The stakes reach well beyond the need for an extra dose of pain relief. When a neuraxial block proves inadequate, women may endure intraoperative pain, visceral discomfort, and anxiety during one of the most emotionally charged operations of their lives, and their satisfaction with the childbirth experience can suffer. Unplanned conversion to general anesthesia exposes both mother and neonate to additional risks and remains among the most concerning complications of obstetric neuraxial anesthesia. Recent systematic reviews and professional recommendations have increasingly framed intraoperative pain during cesarean delivery under neuraxial anesthesia as an important quality indicator that should be recognized promptly and managed effectively. Identifying patients at elevated risk before surgery, the authors argue, could allow anesthesiologists to tailor their anesthetic plan rather than react to failure mid-operation.

The research team, from the Department of Anesthesiology at Lokman Hekim University in Ankara, mined electronic health records and patient follow-up forms for every adult who underwent cesarean delivery under planned spinal anesthesia during the six-year window. Patients under 18, those receiving epidural or combined spinal-epidural techniques, and those planned for general anesthesia were excluded. The investigators drew a sharp three-way distinction: an adequate block provided sufficient surgical anesthesia without any supplemental analgesic or sedative medication and without conversion to general anesthesia; a partial block required supplemental intraoperative medication but no conversion; and a failed block was insufficient for surgery altogether, forcing a switch to general anesthesia. By combining partial and total failures into a single measure of inadequacy, the design deliberately captured the full clinical burden of block insufficiency rather than only its most dramatic endpoint.

The headline numbers tell a story of overall success shadowed by persistent imperfection. Adequate spinal anesthesia was achieved in 3,216 patients, or 95.1 percent of the cohort. The remaining 166 patients, 4.9 percent, experienced an inadequate block, split into 135 partial failures, 4.0 percent, and 31 total failures, 0.9 percent. The demographic contrasts were striking. Patients with inadequate blocks had a median age of 24 years compared with 31 years in the adequate group, a median body weight of 75 kilograms versus 70 kilograms, and a median body mass index of 31.17 versus 27.11 kilograms per square meter. Height was slightly lower in the inadequate group. Gestational age at delivery, by contrast, did not differ significantly between the two groups.

To disentangle which characteristics truly drive block inadequacy, the team ran univariate and multivariable logistic regression analyses. In the unadjusted analysis, increasing age was associated with lower odds of inadequate block, with an odds ratio of 0.642, while higher body mass index, lateral positioning, postpartum sterilization, and surgical adhesions each carried substantially higher odds, and higher educational level was again protective. After adjustment for potential confounders, four factors survived. Increasing age remained associated with lower odds of inadequate block, with an adjusted odds ratio of 0.524, and higher educational level retained a protective association with an odds ratio of 0.678. Postpartum sterilization emerged as the strongest independent risk factor, with an adjusted odds ratio of 9.535, followed by the presence of surgical adhesions at 3.010. Body mass index and lateral position, despite their strong univariate signals, did not remain independently associated after adjustment.

The sterilization finding is the most dramatic in the dataset. Among the 3,353 patients who did not undergo postpartum sterilization, 142, or 4.2 percent, experienced an inadequate block. Among the 29 who did, 24, or 82.8 percent, required supplemental management. The authors attribute this to the nature of tubal ligation performed during cesarean delivery, which demands additional traction on the fallopian tubes and increased peritoneal manipulation. Such maneuvers can provoke visceral discomfort even when the somatic block covering the skin and abdominal wall is otherwise adequate, raising the likelihood that supplemental sedation or analgesia will be needed. Previous obstetric cohorts have likewise identified concomitant tubal ligation as a predictor of inadequate neuraxial anesthesia, and separate studies of spinal anesthesia for postpartum tubal ligation have reported relatively high failure rates even with de novo spinal techniques, reinforcing the idea that added surgical manipulation challenges the limits of a single-shot block.

Surgical adhesions tell a complementary story. In this cohort, 5 of 16 patients with observed adhesions, 31.3 percent, had an inadequate block, compared with 161 of 3,366 patients without adhesions, 4.8 percent. Adhesions, the authors explain, may increase surgical complexity, prolong operative duration, and require more extensive visceral manipulation. Under these circumstances, the intensity or duration of surgical stimulation may simply exceed the analgesic coverage that a single-shot spinal technique can provide. Prior observational work has noted that increased surgical manipulation, including exteriorization of the uterus or complications during obstetric surgery, is associated with greater requirements for supplemental analgesia, suggesting that surgical factors, not just patient characteristics, shape whether a block proves adequate.

The treatment of body mass index and patient position illustrates how easily unadjusted associations can mislead. Obesity theoretically enhances the cephalad spread of intrathecal local anesthetics through increased intra-abdominal pressure and reduced cerebrospinal fluid volume, which should favor a denser block. But increased body habitus also makes anatomical landmarks harder to identify, increases the depth to the intrathecal space, and can make needle placement less precise. These opposing physiological and technical mechanisms, the authors suggest, explain why the relationship between obesity and neuraxial block adequacy has been inconsistent across previous studies, and why body mass index lost significance in their adjusted model. Similarly, while only 65.0 percent of the 20 patients positioned laterally achieved an adequate block compared with 95.3 percent of those positioned sitting, the lateral position was not independently associated with inadequacy after adjustment. Needle type, whether cutting Quincke or pencil-point, and American Society of Anesthesiologists physical status showed no significant association with block adequacy at all.

The findings land in a literature marked by striking heterogeneity. A recent meta-analysis reported a pooled incidence of failed spinal anesthesia of 8.36 percent, with a 95 percent confidence interval of 6.94 to 9.78. A large retrospective review of 5,361 cesarean deliveries found that spinal anesthesia failed to provide pain-free surgery in 4.1 percent of cases, with conversion to general anesthesia in 0.7 percent and supplemental analgesia or sedation in an additional 2.0 percent. At the other extreme, a prospective observational cohort of 275 parturients reported an overall failure rate of 19.5 percent, with emergency procedure, needle size, anesthetist experience, and local anesthetic volume among the associated factors. The authors note that much of this variability stems from differing definitions: studies that count only conversion to general anesthesia as failure report lower rates, while those that also include the need for supplemental medication report higher ones. By adopting the broader definition, the current study argues, research better reflects the true clinical burden.

The authors are candid about the limits of their evidence. The retrospective design restricts control over confounding and depends on the accuracy of medical record documentation. Key procedural variables, including the number of puncture attempts, emergency status, operative duration, and the intrathecal anesthetic dose or volume, were unavailable or inconsistently documented and could not be evaluated, so residual confounding cannot be excluded, particularly for the associations with postpartum sterilization and surgical adhesions. The exact indications for supplemental intraoperative medications could not be reliably determined from the records, and the strong inverse association between maternal age and inadequate block should be interpreted cautiously, since additional model-diagnostic analyses were not available to establish its robustness. Even so, the practical message stands: with nearly one in twenty blocks proving inadequate, and with identifiable patient and surgical characteristics flagging elevated risk, preoperative recognition of high-risk patients may allow anesthesiologists to optimize anesthetic planning and individualize management to safeguard maternal comfort during cesarean delivery.

Subject of Research: Incidence and predictors of inadequate spinal anesthesia during cesarean delivery

Article Title: Inadequate neuraxial anesthesia during cesarean delivery: incidence and predictors in a large retrospective contemporary cohort

Article References: Demir, O., Yondem, O. Z., & Yuksel, B. E. (2026). Inadequate neuraxial anesthesia during cesarean delivery: incidence and predictors in a large retrospective contemporary cohort. Frontiers in Medicine, 13, Article 1930644. https://doi.org/10.3389/fmed.2026.1930644

Image Credits: AI Generated

DOI: 10.3389/fmed.2026.1930644

Keywords: spinal anesthesia, cesarean delivery, neuraxial anesthesia, inadequate block, postpartum sterilization, surgical adhesions, obstetric anesthesia, retrospective cohort, intraoperative pain, general anesthesia conversion, body mass index, logistic regression