Cardiovascular effects of desflurane in mechanically ventilated calves

Transient Pulmonary Artery Hypertension in Holstein Neonate Calves

Simple Summary

At birth, calves are challenged to maintain their vital functions that were previously supported by the placenta of cows. Failures in the neonatal adaptation process can occur during this and can cause the death of neonates. The present study aimed at the invasive hemodynamic evaluation of calves during the first 30 days of life to elucidate the changes in calves during this stage of life. In conclusion, the results of this research show a transient pulmonary arterial hypertension during the process of adapting to extrauterine life.

Abstract

The neonatal period is a challenging phase for calves, and during this phase constant adaptations are required. The aim of the present study was to evaluate the invasive hemodynamics with the Swan-Ganz catheter in neonate calves to understand adaptive changes during the first 30 days of life. A prospective and observational study was conducted with 10 Holstein calves. Assessments of the right atrial pressure (RAP), right ventricular pressure (RVP), pulmonary artery pressure (PAP), pulmonary capillary pressure (PW), cardiac output (CO), heart rate (HR), pulmonary vascular resistance (PVR), and blood gas levels were performed. The analyses of PAP, PVR, PW, HR, sO₂, and arterial blood gases differed (p < 0.05) between the evaluated periods. Our results indicated transient pulmonary artery hypertension during the process of extrauterine adaptation during the first 30 days of life. This hypertension must be considered as physiological and consequent to the neonatal adaptation process.

Mitigation of electroencephalographic and cardiovascular responses to castration in Bos indicus bulls following the administration of either lidocaine or meloxicam

OBJECTIVE

To investigate the mitigating effects of administration of local anaesthetic or systemic meloxicam on the electroencephalographic (EEG) and cardiovascular responses during surgical castration of Bos indicus bull calves.

STUDY DESIGN

Prospective, randomized, experimental study.

ANIMALS

Thirty-six 6-8 month-old Bos indicus bull calves, with a mean ± standard deviation weight of 237 ± 19 kg.

METHODS

Animals were allocated randomly to three groups of 12 (group L, 260 mg of 2% lidocaine subcutaneously and intratesticularly 5 minutes prior to castration; group M, 0.5 mg kg^-1 of meloxicam subcutaneously 30 minutes prior to castration; group C, no preoperative analgesia administered). Anaesthesia was induced and maintained with halothane (0.9-1.1%) in oxygen. Electroencephalogram, heart rate (HR) and mean blood pressure (MAP) were recorded for 300 seconds prior to (baseline, B) and from the start of surgery (first testicle removal, T1). HR and MAP were compared at 10 second intervals for 90 seconds from the start of T1. Median frequency (F₅₀), spectral edge frequency (F₉₅) and total power of the EEG (P_tot) were analysed using area under the curve comparing T1 to B.

RESULTS

All EEG variables were significantly different between B and T1 (p ≤ 0.0001). No differences in F₅₀ were found between groups during T1 (p = 0.6491). F₉₅ and P_tot were significantly different between group L and groups C and M during T1 (p = 0.0005 and 0.0163, respectively). There were transient significant changes in HR and MAP in groups L and M compared to group C during the 20-50 second periods.

CONCLUSIONS

The EEG changes indicate nociceptive responses in all three groups during surgical castration, greater in group L compared to groups C and M. Both analgesics attenuated the peracute cardiovascular response. Lidocaine and meloxicam administered prior to castration attenuated these responses in Bos indicus bull calves.

CLINICAL RELEVANCE

These findings provide support for the preoperative administration of lidocaine and potentially meloxicam for castration in Bos indicus bull calves.

Continuous infusion of propofol in calves: bispectral index and hemodynamic effects

OBJECTIVE

To assess the bispectral index (BIS) and the hemodynamic effects of propofol administered by continuous infusion at different rates in calves.

STUDY DESIGN

Experimental crossover study.

ANIMALS

Eight intact male Dutch calves, aged 6-12 months and weighing 84-124 kg.

METHODS

The calves were anesthetized with propofol (5 mg kg(-1) ) intravenously (IV), and after endotracheal intubation, positioned in right lateral recumbency and allowed to breathe ambient air. Anesthesia was maintained by continuous infusion of propofol, administered IV with an infusion pump at 0.6 mg kg(-1)  minute(-1) (treatment G6) or 0.8 mg kg(-1)  minute(-1) IV (treatment G8), for 60 minutes. The eight animals were anesthetized twice, 1 week apart. The following hemodynamic variables and BIS were assessed before the induction of anesthesia (baseline) and 15, 30, 45, and 60 minutes after beginning the infusion of propofol: heart rate, systolic, diastolic and mean arterial pressures, cardiac output, mean pulmonary artery pressure, cardiac index, stroke index, pulmonary vascular resistance index, and systemic vascular resistance index, BIS, electromyography, and signal quality index.

RESULTS

The continuous infusions of propofol at different rates did not alter BIS variables during the infusion time between dose rates, and no clinically significant hemodynamic changes were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

A continuous infusion of propofol at 0.6 or 0.8 mg kg(-1)  minute(-1) caused minimal hemodynamic changes without clinical relevance in calves. BIS could not be reliably used to discriminate the anesthetic depth during the two propofol infusion rates.

Evaluation of the isoflurane-sparing effects of lidocaine infusion during umbilical surgery in calves

OBJECTIVE

To evaluate the isoflurane-sparing effects of lidocaine administered by constant rate infusion (CRI) during umbilical surgery in calves.

STUDY DESIGN

Randomized 'blinded' prospective clinical study.

ANIMALS

Thirty calves (mean 4.7 ± SD 2.5 weeks old) undergoing umbilical surgery.

METHODS

After premedication with xylazine (0.1 mg kg(-1) , IM), anaesthesia was induced with ketamine (4 mg kg(-1) , IV) and maintained with isoflurane in O(2) administered through a circle breathing system. The calves were assigned randomly to receive a bolus of 2 mg kg(-1) lidocaine IV after induction of anaesthesia, followed by CRI of 50 μg kg(-1) minute(-1) (group L, n=15) or a bolus and CRI of 0.9% sodium chloride (NaCl, group S, n=15). End-tidal isoflurane was adjusted to achieve adequate depth of anaesthesia. Heart rate, direct arterial blood pressure and body temperature were measured intraoperatively. Groups were compared by t- tests, anova or Mann-Whitney rank sum test as appropriate.

RESULTS

The end-tidal concentration of isoflurane (median, IQR) was significantly lower in group L [1.0% (0.94-1.1)] compared to group S [1.2% (1.1-1.5)], indicating a 16.7% reduction in anaesthetic requirement during lidocaine CRI. Cardiopulmonary parameters and recovery times did not differ significantly between groups.

CONCLUSION AND CLINICAL RELEVANCE

Lidocaine CRI may be used as a supplement to inhalation anaesthesia during umbilical surgery in calves in countries where such a protocol would be within the legal requirements for veterinary use in food animals. This study did not show any measurable benefit to the calves other than a reduction in isoflurane requirement.