Respiratory acid-base disorders

Haematological and blood biochemical alterations associated with respiratory disease in calves

Respiratory diseases of cattle, particularly in young animals, represent the most important health and economic problem of cattle rearing. The aim of the present study was to evaluate the changes of selected blood indices in 25 calves aged 2–9 months suffering from etiologically undifferentiated chronic respiratory diseases. Blood samples were analysed for haematological indices and selected serum biochemistry variables. The results found in sick animals were compared with results from 25 healthy animals of the same age, housing and feeding system. Significant differences in means between the groups of clinically healthy and sick calves were found in 13 out of 24 evaluated indicators. In sick animals we found significantly higher mean concentrations of haemoglobin and total number of white blood cells (P < 0.05 and P < 0.01, respectively), as well as higher mean activity of AST and LDH (P < 0.01), concentrations of total proteins and total immunoglobulins (P < 0.001). Significantly lower mean values were recorded in the serum concentrations of albumin, creatinine and glucose (P < 0.001), as well as in the concentration of Mg (P < 0.01), P (P < 0.001), Fe and Zn (P < 0.05). The presented results suggest the effect of respiratory diseases in calves on several changes of haematological and selected serum biochemical indicators. They indicate that respiratory diseases did not lead only to direct disturbance of gas exchange and acid-base balance, but they also indirectly affect some other variables of blood biochemistry.

Evaluation of pulmonary dysfunctions and acid-base imbalances induced by Chlamydia psittaci in a bovine model of respiratory infection

Background

Chlamydia psittaci (Cp) is a respiratory pathogen capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection. To elucidate the pathogenesis of this infection, a translational large animal model was recently introduced by our group. This study aims at quantifying and differentiating pulmonary dysfunction and acid–base imbalances induced by Cp.

Methods

Forty-two calves were grouped in (i) animals inoculated with Cp (n = 21) and (ii) controls sham-inoculated with uninfected cell culture (n = 21). For pulmonary function testing, impulse oscillometry, capnography, and FRC (functional residual capacity) measurement were applied to spontaneously breathing animals. Variables of acid–base status were assessed in venous blood using both (i) traditional Henderson-Hasselbalch and (ii) strong ion approach.

Results

Both obstructive and restrictive pulmonary disorders were induced in calves experimentally inoculated with Cp. Although disorders in respiratory mechanics lasted for 8–11 days, the pattern of spontaneous breathing was mainly altered in the period of acute illness (until 4 days post inoculation, dpi). Expiration was more impaired than inspiration, resulting in elevated FRC. Ventilation was characterised by a reduction in tidal volume (−25%) combined with an increased percentage of dead space volume and a significant reduction of alveolar volume by 10%. Minute ventilation increased significantly (+50%) due to a compensatory doubling of respiratory rate. Hyperventilatory hypocapnia at 2–3 dpi resulted in slightly increased blood pH at 2 dpi. However, the acid–base equilibrium was additionally influenced by metabolic components, i.e. the systemic inflammatory response, all of which were detected with help of the strong ion theory. Decreased concentrations of albumin (2–10 dpi), a negative acute-phase marker, resulted in a decrease in the sum of non-volatile weak acids (A_tot), revealing an alkalotic effect. This was counterbalanced by acidic effects of decreased strong ion difference (SID), mediated by the interplay between hypochloraemia (alkalotic effect) and hyponatraemia (acidic effect).

Conclusions

This bovine model was found to be suitable for studying pathophysiology of respiratory Cp infection and may help elucidating functional host-pathogen interactions in the mammalian lung.

A sub-Tenon's capsule injection of lidocaine induces extraocular muscle akinesia and mydriasis in dogs

The effect of local anaesthetic on the extraocular muscles was investigated in dogs by injecting lidocaine into the space between Tenon's capsule and the sclera. A cross-over design was used with both eyes from five Beagle dogs randomly injected, under general anaesthesia, with 1 mL of 2% lidocaine (1 mL-lidocaine group), 2 mL of 2% lidocaine (2 mL-lidocaine group) or 2 mL of normal saline (control group). Each eye was assigned to all treatments with a minimum 14 day interval between injections. Changes in eye position, pupil diameter, and intraocular pressure (IOP) were evaluated during the procedure. All eyes in the 2 mL-lidocaine group exhibited akinesia and mydriasis (pupil diameter >10mm) with an onset time of 6.5 ± 4.9 and 4.2 ± 4.3 min, respectively. In the 1 mL-lidocaine group, akinesia was induced in nine eyes and mydriasis occurred in seven eyes at 10.7 ± 5.8 and 5.4 ± 2.4 min after the injection, respectively. No changes in eye position or pupil diameter were observed in the control group. Akinesia was maintained for 44.3 ± 26.7 min in the 1 mL-lidocaine group and for 88.5 ± 17.2 min in the 2 mL-lidocaine group. Duration of mydriasis was 51.7 ± 28.9 min in the 1 mL-lidocaine group and 82.9 ± 15.6 min in the 2 mL-lidocaine group. Marked chemosis and sub-conjunctival haemorrhage occurred in 16/30 and 15/30 eyes, respectively. No significant change in IOP was observed between the mean pre- and post-injection values in all groups. These results suggest that a sub-Tenon's injection of 2 mL of 2% lidocaine provided effective extraocular muscle akinesia and mydriasis in dogs.

Influence of the wing-of-the-nostrils correction procedure on the change of the acid-base balance parameters and oxygen concentration in the arterial blood in French bulldogs

Brachycephalic syndrome develops as a result of a specific build of splanchnocranium. In dogs of brachycephalic breeds, an impairment of correct gas exchange occurs. 5 French bulldogs at the age of 11-14 months, which suffered from continuous mixed-type dispnoea and lowered effort tolerance, were examined. Apart from the above-mentioned symptoms, the occurrence of strong external nostril stenosis was noted in the clinical examination. The symptoms observed together with the nostril stenosis indicated a possibility of an occurrence of the brachycephalic syndrome. 1 ml of full blood was drawn from the femoral artery. Acid-base balance parameters were determined in the arterial blood: pH, pCO2, HCO3-, and pO2. The wing-of-the-nostrils correction procedure were carried out in general anaesthesia. In premedication, the patients received medetomidine and after 15 minutes, fentanyl together with atropine. The induction of propofol was carried out. After four weeks from the procedure, blood was collected and the acid-base balance and pO2 parameters were again determined. The obtained values of the acid-base balance and pO2 parameters showed a noticeable influence of the wing-of-the-nostrils correction procedure on the values of the parameters determined. The results of the blood gasometry obtained prior to the procedure clearly indicate the occurrence of respiratory acidosis. The correction of wings of the nostrils significantly influenced saturation of the arterial blood with oxygen and the symptoms of dispnoea observed by the owners and episodes of apnoea and the loss of consciousness entirely subsided.

Development of a retrobulbar injection technique for ocular surgery and analgesia in dogs

OBJECTIVE

To develop and compare 3 techniques for retrobulbar injection of local anesthetic agents for ocular surgery and analgesia in dogs.

DESIGN

Prospective study.

ANIMALS

17 dogs (including 9 cadavers).

PROCEDURES

Inferior-temporal palpebral (ITP), perimandibular, and combined superior-inferior peribulbar injection techniques were compared by assessing the distribution of latex after injection into the orbits of 5 canine cadavers; magnetic resonance imaging (MRI) evaluation of the distribution of contrast agent after injection in the retrobulbar space of 4 canine cadavers; and assessment of the efficacy and MRI evaluation of the anatomic distribution of injections of a lidocainecontrast agent mixture in 4 anesthetized, nonrecovery dogs. By use of the preferred technique (ITP), the ocular effects of lidocaine anesthesia were evaluated in 4 dogs; during a 2-week period after treatment, dogs underwent ophthalmic examination, Schirmer tear testing (STT), intraocular pressure (IOP) measurement, and Cochet-Bonnet esthesiometry.

RESULTS

Of the 3 techniques, the ITP technique was the preferred method for retrobulbar administration of anesthetic agent in dogs because it was efficacious (pupil dilation and central rotation of the globe achieved in all eyes), easiest to perform, and provided thorough coverage of the intraconal retrobulbar space without complication. During the 2-week follow-up period, the ITP injection did not significantly affect STT, IOP, or Cochet-Bonnet esthesiometry values in dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, retrobulbar administration of anesthetic agents via the ITP technique is a potential alternative to systemic administration of neuromuscular blocking agents for ophthalmic surgery and provides the additional benefit of local ocular analgesia.