Inadvertent Epidural Injection of Cefazolin in a Dog

ABSTRACT

Objective

To report a case of inadvertent epidural injection of cefazolin in a dog.

Case Summary

A 5‐year‐old neutered male mixed‐breed dog weighing 37.2 kg was presented to The Ohio State University Veterinary Medical Center's emergency room after the inadvertent epidural administration of cefazolin. The dog was referred from a primary care veterinarian, where it was being prepared for routine lateral suture cranial cruciate ligament repair. After premedication and induction, 800 mg of cefazolin (volume 8 mL) was inadvertently administered into the epidural space. Recovery from anesthesia was uneventful, with the dog showing no immediate adverse effects or seizure activity. The dog's vitals remained stable until transfer to the tertiary facility, where it exhibited signs of residual sedation that resolved appropriately over time with naloxone. The dog was monitored overnight and discharged the next day without complications observed.

New or Unique Information Provided

Recognizing that drug and communication errors are the most common errors in medicine is a critical first step toward implementing interventions aimed at enhancing patient safety and outcomes. Although inadvertent caudal epidural injections of cefazolin have been documented in people, this case appears to be the first report in veterinary medicine.

Abbreviations

LRS

lactated Ringer's solution

RCA

root cause analysis

1. Introduction

Developing a culture of safety and awareness when reporting medical errors is fundamental for preventing future incidents and enhancing patient safety and outcomes in veterinary medicine [1]. A medication error is a failure in the treatment process that could result in harm to the patient [2]. The term “failure” signifies a process that has not met an achievable standard, while “treatment process” encompasses the steps involved in medication management, such as prescribing, dispensing, preparation, administration, documentation, and monitoring. Drug‐related errors represent the most common type of medical errors reported in both human and veterinary hospitals [1, 3]. In an effort to reduce the frequency of these errors, the importance of adhering to the “seven rights” of medication administration, the right patient, right drug, right time, right dose, right route, right reason, and right documentation, has been emphasized [4]. These principles serve as a foundation for safe medication practices and are especially critical in high‐risk environments, such as anesthesia and critical care. Although inadvertent epidural injection of drugs intended for IV use is well‐documented in the human literature, it is still considered an underreported source of medical error that is likely seen in veterinary medicine [5, 6].

Cefazolin, a first‐generation cephalosporin antimicrobial, is commonly used in both human and veterinary medicine. There are reports of epidural administration of cefazolin in people with no immediate or delayed neurologic or hemodynamic complications [5, 7, 8]. To date, there appear to be no reports of epidural administration of cefazolin in dogs. The current report is the first case description of inadvertent administration of cefazolin into the epidural space in a dog.

2. Case Summary

A 5‐year‐old neutered male mixed‐breed dog weighing 37.2 kg initially presented to the primary care veterinarian for routine lateral suture cranial cruciate ligament repair. As premedication, the dog was administered 5 mg of hydromorphone¹ (IM) and 1 mg of acepromazine² (IM). Anesthesia was induced with 140 mg of IV propofol.³ IV fluid therapy (lactated Ringer's solution⁴ [LRS]) was administered at 175 mL/h. During preparation for the surgical procedure, the dog was intended to receive a lumbosacral epidural injection of 3.5 mg of hydromorphone and 20 mg of bupivacaine. The site was aseptically prepared, and a 22‐gauge spinal needle was inserted caudal to the L7 spinous process. The technician performing the procedure asked for the epidural syringe and was handed cefazolin rather than the hydromorphone and bupivacaine mixture. The syringes were labeled correctly; however, the assisting technician was a less experienced individual who was not familiar with the procedure, and the primary technician did not confirm the label before the injection. Thus, 800 mg of cefazolin⁵ was accidentally administered into the epidural space at the lumbosacral junction. The error was noticed immediately after administration of the drug. It was elected to forgo the planned epidural administration of hydromorphone and bupivacaine as well as the surgical procedure. Upon consultation with a veterinary anesthesiologist, the decision was made to recover the dog from general anesthesia and monitor for clinical signs.

The dog was weaned from inhalant anesthesia, and recovery was uneventful. Carprofen⁶ (75 mg) was administered subcutaneously. During the recovery period, the dog's heart rate was stable at 60–72/min, and its respiratory rate was 16–20/min. The rectal temperature was 36.2°C (97.2°F), and the systolic blood pressure measured by Doppler was 140 mm Hg. IV LRS was decreased to 100 mL/h once the dog was extubated. No seizure activity or neurologic abnormalities were noted, and vital signs remained stable before transport to our tertiary care facility.

After recovering from general anesthesia at the referring veterinarian, the dog was presented to The Ohio State University Veterinary Medical Center. Approximately 5 h had passed since inadvertent epidural administration of cefazolin. Upon initial examination, the dog exhibited hypothermia (34.9°C [94.9°F]) in addition to sinus bradycardia (80/min) on auscultation and on ECG. The dog was sedate but rousable with auditory stimulation, becoming ambulatory with weight support. The dog's neurologic status was difficult to assess, which was attributed to the lingering effects of anesthetic drugs. No significant abnormalities were noted other than sedated mentation.

Naloxone⁷ (1.4 mg, IV) was administered, and the hypothermia and bradycardia resolved over the next hour. A repeat neurologic examination performed 6.5 h after epidural administration of cefazolin was unremarkable, and the dog was admitted for overnight observation, focusing on hourly seizure watches and abbreviated neurologic examinations, given concerns for delayed adverse effects. While hospitalized, the dog received IV PlasmaLyte⁸ (80 mL/h [50 mL/kg/day]). The dog remained comfortable, with no signs of pain or disorientation. The dog was monitored for neurologic abnormalities, including seizures, and none were noted during its hospitalization. The next day, physical examination findings were normal other than mild lameness from historical cranial cruciate ligament insufficiency. The patient was deemed stable for discharge. The dog was closely monitored until discharge from the hospital, and no neurologic complications were observed. At 18‐month follow‐up, no delayed sequelae were reported by the owner. The dog has not received another epidural injection and did not return for cranial cruciate ligament repair.

3. Discussion

This report describes the inadvertent epidural administration of cefazolin in a dog during preparation for a routine surgical procedure. Despite potential risks, the dog did not exhibit complications and recovered uneventfully.

Causes for medication errors are well‐documented in human hospitals and are noted at increased frequencies in anesthesia and critical care settings [1, 3, 5, 9]. It has also been demonstrated that medical errors occur frequently in veterinary hospitals, but data for analysis are limited [1, 3]. There are many types of medical errors that can occur in a hospital setting, the severity of which ranges from harmless to fatal. For the purpose of this case study, our focus is on drug administration errors, which involve the administration of the wrong drug, wrong dose, or administration by the wrong route [1].

Documentation of medication administration errors in veterinary medicine is minimally discussed, so little is known about the nature and frequency of these errors [1, 3]. One voluntary study investigated the type and severity of errors in three veterinary hospitals, concluding that drug and communication errors were the most frequently reported types of error [1]. Most errors in the study did not result in harm (45%), similar to the dog in our report; however, 15% of incidents did result in patient harm.

Epidural analgesic administration is an effective technique for managing pain, but it is not exempt from risks, including inadvertent administration of nonepidural drugs, such as the cefazolin reported in the current case. Epidural analgesics are commonly used to provide effective regional pain control and reduce systemic anesthetic requirements during surgical procedures. However, this route of drug administration carries an inherently higher risk of severe complications, including neurologic injury and cardiorespiratory compromise, particularly when medication errors or iatrogenic trauma occur [9]. In addition to the inadvertent administration of drugs by the epidural route, epidural medication inadvertently administered through IV catheters has been documented and poses another risk [9]. Interestingly, an evaluation of errors in veterinary medicine found that anesthesia accounted for only 2% of reported events [3].

Drug characteristics that have been suggested to contribute to the adverse effects of accidental epidural injections are receptor‐specific toxicity, osmolality, the presence of preservative, and pH [7]. The osmolality of the standard diluted cefazolin solution (100 mg/mL) is 290 mOsmol/kg, which is relatively iso‐osmolar and would not be expected to cause significant damage. Similarly, higher pH solutions (>7.0) are more rapidly absorbed. The pH of cefazolin is 4.0–6.0, depending on reconstitution. The drug is water soluble and would be expected to be more slowly absorbed than lipid‐soluble drugs [10]. The peak concentration of cefazolin in dogs after IM administration is 30–90 min, with an elimination half‐life of 45–70 min [11]. Although the rate of metabolism from the epidural space would be expected to be different compared with that after IM administration, it is possible that the cefazolin had been cleared from the dog's circulation by the time of presentation and administration of naloxone.

A similar case in people reported a woman who received 1 g of ampicillin for labor analgesia through the epidural catheter, with no hemodynamic or neurologic changes [12]. In reports of people given high dosages of cefazolin epidurally with intrathecal leakage, neurologic signs were noted within 10 min and lasted for 6 h, with a protracted recovery over 3 months [13]. Although the dog in this case did not suffer any apparent complications after inadvertent epidural administration of cefazolin, there are still associated risks, especially if it is accidentally administered intrathecally by way of an incidental dural puncture [13]. Cefazolin is a strong epileptogenic agent, and this complication has been previously documented in the human literature and in a dog [14]. There are also reports of intrathecal administration of cefazolin in people and dogs that were associated with the onset of status epilepticus [13, 15, 16]. Two human patients undergoing spinal epidural adhesiolysis developed status epilepticus caused by intrathecal leakage of cefazolin occurring through an incidental dural puncture during administration [13]. That publication hypothesizes that the severity and rapidity of the seizures may have been related to the intrathecal concentration of cefazolin.

Most notably, in the current case report, the patient did not experience overt seizures or neurologic deficits, which is consistent with reports of inadvertent epidural cefazolin administration in people. Compared with the existing case report of seizures after intrathecal cefazolin administration in a dog, the greatest difference to consider is the route of administration. The finding of increased risk in intrathecal, rather than epidural, administration of cefazolin in dogs is consistent with reports in people.

The identification of a medical error should prompt a discussion of next steps: an investigation to find the root cause(s), and correct or implement systems to prevent recurrence. Although syringe misidentification was the immediate cause of error in the current report, a thorough root cause analysis (RCA) highlighted several potential underlying systemic factors. Used widely in both human and veterinary medicine to systematically identify factors contributing to errors, RCA focuses on systemic vulnerabilities rather than individual blame and creates targeted interventions to prevent recurrence [17, 18]. Both active failures (mistakes made by individuals directly involved) and latent conditions (systemic or organizational weaknesses) that independently and collectively increase the risk of errors are evaluated. It is important to review the entire process stepwise, as jumping to the most obvious cause may result in misidentification of the true root cause or combination of causes.

A primary contributor to the medical error in the current case appears to be a gap in verification protocols. Inadequate labeling or inconsistent verification, especially under high‐stress conditions, can result in syringe misidentification. Research emphasizes that standardized double‐check systems, in which a second individual verifies the drug and dosage before administration, can significantly reduce the risk of errors, particularly in high‐risk procedures [19, 20]. In this case, a formal double‐check protocol may not have been consistently applied, underscoring the need for reinforced verification protocols, especially when handling medications for procedures with increased risks, such as epidural administration.

The hospital environment also plays a crucial role in error prevention. Environmental distractions such as background noise, conversations, or simultaneous tasks can reduce staff focus and increase the risk of errors during critical tasks such as medication preparation and handoffs. Studies have shown that distractions and multitasking are linked to increased rates and severity of medication errors [21, 22]. In a busy hospital setting, technicians may feel pressured to complete multiple tasks quickly, leading to rushed or incomplete verification. Errors such as these can be reduced by implementing policies to minimize environmental distractions, especially in procedural areas, and fostering a workplace culture that values undivided attention for high‐risk tasks.

The involvement of a less experienced individual in the current case underscores the importance of thorough training and familiarity with hospital protocols for all staff involved. Studies have shown that structured training programs, particularly when combined with mentorship for newer or less experienced staff, can enhance accuracy and confidence in performing high‐risk tasks [23, 24, 25, 26]. In the current case, the assisting staff's limited experience with epidural procedures or medication handling may have reduced their ability to identify or question the error. Ensuring that the entire medical team receives comprehensive training in high‐risk protocols and is provided mentorship during complex procedures can help mitigate such risks and reinforce procedural accuracy.

The physical layout of medication storage areas also contributes to the risk of medication errors. If syringes containing different drugs intended for various administration routes (e.g., intravenous vs. epidural) are stored in close proximity, there is an increased likelihood of selecting the wrong syringe, especially if they appear similar in size, volume, color, or labeling. Optimizing the organization of medication storage areas, such as by segregating drugs based on administration route and using color‐coded labels, can significantly reduce the risk of misidentification [20, 21, 27, 28].

Effective communication, particularly during medication administration, is essential for error prevention. Closed‐loop communication, in which instructions or details are repeated back to confirm understanding, has been shown to reduce the risk of miscommunication in healthcare settings [29, 30]. In the current study, without verbal or visual confirmation, assumptions may have been made about the syringe's contents. Implementing closed‐loop communication protocols, which require staff to confirm critical information verbally before medication administration, can help prevent similar errors by ensuring that any miscommunication or assumption is clarified before a medication can be given.

Epidural administration is an inherently high‐risk procedure that warrants additional safety measures. In human health care, standardized checklists for high‐risk procedures, such as epidural injections or surgeries, have been shown to improve procedural safety by ensuring that all necessary steps, including medication verification, are consistently followed [31]. In this study, use of a checklist including the steps for medication verification and confirmation of syringe content might have prompted a secondary check before administration and potentially prevented the error.

Conducting an RCA after errors occur is essential for addressing both active errors (direct mistakes) and latent conditions (systemic issues) that may have contributed to the error. RCA can uncover both individual and systemic factors, such as cognitive limitations, environmental distractions, and workflow design, that, without structured analysis, might not be apparent [3, 17, 32]. In the current study, factors such as procedural distractions, training gaps, and suboptimal medication layout could be identified with RCA and result in targeted improvements. Effective solutions could include implementing strict double‐check protocols, reinforcing closed‐loop communication standards, reducing distractions in high‐risk areas, and providing enhanced training and mentorship for new employees involved in critical procedures.

Errors in veterinary practice often arise from a combination of cognitive and systemic factors, as illustrated by the current case. As described by Oxtoby et al., these errors reflect an interplay between individual cognitive constraints and environmental influences, consistent with Reason's Swiss cheese model, in which multiple smaller failures align to create conditions for a significant error [3, 17, 32]. By adopting a layered approach to error prevention that encompasses training, environmental controls, communication protocols, and systematic safeguards, veterinary teams can address both the immediate and underlying contributors to errors.

Veterinary practice, however, presents unique challenges, such as client‐driven constraints and animal‐specific considerations, necessitating human healthcare safety protocols to be adapted to the veterinary context [33, 34]. An unfortunate potential long‐term consequence of medical errors in veterinary medicine is the loss of client trust and the resulting hesitancy of owners to pursue further medical care for their pets in the future. Implementing RCA and the commitment to system improvements can ultimately enhance patient safety and reduce the likelihood of similar errors in the future.

Author Contributions

Jessie Warhoe: data curation, investigation, writing – original draft, writing – review and editing. Jiwoong Her: conceptualization, data curation, investigation, methodology, project administration, resources, supervision, writing – original draft, writing – review and editing. Turi Aarnes: conceptualization, investigation, project administration, writing – review and editing.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Conflicts of Interest

The authors declare no conflicts of interest.