Iatrogenic magnesium overdose: 2 case reports

Survival in canine tetanus - retrospective analysis of 42 cases (2006-2020)

Objective

To define factors associated with survival in dogs with tetanus and to evaluate the prognostic significance of an established severity classification scheme.

Methods

Medical records of dogs with the clinical diagnosis of tetanus were retrospectively reviewed with regard to signalment, clinical signs, clinicopathological findings on admission, wound characteristics, complications, therapeutic measures, and survival to discharge. Based on the extracted data, dogs were graded according to a previously published 4-class severity scheme. Non-parametric tests were applied for comparisons between survival categories.

Results

Forty-two dogs fulfilled inclusion criteria, of which 32 survived. Of 10 non-survivors, 4 died and 6 were euthanised. Non-survivors were more often younger than 2 years of age (6/10 vs. 7/32 dogs, p = 0.023), had shorter duration of specific signs of tetanus (time from onset of typical signs to presentation) (2 vs. 4 days, p = 0.016), were prescribed less often antibiotics prior to presentation (p = 0.006), had higher tetanus severity grade (10/12 dogs in Class III or IV died, p < 0.001), more often received acepromazine (p = 0.009) and atropine (p = 0.012), and more often had hyperthermia (p = 0.005) and respiratory complications (pneumonia, laryngeal spasm; p = 0.008). Wound characteristics, the use of tube feeding, metronidazole, methocarbamol, magnesium and antitoxin were not significantly different between non-survivors and survivors.

Clinical significance and conclusion

Young dogs with a rapid course of severe generalized tetanus have a guarded prognosis. The previously described severity classification scheme proved valuable in predicting survival. Prospective multi-center studies are needed to clarify the prognostic significance of age, sedative usage and modified versions of an established classification scheme, including the presence of respiratory complications.

Preliminary evaluation of the efficacy of intravenous magnesium sulfate for the treatment of ventricular arrhythmias in 16 dogs

OBJECTIVE

To evaluate the efficacy of IV magnesium sulfate in decreasing the number of ventricular ectopic beats or convert ventricular tachyarrhythmia to sinus rhythm in dogs.

DESIGN

Prospective, observational feasibility study.

SETTING

Private referral center.

ANIMALS

Sixteen client-owned dogs exhibiting 1 or more of the following: (1) sustained or paroxysmal ventricular tachycardia (heart rate > 180/min), (2) single or multiform ventricular complexes at > 60 ectopies/min.

INTERVENTIONS

Pretreatment (T1) blood creatinine and electrolyte concentrations were measured. A 60-second lead II ECG strip and systolic arterial blood pressure (SABP) were recorded. Magnesium sulfate 0.1 mmol/kg (0.2 mEq/kg) was administered IV over 5 minutes. Five minutes after completion of the magnesium sulfate injection (T2), electrolyte concentrations were measured again. A second 60-second lead II ECG strip and SABP were recorded. The number of ectopic ventricular and supraventricular beats (sinus beats) that occurred in 60 seconds during the T1 and T2 ECG recordings was compared. T1 and T2 electrolytes and SABP were also compared.

RESULTS

There was an increase in the ionized magnesium concentration, a decrease in the heart rate and the number of ventricular ectopic beats, and an increase in the number of supraventricular beats at T2. Two dogs converted to a sinus rhythm at T2 that was not sustained.

CONCLUSIONS

Intravenous administration of 0.1 mmol/kg (0.2 mEq/kg) magnesium sulfate in dogs with ventricular ectopy decreased the number of ventricular beats and heart rate. However, a specific conclusion regarding the use of magnesium sulfate as a first-line therapy for dogs with ventricular tachyarrhythmias at the investigated dose cannot be made.

Tetanus in Animals — Summary of Knowledge

Tetanus is a neurologic non-transmissible disease (often fatal) of humans and other animals with a worldwide occurrence. Clostridium tetani is the spore producing bacillus which causes the bacterial disease. In deep penetrating wounds the spores germinate and produce a toxin called tetanospasmin. The main characteristic sign of tetanus is a spastic paralysis. A diagnosis is usually based on the clinical signs because the detection in the wound and the cultivation of C. tetani is very difficult. Between animal species there is considerable variability in the susceptibility to the bacillus. The most sensitive animal species to the neurotoxin are horses. Sheep and cattle are less sensitive and tetanus in these animal species are less common. Tetanus in cats and dogs are rare and dogs are less sensitive than cats. Clinically two forms of tetanus have been recognized, i. e. localized and generalized. The available treatment is not specific because the toxin in neuronal cells cannot be accessed by antitoxin antibodies. The aim of the therapy is to: neutralise the unbound neurotoxin, inhibit C. tetani growth in the wound, and provide supportive care to mitigate the effects of the neurotoxin. The treatment is difficult with an unclear prognosis.

Retrospective analysis of iatrogenic diseases in cattle requiring admission to a veterinary hospital

Iatrogenic diseases in veterinary medicine are often related to malpractice or lack of skill. For this retrospective study, 4262 clinical records of cattle admitted to the veterinary teaching hospital of the University of Milan between 2005 and 2017 were analysed, and 121 cases (2.8 per cent), referred for an iatrogenic-related disease, were selected. The findings showed that iatrogenic diseases were more often caused by farmers (92.6per cent) than by bovine practitioners (7.4 per cent). Iatrogenic diseases were caused mainly by the improper administration of drugs (43.0 per cent), forced extraction during calving (19.8 per cent), forced milk or colostrum feeding, which was often performed by awkward administration using a nipple bottle (14.9 per cent) or by oral oesophageal tubing (15.7 per cent). Moreover, farmers often performed medical, nursing and zootechnical procedures without adequate training. The role of the practitioner is fundamental in farmer education. Clinicians, especially in some professional branches such as neonatology, should not delegate medical procedures to untrained farmers. Effective tutoring and good communication with farmers play a key role in dairy herd health and consequently in public health. This then can lead to a decrease in improper drug administration, the prevention of antibiotic resistance and the reduction of treatment costs.

Magnesium physiology and clinical therapy in veterinary critical care

OBJECTIVE

To review magnesium physiology including absorption, excretion, and function within the body, causes of magnesium abnormalities, and the current applications of magnesium monitoring and therapy in people and animals.

ETIOLOGY

Magnesium plays a pivotal role in energy production and specific functions in every cell in the body. Disorders of magnesium can be correlated with severity of disease, length of hospital stay, and recovery of the septic patient. Hypermagnesemia is seen infrequently in people and animals with significant consequences reported. Hypomagnesemia is more common in critically ill people and animals, and can be associated with platelet, immune system, neurological, and cardiovascular dysfunction as well as alterations in insulin responsiveness and electrolyte imbalance.

DIAGNOSIS

Measurement of serum ionized magnesium in critically or chronically ill veterinary patients is practical and provides information necessary for stabilization and treatment. Tissue magnesium concentrations may be assessed using nuclear magnetic resonance spectroscopy as well as through the application of fluorescent dye techniques.

THERAPY

Magnesium infusions may play a therapeutic role in reperfusion injury, myocardial ischemia, cerebral infarcts, systemic inflammatory response syndromes, tetanus, digitalis toxicity, bronchospasms, hypercoagulable states, and as an adjunct to specific anesthetic or analgesic protocols. Further veterinary studies are needed to establish the frequency and importance of magnesium disorders in animals and the potential benefit of magnesium infusions as a therapeutic adjunct to specific diseases.

PROGNOSIS

The prognosis for most patients with magnesium disorders is variable and largely dependent on the underlying cause of the disorder.

Magnesium sulfate as an adjunct therapy in the management of severe generalized tetanus in a dog

OBJECTIVE

To describe the use of magnesium sulfate in a case of generalized tetanus in a dog.

CASE SUMMARY

A 1.5-year-old golden retriever was presented for a digital wound on the right thoracic limb and clinical signs associated with generalized tetanus. Initial case management consisted of wound debridement, treatment with metronidazole, tetanus immunoglobulin, methocarbamol, airway management via tracheostomy, and nursing care. Sedation to control severe muscle spasms became insufficient despite increasing doses of benzodiazepine, methocarbamol, and barbiturate continuous rate infusions. A magnesium sulfate continuous rate infusion was instituted on day 7 and muscle rigidity improved within 16 hours allowing discontinuation of sedative infusions over the subsequent 2 days. Clinical improvement continued and the dog was discharged on day 14.

NEW OR UNIQUE INFORMATION PROVIDED

This case demonstrates the use of supraphysiologic magnesium in the treatment of severe generalized tetanus with a positive outcome. No clinical signs associated with magnesium toxicity were noted during the course of therapy. Magnesium sulfate should be considered as a potential adjunct therapy in the management of spastic paralysis caused by severe tetanus in dogs.

Thiopental and halothane dose-sparing effects of magnesium sulphate in dogs

OBJECTIVE

To evaluate the effect of pre- and intraoperatively administered magnesium sulphate (MgSO(4)) on the induction dose of thiopental and of halothane for maintenance of anaesthesia in dogs undergoing ovariohysterectomy (OHE).

STUDY DESIGN

Prospective, double-blind, randomized, placebo-controlled study.

ANIMALS

Forty-six healthy, ASA physical status 1 dogs, scheduled for elective OHE.

METHODS

The dogs were randomly assigned to receive a bolus of 50 mg kg(-1) MgSO(4) intravenously (IV), just before induction of anaesthesia, followed by a constant rate infusion (CRI) of 12 mg kg(-1) hour(-1) MgSO(4) intraoperatively (group Mg, n = 27) or a placebo bolus and CRI of 0.9% sodium chloride (NaCl) (group C, n = 19), approximately 30 minutes after premedication with acepromazine (0.05 mg kg(-1), intramuscularly, IM) and carprofen (4 mg kg(-1), subcutaneously, SC). Anaesthesia was induced with thiopental administered to effect and maintained with halothane in oxygen. End-tidal halothane (ET(hal)) was adjusted to achieve adequate depth of anaesthesia. Blood samples were obtained pre- and postoperatively for measurement of total serum magnesium concentration.

RESULTS

The mean dose of thiopental was statistically lower (p < 0.0005) and the mean standardized ET(hal) concentration and end-tidal carbon dioxide partial pressure (Pe'CO(2)) areas under the curve were statistically smaller (p < 0.0005 and 0.014 respectively) in group Mg. Postoperatively the mean total serum magnesium concentration was statistically higher than the preoperative value (p < 0.0005) in group Mg, but not in group C. Nausea, associated with the MgSO(4) bolus injection, was observed in six dogs in group Mg, two of which vomited prior to induction of anaesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Magnesium sulphate administration reduced the induction dose of thiopental and ET(hal) concentration for maintenance of anaesthesia in dogs undergoing OHE. Observed side effects were nausea and vomiting.