Some physiological and biochemical effects of intravenous fluid administration during halothane anaesthesia in the dog

Six dogs with previously implanted arterial, central venous, pulmonary arterial and left atrial catheters received halothane anaesthesia, and halothane anaesthesia plus administration of a balanced electrolyte solution given over one hour, in a cross-over experiment. Parameters measured included temperature, heart rate (HR), respiratory rate (f), arterial and mixed venous blood-gases and acid-base parameters, mean arterial pressure ( AP ), mean pulmonary artery pressure ( PAP ), mean left atrial pressure ( LAP ), mean central venous pressure ( CVP ), packed cell volume (PCV), total plasma protein (TPP), plasma sodium, potassium and chloride concentrations, and urinary sodium and potassium concentrations.
During halothane anaesthesia there were significant decreases in AP , PCV, TPP, f, and significant increases in arterial and mixed venous oxygen, and glucose concentrations, when compared with conscious control values. When intravenous fluid was administered during anaesthesia, there were significant decreases in temperature, AP , PCV and TPP, with significant increases in PAP , CVP and f, when compared with values during anaesthesia alone. After one hour recovery period from anaesthesia, dogs receiving intravenous fluids had significantly decreased PaO₂ values and significantly increased pH when compared with anaesthesia alone. There was an average urinary excretion of 7 mmol of sodium and 5 mmol of potassium during anaesthesia, and 36 mmol of sodium and 8 mmol potassium during fluid administration.     

Clinical anaesthesia in the horse: comparison of enflurane and halothane

Anaesthesia was induced in 24 horses with xylazine and ketamine and maintained with halothane (12 cases) or enflurane (12 cases) in oxygen. Pulse rate, arterial blood pressure, arterial blood gas values, respiratory rate and tidal volume were measured at regular intervals during anaesthesia. Serial venous blood samples were taken for assay of glucose, urea, haemoglobin, packed cell volume, gamma glutamyl transpeptidase, aspartate aminotransferase, alanine aminotransferase and creatine kinase. Operating conditions and the horses' behaviour in the recovery period were also recorded. In the case of the group of horses receiving enflurane, difficulty was experienced maintaining anaesthesia deep enough for surgery. This group also displayed greater respiratory depression. There were no significant differences between arterial blood pressure values, or any of the haematological or biochemical parameters recorded in each group. Recovery from anaesthesia was significantly faster in horses receiving enflurane but less smooth. It was concluded that, although enflurane appeared to be safe in the horse, the respiratory depression and the unpleasant recovery did not make it a desirable alternative to halothane.     

Cardiorespiratory, endocrine and metabolic changes in ponies undergoing intravenous or inhalation anaesthesia

Six Welsh gelding ponies (weight 246 ± 6 kg) were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) followed by 0.02 mg/kg of detomidine i.v. Anaesthesia was induced with 2 mg/kg of ketamine i.v. Ponies were intubated and lay in left lateral recumbency. On one occasion anaesthesia was maintained for 2 h using 1.2% halothane in oxygen. The same group of ponies were anaesthetized 1 month later using the same induction regime and anaesthesia was maintained with a combination of detomidine, ketamine and guaiphenesin, while the ponies breathed oxygen-enriched air. Electrocardiogram, heart rate, mean arterial blood pressure, cardiac output, respiratory rate, blood gases, temperature, haematocrit, glucose, lactate and cortisol were measured and cardiac index and systemic vascular resistance were calculated in both groups. Beta-endorphin, met-enkephalin, dynorphin, arginine vasopressin (AVP), adrenocorticotrophic hormone (ACTH) and catecholamines were measured in the halothane anaesthesia group only and 11-deoxycortisol during total intravenous anaesthesia (TIVA) only. Cardiorespiratory depression was more marked during halothane anaesthesia. Hyperglycaemia developed in both groups. Lactate and AVP increased during halothane anaesthesia. Cortisol increased during halothane and decreased during TIVA. There were no changes in the other hormones during anaesthesia. Recovery was smooth in both groups. TIVA produced better cardiorespiratory performance and suppressed the endocrine stress response observed during halothane anaesthesia.     

A comparison of the haemodynamic effects of isoflurane and halothane anaesthesia in horses

The purpose of this study was to compare the haemodynamic effects of equipotent isoflurane and halothane anaesthesia. Six adult horses were investigated on two separate occasions at least 4 weeks apart. On both occasions anaesthesia was induced by ketamine 2.2 mg/kg bwt given 5 min after i.v. administration 100 microg/kg bwt romifidine. Anaesthesia was maintained either by halothane or isoflurane (end-tidal concentrations 0.9-1.0% and 1.3-1.4%, respectively). Horses were ventilated by intermittent positive pressure to maintain PaCO2 between 40-50 mmHg. Haemodynamic variables were measured using catheter-mounted strain gauge transducers in the left and right ventricle, aorta, and right atrium. Cardiac output (CO), velocity time integral (VTI), maximal aortic blood flow velocity (Vmax) and acceleration (dv/dt(max)), left ventricular pre-ejection period (PEP) and ejection time (ET) were measured from aortic blood flow velocity waveforms obtained by transoesophageal Doppler echocardiography. Flow velocity waveforms were recorded from the femoral arteries and veins using low pulse repetition frequency Doppler ultrasound. Time-averaged mean velocity (TAV), velocity of component a (TaVa), velocity of component b (TaVb) and early diastolic deceleration slope (EDDS) were measured. Pulsatility index (PI) and volumetric flow were calculated. Microvascular blood flow was measured in the left and right semimembranosus muscles by laser Doppler flowmetry. Maximal rate of rise of LV pressure (LVdp/dt(max)), CO, Vmax, dv/dt(max), ET, VTI were significantly higher at all time points during isoflurane anaesthesia compared to halothane anaesthesia. Pre-ejection period and diastolic aortic blood pressure were significantly less throughout isoflurane anaesthesia compared to halothane. Isoflurane anaesthesia was associated with significantly lower systemic vascular resistance than halothane anaesthesia. Femoral arterial and venous blood flow were significantly higher and EDDS and PI were significantly lower during isoflurane anaesthesia compared to halothane anaesthesia. In addition during both halothane and isoflurane anaesthesia, femoral arterial flow was higher and EDDS and PI lower in the left (dependent) artery compared to the right (nondependent) artery. This study supports previous work demonstrating improved left ventricular systolic function during isoflurane compared to halothane anaesthesia. This improvement was still evident after premedication with a potent-long acting alpha2-adrenoreceptor agonist, romifidine, and induction of anaesthesia with ketamine. There was also evidence of increased hindlimb blood flow during isoflurane anaesthesia. However, there were differences observed in flow between the left and right hindlimb during maintenance of anaesthesia with each agent, suggesting that there were differences in regional perfusion in anaesthetised horses caused by factors unrelated to agents administered.     

EVALUATION OF EQUTTHESIN AS A GENERAL ANAESTHETIC IN CAMELS (Camelus dro-medarius).

The effects of equithesin administered IV “to effect” were evaluated in twelve adult domesticated camels (Camelus Dromedarius). The mean dose required for “to effect” anaesthesia as 0.74 ± 0.03 ml/kg. Moderate relaxation of muscles lasted 30 to 45 minutes and duration of analgesia was 10–15 minutes. The sleeping time was 15 to 45 minutes and the animals showed recovery in 75–115 minutes. During anaesthesia, there was moderate tachycardia, transient hypotension and decrease in central venous pressure. Primary T wave changes were a consistent finding in the ECG. There was mild hypoxemia, mild hypercapnia and significant decrease in arterial-venous oxygen tension difference. A significant decrease in the total leucocyte count occurred during the peak effect of anaesthesia. Hyperglycaemia observed at the peak anaesthetic effect was followed by hypoglycaemia 24 hours after administration of equithesin. The changes in rectal temperature, respiratory rate and other biochemical constituents studies were not significantly affected.     

Changes in heart rate, mean arterial pressure, blood biochemistry, plasma glucose, plasma lactate and some plasma enzymes during sufentanil/halothane anaesthesia in horses

Nine horses were each anaesthetised for 40 min using SufentaniVhalothane. No surgery was performed. After premedication (detomidine 5 pgkg bwt iv) induction of anaesthesia was achieved by a combination of guaiphenesinlthiopentone. Anaesthesia was maintained by inhalation of halothane (0.8%) in oxygen. Six horses (Group 1) received 1 pgkg bwt sufentanil followed by a second injection (1 pg/kg bwt) after 20 min. Three horses (Group 2) received 2 pg/kg bwt sufentanil also followed by a second injection (2 pg/kg bwt) after 20 min. Each sufentanil injection produced a slight decrease in mean arterial blood pressure with a gradual return to the initial pressure. Bradycardia was also observed. Sufentanil injection induced apnoea needing artificial ventilation. Arterial blood was sampled for analysis during the anaesthetic procedure. At the end of anaesthesia, 1 h and 24 h after rising, venous blood was sampled to determine concentrations of lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and creatine phosphokinase (CPK). Values obtained were compared with values in blood taken before premedication. Plasma glucose and lactate concentrations just before sufentanil administration, at the end of anaesthesia and 1 h after rising were compared to control values. Plasma glucose concentration increased significantly during anaesthesia but returned to normal values 1 h after rising. All other parameters stayed within physiological ranges. In both groups spontaneous respiration returned 20–25 min after the second sufentanil injection. Recovery was uneventful.     

Evaluation of an anaesthetic technique used in dogs undergoing craniectomy for tumour resection

ObjeCTIVE: To evaluate a total intravenous anaesthetic technique in dogs undergoing craniectomy. STUDY DESIGN: Prospective clinical study. ANIMALS: Ten dogs admitted for elective surgical resection of rostro-tentorial tumours. METHODS: All dogs were premedicated with methadone, 0.2 mg kg(-1) intramuscularly 30 minutes prior to induction of anaesthesia. Anaesthesia was induced with propofol administered intravenously (IV) to effect, following administration of lidocaine 1 mg kg(-1) IV and maintained with a continuous infusion of propofol at < or =0.4 mg kg(-1) minute(-1) during instrumentation and preparation and during movement of the animals to recovery. During surgery, anaesthesia was maintained using a continuous infusion of propofol at 相似文献   

Haemodynamic and blood gas changes in buffaloes (Bubalus bubalis) in the supine position following thiopentone anaesthesia with premedication

Studies were undertaken on seven adult female buffaloes (Bubalus bubalis) premedicated with triflupromazine hydrochloride (0.3 mg/kg) and chloral hydrate (30 mg/kg). Anaesthesia was induced with thiopentone sodium (10 mg/kg) and animals were kept under intermittent positive pressure ventilation. Measurements were made for 30 min in the lateral position, for 20 min in the supine position and subsequently for 40 min again in the lateral position. Regurgitation during anaesthesia was avoided by evacuation of the rumen by rumenotomy two days prior to the experiment. When animals were in the lateral position there were minimal changes in arterial pressure and heart rate but central venous pressure rose. These changes were related to intermittent positive pressure ventilation. In the supine position, increase in heart rate (28%) was associated with profound hypotension (56%) and decrease in central venous pressure (171%) in these animals. There was a fall in venous oxygen tension and a marked increase (91%) in oxygen extraction ratio. Restoration to the lateral position ameliorated all these changes rapidly. It was suggested that a low pressure-low flow circulatory state exists in anaesthetised adult buffaloes in the supine position.     

A case of spontaneous venous embolism with carbon dioxide during laparoscopic surgery in a pig

BACKGROUND: Carbon dioxide (CO2) embolism is a possible complication of capnoperitoneum during laparoscopic surgery. Experimentally induced venous CO2 embolism has been studied in pigs. In this paper we report a case of spontaneous CO2 embolism. OBSERVATIONS: A 4-month-old Large White pig weighing 20 kg underwent experimental laparoscopic surgery under general anaesthesia. Monitoring consisted of pulse oximetry, capnography, airway pressure, electrocardiography, invasive arterial and central venous blood pressures, and arterial blood-gas analysis. Shortly after the start of laparoscopy and onset of CO2 insufflation, sudden decreases in end-tidal CO2 (Pe'CO2), haemoglobin saturation of oxygen (SpO2), systolic arterial blood pressure and heart rate were observed. Airway pressure increased and pulmonary compliance decreased simultaneously. Insufflation was immediately discontinued and epinephrine (2 mg IV), atropine (0.5 mg IV) and a 50 mL bolus of a polygeline solution were administered without effect. At this time arterial blood-gas analysis revealed a pH of 7.29 and a PaCO2 of 6.8 kPa (51.2 mmHg); PaO2 was 26.6 kPa (199.5 mmHg). After 4 minutes asystole occurred. CONCLUSIONS: The sudden decrease of Pe'CO2 and lung compliance combined with the sudden decrease in systolic blood pressure, heart rate and a poor response to resuscitation suggest a case of fatal gaseous venous embolism.     

Anaesthetic complications in pigs undergoing MRI guided convection enhanced drug delivery to the brain: a case series

ObservationsA total of 13 intracerebral infusions were performed at approximately 1 month intervals in three NIH miniature pigs over the age range of 31–59 weeks. Pigs received azaperone and ketamine premedication to allow venous cannulation and propofol induction of anaesthesia. Anaesthesia was maintained with isoflurane throughout cranial surgery and MRI scanning. Physiological monitoring during surgery consisted of blood pressure, pulse, temperature and oxygen saturation monitoring, ECG and capnography. Analgesia consisted of meloxicam and morphine. However, during MRI scanning blood pressure and ECG monitoring had to be discontinued. Anaesthetized pigs underwent intermittent intraputamenal convection enhanced delivery (CED) of gadolinium with real-time magnetic resonance imaging. Progressive tachycardia was consistently observed in all pigs during CED with a mean ± SD maximum increase of 41 ± 22 beats minute^?1 from a baseline heart rate of 96 ± 9 minute^?1. The heart rate remained elevated until recovery. A mean reduction in body temperature of 2.8 ± 0.6 °C from the start of anaesthesia was also observed during the period of MRI scanning. All pigs recovered from anaesthesia smoothly and heart rates returned to normal during the recovery period.ConclusionsHypothermia is common in pigs undergoing this sedation and anaesthesia protocol. Convection enhanced delivery of drugs in healthy anaesthetized pigs may result in tachycardia.     

Oxygenation and plasma endothelin‐1 concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse‐delivered inhaled nitric oxide

ObjectiveTo assess oxygenation, ventilation‐perfusion (V/Q) matching and plasma endothelin (ET‐1) concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse‐delivered inhaled nitric oxide (iNO).Study DesignProspective experimental trial.AnimalsHealthy adult Standardbred horses.MethodsHorses were anaesthetized with isoflurane in oxygen and placed in lateral recumbency. Six control (C group) horses were anaesthetized without iNO delivery and six horses received pulse‐delivered iNO (NO group). After 2.5 hours of anaesthesia isoflurane and iNO were abruptly discontinued, inhaled oxygen was reduced from 100% to approximately 30%, and the horses were moved to the recovery stall. At intervals during a 30‐minute period following the discontinuation of anaesthesia, arterial and mixed venous blood gas values, shunt fraction (Qs/Qt), plasma ET‐1 concentration, pulse rate and respiratory rate were measured or calculated. Repeated measures anova and a Bonferroni post hoc test was used to analyze data with significance set at p <0.05.ResultsAt all time points in the recovery period, NO horses maintained better arterial oxygenation (oxygen partial pressure: NO 13.2 ± 2.7–11.1 ± 2.7 versus C 6.7 ± 1.1–7.1 ± 1.1 kPa) and better V/Q matching (Qs/Qt NO 0.23 ± 0.05–0.14 ± 0.06 versus C 0.48 ± 0.03–0.32 ± 0.08%) than C horses. Mixed venous oxygenation was higher in NO for 25 minutes following the discontinuation of anaesthesia (NO 6.3 ± 0.2–4.5 ± 0.07 versus C 4.7 ± 0.6–3.7 ± 0.3 kPa). In both groups of horses arterial oxygenation remained fairly stable; venous oxygenation declined over this time period in the NO group but still remained higher than venous oxygen in the C group. ET‐1 concentrations were higher at most time points in C than NO. Changes in other parameters were either minor or absent.Conclusions and Clinical RelevanceDelivery of iNO to healthy horses during anaesthesia results in better arterial and venous oxygenation and V/Q matching (as determined by lower Qs/Qt) and lower ET‐1 concentrations throughout a 30‐minute anaesthetic recovery period.     

The effects of spontaneous and mechanical ventilation on central cardiovascular function and peripheral perfusion during isoflurane anaesthesia in horses

OBJECTIVE: To compare the effects of spontaneous breathing and mechanical ventilation on haemodynamic variables, including muscle and skin perfusion measured with laser Doppler flowmetery, in horses anaesthetized with isoflurane. STUDY DESIGN: Prospective controlled study. ANIMALS: Ten warm-blood trotter horses (five males, five females). Mean mass was 492 kg (range 420-584 kg) and mean age was 5 years (range 4-8 years). MATERIALS AND METHODS: After pre-anaesthetic medication with detomidine (10 microg kg(-1)) anaesthesia was induced with intravenous (IV) guaifenesin and thiopental (4-5 mg kg(-1) IV) and maintained using isoflurane in oxygen. The horses were positioned in dorsal recumbency. In five animals breathing was initially spontaneous (SB) while the lungs of the other five were ventilated mechanically using intermittent positive pressure ventilation (IPPV). Total anaesthesia time was 4 hours with the ventilatory mode changed after 2 hours. During anaesthesia, heart rate (HR) cardiac output (Qt) stroke volume (SV) systemic arterial blood pressures (sAP), and pulmonary arterial pressure (pAP) were recorded. Peripheral perfusion was measured in the semimembranosus and gluteal muscles and on the tail skin using laser Doppler flowmetry. Arterial (a) and mixed venous (v) blood gases, pH, haemoglobin concentration [Hb], haematocrit (Hct), plasma lactate concentration and muscle temperature were measured. Oxygen content, venous admixture (s/Qt) oxygen delivery (DO(2)) and oxygen consumption (VO(2)) were calculated. RESULTS: During mechanical ventilation, HR, sAP, pAP, Qt, SV, Qs/Qt and PaCO(2) were lower and PaO(2) was higher compared with spontaneous breathing. There were no differences between the modes of ventilation in the level of perfusion, DO(2), VO(2), [Hb], (Hct), or plasma lactate concentration. After the change from IPPV to SB, left semimembranosus muscle and skin perfusion improved, while muscle perfusion tended to decrease when SB was changed to IPPV. Low-frequency flow motion was seen twice as frequently during IPPV compared with SB. CONCLUSIONS: Mechanical ventilation impaired cardiovascular function compared with SB in horses during isoflurane anaesthesia. Muscle and skin perfusion changes occurred with ventilation, although further studies are needed to elucidate the underlying mechanisms.     

Motility of the oesophagus and gastro-oesophageal junction during halothane anaesthesia in sheep

Electromanometry and electromyography were used to study gastro-oesophageal motility in two planes of halothane anaesthesia in sheep. Gastro-oesophageal motility when present was greater in light than in deep anaesthesia. The caudal thoracic oesophagus contracted more frequently and for longer than the rostral thoracic oesophagus. In light anaesthesia oesophageal movements were peristaltic in direction with a propagation velocity of 26–29 cm sec^-1. Rumen pressures increased throughout anaesthesia and the rate of increase was greatest when the plane of anaesthesia was deep at the start. Gastro-oesophageal reflux (GOR) occurred in both planes of anaesthesia and must occur by passive mechanisms during deep anaesthesia because gastro-oesophageal motility was inhibited.A high pressure zone (HPZ) was demonstrated for a length of 2.9 cm at the gastro-oesophageal junction with a balloon-tipped catheter and a pull through technique. Open-tipped catheters could detect the HPZ but were less sensitive. The pressure in the HPZ was not significantly influenced by the depth of anaesthesia used. In 80% of cases of light anaesthesia an increase in HPZ pressure preceeded the contraction of the cranial sac of the rumen. In deep anaesthesia the HPZ continued to have rhythmic changes in tone. Spontaneous GOR coincided with a maximum gastro-oesophageal pressure gradient in 24% of cases. Rumen insufflation with oxygen provoked GOR at a rumen pressure above 33 mmHg compared with 7.2 mmHg during spontaneous reflux.The study demonstrates that a gastro-oesophageal pressure gradient was not primarily responsible for the initiation of GOR during anaesthesia and that the HPZ at the gastro-oesophageal junction of sheep had some of the properties of a lower oesophageal sphincter and played an important role in the initiation of GOR during anaesthesia.     

隆朋麻醉对犬心钠素和皮质醇的影响

为探讨隆朋麻醉对犬心钠素(ANP)和皮质醇(Cor.)分泌的影响,选取健康犬12只,将其随机均分为单纯隆朋麻醉组和对照组。2组均于麻醉前,麻醉后0.5、2、8、24、48、72和120 h采集静脉血,采集完毕后迅速离心取血浆,用放射性免疫法检测ANP和Cor.的浓度。麻醉组:ANP出现轻微的下降趋势,在2 h时恢复到正常水平;而Cor.呈现较轻微的下降趋势,在24 h时恢复到正常水平;对照组:试验开始后ANP和Cor.在0~0.5 h都呈现上升趋势,ANP和Cor.都在2 h时恢复到正常水平。结果表明,隆朋单纯麻醉时对ANP和Cor.有轻微的影响。     

Comparison of respiratory function during TIVA (romifidine,ketamine, midazolam) and isoflurane anaesthesia in spontaneously breathing ponies Part I: blood gas analysis and cardiorespiratory variables

ObjectiveTo compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique.Study designExperimental, cross–over study.AnimalsSix healthy ponies weighing mean 286 (range 233–388) ± SD 61 kg, age 13 (9-16) ± 3 years.MethodsThe ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 μg kg^?1 intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg^?1) and ketamine (2.5 mg kg^?1), then maintained either with inhaled isoflurane (Fe’Iso = 1.1 vol%) (T-ISO) or an IV infusion of romifidine (120 μg kg^?1 hour^?1), midazolam (0.09 mg kg^?1 hour^?1 IV) and ketamine (3.3 mg kg^?1 hour^?1) (T-TIVA). Ponies were placed in lateral recumbency. Breathing was spontaneous and Fi’O₂ 60%. After an instrumentation/stabilisation period of 30 minutes, arterial and mixed venous blood samples were taken simultaneously every 10 minutes for 60 minutes and analysed immediately. Oxygen extraction ratio (O₂ER) and venous admixture were calculated. Tidal volume (TV), minute volume (MV), respiratory rate (f_R), packed cell volume (PCV), arterial blood pressure and heart rate (HR) were measured and recorded. Data were analysed with mixed model anova (a = 0.05). Treatments were compared overall and at two selected time points (T30 and T60) using Bonferroni correction.ResultsArterial and mixed venous partial pressures of O₂ and CO₂, and TV were significantly lower and MV and f_R were higher in T-TIVA compared to T-ISO. Venous admixture did not differ between treatments. O₂ER was significantly higher in T-TIVA. Mean arterial pressure was higher and HR was lower in T-TIVA compared to T-ISO.Conclusions and clinical relevanceWhilst arterial CO₂ was within an acceptable range during both protocols, the impairment of oxygenation was more pronounced with the T-TIVA evidenced by lower arterial and venous oxygen partial pressures.     

Cardiovascular effects recorded in horses during anaesthesia after treatment with trichlorfon

Five horses were anaesthetised twice with thiopentone sodium, guaifenesin and halothane. The second anaesthesia was 16 days after the first and two days following oral administration of trichlorfon. Heart rate, carotid arterial, pulmonary arterial and right atrial pressures, cardiac output and blood temperature were measured every 15 minutes for 120 minutes. Heart rate, carotid arterial pressure and cardiac output were similar on both occasions. Pulmonary arterial and right atrial pressures were highest during anaesthesia after treatment with trichlorfon when compared with values obtained before treatment. Pulmonary vascular resistance was significantly decreased at four measurement times during anaesthesia after treatment with trichlorfon. All cardiovascular measurements were within ranges accepted as normal for halothane anaesthesia in horses. In a second experiment, four ponies were anaesthetised with xylazine and ketamine on two occasions one week apart. Two ponies received trichlorfon two days before the second anaesthesia. Heart rate, arterial pressure and respiratory rate recorded during anaesthesia were not different in ponies after organophosphate treatment. The time to standing after the second anaesthesia was significantly increased in all ponies.     

Fatal venous air embolism in a cat undergoing dental extractions

A five‐year‐old domestic shorthair cat underwent general anaesthesia and tooth extractions. Immediately after use of a high‐speed, air‐driven, water‐cooled dental drill, the cat suffered cardiac arrest and attempted resuscitation was unsuccessful. Post‐mortem radiographs showed air in the vena cava, right atrium, right auricle and right ventricle, hepatic and renal veins. These findings were confirmed at post‐mortem examination. The cause of death was massive air embolism. There are reports of fatal venous air embolism in the human literature from the use of high‐speed, air‐driven, water‐cooled dental drills. In this case, we believe that the air jet from the cooling system provided an enormous pressure gradient allowing air entry through an alveolar bone fracture or the inflamed gingival tissues. This is the first report of fatal venous air embolism associated with the use of a high‐speed dental drill in the veterinary literature.     

Brightness of venous blood in South American camelids: implications for jugular catheterization

Objective  To compare the brightness of South American camelid venous blood to that of Equidae.
Study design  Prospective clinical evaluation.
Animals  Twelve South American camelids (eight llamas, four alpacas), eight horses and ponies (control group).
Methods  Appropriately sized catheters were placed in the jugular vein of each animal under local anaesthesia. The blood spilt before the catheter was capped was caught on a white tile. A sample of blood was drawn for blood-gas analysis. The brightness of the blood (both on the tile and in the syringe) was matched to a colour chart (1 = darkest red, 8 = brightest red) by a single observer under bright light conditions. Packed cell volume (PCV) and partial pressure of oxygen (PvO₂) in the blood were also measured on the syringe blood. Normally distributed data were compared using a two tailed t -test, and non-normally distributed data were compared using a Mann–Whitney U -test. Significance was set at p  < 0.05.
Results  Camelid venous blood was significantly brighter red than that of horses and ponies both on the white tile ( p  = 0.0003) and in the syringe ( p  = 0.0001). PCV was significantly lower in camelids (32 ± 4%) compared with horses (37 ± 5%). Partial pressure of oxygen values were similar between groups.
Conclusions and clinical relevance  Jugular venous blood in alpacas and llamas is significantly brighter red than that of horses. Colour should not be used as a sole determinant of venous or arterial catheterization in this species.     

Effects of sevoflurane, isoflurane and halotane anaesthesia on fluorescein angiographic phases of dogs: a comparative study

A fluorescein angiography method was developed to compare the onset and the total duration of the fluorangiographic phases between three anaesthetic protocols in six healthy mixed-breed dogs. The animals were anaesthetized three times. Each dog received, as pre-anaesthetic protocol, atropine (10 micrograms/kg intramuscularly), and as a sedative, romifidine (80 micrograms/kg intravenously). Fifteen minutes later, induction of anaesthesia was delivered with propofol (1 mg/kg intravenously) and maintained either with sevoflurane (SEVO group), isoflurane (ISO group) or halothane (HAL group) for 30 min in all cases. Some angiographic, cardiovascular and respiratory variables were registered during the procedure. Recovery times were also registered. Angiographic variables recorded were: onset of the arterial phase (TA), onset of the arteriovenous phase (TAV), onset of the venous phase (TV), complete arterial phase duration (I1), complete arteriovenous phase duration (I2) and I1 plus I2 (I3). Mean heart rate, mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate, tidal volume, arterial oxygen saturation and end-tidal CO2 during SEVO and ISO anaesthesia, were similar in dogs. Minute ventilation and rectal temperature were higher in dogs with SEVO than ISO. HAL produced higher arterial pressures and a lower arterial oxygen saturation than ISO and SEVO. Mean respiratory rate, rectal temperature and minute ventilation were higher in HAL. Pulse rate, end-tidal CO2 and tidal volume were similar in the dogs of the three groups. No differences in recovery times were found. The fluorescein angiographic times were within the normal range. There were no significant differences between protocols in I1, I2 or I3. HAL produced a significant increase of all temporal variables (TA, TAV and TV) when compared with ISO; TA was higher in HAL than SEVO-treated dogs. All protocols appear to be safe and effective for inducing and maintaining general anaesthesia in healthy dogs for performing fluorescein angiography.     

A study of cardiovascular function under controlled and spontaneous ventilation in isoflurane–medetomidine anaesthetized horses

Objective To determine, in mildly hypercapnic horses under isoflurane–medetomidine balanced anaesthesia, whether there is a difference in cardiovascular function between spontaneous ventilation (SV) and intermittent positive pressure ventilation (IPPV). Study design Prospective randomized clinical study. Animals Sixty horses, undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. Methods Horses were sedated with medetomidine and anaesthesia was induced with ketamine and diazepam. Anaesthesia was maintained with isoflurane and a constant rate infusion of medetomidine. Horses were assigned to either SV or IPPV for the duration of anaesthesia. Horses in group IPPV were maintained mildly hypercapnic (arterial partial pressure of carbon dioxide (PaCO₂) 50–60 mmHg, 6.7–8 kPa). Mean arterial blood pressure (MAP) was maintained above 70 mmHg by an infusion of dobutamine administered to effect. Heart rate (HR), respiratory rate (f_R), arterial blood pressure and inspiratory and expiratory gases were monitored continuously. A bolus of ketamine was administered when horses showed nystagmus. Cardiac output was measured using lithium dilution. Arterial blood‐gas analysis was performed regularly. Recovery time was noted and recovery quality scored. Results There were no differences between groups concerning age, weight, body position during anaesthesia and anaesthetic duration. Respiratory rate was significantly higher in group IPPV. Significantly more horses in group IPPV received supplemental ketamine. There were no other significant differences between groups. All horses recovered from anaesthesia without complications. Conclusions There was no difference in cardiovascular function in horses undergoing elective surgery during isoflurane–medetomidine anaesthesia with SV in comparison with IPPV, provided the horses are maintained slightly hypercapnic. Clinical relevance In horses with health status ASA I and II, cardiovascular function under general anaesthesia is equal with or without IPPV if the PaCO₂ is maintained at 50–60 mmHg.