Significant Changes In Cardiovascular Parameters Research Articles

Cardiovascular effects of dog appeasing pheromone in the hospital environment

Recent research has emphasized the health implications of acute or chronic stress in animals. Hospitalized dogs are susceptible to stress due to various factors, including exposure to a novel environment, invasive procedures, and separation from their primary caregiver. The clinical significance of stress in these animals underscores the importance of stress management from the moment of admission. However, there remains a lack of universal qualitative and quantitative indicators of stress in small animals, necessitating reliance on behavioral analysis and stress marker assessment for accurate diagnosis. Among these markers, cardiovascular parameters such as heart rate and systolic blood pressure are commonly used, although their interpretation can be influenced by various factors. The aim of the study was to assess the impact of appeasing pheromone on cardiovascular parameters in hospitalized dogs. Ten healthy dogs were selected for a prospective, paired, randomized, and double-blinded. The dogs were submitted to two experimental protocols: pheromone administration and placebo. The cardiovascular parameters were evaluated at baseline until the end of a 24-hour hospitalization period. The study evaluated ambulatory electrocardiography and systolic non-invasive blood pressure using a doppler. Analysis of cardiovascular parameters revealed no significant difference in systolic blood pressure between groups, despite its elevation in both treatment conditions. In the placebo group, the maximum heart rate of the placebo group at time baseline (T0) was lower compared to subsequent time points (T6, T12, T20), indicative of stress upon arrival in the hospital environment. Conversely, the pheromone group showed a higher mean heart rate at T20 compared to the placebo group. Additionally, the placebo group displayed a higher minimum heart rate at time baseline (T0) compared to later time points (T6, T12, T20, T24). At time T6, a higher minimum heart rate was observed in the pheromone group. Even though fluctuations were observed in mean and minimum heart rates during monitoring, they indicated no clinically relevant deviations. There was no difference in heart rate variability over time between the analyzed substances. Exposure to dog appeasing pheromone through a diffuser presentation, therefore, did not lead to significant changes in cardiovascular parameters related to stress reduction in hospitalized dogs.

Stimulant Medication Treatment in Children with Congenital Heart Disease and Attention-Deficit/Hyperactivity Disorder: Cardiovascular Outcomes.

Children with congenital heart disease (CHD) are at increased risk for attention-deficit/hyperactivity disorder (ADHD). The aim of this study was to determine whether children with CHD and ADHD clinically treated with stimulant medication were at increased risk for changes in cardiovascular parameters or death compared with CHD-matched controls. In this retrospective cohort study, patients with CHD + ADHD treated with stimulant medication (exposed group [EG]) were matched by CHD diagnosis and visit age to patients not on stimulants (nonexposed group [NEG]). Cardiovascular parameters (heart rate [HR] and systolic and diastolic blood pressure [SBP and DBP]) and electrocardiograms (ECGs) from medical records over 12 months were compared using mixed effects models. Cardiovascular parameters for 151 children with CHD (mean age 8 ± 4 years) were evaluated (N = 46 EG and N = 105 NEG). Stimulant medication use was not associated with sudden cardiac death. HR and SBP did not significantly change over time in the EG and remained similar between groups. EG children had higher DBP compared with NEG children over time ( p = 0.001). Group × time interactions for HR, SBP, and DBP were not different between the EG and NEG. QTc was not significantly different between the EG and NEG (447 ms vs 439 ms, p = 0.23). EG children demonstrated improvement in ADHD symptoms. Stimulant medication use in children with CHD was not associated with clinically significant changes in cardiovascular parameters compared with controls. Stimulants should be considered for ADHD treatment in children with CHD when prescribed with appropriate monitoring and coordination with the cardiologist.

Gravity Threshold and Dose Response Relationships: Health Benefits Using a Short Arm Human Centrifuge.

PurposeIncreasing the level of gravity passively on a centrifuge, should be equal to or even more beneficial not only to astronauts living in a microgravity environment but also to patients confined to bed. Gravity therapy (GT) may have beneficial effects on numerous conditions, such as immobility due to neuromuscular disorders, balance disorders, stroke, sports injuries. However, the appropriate configuration for administering the Gz load remains to be determined.MethodsTo address these issues, we studied graded G-loads from 0.5 to 2.0g in 24 young healthy, male and female participants, trained on a short arm human centrifuge (SAHC) combined with mild activity exercise within 40–59% MHR, provided by an onboard bicycle ergometer. Hemodynamic parameters, as cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were analyzed, as well as blood gas analysis. A one-way repeated measures ANOVA and pairwise comparisons were conducted with a level of significance p < 0.05.ResultsSignificant changes in heart rate variability (HRV) and its spectral components (Class, Fmax, and VHF) were found in all g loads when compared to standing (p < 0.001), except in 1.7 and 2.0g. There were significant changes in CO, cardiac index (CI), and cardiac power (CP) (p < 0.001), and in MAP (p = 0.003) at different artificial gravity (AG) levels. Dose-response curves were determined based on statistically significant changes in cardiovascular parameters, as well as in identifying the optimal G level for training, as well as the optimal G level for training. There were statistically significant gender differences in Cardiac Output/CO (p = 0.002) and Cardiac Power/CP (p = 0.016) during the AG training as compared to standing. More specifically, these cardiovascular parameters were significantly higher for male than female participants. Also, there was a statistically significant (p = 0.022) gender by experimental condition interaction, since the high-frequency parameter of the heart rate variability was attenuated during AG training as compared to standing but only for the female participants (p = 0.004).ConclusionThe comprehensive cardiovascular evaluation of the response to a range of graded AG loads, as compared to standing, in male and female subjects provides the dose-response framework that enables us to explore and validate the usefulness of the centrifuge as a medical device. It further allows its use in precisely selecting personalized gravity therapy (GT) as needed for treatment or rehabilitation of individuals confined to bed.

Effect of hemodialysis on impedance cardiography (electrical velocimetry) parameters in children.

Pediatric hemodialysis (HD) patients have a high incidence of cardiovascular morbidity and mortality. The study aim was to investigate whether impedance cardiography (electrical velocimetry, EV) is suitable as a hemodynamic trend monitoring tool in pediatric patients during HD. Measurements by EV were obtained before, during, and after HD in a prospective single-center pediatric observational study. In total, 54 dialysis cycles in four different pediatric patients with end-stage kidney disease on chronic HD were included. EV parameters analyzed were heart rate (HR), stroke volume (SV), stroke volume index (SI), cardiac output (CO), cardiac index (CI), thoracic fluid content (TFC), index of contractility (ICON), stroke volume variation (SVV), variation of ICON (VIC), R-R interval (TRR), pre-ejection period (PEP), left ventricular ejection time (LVET), and systolic time ration (STR). Systemic vascular resistance index (SVRI) was calculated. EV did measure significant changes in cardiovascular parameters associated with HD. The following parameters increased after HD: HR (9%), SVV (19%), VIC (33%), PEP (8%), and STR (18%). A decrease after HD was measured in SV (18%), SI (18%), CO (10%), CI (10%), TFC (10%), ICON (7%), TRR (7%), LVET (8%), and LVET (8%). SVRI was not affected by HD. The changes were correlated to ultrafiltration. HD cycles without fluid withdrawal also altered cardiovascular parameters. Pediatric HD with and without fluid withdrawal changes hemodynamic EV monitoring parameters. Possibly EV may be useful to optimize HD management in pediatric patients.

High salt intake during puberty leads to cardiac remodelling and baroreflex impairment in lean and obese male Wistar rats.

Modern lifestyle increases the prevalence of obesity and its co-morbidities in the young population. High-salt (HS) diets are associated with hypertension and cardiac remodelling. The present study evaluated the potential effects of cardiometabolic programming induced by HS intake during puberty in lean and obese rats. Additionally, we investigated whether HS could exacerbate the impairment of cardiovascular parameters in adult life due to postnatal early overnutrition (PO). At postnatal day 3 (PN3), twenty-four litters of Wistar rats were divided into two groups: normal litter (NL, nine pups/dam) and small litter (SL, three pups/dam) throughout the lactation period; weaning was at PN21. At PN30, the pups were subdivided into two more groups: NL plus HS (NLHS) and SL plus HS (SLHS). HS intake was from PN30 until PN60. Cardiovascular parameters were evaluated at PN120. SL rats became overweight at adulthood due to persistent hyperphagia; however, HS exposure during puberty reduced the weight gain and food intake of NLHS and SLHS. Both HS and obesity raised the blood pressure, impaired baro- and chemoreflex sensitivity and induced cardiac remodelling but no worsening was observed in the association of these factors, except a little reduction in the angiotensin type-2 receptor in the hearts from SLHS animals. Our results suggest that the response of newborn offspring to PO and juveniles to a HS diet leads to significant changes in cardiovascular parameters in adult rats. This damage may be accompanied by impairment of both angiotensin signalling and antioxidant defence in the heart.

Respiratory-Induced Hemodynamic Changes Measured by Whole-Body Multichannel Impedance Plethysmography

The cardiovascular system is described by parameters including blood flow, blood distribution, blood pressure, heart rate and pulse wave velocity. Dynamic changes and mutual interactions of these parameters are important for understanding the physiological mechanisms in the cardiovascular system. The main objective of this study is to introduce a new technique based on parallel continuous bioimpedance measurements on different parts of the body along with continuous blood pressure, ECG and heart sound measurement during deep and spontaneous breathing to describe interactions of cardiovascular parameters. Our analysis of 30 healthy young adults shows surprisingly strong deep-breathing linkage of blood distribution in the legs, arms, neck and thorax. We also show that pulse wave velocity is affected by deep breathing differently in the abdominal aorta and extremities. Spontaneous breathing does not induce significant changes in cardiovascular parameters.

Angiotensin 1–7 Action in the Lateral Preoptic Area is Involved in Urinary Bladder Regulation in Female Wistar Rats.

BackgroundChemical lesions of the lateral preoptic area (LPA) enhance water intake induced by subcutaneous injection of hypertonic saline in rats. On the other hand, the LPA section abolishes the increase in intravesical pressure (IP) induced by olfactory tubercle stimulation in dogs. Immunohistochemical labeling has demonstrated the presence of Mas receptors for Angiotensin‐(1–7) in LPA. It is not known whether neurons with Mas receptors in LPA are involved in urinary bladder regulation.AimWe investigated the effects of activation or blockade of Mas receptors for angiotensin‐(1–7) in LPA on intravesical pressure in anesthetized female rats.Materials and methodsFemale Wistar rats (~240 g, N=6) underwent to a stereotaxic surgery for implantation of stainless steel guide cannulas into the LPA under ketamine and xylazin anesthesia. After 7 days, the animals were anesthetized and maintained with 2% isoflurane in 100% O2 and submitted to cannulation of the femoral artery and vein, placement of a miniaturized Doppler flow probe around the left renal artery to measure the renal blood flow and cannulation of the urinary bladder for IP measurements. After baseline IP and cardiovascular parameters recordings for 15 min, angiotensin‐(1–7) (5 nmol/ uL) or saline (1 uL) or A‐779 (Mas receptor antagonist, 50 nmol/uL) was injected into the LPA and the variables were measured for additional 60 min.ResultsUnilateral injection of angiotensin‐(1–7) into LPA evoked a significant increase in IP (187.5±37.2%) compared to saline (−2.1±1.9%). Unilateral injection of A‐779 into LPA decreased the IP (−15.9±2.8%) in comparison to saline (2.0±1.1%). Interestingly, the decrease in IP was enhanced after bilateral injection of A‐779 into LPA (−27.3±3.4%) compared to the unilateral injection of this drug and also in comparison to saline (−2.9±1.6%) bilaterally into LPA. No significant changes in cardiovascular parameters after angiotensin‐(1–7) or saline or A‐779 in APL were observed.ConclusionThe data suggest that LPA is an important part of the circuit that regulates the urinary bladder activity mediated by angiotensin‐(1–7).Support or Funding InformationFinancial support: FAPESP and NEPAS‐FMABCThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of uphill, level, and downhill walking on cardiovascular parameters among young adults

BACKGROUND: Uphill walking and downhill walking are the different forms of walking which causes cardiovascular changes in the body. By changing the gradient of the treadmill, we can change the severity of exercise by keeping the speed constant. AIM: This study aims to evaluate the cardiovascular changes during uphill, level, and downhill walking in young adults. STUDY DESIGN: This was an experimental study MATERIALS AND METHODS: Twenty participants (15 males and 5 females) having normal body mass index were made to walk on the treadmill at different gradients of −15%, 0%, and +15% at a preferential speed for a constant duration of 15 min. The heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and rate pressure product (RPP) were recorded before and after walking. STATISTICAL ANALYSIS: Statistical analysis was done by ANOVA test using SPPSS, version 20 (IBM, Bangaluru, Karnataka ,India), where P RESULTS: There was a significant increase in HR (105.8 ± 20.06), SBP (133.3 ± 13.54), and RPP (14146 ± 3025) during uphill walking as compared to downhill and level walking. There were no significant changes in cardiovascular parameters when level walking and downhill walking were compared. DBP did not show any significant changes at any gradient of walking. CONCLUSION: Cardiovascular response increases during uphill walking, but level walking and downhill walking show no difference in cardiovascular response. These findings can be used to prescribe the exercises for young adults.

Renal responses produced by microinjection of the kappa opioid receptor agonist, U50-488H, into sites within the rat lamina terminalis.

Activation of central kappa opioid receptors (KOR) has been demonstrated to produce marked free water diuresis with a concurrent increase in renal sympathetic nerve activity (RSNA). This study investigated the cardiovascular (CV) and renal effects evoked by central activation of KOR in two lamina terminalis sites, the median preoptic area (MPA) and anterolateral division of the bed nuclei of the stria terminalis (BST). Rats anesthetized with urethane alpha-chloralose were instrumented to record mean arterial pressure, heart rate, RSNA, and urine output (V). Rats were infused with isotonic saline (25 μL/min) and urine samples were collected during two 10-min control periods and six consecutive 10-min experimental periods following microinjection of vehicle, U50-448H (U50, KOR agonist) alone or norbinaltorphimine (nor-BNI, KOR antagonist) plus U50. Microinjection of U50 into the BST increased V (peak at 30 min, 84.8 ± 12.9 μL/min) as compared to its respective control, vehicle, or nor-BNI plus U50. This diuretic effect occurred without any significant changes in CV parameters, RSNA, or urinary sodium excretion. In contrast, U50 injection into the MPA significantly increased RSNA (peak at 20 mins: 129 ± 9.9) without increasing the other parameters. This study demonstrated novel sites through which activation of KOR selectively increases V and RSNA. The ability of U50 to increase V without affecting sodium excretion and RSNA raises the possibility that LT neurons could be an important substrate through which drugs targeting KOR could selectively facilitate water excretion in sodium-retaining diseases such as congestive heart failure.

Comparison of the cardiopulmonary parameters after induction of anaesthesia with alphaxalone or etomidate in dogs

ObjectiveTo compare the cardiorespiratory effects and quality of induction of and recovery from anaesthesia following etomidate or alphaxalone-HPCD IV. Study designRandomized ‘blinded’ cross-over study. Twenty-four hours was allowed between phases. AnimalsEight healthy adult Beagles (four male, four female). MethodsDogs were anaesthetized with sevoflurane for instrumentation, then allowed to awake. They then received etomidate (treatment E) or alphaxalone-HPCD (treatment A) intravenously to effect. Heart rate (HR), body temperature, invasive arterial pressures (AP), systemic vascular resistance index (SVRI), stroke volume index, cardiac index (CI), contractility, respiratory rate, central venous pressure, and capnometry were obtained before anaesthetic induction (baseline), 30 seconds and 1 minute after induction, after intubation, one minute after intubation, and for every 5 minutes afterwards until the dog began to swallow and the trachea was extubated. Arterial bloods were taken for analyses before induction, after intubation and every 10 minutes thereafter. The dogs breathed room air. The quality of induction of and recovery from anaesthesia were scored categorically. Statistical analyses used anova for repeated measures, paired t-tests or Wilcoxon signed rank-test as relevant. Significance was set at p < 0.05. ResultsThe induction doses required were (mean ± SD) 2.91 ± 0.41 mg kg−1 and 4.15 ± 0.7 mg kg−1 for treatment E and A respectively. No significant changes in cardiovascular parameters were observed with treatment E. Treatment A resulted in statistically significant increases in HR and CI and reductions of APs and SVRI. Time to extubation was longer with treatment A (25 ± 7 minutes) than with treatment E (17 ± 4 minutes). Dogs became hypoxic with both treatments. The quality of induction and recovery were excellent with treatment A, but significantly less satisfactory with treatment E (recovery score, treatment E median 1, range 0–2; treatment A median 0, range 0–1). Conclusions and clinical relevanceAlphaxalone-HPCD caused significant tachycardia and increase in CI, and statistically (but not clinically) significant decreases in APs and SVRI. Etomidate caused no statistically significant cardiovascular changes. Quality of recovery was better with alfaxalone-HPCD. Both agents caused short-lived hypoxia, and oxygen supplementation is advisable.

No relevant cardiac, pharmacokinetic or safety interactions between roflumilast and inhaled formoterol in healthy subjects: an open-label, randomised, actively controlled study.

BackgroundRoflumilast is an oral, selective phosphodiesterase 4 inhibitor with anti-inflammatory effects in chronic obstructive pulmonary disease (COPD). The addition of roflumilast to long-acting bronchodilators improves lung function in patients with moderate-to-severe COPD. The present study investigated drug-drug interaction effects between inhaled formoterol and oral roflumilast.MethodsThis was a single-centre (investigational clinic), open, randomised, multiple-dose, parallel-group study. In Regimen A, healthy men were treated with roflumilast (500 μg tablet once daily; Day 2-18) and concomitant formoterol (24 μg twice daily; Day 12-18). In Regimen B, healthy men were treated with formoterol (24 μg twice daily; Day 2-18) and concomitant roflumilast (500 μg once daily; Day 9-18). Steady-state plasma pharmacokinetics of roflumilast, roflumilast N-oxide and/or formoterol (Cmax and AUC0-τ) as well as pharmacodynamics - blood pressure, transthoracic impedance cardiography (ZCG), 12-lead digital electrocardiography, peripheral blood eosinophils, and serum glucose and potassium concentrations - were evaluated through Day 1 (baseline), Day 8 (Regimen B: formoterol alone) or Day 11 (Regimen A: roflumilast alone), and Day 18 (Regimen A and B: roflumilast plus formoterol). Blood and urine samples were taken for safety assessment at screening, pharmacokinetic profiling days and Day 19. Adverse events were monitored throughout the study.ResultsOf the 27 subjects enrolled, 24 were evaluable (12 in each regimen). No relevant pharmacokinetic interactions occurred. Neither roflumilast nor formoterol were associated with significant changes in cardiovascular parameters as measured by ZCG, and these parameters were not affected during concomitant administration. Formoterol was associated with a slight increase in heart rate and a corresponding shortening of the QT interval, without changes in the heart rate-corrected QTc interval. There were small effects on the other pharmacodynamic assessments when roflumilast and formoterol were administered individually, but no interactions or safety concerns were seen after concomitant administration. No severe or serious adverse events were reported, and no adverse events led to premature study discontinuation.ConclusionsNo clinically relevant pharmacokinetic or pharmacodynamic interactions were found when oral roflumilast was administered concomitantly with inhaled formoterol, including no effect on cardiac repolarisation. Roflumilast was well tolerated.Trial RegistrationClinicaltrials.gov NCT00940329

Effects of Electroacupuncture on Minimum Alveolar Concentration of Isoflurane and Cardiovascular System in Isoflurane Anesthetized Dogs

The effects of electroacupuncture (EA) on the minimum alveolar concentration (MAC) and on the cardiovascular system were evaluated with dogs under isoflurane anesthesia. Eight healthy male beagles were randomly assigned to six study groups (five heads/group) with washout intervals of 7 ~ 31 days between experiments for recovery and anesthetic clearance. MAC of isoflurane and cardiovascular parameters were determined after EA at nonacupoint and and at acupoints LI-4, SP-6, ST-36 and TH-8. Electroacupuncture for 30 minutes at LI-4, SP-6, ST-36 and TH-8 acupoints lowered the MAC of isoflurane by 17.5 +/- 3.1%, 21.3 +/- 8.0%, 20.5 +/- 8.2% and 15.6 3.1%, respectively (p < 0.05). However, electrical stimulation of nonacupoint did not induce a significant change in MAC of isoflurane. In the cardiovascular system, the ST-36 group did not induce any significant change in cardiovascular parameters. In the TH-8 group, the mean and diastolic arterial pressure and the systemic vascular resistance were decreased. In the LI-4 group, cardiac output and cardiac index decreased after EA. These results indicate that EA at LI-4, SP-6 and ST-36 have advantages in isoflurane anesthesia in terms of reducing the dose of anesthetics and minimizing cardiovascular side effects.

The prone position in ARDS. A successful therapeutic strategy

As early as 1974, Brian advocated the prone position for ventilated patients. He suggested that this position might enhance ventilation of the dorsal parts of the lungs, thereby improving oxygenation. These considerations have been confirmed by several experimental and clinical studies. Better secretion removal, decreased intrapulmonary shunting, and an increased FRC are thought to be responsible for the observed improvement of oxygenation. However, the prone position never became very popular in the clinical treatment of the adult respiratory distress syndrome (ARDS). Routine performance of thoracic CT scans in ARDS patients demonstrated preferential distribution of pathological densities in the dependent lung areas. The prone position therefore could possibly benefit these patients, as shown by two recent studies. The aim of our study was to evaluate the influence of repeatedly turning the patient to the prone position on gas exchange and thoracic CT findings in multiple-trauma patients. METHODS. Seven ventilated intensive care patients with severe ARDS (Murray Score > 2.5, Quotient > 0.7, mean airway pressure > 18 cm H2O, thoracic CT scan showing dorsal atelectases) were included in the study. Patients were turned from the supine to the prone position at 12-h intervals using an air-cushion bed (Mediscus, Austria). Redistribution of dystelectatic or atelectatic dependent lung areas was verified by means of repeated thoracic CT scans (Figs. 1, 8). RESULTS. The patients were intermittently turned for 6.5 +/- 1.1 days. The course of gas exchange is shown in Figs. 2 and 3. Initially, improvement of the respiratory quotient could only be achieved during prone positioning, from the 2nd day in the supine position as well. Intrapulmonary shunting showed a similar trend (Figs. 4 and 5). No significant changes in cardiovascular parameters could be observed. Control thoracic CT scans showed uniform reduction of atelectases in dependent lung areas (Figs. 1 and 8). The inspiratory fraction of oxygen could be reduced significantly as of the 2nd day (Fig. 7). Constant levels of positive end-expiratory pressure and tidal volume were associated with decreasing mean and plateau airway pressures (Fig. 6). DISCUSSION. Repeatedly turning the patient to the prone position produced long-lasting improvement of arterial oxygenation, which persists up to the end of the weaning process. This is in good accordance with other studies, however, this is the first study to report an observation period of more than 6 days of repeatedly turning the patient. These positive effects on gas exchange can be attributed to sudden improvement of the ventilation-perfusion ratio within the lung areas that become dependent after turning to the prone position. Due to reduced hydrostatic pressure and relative hyperventilation, previously collapsed alveoli are recruited in the lung areas that become non-dependent after turning to the prone position.

The human pineal gland responds to stress-induced sympathetic activation in the second half of the dark phase: preliminary evidence.

Previous reports by our group and by others showed that the human pineal gland is unresponsive to stress-induced systemic sympathetic activation either during the day or 3 hrs after the beginning of darkness. In the present study, we investigated whether a longer period of dark exposure is required to demonstrate a stimulatory effect of stress-induced sympathetic activation on the human pineal gland. For this purpose, plasma melatonin levels were measured in six healthy men (aged 25-34 yrs) both in resting condition and before and after a physical exercise performed between 02.40 and 03.00 h, 30 min after exposure to bright light (2000 lux). Light exposure lasted from 02.10 h up to 04.00 h. The exercise consisted in bicycling on a bicycle ergometer at 50% of the personal maximum work capacity (MWC) for 10 min, followed by another 10 min of bicycling at 80% of the MWC. In the same subjects, plasma melatonin levels were measured also without exposure to light and with no exercise (control dark condition). The results showed that physical exercise, although inducing a rapid and short-term general sympathetic activation (as shown by significant changes in cardiovascular parameters) was able to increase light-depressed plasma melatonin levels only 5 hrs after the end of the stress (p < 0.0001, group X time interaction, two-way ANOVA with repeated measures). These findings suggest that the human pineal gland is responsive to systemic sympathetic activation induced by physical stress in the second half of the dark phase.

Nicardipine Decreases Blood Pressure and Heart Rate at Nucleus Tractus Solitarii of Spontaneously Hypertensive Rats

The effects of the dihydropyridine (DHP) calcium channel antagonist, nicardipine, on central cardiovascular regulation were investigated by injecting it into the cisterna magna or directly into the nucleus tractus solitarii (NTS), in anesthetized normotensive or spontaneously hypertensive (SHR) rats. Intracisternal injections of nicardipine (1-10 micrograms/kg) dose-dependently decreased blood pressure in SHR; there was no significant change in cardiovascular parameters in normotensive rats. In SHR, nicardipine (100 ng) microinjected bilaterally into the NTS produced hypotension and bradycardia. The same doses of nicardipine intravenously injected did not change either parameter. Previous administration of the beta-adrenoceptor blocking drug, tertatolol (50 micrograms/kg i.v.), prevented the nicardipine-induced bradycardia and hypotension after injection into the NTS. These data suggest that part of the central cardiovascular effects of nicardipine result from an interaction with DHP sites within the NTS leading to a withdrawal of the sympathetic tone.

Cardiovascular effects of high-dose fentanyl anaesthesia.

An anaesthetic technique using high-dose fentanyl for coronary artery surgery is described. Fentanyl 60 or 70 micrograms kg-1 was used as the sole anaesthetic agent, and patients were ventilated with air/O2 (fentanyl 70 micrograms kg-1) or N2O/O2 (fentanyl 60 micrograms kg-1). Cardiovascular data from 30 patients are presented. Fentanyl caused no significant cardiovascular depression. The only statistically significant changes in cardiovascular parameters were seen in the patients who received fentanyl 60 micrograms kg-1. Five minutes after skin incision there was an increase in peripheral resistance. Diastolic pressure was increased following sternotomy. Problems associated with this technique of anaesthesia are a 50% incidence of hypertension following sternotomy (requiring treatment with sodium nitroprusside) and prolonged respiratory depression. The lack of cardiovascular depression produced by fentanyl and the ability of fentanyl to reduce hormonal and metabolic responses to surgery make it a satisfactory technique for cardiac anaesthesia.