Effect of body position on feline electrocardiographic recordings

The aim of this study was to determine whether changes in body position alter feline electrocardiographic parameters. Forty-seven cats referred to the Feline Unit of the University of Bristol had electrocardiograms (ECGs) recorded. Only cats presenting in sinus rhythm were included in the study (n = 41). ECGs were recorded either as part of the investigation for potential cardiac disease (n = 38) or as a preanesthetic screen (n = 3). Standard 6-lead ECGs (leads I, II, III, aVR, aVL, and aVF) were recorded in 3 different recumbent positions in the 41 cats. Recordings were 1st made in right lateral (RL) recumbency, followed by sternal (ST) and then left lateral (LL) recumbency. Measurements were taken of the amplitude and duration of P waves and QRS complexes and duration of PQ and QT intervals from lead II was taken in the 3 different positions. Mean electrical axis (MEA) also was calculated. Repeated measures analysis of variance was performed and identified a significant difference in R wave amplitudes (P = .009) and MEA (P = .037) among the 3 different body positions. Two-tailed paired t-tests demonstrated that the R wave amplitude differed significantly both in ST (P = .025) and LL recumbency (P = .009). The mean R wave amplitude was reduced in both ST and LL recumbency when compared with RL recumbency. The MEA only was significantly different in LL recumbency (P = .037). ST and LL recumbencies should not be used for recording ECGs in cats if amplitudes and MEA are to be compared with standard references.     

Radiographic and electrocardiographic evaluation of cardiac morphology and function in captive cheetahs (Acinonyx jubatus).

In a prospective study, eight (four males and four females) healthy, adult captive cheetahs (Acinonyx jubatus) were immobilized with a combination of tiletamine-zolazepam (4 mg/kg, i.m.), administered with a remote drug delivery system, to define normal cardiac morphology and function. Standard lateral and ventrodorsal (VD) radiographs were then taken to measure heart and thorax using a metric and vertebral scale system. Standard six-lead electrocardiograms were obtained with the animals in right lateral recumbency under isoflurane anesthesia. Mean chest depth and width was 18.7 +/- 1.3 cm and 13.0 +/- 0.6 cm, respectively. The mean lateral cardiac short axis (X) was 9.1 +/- 0.6 cm. the mean cardiac long axis (Y) was 13.6 +/- 0.7 cm, and the mean lateral heart sum (X + Y) was 22.6 +/- 1.2 cm. In the VD projection, mean cardiac short axis (V) was 10.1 +/- 0.7 cm, mean cardiac long axis (W) was 14.9 +/- 1.2 cm, and the heart sum (V + W) was 24.9 +/- 1.8 cm. The vertebral heart size was 8.2 +/- 0.9. All cheetahs had sinus rhythm, and no arrhythmias were noted. Mean heart rate was 126 +/- 15 beats/min, and the mean electrical axis was 82 + 5 degrees. P waves were always positive on lead II and had a width of 0.04 +/- 0.01 sec and a height between 0.1 and 0.3 mV. PR intervals were 0.11 +/- 0.01 sec. The height of the QRS complex was 1.25 +/- 0.24 mV and the width 0.06 +/- 0.01 sec. The ST segment was 0.04 sec, and the T wave (height: 0.25 +/- 0.05 mV) was positive in all cheetahs examined. Although these cardiac and thoracic measurements were larger than those of domestic cats (Felis catus), ratios of cardiac parameters were similar in both species. Electrocardiographic findings were similar to those reported from domestic cats.     

The electrocardiogram of anesthetized captive adult emus (Dromaius novaehollandiae)

ObjectiveTo characterize the electrocardiogram (ECG) of anesthetized adult emus (Dromaius novaehollandiae).AnimalsTen clinically healthy adult emus anesthetised for routine physical examination and an electrocardiogram, for both monitoring and investigation into any evidence of cardiac disease.MethodsThe ECGs for each emu were obtained in right lateral recumbency, using a modified electrode placement that replicated the standard bipolar leads used in small mammals. Lead II was used for waveform analysis.ResultsMedian P wave amplitude was 0.55 mV (range: 0.2–0.92 mV) and P wave duration was 0.06 s (0.04–0.09 s). S wave amplitude measured 1.42 mV (0.92–2.12 mV), T wave amplitude 0.67 mV (0.16–0.83 mV) and QRS duration was 0.07 s (0.07–0.12 s). Ninety percent of the QRS complexes were of rS type.ConclusionOur study provides electrocardiographic baseline data for anesthetized adult emus.     

Evaluation of six-lead electrocardiograms obtained from dogs in a sitting position or sternal recumbency

OBJECTIVE: To compare 6-lead ECG traces in clinically normal conscious dogs in a sitting position and sternal recumbency to that of right lateral recumbency. ANIMALS: 31 healthy dogs with no history of cardiac disease. PROCEDURE: Six-lead ECGs were recorded for dogs in right lateral recumbency, a sitting position, and sternal recumbency. Q-, R-, and S-wave amplitudes as well as QRS-complex duration were measured in all leads. Additionally, P-wave amplitude and duration, PR interval, ST-segment elevation or depression, and OT interval were measured in lead II. RESULTS: Compared with measurements in right lateral recumbency, the sitting position resulted in increased Q-wave amplitude (lead III), increased R-wave amplitude (leads I and aVL), decreased R-wave amplitude (leads III and aVF), increased S-wave amplitude (lead aVR), decreased S-wave amplitude (lead aVL), increased P-wave amplitude (lead II), and a leftward shift in the mean electrical axis. Compared with measurements in right lateral recumbency, sternal recumbency resulted in decreased Q-wave amplitude (leads I, II, and aVF), increased R-wave amplitude (leads 11, III, and aVF), decreased R-wave amplitude (lead aVR), increased S-wave amplitude (lead aVR), increased P-wave amplitude (lead II), and decreased ST-segment depression (lead II). Compared with right lateral recumbency, the sitting position or sternal recumbency did not result in significant differences in PR interval, QT interval, or QRS-complex duration. CONCLUSIONS AND CLINICAL RELEVANCE: Significant changes are found in ECG measurements in the sitting position and sternal recumbency, compared with right lateral recumbency. In dogs, many ECG reference range values for right lateral recumbency are not valid for ECGs obtained in the sitting position or sternal recumbency.     

Electrocardiography of the normal domestic pet rabbit

To establish a well-tolerated technique for recording electrocardiograms (ECGs) and a reference range for the normal pet rabbit ECG, 46 healthy pet rabbits were studied. The following reference ranges were calculated. Heart rate was 198 to 330 bpm. P waves had a duration of 0.01 to 0.05 seconds and an amplitude of 0.04 to 0.12 mV. The P-R interval was 0.04 to 0.08 seconds and the duration of the QRS complex was 0.02 to 0.06 seconds. The amplitude of the R wave was 0.03 to 0.39 mV. The Q-T interval was 0.08 to 0.16 seconds. The amplitude of the T wave was 0.05 to 0.17 mV. Mean electrical axis was found to be -43° to +80°. Evidence of variation due to breed or bodyweight was not found to be significant, except for a quadratic relationship between R wave amplitude and bodyweight. The ECG recording technique used in this study for pet rabbits was well tolerated and shown to be both reliable and repeatable.     

The Electrocardiogram of Conventional and Miniature Swine (Sus scrofa)

Standard, augmented limb leads and lead V₁₀ (representing the Z axis) taken in sequence and three semi-orthogonal leads (I, aVF, and V₁₀) taken simultaneously were recorded from 43 healthy pigs. Records were analyzed for rate, rhythm, interval duration and component amplitudes. The wave form of QRS complexes were analyzed in all leads studied. P, QRS, and T vectors were calculated for the mean dorsal (frontal), sagittal, and transverse planes. study of orthogonal leads in right sternal recumbency indicated that ventricular activation is spatially oriented dorsad, sinistrad and slightly caudad. No essential difference was noticed in the conventional and miniature swine. Ventricular fibrillation induced electrically in four older pigs was a progressive, terminal event; in two newborn piglets, ventricular fibrillation induced several times was terminated in each case by spontaneous recovery to sinus rhythm.     

The Electrocardiogram, Vectorcardiogram and Spatiocardiogram in the Rabbit

Standard, augmented limb leads and three orthogonal leads (I, aVF and V₁₀) taken simultaneously were recorded from 25 rabbits. Records were analyzed for rate, rhythm, interval duration and component amplitudes. The wave forms of QRS complexes were analyzed in all leads. P, QRS, and T vectors were calculated for the mean frontal (dorsal), sagittal, and transverse planes. Study of orthogonal leads in sternal recumbency indicated that ventricular activation is spatially oriented sinistrad or dextrad, ventrad and caudad.     

Anaesthetic and cardiopulmonary effects of intramuscular morphine, medetomidine and ketamine administered to telemetered cats

The quality and duration of anaesthesia, cardiorespiratory effects and recovery characteristics of a morphine, medetomidine, ketamine (MMK) drug combination were determined in cats. Six healthy, adult female cats were administered 0.2 mg/kg morphine sulphate, 60 microg/kg medetomidine hydrochloride, and 5 mg/kg ketamine hydrochloride intramuscularly. Atipamezole was administered intramuscularly at 120 min after MMK administration. Time to lateral recumbency, intubation, extubation and sternal recumbency were recorded. Cardiorespiratory variables and response to a noxious stimulus were recorded before and at 3 min and 10 min increments after drug administration until sternal recumbency. The time to lateral recumbency and intubation were 1.9+/-1.2 and 4.3+/-1.2 min, respectively. Body temperature and haemoglobin saturation with oxygen remained unchanged compared to baseline values throughout anaesthesia. Respiratory rate, tidal volume, minute volume, heart rate, and blood pressure were significantly decreased during anaesthesia compared to baseline values. One cat met criteria for hypotension (systolic blood pressure <90 mmHg). End tidal carbon dioxide increased during anaesthesia compared to baseline values. All but one cat remained non-responsive to noxious stimuli from 3 to 120 min. Time to extubation and sternal recumbency following atipamezole were 2.9+/-1.1 and 4.7+/-1.0 min, respectively. MMK drug combination produced excellent short-term anaesthesia and analgesia with minimal cardiopulmonary depression. Anaesthesia lasted for at least 120 min in all but one cat and was effectively reversed by atipamezole.     

Validation of 2 techniques for electrocardiographic recording in dogs and cats

BACKGROUND: Standard electrocardiographic (ECG) recording in the dog and cat is commonly performed in right lateral recumbency, by connecting the ECG leads to the skin of the patient via metallic alligator clips. The jaws of the alligator clips are usually filed or flattened to reduce their uncomfortable pressure on the patient's skin. However, filed and flattened alligator clips can occasionally lose their grip to the skin, causing lead detachment during standard ECG recording. HYPOTHESIS: The aim of the study was to validate two novel ECG recording techniques ("gel" and "pads"). ANIMALS: Six-lead standard ECG recording was obtained from 42 dogs and 40 cats using the standard technique, as well as the two novel methods. METHODS: Measurements were taken of the amplitude and duration of P waves and QRS complexes, duration of PQ and QT intervals, and mean electrical axis (MEA). In each recording, five representative complexes were measured, and the results were averaged for each parameter. RESULTS: A good quality ECG recording was obtained with all the three different techniques, although a degree of wandering trace was observed in one third of cats with the "pads" technique. Bland-Altman analysis showed good agreement between the ECG values recorded with the two novel techniques and those recorded with the standard traditional technique. Furthermore, the observed differences were not clinically relevant, except for the R wave amplitude recorded with the "pads" method in cats (-0.35 to 0.37 mV). CONCLUSIONS AND CLINICAL IMPORTANCE: In conclusion, this study supports the reliability and clinical validity of the "gel" and "pads" techniques for ECG recording both in the dog and the cat, with some limitations for the "pads" technique in cats.     

Original Study: Determination of normal intra‐abdominal pressure using urinary bladder catheterization in clinically healthy cats

Objective – To establish a reference interval for intra‐abdominal pressure (IAP) measured by urinary bladder catheterization in normal cats and determine if IAP is affected by observer variation, volume of saline instillation before measurement, or subject variables of gender, positioning, body condition score, and sedation. Design – Prospective experimental study. Setting – Private referral center. Animals – Twenty healthy adult cats. Interventions – Sedation with butorphanol, midazolam, and propofol for catheterization of the urinary bladder and measurement of IAP. Measurements and Main Results – A 5‐Fr red rubber urinary catheter was placed under sedation, and IAP was determined using a water manometer with the cats in right lateral and sternal recumbency. Three readings were taken in each position by 2 observers. The cats were allowed to recover with the urinary catheter in place, and IAP was measured in each cat while they were awake in right lateral and sternal recumbency. Conclusions – In this population of clinically healthy cats, median (interquartile range) IAP taken over all measurements was 7.00 cm H₂O (5.23–8.83 cm H₂O). There was no statistical difference between observers or subject gender. Factors associated with a statistically significant increase in IAP were right lateral compared with sternal recumbency (P=0.002), being awake compared with sedated (P<0.001), having a higher body condition score (P=0.01 and 0.001), instillation of a higher volume of saline into the bladder for measurement (P<0.001), and struggling during awake measurements (P<0.001).     

Effects of Body Positioning on Swallowing and Esophageal Transit in Healthy Dogs

Background: Contrast videofluoroscopy is the imaging technique of choice for evaluating dysphagic dogs. In people, body position alters the outcome of videofluoroscopic assessment of swallowing.
Hypothesis/Objective: That esophageal transit in dogs, as measured by a barium esophagram, is not affected by body position.
Animals: Healthy dogs ( n = 15).
Methods: Interventional, experimental study. A restraint device was built to facilitate imaging of dogs in sternal recumbancy. Each dog underwent videofluoroscopy during swallowing of liquid barium and barium-soaked kibble in sternal and lateral recumbancy. Timing of swallowing, pharyngeal constriction ratio, esophageal transit time, and number of esophageal peristaltic waves were compared among body positions.
Results: Transit time in the cervical esophagus (cm/s) was significantly delayed when dogs were in lateral recumbency for both liquid (2.58 ± 1.98 versus 7.23 ± 3.11; P = .001) and kibble (4.44 ± 2.02 versus 8.92 ± 4.80; P = .002). In lateral recumbency, 52 ± 22% of liquid and 73 ± 23% of kibble swallows stimulated primary esophageal peristalsis. In sternal recumbency, 77 ± 24% of liquid ( P = .01 versus lateral) and 89 ± 16% of kibble ( P = .01 versus lateral) swallows stimulated primary esophageal peristalsis. Other variables were not significantly different.
Conclusions and Clinical Importance: Lateral body positioning significantly increases cervical esophageal transit time and affects the type of peristaltic wave generated by a swallow.     

INFLUENCE Of PATIENT POSITIONING ON THE L5–L6 MID-LAMINAR DISTANCE

The aim of this project was to determine the effect of patient position on the L5-L6 mid-laminar distance (MLD). The lumbar area of 22 recently euthanatized dogs of various breeds was radiographed in three positions: lateral recumbency with the spine in neutral position, lateral recumbency with the spine flexed in a kyphotic position, and sternal recumbency with the spine flexed in a kyphotic position. Digital images of the radiographs were analyzed using a computer program that allowed measurement of the MLD between L5-L6 in the three positions. The L5 and L6 MLD was significantly larger in sternal recumbency with the spine flexed (142.3 units) than both in lateral recumbency with the spine flexed (138.7 units; P= 0.001) and lateral recumbency with the spine in the neutral position (135.8 units; P < or = 0.001). The MLD in lateral recumbency with the spine flexed was significantly larger than in lateral recumbency with the spine in neutral position (P = 0.005). Positioning a dog in sternal recumbency with the spine flexed produces a significantly larger MLD than in lateral recumbency with the spine flexed; this should simplify needle placement when performing a lumbar puncture.     

Evaluation of the sedative and cardiorespiratory effects of dexmedetomidine,dexmedetomidine-butorphanol,and dexmedetomidine-ketamine in cats

OBJECTIVE: To determine sedative and cardiorespiratory effects of dexmedetomidine alone and in combination with butorphanol or ketamine in cats. DESIGN: Randomized crossover study. ANIMALS: 6 healthy adult cats. PROCEDURES: Cats were given dexmedetomidine alone (10 microg/kg [4.5 mg/lb], IM), a combination of dexmedetomidine (10 microg/kg, IM) and butorphanol (0.2 mg/kg [0.09 mg/lb], IM), or a combination of dexmedetomidine (10 microg/kg, IM) and ketamine (5 mg/kg [2.3 mg/lb], IM). Treatments were administered in random order, with > or = 1 week between treatments. Physiologic variables were assessed before and after drug administration. Time to lateral recumbency, duration of lateral recumbency, time to sternal recumbency, time to recovery from sedation, and subjective evaluation of sedation, muscle relaxation, and auditory response were assessed. RESULTS: Each treatment resulted in adequate sedation; time to lateral recumbency, duration of lateral recumbency, and time to recovery from sedation were similar among treatments. Time to sternal recumbency was significantly greater after administration of dexmedetomidine-ketamine. Heart rate decreased significantly after each treatment; however, the decrease was more pronounced after administration of dexmedetomidine-butorphanol, compared with that following the other treatments. Systolic and diastolic blood pressure measurements decreased significantly from baseline with all treatments; 50 minutes after drug administration, mean blood pressure differed significantly from baseline only when cats received dexmedetomidine and butorphanol. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in cats, administration of dexmedetomidine combined with butorphanol or ketamine resulted in more adequate sedation, without clinically important cardiovascular effects, than was achieved with dexmedetomidine alone.     

Electrocardiographic changes in the growing Mastín Español

Serial electrocardiograms were recorded from 70 Mastín Español dogs in right lateral recumbency, aged between one day and three years, in order to observe the changes in the waveform and intervals, QRS morphology, cardiac rhythm and heart rate caused by their growth. Age and bodyweight caused a gradual increase in the duration and amplitude of the P wave, duration of the PR, QT and RR intervals, amplitude of the R wave and duration of the QRS complex and ST segment. Q wave was observed in nearly all the recordings with different amplitudes. The S wave was only significant in one-day-old animals and QRS morphology showed significant important changes from qrS and rS to qR and qRs morphologies during the first two weeks of life. The T wave increased its amplitude until the age of two months and changed its polarity (from negative to positive) from five months of age onwards. The heart rate decreased until the age of seven months, reaching stabilised values of 110 ± 7-3 beats per minute. Sinus tachycardia was commonplace in animals under one month old and respiratory sinus arrhythmia was found from six months of age. Sex only influenced the duration and amplitude of the T wave. Males had higher mean values than females.     

The effect of intravenous administration of variable-dose flumazenil after fixed-dose ketamine and midazolam in healthy cats

The effects of intravenous administration of variable-dose flumazenil (0, 0.001, 0.005, 0.01, and 0.1 mg/kg) after ketamine (3 mg/kg) and midazolam (0.0 and 0.5 mg/kg) were studied in 18 healthy unmedicated cats from time of administration until full recovery. End-points were chosen to determine whether flumazenil shortened the recovery period and/or modified behaviors previously identified and attributed to midazolam. Overall, flumazenil administration had little effect on recovery or behaviors. One minute after flumazenil administration, all cats were recumbent but a greater proportion of cats which received the highest dose assumed sternal recumbency with head up than any other group. Although not significant, those cats that received the highest flumazenil dose also had shorter mean times for each of the initial recovery stages (lateral recumbency with head up, sternal recumbency with head up and walking with ataxia) than any of the other treatment groups that received midazolam. For complete recovery, flumazenil did decrease the proportion of the cats that was sedated, but did not shorten the time to walking without ataxia. Based on this study, the administration of flumazenil in veterinary practice, at the doses studied, to shorten and/or improve the recovery from ketamine and midazolam in healthy cats cannot be recommended.     

Body temperature and behaviour of mares during the last two weeks of pregnancy

Average daily core body temperature and behavioural patterns of pregnant mares were studied, in search of definitive signs of parturition within 24 h of the event. Nineteen pony mares were sampled twice daily for core body temperature. A significant temperature drop, averaging 0.1 degrees C (0.2 degrees F) was observed during the day prior to parturition. Between 18.00 h and 06.00 h, during the two weeks before parturition, Thoroughbred and Standardbred mares (n = 52) spent an average 66.8 per cent of their time standing, 27.0 per cent eating, 4.9 per cent lying in sternal recumbency, 1.0 per cent lying in lateral recumbency, and 0.3 per cent walking. On the night before parturition, mares spent significantly less time lying in sternal recumbency than on previous nights and on the night of parturition all behaviour patterns except eating were significantly different from the nights of the two weeks before parturition. There was an increase in walking (5.3 per cent), lying in sternal recumbency (8 per cent) and lying in lateral recumbency (5.3 per cent) whereas standing (53.3 per cent) was decreased. In 58 observed pregnancies, 54 mares (97 per cent) foaled in a recumbent position and 50 mares (86 per cent) foaled between 18.00 h and 06.00 h.     

Effect of body position on the arterial partial pressures of oxygen and carbon dioxide in spontaneously breathing,conscious dogs in an intensive care unit

Objective – To evaluate the effect of body position on the arterial partial pressures of oxygen and carbon dioxide (PaO₂, PaCO₂), and the efficiency of pulmonary oxygen uptake as estimated by alveolar‐arterial oxygen difference (A‐a difference). Design – Prospective, randomized, crossover study. Setting – University teaching hospital, intensive care unit. Animals – Twenty‐one spontaneously breathing, conscious, canine patients with arterial catheters placed as part of their management strategy. Interventions – Patients were placed randomly into lateral or sternal recumbency. PaO₂ and PaCO₂ were measured after 15 minutes in this position. Patients were then repositioned into the opposite position and after 15 minutes the parameters were remeasured. Measurements and Main Results – Results presented as median (interquartile range). PaO₂ was significantly higher (P=0.001) when patients were positioned in sternal, 91.2 mm Hg (86.0–96.1 mm Hg), compared with lateral recumbency, 86.4 mm Hg (73.9–90.9 mm Hg). The median change was 5.4 mm Hg (1.1–17.9 mm Hg). All 7 dogs with a PaO₂<80 mm Hg in lateral recumbency had improved arterial oxygenation in sternal recumbency, median increase 17.4 mm Hg with a range of 3.8–29.7 mm Hg. PaCO₂ levels when patients were in sternal recumbency, 30.5 mm Hg (27.3–32.7 mm Hg) were not significantly different from those in lateral recumbency, 32.2 mm Hg (28.3–36.0 mm Hg) (P=0.07). The median change was ?1.9 mm Hg (?3.6–0.77 mm Hg). A‐a differences were significantly lower (P=0.005) when patients were positioned in sternal recumbency, 21.7 mm Hg (17.3–27.7 mm Hg), compared with lateral recumbency, 24.6 mm Hg (20.4–36.3 mm Hg). The median change was ?3.1 mm Hg (?14.6–0.9 mm Hg). Conclusions – PaO₂ was significantly higher when animals were positioned in sternal recumbency compared with lateral recumbency, predominantly due to improved pulmonary oxygen uptake (decreased A‐a difference) rather than increased alveolar ventilation (decreased PaCO₂). Patients with hypoxemia (defined as PaO₂<80 mm Hg) in lateral recumbency may benefit from being placed in sternal recumbency. Sternal recumbency is recommended to improve oxygenation in hypoxemic patients.     

Electrocardiographic parameters of free-ranging roe deer (Capreolus capreolus).

Electrocardiographic parameters were measured in 28 free-ranging roe deer (Capreolus capreolus). The electrocardiograms (ECGs) were recorded in base-apex lead, standard bipolar limb leads (I, II, III), and augmented unipolar limb leads (aVR, aVL, aVF). Morphology and amplitude of P waves, QRS complexes, and T waves were analyzed in all seven leads. Cardiac rhythm, heart rate, and durations of P, QRS, and T waves, PR interval, QTc interval, and ST segment were calculated in the base-apex lead. The mean electrical axis for each individual was determined from the net amplitude of the QRS complex in leads I and II. All of the animals had a sinus rhythm. Heart rates ranged from 60-180 beats per minute, with a mean +/- SD of 104.8 +/- 44.1. The electrical axis was 100 degrees-220 degrees, with a mean +/- SD of 169.5 degrees +/- 40.8 degrees. The base-apex lead provided the most uniform ECG patterns and higher mean amplitudes than did standard leads.     

The effect of body position on the 'hanging drop' method for identifying the extradural space in anaesthetized dogs

ObjectivesTo assess the accuracy of the ‘hanging drop method’ for identifying the extradural space in anaesthetized dogs positioned in sternal or lateral recumbency.Study designProspective randomized-experimental study.AnimalsSeventeen clinically healthy adult dogs, 10 females and seven males weighing 8.4–26.2 kg.MethodsDogs were positioned in either sternal (n = 8) or lateral (n = 9) recumbency under general anaesthesia. A 20 SWG spinal needle pre-filled with 0.9% saline was advanced through the skin into the lumbosacral extradural space and the response of the saline drop recorded, i.e. whether it: 1) was aspirated from the hub into the needle; 2) remained within the hub, or 3) moved synchronously with i) spontaneous respiration, ii) heart beat or iii) manual lung inflation. The position of the needle tip was ultimately determined by positive contrast radiography.ResultsOne dog positioned in lateral recumbency was excluded from the study because bleeding occurred from the needle hub. Saline was aspirated into the needle in seven of eight dogs held in sternal recumbency but in none of the dogs positioned in lateral recumbency. Accurate needle tip placement in the extradural space was confirmed by positive contrast radiography in all dogs.Conclusion and clinical relevanceThe ‘hanging drop’ method, when performed with a spinal needle, appears to be a useful technique for identifying the location of the extradural space in anaesthetized medium-sized dogs positioned in sternal, but not in lateral recumbency. The technique may yield ‘false negative’ results when performed in dogs positioned in sternal recumbency.     

Sleep and Wakefulness in the Housed Pony Under Different Dietary Conditions

For several weeks, three ponies kept in an environment with controlled light and temperature, were studied for behaviour (time spent in recumbency and time required to consume hay or oats) and for electrical activity of the brain (cortical and sub-cortical) during the night phase of the circadian rhythm.

Recumbency was adopted by all the ponies for six or seven periods during the night. With a regimen of hay ad libitum, about four hours were cumulated in sternal recumbency and only one hour in complete lateral recumbency. Various degree of sleep, as identified by cortical and hippocampal electrical activities, accounted for 30% of the circadian cycle. Paradoxical sleep was calculated to occur during 7% of the 24 hours.

When oats were substituted for hay or during fasting for two to five days, the total recumbency time and the total sleep time (slow wave sleep and paradoxical sleep) increased. The time in lateral recumbency did not change.