Intrathecal morphine overdose in a dog

Melatonin and morphine: potential beneficial effects of co-use

Morphine is a potent analgesic agent used to control acute or chronic pain. Chronic administration of morphine results in analgesic tolerance, hyperalgesia, and other side effects including dependence, addiction, respiratory depression, and constipation, which limit its clinical usage. Therefore, identifying the new analgesics with fewer side effects which could increase the effect of morphine and reduce its side effects is crucial. Melatonin, a multifunctional molecule produced in the body, is known to play an important role in pain regulation. The strong anti-inflammatory effect of melatonin is suggested to be involved in the attenuation of the pain associated with inflammation. Melatonin also increases the anti-nociceptive actions of opioids, such as morphine, and reverses their tolerance through regulating several cellular signaling pathways. In this review, published articles evaluating the effect of the co-consumption of melatonin and morphine in different conditions were investigated. Our results show that melatonin has pain-killing properties when administered alone or in combination with other anti-nociceptive drugs. Melatonin decreases morphine consumption in different pathologies. Furthermore, attenuation of morphine intake can be accompanied by reduction of morphine-associated side-effects, including physical dependence, morphine tolerance, and morphine-related hyperalgesia. Therefore, it is reasonable to believe that the combination of melatonin with morphine could reduce morphine-induced tolerance and hyperalgesia, which may result from anti-inflammatory and antioxidant properties of melatonin. Overall, we underscore that, to further ameliorate patients' life quality and control their pain in various pathological conditions, melatonin deserves to be used with morphine by anesthesiologists in clinical practice.

An Update on Drugs Used for Lumbosacral Epidural Anesthesia and Analgesia in Dogs

This review aims to report an update on drugs administered into the epidural space for anesthesia and analgesia in dogs, describing their potential advantages and disadvantages in the clinical setting. Databases searched include Pubmed, Google scholar, and CAB abstracts. Benefits of administering local anesthetics, opioids, and alpha₂ agonists into the epidural space include the use of lower doses of general anesthetics (anesthetic “sparing” effect), perioperative analgesia, and reduced side effects associated with systemic administration of drugs. However, the potential for cardiorespiratory compromise, neurotoxicity, and other adverse effects should be considered when using the epidural route of administration. When these variables are considered, the epidural technique is useful as a complementary method of anesthesia for preventive and postoperative analgesia and/or as part of a balanced anesthesia technique.

Postoperative Analgesia Provided by Liposomal Hydromorphone in Client-Owned Dogs Undergoing Limb Amputation

The analgesic efficacy of liposomal hydromorphone (LE-hydro) was tested in dogs undergoing limb amputation. The positive controls (n = 10) received subcutaneous (SQ) hydromorphone (0.2 mg/kg) and 1.5 mL of blank liposomes before surgery; fentanyl continuous rate infusion (CRI), 5-10 μg/kg/hr IV, during and for 24 hr after surgery; and a fentanyl patch at extubation. The negative controls (n = 7) received SQ hydromorphone (0.2 mg/kg) and 1.5 mLs of blank liposomes SQ before surgery, fentanyl CRI (5-10 μg/kg/hr IV) during surgery but stopped at extubation, and a fentanyl patch at extubation. The test group (n = 11) received 3 mg/kg of LE-hydro and 1.5 mL of saline SQ before surgery, 1.5 mL of saline SQ, and a saline CRI during surgery. All groups received a bupivacaine block in the limb prior to amputation and carprofen prior to surgery. Treatment failures, pain scores, opioid side effects, heart rate, respiratory rate, temperature, and client-reported pain and side effects were evaluated. There were three treatment failures in the positive control (3/10) and test groups (3/11). Negative controls had seven treatment failures (7/7). Side effects for all three groups were within expected limits. LE-hydro provides postoperative analgesia equivalent to fentanyl CRI in dogs undergoing limb amputation.

Possible delayed respiratory depression following intrathecal injection of morphine and bupivacaine in an alpaca

OBJECTIVE

To describe general anesthesia and successful treatment of an alpaca, which developed respiratory arrest 2 hours after intrathecal injection of morphine and bupivacaine.

CASE SUMMARY

A 10-day-old female alpaca weighing 7.3 kg was presented to our hospital with a fractured right tibia. The cria was anesthetized to repair the fracture with a dynamic compression plate. Anesthesia was induced with IV propofol and maintained with sevoflurane in 100% oxygen. Prior to the start of surgery the alpaca received an unintended intrathecal injection of 0.6 mL of a solution of 0.5 mg morphine (0.068 mg/kg) and 1.5 mg bupivacaine (0.2 mg/kg), after an attempted lumbo-sacral epidural. The alpaca developed respiratory arrest 120 minutes after the intrathecal injection was administered. Adequate hemoglobin-oxygen saturation was maintained despite minimal intermittent manual ventilation, but marked hypercapnia developed (PaCO2 of 17.3 KPa [130 mm Hg]). Delayed respiratory depression resulting from cephalad migration of intrathecal morphine was suspected. Ventilation was supported until the end of surgery when sevoflurane was discontinued. The trachea remained intubated, 100% oxygen was supplied, and ventilation was supported at 2-4 breaths/min for the next 60 minutes, but no attempts to breathe spontaneously were detected. Intravenous naloxone (0.3 mg [0.04 mg/kg]) was administered slowly to effect until adequate spontaneous ventilation and full consciousness returned. The anesthetic recovery of the alpaca was rapid and uneventful after the opioid antagonist was given.

NEW INFORMATION PROVIDED

Delayed respiratory depression is a potential complication after intrathecal administration of morphine. Careful dose-adjustment may reduce the risk, and close monitoring will result in early detection and treatment of this complication.

Reversible paralysis and loss of deep pain sensation after topical intrathecal morphine administration following durotomy

OBJECTIVE

To report 2 dogs that developed temporary pelvic limb paralysis with loss of deep pain sensation after topical intrathecal morphine administration during spinal surgery.

STUDY DESIGN

Clinical report.

ANIMALS

Dogs (n = 2).

METHODS

A 5-year-old castrated male French Bulldog with a subarachnoid diverticulum at T9-T10 and a 9.5-year-old castrated male Belgian Shepherd dog with a herniated disc at T12-T13 and intradural component, had Gelfoam soaked with morphine placed over the dura mater defect.

RESULTS

Pelvic limb paralysis and loss of deep pain sensation was noticed immediately after recovery from anesthesia. After intravenous naloxone administration, both dogs immediately regained ambulation and normal pain sensation; however the effect was temporary lasting only a few hours. Permanent resolution of clinical signs occurred 24 hours after surgery.

CONCLUSIONS

Topical intrathecal morphine administration resulted in temporary pelvic limb paralysis and loss of deep pain sensation. This route of administration should be used cautiously until further determination of the efficacy and adverse effects associated with topical intrathecal morphine administration.

Status epilepticus attributed to inadvertent intrathecal injection of cefazolin during myelography

OBJECTIVE

To describe a case of status epilepticus believed to be a consequence of inadvertent intrathecal administration of cefazolin in a dog undergoing a myelogram.

CASE SUMMARY

A 4-year-old, 6.5 kg, male neutered Dachshund was referred for evaluation of an acute onset hind limb paraparesis. While performing a lumbar myelogram, cefazolin was inadvertently injected into the ventral subarachnoid space. Subsequent refractory seizure activity was attributed to the epileptogenic effects of intrathecally administered cefazolin. Supportive therapy led to eventual complete recovery.

NEW OR UNIQUE INFORMATION PROVIDED

Although epileptogenic effects of intrathecally administered cefazolin are well documented in the human and experimental animal model literature, to the authors' knowledge this has not been characterized in the veterinary literature. This case highlights the need to be diligent and mindful when one administers medications, and describes the management of a dog adversely affected as a consequence of a medical error.

Effects of opium consumption on cardiometabolic diseases

Opium is the second-most-commonly abused substance (after tobacco) in developing countries of the Middle East region, and in many Asian nations. One of the reasons for the high prevalence of opium abuse in these countries is a traditional belief among Eastern people, even including some medical staff, that opium might have beneficial effects on cardiovascular health and in the control of diabetes mellitus, hypertension, and dyslipidaemia. In this Perspectives article, we summarize the current understanding of the pharmacotoxicology of opium and its specific effects on glycaemic control, blood pressure, lipid profile, and atherosclerosis. On the basis of the available evidence, we believe not only that opium has no ameliorating effect on cardiovascular diseases, but also that the use of this drug might have adverse effects on these conditions. Therefore, people should be educated about the hazardous effects of opium consumption on cardiometabolic diseases.

Unusual perianesthetic malignant hyperthermia in a dog

CASE DESCRIPTION

A 7-month-old male Siberian Husky affected by lower motor neuron tetraparesis was anesthetized for electrodiagnostic testing and collection of muscle and nerve biopsy specimens.

CLINICAL FINDINGS

Preanesthetic physical examination revealed a high rectal temperature, and serum biochemical analysis revealed high muscle and liver enzyme activities. The dog was anesthetized twice. The dog was anesthetized with isoflurane and developed moderate hypercarbia and mild hyperthermia. Injectable anesthetic agents were used to anesthetize the dog the second time, during which the dog developed severe malignant hyperthermia. A genetic test performed after anesthesia did not reveal a mutation of the RYR1 gene, the gene that mediates calcium-release channels in skeletal muscle. On the basis of clinical features, and because other neuromuscular disorders were ruled out, a genetic channelopathy involving the skeletal muscle ion channels was suspected.

TREATMENT AND OUTCOME

The dog was disconnected from the breathing system, and active cooling of the body was performed with ice packs applied to the body surface and alcohol applied to the foot pads. Cold crystalloid solutions were administered i.v.. Intermittent positive-pressure ventilation with 100% oxygen was performed to decrease end-tidal partial pressure of carbon dioxide. Because dantrolene was not available, acepromazine was administered to facilitate a decrease in body temperature. The dog recovered from malignant hyperthermia and was discharged to the owner after 13 days of hospitalization.

CLINICAL RELEVANCE

Dogs affected by genetic muscle disorders should be considered at risk for perianesthetic malignant hyperthermia, even in the absence of an RYR1 gene mutation.

Suspected acute meperidine toxicity in a dog

OBSERVATIONS

A 22-month-old male neutered Coton De Tulear dog was presented for upper gastrointestinal endoscopy under general anesthesia. The anesthetic plan included premedication with intramuscular meperidine (4 mg kg(-1)) but meperidine was inadvertently administered at ten-fold this dose. Within 5 minutes, the dog was unresponsive to external stimulation, and by 10 minutes post-injection developed generalized signs of central nervous system (CNS) excitement. Initial therapy included inspired oxygen supplementation, and single intravenous (IV) doses of diazepam (0.68 mg kg(-1)) and naloxone (0.03 mg kg(-1)) to no effect. A second dose of diazepam (0.46 mg kg(-1), IV) abolished most of the signs of CNS excitement. General anesthesia was induced and the endoscopy performed. Time to extubation was initially prolonged, but administering naloxone (final dose 0.1 mg kg(-1), IV) to effect enabled extubation. After naloxone, the dog became agitated, noise sensitive, and had leg and trunk muscle twitches. Diazepam (0.30 mg kg(-1), IV) abolished these signs and the dog became heavily sedated and laterally recumbent. Naloxone administration was continued as a constant rate infusion (0.02 mg kg(-1) hour(-1), IV) until approximately 280 minutes post-meperidine injection, at which time the dog suddenly sat up. Occasional twitches of the leg and trunk muscles were observed during the night. The dog was discharged the next day appearing clinically normal.

CONCLUSIONS

Given that the CNS excitatory effects of normeperidine are not a mu opioid receptor effect, the use of naloxone should be considered carefully when normeperidine excitotoxicity is suspected. Benzodiazepines may be beneficial in ameliorating clinical signs of normeperidine excitotoxicity.