Anaesthesia In Dorsal Recumbency Research Articles

Increased body condition score has a detrimental effect on arterial oxygen tension and increases the risk of hypoxaemia in anaesthetised horses

SummaryBackgroundImpaired oxygenation during anaesthesia can be detrimental. Bodyweight and body shape influence arterial oxygen tension (PaO2) but the effect of body condition score (BCS) has not been investigated.ObjectivesTo examine the effect of BCS on respiratory indices.Study designRetrospective.MethodsIn total, 524 anaesthetic records were reviewed. Records from healthy adult horses under isoflurane anaesthesia in dorsal recumbency, receiving controlled mechanical ventilation, with complete ventilation and arterial blood gas data and BCS assessment by one person (KL) were included in data analysis. Data were analysed using student's t‐test, Mann–Whitney U test, chi‐squared analysis and logistic regression.ResultsIn total, 135 records for 85 horses with BCS <6/9 (Group N) and 50 horses with BCS ≥6/9 (Group O) met the inclusion criteria. Overall, there was a strong negative correlation between BCS and PaO2 (Spearman's r = 0.72, p < 0.001). Group O had significantly lower PaO2 (112 [50–546 mmHg]) compared to Group N (380 [65–658 mmHg], p < 0.001) which remained when horses were further categorised by bodyweight >500 kg (118 mmHg vs. 390 mmHg, p < 0.001) and <500 kg (160 mmHg vs. 451 mmHg, p < 0.04). Group O were 34 times more likely to be hypoxaemic (PaO2 < 100 mmHg) compared to Group N (χ2 = 34.39, p = 0.03). Alveolar dead space fraction was greater in Group O (0.27 [0.10–0.41]) versus Group N (0.24 [0.12–0.35]), p < 0.001. Multivariate logistic regression analysis identified a significant association between PaO2 and bodyweight (p = 0.01), alveolar dead space fraction (p = 0.005) and BCS (p < 0.001).Main limitationsRetrospective design.ConclusionsBody condition score ≥6/9 has a detrimental effect on PaO2, alveolar dead space fraction and is a risk factor for hypoxaemia in healthy anaesthetised horses in dorsal recumbency.

Postcastration adhesions: clinical signs, diagnosis, treatment and prognosis in 20 horses

The main goal of this short communication is to report the clinical signs, diagnostic modalities, surgical treatment and prognosis associated with postcastration adhesions. Twenty horses, castrated on average 30 months...

Effects of general anaesthesia in dorsal recumbency with and without vatinoxan on bronchoalveolar lavage cytology of healthy horses

Pneumonia is one of the potential complications of general anaesthesia in horses. Anaesthesia is known to increase neutrophils in bronchoalveolar lavage fluid (BALF) of horses after lateral recumbency, but studies after dorsal recumbency are lacking. Our primary aim was to determine when lung inflammation reaches its maximum and how rapidly BALF cytology returns to baseline after anaesthesia in dorsal recumbency. A secondary aim was to investigate the possible effect of vatinoxan, a novel drug, on the BALF cytology results.Six healthy experimental horses were enrolled in this observational crossover study. The horses were subject to repeated BALF and blood sampling for 7 days after general anaesthesia with two treatment protocols, and without anaesthesia (control). During the two treatments, the horses received either medetomidine-vatinoxan or medetomidine-placebo as premedication, and anaesthesia was induced with ketamine-midazolam and maintained with isoflurane for 1h in dorsal recumbency. The differences in BALF and blood variables between the two anaesthesia protocols and control were analysed with repeated measures analysis of variance models.In this study, anaesthesia in dorsal recumbency resulted in no clinically relevant changes in airway cytology that could be differentiated from the effect of repeated BALF sampling. No differences in BALF matrix metalloproteinase gelatinolytic activity could be detected between the two treatments or the control series. Marked increase in serum amyloid A was detected in some animals. Vatinoxan as premedication did not consistently affect lung cytology or blood inflammatory markers after anaesthesia.

Cardiorespiratory effects of a 7° reverse Trendelenburg position in anaesthetized horses: a randomized clinical trial

ObjectiveTo evaluate the cardiorespiratory effects of a 7° reverse Trendelenburg position (RTP) in anaesthetized horses. Study designRandomized, non-blinded clinical trial. AnimalsA total of 125 horses undergoing elective surgery in dorsal recumbency. MethodsHorses were allocated to one of three weight classes and assigned to be positioned either on a horizontal table or on a table in 7° RTP, according to a randomized block design. In all horses, anaesthesia was maintained with isoflurane in oxygen and a constant rate infusion of romifidine. All horses were mechanically ventilated throughout anaesthesia, and routine cardiovascular monitoring and arterial blood gas analysis were performed at 15-minute intervals and relevant variables calculated. Data from the first 60 minutes of anaesthesia were compared between both positions using a mixed model analysis of variance. ResultsA significant interaction was found between position and weight class for the alveolar to arterial oxygen tension gradient and F-shunt: these variables were lower in RTP than in horizontal position in the two lowest weight classes and vice versa in the highest weight class. Arterial oxygen tension and oxygenation indices were significantly worse in the horses in the higher weight classes. Conclusions and clinical relevanceA 7° RTP did not result in clinically relevant changes in gas exchange or cardiovascular function. Horses with a higher body weight are at increased risk for hypoxaemia during anaesthesia in dorsal recumbency.

Medial patellar ligament splitting in horses with upward fixation of the patella: A long-term follow-up.

Medial patellar ligament splitting (MPLS) has been shown to be a highly effective and minimally invasive treatment for upward fixation of the patella (UFP) in horses. However, long-term follow-up results of this procedure have not previously been reported. To evaluate the long-term resolution of UFP following MPLS and provide information on complications and recurrence. Retrospective case series. Data were collected from horses that underwent MPLS between 1999 and 2013. All cases had a confirmed diagnosis of UFP that had not responded to conservative therapy. Data were collected from medical records, including follow-up visits and through telephone conversations with the owner, trainer or referring veterinarian. A total of 85 horses were included. Fifty-eight horses (68%) had surgery under general anaesthesia in dorsal recumbency, while 27 horses (32%) underwent standing surgery and 97.6% had complete resolution of the UFP immediately after surgery or within the 2 week rehabilitation period. Two cases (2.4%) had only unilateral resolution after bilateral surgery, even after the procedure was repeated. The majority of cases (90.5%) were followed up at least 3 and up to 14 years after surgery. No short- or long-term complications were reported. No recurrence of UFP was observed in the horses that resumed exercise after surgery. Medial patellar ligament splitting is a highly effective and minimally invasive surgical procedure to treat UFP when conservative treatment is unsuccessful. In addition, it allows for a very rapid return to sports activity. No short- or long-term complications were observed and no recurrence of this condition was noted.

Post anaesthetic myelopathy in the horse: a case report

The first case of post anaesthetic myelopathy in a horse is described. A two year old 530 kg Shire stallion underwent surgical removal of a granuloma in the ventral sternal region under general inhalation anaesthesia in dorsal recumbency. Total duration of the operation was 85 min. The anaesthesia was uneventful except for profuse sweating and arterial hypertension observed during the whole period. During recovery the horse was not able to stand, and flaccid paralysis of hind limbs, absence of reaction to an induced pain stimulus on the hind limbs and no patellar or anal reflex was recorded; in addition, tail tonus was weak. Panniculus reflex was absent distally from the 17<sup>th</sup> intercostal space. Head, neck and front limb movement was not affected. The horse did not respond to treatment by intravenous administration of dexamethasone, hypertonic or isotonic saline. The status deteriorated and the horse was euthanised 4 h after the end of anaesthesia. The main pathological findings were haemorrhage, oedema and malacia of L5–L6 spinal cord segments and cauda equina. Histological examination of the spinal cord revealed haemorrhage and areas of necrosis predominantly in the grey matter of L5 and L6 segments. Impairment of spinal cord perfusion due to haemodynamic changes associated with dorsal recumbency and general anaesthesia is presumed. Predisposition factors could include young age, dorsal recumbency and high weight.  

Ligation in Castration of the Male Horse Using a TA‐30 Stapler

Reasons for performing the studyMost complications in equine castrations result from insufficient ligation and contamination.ObjectivesStapling instruments reduce tissue handling, decrease surgical time, minimise contamination and provide secure visceral and vascular closure when used correctly. Using a stapler device might therefore increase ligation security and decrease contamination, and by this, reduce the complication rate seen in routine castration.Study designThe applicability and safety of a TA‐30 premium stapler as a ligation method in castration of the horse was tested in 15 horses under general anaesthesia in dorsal recumbency. Three horses were cryptorchids, one horse suffered a scirrous chord, and one horse suffered an infectious orchitis.MethodsThe vaginal process was approached inguinally. A noncutting emasculator was applied to compress the closed vaginal process. Consecutively a TA‐30 Premium stapler was applied to the compressed site. The distal part of the vaginal process was then removed, the stapler device was released and the incision was closed. The TA‐30 stapler accommodates 3 different staple cartridges of 30 mm width, accommodating 1.0 to 2.5 mm tissue thickness. The thickness of the vaginal process after compression was measured to be 1.0 mm (0.9–1.1 mm) in 10 fresh specimens. The 30‐V3 cartridges (triple row, 1 mm closed diameter) were chosen in 9 horses with smaller vaginal processes and the 30‐3.5 cartridges (double row 1.5 mm closed diameter) in 6 other horses with larger vaginal processes.ResultsAll horses recovered without intra‐ or post operative complications.ConclusionsA TA‐30 stapler is a safe ligation instrument in equine castrations. The use of titanium staples may reduce infection rate in routine castrations, even more in ligation of precontaminated vaginal processes in cases of post operative haemorrhage control after practice castrations or in closing the vaginal process after the removal of an infected testis or scirrous chord.Ethical animal research: Ethical committee oversight not currently required by this congress: procedures were performed as part of clinical investigations. Explicit owner informed consent for participation in this study was not stated. Sources of funding: None. Competing interests: None.

Use of continuous positive airway pressure (CPAP) to optimise oxygenation in anaesthetised horses – a clinical study

Hypoxaemia is a common problem during equine anaesthesia. Continuous positive airway pressure (CPAP) is a ventilation mode routinely employed in man to overcome hypoxaemia but has not been objectively assessed in horses. To test the effects of CPAP on oxygenation and its indices in anaesthetised horses in a clinical setting. Twenty-four healthy horses requiring anaesthesia in dorsal recumbency were anaesthetised using a standard protocol. Following orotracheal intubation and connection to an anaesthetic machine capable of applying CPAP, horses were randomly allocated to ventilate at physiological airway pressure measured at the airway opening (Group PAP) or to receive CPAP of 8 cmH2O (Group CPAP). Arterial blood gas analysis was performed as soon as arterial cannulation was achieved and 30, 60 and 90 min after induction. If PaCO2 increased above 9.31 kPa controlled ventilation was initiated. Groups were compared using a general linear model. Horses receiving CPAP had significantly higher PaO2 and calculated oxygen indices than horses receiving PAP. No significant differences in ventilation indices were observed between the 2 groups. Eight horses receiving PAP and 5 receiving CPAP required controlled ventilation. No differences in dobutamine requirements or mean arterial pressures were recorded. Continuous positive airway pressure of 8 cmH2O improved oxygenation indices in dorsally recumbent horses without significantly influencing ventilation. Continuous positive airway pressure reduces the incidence of hypoxaemia in anaesthetised horses. Further research is warranted to elucidate the effects of CPAP on the cardiovascular system.

Use of rigid endoscopy to evaluate vaginal haemorrhage in a rat

ENDOSCOPY provides a minimally invasive method for diagnostic sampling (eg, for biopsy, cytology or cultures) and visual examination of internal structures. This diagnostic modality is especially advantageous in small exotic...

Laparoscopic-assisted cystotomy: an experimental study in male sheep

Aim: To describe a technique of laparoscopic-assisted cystotomy in male sheep. Experimental animals: five healthy male sheep aged approximately nine months (mean weight: 39.6 ± 1.51 kg). Laparoscopy was performed on sheep placed under general anaesthesia in dorsal recumbency. A 10-mm laparoscope was inserted through the right paramedian region between the xiphoid and preputial orifice. After creation of a capnoperitoneum, grasping forceps were inserted through the left paramedian region close to the last pair of teats. The urinary bladder was elevated using grasping forceps and exteriorized through an abdominal incision. The bladder was opened extracorporeally, lavaged, closed, and then repositioned. A pigtail balloon catheter was subsequently inserted percutaneously under laparoscopic control and removed ten days later. A repeat laparoscopy was performed at 14 days after the first procedure to assess gross pathological changes. Laparoscopic-assisted cystotomy was successfully performed on all sheep. In one sheep, both the ventral and dorsal bladder walls were inadvertently perforated when placing the urinary catheter. The postoperative course was favourable: all sheep had a good appetite and showed no pathological findings during physical examination. During the repeat laparoscopy, it was observed that one sheep had developed a focal adhesion of the parietal peritoneum to the bladder catheter portal site. Laparoscopic-assisted cystotomy with catheter implantation is shown to be feasible in male sheep. This technique may be useful for removal of uroliths in patients suffering from obstructive urolithiasis opening the urinary bladder and for performing urinary diversion.

Results and complications of a novel technique for primary castration with an inguinal approach in horses

Complications associated with equine castration can have medical and financial consequences. This retrospective study investigated a novel method of castration via an inguinal approach in mature stallions and compared the incidence of complications with other methods. Castration via an inguinal approach has a low complication rate at the site of surgery compared with other castration techniques. Mature stallions (n = 238) were castrated under general anaesthesia in dorsal recumbency using an inguinal approach. The vaginal process was incised, the spermatic cord ligated twice and the testis removed. After suturing, the vaginal process and one or 2 layers of fascia, the subcutis and cutis were closed in a simple continuous pattern. Five of 238 (2.1%) horses had post operative haemorrhage and a haematoma in the scrotal region, which required additional treatment. All horses made a full recovery. Five of 238 (2.1%) of the horses had a post operative respiratory infection, which resolved with antibiotic therapy. Sixteen of 238 (8.8%) had transient signs of colic shortly after surgery. This technique of castration with an inguinal approach had a low incidence of complications at the site of surgery compared with other methods. An inguinal approach and leaving the vaginal tunic in situ may cause less soft tissue trauma than a scrotal approach.

Atelectasis causes gas exchange impairment in the anaesthetised horse

The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the 'normal' regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.