Ventilatory and Metabolic Compensation in Dogs With Acid-Base Disturbances

Relationship between Respiratory Rate, Oxygen Saturation, and Blood Test Results in Dogs with Chronic or Acute Respiratory Disease: A Retrospective Study

This study aimed to investigate the association of respiratory rate (RR), oxygen saturation (SpO2), and blood findings with respiratory disease in dogs and to compare the examination findings in the chronic and acute phases. Dogs that visited a veterinary referral hospital with respiratory symptoms were classified into the chronic disease group (GC), and those that visited the emergency veterinary hospital were classified into the acute disease group (GA). In total, 704 and 682 dogs were included in GC and GA, respectively. The RR and SpO2 were significantly higher and lower, respectively, in patients with lung disease compared to other disease sites in both groups. White blood cell counts were significantly increased in patients with lung and pleural diseases in both groups. Respiratory alkalosis and respiratory acidosis were most common in GC and GA, respectively. The C-reactive protein levels were elevated in both groups, primarily in patients with lung disease. Associations between the results of several tests for understanding and diagnosing respiratory conditions and diseases were recognized, and differences in the trends of the chronic and acute phases were clarified. These tools may be used as adjuncts to other tests for the diagnosis and monitoring of treatment responses.

Acute Anaplasma phagocytophilum infection in a pediatric domestic cat

Case summary

A domestic shorthair cat estimated to be 4-6 weeks old was presented to a referral center for evaluation of lethargy, anorexia and diarrhea for a duration of 24 h. A feline vector-borne PCR panel, as well as a blood smear, examined by a board-certified pathologist, confirmed an Anaplasma phagocytophilum infection. Morulae were identified in both feline neutrophils and eosinophils. Treatment consisted of a 21-day course of liquid doxycycline. Clinical signs rapidly resolved and were not noted to recur.

Relevance and novel information

This case demonstrates that A phagocytophilum can infect cats as young as 4-6 weeks old. Doxycycline, as the antibiotic of choice for the treatment of A phagocytophilum infections, was used. Consistent with the literature, a rapid clinical improvement was detected. Anaplasmosis should be listed as a differential diagnosis in pediatric cats suffering from acute febrile illness with potential previous tick exposure (history of living outdoors) in order to provide proper treatment.

Intraoperative fluid therapy for video-assisted ovariohysterectomy in dogs

Background

Intraoperative fluids are still poorly studied in veterinary medicine. In humans the dosage is associated with significant differences in postoperative outcomes.

Objectives

The aim of this study is to verify the influence of three different fluid therapy rates in dogs undergoing video-assisted ovariohysterectomy.

Methods

Twenty-four female dogs were distributed into three groups: G5, G10, and G20. Each group was given 5, 10, and 20 mL·kg⁻¹·h⁻¹ of Lactate Ringer, respectively. This study evaluated the following parameters: central venous pressure, arterial blood pressure, heart rate, respiratory rate, temperature, acid-base balance, and serum lactate levels. Additionally, this study evaluated the following urinary variables: urea, creatinine, protein to creatinine ratio, urine output, and urine specific gravity. The dogs were evaluated up to 26 h after the procedure.

Results

All animals presented respiratory acidosis during the intraoperative period. The G5 group evidenced intraoperative oliguria (0.80 ± 0.38 mL·kg⁻¹·h⁻¹), differing from the G20 group (2.17 ± 0.52 mL·kg⁻¹·h⁻¹) (p = 0.001). Serum lactate was different between groups during extubation (p = 0.036), with higher values being recorded in the G5 group (2.19 ± 1.65 mmol/L). Animals from the G20 group presented more severe hypothermia at the end of the procedure (35.93 ± 0.61°C) (p = 0.032). Only the members of the G20 group presented mean potassium values below the reference for the species. Anion gap values were lower in the G20 group when compared to the G5 and G10 groups (p = 0.017).

Conclusions

The use of lactated Ringer's solution at the rate of 10 mL·kg⁻¹·h⁻¹ seems to be beneficial in the elective laparoscopic procedures over the 5 or 20 mL·kg⁻¹·h⁻¹ rates of infusion.

Changes in the SIDActual and SID Effective Values in the Course of Respiratory Acidosis in Horses With Symptomatic Severe Equine Asthma-An Experimental Study

Equine asthma syndrome is an allergic, inflammatory airway disease that usually affects older horses. Respiratory acidosis is an acid-base imbalance caused by alveolar hypoventilation. The acid-base balance may be assessed using the Henderson-Hasselbalch equation as well as the Stewart model. The authors hypothesized that systemic respiratory acidosis changes the ionic concentrations affecting water dissociation. The study group included 16 Warmblood, mixed breed horses of both sexes with a history of severe equine asthma, and 10 healthy horses were used as controls. Arterial and venous blood were collected from all the horses. The pH, pO₂, and pCO₂ and HCO_3- were assessed in the arterial blood. Na, K, Cl, albumin, and P_inorganic (P_i) were assessed in the venous blood. The obtained results were used to calculate the anion gap (AG), modified AG, actual strong ion difference (SID_a), weak non-volatile acids, and effective strong ion difference (SID_e) values for all the horses. A systemic, compensatory respiratory acidosis was diagnosed in the study group. The concentration of Na in the blood serum in the study group was significantly higher, whereas the concentration of Cl was significantly lower than the values in the control group. The SID_a and SID_e values calculated in the horses from the study group were significantly higher than those in the control group. Significantly higher SID_a and SID_e values confirm the presence of ionic changes that affect water dissociation in the course of respiratory acidosis in horses. The SID_a and SID_e values may be useful in the diagnosis and treatment of respiratory acidosis in horses, which warrant further investigation.

Food engorgement in 35 dogs (2009-2013) compared with 36 dogs with gastric dilation and volvulus

The clinical features and management of food engorgement (FE) in dogs have not been previously described. This retrospective observational study describes characteristics and outcome of 35 dogs with FE, and compares features on presentation to 36 dogs with gastric dilation and volvulus (GDV). Cases were retrospectively reviewed for history, clinical findings and outcome. Gastric distension was measured by caudal gastric margin (CGM), level with lumbar vertebrae, on a lateral abdominal radiograph. Frequent characteristics of dogs with FE included tachycardia, tachypnoea, hyperproteinaemia, increased base excess (BE), mild hypernatraemia and hyperlactataemia. There was overlap in CGM between dogs with GDV (CGM range L3 to >L6) and dogs with FE (CGM range <L2 to L5-L6). In contrast to dogs with GDV, lactate concentration in dogs with FE was not associated with CGM or BE. Dogs with FE mostly received medical intervention consisting of fluid therapy and analgesia, and all dogs survived to discharge. In conclusion, dogs with FE frequently presented with acid-base and electrolyte derangements, including hyperlactataemia. While dogs with FE can have gastric distension as severe as that seen with GDV, outcome with supportive care only is excellent.

Compensation for Acid-Base Disorders

Hydrogen concentration is a critical determinant of many physiologic functions and is tightly regulated. Any alteration in acid-base equilibrium sets into motion a compensatory response by either the lungs or the kidneys. The compensatory response attempts to return the ratio between Pco₂ and [HCO₃^-] to normal and thereby minimize the pH change. A primary increase or decrease in one component is associated with a predictable compensatory change in the same direction in the other component, and the expected compensation can be estimated clinically in dogs and cats.

Blood Gas Analyzers

Acid-base and respiratory disturbances are common in sick and hospitalized veterinary patients; therefore, blood gas analyzers have become integral diagnostic and monitoring tools. This article will discuss uses of blood gas analyzers, types of samples that can be used, sample collection methods, potential sources of error, and potential alternatives to blood gas analyzers and their limitations. It will also discuss the types of analyzers that are available, logistical considerations that should be taken into account when purchasing an analyzer, and the basic principles of how these analyzers work.

[Blood gas analysis in dogs in veterinary practice. A review]

Blood gas analysis is useful to obtain information about acid-base state and gas exchange of the lung. Interpretation is based on the Henderson-Hasselbalch equation. This approach has its limitations especially in interpretation of complex disturbances of acid-base status and has been complemented by base excess and anion gap. Peter Stewart described a model of quantitative approach to the acid-base disturbances which has been further developed and is known as the strong ion approach. This model differs from the traditional approach in the assessment of metabolic disorders of acid base status. Both models complement each other but also have their advantages and disadvantages. For simple disorders of the acid-base state the Henderson-Hasselbalch approach can be used, however in complex disturbances of acid-base balance, especially with abnormalities of serum albumin and phosphate concentrations, the strong ion approach is recommended. With the understanding of both models and of the clinical presentation of blood gas abnormalities, optimal case management and therapy can be provided.

A comparison of traditional and quantitative analysis of acid-base imbalances in hypoalbuminemic dogs

OBJECTIVE

To compare the traditional (HH) and quantitative approaches used for the evaluation of the acid-base balance in hypoalbuminemic dogs.

DESIGN

Prospective observational study.

SETTING

ICU of a veterinary teaching hospital.

ANIMALS

One hundred and five client-owned dogs.

MEASUREMENTS AND MAIN RESULTS

Jugular venous blood samples were collected from each patient on admission to determine: total plasma protein (TP), albumin (Alb), blood urea nitrogen (BUN), glucose (Glu), hematocrit (HCT), Na(+) , Cl(-) , K(+) , phosphate (Pi ), pH, PvCO2, bicarbonate (HCO3 (-) ), anion gap (AG), adjusted anion gap for albumin (AGalb ) or phosphate (AGalb-phos ), standardized base excess (SBE), strong ion difference (SID), concentration of nonvolatile weak buffers (Atot ), and strong ion gap (SIG). Patients were divided in 2 groups according to the severity of the hypoalbuminemia: mild (Alb = 21-25 g/L) and severe (Alb ≤20 g/L). All parameters were compared among groups. Patients with severe hypoalbuminemia showed significant decrease in TP (P = 0.011), Atot (P = 0.050), and a significant increase in adjusted AG (P = 0.048) and the magnitude of SIG (P = 0.011) compared to animals with mild hypoalbuminemia. According to the HH approach, the most frequent imbalances were simple disorders (51.4%), primarily metabolic acidosis (84.7%) associated with a high AG acidosis. However, when using the quantitative method, 58.1% of patients had complex disorders, with SIG acidosis (74.3%) and Atot alkalosis (33.3%) as the most frequent acid-base imbalances. Agreement between methods only matched in 32 cases (kappa < 0.20).

CONCLUSIONS

The agreement between the HH and quantitative methods for interpretation of acid-base balance was poor and many imbalances detected using the quantitative approach were missed using the HH approach. Further studies are necessary to confirm the clinical utility of using the quantitative approach in the decision-making process of the severely ill hypoalbuminemic patients.

Point-of-care blood gas and electrolyte analysis in rabbits

This article outlines a practical approach for the use of blood-gas analysis in pet rabbits using the I-STAT analyzer. Sampling techniques and a theoretic approach to diagnosis are described. The following 95% RI were obtained from venous samples of 45 healthy rabbits: pH (7.245-7.533), PCO(2) (28.9-52.9 mm Hg), HCO(3) (17.0-32.5 mmol/L), total CO(2) (18-34 mmol/L), BE(ecf) (-10-8 mmol/L), AnGap (11-26 mmol/L), Na (136-147 mmol/L), K (3.4-5.7 mmol/L), Cl (93-113 mmol/L), Glu (93-245 mg/dL), BUN (9-33 mg/dL). Results from 20 arterial samples were pH (7.358-7.502), PCO(2) (29.1-36.8 mm Hg), HCO(3) (17.5-27.6 mmol/L), BE(ecf) (-7-5 mmol/L), PO(2) (75-101 mm Hg), iCa (1.67-1.85). The article also includes some conclusions obtained comparing results from healthy and ill rabbits over an 18-month period.

Acid-base status in the avian patient using a portable point-of-care analyzer

The i-STAT PCA can be used as a blood analyzer in critical avian patients, although single values must be interpreted carefully. The study of the acid-base status in companion birds is still in its infancy. Further research is needed to establish normal reference values in arterial blood gases, compare them with venous blood gas, and to determine if the formulas that deviate from small animal medicine are or are not applicable.

Making sense of blood gas results

Recent technologic advances have allowed the production and marketing of cage-side blood gas analyzers to private practitioners. The widespread use of cage-side portable blood gas analyzers in veterinary practices has increased the need to develop the basic skills of blood gas analysis as part of a tool kit for practicing veterinarians. Rapid expansion of emergency and critical care medicine as a specialty and increased numbers of veterinary emergency and veterinary specialty practices have occurred concurrently with the availability of blood gas analyzers that are affordable for private practitioners. As a result, evaluation of blood gas results is no longer an activity confined to academic institutions and has become a daily part of many practicing veterinarians' activities.

Secondary chronic respiratory acidosis in a dog following the cervical cord compression by an intradural glioma

An intradural tumor in the upper cervical region was found in a dog with quadriparesis and chronic respiratory acidosis. Surgical removal of the tumor in the atlas and intraoperative radiotherapy were attempted. The tumor was histologically diagnosed as a neural glioma. A preoperative acid-base disturbance was dramatically improved after surgery. The clinical changes appeared in this case suggest that compression of the spinal cord at this region may cause paralysis of the respiratory muscles and secondarily result in chronic respiratory acidosis following the respiratory insufficiency.

Respiratory acid-base disorders

Respiratory acid-base disorders, although infrequently diagnosed in veterinary medicine, can cause or contribute to adverse clinical outcomes. Recognition of the mechanisms and causes of respiratory acidosis and alkalosis can prompt clinical detection of the acid-base derangement, allowing for appropriate intervention.

Respiratory monitoring: arterial blood gas analysis, pulse oximetry, and end-tidal carbon dioxide analysis

The use of arterial blood gas analysis, pulse oximetry, and capnography has become commonplace in the assessment of veterinary patients. Blood gas analysis allows for the qualitative and quantitative assessment of both metabolic and respiratory acid-base problems, including the interrelationships between ventilation, oxygenation, and metabolic conditions. Blood gas analysis is a useful adjunct to clinical patient assessment and other diagnostics in determining appropriate therapy for specific and complex conditions. Both pulse oximetry and capnography are useful monitoring tools. However, they have technical limitations and cannot comprehensively evaluate patient oxygenation and ventilation. Pulse oximetry and capnography are not replacements for arterial blood gas analysis, but rather serve as adjunctive monitoring tools.