Phenylephrine Infusion Research Articles

Involvement of CRF1 receptors in bed nucleus of stria terminalis (BNST) on baroreflex responses in chronically stressed rats

INTRODUCTIONStudies suggest the involvement of CRF receptors in bed nucleus of the stria terminalis (BNST) on cardiovascular responses in acute stress. Data from our group had demonstrated that the expression of CRF1 receptors within the BNST is decreased in animals exposed to chronic variable stress (CVS). Nevertheless, an involvement of BNST CRF neurotransmission on cardiovascular changes evoked by CVS has never been investigated.AIMTo evaluate the involvement of CRF1 receptor in the BNST on baroreflex changes evoked by CVS in rats.METHODOLOGYMale Wistar rats (250g) were submitted to stereotaxic surgery for implantation of cannulas into the BNST. After 4 days of recovery, the animals were exposed to a CVS protocol for 10 days. After the last session, the rats had the femoral artery and vein cannulated for cardiovascular record and drug infusion, respectively. Twenty‐four hours later, the experiments were performed. Baroreflex function was assessed by evoking changes on arterial pressure throughout intravenous infusions of phenylephrine and sodium nitroprusside, which evoke pressor and depressor effects, respectively. Baroreflex activity was evaluated in both control rats and animals subjected to ECV protocol before and after bilateral microinjection of the selective CRF1 antagonist CP376395 (5nmol/100nL) into the BNST.RESULTSComparison of values before BNST treatment revealed that ECV decreased the bradycardiac response evoked by blood pressure increase (−48±10 vs −114±23 bpm, P<0.03). Moreover, bilateral microinjection of CP376395 into the BNST decreased reflex bradycardia in control group (−51±13 vs −114±23 bpm, P<0.02), but not in animals subjected to ECV (−51±10 vs −48±10 bpm, P>0.05). The tachycardia evoked by blood pressure decrease was also decreased following ECV (57±5 vs 97±11 bpm, P<0.05). The BNST treatment with CP376395 decreased the tachycardiac response in control animals (50±9 vs 97±11 bpm, P<0.001), but without affecting this response in CVS rats (52±5 vs 57±5 bpm, P>0.05).CONCLUSIONThe impairment of baroreflex function evoked by CVS is related to decreased control of this reflex cardiovascular by CRF1 receptor in the BNST.Support or Funding InformationFINANCIAL SUPPORT: FAPESPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

TNFα Impairs Cerebral Blood Flow Autoregulation in Pregnant Rats

Neurological symptoms are often reported among preeclamptic patients and cerebrovascular events account for ~40% of all preeclamptic/eclamptic‐related deaths. While cerebral blood flow (CBF) autoregulation is impaired in preeclamptic (PE) women as well as in placental ischemic rats which develop a PE‐like syndrome, the underlying mechanisms responsible for abnormal CBF autoregulation are unclear. Placental ischemic rats have higher levels of circulating cytokines, and we previously reported that tumor necrosis factor – alpha (TNFα), at levels that mimic TNFα in human preeclampsia, increases blood brain barrier (BBB) permeability and cerebral edema in pregnant rats. Therefore, we tested the hypothesis that TNFα alters CBF autoregulation in pregnant rats. To test this hypothesis, normal pregnant Sprague Dawley rats were infused with TNFα (200ng/day) and cerebral blood flow was measured by laser Doppler flowmetry under anesthesia. Rats were intubated and ventilated in order to maintain constant blood gasses and mean arterial pressure was elevated step‐wise from 100–190 mmHg by infusion of phenylephrine to determine changes in CBF. TNFα was found to impair CBF autoregulation in pregnant rats where CBF was significantly increased in TNFα‐infused rats at 180 mmHg (225±13 vs 173±8) and 190 mmHg (253±17 vs 188±9) compared to normal pregnant rats with no significant difference in peak CO2 between the two groups at 180 mmHg (44.9±0.8 vs 45.4±0.9 mmHg) or 190 mmHg (43±0.8 vs 45.3±0.9). Autoregulatory index (percent change in blood flow divided by percent change in perfusion pressure) was also significantly increased in TNFα‐infused rats at 180 mmHg (1.56±0.17 vs 0.91±0.11) and 190 mmHg (1.7±0.07 vs 0.99±0.11) compared to normal pregnant rats. These data suggest that circulating TNFα from the ischemic placenta could contribute to cerebrovascular complications during pregnancy and postpartum. TNFα could serve as a novel pharmacological target to ameliorate CBF autoregulation in preeclampsia.Support or Funding InformationThis study was supported by National Institutes of Health Grants, HLHL51971, HL136684‐A0, and an NRSA Institutional Training Grant, T32HL105324.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Randomized Double-blind Trial of Phenylephrine and Metaraminol Infusions for Prevention of Hypotension During Spinal and Combined Spinal-Epidural Anesthesia for Elective Cesarean Section

(Anaesthesia. 2017;72(5):609–617) Currently phenylephrine, preferably as an infusion, is the drug of choice for the prevention and management of spinal anesthesia-induced hypotension during elective cesarean delivery. However, high doses of phenylephrine may result in maternal bradycardia, which can lead to decreased cardiac output and uteroplacental perfusion. While metaraminol is a vasopressor that has been used widely to maintain blood pressure and heart rate in nonobstetric patients, investigations in obstetrics, especially in comparison to phenylephrine have been limited. The current investigators decided to investigate metaraminol as an alternative to phenylephrine for the prevention of maternal hypotension during the administration of spinal or combined spinal-epidural anesthesia for elective cesarean sections (CS). They hypothesized that metaraminol would be at least noninferior to phenylephrine in terms of neonatal acid-base status.

Pharmacological assessment of the contribution of the arterial baroreflex to sympathetic discharge patterns in healthy humans

To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure with intravenous nitroprusside (NTP) and phenylephrine (PE) and measured action potential (AP) patterns with wavelet-based methodology. We hypothesized that 1) baroreflex unloading (NTP) would increase firing of low-threshold axons and recruitment of latent axons and 2) baroreflex loading (PE) would decrease firing of low-threshold axons. Heart rate (HR, ECG), arterial blood pressure (BP, brachial catheter), and muscle sympathetic nerve activity (MSNA, microneurography of peroneal nerve) were measured at baseline and during steady-state systemic, intravenous NTP (0.5-1.2 µg·kg-1·min-1, n = 13) or PE (0.2-1.0 µg·kg-1·min-1, n = 9) infusion. BP decreased and HR and integrated MSNA increased with NTP ( P < 0.01). AP incidence (326 ± 66 to 579 ± 129 APs/100 heartbeats) and AP content per integrated burst (8 ± 1 to 11 ± 2 APs/burst) increased with NTP ( P < 0.05). The firing probability of low-threshold axons increased with NTP, and recruitment of high-threshold axons was observed (22 ± 3 to 24 ± 3 max cluster number, 9 ± 1 to 11 ± 1 clusters/burst; P < 0.05). BP increased and HR and integrated MSNA decreased with PE ( P < 0.05). PE decreased AP incidence (406 ± 128 to 166 ± 42 APs/100 heartbeats) and resulted in fewer unique clusters (15 ± 2 to 9 ± 1 max cluster number, P < 0.05); components of an integrated burst (APs or clusters per burst) were not altered ( P > 0.05). These data support a hierarchical pattern of sympathetic neural activation during manipulation of baroreceptor afferent activity, with rate coding of active neurons playing the predominant role and recruitment/derecruitment of higher-threshold units occurring with steady-state hypotensive stress. NEW & NOTEWORTHY To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure with intravenous nitroprusside and phenylephrine and measured sympathetic outflow with wavelet-based methodology. Baroreflex unloading increased sympathetic activity by increasing firing probability of low-threshold axons (rate coding) and recruiting new populations of high-threshold axons. Baroreflex loading decreased sympathetic activity by decreasing the firing probability of larger axons (derecruitment); however, the components of an integrated burst were unaffected.

Low-Dose Epinephrine Infusions and Tranexamic Acid During Lower-Extremity Total Joint Arthroplasty: Commentary on an article by Wei-Nan Zeng, MD, et al.: "Low-Dose Epinephrine Plus Tranexamic Acid Reduces Early Postoperative Blood Loss and Inflammatory Response. A Randomized Controlled Trial".

Low-Dose Epinephrine Infusions and Tranexamic Acid During Lower-Extremity Total Joint Arthroplasty: Commentary on an article by Wei-Nan Zeng, MD, et al.: "Low-Dose Epinephrine Plus Tranexamic Acid Reduces Early Postoperative Blood Loss and Inflammatory Response. A Randomized Controlled Trial".

Neuroreflex control of cardiovascular function is impaired after acute poisoning with chlorpyrifos, an organophosphorus insecticide: Possible short and long term clinical implications

Although it is well-established that severe poisoning by organophosphorus (OP) compounds strongly affects the cardiorespiratory system, the effects of sub-lethal exposure to these compounds on the neural control of cardiovascular function are poorly explored. The aim of this study was to evaluate the effects of acute sub-lethal exposure to chlorpyrifos (CPF), a commonly used OP insecticide, on three basic reflex mechanisms involved in blood pressure regulation, the peripheral chemoreflex, the baroreflex and the Bezold-Jarisch reflex. Adult male Wistar rats were injected intraperitoneally with a single dose of CPF (30 mg/kg) or saline (0.9%). 24 h after injections, cardiovascular reflexes were tested in awake rats. Potassium cyanide (KCN) and phenylbiguanide (PBG) were injected intravenously to activate the chemoreflex and the Bezold-Jarisch reflex, respectively. The baroreflex was activated by phenylephrine and sodium nitroprusside infusions. Blood samples were taken for measurements of butyrylcholinesterase (BChE) activity while acetylcholinesterase (AChE) activity was measured in brainstem samples. Animals treated with CPF presented signs of intoxication such as ataxia, tremor, lacrimation, salivation, tetany, urination and defecation. The hypertensive and the bradycardic responses of the chemoreflex as well as the hypotensive and bradycardic responses of the Bezold-Jarisch reflex were attenuated in CPF treated animals (P < 0.05). Concerning the baroreflex responses, CPF treatment reduced the bradycardia plateau, the range and the gain of the reflex (P < 0.05). Plasma BChE and brainstem AChE were both reduced significantly after CPF treatment (P < 0.05). Our results showed that acute sub-lethal exposure to CPF impairs the cardiovascular responses of homeostatic and defensive cardiovascular reflexes. These effects are associated with a marked inhibition of plasma BChE and brainstem AChE.

The influence of norepinephrine and phenylephrine on cerebral perfusion and oxygenation during propofol\u2013remifentanil and propofol\u2013remifentanil\u2013dexmedetomidine anaesthesia in piglets

BackgroundVasopressors are frequently used to increase blood pressure in order to ensure sufficient cerebral perfusion and oxygenation (CPO) during hypotensive periods in anaesthetized patients. Efficacy depends both on the vasopressor and anaesthetic protocol used. Propofol–remifentanil total intravenous anaesthesia (TIVA) is common in human anaesthesia, and dexmedetomidine is increasingly used as adjuvant to facilitate better haemodynamic stability and analgesia. Little is known of its interaction with vasopressors and subsequent effects on CPO. This study investigates the CPO response to infusions of norepinephrine and phenylephrine in piglets during propofol–remifentanil and propofol–remifentanil–dexmedetomidine anaesthesia. Sixteen healthy female piglets (25–34 kg) were randomly allocated into a two-arm parallel group design with either normal blood pressure (NBP) or induced low blood pressure (LBP). Anaesthesia was induced with propofol without premedication and maintained with propofol–remifentanil TIVA, and finally supplemented with continuous infusion of dexmedetomidine. Norepinephrine and phenylephrine were infused in consecutive intervention periods before and after addition of dexmedetomidine. Cerebral perfusion measured by laser speckle contrast imaging was related to cerebral oxygenation as measured by an intracerebral Licox probe (partial pressure of oxygen) and transcranial near infrared spectroscopy technology (NIRS) (cerebral oxygen saturation).ResultsDuring propofol–remifentanil anaesthesia, increases in blood pressure by norepinephrine and phenylephrine did not change cerebral perfusion significantly, but cerebral partial pressure of oxygen (Licox) increased following vasopressors in both groups and increases following norepinephrine were significant (NBP: P = 0.04, LBP: P = 0.02). In contrast, cerebral oxygen saturation (NIRS) fell significantly in NBP following phenylephrine (P = 0.003), and following both norepinephrine (P = 0.02) and phenylephrine (P = 0.002) in LBP. Blood pressure increase by both norepinephrine and phenylephrine during propofol–remifentanil–dexmedetomidine anaesthesia was not followed by significant changes in cerebral perfusion. Licox measures increased significantly following both vasopressors in both groups, whereas the decreases in NIRS measures were only significant in the NBP group.ConclusionsCerebral partial pressure of oxygen measured by Licox increased significantly in concert with the vasopressor induced increases in blood pressure in healthy piglets with both normal and low blood pressure. Cerebral oxygenation assessed by intracerebral Licox and transcranial NIRS showed opposing results to vasopressor infusions.

Comparison of Infusion and Bolus Injections of Phenylephrine on Hemodynamic Stability during Cardiopulmonary Bypass and their Effects on Bicarbonate and Lactate Blood Level

Comparison of Infusion and Bolus Injections of Phenylephrine on Hemodynamic Stability during Cardiopulmonary Bypass and their Effects on Bicarbonate and Lactate Blood Level

Haemodynamic stability during anaesthesia induction with propofol – impact of phenylephrine. A double-blind, randomised clinical trial

Background. We studied the effects of a parallel phenylephrine infusion during bispectral index guided anaesthesia in-duction with propofol on haemodynamic parameters. We hypothesised that mean ar-terial pressure and cardiac index would be better maintained in the group of patients receiving the phenylephrine infusion dur-ing induction.Methods. We studied ASA I-III patients scheduled for oncological abdominal sur-gery. Forty patients randomly received ei-ther a 0.9% NaCl or a phenylephrine (0.5 μg/kg/min) infusion during the induction of anaesthesia with propofol to a bispectral index value of 60. Mean arterial pressure, stroke volume index and systemic vascular resistance index were recorded, starting at one minute before induction for 20 min-utes, at one-minute intervals.Results. After induction of anaesthesia before intubation mean arterial pressure and stroke volume index decreased sig-nificantly compared to baseline in both groups, while the systemic vascular resist-ance index increased slightly. At the end of measurements, mean arterial pressure (66 ± 11 vs. 94 ± 14 mmHg; 0.9% NaCl vs. phenylephrine group p<0.01) and stroke volume index (34.2 ± 9.1 vs. 44.0 ± 9.7 ml/m2; 0.9% NaCl vs. phenylephrine group p<0.01) were lower in both groups in com-parison to baseline values, but were better maintained in the phenylephrine group, whereas systemic vascular resistance index was higher than at baseline (2308 ± 656 vs. 3198 ± 825 dynes s/cm5/m2; 0.9% NaCl vs. phenylephrine group p<0.01) with signifi-cant differences between groups. Conclusion. Our study shows that a con-tinuous phenylephrine infusion can atten-uate the drop in mean arterial pressure and stroke volume index during anaesthesia induction with propofol.

The Effect of Prophylactic Infusion of Combined Ephedrin and Phenylephrine on Maternal Hemodynamic after Spinal Anesthesia for Cesarean Section: A Randomized Clinical Trial.

IRCT201401277013N6.

Study Comparing Phenylephrine Bolus and Infusion for Maternal Hypotension and Neonatal Outcome during Cesarean Section under Spinal Anesthesia.

Background:Phenylephrine(PE) bolus and infusion have been compared for post spinal hypotension and neonatal effects during cesarean section(CS) under spinal anesthesia(SA).Aim:The primary aim of this study was to compare bolus doses of 50μg of PE with a fixed infusion rate of 50 μg/min of the same drug given prophylactically. The secondary aim was to study the neonatal outcome and side effects with the two regimes.Settings and Design:This prospective,randomized,comparative study was conducted in the department of Anesthesia in a tertiary care teaching hospital.Materials and Methods:This study was conducted on 100 normotensive women undergoing CS under SA. The patients were randomized into two groups of 50 each. Group A received bolus of 50 μg PE after the systolic BP(SBP) fell by 20% from the baseline and Group B received a prophylactic infusion of 50 μg/min PE. The changes in heart rate (HR), BP and side effects were compared till delivery. The neonatal APGAR scores were compared at 1 and 5 minutes and an umbilical artery sample was sent for blood gas analysis.Statistical Analysis:Categorical variables were shown in number and percentage. Normally distributed continuous variables were presented as mean ± SD and compared using unpaired t-test. Non normally distributed continuous variables were displayed as median and were compared using Mann-Whitney test. A P value of <0.05 was considered significant.Results:In group A, the HR was higher than in group B throughout the monitoring period. (P < 0.001). In group A, SBP trend showed a fall of more than 20% from the base line in 44 patients. The mean fall in SBP was -28.06 ± 5.3 mmHg% in Group A while in group B the mean fall in SBP was only -0.44 ± 4.3mmHg%. Nausea and vomiting was less in group B. There was no difference in APGAR or neonatal acidosis on ABG.Conclusion:There was a tighter control of BP in the infusion group vs. the bolus group while the neonatal outcome was similar in both the groups.

Liver transplantation for acute liver failure due to hepatitis E in a pregnant patient.

Liver transplantation for acute liver failure due to hepatitis E in a pregnant patient.

A comparative study of phenylephrine and ephedrine combination to ephedrine and phenylephrine alone for maintenance of blood pressure for caesarean delivery and their effects on foetal acid base status

Introduction: Spinal anaesthesia is the preferred technique for caesarean section. Around 80% of which is complicated by maternal hypotension. Vasopressors are currently the treatment of choice for spinal-induced hypotension but these may individually have significant maternal or foetal side effects. Aim: To compare ephedrine and phenylephrine infusion with ephedrine and phenylephrine combination for preventing the hypotension in patients undergoing emergency caesarean section under spinal anaesthesia. Materials and Methods: A prospective randomized double blind study of 90 parturients beyond 32 weeks of pregnancy for caesarean section under spinal anaesthesia. Assuming a potency ratio of 80:1 ephedrine to phenylephrine, the patients were divided into the following three groups: Group E - received infusions of ephedrine 8 mg/ml, Group P - received infusions of 100 mcg/ml phenylephrine and Group E + P received infusion of ephedrine 4 mg/ml + phenylephrine 50 mcg/ml. A predefined algorithm was used to adjust the infusion rate according to the systolic blood pressure (SBP). After spinal injection, SBP, diastolic blood pressures (DBP), heart rate (HR) were recorded every one minute until the cord was clamped. Also, the vasopressor infusion rates were collected till clamping of umbilical cord in each group. Foetal parameters were analyzed from umbilical blood gas. Results: The incidence of hypotension was significantly higher in ephedrine group. The mean rate of infusion was higher for group E (P 0.05) as compared to others. Complications of bradycardia were observed in 30% of patients receiving phenylephrine. Conclusions: Combination of both phenylephrine and ephedrine is efficacious for spinal-induced hypotension with least maternal or foetal side effects.

Effect of prophylactic ondansetron and/or continuous infusion of phenylephrine on spinal anesthesia-induced hypotension

Effect of prophylactic ondansetron and/or continuous infusion of phenylephrine on spinal anesthesia-induced hypotension

The Role of Angiotensin II Infusion on the Baroreflex Sensitivity and Renal Function in Intact and Bilateral Renal Denervation Rats.

Background:The role of renin-angiotensin system (RAS) in communication between renal system and cardiovascular system is extremely important. Baroreflex sensitivity (BRS) index defines as heart rate (HR) alteration versus mean arterial pressure (MAP) change ratio . Sympathetic nerve is arm of the baroreflexes and any change in its activity will lead to change in the BRS. The role of angiotensin II (Ang II) infusion in systemic circulation accompanied with bilateral renal denervation (RDN) on BRS index and renal function was studied.Materials and Methods:Seventy-two male and female Wistar rats in 12 groups were anesthetized and catheterized. The alteration of MAP and HR responses to phenylephrine infusion compared to control groups was determined in bilateral RDN rats subjected to treat with Ang II (300 or 1000 ng/kg/min) administration.Results:The BRS index was elevated in Ang II-treated non-RDN (normal) male rats gradually and dose dependently (P < 0.05), while this index was significantly different when compared with RDN male rats (P < 0.05). Accordingly, the BRS index was significantly lower in RDN than non-RDN male rats, and such observation was not observed in female rats. The creatinine clearance (insignificantly) and urine flow (significantly; P < 0.05) were decreased in both non-RDN and RDN male and female rats treated with Ang II. In RDN model, the serum nitrite levels were decreased in male and increased in female by Ang II infusion when compared with vehicle infusion.Conclusion:The Ang II infusion could increase the BRS index in non-RDN (normal) male rats which is significantly greater than BRS index in RDN rats.

Isoflurane's Effect on Intraoperative Systolic Left Ventricular Performance in Cardiac Valve Surgery Patients

BackgroundIsoflurane, a common anesthetic for cardiac surgery, reduced myocardial contractility in many experimental studies, few studies have determined isoflurane's direct impact on the left ventricular (LV) contractile function during cardiac surgery. We determined whether isoflurane dose-dependently reduces the peak systolic velocity of the lateral mitral annulus in tissue Doppler imaging (S′) in patients undergoing cardiac surgery.MethodsDuring isoflurane-supplemented remifentanil-based anesthesia for patients undergoing cardiac surgery with preoperative LV ejection fraction greater than 50% (n = 20), we analyzed the changes of S′ at each isoflurane dose increment (1.0, 1.5, and 2.0 minimum alveolar concentration [MAC]: T1, T2, and T3, respectively) with a fixed remifentanil dosage (1.0 μg/min/kg) by using transesophageal echocardiography.ResultsMean S′ values (95% confidence interval [CI]) at T1, T2, and T3 were 10.5 (8.8–12.2), 9.5 (8.3–10.8), and 8.4 (7.3–9.5) cm/s, respectively (P < 0.001 in multivariate analysis of variance test). Their mean differences at T1 vs. T2, T2 vs. T3, and T1 vs. T3 were −1.0 (−1.6, −0.3), −1.1 (−1.7, −0.6), and −2.1 (−3.1, −1.1) cm/s, respectively. Phenylephrine infusion rates were significantly increased (0.26, 0.22, and 0.47 μg/kg/min at T1, T2, and T3, respectively, P < 0.001).ConclusionIsoflurane increments (1.0–2.0 MAC) dose-dependently reduced LV systolic long-axis performance during cardiac surgeries with a preserved preoperative systolic function.

Aortocaval Compression Syndrome: Time to Revisit Certain Dogmas

More than 70 years ago, the phenomenon of "postural shock" in the supine position was described in healthy women in late pregnancy. Since then, avoidance of the supine position has become a key component of clinical practice. Indeed, performing pelvic tilt in mothers at term to avoid aortocaval compression is a universally adopted measure, particularly during cesarean delivery. The studies on which this practice is based are largely nonrandomized, utilized a mix of anesthetic techniques, and were conducted decades ago in the setting of avoidance of vasopressors. Recent evidence is beginning to refine our understanding of the physiologic consequences of aortocaval compression in the context of contemporary clinical practice. For example, magnetic resonance imaging of women at term in the supine and tilted positions has challenged the dogma that 15° of left tilt is sufficient to relieve inferior vena cava compression. A clinical investigation of healthy term women undergoing elective cesarean delivery with spinal anesthesia found no difference in neonatal acid-base status between women randomized to be either tilted to the left by 15° or to be in the supine position, if maternal systolic blood pressure is maintained at baseline with a crystalloid coload and prophylactic phenylephrine infusion. This review presents a fresh look at the decades of evidence surrounding this topic and proposes a reevaluation and appraisal of current guidelines regarding entrenched practices.

ED50 of intrathecal ropivacaine for cesarean section under prophylactic infusion of phenylephrine: A consort study.

Background:Studies have reported that prophylactic continuous infusion of phenylephrine during spinal anesthesia for cesarean section can decrease the spread of local anesthetics. We investigated the ED50 of intrathecal hyperbaric ropivacaine in parturient women undergoing cesarean section under prophylactic infusion of phenylephrine.Methods:Sixty parturient women were allocated into 2 groups in this prospective study. Group P received 0.5 mL kg−1 h−1 of phenylephrine (5 mg/50 mL) at the start of intrathecal injection, and Group C (control group) received the same volume of saline. The dose of intrathecal ropivacaine for each subject was decided through up-down allocation method. The initial dose was set as 7.5 mg. Successful anesthesia was defined as the level of T6 or above achieved within 15 minutes after intrathecal injection and no additional epidural drug or venous analgesia to complete operation. The Massey formula was applied to calculate the ED50 of intrathecal ropivacaine in both groups.Results:The ED50 of hyperbaric ropivacaine determined by up-and-down method was 7.2 mg (95% confidence interval (CI), 6.8–7.6 mg) in the Group P, and 6.8 mg (95% CI, 6.4–7.2 mg) in the Group C, there was significant difference between the 2 groups (P < .5). The ED50 of intrathecal ropivacaine increases compared with Group C when phenylephrine is prophylactic infused to prevent spinal induced hypotension in cesarean section.Conclusion:The ED50 of intrathecal hyperbaric ropivacaine is 7.2 mg when phenylephrine is prophylactic infused to prevent spinal induced hypotension in cesarean section, and more ropivacaine demands on spinal anesthesia for cesarean section (www.chictr.org.cn, registration number: ChiCTR-RIC-17011650).

Effect of ephedrine and phenylephrine on brain oxygenation and microcirculation in anaesthetised patients with cerebral tumours: study protocol for a randomised controlled trial

IntroductionDuring brain tumour surgery, vasopressor drugs are commonly administered to increase mean arterial blood pressure with the aim of maintaining sufficient cerebral perfusion pressure. Studies of the commonly used vasopressors...

Influence of catecholamines at different dosages on the function of the LiDCO sensor in isoflurane anesthetized horses

To compare the lithium dilution method for cardiac output (LiDCO) and bolus-thermo-dilution (BTD) measurements before and during infusion of dobutamine, dopamine, phenylephrine, or noradrenaline at 2 different doses in anesthetized horses and to examine the correlation between sensor voltages (saline-blood exposed) and possible measurement errors. Prospective experimental study. University teaching hospital. Nine Warmblood horses. Following 90 minutes of equilibration, 3 different doses of dobutamine (0.5-3 μg/kg/min), dopamine (1-5 μg/kg/min), phenylephrine (0.5-3 μg/kg/min), or noradrenaline (0.1-0.5 μg/kg/min) were administered for 15 minutes in anesthetized horses, and measurements using the LiDCO were performed at the lowest and highest doses. Pairs of LiDCO and BTD measurements were collected and sensor voltages exposed to blood and saline were measured before and at the end of each infusion period. Agreement between LiDCO and BTD was assessed with the Bland-Altman method. The biases (2 standard deviations) before infusion of dobutamine, dopamine, phenylephrine, and noradrenaline were 1.1 (5.7), 1.6 (7.3), 0.2 (6.6), and 1.5 (4.1) L/min, respectively, and minimally and nonsignificantly changed following low-dose catecholamine infusions. Following infusion of higher doses, biases were significantly higher compared to baseline with 10.7 (7.8), 11.2 (11.9), 6.9 (11.7), and 3.5 (3.8) L/min, respectively. The difference between saline- and blood-exposed sensor voltage decreased during infusion of high doses of catecholamines with correlations (rs = 0.62) between cardiac output differences and sensor voltage differences (saline-blood). This study demonstrated that catecholamines could lead to overestimation in a dose-dependent fashion in LiDCO measurements. Monitoring changes in sensor voltage differences (saline-blood) is a valuable and clinically applicable tool to predict errors in LiDCO measurements.