Seizures in 3 juvenile dogs after intravenous anesthetic drug withdrawal during weaning from mechanical ventilation suspected to be a sign of iatrogenic withdrawal syndrome.

OBJECTIVE: To describe seizure activity in juvenile dogs successfully weaned from long-term mechanical ventilation. CASE SERIES SUMMARY: Three juvenile dogs (all approximately 3 months old) underwent long-term mechanical ventilation with IV anesthesia for suspected noncardiogenic pulmonary edema. Within 24 hours of extubation and within 10 hours of discontinuing midazolam continuous infusions, all dogs experienced seizures, which is 1 sign of iatrogenic withdrawal syndrome. Each dog was treated with an anticonvulsant protocol, and none experienced seizures after being discharged. NEW OR UNIQUE INFORMATION PROVIDED: Each dog received IV anesthesia, including fentanyl, dexmedetomidine, midazolam, and propofol, during mechanical ventilation and subsequently experienced seizures after successful weaning from mechanical ventilation. Juvenile dogs may be at risk for seizures after weaning from mechanical ventilation and IV anesthesia. Neurological monitoring and further research into an appropriate weaning protocol may prove beneficial in juvenile dogs requiring prolonged anesthesia.

A retrospective study of positive pressure ventilation in 58 dogs: indications, prognostic factors and outcome.

OBJECTIVES: To assess the usefulness of clinical and clinicopathological parameters as prognostic markers of survival in dogs undergoing positive pressure ventilation. METHODS: Retrospective study of case records of 58 client-owned dogs undergoing positive pressure ventilation. Dogs were divided into two groups; inadequate oxygenation due to pulmonary parenchymal disease (Group 1) and inadequate ventilation (Group 2). RESULTS: Median duration of positive pressure ventilation was 30 (range 10 to 136) hours. Survival rate was 32% (19 dogs). Survivors were significantly younger (P<0·005) and had significantly higher (P<0·002) median PaO2 /FiO2 ratio at 4 to 12 hours postinitiation of positive pressure ventilation, and immediately before weaning (P<0·006) compared to non-survivors. A receiver operator characteristics analysis of PaO2 /FiO2 immediately before weaning as predictor of survival had an area under the curve of 0·76 (95% confidence interval 0·54 to 0·97), with optimal cut-off point of 252 mmHg, corresponding to a sensitivity and specificity of 0·80 and 0·79, respectively. The survival rates of dogs with PaO2 /FiO2 less than 200 mmHg at 4 to 12 hours postinitiation of positive pressure ventilation, or immediately before weaning were 15% (3/20 dogs) and 6% (1/16 dogs), respectively. CLINICAL SIGNIFICANCE: The PaO2 /FiO2 ratio is an early prognostic indicator of successful weaning in dogs undergoing positive pressure ventilation.

Indication, management, and outcome of brachycephalic dogs requiring mechanical ventilation.

OBJECTIVES: To evaluate the frequency, and need for mechanical ventilation (MV) in a population of brachycephalic dogs (BD) compared with non-BD. Also, to describe the pre-MV abnormalities, ventilator settings used, the cardiovascular and pulmonary monitoring results and complications encountered in the same BD population. In addition, we sought to identify factors associated with successful weaning and describe outcomes of BD requiring MV. DESIGN: Retrospective observational study (1990-2008). SETTING: University Small Animal Teaching Hospital. ANIMALS: Fifteen BD managed with MV. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Signalment, indication for MV, ventilator settings, arterial blood gas values, duration of MV, complications, and outcome were recorded for each patient enrolled in study. BD were more likely to receive MV than non-BD (P=0.036). Out of the 15 dogs that fulfilled the inclusion criteria 7 (47%) underwent MV for impending respiratory fatigue, 6 (40%) for hypoxemia and 2 for hypercapnea. The most common underlying disease was aspiration pneumonia. Duration of MV ranged from 2 to 240 hours (median 15 hours). Seven patients were weaned (47%). Seven dogs had a temporary tracheostomy tube and 5 of them (71%) were weaned. Dogs that were weaned had a significantly greater preweaning trial PaO2/FiO2 ratio than those that were not (359 ± 92 versus 210 ± 57 mm Hg, P=0.025). No significant difference for weaning success between dogs with and those without a tracheostomy was detected (P=0.132). The discharge rate was 27% (all from the respiratory fatigue group). CONCLUSION: Among all dogs admitted to ICU, BD were more likely to receive MV than non-BD. Aspiration pneumonia was frequently identified as the underlying cause of respiratory compromise. The survival rate for BD undergoing MV was not markedly different from previous studies. Weaning of BD from MV may be facilitated by employing preemptive strategies such as performing tracheostomy tube placements.

Outcome and medical management in dogs with lower motor neuron disease undergoing mechanical ventilation: 14 cases (2003-2009).

OBJECTIVE: To describe the application of intermittent positive pressure ventilation (IIPV) in dogs with lower motor neuron disease (LMND). DESIGN: Multi-institutional, retrospective study (2003-2009). SETTING: Intensive care units at multiple university teaching hospitals. ANIMALS: Fourteen dogs with LMND that underwent IIPV. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The ventilatory logs of 4 teaching hospitals were searched for dogs undergoing IIPV in association with a diagnosis of acute LMND. The medical records were evaluated for signalment, specific LMND, ventilatory management and duration, complications associated with ventilation, duration of hospitalization, and outcome. Descriptive statistics were used as indicated. Fifteen records were evaluated, 1 dog was excluded since it experienced cardiopulmonary arrest (CPA) before commencement of IIPV. The median age was 7.0 years (range 10 mo to 12 y). There were 5 Labrador retrievers, 4 mixed breeds, and 5 other breeds were each represented once. Five dogs were diagnosed with myasthenia gravis, 4 dogs with polyradiculoneuritis, and 5 dogs had an undetermined LMND. Clinical signs of weakness before ventilation were present for a median of 36 hours (range 6 h to 14 d). Dogs were ventilated for a median of 109 hours (range 5-261 h). Nine dogs had temporary tracheostomies performed, and 8 dogs received nutritional support. Five dogs developed ventilator associated pneumonia. Six dogs were successfully weaned from the ventilator with a median ventilatory time of 49 hours (range 25-192 h). Three dogs survived to discharge. No single LMND was associated with a better outcome. CONCLUSIONS: High euthanasia rates and iatrogenic complications limit the ability to accurately prognosticate for affected dogs in this retrospective study, but in dogs with LMND that is severe enough to require IIPV, support may be required days to weeks.

Principles of mechanical ventilation.

Mechanical ventilation is an enormous undertaking for a veterinary hospital in general and for any patient in particular. It is a team effort requiring large amounts of space, supplies, labor, and time. It requires committed owners and clinicians who communicate clearly with each other. It also requires a significant financial commitment initially from the hospital to obtain the equipment and expertise and then from the owner to maintain the patient. All members of the patient care team should have a basic understanding of respiratory physiology and ventilator mechanics. Clear goals for therapy and end points should be established. If they cannot be met, the goals should be reassessed in light of changes in patient condition. Weaning may be difficult and long, but once successful, it is most rewarding for the patient, family, clinician, and team.

Weaning from mechanical ventilation.

Patients that require positive pressure ventilation to maintain sufficient alveolar ventilation or pulmonary gas exchange may eventually reach a point in the course of their care wherein mechanical ventilation is no longer necessary. This process of transferring the work of breathing from the ventilator back to the patient is referred to as ventilator weaning. The term "ventilator weaning" may be used to refer to all methods by which this transfer of workload may be accomplished. In many patients, particularly those with short-lasting or readily correctable causes of respiratory insufficiency (e.g., general anesthesia), the discontinuation of positive pressure ventilation may be easily achieved. Indeed, in patients awakening from general anesthesia, the axiom "awake enough to blink, awake enough to breath" may prove to be a sufficient guideline. However, in those patients requiring long-term mechanical ventilatory support, the process can prove to be both frustrating and exceptionally challenging. It is of crucial importance to identify those patients that may be successfully weaned because of both the financial impact of prolonged intensive care unit hospitalization and the risks imposed on the patient by the process of positive pressure ventilation. To be able to predict which patients may be ready to be weaned from the ventilator requires an understanding of the balance between the work of breathing (ventilatory load) and the ability of the patient's respiratory pump to meet those needs (ventilatory capacity). The management of patients experiencing difficulty during the weaning process requires that the clinician recognize imbalances between ventilatory load and capacity and to correct these imbalances once identified.