Dissociative Anaesthesia During Field and Hospital Conditions for Castration of Colts

The principal aim of this study was to evaluate dissociative anaesthesia for castration of colts during field conditions. Three dissociative anaesthetic protocols were evaluated during castration of colts in an animal hospital. The protocol considered to be the most suitable was thereafter evaluated during castration of colts under field conditions. Respiratory and haemodynamic parameters and the response to surgery were determined during anaesthesia. All horses breathed air spontaneously during anaesthesia. Under hospital conditions 26 colts were randomised to receive one of three anaesthetic protocols: Romifidine and tiletamine-zolazepam (RZ); acepromazine, romifidine and tiletamine-zolazepam (ARZ); or acepromazine, romifidine, butorphanol and tiletamine-zolazepam (ARBZ). The surgeon was blinded to the anaesthetic protocol used and decided whether supplemental anaesthesia was needed to complete surgery. Under field conditions 31 colts were castrated during anaesthesia with the ARBZ protocol. All inductions, anaesthesia and recoveries were calm and without excitation under both hospital and field conditions. Surgery was performed within 5–20 minutes after the horses had assumed lateral recumbency during both hospital and field castrations. Under hospital conditions some horses needed supplemental anaesthesia with all three anaesthetic protocols to complete surgery. Interestingly, none of the horses castrated with protocol ARBZ under field conditions needed additional anaesthesia. Cardiorespiratory changes were within acceptable limits in these clinically healthy colts

Effect of sedation with detomidine and butorphanol on pulmonary gas exchange in the horse

<p>Abstract</p> <p>Background</p> <p>Sedation with α₂-agonists in the horse is reported to be accompanied by impairment of arterial oxygenation. The present study was undertaken to investigate pulmonary gas exchange using the Multiple Inert Gas Elimination Technique (MIGET), during sedation with the α₂-agonist detomidine alone and in combination with the opioid butorphanol.</p> <p>Methods</p> <p>Seven Standardbred trotter horses aged 3–7 years and weighing 380–520 kg, were studied. The protocol consisted of three consecutive measurements; in the unsedated horse, after intravenous administration of detomidine (0.02 mg/kg) and after subsequent butorphanol administration (0.025 mg/kg). Pulmonary function and haemodynamic effects were investigated. The distribution of ventilation-perfusion ratios (V_A/Q) was estimated with MIGET.</p> <p>Results</p> <p>During detomidine sedation, arterial oxygen tension (PaO₂) decreased (12.8 ± 0.7 to 10.8 ± 1.2 kPa) and arterial carbon dioxide tension (PaCO₂) increased (5.9 ± 0.3 to 6.1 ± 0.2 kPa) compared to measurements in the unsedated horse. Mismatch between ventilation and perfusion in the lungs was evident, but no increase in intrapulmonary shunt could be detected. Respiratory rate and minute ventilation did not change. Heart rate and cardiac output decreased, while pulmonary and systemic blood pressure and vascular resistance increased. Addition of butorphanol resulted in a significant decrease in ventilation and increase in PaCO₂. Alveolar-arterial oxygen content difference P(A-a)O₂remained impaired after butorphanol administration, the V_A/Q distribution improved as the decreased ventilation and persistent low blood flow was well matched. Also after subsequent butorphanol no increase in intrapulmonary shunt was evident.</p> <p>Conclusion</p> <p>The results of the present study suggest that both pulmonary and cardiovascular factors contribute to the impaired pulmonary gas exchange during detomidine and butorphanol sedation in the horse.</p

Sedation and dissociative anaesthesia in the horse

The overall aim of this investigation was to study the effects of different drug combinations for premedication and dissociative anaesthesia, to examine their suitability for field conditions and their ability to maintain cardiorespiratory function and provide sufficient analgesia for common, but challenging procedures such as castration. Haemodynamic parameters, pulmonary ventilation-perfusion relationships, and clinical effects were studied during sedation and dissociative anaesthesia. The effects of additional premedication and prolongation of dissociative anaesthesia and response to surgery were evaluated. The cardiorespiratory effects of romifidine and tiletamine-zolazepam anaesthesia did not differ significantly from those of prolonged romifidine and ketamine anaesthesia. Prolongation of anaesthesia with ketamine alone after romifidine/ketamine resulted in a poor quality of anaesthesia. There was a decrease in arterial oxygenation during sedation with a2-agonists, which was mainly attributed to a reduced cardiac output and increased ventilation-perfusion mismatch. During dissociative anaesthesia the cardiac output did normalise, but arterial oxygenation was further impaired as a result of increased intrapulmonary shunt and increased ventilation-perfusion mismatch. Administration of acepromazine before sedation with romifidine and butorphanol resulted in better maintenance of circulation and partly prevented the anaesthesia-induced ventilation-perfusion disturbances and fall in arterial oxygen tension. Although the arterial oxygenation was further impaired during anaesthesia and recumbency compared to that during sedation, the oxygen delivery did not decrease further. On the contrary, the arterial-mixed venous oxygen content difference and mixed venous oxygen tension remained closer to standing unsedated values during anaesthesia than in the sedated horse. Breathing high oxygen concentrations (>95% oxygen) during dissociative anaesthesia improved arterial oxygenation compared to air breathing (21% oxygen), but concomitantly increased intrapulmonary shunt and introduced hypoventilation. The intrapulmonary shunt created during anaesthesia with high oxygen concentrations persisted when the horses returned to air breathing, possibly indicating that resorption atelectasis produced during high oxygen breathing subsequently persisted during anaesthesia and recumbency. Tiletamine-zolazepam anaesthesia, after premedication with acepromazine, romifidine and butorphanol, produced anaesthesia and analgesia sufficient for castration of colts under field conditions. When the same regimen was used in the animal hospital there was a need for supplementary anaesthesia in some cases to complete surgery. The induction, anaesthesia and recovery were calm and without excitation in all colts both under hospital and field conditions. Cardiorespiratory changes during air breathing were within acceptable limits in these clinically healthy horses

Hot ice : en upplevelsebyggnad som integrerar arkitektur och teknik för en hållbar utveckling

Validerat; 20101217 (root

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 (PaCO(2)) 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 PaCO(2) is maintained at 50-60 mmHg