Application of Airway Pressure Therapy in Veterinary Critical Care: Part I: Respiratory Mechanics and Hypoxemia

Over the past several decades, recognition of acute respiratory failure as the cause of death in patients suffering from various clinical conditions has prompted aggressiv investigation into the area of respiratory physiology and supportive respiratory care. With the evolution of emergency medicine and critical care services in both human and veterinary medicine, many patients previously considered unsalvageable due to the severity of their underlying disease are now being resuscitated and successfully supported, creating a new population of critically ill patients. Where only a decade ago these patients would have succumbed to their underlying disease, they now survive long enough to manifest the complications of shock and tissue injury in the form of acute respiratory failure. Investigation into the pathophysiology and treatment of this acute respiratory distress syndrom (ARDS) has facilitated increased clinical application of respiratory theerapy and machanical ventilation.¹ The purpose of this paper is to provide a basic review of respiratory mechanics and the pathophysiology of hypoxemia as they relate to airway pressure therapy in veterinary patients and to review the use of airway pressure therapy in veterinary patients This paper is divided into two parts; part I reviews respiratory mechanics and hypoxemia as they apply to respiratory therapy, while part II deals specifically with airway pressure therapy andits use in clinical cases.     

Magnesium in the 1990's: Implications for Veterinary Critical Care

Magnesium is the second most abundant intracelular cation, exceeded only by potassium. The majority of magnesium is found in bone and muscle. This cation is required for many metabolic functions, most notably as a coenzyme for the sodium-potassium ATPase pump. Magnesium functions to maintain the electrolyte gradient across all membranes. Interference with this gradient may result in changes in the resting membrane potential and disturbances in repolarization, resulting in cardiovascular and neuromuscular abnormalities.
Hypomagnesemia may be the most underdiagnosed electrolyte disorder. Incidence rates greater than 50 percent have been reported in critically ill human patients. Currently there is little or no information available regarding the incidence and significance of hypomagnesemia in hospitalized animals. Causes of magnesium deficiency can be divided into four general categories: gastrointestinal, renal, endocrine and miscellaneous. The diagnosis of magnesium depletion can be difficult since less than one percent of total body magnesium is located in serum. Alternative methods of evaluating magnesium status include determining ultrafilterable magnesium levels, mononuclear blood cell magnesium levels or by quantifying magnesium retention of an administered loading dose.     

Sound Pressure Levels in 2 Veterinary Intensive Care Units

Background

Intensive care units (ICUs) in human hospitals are consistently noisy environments with sound levels sufficient to substantially decrease sleep quality. Sound levels in veterinary ICUs have not been studied previously, but environmental sound has been shown to alter activity in healthy dogs.

Hypothesis

Veterinary ICUs, like those in human medicine, will exceed international guidelines for hospital noise.

Animals

NA.

Methods

Prospective, observational study performed consecutively and simultaneously over 4 weeks in 2 veterinary ICUs. Conventional A‐weighted sound pressure levels (equivalent continuous level [a reflection of average sound], the sound level that is exceeded 90% of the recording period time [reflective of background noise], and maximum sound levels) were continuously recorded and the number of spikes in sound >80 dBA were manually counted.

Results

Noise levels were comparable to ICUs in human hospitals. The equivalent continuous sound level was higher in ICU1 than in ICU2 at every time point compared, with greatest differences observed on week day (ICU1, 60.1 ± 3.7 dBA; ICU2, 55.9 ± 2.5 dBA, P < .001) and weekend nights (ICU1, 59.9 ± 2.4 dBA; ICU2, 53.4 ± 1.7 dBA, P < .0001) reflecting a 50% difference in loudness. Similar patterns were observed for the maximum and background noise levels. The number of sound spikes was up to 4 times higher in ICU1 (162.3 ± 84.9 spikes) than in ICU2 (40.4 ± 12.2 spikes, P = .001).

Conclusions and Clinical Importance

These findings show that sound in veterinary ICUs is loud enough to potentially disrupt sleep in critically ill veterinary patients.     

Alternating one lung ventilation using a double lumen endobronchial tube and providing CPAP to the non-ventilated lung in a dog

Introduction This case report describes the anaesthetic management of exploratory thoracoscopy and alternating one lung ventilation (OLV) in a dog with a pulmonary bulla, and the application of continuous positive airway pressure (CPAP) to the non‐ventilated lung for preventing and treating hypoxia. Case history A 6‐year‐old, male castrated Border collie was scheduled for exploratory thoracoscopy to investigate spontaneous pnemothorax that had not resolved with repeated suction. Specific requirements for the thoracoscopy were alternating OLV to allow the surgical access to the right middle lobe and its removal, and the examination of the left hemithorax to rule out the presence of other lesions. Diagnosis and management Selective lung ventilation was performed with a double lumen endobronchial tube (DLT), inserted under endoscopic guidance. After a short period of two lung ventilation during preparation of the surgical field, alternating OLV was performed, combining CPAP, provided to the non‐ventilated lung via a Mapleson D breathing system, and positive end‐expiratory pressure (PEEP) applied to the ventilated lung. Left OLV occurred first and resection of the right middle pulmonary lobe was successfully performed; right OLV followed to allow the examination of the left hemithorax. Discussion and conclusions The combination of CPAP and PEEP resulted in a satisfactory intra‐operative management of hypoxemia. Alternating OLV can be performed successfully by using a DLT. CPAP, commonly employed in human medicine, should be considered an important tool in the anaesthetic management of OLV in small animals.     

补液疗法在兽医临床上的应用技术及注意问题

兽医临床上的补液疗法主要适用于腹泻、大出血后,因畜体脱水、失盐引起的血液浓缩,微循环瘀血、脑心灌注不足时,用以补充循环血液量,改善血液循环;在心、肺、肾功能发生改变时,用以调节心、肺、肾功能,增强机体保水力,促进水盐代谢功能的动态平衡;在脱水疾病因丢失电解质,渗透压发生改变时,用以纠正体液渗透压;在多种原因引起中毒时,用以提高机体的解毒能力,稀释血液中的毒素,促进毒素排出。由此可见,补液在兽医临床诊疗中具有十分重要的作用。     

The recognition and treatment of the intermediate syndrome of organophosphate poisoning in a dog

Objective: To discuss a new clinical presentation of organophosphate toxicity called the intermediate syndrome in a dog. Case summary: A mixed breed dog presented with generalized weakness, hypoventilation and hypoxemia. The weakness was most marked in the thoracic limbs, cervical and respiratory muscles. The history revealed a likely exposure to an organophosphate compound. The other dog in the household demonstrated mild clinical signs of organophosphate toxicity. A blood cholinesterase level was markedly reduced. Therapy included placement of a tracheostomy tube and mechanical ventilation. The dog gradually improved over the following 8 days but had persistent cervical ventroflexion for a total of 4 weeks. New or unique information provided: Organophosphate toxicity can present as a paralysis following the acute cholinergic crisis. The muscular weakness predominantly affects the thoracic limb and neck muscles but cranial nerve deficits can also occur. Dogs can die from the associated respiratory depression. Oxime therapy is indicated in the treatment of this syndrome.     

Photobiomodulation Therapy in Veterinary Medicine: A Review

Laser therapy, or photobiomodulation, has rapidly grown in popularity in human and veterinary medicine. With a number of proposed indications and broad, sometimes anecdotal, use in practice, research interest has expanded aimed at providing scientific support. Recent studies have shown that laser therapy alters the inflammatory and immune response as well as promotes healing for a variety of tissue types. This review will cover the history of the modality, basic principles, proposed mechanisms of action, evidence-based clinical indications, and will guide the practitioner through its application in practice.