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Biomedical subjects

R E Clutton

Publications and source records attributed to R E Clutton.

At least 19 recordsLinked to original sources
PubMed2006

The early response to major trauma and intramedullary nailing.

The stress response to trauma is the summation of the physiological response to the injury (the 'first hit') and by the response to any on-going physiological disturbance or subsequent trauma surgery (the 'second hit'). Our animal model was developed in order to allow the study of each of these components of the stress response to major trauma. High-energy, comminuted fracture of the long bones and severe soft-tissue injuries in this model resulted in a significant tropotropic (depressor) cardiovascular response, transcardiac embolism of medullary contents and activation of the coagulation system. Subsequent stabilisation of the fractures using intramedullary nails did not significantly exacerbate any of these responses.

Animals↗
PubMed2006

Post anaesthetic colic in horses: a preventable complication?

REASONS FOR PERFORMING STUDY: There is little information on the prevalence of, and risk factors associated with, post anaesthetic colic (PAC) in horses undergoing nonabdominal operations. OBJECTIVES: To undertake the first prospective study of prevalence of PAC and identify risk factors in its development in nonabdominal procedures. METHODS: A multicentre prospective case-control study was conducted, on every horse undergoing anaesthesia for a nonabdominal procedure between April 2004 and June 2005. Colic cases were defined as any horse with recognised signs of abdominal pain within 72 h of general anaesthesia that could not be attributed to any concurrent disease. Five control horses per case were selected randomly from the study population at all hospitals. Multivariable logistic regression analysis was used to examine the relationship between predictor variables and the risk of developing PAC. RESULTS: The estimated mean prevalence of PAC in the study population was 5.2% (95% CI, 2.8, 8.0). However, the prevalence of colic varied between each centre. The most commonly diagnosed cause of colic was impaction. Multivariable analyses showed that the centre involved and the type of surgery performed were associated with an increased risk of PAC. Preoperative food deprivation and the use of opioid drugs were confounding factors. CONCLUSIONS: Prevalence of PAC varied significantly between the 4 hospitals studied; there may be hospital-related covariates that account for this. The type of surgery performed influenced the risk of PAC. POTENTIAL RELEVANCE: Identifying the risk factors for PAC is a prerequisite for its prevention. This study indicates horses at increased risk of PAC that might benefit from a more critical evaluation of post anaesthetic gastrointestinal function and/or the provision of preventative measures. Further investigation is required to explain the variation in prevalence of PAC between centres.

Anesthesia↗
PubMed2002

An experimental evaluation of a new intraparenchymal continuous compliance probe: preliminary studies.

The Spiegelberg automated compliance device offers practical benefits over the standard manual injection techniques for assessing volume-pressure status. Currently, however, the system relies on the insertion of an intraventricular catheter. If automated continuous measurement of intraparenchymal compliance could be achieved, then this would be a further practical advance. Automated measurements of compliance using a prototype intraparenchymal probe were assessed in comparison with the current intraventricular probe in a sheep model of diffusely raised ICP. The results show poor correlation between intraventricular compliance (IVC) and intraparenchymal compliance (IPC) at low levels of cerebral perfusion pressure (CPP). The IPC response to decreasing CPP beyond probable levels of blood flow autoregulation suggest that IPC is more dependent on local tissue perfusion factors, rather than overall physical compliance. Further evaluation of compliance in the intraparenchymal compartment versus intraventricular compliance will be needed before adaptation of the automated system for clinical application.

Animals↗
PubMed2000

Experimental evaluation of the Spiegelberg intracranial pressure and intracranial compliance monitor. Technical note.

The goal of this study was to compare the Spiegelberg intraventricular intracranial pressure (ICP)/intracranial compliance monitoring device, which features an air-pouch balloon catheter, with existing gold-standard methods of measuring ICP and intracranial compliance. A Spiegelberg intraventricular catheter, a standard intraventricular catheter, and a Codman intraparenchymal ICP microsensor were placed in five sheep, which previously had been given anesthetic and paralytic agents, to allow comparative measurement of ICP at incremental levels (range 5-50 mm Hg). Intracranial pressure measured using the Spiegelberg intraventricular air-pouch balloon catheter displayed a linear correlation with ICP measured using the standard intraventricular fluid-filled catheter (r2 = 0.9846, p < 0.001; average bias -0.74 mm Hg), as well as with ICP measured using the Codman intraparenchymal strain-gauge sensor (r2 = 0.9778, p < 0.001; average bias 0.01 mm Hg). Automated measurements of intraventricular compliance obtained using the Spiegelberg compliance device were compared with compliance measurements that were made using the gold-standard manual cerebrospinal fluid bolus injection technique at ICPs ranging from 5 to 50 mm Hg, and a linear correlation was demonstrated between the two methods (r2 = 0.7752, p < 0.001; average bias -0.019 ml/mm Hg). The Spiegelberg air-pouch ICP/compliance monitor provides ICP and compliance data that are very similar to those obtained using both gold-standard methods and an intraparenchymal ICP monitor over a range of pathophysiological ICPs. The automated closed Spiegelberg system offers practical advantages for the measurement of intraventricular compliance. Assessment of the clinical utility and robustness of the Spiegelberg system, together with the development of an intraparenchymal device, would enhance the clinical utility of automated compliance measurement and expand the range of its applications.

Animals↗
PubMed1998

Effect of muscle injection site and drug temperature on pre-anaesthetic sedation in pigs.

The responses of 83 Meishan gilts given azaperone (1.0 mg/kg) and ketamine (5 mg/kg) intramuscularly at one of four sites: the cervical muscles (20); the triceps muscle (m triceps brachii) (20); the middle gluteal muscle (m gluteus medius) (22); and the fascia lata muscle (m fascia lata) (21) were recorded. There were more reactions to the injection into the fascia lata muscle than to injections into the middle gluteal muscle and the triceps muscle (P = 0.024) and fewest after injections into the cervical muscles (P = 0.013). The injection site did not influence the time from injection to recumbency but there was least variability with the fascia lata muscle. The degree of sedation achieved, and the response to venous cannulation were similar in all four groups. There were no long-term complications (lameness or abscess formation) associated with the injections at any of the sites. In a second study with 68 pigs the same drug mixture was injected into the triceps muscle at either 6 to 8 degrees C (23), 19 to 22 degrees C (23) or 38.5 to 40.5 degrees C (22). There was no significant difference (P = 0.078) between the numbers of responses to the injections at each temperature. Mean time to recumbency was shortest with the injections at the highest temperature although the differences were not statistically significant (P = 0.498). The degree of sedation achieved, the response to venous cannulation and the incidence of complications were similar in all three groups.

Absorption↗
PubMed1998

Haemodynamic effects of a sixty minute infusion of dopamine hydrochloride in horses anaesthetised with halothane.

To describe the haemodynamic effects of a 60 min infusion of dopamine 4 microg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 microg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2 between 4.6-5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measured using intracardiac strain gauge transducers sited in the left and right ventricle, aorta, and pulmonary artery. Left ventricular pressure was differentiated to obtain maximal rate of increase of intraventricular pressure (LVdp/dtmax). Transoesophageal Doppler echocardiography was performed to measure maximum aortic blood flow velocity (vmax) and acceleration (dv/dtmax), left ventricular velocity time integral (vTI) and cardiac output (CO), and left ventricular pre-ejection period (PEP) and ejection time (ET). Measurements were made during the 60 min infusion, and for 30 min after the infusion was discontinued. Infusion of dopamine 4 microg/kg/min significantly decreased mean aortic pressure, while left and right ventricular end-diastolic pressure and mean pulmonary artery pressure remained unchanged. There was a small, but significant, increase in heart rate during dopamine infusion. Maximum acceleration of aortic blood flow, CO and vTI were also significantly increased by dopamine infusion. Maximal rate of increase of intraventricular pressure (LVdp/dtmax) was significantly decreased 10 min after commencing infusion, but then returned to baseline for the remainder of the study. Left ventricular pre-ejection period (PEP) decreased during dopamine infusion whilst ejection time (ET) significantly increased. All measured variables except LVET had returned to baseline values within 30 min of discontinuing the infusion. This study demonstrated beneficial effects of dopamine infusion upon left ventricular systolic function. However, the therapeutic value of the drug is likely to be limited in clinical anaesthesia due to the simultaneous falls in arterial blood pressure which accompany its administration.

Anesthesia, Inhalation↗
PubMed1998

Anaesthesia for lambs undergoing spinal surgery: a case series.

Six 1-month-old lambs were anaesthetized for cervical spinal cord surgery. Anaesthesia was induced with intravenous midazolam (0.5 mg/kg) then halothane delivered by mask in an O2-N2O mixture. After endotracheal intubation, the lungs were ventilated mechanically and anaesthesia maintained with halothane and nitrous oxide. Buprenorphine and flunixin were given before and after surgery, and the wound margin was infiltrated with 0.5% bupivacaine solution. Neuromuscular block was produced with repeated injections of atracurium; neuromuscular transmission was restored with edrophonium. Lambs made a rapid recovery without obvious signs of discomfort, sedation, or weakness after operations lasting up to 156 min. Anaesthesia was induced in a seventh lamb using etomidate, which probably contributed to death during recovery from anaesthesia.

Anesthesia↗
PubMed1998

Temporal effects of an infusion of dobutamine hydrochloride in horses anesthetized with halothane.

OBJECTIVE: To evaluate temporal hemodynamic effects of dobutamine in horses anesthetized with halothane. ANIMALS: 8 adult Thoroughbreds. PROCEDURE: Anesthesia was induced by i.v. administration of romifidine and ketamine and maintained using halothane in oxygen. After 60 minutes, dobutamine was administered i.v. for 60 minutes at 4 micrograms/kg of body weight/min. Measurements of left ventricular function were obtained by transesophageal echocardiography and cardiac catheterization. RESULTS: Mean, systolic, diastolic, aortic, pulmonary arterial, and left and right ventricular end-diastolic and systolic pressures, maximal rate of increase of intraventricular pressure (LVdp/dtmax), maximum acceleration (dv/dtmax) and velocity (Vmax) of aortic blood flow, cardiac output, and left ventricular velocity time integral were significantly increased, whereas left ventricular pre-ejection period and ejection time significantly decreased. Cardiac output, LVdp/dtmax, Vmax, and dv/dtmax increased throughout infusion. Heart rate was significantly less after 10 minutes and significantly greater at 60 minutes than before infusion. Supraventricular tachycardia developed in 2 horses. Cardiac output, LVdp/dtmax, Vmax, dv/dtmax, left ventricular and aortic systolic pressures, and mean aortic pressure had not returned to control values 30 minutes after infusion was discontinued. CONCLUSIONS: At this dosage, dobutamine did not achieve peak effect on many hemodynamic variables within 40 minutes of commencing infusion, and effects of 60-minute infusion persisted after infusion was discontinued. CLINICAL RELEVANCE: Dobutamine has a hemodynamic profile suited to treatment of low cardiac output in anesthetized horses; however, sustained administration may be associated with supraventricular tachycardia and a protracted time to peak effect.

Anesthesia, Inhalation↗
PubMed1997

Comparison of three injectable anaesthetic techniques in pigs.

Forty-six near-adult pigs (mean age 10 months, mean weight 156 kg) were anaesthetised for laparoscopy. After intramuscular azaperone (1.0 mg/kg) and ketamine (2.5 mg/kg), 14 of the pigs received intravenous etomidate (200 micrograms/kg) and midazolam (100 micrograms/kg) and 17 were given ketamine (2 mg/kg) and midazolam (100 micrograms/kg). The other 15 pigs were anaesthetised with pentobarbitone (15 to 20 mg/kg) without pre-anaesthetic medication. The duration and adequacy of anaesthesia, recovery rate, and seven physiological variables (ECG, heart rate, indirect arterial blood pressure, respiratory rate, minute volume, mean end-tidal carbon dioxide concentration and percentage oxygen saturation of haemoglobin) were compared. Repeated injections were needed in 29 of the 46 cases. Pentobarbitone was the least satisfactory drug because although the haemodynamic variables were greater, it caused more respiratory depression and a higher overall complication rate than the other methods. Apnoea occurred in two pigs, and was fatal in one, and positive pressure ventilation with oxygen was needed in three others. Intubation conditions were poorer and the times to standing, walking and rooting were longer in the pigs anaesthetised with pentobarbitone.

Adjuvants, Anesthesia↗
PubMed1997

Temporal effects of an infusion of dopexamine hydrochloride in horses anesthetized with halothane.

OBJECTIVE: To evaluate the hemodynamic effects of a 60-minute infusion of dopexamine in horses anesthetized with halothane. ANIMALS: 7 adult Thoroughbreds. PROCEDURE: Measurements of left ventricular function obtained by transesophageal Doppler echocardiography and cardiac catheterization. RESULTS: Infusion of dopexamine (4 micrograms/kg of body weight/min) significantly increased heart rate, cardiac output, maximal rates of increase and decrease of left ventricular pressure, and maximal acceleration and maximal velocity of aortic blood flow. Left ventricular ejection time significantly increased, and pre-ejection period decreased during the infusion. Cardiac output, maximal rate of increase of left ventricular pressure, and maximal acceleration continued to increase as the infusion progressed. Right ventricular end-diastolic pressure was significantly decreased after 20 minutes of infusion and decreased progressively throughout the remaining time of infusion. Many hemodynamic variables, including right ventricular end-diastolic pressure, had not returned to control values 30 minutes after the infusion was discontinued. A number of undesirable adverse effects were observed in horses receiving dopexamine infusion; during administration, profuse sweating occurred in every horse. In 6 horses, recovery from anesthesia was associated with excitement and violent shivering. Colic developed in 2 horses within 3 hours of recovery. CONCLUSIONS: Dopexamine (4 micrograms/kg/min) does not achieve a peak effect on many hemodynamic variables within a short period of commencing administration, and the effects of infusion may persist for extended periods after drug administration is discontinued. CLINICAL RELEVANCE: Dopexamine has a hemodynamic profile suited to treatment of low cardiac output in anesthetized horses; however, at the dosage rate studied (4 micrograms/kg/min), its administration was associated with a number of undesirable adverse effects which could preclude its clinical use.

Anesthetics, Inhalation↗
PubMed1996

Measurement of cardiac output by transoesophageal Doppler echocardiography in anaesthetized horses: comparison with thermodilution.

In order to determine if transoesophageal Doppler echocardiography could be used to estimate cardiac output in anaesthetized horses, we have compared the technique with estimations of cardiac output by thermodilution in eight healthy adult thoroughbreds. Measurements of aortic blood flow velocity were made by high pulse repetition frequency (HPRF) and continuous wave (CW) Doppler echocardiography from a 3.5-MHz transoesophageal probe. Cardiac output was increased during the study by administration of dobutamine, providing a range of cardiac output measurements by thermodilution from 15.0 to 64.4 liter min-1. Estimations derived from CW Doppler overestimated cardiac output compared with thermodilution (bias = 4.0 litre min-1). Estimations from HPRF Doppler echocardiography more closely reflected measurements obtained by thermodilution (bias = 0.7 litre min-1). Limits of agreement between the techniques were similar for both modes of insonation (HPRF = -7.7 to 9.1 litre min-1, CW = -4.9 to 12.8 litre min-1). There were significant differences in bias between both Doppler techniques and thermodilution for individual horses. As a result, for any individual horse, limits of agreement between the techniques were closer (HPRF = +/- 6.4 litre min-1, CW = +/- 7.6 litre min-1). We conclude that transoesophageal echocardiography provided an alternative, effective and non-invasive method for measurement of cardiac output in anaesthetized horses.

Anesthesia, General↗
PubMed1995

Repair of the facial nerve in the cerebellopontine angle using freeze-thawed skeletal muscle autografts. An experimental surgical study in the sheep.

Six adult blackface sheep underwent repair of the transected facial nerve in the cerebellopontine angle using short freeze-thawed muscle autografts. A typical facial palsy was observed on the side of the intervention immediately after operation. The sheep were allowed to recover for one year by which time clinical observation showed a complete recovery of the facial palsy in 5 sheep and a partial recovery in the remaining sheep. Under general anaesthesia function of the repaired VIIth nerve and the normal contralateral facial nerve were assessed using electrophysiological stimulating and recording techniques. These studies showed restoration of facial nerve continuity to have taken place with functional reinnervation of target facial muscles. Electrophysiological indices of nerve function were consistent with those expected after repair of any peripheral nerve. Morphometric study of the nerves after their removal showed structural changes which though quantitatively different from those of normal nerve were consistent with those seen in other sites and studies where nerves have been repaired. This technique is discussed as a possible treatment for facial nerves whose continuity is disrupted during the removal of cerebellopontine angle tumours.

Animals↗
PubMed1995

Feasibility of transoesophageal echocardiography for evaluation of left ventricular performance in anaesthetised horses.

Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 micrograms/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient of variation and 95% confidence intervals were narrower for the Doppler variables than for those obtained from cardiac catheterisation. For each horse the anaesthetic to anaesthetic repeatability of the Doppler indices of left ventricular function, exceeded that of maximum rate of rise of left ventricular pressure (LVdp/dtmax). The horse to horse variability was significant for heart rates Vmax, dv/dtmax, and VTI. After dobutamine infusion there were significant changes in all measured variables except heart rate, VTI and CO. The % change that occurred exceeded the predicted 95% confidence intervals for single measurements in all significantly affected variables. This suggests Doppler indices of cardiac performance may be useful to assess changes in haemodynamic function. Passage of the probe into the oesophagus was not associated with serious adverse effects. Mild serous nasal discharge was visible for up to 24 h after the horses recovered from anaesthesia. Mild nasal haemorrhage occurred on 5 occasions during probe insertion. It is concluded that transoesophageal Doppler echocardiography provides a minimally invasive, continuous method for monitoring left ventricular systolic performance in anaesthetised horses.

Adrenergic beta-Agonists↗
PubMed1994

Edrophonium for the antagonism of neuromuscular blockade in dogs.

Neuromuscular, electrocardiographic and autonomic nervous changes were studied when edrophonium and four combinations of edrophonium and atropine were used to antagonise vecuronium-induced neuromuscular blockade in 87 dogs anaesthetised with halothane. Edrophonium (500 micrograms/kg body-weight) was given alone, or with atropine (40 micrograms/kg) or one minute after a dose of 600 micrograms of atropine, and a lower dose of edrophonium (250 micrograms/kg) was used with high (40 micrograms/kg) and low (20 micrograms/kg) doses of atropine. The neuromuscular blockade was antagonised when some recovery was present. The reversal was rapid and complete in 75 cases, but the remaining 12 dogs which received the low dose of edrophonium required a second injection. Trials with the high dose of edrophonium alone were discontinued because cardiac arrest occurred in one dog and bronchosecretion with profuse salivation in another. The heart rate increased with the low dose of edrophonium and the high dose of atropine, and increased and then decreased when edrophonium was followed by 600 micrograms of atropine. The heart rate was stable when the high and low doses of atropine and edrophonium were matched. All the treatments caused atrioventricular blockade. Non-cardiac autonomic changes (salivation and bronchosecretion) occurred in only two of the 87 dogs.

Anesthesia, Intravenous↗