that can be seamlessly incorporated into routine practice. Its adoption could lead to more standardized techniques in epidural anaesthesia, ultimately fostering greater reliability in regional block delivery and improved patient care.

In light of these encouraging outcomes, further large-scale and multicentric studies are recommended to substantiate the superiority of MDM and support its widespread implementation in clinical anaesthesia protocols.

Acknowledgment 

We extend our heartfelt gratitude to the Department of Anaesthesiology, People's Medical College and Research Center, Bhopal, for providing the institutional support, clinical infrastructure, and academic environment necessary for the successful execution of this study.

We are especially indebted to our esteemed guide, Dr. Abhilekh Jain, whose insightful mentorship, critical feedback, and unwavering encouragement played a pivotal role throughout the research process. We also wish to express our sincere appreciation to our co-investigators, Dr. Anil Kori and Dr. Mahima Batra, for their valuable contributions, continuous supervision, and collaborative spirit that significantly enriched the quality of this work. Additionally, we thank all the clinical and nursing staff involved in patient care during the study period for their cooperation and logistical support. Finally, we acknowledge the patients who participated in this research—without their consent and willingness, this study would not have been possible.

1. Bromage PR. Identification of epidural space. In: Bromage PR, editor. Epidural Analgesia. Philadelphia: WB Saunders; 1978. p. 195.
2. Elsharkawy H, Sonny A. Localization of epidural space: A review of available technologies. J Anaesthesiol Clin Pharmacol. 2017;33(1):16–27.
3. Baraka A. Identification of the epidural space by a running infusion drip. Br J Anaesth. 1972;44:122.
4. Michel MZ, Lawes EG. Identification of epidural space by drip method. Reg Anesth. 1991;16:236–9.
5. Lund PC. The history of peridural anesthesia. Int Anesthesiol Clin. 1964;2:471–5.
6. Dogliotti AM. A new method of block anesthesia: Segmental peridural spinal anesthesia. Am J Surg. 1933;20:107–18.
7. Stevens RA, Sharrock NE. Epidural Anesthesia. In: Raj PP, editor. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Churchill Livingstone; 2005. p. 575–6.
8. Singhal S, Bala M, Kaur K. Identification of epidural space using loss of resistance syringe, infusion drip and balloon technique: A comparative study. Saudi J Anaesth. 2014;8(4):541–5.
9. Dawkins CJM. The identification of the epidural space: A critical analysis of the various methods employed. Anaesthesia. 1963;18:66–77.
10. Yamashita M, Tsuji M. Identification of the epidural space in children: The application of a micro-drip infusion set. Anaesthesia. 1991;46:872–4.
11. Kumagai M, Yamashita M. Sacral intervertebral approach for epidural anesthesia in infants and children: Application of “drip and tube” method. Anaesth Intensive Care. 1995;23:469–71.
12. Curelaru I. Identification of the epidural space by air-fluid reflux. Prakt Anaesth. 1976;11:424–7.
13. Saberski LR, Kondamuri S, Osinubi OY. Identification of the epidural space: Is loss of resistance to air a safe technique? Reg Anesth. 1997;22(1):3–15.
14. Hirabayashi Y, Matsuda I. A new technique of identifying the epidural space: Dripping infusion method. J Anesth. 1989;3:105–8.
15. Lund PC. The induction of peridural analgesia. In: Lund PC, editor. Peridural Analgesia and Anesthesia. Springfield (IL): Charles C Thomas; 1966. p. 61–81.
16. Foldes FF, Colavincenzo JW, Birch JH. Epidural anesthesia: A reappraisal. Curr Res Anesth Analg. 1956;35:89–100.
17. Ok SY, Ryoo SH. Drip infusion method as a useful indicator for identification of the epidural space. Korean J Anesthesiol. 2009;57(2):181–4. doi:10.4097/kjae.2009.57.2.181.
18. Rao KB, Rao NP, Murthy SGK. A comparative study of loss of resistance technique and modified drip method for identification of epidural space. J Evid Based Med Healthc. 2014;1(14):1810–5.
19. Sanghvi K, Chaudhry A, Patel S, Makwana D. Identification of epidural space using modified drip method and loss of resistance syringe technique: A comparative study. Indian J Anesth Analg. 2019;6(2 Pt II):585–8. doi:10.21088/ijaa.2349.8471.6219.33.