The use of sevoflurane in a 2:1 mixture of nitrous oxide and oxygen for rapid mask induction of anaesthesia in the cat

The Influence of Anaesthetic Drugs on the Laryngeal Motion in Dogs: A Systematic Review

Simple Summary

Laryngeal paralysis is secondary to a loss of normal function of the larynx. Older dogs are particularly affected, with normal breathing becoming difficult. A successful diagnosis typically relies on the visualisation of either, complete, or partially absent, laryngeal movements. The use of anaesthesia drugs to provide sedation and stress relief is most commonly necessary during the diagnosis of laryngeal paralysis. While, the excessive administration of anaesthesia drugs may result in absent movements, the ideal anaesthesia regime remains unknown, and the use of sedation is questionable, given the potential for absent laryngeal movements, even in healthy dogs. In this systematic review, we found a potential benefit from using sedation during the evaluation of laryngeal function when compared to injectable anaesthetics only. The respiratory stimulant doxapram was effective in differentiating normal dogs from dogs with laryngeal paralysis but has associated safety hazards.

Abstract

Anaesthetic drugs are commonly used during the evaluation of laryngeal function in dogs. The aim of this review was to systematically analyse the literature describing the effects of anaesthetic drugs and doxapram on laryngeal motion in dogs and to determine which drug regime provides the best conditions for laryngeal examination. PubMed, Google Scholar, and EMBASE databases were used for the literature search up to November 2019. Relevant search terms included laryngeal motion, anaesthetic drugs and dogs. Studies were scored based on their level of evidence (LoE), according to the Oxford Centre for Evidence-based Medicine, and the quality was assessed using the risk-of-bias tool and SIGN-checklist. In healthy dogs, premedication before laryngeal examination provided better examination conditions and maintained overall adequate laryngeal motion in 83% of the studies. No difference in laryngeal motion between induction drugs was found in 73% of the studies but the effects in dogs with laryngeal paralysis remain largely unknown. Doxapram increased laryngeal motion in healthy dogs without serious side effects, but intubation was necessary for some dogs with laryngeal paralysis. Methodological characteristics varied considerably between studies, including the technique and timing of evaluation, number of assessors, study design, drug dose, combinations, route and speed of administration.

AAHA anesthesia guidelines for dogs and cats

Safe and effective anesthesia of dogs and cats rely on preanesthetic patient assessment and preparation. Patients should be premedicated with drugs that provide sedation and analgesia prior to anesthetic induction with drugs that allow endotracheal intubation. Maintenance is typically with a volatile anesthetic such as isoflurane or sevoflurane delivered via an endotracheal tube. In addition, local anesthetic nerve blocks; epidural administration of opioids; and constant rate infusions of lidocaine, ketamine, and opioids are useful to enhance analgesia. Cardiovascular, respiratory, and central nervous system functions are continuously monitored so that anesthetic depth can be modified as needed. Emergency drugs and equipment, as well as an action plan for their use, should be available throughout the perianesthetic period. Additionally, intravenous access and crystalloid or colloids are administered to maintain circulating blood volume. Someone trained in the detection of recovery abnormalities should monitor patients throughout recovery. Postoperatively attention is given to body temperature, level of sedation, and appropriate analgesia.

Feline blood transfusions: A pinker shade of pale

PRACTICAL RELEVANCE

blood transfusions are a potentially life-saving procedure that are within the reach of most small animal practitioners. Only minimal equipment is required.

PATIENT GROUP

any cat with clinical signs attributable to a reduced red blood cell mass that is affecting oxygen transport (as a result of reduced packed cell volume or acute blood loss) is a potential candidate for a transfusion.

CLINICAL CHALLENGES

although the principles of transfusion medicine are not complicated, there can be fatal consequences if certain steps are omitted.

DIAGNOSTICS

blood typing kits and blood filters are readily available from veterinary wholesalers, laboratories and blood banking services.

EVIDENCE BASE

over the past three decades, a substantial body of clinical research and reports has built up covering feline blood types and transfusion medicine. This article draws on that research to provide clinical guidance aimed at all veterinarians in feline or small animal practice who either currently practise transfusion medicine or plan to do so.

Determination of minimum alveolar concentration of sevoflurane in juvenile swine

Pigs are important animal models in veterinary and medical research and have been widely used in experiments requiring surgical anesthesia. Sevoflurane is an inhalant anesthetic with unique properties that make it an ideal anesthetic for mask induction and anesthesia maintenance. However, there are relatively few studies reporting the anesthetic requirements for sevoflurane in juvenile swine, an age group that is commonly used in research experiments. Therefore the objective of this study was to determine the Minimum Alveolar Concentration (MAC) for sevoflurane in juvenile swine. Sevoflurane anesthesia was induced in six Yorkshire-cross pigs of approximately 9 weeks-of-age and MAC for sevoflurane was determined. The sevoflurane MAC value was determined to be 3.5+/-0.1% which is notably higher than values reported in the literature for pigs. This discrepancy in MAC values may represent changes in anesthetic requirements between different age groups of pigs and differences in the type of stimulus used to determine MAC.

Vancomycin for multi-drug resistant Enterococcus faecium cholangiohepatitis in a cat

A 12-year-old, neutered male domestic shorthair cat was evaluated with a life-long history of intermittent, predominantly small bowel diarrhea and a 3 day history of hematochezia. At presentation, the cat had increased liver enzyme activities and an inflammatory leukogram. Histopathology demonstrated inflammatory bowel disease (IBD), cholangiohepatitis and pancreatitis. The cholangiohepatitis was associated with a multi-drug resistant Enterococcus faecium. Gallbladder agenesis was also documented. Treatment with vancomycin was safely instituted for 10 days. Clinical signs resolved, however, cure of the bacterial cholangiohepatitis was not achieved. The risk of vancomycin resistant enterococci (VRE) in human and veterinary medicine is discussed.

Clinical use of dexmedetomidine as premedicant in cats undergoing propofol-sevoflurane anaesthesia

The purpose of this report was to evaluate the cardiorespiratory effects and efficacy of dexmedetomidine as a premedicant agent in cats undergoing ovariohysterectomy anaesthetized with propofol-sevoflurane. Cats were randomly divided into two groups of eight animals each. Dexmedetomidine (0.01 mg/kg) or 0.9% saline was administered intravenously (D and S, respectively). After 5 min, propofol was administered intravenously and anaesthesia was maintained with sevoflurane. Heart and respiratory rates, arterial blood pressure, oxygen saturation, rectal temperature and the amount of propofol needed for induction were measured. Premedication with dexmedetomidine reduced the requirement of propofol (6.7+/-3.8 mg/kg), but induced bradycardia, compared with the administration of saline (15.1+/-5.1 mg/kg). Recovery quality was significantly better in D but no significant difference in time to return of swallowing reflex was observed between groups (D=2.5+/-0.5 min; S=3.2+/-1.8 min). In conclusion, dexmedetomidine is a safe and effective agent for premedication in cats undergoing propofol-sevoflurane anaesthesia with minimal adverse effects.

Therapy for Australian cats with lymphosarcoma

OBJECTIVE

To determine the response of Australian cats with lymphosarcoma to chemotherapy and/or surgery in relation to patient and tumour characteristics, haematological and serum biochemical values and retroviral status.

DESIGN

Prospective study of 61 client-owned cats with naturally-occurring lymphosarcoma subjected to multi-agent chemotherapy and/or surgery.

PROCEDURE

An accepted chemotherapy protocol utilising l-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate and prednisolone was modified and used to treat 60 cats with lymphosarcoma. Clinical findings were recorded before and during therapy. As far as practical, cases were followed to death, euthanasia or apparent cure. Owner satisfaction with the results of chemotherapy was determined using a questionnaire sent after the completion of chemotherapy.

RESULTS

One cat, with lymphosarcoma limited to a single mandibular lymph node, was treated using surgery alone and was cured. The other 60 cats were treated using multi-agent chemotherapy, although seven cats with localised intestinal, ocular and subcutaneous lesions had these lesions partially (2 intestinal lesions) or completely (2 eyes, 2 intestinal lesions and a cluster of regional lymph nodes) resected prior to starting chemotherapy. The median survival time for these 60 cats was 116 days. Of the 60 cats, 48 rapidly went into complete remission following the administration of 1-asparaginase, vincristine and prednisolone (complete remission rate 80%) and these cats had a median survival of 187 days. Three cats were censored from further analysis as their long-term survival data were uninterpretable because they died of causes unrelated to lymphosarcoma or were prematurely lost to follow-up. Twenty cats were classed as 'long-term survivors' based on survival time in excess of one year and at least 14 were 'cured' based on the absence of physical evidence of lymphosarcoma 2-years after initiating treatment. In other words, of the 48 cats that reached complete remission, in excess of 29% were 'cured'. Despite detailed analysis, few meaningful prognostic indicators based on patient or tumour characteristics were identified, although long-term survivors were more likely to be less than 4-years (P= 0.04) and to have tumours of the T-cell phenotype (P= 0.06). Excluding the one FeLV ELISA-positive cat with mediastinal LSA, 7 of 9 cats less than 4 years-of-age were long-term survivors (median survival time >1271 days). There was a strong association between achieving complete remission and long-term survival (P = 0.003). On the basis of 27 replies to a questionnaire, owners were generally very satisfied with the response to chemotherapy, irrespective of the survival time of the individual patient. Eighty five percent of owners expressed complete satisfaction with their decision to pursue chemotherapy and 70% believed their cat's health status improved during the first 2-weeks of treatment. Importantly, 78% of owners considered that chemotherapy required a very substantial time commitment on their part.

CONCLUSIONS

It was possible to cure approximately one quarter of cats with lymphosarcoma using sequential multi-agent chemotherapy and/or surgery. FeLV-negative cats younger than 4 years (typically with mediastinal lymphosarcoma) had a particularly favourable prognosis. The decision to embark on chemotherapy should be based on the results of induction chemotherapy with l-asparaginase, vincristine and prednisolone, as the response to this was a good predictor of long-term survival. Cats surviving the first 16 weeks of chemotherapy generally enjoyed robust remissions (in excess of 1 year) or were cured of their malignancy.