Indications, management, and outcome of long-term positive-pressure ventilation in dogs and cats: 148 cases (1990-2001)

Nursing strategies for the mechanically ventilated patient

The goal of this manuscript is to provide a comprehensive and multi-disciplinary review of the best nursing practices of caring for mechanically ventilated patients. By reviewing human medicine literature, the authors will extrapolate procedures that have been found to be most effective in reducing the risk of mechanical ventilation (MV) complications. Paired with review of the current standards in veterinary medicine, the authors will compile the best practice information on mechanically ventilated patient care, which will serve as a detailed resource for the veterinary nursing staff. Written from a nursing standpoint, this manuscript aims to consolidate the nursing assessment of a mechanically ventilated patient, addressing both systemic and physical changes that may be encountered during hospitalization. The goal of this review article is to present information that encourages a proactive approach to nursing care by focusing on understanding the effects of polypharmacy, hemodynamic changes associated with MV, complications of recumbent patient care, and sources of hospital acquired infections. When applied in conjunction with the more technical aspects of MV, this manuscript will allow veterinary technicians involved in these cases to understand the dynamic challenges that mechanically ventilated patients present, provide guidance to mitigate risk, address issues quickly and effectively, and create an up-to date standard of practice that can be implemented.

Mechanical ventilation in snake envenomation of dogs and cats

Envenomation by snakes in Elapidae and Viperidae families have been associated with respiratory failure in dogs and cats. Mechanical ventilation may be required for hypoventilation due to neuromuscular paralysis or hypoxemia due to pulmonary hemorrhage or aspiration pneumonia. Median incidence of dogs and cats with snake envenomation that require mechanical ventilation is 13% (0.06-40%). Standard treatment of snake envenomation in dogs and cats includes prompt administration of appropriate antivenom and management of envenomation complications such as coagulopathy, rhabdomyolysis and acute kidney injury. When mechanical ventilation is required, overall prognosis is good with appropriate treatment. Standard anesthetic protocols and mechanical ventilator settings are generally appropriate, with lung protective ventilation strategies typically reserved for patients with pulmonary disease. Median survival to discharge for cats and dogs with elapid envenomation is 72% (76-84%) with 33 h (19.5-58 h) median duration of mechanical ventilation and 140 h (84-196 h) median hospitalization. This article reviews indications for mechanical ventilation in cats and dogs with snake envenomation, and discusses ventilator settings, anesthetic and nursing considerations, complications and outcomes specific to this disease.

Noncardiogenic pulmonary edema in small animals

OBJECTIVE

To review various types of noncardiogenic pulmonary edema (NCPE) in cats and dogs.

ETIOLOGY

NCPE is an abnormal fluid accumulation in the lung interstitium or alveoli that is not caused by cardiogenic causes or fluid overload. It can be due to changes in vascular permeability, hydrostatic pressure in the pulmonary vasculature, or a combination thereof. Possible causes include inflammatory states within the lung or in remote tissues (acute respiratory distress syndrome [ARDS]), airway obstruction (post-obstructive pulmonary edema), neurologic disease such as head trauma or seizures (neurogenic pulmonary edema), electrocution, after re-expansion of a collapsed lung or after drowning.

DIAGNOSIS

Diagnosis of NCPE is generally based on history, physical examination, and diagnostic imaging. Radiographic findings suggestive of NCPE are interstitial to alveolar pulmonary opacities in the absence of signs of left-sided congestive heart failure or fluid overload such as cardiomegaly or congested pulmonary veins. Computed tomography and edema fluid analysis may aid in the diagnosis, while some forms of NCPE require additional findings to reach a diagnosis.

THERAPY

The goal of therapy for all types of NCPE is to preserve tissue oxygenation and reduce the work of breathing. This may be achieved by removing the inciting cause (eg, airway obstruction) and cage rest in mild cases and supplemental oxygen in moderate cases and may require mechanical ventilation in severe cases.

PROGNOSIS

Prognosis is generally good for most causes of veterinary NCPE except for ARDS, although data are scarce for some etiologies of NCPE.

Clinical review of high-flow nasal oxygen therapy in human and veterinary patients

Oxygen therapy is the first-line treatment for hypoxemic acute respiratory failure. In veterinary medicine this has traditionally been provided via mask, low-flow nasal oxygen cannulas, oxygen cages and invasive positive pressure ventilation. Traditional non-invasive modalities are limited by the maximum flow rate and fraction of inspired oxygen (FiO₂) that can be delivered, variability in oxygen delivery and patient compliance. The invasive techniques are able to provide higher FiO₂ in a more predictable manner but are limited by sedation/anesthesia requirements, potential complications and cost. High-flow nasal oxygen therapy (HFNOT) represents an alternative to conventional oxygen therapy. This modality delivers heated and humidified medical gas at adjustable flow rates, up to 60 L/min, and FiO₂, up to 100%, via nasal cannulas. It has been proposed that HFNOT improves pulmonary mechanics and reduces respiratory fatigue via reduction of anatomical dead space, provision of low-level positive end-expiratory pressure (PEEP), provision of constant FiO₂ at rates corresponding to patient requirements and through improved patient tolerance. Investigations into the use of HFNOT in veterinary patients have increased in frequency since its clinical use was first reported in dogs with acute respiratory failure in 2016. Current indications in dogs include acute respiratory failure associated with pulmonary parenchymal disease, upper airway obstruction and carbon monoxide intoxication. The use of HFNOT has also been advocated in certain conditions in cats and foals. HFNOT is also being used with increasing frequency in the treatment of a widening range of conditions in humans. Although there remains conflict regarding its use and efficacy in some patient groups, overall these reports indicate that HFNOT decreases breathing frequency and work of breathing and reduces the need for escalation of respiratory support. In addition, they provide insight into potential future veterinary applications. Complications of HFNOT have been rarely reported in humans and animals. These are usually self-limiting and typically result in lower morbidity and mortality than those associated with invasive ventilation techniques.

Mechanical ventilation in dogs and cats with tick paralysis

Respiratory failure from tick paralysis (TP) is an important cause of mortality in cats and dogs in Australia, occurring from a combination of respiratory muscle paralysis, upper respiratory tract obstruction and pulmonary disease. Patients may require positive-pressure ventilation in management of any combination of hypoxemia, hypoventilation or respiratory fatigue, but may also require airway management due to laryngeal paralysis. No single ventilation strategy is recommended due to the heterogenous disease presentations. Lung protective ventilation should be used in patients with pulmonary disease. Due to local and systemic effects of TP, patients are at higher risk of complications such as aspiration pneumonia and corneal ulceration and may have additional intravenous fluid and nutritional considerations. Treatment with hyperimmune serum is associated with improved outcomes. Prognosis is considered good with documented survival to discharge (STD) of 52.6-77% for animals with TP ventilated with lung disease and 90.5% for animals without lung disease. Median reported duration of ventilation for TP ranges from 23 to 48 h (range 3 h-10 days). The severity of individual neuromuscular signs and the presence of associated conditions such as aspiration pneumonia and laryngeal paralysis may necessitate longer periods of mechanical ventilation. This review aims to summarize the current recommendations regarding indications, management and prognosis of cats and dogs undergoing MV for TP and to identify areas for future research.

Retrospective evaluation of transportation and outcome of dogs on a mechanical ventilator: 9 cases

OBJECTIVE

To describe the transportation and clinical outcome of 9 dogs transported to a referral hospital on mechanical ventilation (MV).

DESIGN

Retrospective case series (2015-2020).

SETTING

University teaching hospital.

ANIMALS

Nine dogs transported to a referral center on MV.

INTERVENTIONS

All dogs underwent MV during vehicular transport.

MEASUREMENT AND MAIN RESULTS

The medical records of 9 dogs transported on a MV to a university teaching hospital were reviewed. Data collected included signalment, reason for MV, ventilator settings, sedation protocol, monitoring in transit, distance traveled, complications, clinical outcome, and cost. All dogs transported survived transport to the referral hospital and 8 of 9 were successfully weaned from the ventilator and discharged home.

CONCLUSIONS

MV during transport in this setting was practical and safe. Dogs in this study had a high survival rate compared to previous studies of dogs undergoing MV, likely due to selection of cases assessed to have a correctable underlying disease.

High-flow nasal cannula improves hypoxemia in dogs failing conventional oxygen therapy

OBJECTIVE

A prospective clinical trial was performed to evaluate the efficacy and tolerance of high-flow nasal cannula (HFNC) in dogs with hypoxemia.

ANIMALS

20 client-owned dogs failing conventional oxygen therapy (COT).

PROCEDURES

Patients admitted to the ICU for treatment of hypoxemic respiratory failure were enrolled in the study. PaO2, SPO2, respiratory rate (RR), and acute patient physiologic and laboratory evaluation scores were obtained at the time of COT failure and after initiation of HFNC. Complications and patient tolerance while receiving HFNC were also recorded.

RESULTS

Compared to COT, the median PaO2 and SO2 were significantly higher when dogs were receiving HFNC (60.8 vs 135.6 mm Hg and 90.7% vs 99.25%, respectively). Dogs receiving HFNC had a significant reduction in median RR as compared to dogs undergoing COT (52 vs 36 breaths per minute). After the initiation of HFNC, all dogs showed clinical improvement as measured by PaO2, SO2, and RR. Of 20 dogs, 6 ultimately failed HFNC and mechanical ventilation was recommended. Nine dogs undergoing HFNC survived to discharge, and acute patient physiologic and laboratory evaluation scores had a significant positive severity correlation with death. Complications included pneumothorax in 1 dog.

CLINICAL RELEVANCE

COT has limited flow rates due to airway irritation caused by room temperature, nonhumidified oxygen. HFNC uses vapor humidification and heated oxygen, allowing for higher flow rates. In people, HFNC is used as escalation of oxygen therapy when COT fails. Dogs treated with HFNC had significant improvements in PaO2, SO2, and RR as compared to COT. HFNC is well tolerated and effective in treating hypoxemia in dogs.

Inclusion of airway pressure release ventilation in the management of respiratory failure and refractory hypercapnia in a dog

OBJECTIVE

To describe the use of airway pressure release ventilation (APRV) to relieve hypercapnia in a dog undergoing mechanical ventilation.

CASE SUMMARY

A 3-month-old male Shar-Pei mix presented to the emergency department with suspected noncardiogenic pulmonary edema. Due to severe hypercapnia, mechanical ventilation was initiated. The hypercapnia failed to improve with conventional pressure control mechanical ventilation, bronchodilator administration, suctioning, or endotracheal tube replacement. The dog was transitioned to APRV and maintained in this mode for 36 hours. A modified APRV protocol in which inverse inspiratory to expiratory ratios ranged from 4.3:1 to 6.0:1 was utilized, resulting in a drastic improvement in the patient's hypercapnia. The patient eventually was transitioned off the ventilator, and no respiratory abnormalities have been noted at subsequent recheck examinations.

NEW OR UNIQUE INFORMATION PROVIDED

This case documents the first use of APRV to relieve refractory hypercapnia in a dog undergoing mechanical ventilation and is one of the only recorded cases of using APRV for this purpose in the medical literature at large. APRV may be considered in cases of hypercapnia when traditional therapies fail, although caution is warranted as this mode of ventilation can also worsen hypercapnia.

Retrospective evaluation of the outcome and prognosis of undergoing positive pressure ventilation due to cardiac and noncardiac causes in dogs and cats (2019-2020): 101 cases

OBJECTIVE

To compare the short- and long-term outcomes of dogs and cats with left-sided congestive heart failure (L-CHF) undergoing positive pressure ventilation (PPV) to patients undergoing PPV for other causes and to determine risk factors associated with outcomes in this population.

DESIGN

This retrospective study included dogs and cats that underwent PPV during 2018-2020. The study group included patients diagnosed with L-CHF. The control group included patients who were ventilated for reasons other than L-CHF. The risk factors evaluated included vital signs on presentation, ventilator settings, development of azotemia during hospitalization, cardiopulmonary resuscitation (CPR), complications, and medications used.

SETTING

University Teaching Hospital.

ANIMALS

Fifty (32 dogs, 18 cats) study group animals and 51 (39 dogs, 12 cats) control group animals were included in the L-CHF and control groups, respectively.

MEASUREMENTS AND MAIN RESULTS

Sixty-six percent (33/50) of L-CHF patients, compared with 35% (18/51) of the control patients, were weaned off PPV (P = 0.002). Fifty-four percent (27/50) of the L-CHF patients survived to discharge, compared with 26% (13/51) of the control group patients (P = 0.003). However, only 54% (12/22) of the discharged L-CHF patients survived for >2 months compared to 100% of the control patients. The median survival time for dogs and cats with L-CHF surviving to discharge was 240 days (range: 1-730 days). In dogs, factors negatively associated with survival included CPR in both groups and the development of azotemia in the L-CHF group. Anemia on presentation was negatively associated with survival for both cats and dogs in the control group.

CONCLUSIONS

Dogs and cats undergoing PPV due to L-CHF were more commonly weaned off the ventilator and survived to discharge compared to other causes necessitating PPV. However, these patients suffer from severe heart disease, and therefore, their long-term survival is guaranteed.

Indications and outcome associated with positive-pressure ventilation in dogs and cats: 127 cases

OBJECTIVES

To determine the indications and outcomes of positive-pressure ventilation (PPV) and identify factors associated with successful weaning.

DESIGN

Retrospective study from October 2009 to September 2013.

SETTING

University teaching hospital.

ANIMALS

One hundred and eleven dogs and 16 cats.

MEASUREMENTS AND MAIN RESULTS

Medical records were retrospectively reviewed; signalment, indication for PPV, patient characteristics, blood gas, and ventilator variables during PPV, duration of PPV, and outcome were recorded. Dogs were most commonly ventilated for pneumonia (36/111; 32%) and cats for multiple pulmonary diseases (8/16; 50%). The median duration of PPV for all animals was 25.7 h (range, 0.1-957 h). Long-term PPV (≥24 h) was performed in 53% of cases. No differences were noted in successful weaning rates between cases ventilated for pulmonary etiologies (23/99; 23%) versus nonpulmonary etiologies (9/28; 32%). Overall, 32 of 127 (25%; 30 dogs, 2 cats) animals were successfully weaned from PPV and 28 of 127 (22%; 26 dogs, 2 cats) survived to hospital discharge. Long-term ventilation had a higher likelihood of successful weaning (26/67 [39%] vs 6/60 [10%], P = 0.0002) and higher rates of survival to discharge (23/67 [34%] vs 5/60 [8%], P = 0.0005) than short-term ventilation. Animals with higher Pao₂ /Fio₂ and Spo₂ /Fio₂ and lower APPLE and SOFA scores on day 1 of PPV were more likely to be weaned (P < 0.03).

CONCLUSIONS

The outcome of PPV appears to be most heavily determined by the underlying disease process and no clear improvement in outcome could be demonstrated in this study, despite advances in veterinary critical care and ventilator management strategies since previous studies. Dogs and cats receiving PPV for more than 24 h in this study had a higher likelihood of a positive outcome. Several indices of oxygenation and illness severity at the onset of PPV were predictive of outcome and maybe useful when considering prognosis of these cases.

Complications associated with long-term positive-pressure ventilation in dogs and cats: 67 cases

OBJECTIVES

To determine the complications associated with positive-pressure ventilation (PPV) in dogs and cats.

DESIGN

Retrospective study from October 2009 to September 2013.

SETTING

University Teaching Hospital.

ANIMALS

Fifty-eight dogs and 9 cats.

MEASUREMENTS AND MAIN RESULTS

Medical records were retrospectively reviewed; signalment, complications associated with PPV, duration of PPV, and outcome were recorded. Complications most commonly recorded during PPV included hypothermia 41/67 (61%), hypotension 39/67 (58%), cardiac arrhythmias 33/67 (49%), a positive fluid balance 31/67 (46%), oral lesions 25/67 (37%), and corneal ulcerations 24/67 (36%). A definition of ventilator-associated events (VAE) extrapolated from the Center of Disease Control's criteria was applied to 21 cases that received PPV for at least 4 days in this study. Ventilator-associated conditions occurred in 5 of 21 (24%) of cases with infection-related ventilator-associated conditions and ventilator-associated pneumonia identified in 3 of 21 (14%) cases.

CONCLUSIONS

Complications are common and diverse in dogs and cats receiving long-term PPV and emphasizes the importance of intensive, continuous patient monitoring and appropriate nursing care protocols. Many of the complications identified could be serious without intervention and suggests that appropriate equipment alarms could improve patient safety. Development of veterinary specific surveillance tools such as the VAE criteria would aid future investigations and allow for effective multicenter studies.

Suspected benzodiazepine withdrawal-associated seizures in 3 young dogs undergoing mechanical ventilation

OBJECTIVE

To describe new onset of generalized seizures in 3 young dogs following cessation of a benzodiazepine-containing sedation protocol to facilitate mechanical ventilation (MV) for hypoxemia.

SERIES SUMMARY

Three dogs under 5 months of age underwent MV due to severe hypoxemia. All 3 dogs were sedated with a constant rate infusion of benzodiazepines as part of their sedation protocol to facilitate MV. All 3 dogs had an acute onset of generalized seizures within 36 hours of sedation cessation and weaning from MV. All 3 dogs' seizures were successfully managed with a slow, tapering course of benzodiazepines. One dog was additionally treated with levetiracetam at the time of initial seizure activity, which was discontinued 1 year following discharge and absence of ongoing seizure activity. All 3 dogs were discharged successfully with no reports of ongoing seizures or neurologic deficits after discharge.

NEW OR UNIQUE INFORMATION PROVIDED

Young dogs managed with benzodiazepines to facilitate MV may have acute onset of generalized seizures following cessation, which can be successfully managed with short-term benzodiazepine therapy. The 3 cases in this series demonstrated a positive outcome and were successfully managed following acute onset of generalized seizure activity post-MV.

Subclinical Hypoventilation in Dogs Undergoing Ventral Slot Decompressive Surgery for Cervical Myelopathy Due to Intervertebral Disc Herniation

The objective of this prospective cohort study was to document the occurrence of post-operative hypoventilation in dogs undergoing decompressive ventral slot or hemilaminectomy for the treatment of intervertebral disc herniation (IVDH). Twenty dogs undergoing ventral slot surgery and 20 dogs undergoing hemilaminectomy surgery for the treatment of IVDH that presented to XX between 2017 and 2020 were enrolled. Dogs were anesthetized using a standard protocol. Blood gas samples were taken at up to 11 time points beginning during anesthetic recovery and continuing for a maximum of 72 h post-operatively. Dogs with cervical lesions that were non-ambulatory before surgery had more evidence of subclinical hypoventilation in the immediate peri-extubation period than dogs with less severe injuries or those undergoing hemilaminectomy surgery. We found no difference in the ventilation status in dogs undergoing cervical or thoracolumbar decompressive surgery for IVDH from 8 to 72 h post-operatively. Other markers of acid-base status indicated that subclinical hypoventilation within the peri-extubation period was transient and self-limiting. There was a moderate positive correlation between sedation scores and estimated PaCO₂. These data suggest that dogs with severe cervical spinal cord injuries may be at risk for subclinical hypoventilation in the immediate peri-extubation period. Increased sedation may be correlated with decreased ventilatory status in dogs recovering from decompressive vertebral column surgery.

Ventilatory failure in a cat following radical chest wall resection for feline injection site sarcoma

Case summary

A 12-year-old spayed female domestic shorthair cat presented for chest wall resection and radiation therapy following incomplete surgical excision of a feline injection site sarcoma. A CT scan for surgical planning was performed under general anesthesia and showed extensive tumor infiltration of the soft tissues of the right thorax. The cat recovered uneventfully from this anesthetic event. Nineteen days later, the patient was reanesthetized for forequarter amputation plus radical chest wall resection, including ribs 3–8 and all associated soft tissues plus adjacent spinous processes. Postoperatively, the patient developed acute respiratory failure secondary to hypoventilation. The cat was mechanically ventilated for 12 h prior to being successfully weaned from the ventilator. However, the improvement was transient and mechanical ventilation was reinitiated 6 h later owing to respiratory fatigue. On the second day, the cat developed unexplained central nervous system signs and was euthanized.

Relevance and novel information

To our knowledge, this is the first case report to describe ventilatory failure secondary to radical chest wall resection in a cat. Hypoventilation with subsequent need for mechanical ventilation is a potential complication that should be considered during preoperative planning in patients requiring extensive chest wall resections.

Ventilated postmortem computed tomography to evaluate the lungs of dogs with and without focal lung lesions

OBJECTIVE

To identify the optimal ventilation pressure for ventilated postmortem CT assessment of the lungs in cadaveric dogs and compare the optimal ventilation pressures between dogs with and without focal lung lesions.

SAMPLE

12 cadaveric dogs.

PROCEDURES

CT was performed with dogs positioned in sternal recumbency within 30 to 180 minutes after death. After orotracheal intubation, lungs were aerated to ventilation pressures of 0, 10, 15, 20, 25, 30, and 35 cm H₂O. Lung attenuation measurements were made at 5 predetermined anatomical locations with use of a multi-image analysis graphic user interface tool. Lungs were considered hyperaerated (-1000 to -901 HU), normo-aerated (-900 to -501 HU), poorly aerated (-500 to -101 HU), and nonaerated (-100 to 100 HU) on the basis of lung attenuation values. Optimal ventilation pressure was defined as the pressure at which the percentage of normo-aerated lung was greatest. For analysis, dogs were assigned to one group when focal lung lesions were evident and to another group when lesions were not evident.

RESULTS

Median optimal ventilation pressure was significantly higher for those dogs with lung lesions (35 cm H₂O), compared with those without (25 cm H₂O).

CONCLUSIONS AND CLINICAL RELEVANCE

A ventilation pressure of 35 cm H₂O may be considered for ventilated postmortem CT to determine the presence of focal lung lesions; however, further investigation is required.

Quality of life following mechanical ventilation in dogs and cats

BACKGROUND

Mechanical ventilation is frequently performed in small animal critical care medicine with well-documented survival data; quality of life in these patients following discharge from hospital is unknown.

KEY FINDINGS

Owners of patients surviving to discharge following mechanical ventilation were surveyed with an open ended and ranking score questionnaire. Response rate was 57% (27/47). All respondents rated their pet's quality of life prior to the illness necessitating ventilation as good to excellent (8/10-10/10). Perceived recovery periods ranged from 0 days to 6 months (the most common response being 2-3 weeks). Fourteen owners stated that their pets' quality of life was as good or better than previously. Patients with persistent quality of life concerns (n = 3) had been ventilated for neurological disease. Four owners reported changed behaviors such as startling easily or being excessively responsive to noise. One cat became deaf and at time of survey had not regained hearing. Commonly reported problems included decreased exercise tolerance (n = 3). All respondents stated that they would ventilate their pet again.

SIGNIFICANCE

Cats and dogs that are mechanically ventilated appear to recover with minimal adverse effect on their quality of life. Patients ventilated for neurological conditions may be more likely to experience quality of life limitations.

Seizure activity following atracurium continuous rate infusion in three mechanically ventilated juvenile dogs

OBJECTIVE

To describe patient recovery in dogs that had undergone mechanical ventilation (MV) and received atracurium as a continuous rate infusion (CRI).

CASE SERIES SUMMARY

Three dogs were treated with atracurium CRI while mechanically ventilated and were successfully weaned. All were pediatric patients (2-3 months old) ventilated due to respiratory fatigue and hypoxemia. All dogs experienced seizure activity in the initial 24 h following extubation and were treated with various anticonvulsant protocols; no patients experienced documented seizures after 48 h of discontinuation from MV.

NEW OR UNIQUE INFORMATION PROVIDED

All three successfully weaned dogs that had received an atracurium CRI experienced new onset seizures in their recovery from MV. Atracurium use in long-term MV has not been described previously, and seizures in dogs following atracurium administration has not been described in the clinical setting. Although causation cannot be proven in this case series, atracurium use should be carefully considered and be monitored appropriately when used for a prolonged duration.

Brachycephalic airway syndrome: management of post-operative respiratory complications in 248 dogs

OBJECTIVE

As ownership of brachycephalic dog breeds rises, the surgical correction of components of brachycephalic airway syndrome (BAS) is increasingly recommended by veterinarians. This study's objective was to describe the incidence of, and strategies for the management of post-operative respiratory complications in brachycephalic dogs undergoing surgical correction of one or more components of BAS.

METHODS

Medical records of 248 brachycephalic dogs treated surgically for BAS were retrospectively reviewed for demographic information, procedures performed, post-operative complications and treatment implemented, hospitalisation time, and necessity for further surgery.

RESULTS

Pugs, Cavalier King Charles Spaniels and British Bulldogs were the most commonly encountered breeds. Dogs which experienced a complication were significantly older (mean was 5.5 years, compared with 4.1 years [P < 0.01]). Fifty-eight dogs (23.4%) had complications which included: dyspnoea managed with supplemental oxygen alone (7.3%, n = 18), dyspnoea requiring anaesthesia and re-intubation (8.9%, n = 22), dyspnoea necessitating treatment with a temporary tracheostomy (8.9%, n = 22), aspiration pneumonia (4%, n = 10), and respiratory or cardiac arrest (2.4%, n = 6). Five of the 22 dogs requiring anaesthesia and re-intubation deteriorated 12 or more hours after post-surgical anaesthetic recovery. The overall mortality rate in this study was 2.4% (n = 6). Age, concurrent airway pathology, and emergency presentation significantly predicted post-operative complications.

CONCLUSION

Our data show the importance of close monitoring for a minimum of 24 h following surgery by an experienced veterinarian or veterinary technician. Surgical intervention for BAS symptomatic dogs should be considered at an earlier age as an elective procedure, to reduce the risk of post-operative complications.

Tidal volume in mechanically ventilated dogs: can human strategies be extrapolated to veterinary patients?

This paper compares and describes the tidal volume (Vt) used in mechanically ventilated dogs under a range of clinical conditions. Twenty-eight dogs requiring mechanical ventilation (MV) were classified into 3 groups: healthy dogs mechanically ventilated during surgery (group I, n = 10), dogs requiring MV due to extra-pulmonary reasons (group II, n = 7), and dogs that required MV due to pulmonary pathologies (group III, n = 11). The median Vt used in each group was 16 mL/kg (interquartile range [IQR], 15.14-21) for group I, 12.59 mL/kg (IQR, 9-14.25) for group II, and 12.59 mL/kg (IQR, 10.15-14.96) for group III. The Vt used was significantly lower in group III than in group I (p = 0.016). The thoraco-pulmonary compliance was significantly higher in group I than in groups II and III (p = 0.011 and p = 0.006, respectively). The median driving pressure was similar among the groups with a median of 9, 11, and 10 cmH₂O in groups I, II, and III, respectively (p = 0.260). Critically-ill dogs requiring MV due to the primary pulmonary pathology received a significantly lower Vt than healthy dogs but with a range of values that were markedly higher than those recommended by human guidelines.

Clinical manifestations, laboratory findings, treatment and outcome of acute organophosphate or carbamate intoxication in 102 dogs: A retrospective study

Organophosphates (OP) and carbamates are commonly used insecticides and important intoxication sources of humans and animals. Nevertheless, large scale studies of these intoxications in dogs are unavailable. The medical records of dogs presented to a veterinary hospital were reviewed retrospectively. The study included 102 dogs definitely diagnosed with acute OP or carbamate intoxication. The most common presenting clinical signs included muscle tremor, hypersalivation, miosis, weakness, vomiting and diarrhea. Hypersalivation, muscle tremor and tachypnea were significantly (P < 0.05) associated with survival to discharge; while weakness, mental dullness, anorexia, pale mucous membranes and paddling were significantly associated with death. Common laboratory abnormalities included decreased butyrylcholine esterase activity, acidemia, increased total plasma protein, leukocytosis, hypochloridemia, hyperbilirubinemia, increased creatinine and alanine transaminase (ALT), aspartate transaminase (AST) and creatine kinase activities, and prolonged activated partial thromboplastin time (aPTT). Compared to the survivors, the non-survivors showed significantly: higher frequencies of thrombocytopenia, hypocarbemia, prolonged prothrombin time (PT), hypernatremia, hyperkalemia, hypocholesterolemia, hypoproteinemia, hypertriglyceridemia, increased ALT activity and increased urea concentration; lower median concentrations of venous blood bicarbonate, serum chloride and total CO₂; and higher medians of PT, serum total bilirubin and urea concentrations, and ALT and AST activities. Intoxicated dogs were commonly treated with diphenhydramine, atropine-sulfate, antibiotics, diazepam and pralidoxime, while some (19.2%) required general anesthesia and mechanical ventilation. The survival rate of dogs treated by gastric lavage was higher (P = 0.041) compared to that of the remaining dogs. Development of respiratory failure and mechanical ventilation requirement were significantly associated (P < 0.001) with death. The mortality rate was 17%.

Prospective pilot study for evaluation of high-flow oxygen therapy in dyspnoeic dogs: the HOT-DOG study

OBJECTIVES

To describe the use, effectiveness and tolerance of high-flow oxygen therapy in dyspnoeic dogs.

MATERIALS AND METHODS

Prospectively, dogs in acute respiratory distress admitted to an intensive care unit between January and May 2018 that failed to respond to nasal oxygen therapy and medical stabilisation after 30 minutes were transitioned to high-flow oxygen therapy. High-flow oxygen therapy, delivered an inspired oxygen fraction of 100% using an air/oxygen blender, active humidifier, single warmed tube and specific nasal cannula. Respiratory rate, pulse oximetry (SpO₂ ), heart rate and a tolerance score were assessed every 15 minutes from T₀ (under nasal oxygen) to 1 hour (T₆₀ ), and PaO₂ and PaCO₂ at T₀ and T₆₀ . Complications were recorded for each dog.

RESULTS

Eleven dogs were included. At T₆₀ , PaO₂ , flow rate and SpO₂ were significantly greater than at T₀ (171 ± 123 versus 73 ± 24 mmHg; P=0.015; 18 ±12 L/minute versus 3.2 ± 2.0 L/minute, P<0.01; 97.7 ±2.3% versus 91.6 ±7.2%, P=0.03, respectively). There was no significant difference in PaCO₂ , respiratory rate or heart rate between T₀ and T₆₀ . Tolerance was excellent, and there were no complications.

CLINICAL SIGNIFICANCE

High-flow oxygen therapy improves markers of oxygenation in dyspnoeic dogs and is an effective means to deliver oxygen with comfort and minimal complications.

Risk factors, characteristics, and outcomes of acute respiratory distress syndrome in dogs and cats: 54 cases

OBJECTIVE

To characterize the clinical features of the acute respiratory distress syndrome (ARDS), risk factors, and outcome in dogs and cats. The study also aimed to evaluate the current veterinary criteria for the diagnosis of ARDS by comparison of clinical diagnostic criteria with necropsy findings.

DESIGN

Retrospective study.

ANIMALS

Fifty-four client-owned animals, 46 dogs and 8 cats.

INTERVENTIONS

Medical records were reviewed for patients with the diagnosis of ARDS based on previously published clinical criteria or necropsy diagnosis. Signalment, clinical findings, and outcome were recorded.

MEASUREMENTS AND MAIN RESULTS

Animals were grouped according to a clinical or necropsy diagnosis: 43/54 (80%) were diagnosed with ARDS based on clinical criteria (group 1) and 11/54 (20%) were diagnosed with ARDS based on necropsy only (group 2). In group 1, 22/43 (51%) had a necropsy, which confirmed ARDS in 12/22 (54%). Direct (pulmonary) causes of ARDS were more common than indirect causes in dogs, while cats had a similar occurrence of direct and indirect causes. The most common risk factors identified in dogs were aspiration pneumonia (42%), systemic inflammatory response syndrome (SIRS) (29%), and shock (29%). All cats diagnosed clinically with ARDS had SIRS with or without sepsis. Of the animals with a clinical diagnosis of ARDS, 49% received mechanical ventilation and 58% received treatment (with or without mechanical ventilation) for 24 hours or longer. The overall case fatality rate was 84% in dogs and 100% in cats.

CONCLUSIONS AND CLINICAL RELEVANCE

As described in human literature, pneumonia was the most common risk factor in dogs with ARDS, whereas it was SIRS for the cat population. The high mortality rate and discrepancy between the clinical diagnosis and necropsy findings may highlight limitations in the clinical criteria for the diagnosis of ARDS and treatment in dogs and cats.

Australian elapid snake envenomation in cats: Clinical priorities and approach

Practical relevance: No fewer than 140 species of terrestrial snakes reside in Australia, 92 of which possess venom glands. With the exception of the brown tree snake, the venom-producing snakes belong to the family Elapidae. The venom of a number of elapid species is more toxic than that of the Indian cobra and eastern diamondback rattle snake, which has earned Australia its reputation for being home to the world's most venomous snakes. Clinical challenges: The diagnosis of elapid snake envenomation is not always easy. Identification of Australian snakes is not straightforward and there are no pathognomonic clinical signs. In cats, diagnosis of envenomation is confounded by the fact that, in most cases, there is a delay in seeking veterinary attention, probably because snake encounters are not usually witnessed by owners, and also because of the tendency of cats to hide and seek seclusion when unwell. Although the administration of antivenom is associated with improved outcomes, the snake venom detection kit and antivenom are expensive and so their use may be precluded if there are financial constraints. Evidence base: In providing comprehensive guidance on the diagnosis and treatment of Australian elapid snake envenomation in cats, the authors of this review draw on the published veterinary, medical and toxicology literature, as well as their professional experience as specialists in medicine, and emergency medicine and critical care.

Avaliação metabólica e hemodinâmica de dois protocolos de sedação prolongada em cães

RESUMO Objetivou-se determinar a viabilidade de dois protocolos de sedação para ventilação prolongada em cães e seus efeitos hemodinâmicos e metabólicos. Doze cães, alocados aleatoriamente em dois grupos (n=6), receberam infusão contínua de midazolam (0,5mg/kg/h), fentanil (10µg/kg/h) e propofol (18mg/kg/h) no GMF ou cetamina (0,6mg/kg/h), morfina (0,26mg/kg/h) e propofol (18mg/kg/h) no GCM, durante 24 horas. Os cães foram ventilados mecanicamente com FiO2 de 40%, mantendo-se a normocapnia. A FC diminuiu 32% no GMF e 34% no GCM ao longo do tempo, reduzindo o IC em 24% no GMF e em 29% no GCM. A CaO2, o CvmO2, a DO2 e o VO2 diminuíram no GCM (5%, 16%, 31% e 7%) e no GMF (4%, 19%, 26% e 15%), respectivamente. A TEO2 aumentou 32% no GMF e 36% no GCM, sem diferenças entre grupos, porém a calorimetria indireta demonstrou diminuição do VO2, minimizando a redução da DO2. Não houve diferença entre os tempos para extubação, deambulação e recuperação total, com médias globais (minutos) de 33,8±15,9, 134,8±60,7 e 208±77,5, respectivamente. Conclui-se que ambos os protocolos permitiram a ventilação mecânica, com redução do IC e da DO2, porém sem prejuízos hemodinâmicos e metabólicos, podendo ser utilizados com segurança em cães hígidos.

Retrospective evaluation of the prevalence, risk factors, management, outcome, and necropsy findings of acute lung injury and acute respiratory distress syndrome in dogs and cats: 29 cases (2011-2013)

OBJECTIVE

To determine the prevalence and risk factors for veterinary acute lung injury (VetALI) and veterinary acute respiratory distress syndrome (VetARDS), assess mechanical ventilation settings and patient outcomes, and to evaluate the relationship of clinical diagnoses with necropsy findings.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Twenty-four dogs and 5 cats with a clinical diagnosis of VetALI or VetARDS. Control population includes 24 dogs and 5 cats with a clinical diagnosis of respiratory disease other than VetALI or VetARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

VetALI and VetARDS were diagnosed in 3.2% of dogs and 1.3% of cats presenting to the ICU. Systemic inflammatory response syndrome was the most common inciting condition (16/24 dogs, 2/5 cats), followed by vomiting and subsequent aspiration of gastric contents (9/24 dogs), sepsis (5/24 dogs, 3/5 cats), multiple transfusions (4/24 dogs), trauma (3/24 dogs), and adverse drug reactions (1/24 dogs, 1/5 cats).  None of these conditions were found to be significantly associated with a risk of development of VetALI or VetARDS when compared to controls. Twelve dogs (50%) and 4 cats (80%) underwent mechanical ventilation for a median duration of 18 hours in dogs (range: 6-174 h) and 15.5 hours in cats (range: 6-91 h). Overall, 3/29 patients survived to discharge including 2/24 dogs and 1/5 cats. Necropsy results were available for 8/22 dogs and 3/4 cats. A total of 6/8 dogs (75%) dogs and 3/3 (100%) cats met the histopathologic criteria for diagnosis of VetALI or VetARDS.

CONCLUSIONS

VetALI and VetARDS can cause life-threatening respiratory distress in dogs and cats necessitating mechanical ventilation in 50% of dogs and 80% of cats in this study. These diseases are associated with a poor clinical outcome and a high rate of humane euthanasia.

Retrospective evaluation of cats with elapid snake envenomation associated neurotoxicity requiring mechanical ventilation: 12 cases (2005-2014)

OBJECTIVE

To retrospectively determine the population and outcome characteristics of a cohort of Australian elapid snake envenomed cats requiring mechanical ventilation (MV).

DESIGN

Retrospective observational study (2005-2014).

SETTING

Academic veterinary emergency and critical care service.

ANIMALS

Twelve cats undergoing MV for elapid snake envenomation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The medical records were searched to identify cats requiring MV as part of treatment for elapid snake envenomation. Signalment, the indication for, duration of and complications associated with MV, duration of hospitalization, and survival to hospital discharge were recorded for each of the enrolled cases. Seven cats (58.3%) underwent MV because of presumed unsustainable respiratory effort and 5 cats (41.7%) for respiratory arrest. Eleven cats (91.7%) were successfully weaned from MV and survived to hospital discharge. No cats developed ventilator associated pneumonia or pneumothorax. The median duration of MV was 19.5 hours for the survivors (range 7.0-37.0 hours) and median duration of hospitalization was 3.5 days (range 2.4-14.9 days).

CONCLUSIONS

Cats requiring MV for elapid snake envenomation have a favorable outcome and require a relatively short period of MV. Complications encountered are unlikely to influence outcome.

Prevalence and risk factors for development of hemorrhagic gastro-intestinal disease in veterinary intensive care units in the United Kingdom

OBJECTIVE

To determine the prevalence of hemorrhagic gastro-intestinal (GI) disease developing in dogs and cats admitted for management of non-GI disease in veterinary intensive care units (ICUs).

DESIGN

Retrospective study of animals presented between October 2012 and July 2013.

SETTING

Three ICUs located in veterinary teaching hospitals in the United Kingdom.

ANIMALS

Dogs (n = 272) and cats (n = 94) were consecutively enrolled from 3 ICUs if they were hospitalized in the unit for at least 24 hours. Cases were excluded if they had hemorrhagic GI disease in the 48-hour period before presentation or in the 24-hour period after admission. Cases were also excluded if they suffered skull fracture, epistaxis, or hemoptysis, if they underwent surgical procedures of the GI or upper respiratory tracts, or if they were presented for management of GI disease.

MEASUREMENTS AND MAIN RESULTS

Hemorrhagic GI disease was observed in dogs at all 3 units, but at different rates (Center 1: 10.3%, Center 2: 4.8%, Center 3: 2.2%). Hemorrhagic GI disease was not observed in cats at any of the participating centers. Construction of a multivariable logistic regression model revealed that serum albumin concentration, administration of prophylactic gastro-protectant drugs, and institution were significantly associated with the development of hemorrhagic GI disease in dogs. Development of hemorrhagic GI disease and placement of a feeding tube were significantly associated with mortality during the period of hospitalization in dogs. Thirty-seven (13.6%) dogs and 12 (12.8%) cats died or were euthanized while hospitalized, with a higher mortality rate (42.1%) in dogs with hemorrhagic GI disease.

CONCLUSIONS

Hemorrhagic GI disease does develop in dogs hospitalized for management of non-GI disease, but this phenomenon was not observed in cats. Development of hemorrhagic GI disease appeared to have a significant impact on survival in veterinary ICUs.

Oxygenation and Ventilation

Perioperative complications commonly include oxygenation and ventilation abnormalities. The best outcome is associated with prevention. Ventilation impairment may be due to either neurologic compromise such as cervical intervertebral disk disease or severe parenchymal disease, while oxygenation failure may result from either the underlying disease or severe complications such as aspiration pneumonia, volume overload, pulmonary thromboembolism, or acute respiratory distress syndrome. This article reviews the approach to the patient with perioperative complications and provides recommendations on the management approach.

Ventilator waveforms

Ventilator waveforms are graphic representations of changes in pressure, flow, and volume within a ventilator circuit. The changes in these parameters over time may be displayed individually (scalars) or plotted one against another (pressure-volume and flow-volume loops). There are 6 basic shapes of scalar waveforms, but only 3 are functionally distinct (square, ramp, and sine). The pressure scalar is a particularly valuable tool when constant flow (e.g., volume control) modes are employed and an inspiratory pause is added. In this setting, inspection of the pressure waveform can allow determination of static, quasistatic, and dynamic compliance, as well as relative changes in airway resistance. Inspection of the pressure waveform can also help to identify many important aspects of patient drug responses, dyssynchrony, and air trapping (auto positive end-expiratory pressure [auto-PEEP]). Depending on the ventilation mode employed, the shape of the flow waveform may be set by the ventilator operator or may be dependent on patient effort and lung mechanics. Decelerating flow patterns have several important advantages when this option is available. Inspection of flow waveforms is crucial in the recognition of dyssynchrony, setting optimal inspiratory times, evaluating responses to bronchodilators, and the recognition of auto-PEEP. The volume waveform often contains somewhat less useful information than the other 2 scalars, but plays a crucial role in the identification of leaks in the circuit. Pressure-volume loops are particularly useful in setting PEEP and peak inspiratory pressure ranges. Inspection of these loops also often helps in the evaluation of lung mechanics, in the identification of circuit leaks, and in the assessment of patient triggering effort. Flow-volume loops are extremely useful in the identification of leaks and excessive airway secretions as well as alterations in airway resistance. Lastly, serial waveform inspection is crucial to the identification and resolution of patient-ventilator dyssynchrony in many cases.

A case of type B botulism in a pregnant bitch

A two-year-old pregnant Gordon setter presented with acute onset of flaccid tetraparesis and respiratory distress. Neurological examination revealed diffuse lower motor neuron dysfunction. Clostridium botulinum neurotoxin B was isolated from the dog's serum. The dog was hospitalised and received supportive care; respiratory function was monitored but positive-pressure ventilation was not required. Recovery was complete within 1 month and parturition occurred without complication 49 days after admission. The puppies delivered lacked any obvious congenital defects and development during the first few months of life was normal. The source of contamination was suspected to be poorly conserved dry food. To the authors' knowledge, this is the first report of C. botulinum neurotoxin B isolation in a dog and the first report of botulism in a pregnant bitch.

Multiple organ dysfunction syndrome in humans and animals

Multiple organ dysfunction syndrome (MODS), defined as the presence of altered organ function in an acutely ill patient such that homeostasis cannot be maintained without intervention, is a cause of high morbidity and mortality in humans and animals. Many advances have been made in understanding the pathophysiology and treatment of this syndrome in human medicine, but much still is unknown. This comparative review will provide information regarding the history and pathophysiology of MODS in humans and discuss how MODS affects each major organ system in animals.

Successful outcome in a dog with neurological and respiratory signs following smoke inhalation

OBJECTIVE

To report the case management of a patient with smoke inhalation complicated by neurological impairment, carboxyhemoglobinemia, acute respiratory distress syndrome (ARDS), upper airway obstruction, aspiration pneumonia, and bacteremia.

CASE SUMMARY

A 1.5-year-old male intact Beagle presented shortly after being involved in a household fire. Upon arrival the dog was diagnosed with ARDS and demonstrated acute neurological signs (eg, obtundation and seizures). Treatment included mechanical ventilation, temporary tracheostomy, and intensive supportive care. During hospitalization, the dog suffered multiple complications including prolonged neurological abnormalities, aspiration pneumonia, and bacteremia. The dog recovered over a 16-day period.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first description of extensive management of a patient suffering both neurological and respiratory complication due to smoke inhalation, and details the steps that were taken to achieve a successful outcome.

Basics of mechanical ventilation for dogs and cats

Respiratory failure may occur due to hypoventilation or hypoxemia. Regardless of the cause, emergent anesthesia and intubation, accompanied by positive pressure ventilation, may be necessary and life saving. Long-term mechanical ventilation requires some specialized equipment and knowledge; however, short-term ventilation can be accomplished without the use of an intensive care unit ventilator, and can provide oxygen supplementation and carbon dioxide removal in critical patients.