Cardiac Oscillations Research Articles

Activation of the hypothalamic paraventricular nucleus by forebrain hypertonicity selectively increases tonic vasomotor sympathetic nerve activity.

We recently reported that mean arterial pressure (MAP) is maintained in water-deprived rats by an irregular tonic component of vasomotor sympathetic nerve activity (SNA) that is driven by neuronal activity in the hypothalamic paraventricular nucleus (PVN). To establish whether generation of tonic SNA requires time-dependent (i.e., hours or days of dehydration) neuroadaptive responses or can be abruptly generated by even acute circuit activation, forebrain sympathoexcitatory osmosensory inputs to PVN were stimulated by infusion (0.1 ml/min, 10 min) of hypertonic saline (HTS; 1.5 M NaCl) through an internal carotid artery (ICA). Whereas isotonic saline (ITS; 0.15 M NaCl) had no effect (n = 5), HTS increased (P < 0.001; n = 6) splanchnic SNA (sSNA), phrenic nerve activity (PNA), and MAP. Bilateral PVN injections of muscimol (n = 6) prevented HTS-evoked increases of integrated sSNA and PNA (P < 0.001) and attenuated the accompanying pressor response (P < 0.01). Blockade of PVN NMDA receptors with d-(2R)-amino-5-phosphonovaleric acid (AP5; n = 6) had similar effects. Analysis of respiratory rhythmic bursting of sSNA revealed that ICA HTS increased mean voltage (P < 0.001) without affecting the amplitude of inspiratory or expiratory bursts. Analysis of cardiac rhythmic sSNA likewise revealed that ICA HTS increased mean voltage. Cardiac rhythmic sSNA oscillation amplitude was also increased, which is consistent with activation of arterial baroreceptor during the accompanying pressor response. Increased mean sSNA voltage by HTS was blocked by prior PVN inhibition (muscimol) and blockade of PVN NMDA receptors (AP5). We conclude that even acute glutamatergic activation of PVN (i.e., by hypertonicity) is sufficient to selectively increase a tonic component of vasomotor SNA.

A computational fluid dynamics study on hemodynamics for different locations of the distal anastomosis of a bypass nearby a collateral vessel in the femoropopliteal area.

Revascularization of the femoropopliteal sector is often performed by the placement of a bypass. In this paper, we have studied the effects of hemodynamics on patency of the bypass for different positions of the distal anastomosis close to a collateral artery. Computational fluid dynamics (CFD) are used for this study. The cardiac cycle-averaged wall shear stress (WSS) and oscillation index (OSI) have been analyzed. Low WSS and high OSI may increase the risk of intimal hyperplasia (IH), which may reduce bypass patency. From the CFD simulations, spots of low WSS and high OSI are found within and near the entrance of the collateral artery, near the suture line, at the floor, toe, and heel. We regarded flow ratios of 20:80 and of 35:65. It is found that for the high flow ratio anastomosis located proximal to the collateral artery is clearly more advantageous. However for the low flow ratio anastomosis located distal to the collateral artery seems to be slightly more advantageous, the results are less conclusive. One of the studied flow geometries has been validated by in vitro experiments using a time resolved particle image velocimetry technique. Velocity fields from these experiments are in good agreement with the CFD results.

A minimally invasive method for clinical trans-diaphragmatic pressure measurement in anaesthetized dogs

ObjectiveTo measure trans-diaphragmatic pressures, as an indication of diaphragmatic contractility, in anaesthetized dogs breathing normally, or during inspiratory obstruction (Mueller’s manoeuvre) in order to assess if the method is practicable for use in clinical circumstances. Study designPilot study. AnimalsTwenty eight client-owned dogs, ASA I or II, 1–10 years old, 5–30 kg bodyweight, which required anaesthesia for surgery, and were to be positioned in lateral recumbency. MethodsFollowing a standardized regimen of premedication and anaesthetic induction, anaesthesia was stabilized and maintained with isoflurane. Two commercially available balloon catheters were introduced orally, and advanced, one into the stomach and one into the mid-third of the oesophagus. Oesophageal and gastric pressures were measured from these catheters, and trans-diaphragmatic pressure (Pdi) calculated and recorded continuously. At three separate time points during anaesthesia, for one breath, inspiration was obstructed (Mueller’s manoeuvre) and Pdi was measured. ResultsPlacement of the catheters in the stomach was not easy, and failed in three cases. In five dogs, their size resulted in failure of correct placement of catheters. Good traces of all three pressures reflecting respiratory cycles were obtained from 20 dogs. During normal spontaneous breathing (mean ± SD [range]) Pdi was 5 ± 2.1 (3–10) mmHg. During Mueller’s manoeuvre, Pdi was 14.6 ± 4.5 (9–21) mmHg. Abnormal waveforms were seen included cardiac oscillations (five dogs), inadequate intra-gastric pressure tracing (one dog), deflections with a double peak (one dog), and multiple artifacts when there was increased heart rate and tachypnoea (two dogs in response to surgery). Conclusions and clinical relevanceMeasurement of trans-diaphragmatic pressure with balloon catheters was practicable in suitably sized dogs anaesthetized for clinical purposes and might be a useful tool in the assessment of diaphragmatic function. A range of catheters are required if the technique is to work in all dogs.

Cardio-Respiratory Coordination Increases during Sleep Apnea

Cardiovascular diseases are the main source of morbidity and mortality in the United States with costs of more than $170 billion. Repetitive respiratory disorders during sleep are assumed to be a major cause of these diseases. Therefore, the understanding of the cardio-respiratory regulation during these events is of high public interest. One of the governing mechanisms is the mutual influence of the cardiac and respiratory oscillations on their respective onsets, the cardio-respiratory coordination (CRC). We analyze this mechanism based on nocturnal measurements of 27 males suffering from obstructive sleep apnea syndrome. Here we find, by using an advanced analysis technique, the coordigram, not only that the occurrence of CRC is significantly more frequent during respiratory sleep disturbances than in normal respiration (p-value<10−51) but also more frequent after these events (p-value<10−15). Especially, the latter finding contradicts the common assumption that spontaneous CRC can only be observed in epochs of relaxed conditions, while our newly discovered epochs of CRC after disturbances are characterized by high autonomic stress. Our findings on the connection between CRC and the appearance of sleep-disordered events require a substantial extension of the current understanding of obstructive sleep apneas and hypopneas.

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What's in this issue?

Quasi-periodic modeling for heart sound localization and suppression in lung sounds

We present a novel approach to treating lung sounds contaminated by heart sounds by means of quasi-periodic signal modeling. Heart sounds are described through the long and short-term quasi-periodicity generated by cardiac cycle repetition and oscillations caused by valves openings and closures, respectively. In terms of signals, these quasi-periodicities drive time-variant HS envelope and phase which are modeled by single and piecewise time polynomials, respectively. Single polynomials account for slow and continuous envelope time variations, while piecewise polynomials capture fast and abrupt phase changes in short time intervals. Such a compact signal description provides an efficient way to fundamental heart sound (FHS) components localization and posterior removal from lung sounds. The results show that the proposed method outperforms two reference methods for medium (15ml/s/kg) and high (22.5ml/s/kg) air flow rates.

Sympathetic network drive during water deprivation does not increase respiratory or cardiac rhythmic sympathetic nerve activity

Effects of water deprivation on rhythmic bursting of sympathetic nerve activity (SNA) were investigated in anesthetized, bilaterally vagotomized, euhydrated (control) and 48-h water-deprived (WD) rats (n = 8/group). Control and WD rats had similar baseline values of mean arterial pressure, heart rate, end-tidal CO2, and central respiratory drive. Although integrated splanchnic SNA (sSNA) was greater in WD rats than controls (P < 0.01), analysis of respiratory rhythmic bursting of sSNA revealed that inspiratory rhythmic burst amplitude was actually smaller (P < 0.005) in WD rats (+68 ± 6%) than controls (+208 ± 20%), and amplitudes of the early expiratory (postinspiratory) trough and late expiratory burst of sSNA were not different between groups. Further analysis revealed that water deprivation had no effect on either the amplitude or periodicity of the cardiac rhythmic oscillation of sSNA. Collectively, these data indicate that the increase of sSNA produced by water deprivation is not attributable to either increased respiratory or cardiac rhythmic burst discharge. Thus the sympathetic network response to acute water deprivation appears to differ from that of chronic sympathoexcitation in neurogenic forms of arterial hypertension, where increased respiratory rhythmic bursting of SNA and baroreflex adaptations have been reported.

Inadvertent Triggering of the Ventilator Caused By Surgically Placed Pacer Wires

Inadvertent ventilator triggering can occur for various reasons. Leaks in the ventilator circuit, endotracheal tube leaks, tracheal cuff leaks, cardiac oscillations, water condensate causing oscillations in the circuit tubing, ventilator expiratory valve integrity, and overly sensitive triggering mechanism settings may precipitate this phenomena. We present a case of inadvertent ventilator triggering caused by electrical stimulation of the diaphragm from surgically placed pacing wires post cardiothoracic surgery. A 47-year-old woman underwent surgical placement of a left (LVAD) and right (RVAD) ventricular assist device for severe end stage cardiomyopathy, as a bridge to cardiac transplantation. The patient was observed to have inadvertent ventilator triggering while deeply sedated postoperatively. The ventilator set respiratory rate was 16 breaths/min, with patient respiratory rate of 30 breaths/min while deeply sedated. Upon assessment of ventilator waveforms and arterial blood gas revealing a profound respiratory alkalosis, the pressure/time waveform demonstrated a -2 cm H(2)O decrease in pressure prior to each cycled breath. The ventilator was subsequently changed from flow trigger sensitivity of 3 L/min to pressure trigger sensitivity of -3 cm H(2)O to eliminate the autotriggering. Later in the patient's ICU stay, inadvertent ventilator triggering was again observed. Further adjustment of the pressure trigger sensitivity to -3 cm H(2)O eliminated the autotriggering. Clinical assessment found the pacing wires were responsible for stimulating the patient's diaphragm, therefore causing airway pressure decreases and premature breath delivery. Once the electrical amplitude of the pacemaker was decreased, the inadvertent ventilator triggering resolved and normal trigger sensitivity and pH was restored.

Ventilation heterogeneity: small length scales, big challenges

the distribution of regional ventilation is heterogeneous in normal lung and increases dramatically under pathological conditions. This has been demonstrated both in humans and in animal models using a number of different imaging techniques. General anesthesia and mechanical ventilation can

Altered Short-Term Dynamics of Cardio-Respiratory Interaction during Propofol-Induced Yawning

"Cardiac and respiratory oscillations have been shown to interact with each other. This interaction could reflect autonomic nervous system functionality. Propofol-induced yawning during anesthesia induction seems to be associated with sympathetic activation. Presumptively, there is high linearity among interaction of different physiologic system behaviors. Recently, investigators used coherence analysis to quantify the existence and strength of linearity between system signals for study of cardio-respiratory interaction under different physiological conditions. In this investigation, we used a method of time-frequency coherence function to analyze ECG and respiration signals to investigate the linearity of cardio-respiratory dynamics in patients undergoing routine propofol induction procedures for elective surgery. In this prospective, observational clinical study, a total of 84 eligible patients were enrolled. The patients were categorized into yawning and no-yawning groups during propofol induction. During induction, both groups demonstrated significant reduction in high frequency coherence (coh-HF) with simultaneously significant increase in very low frequency coherence (coh-VLF) compared to the pre-induction period. As yawning occurred, the yawning group had more significant changes of cardio-respiratory coherences than the no-yawning group at coh-LF and coh-VLF bands. The yawning group also showed loss of linearity at high frequency band (coh-HF > 0.5) as compared with the pre-induction period, and also showed increases in linearity at low (coh-LF > 0.5) and very low (coh-VLF > 0.5) frequency bands compared with the no-yawning group. Propofol-induced yawning alters cardio-respiratory dynamics with changes of linearity between cardio-vascular and respiratory system behaviors."

Investigating Properties of the Cardiovascular System Using Innovative Analysis Algorithms Based on Ensemble Empirical Mode Decomposition

Cardiovascular system is known to be nonlinear and nonstationary. Traditional linear assessments algorithms of arterial stiffness and systemic resistance of cardiac system accompany the problem of nonstationary or inconvenience in practical applications. In this pilot study, two new assessment methods were developed: the first is ensemble empirical mode decomposition based reflection index (EEMD-RI) while the second is based on the phase shift between ECG and BP on cardiac oscillation. Both methods utilise the EEMD algorithm which is suitable for nonlinear and nonstationary systems. These methods were used to investigate the properties of arterial stiffness and systemic resistance for a pig's cardiovascular system via ECG and blood pressure (BP). This experiment simulated a sequence of continuous changes of blood pressure arising from steady condition to high blood pressure by clamping the artery and an inverse by relaxing the artery. As a hypothesis, the arterial stiffness and systemic resistance should vary with the blood pressure due to clamping and relaxing the artery. The results show statistically significant correlations between BP, EEMD-based RI, and the phase shift between ECG and BP on cardiac oscillation. The two assessments results demonstrate the merits of the EEMD for signal analysis.

Successful Pericardiocentesis for Cardiac Tamponade in a Patient with Thrombocytopenic Acute Lymphocytic Leukemia

We evaluated a 22-year-old patient complaining of acute breathlessness and pretibial edema in relapsed and refractory acute lymphoblastic leukemia (ALL). The patient was under rituximab-cyclophosphamide, vincristine, dexamethasone, doxorubicin (R-HCVAD) alternating with R-rituximab, methotrexate-cytarabine (MTX-ARAC) chemotherapies and he had a pancytopenia including severe thrombocytopenia. On his physical examination: The heart rate was 120 beats/min with evidence of pulsus paradoxus and the blood pressure was 85/60 mmHg. The jugular venous pressure was elevated up to the angle of the jaw. The cardiac apex was ill-defined and heart sounds were faint. There was no murmur or pericardial friction rub. He had severe pretibial edema because of hypoalbuminemia and acute right ventricular dysfunction observed by echocardiography. Electrocardiography revealed a poor R wave progression in all precordial derivations and sinus tachycardia. Laboratory data showed haemoglobin of 9.2 g/dL, white blood cell (WBC) count of 2.8x10 K/ uL with 93% blast cells, platelet count of 5x103/uL. International Normalized Ratio (INR) was 2.94 and activated Partial Thromboplastin Time (aPTT) was 56 sec. Chest radiogram showed moderate right sided pleural effusion with a normal cardiothoracic index. Bedside echocardiography revealed a large pericardial effusion with gross cardiac oscillation and diastolic collapse of the right ventricle and atrium (Figure 1). Mitral inflow pattern changed in expirium more than 25% of inspirium values and tricuspid inflow pattern changed in inspirium more than 40% of expirium values. Vena cava size was 2.3 cm and there was no change with respiration, particularly during inspirium. Echocardiographic and clinical findings indicated cardiac tamponade. Despite treatment with R-HCVAD regimen, the patient had no reponse to the treatment and his clinical condition was deteriorated. Because of the patient’s hemodynamic instability, we Abstract Cardiac tamponade (CT) as a clinical manifestation of lymphomas is extremely rare. Although leukaemic infiltration of the pericardium is frequently observed at post-mortem, clinically evident cardiac tamponade is also rare. We present a case of cardiac tamponade complicating leukaemia. The patient had cardiac tamponade and severe thrombocytopenia during chemotherapy due to relapsed and refractory acute lymphoblastic leukemia (ALL). We experienced complete resolution of the pericardial effusion without any bleeding complications after urgent pericardiocentesis within 15 days after successful ibubrufen-colchicine therapy. The exciting feature of this paper is that rescue pericardiosentesis may be livesaving despite crucial states, such as severe thrombocytopenia. (JAEM 2012; 11: 188-9)

Rhythmic Oscillations of Human Penile Bioimpedance in Healthy Individuals and in Patients with Vascular Erectile Dysfunction

Small variations of electric impedance (bioimpedance) of human penis were examined in healthy volunteers and in patients with vascular erectile dysfunction (ED). The harmonic analysis revealed rhythmic oscillations of penile bioimpedance at frequencies corresponding to the heart and respiration rates and Mayer wave (0.1 Hz) and to multiple frequencies (harmonics) of the respiratory and cardiac oscillations. In normal penile bioimpedance spectrum, the Mayer and respiratory peaks were several times higher than the first cardiac (pulsatile) harmonic indicating neurogenic origin of rhythmic bioimpedance variations in the whole penis. The most of healthy individuals (78%) demonstrated the cardiac harmonics at the frequency range of 4-7 Hz that violated the monotone decrement of the pulsatile harmonic series suggesting the resonant character of oscillations of the penile arteries at this "near" frequency range. In contrast to stable 1-4 cardiac harmonics, the amplitudes of the near-range resonant harmonics could vary during few minutes suggesting a causal relation of the corresponding bioimpedance oscillations with the varying vascular tone in penile arteries. The most patients (89%) with vascular ED demonstrated not only the first 1-4 monotonically decrementing harmonics and the near-resonant ones, but also the stable cardiac harmonics at the "far" frequency range of 8-14 Hz that also disturbed the monotonic character of the cardiac harmonic series indicating the sclerotic alterations in regional arteries. In ED patients, insignificant decrease of the initial cardiac harmonics C1-C3 in comparison with the norm was accompanied by pronounced and significant decrease of the respiratory R1 and Mayer M1 peaks. The study showed that the far-frequency bioimpedance resonances at the range of 8-14 Hz and dramatic drop of Mayer and respiratory peaks are the diagnostic signs of vascular ED independent on the accompanying hormonal or neurogenic disorders.

Effect of change in levels of motor activity and innervation on basic and secondary rhythms of rat heart beatings and respiration in ontogenesis

Changes in the heart basic rhythm, its rhythmical variations on periodograms, and level of spontaneos motor activity were studied on offspring of white rats from newborn to 3-week age at transition from the state of active wakefulness to narcosis as well as under conditions of blockade of M-cholinoreceptors with atropine. It is shown that the endogenous rhythmical activity can be regulated not only by a change in frequency of basic rhythms, but also by action on all parameters and properties of their rhythmical variations and secondary rhythms. The changes in power of the heart secondary rhythms exceed considerably the frequency oscillations of basic rhythms during blockade of cholinergic innervation or a change in the motor activity level that affects both the basic rhythm circulation and respiration and their variations--secondary rhythms. The atropine blockade of M-cholinoreceptors at the studied ages changes the heart beating rhythm within the limits of 10% of bradicardia in newborns to tachycardia in the 3-week old animals. At the same time, power of the cardiac rhythm secondary oscillations changes several times. These data indicate that the cholinergic mechanisms play the key role in formation of the secondary rhythms and their correlation with motor activity.

Exposure to smoking cues: Cardiovascular and autonomic effects

Laboratory exposures to smoking cues have been shown to reliably induce self-reported cigarette cravings among smokers, a model of environmentally triggered urges to smoke that can contribute to poorer cessation success. Several studies have also demonstrated that cue exposures give rise to changes in heart rate and blood pressure. Few studies, however, have investigated possible cue effects on heart rate and blood pressure variability (HRV and BPV). Particularly intriguing in this regard are cardiac oscillations in the low (i.e., 0.04–0.15 Hz), and high (i.e., 0.15–0.50 Hz) frequency range, which are thought to reflect components of autonomic control and response to environmental challenges. A closer examination of cardiovascular reactivity may thus help characterize the autonomic response to smoking cue exposure. To that end, an experimental study was conducted in which nicotine dependent daily smokers ( n = 98) were exposed to guided imagery of neutral and smoking situations, while continuous, noninvasive, beat-to-beat cardiovascular data were collected. Consistent with previous research, the findings revealed significant increases in both systolic and diastolic blood pressure during smoking imagery, relative to neutral imagery. In addition, power spectral density analyses of heart rate and blood pressure variability revealed elevated HRV and BPV in both the low- and high-frequency ranges during the smoking imagery. The results suggest the presence of an autonomic component to smoking cue reactivity, and also raise the possibility of long-term negative cardiac consequences for smokers who ubiquitously encounter cues in their daily environments.

Feasibility of NIRS in the Neurointensive Care Unit: A Pilot Study in Stroke Using Physiological Oscillations

Near-infrared spectroscopy (NIRS) is a non-invasive, real-time bedside modality sensitive to changes in cerebral perfusion and oxygenation and is highly sensitive to physiological oscillations at different frequencies. However, the clinical feasibility of NIRS remains limited, partly due to concerns regarding NIRS signal quantification, which relies on mostly arbitrary assumptions on hemoglobin concentrations and tissue layers. In this pilot study comparing stroke patients to healthy controls, we explored the utility of the interhemispheric correlation coefficient (IHCC) during physiological oscillations in detecting asymmetry in hemispheric microvascular hemodynamics. Using bi-hemispheric continuous-wave NIRS, 12 patients with hemispheric strokes and 9 controls were measured prospectively. NIRS signal was band-pass filtered to isolate cardiac (0.7-3 Hz) and respiratory (0.15-0.7 Hz) oscillations. IHCCs were calculated in both oscillation frequency bands. Using Fisher's Z-transform for non-Gaussian distributions, the IHCC during cardiac and respiratory oscillations were compared between both groups. Nine patients and nine controls had data of sufficient quality to be included in the analysis. The IHCCs during cardiac and respiratory oscillations were significantly different between patients versus controls (cardiac 0.79 +/- 0.18 vs. 0.94 +/- 0.07, P = 0.025; respiratory 0.24 +/- 0.28 vs. 0.59 +/- 0.3; P = 0.016). Computing the IHCC during physiological cardiac and respiratory oscillations may be a new NIRS analysis technique to quantify asymmetric microvascular hemodynamics in stroke patients in the neurocritical care unit. It allows each subject to serve as their own control obviating the need for arbitrary assumptions on absolute hemoglobin concentration. Future clinical applications may include rapid identification of patients with ischemic brain injury in the pre-hospital setting. This promising new analysis technique warrants further validation.

Autotriggering During Pressure Support Ventilation Due to Cardiogenic Oscillations

Newer generation anesthesia machines are equipped with a pressure support mode of ventilation, which can be used to support spontaneous ventilation in anesthetized patients. The Drager Apollo anesthesia machine uses an inspiratory limb hot-wire flow sensor to measure inspiratory flow rates. Detected flow rates that exceed the pressure support flow trigger will trigger pressure support breaths (Internal communication document. Drager Medical, 2007). In the case we are presenting, cardiac oscillations produced inspiratory flow rates that exceeded the flow trigger and autotriggered pressure support breaths. Autotriggering could be suppressed by increasing the trigger threshold or the positive end-expiratory pressure setting.

Investigating the Properties of Self-Organization and Synchronization in Electronic Systems

Nonlinear cooperative behavior appears naturally in many systems, such as cardiac cell oscillations; cellular calcium oscillations; oscillatory chemical reactions, and fireflies. Such systems have been studied in detail due to their inherent properties of robustness, adaptability, scalability, and emergence. In this paper, such nonlinear cooperative behaviors are considered within the domain of electronic system design. We investigate these desirable properties in a system composed of electronic oscillators. The paper presents a series of circuit simulation results showing that self-organizing principles, which can be emulated in an electronic circuit, enable the systems to show a phase transition to synchronization, in a manner similar to those of natural systems. Circuit simulation results presented here show that the circuits are robust to the unreliable performance of the electronic oscillators and tolerant to their run-time faults. These are important findings for future engineering applications in which the system's elements are likely to be unreliable and faulty, such as in molecular- and nanoelectronic systems.

The effects of airway closure in central apneas and obstructed respiratory efforts in mixed apneas in preterm infants

Airway closure during central apnea could allow for better gas exchange. However, the return of inspiratory efforts against a closed airway may cause greater desaturation and prolongation of apnea. To investigate the effect of patency of the airway and obstructed respiratory efforts on the length of apneas and the degree and slope of O(2) desaturation and bradycardia. All mixed apneas observed in 15 preterms were matched 1:2 with the longest central apneas in each infant. Central apneas were further classified using the amplified cardiac airflow oscillation in those with airway open and in those with airway closed. No differences were found in the length of apnea, slope of O(2) desaturation, delay between the onset of apnea and onset of desaturation, lowest post-apneic SpO(2), and time of recovery of SpO(2) between central apneas with and without airway closure. Although mixed apneas were significantly longer than central apneas, their initial central component was significantly shorter than the length of central apneas. In mixed apneas, the onset of O(2) desaturation occurred faster, SpO(2) decreased lower, and recovered slower compared with central apneas. The slope of O(2) desaturation after the obstructed respiratory efforts was significantly greater than before the obstructed respiratory efforts. In preterm infants: (1) airway closure during central apneas does not limit oxygen desaturation; (2) respiratory efforts against a closed airway prolong apnea and worsen the degree of desaturation and bradycardia. Although respiratory efforts are not necessary to induce airway closure, inspiratory efforts against a closed airway could trigger inhibitory cardio-respiratory responses causing significant desaturation, bradycardia, and prolongation of apnea.

The Monitoring of Vital Functions in Different Associations of General Injectable Anesthetics in Dogs

The discovery of new anesthetics, more effective and less toxic, gave veterinarians the possibility to successfully intervene in resolving the most different situations encountered in their activity. This study consisted in monitoring respiratory frequency, cardiac frequency and body temperature in patients anesthetized and then subdued to different surgical interventions. The researches were carried on 20 dogs of different breeds, ages and sexes, diagnosed with different types of diseases, which needed surgical treatment under the effect of anesthesia. There were selected patients in which pain intensity associated with surgical intervention was relatively equal. Anesthesia protocols consisted mainly in the association of two substances: xylazine + ketamine – in 5 cases; medetomidine + ketamine – in 5 cases; acepromazine + ketamine – in 5 cases; propofol – in 5 cases. In case of anesthesia induced by xylazine-ketamine combination, it was observed a slight tendency to bradycardia, respiratory frequency oscillations and the decrease of body temperature (tendency to hypothermia). Medetomidine-ketamine association determined cardiac frequency oscillations (without a particular tendency), an initial increase of respiratory frequency followed by come-back to normal and a slight decrease of body temperature. Using acepromazine-ketamine combination, the studied parameters varied under acceptable limits during anesthesia. Propofol ensured good conditions for surgical interventions, with the observations that the anesthetic effect is short and it requires supplementary safety measures in order to avoid the appearance of respiratory disorders. The selection of anesthetic substances must be done considering patient-related factors, the purpose of anesthesia and the available equipments.