When Wasp Stings May Blunt Spinal Anesthesia: Two Puzzling Cases

Spinal anesthesia is one of the most dependable tools in modern operating rooms. A single injection of local anesthetic into the cerebrospinal fluid surrounding the spinal cord can render a patient completely numb and immobile from the waist down, allowing hernia repairs, knee arthroscopies, cesarean sections, and countless other procedures to proceed without general anesthesia. Failures are rare, and when they do occur they are almost always traced to identifiable problems: a needle that missed its target, an inadequate dose, unusual spinal anatomy, or a patient factor such as obesity that interferes with drug spread. That is precisely why two cases reported in Clinical Case Reports have caught the attention of anesthesiologists. In both instances, healthy men received technically flawless spinal blocks with a standard local anesthetic and felt nothing change — no numbness, no weakness, no block of any kind. The only unusual feature linking them was a wasp sting in the months before surgery.

The first patient was a 42-year-old man, classified as ASA I, meaning a completely healthy individual with no systemic disease, scheduled for an inguinal hernia repair. Six months earlier he had been stung on the forearm by a wasp. An experienced anesthesiologist performed spinal anesthesia at the L3–L4 interspace of the lumbar spine using a 25-gauge Quincke needle, the workhorse of neuraxial techniques. Free and continuous flow of cerebrospinal fluid confirmed that the needle tip sat correctly within the thecal sac, the membrane-enclosed space containing the fluid that bathes the spinal cord and nerve roots. The team then injected 3 milliliters of 0.5 percent hyperbaric bupivacaine — a total of 15 milligrams — a dose routinely sufficient for lower abdominal surgery. The injection met no resistance, and cerebrospinal fluid continued to flow throughout, ruling out displacement of the needle. Barbotage, the repeated aspiration and reinjection sometimes used to confirm placement, was not performed.

Ten minutes later, the patient should have been profoundly anesthetized. Instead, pinprick and cold sensation testing demonstrated no sensory blockade at any dermatome level, and the modified Bromage scale, the standard measure of lower-limb motor block, remained at Grade 0, indicating full strength and movement in both legs. The team repeated the procedure at a different interspace, L2–L3, using the same technique and the same anesthetic solution. The result was identical: no sensory change, no motor weakness, nothing. With two failed attempts and no explanation, the clinicians converted to general anesthesia, which proceeded uneventfully. Postoperative evaluation, including allergy testing, was entirely normal, and no technical error could be identified on review.

The second case followed a strikingly similar script. A 35-year-old healthy man, also ASA I, presented for knee arthroscopy. Five months before surgery he had been stung on the chest by a wasp. Spinal anesthesia was again performed at L3–L4 with a 25-gauge Quincke needle, and free cerebrospinal fluid flow was confirmed before the injection of 2.5 milliliters of 0.5 percent hyperbaric bupivacaine, equivalent to 12.5 milligrams. The injection was smooth, with continuous fluid return confirming correct needle positioning throughout. After ten minutes the patient retained full sensory and motor function. A second attempt at L2–L3 with the same drug and technique again produced no blockade whatsoever. Pinprick and cold testing showed no reduction in sensation at any level, and the Bromage score stayed at Grade 0. He too was converted to general anesthesia and recovered without complications.

The authors of the report, led by Ammir Abuzahra and colleagues, emphasize that the pattern shared by these two cases is what makes them remarkable. Typical causes of failed spinal anesthesia — needle misplacement, inadequate dosing, obesity, spinal pathology — were absent in both patients. Both blocks were performed by experienced anesthesiologists with correct technique and appropriate drug doses, and both patients were fully cooperative. Under ideal conditions, the incidence of total spinal anesthetic failure is very low. The complete absence of both sensory and motor blockade, rather than a patchy or insufficient block, suggested that something fundamental had prevented the local anesthetic from acting on neural tissue at all. The decision to repeat the block with the same agent reflected standard clinical practice, since a first failure can usually be attributed to subtle technical error, but the repeated negative result, combined with the normal appearance of cerebrospinal fluid in every pass, made a purely technical explanation unlikely.

The hypothesis the authors put forward is provocative: that prior wasp envenomation may have altered the patients’ neuronal responsiveness to spinal local anesthetics. They are careful to label this as speculative, and with only two cases no causal inference is possible. But there is genuine biological plausibility buried in wasp venom chemistry. Wasp venoms contain multiple biologically active peptides, among them the pompilidotoxins, a class of neurotoxins that act directly on voltage-gated sodium channels — the same molecular gates that bupivacaine blocks to produce anesthesia. Experimental studies have shown that alpha-pompilidotoxin slows the inactivation of sodium currents, prolonging the influx of sodium ions into neurons and thereby changing how nerve cells fire. Because bupivacaine exerts its anesthetic effect principally by plugging these very channels, an interaction between venom-induced channel changes and the drug’s mechanism is, at least in theory, conceivable.

A second possible mechanism involves inflammation. Wasp venom also contains mastoparan peptides, which can activate mast cells and trigger the release of histamine, as demonstrated in experimental cell models. In theory, inflammatory mediators could alter neural excitability or the responsiveness of nerve membranes to local anesthetics. Delayed immune-mediated neurologic complications after wasp stings have been described in the medical literature, showing that venom effects are not always confined to the minutes after the sting. However, the authors note that no published evidence currently establishes sustained inflammatory changes within the neuraxis — the spinal canal and its contents — after a remote sting, and neither patient underwent biomarker testing or neurophysiological studies that might have detected such changes. The mechanism remains an open question rather than a demonstrated pathway.

The report builds on an earlier and equally curious observation. A case-control study published in the Indian Journal of Anaesthesia by Panditrao and colleagues reported delayed or incomplete spinal blockade with intrathecal bupivacaine among patients with histories of scorpion stings, and proposed venom-related alterations in anesthetic responsiveness as a possible explanation. The new wasp cases echo that finding across a different venomous species, though the authors stress that the scorpion study does not establish that the same phenomenon occurs after wasp stings. Reduced effectiveness of local anesthetics has also been reported in some patients with connective tissue disorders such as Ehlers–Danlos syndrome Type III, indicating that altered anesthetic responsiveness, while poorly understood, is not without precedent. Neither of the current patients had any connective tissue disorder, and both had normal postoperative allergy testing.

The limitations of the report are considerable, and the authors lay them out candidly. Two cases might be coincidental; many people are stung by wasps every year and receive spinal anesthesia without any difficulty. The temporal pattern — failure occurring months after the sting — argues against an acute allergic reaction, since neither patient showed any perioperative allergic signs, but it also means any lasting change would have to persist far longer than venom components themselves remain in the body. The team lacked laboratory evidence such as inflammatory biomarker measurements, serum antibody testing, or nerve-excitability studies that could have supported a venom-related mechanism. Neither patient developed signs of local anesthetic systemic toxicity, though that does not independently exclude problems related to drug preparation, storage, or distribution. Subtle differences in technique or interspace level cannot be entirely excluded, but the repeated failure at two different spinal levels makes a technical cause improbable.

For now, the authors present these observations as hypothesis-generating rather than practice-changing. No anesthesiologist should refuse a spinal block to a patient with an old wasp sting on the basis of two case reports. But the known neuroactive properties of wasp venom — sodium-channel modification by pompilidotoxins and mast-cell activation by mastoparan — provide enough biological plausibility to justify closer attention. The authors call for larger observational studies, pharmacological testing, and mechanistic investigations before any clinical relationship can be established, along with additional case reports from other centers. If the association holds up, it would suggest that a sting’s effects can echo through the nervous system in ways nobody expected, and that the humble wasp still holds chemical secrets relevant to the operating room. Until then, the two men who lay awake and unnumbed on their operating tables remain a medical mystery — and a reminder that even the most routine procedures in medicine can occasionally defy every textbook expectation.

Subject of Research: Spinal anesthesia failure following wasp envenomation

Article Title: Spinal Anesthesia Failure Following Wasp Envenomation: A Case Series of Two Patients

Article References: Abuzahra, A., Maraqah, M., Atawneh, S., Qawasmi, R., Rabaee, M., Sweity, S., Ewidat, O., Riyad, N., & Mujahed, A. (2026). Spinal Anesthesia Failure Following Wasp Envenomation: A Case Series of Two Patients. Clinical Case Reports, 14(10), Article e73637. https://doi.org/10.1002/ccr3.73637

Image Credits: AI Generated

DOI: 10.1002/ccr3.73637

Keywords: spinal anesthesia, wasp venom, bupivacaine, pompilidotoxin, mastoparan, voltage-gated sodium channels, anesthesia failure, envenomation, neurotoxicity, case series, local anesthetics, mast cells