Oral clonidine preanesthetic medication augments the pressor responses to intravenous ephedrine in awake or anesthetized patients

Hemodynamic impact of ephedrine on hypotension during general anesthesia: a prospective cohort study on middle-aged and older patients

BACKGROUND

Ephedrine is a mixed α- and β-agonist vasopressor that is frequently used for the correction of hypotension during general anesthesia. β-responsiveness has been shown to decrease with age; therefore, this study aimed to determine whether aging would reduce the pressor effect of ephedrine on hypotension during general anesthesia.

METHODS

Seventy-five patients aged ≥ 45 years were included in this study, with 25 patients allocated to each of the three age groups: 45-64 years, 65-74 years, and ≥ 75 years. All patients received propofol, remifentanil, and rocuronium for the induction of general anesthesia, followed by desflurane and remifentanil. Cardiac output (CO) was estimated using esCCO technology. Ephedrine (0.1 mg/kg) was administered for the correction of hypotension. The primary and secondary outcome measures were changes in the mean arterial pressure (MAP) and CO, respectively, at 5 min after the administration of ephedrine.  RESULTS: The administration of ephedrine significantly increased MAP (p < 0.001, mean difference: 8.34 [95% confidence interval (CI), 5.95-10.75] mmHg) and CO (p < 0.001, mean difference: 7.43 [95% CI, 5.20-9.65] %) across all groups. However, analysis of variance revealed that the degree of elevation of MAP (F [2, 72] = 0.546, p = 0.581, η2 = 0.015 [95% CI, 0.000-0.089]) and CO (F [2, 72] = 2.023, p = 0.140, η2 = 0.053 [95% CI, 0.000-0.162]) did not differ significantly among the groups. Similarly, Spearman's rank correlation and multiple regression analysis revealed no significant relation between age and the changes in MAP or CO after the administration of ephedrine.

CONCLUSION

The administration of ephedrine significantly increased MAP and CO; however, no significant correlation with age was observed in patients aged > 45 years. These findings suggest that ephedrine is effective for the correction of hypotension during general anesthesia, even in elderly patients.

TRIAL REGISTRATION

UMIN-CTR (UMIN000045038; 02/08/2021).

Hypothesis: Fever control, a niche for alpha-2 agonists in the setting of septic shock and severe acute respiratory distress syndrome?

During severe septic shock and/or severe acute respiratory distress syndrome (ARDS) patients present with a limited cardio-ventilatory reserve (low cardiac output and blood pressure, low mixed venous saturation, increased lactate, low PaO2/FiO2 ratio, etc.), especially when elderly patients or co-morbidities are considered. Rescue therapies (low dose steroids, adding vasopressin to noradrenaline, proning, almitrine, NO, extracorporeal membrane oxygenation, etc.) are complex. Fever, above 38.5-39.5°C, increases both the ventilatory (high respiratory drive: large tidal volume, high respiratory rate) and the metabolic (increased O2 consumption) demands, further limiting the cardio-ventilatory reserve. Some data (case reports, uncontrolled trial, small randomized prospective trials) suggest that control of elevated body temperature ("fever control") leading to normothermia (35.5-37°C) will lower both the ventilatory and metabolic demands: fever control should simplify critical care management when limited cardio-ventilatory reserve is at stake. Usually fever control is generated by a combination of general anesthesia ("analgo-sedation", light total intravenous anesthesia), antipyretics and cooling. However general anesthesia suppresses spontaneous ventilation, making the management more complex. At variance, alpha-2 agonists (clonidine, dexmedetomidine) administered immediately following tracheal intubation and controlled mandatory ventilation, with prior optimization of volemia and atrio-ventricular conduction, will reduce metabolic demand and facilitate normothermia. Furthermore, after a rigorous control of systemic acidosis, alpha-2 agonists will allow for accelerated emergence without delirium, early spontaneous ventilation, improved cardiac output and micro-circulation, lowered vasopressor requirements and inflammation. Rigorous prospective randomized trials are needed in subsets of patients with a high fever and spiraling toward refractory septic shock and/or presenting with severe ARDS.

Comparison of surgical conditions following premedication with oral clonidine versus oral diazepam for endoscopic sinus surgery: A randomized, double-blinded study

Background and Aims:

Endoscopic sinus surgery (ESS) provides a challenge and an opportunity to the anesthesiologists to prove their mettle and give the surgeons a surgical field which can make their delicate surgery safer,more precise and faster. The aim of the study was to evaluate the surgical field and the rate of blood loss in patients premedicated with oral clonidine versus oral diazepam for endoscopic sinus surgery.

Material and Methods:

ASA I or II patients who were scheduled to undergo ESS were randomly allocated to group D (n = 30) or group C (n = 30). The patients' vital parameters, propofol infusion rate, and rate of blood loss were observed and calculated. The surgeon, who was blinded, rated the visibility of the surgical field from grade 0-5.

Results:

In the clonidine group, the rate of blood loss, the surgical time, propofol infusion rate was found to be statistically lower as compared to the diazepam group. Also a higher number of patients in the clonidine group had a better surgical score (better surgical field) than the diazepam group and vice versa.

Conclusions:

Premedication with clonidine as compared to diazepam, provides a better surgical field with less blood loss in patients undergoing ESS.

Hemodynamic effects of ephedrine and phenylephrine bolus injection in patients in the prone position under general anesthesia for lumbar spinal surgery

Ephedrine and phenylephrine (PE) are vasoconstrictors commonly used to restore the blood pressure (BP) to normal values. The aim of the present study was to investigate the effects of ephedrine and PE bolus administration on intra-arterial systolic BP (ISBP), intra-arterial diastolic BP (IDBP) and cardiac output (CO) in patients undergoing lumbar spine surgery in the prone position under general anesthesia (GA). In this prospective, randomized, and double-blind study, a total of 60 patients aged 20-60 years and undergoing elective lumbar spine surgery were administered either a single dose of ephedrine (0.1 mg/kg) or PE (1 µg/kg) through a central venous catheter as a bolus injection following the achievement of a stable hemodynamic status for ≥10 min. Following bolus injection of ephedrine or PE, a significant increase in ISBP was observed in the two experimental groups compared with pre-ephedrine and pre-PE values. The duration of the increment in ISBP however was significantly longer in the ephedrine group compared with the PE group. A similar response was observed in IDBP. A significant increase in CO began 1 min following ephedrine injection and lasted for the entire observation period, whereas the increase was only sustained for 3 min following bolus injection in the PE group. The results of the present study demonstrated that bolus ephedrine produces a more persistent pressor response and durable increase in CO and CI compared with PE when patients are in the prone position with GA for spine surgery.

Prone position results in enhanced pressor response to ephedrine compared with supine position during general anesthesia

STUDY OBJECTIVE

To elucidate and compare the pressor response to ephedrine in the prone or supine position during general anesthesia (GA).

DESIGN

Prospective cohort study.

SETTING

Department of General Surgery or Spine Surgery, Zhongda Hospital, Southeast University, Nanjing, China.

PATIENTS

Fifty-six patients who were scheduled to undergo elective surgery in the supine or prone position (n = 28 each) and using a generic GA protocol.

INTERVENTIONS

During surgery, the patients received intravenous (IV) ephedrine when their systolic blood pressure (SBP) decreased to 90 to 110 mm Hg.

MEASUREMENTS

Hemodynamic changes were measured at 1-minute intervals for 10 minutes and were compared with baseline.

MAIN RESULTS

Forty-nine patients (23 in the prone position and 26 in the supine position) completed the study. There were no significant differences between the groups with regard to demographic characteristics, hemodynamic parameters, end-tidal concentration of sevoflurane, and dose of propofol and remifentanil (all P> .05). After the bolus injection of ephedrine, a significant increase in SBP was observed in both groups compared to baseline, but the duration and magnitude of the increase in SBP were longer and greater in the prone position than in the supine position. The magnitude of increase of the mean blood pressure was significantly greater in the prone position compared to the supine position at 2 to 7 minutes after ephedrine injection. Ephedrine could cause significant increase in diastolic blood pressure 2 minutes after IV injection, which could last until at least 9 minutes in the prone position group compared to only for 5 minutes in the supine position group (all P< .05).

CONCLUSION

Compared to the supine position, the prone position could augment the pressor response to IV ephedrine during GA. Further studies are recommended to identify its association with other confounding factors such as surgery type or duration, patient history of cardiovascular disease, or patient hydration status.

Bradycardia in perspective-not all reductions in heart rate need immediate intervention

According to Wikipedia, the word 'bradycardia' stems from the Greek βραδύς, bradys, 'slow', and καρδία, kardia, 'heart'. Thus, the meaning of bradycardia is slow heart rate but not necessarily too slow heart rate. If looking at top endurance athletes they may have a resting heart rate in the very low thirties without needing emergent intervention with anticholinergics, isoprenaline, epinephrine, chest compressions or the insertion of an emergency pacemaker (Figure 1). In fact, they withstand these episodes without incident, accommodating with a compensatory increase in stroke volume to preserve and maintain cardiac output. With this in mind, it is difficult for the authors to fully understand and agree with the general sentiment amongst many pediatric anesthesiologists that all isolated bradycardia portends impending doom and must be immediately treated with resuscitative measures.

The effectiveness of intramuscular dexmedetomidine on hemodynamic responses during tracheal intubation and anesthesia induction of hypertensive patients: a randomized, double-blind, placebo-controlled study

BACKGROUND

Hypertensive patients are at risk for increased hemodynamic response to tracheal intubation. Sympatholytic drugs administered during the preinduction period may prevent adverse events.

OBJECTIVE

We assessed the effectiveness of a single preinduction IM bolus dose of dexmedetomidine (DMED) 2.5 μg/kg in attenuating hemodynamic responses to tracheal intubation and rapid-sequence anesthesia induction in hypertensive patients treated with angiotensin-converting enzyme inhibitors.

METHODS

Adult patients (American Society of Anesthesiologists classification II and III) with essential hypertension, scheduled for elective abdominal or gynecologic surgery, were enrolled in this randomized, double-blind, placebo-controlled study. Patients were assigned to i of 2 groups: the DMED group received IM DMED 2.5 μg/kg and the placebo group received IM saline 0.9% 45 to 60 minutes before induction of anesthesia. General anesthesia was induced with thiopental, fentanyl, and vecuronium and maintained with a sevoflurane-nitrous oxide-oxygen mixture. Hemodynamic values were recorded before (baseline) and after anesthesia induction, before endotracheal intubation, and 1, 3, and 5 minutes after intubation. The patients were monitored for hypotension (systolic arterial pressure [SAP] decreased ≥25% from baseline or to <90 mm Hg) or bradycardia (heart rate [HR] decreased ≥25% from baseline or to <50 beats/min).

RESULTS

Nine hundred sixty patients were assessed for enrollment during a 6-month period. Sixty patients (49 women, 11 men; mean [SD] age, 59.16 [8.39] years) were eligible for the study. There were no significant differences in baseline hemodynamic values between the groups. SAP and diastolic arterial pressure (DAP) before anesthesia induction, 1 and 3 minutes after intubation, and DAP 1 minute after intubation were significantly lower in the DMED group than in the placebo group (all, P < 0.05). There were no significant between-group differences in SAP or DAP 5 minutes after intubation. HR before anesthesia induction, before intubation, and 1, 3, and 5 minutes after intubation were lower in the DMED group than in the control group (all, P < 0.05). In the DMED group, SAP after intubation, DAP before intubation, 3 and 5 minutes after intubation, HR before induction, before intubation, and 3 and 5 minutes after intubation were significantly decreased compared with baseline values (all, P < 0.05). In the control group, SAP at all times, DAP before intubation, 1, 3, and 5 minutes after intubation, HR before intubation, and 3 and 5 minutes after intubation were significantly decreased compared with baseline values (all, P < 0.05). Hypotension and bradycardia were observed together in 3 patients, and hypotension alone was observed in 1 patient 3 minutes after intubation in the DMED group; hypotension was observed in 1 patient at 3 minutes after intubation in the control group.

CONCLUSION

The results of this study suggest that IM DMED 2.5 μg/kg administered 45 to 60 minutes before anesthesia induction attenuated, but did not completely prevent, hemodynamic responses to tracheal intubation in these patients with essential hypertension.

Effect of clonidine premedication on blood loss in spine surgery

Background:

Blood loss in spine surgery is an important issue, even though it has been understudied compared with hip and knee arthroplasty.

Objectives:

In this study, we evaluated the effect of oral clonidine as premedication on blood loss in lumbar spine fusion surgery under anesthesia with propofol and remifentanil.

Patients and Methods:

In this double-blind, randomized clinical trial, 30 patients who were undergoing lumbar spine posterior fusion surgery due to traumatic fracture were allocated randomly into 2 groups. The study group (clonidine group) received a 200-μg oral clonidine tablet 60–90 minutes before anesthesia, and the control group received placebo at the same time. Induction and maintenance of anesthesia and the mean target arterial pressure for controlled hypotension with remifentanil were the same in the 2 groups. We compared the amount of intraoperative blood loss, dose of remifentanil/hour administered, need for nitroglycerine to reach the mean target arterial pressure when remifentanil was insufficient, duration of operation, and surgeon’s satisfaction of a bloodless field between groups.

Results:

There was no statistically significant difference between groups in age (P = 0.115), sex (P = 0.439), weight (P = 0.899), operation time (P = 0.2), or American Society of Anesthesiologists physical status score (P = 0.390).

Intraoperative blood loss and remifentanil dose administered per hour in the clonidine group were significantly less than in the control group (P = 0.002 and P = 0.001, respectively), but there was no significant difference in surgeon’s satisfaction between groups (P = 0.169).

Conclusions:

As an oral premedication, clonidine can reduce surgical blood loss in lumbar spine posterior fusion surgery, even at the same levels of mean arterial pressure (MAP) with the control group. Its use can be studied in more complicated spine surgeries, such as scoliosis and spinal deformity surgeries.

Alpha-2 agonists to reduce vasopressor requirements in septic shock?

One of the unsolved problems of septic shock is the poor responsiveness, or reduced vascular reactivity, to vasopressors used to increase blood pressure (BP). Attempts to restore vascular reactivity with NO inhibitors or low dose steroids have met with little success. Low vascular reactivity, which may lead to refractory shock and death, is linked to desensitization or down-regulation of alpha-1 adrenergic receptors. Our working hypothesis is that the use of alpha-2 agonists (e.g. clonidine or dexmedetomidine) in septic shock, in addition to the state-of-the-art treatment (including volume load and vasopressors), will reduce the vasopressor requirements needed to restore adequate BP. This counter-intuitive proposal is based on the fact that alpha-2 agonists will reduce the massive release of endogenous catecholamines. A decrease in plasma endogenous catecholamine concentrations will be followed by reduced down-regulation of alpha-1 receptors and/or a gradual re-sensitization of alpha-1 adrenergic receptors. In turn, this will lead to lowered vasopressor requirement, with respect to dose and duration. Our hypothesis, based on a reverse "denervation hypersensitivity", is at variance with accepted treatments, which rest only on volume load and vasopressors and emphasizes restoration of blood pressure per se. Several observations in the cardiology and anesthesia setting have shown increased vascular reactivity following alpha-2 agonist administration. Our preliminary observations in the setting of septic shock again suggest such increased vascular reactivity. Improved outcome was also observed. Rigorous work is warranted to verify reduced vasopressor requirement and improved outcome, when an alpha-2 agonist is combined with state-of -the-art treatment of septic shock.

Oral clonidine attenuates the fall in mean arterial pressure due to scalp infiltration with epinephrine-lidocaine solution in patients undergoing craniotomy: a prospective, randomized, double-blind, and placebo controlled trial

BACKGROUND

Scalp infiltration with epinephrine-lidocaine solution in patients undergoing neurosurgery may result in transient but significant hypotension. We investigated whether premedication with alpha2-adrenoreceptor agonist clonidine, which also exhibits alpha1-adrenoreceptor mediated vasoconstriction, would prevent or attenuate this fall in mean arterial pressure (MAP).

METHODS

Sixty-six American Society of Anesthesiologists I and II adult patients, 18 to 50 years, undergoing elective tumor decompression were recruited into this prospective, randomized, double-blind, placebo controlled study, and scheduled to receive either oral pantoprazole 40 mg (placebo group) or oral clonidine 3 microg/kg (clonidine group), 90 minutes before induction of anesthesia. Primary end points studied were heart rate (HR) and MAP in both groups measured just before scalp infiltration (preinfiltration baseline) and then every 30 seconds for 5 minutes after initiation of scalp infiltration with 2.5 microg/mL epinephrine contained in 15 mL of 1% lidocaine solution.

RESULTS

There was no significant change in HR in the 2 groups during the study period compared with baseline values; however, patients in clonidine group had significantly lower HR compared with placebo (*P<0.05). In both groups, MAP fell significantly below baseline 1 minute after start of infiltration. It recovered in the clonidine group after 2.5 minutes but not in the placebo group where it continued to remain low even at 5 minutes. MAP in the placebo group was also significantly lower compared with the clonidine group from 2.5 minutes to 5 minutes.

CONCLUSION

In conclusion, oral clonidine 3 microg/kg administered 90 minutes before induction of anesthesia attenuates the fall in MAP due to scalp infiltration with a dilute concentration of epinephrine-lidocaine solution in patients undergoing craniotomy under isoflurane anesthesia.

Clonidine premedication effects on inhaled induction with sevoflurane in adults: a prospective, double-blind, randomized study

BACKGROUND

The purpose of this study was to evaluate whether oral clonidine premedication becomes an alternative to N2O in terms of shortening the induction time and attenuation of the adrenergic response to tracheal intubation during inhalation induction with sevoflurane, and to evaluate the quality of anesthetic induction according to the patient's satisfaction.

METHODS

We studied 84 female patients who were randomly allocated into four study groups: Groups I and II received a placebo orally, and Groups III and IV received clonidine at 150 and 300 microg, respectively, 90 min before induction of anaesthesia. Patients were anesthetized using a triple-deep-breath technique with 5% sevoflurane in Groups I, III and IV, and with 60% N2O-5% sevoflurane in group II.

RESULTS

Induction time was significantly longer (P < 0.05) in Group I. Increases in mean blood pressure and heart rate after tracheal intubation were significantly suppressed in Groups III and IV but not in Group II compared with Group I. Comfort and impression of anesthesia was better in Groups III and IV than in Groups I and II.

CONCLUSION

In volatile anesthetic induction, pre-anesthetic clonidine may become an alternative to N2O and may provide more comfort than with N2O.

[Strategies for perioperative sympatho-modulation]

Despite the growing evidence for the efficacy of different sympatho-modulatory therapies to lower perioperative cardiac morbidity and mortality, such therapeutic strategies are rather infrequently used in daily clinical practice. Most physicians involved in perioperative medicine are aware of the increasing literature related to this topic, but only few comply with current clinical practice guidelines even in the absence of contraindications. This review discusses possible explanations for this reluctance and again summarizes the basic and clinical principles of current sympatho-modulatory therapies including alpha(2)-agonism, beta-adrenergic antagonism, and regional anesthetic techniques in modern anesthetic practice. In addition, the emerging perioperative concept of a patient-tailored individualized pharmacotherapy based on "gene profiling", particularly the adrenergic polymorphisms, is discussed.

Differential pressor response to intravenous ephedrine during recovery from deliberate hypotension

STUDY OBJECTIVE

To determine whether nitroglycerin or trimethaphan alters pressor response to intravenous (i.v.) ephedrine.

DESIGN

Prospective, randomized study.

SETTING

Operating room of a university hospital.

PATIENTS

60 ASA physical status I female patients scheduled for mastectomy.

INTERVENTIONS

Patients were assigned to one of six groups (n = 10 in each). Group 1: nitroglycerin + normal saline (NS) i.v., Group 2: nitroglycerin + ephedrine 0.1 mg/kg i.v., Group 3: nitroglycerin + ephedrine 0.15 mg/kg i.v., Group 4: trimethaphan + NS i.v., Group 5: trimethaphan + ephedrine 0.1 mg/kg i.v., and Group 6: trimethaphan + ephedrine 0.15 mg/kg i.v.

MEASUREMENTS

Hemodynamic responses to ephedrine following withdrawal of vasodilators were observed for 15 minutes.

MAIN RESULTS

Ephedrine increased heart rate and mean blood pressure. After ephedrine 0.1 mg/kg i.v., the maximum pressor response in the trimethaphan group was approximately twofold that of the nitroglycerin group (p = 0.038).

CONCLUSIONS

Ephedrine restored BP more easily in those patients who had received trimethaphan compared with those who had received nitroglycerin for deliberate hypotension.

Oral Clonidine Premedication Exacerbates Hypotension Following Tourniquet Deflation by Inhibiting Noradrenaline Release

Clonidine premedication prevents tourniquet pain and reduces sympathetic nerve activity. We evaluated hemodynamic changes and catecholamine release following tourniquet deflation during spinal anesthesia in patients who received oral clonidine premedication. The final analysis included 24 otherwise healthy patients undergoing lower-limb surgery randomly assigned to two groups: those receiving approximately 5 micrograms/kg of oral clonidine 1 hr before anesthesia (clonidine group, n = 12), and those receiving no premedication (control group, n = 12). After lumbar anesthesia, a tourniquet was applied for approximately 60 minutes to each patient. Electrocardiogram, arterial blood pressure, and consumption of butorphanol for tourniquet pain were monitored. Blood samples were obtained at different times to measure serum concentration of catecholamine. In the clonidine group, mean blood pressure decreased from 87 +/- 7 mmHg at baseline to 65 +/- 10 mmHg after tourniquet deflation (P < 0.05). This peak reduction of mean blood pressure in the clonidine group was significantly lower than in the control group. After receiving clonidine premedication, the plasma noradrenaline concentrations in the clonidine group were significantly lower than those in the control group. Noradrenaline concentration increased in the control group from 162.3 +/- 89.2 pg/mL before tourniquet deflation to 199.3 +/- 95.7 pg/mL afterward (P < 0.01), but there was no significant change in noradrenaline concentration after tourniquet deflation in the clonidine group. We conclude that oral clonidine premedication exacerbated the reduction in mean blood pressure following tourniquet deflation by inhibiting noradrenaline release.

Propofol anesthesia enhances the pressor response to intravenous ephedrine

The induction of anesthesia with propofol is often associated with a decrease in arterial blood pressure (BP). Although vasopressors are sometimes required to reverse the propofol-induced hypotension, little is known about the effect of propofol on these drugs. We studied the effects of propofol and sevoflurane on pressor response to i.v. ephedrine. Thirty adult patients were randomly assigned to one of two groups. In the Propofol group (n = 15), patients received propofol 2.5 mg/kg i.v. for induction followed by 100 microg x kg(-1) x min(-1) i.v. for maintenance. In the Sevoflurane group (n = 15), anesthesia was induced with sevoflurane 3%-4% in oxygen and maintained with sevoflurane 2% in oxygen. All patients in both groups received ephedrine 0.1 mg/kg i.v. before and after the anesthetic induction. Ephedrine increased the heart rate significantly (P < 0.05) in awake patients in both study groups. In contrast, there was no increase in heart rate after the ephedrine administration under propofol or sevoflurane anesthesia. In awake patients, transient increases in mean BP were observed after i.v. ephedrine in both groups. In the Propofol group, 2 min after the administration of ephedrine, mean BP increased 16% +/- 10% under anesthesia but increased only 4% +/- 6% when the same patients were awake. The magnitudes of the pressor responses to ephedrine during propofol anesthesia were significantly greater (P < 0.05) than during the awake state. However, ephedrine 0.1 mg/kg i.v. showed no significant increases in BP during sevoflurane anesthesia. We conclude that propofol, not sevoflurane, anesthesia augments the pressor responses to i.v. ephedrine.

IMPLICATIONS

The effect of anesthetics on vasopressor-mediated cardiovascular effects is poorly understood. We evaluated the pressor response to ephedrine during propofol or sevoflurane anesthesia. Our study suggests that anesthesia-induced hypotension may be easier to reverse with ephedrine during propofol anesthesia than during sevoflurane anesthesia.

Effects of oral clonidine premedication on side effects of intravenous ketamine anesthesia: a randomized, double-blind, placebo-controlled study

STUDY OBJECTIVE

To determine the effects of oral clonidine premedication on hemodynamic changes during the entire course of ketamine anesthesia and incidence of postoperative adverse reactions.

DESIGN

Randomized, prospective, double-blind, placebo-controlled study.

SETTING

Department of Anesthesiology, University of Tsukuba Hospital, Ibaraki, Japan.

PATIENTS

39 ASA physical status I and II patients undergoing superficial surgeries.

INTERVENTIONS

Placebo, clonidine 2.5 micrograms/kg, and clonidine 5 micrograms/kg groups received respective doses of oral clonidine 90 minutes prior to surgery. Anesthesia was induced with ketamine 2 mg/kg intravenously (i.v.), trachea was intubated, and anesthesia was maintained with 67% nitrous oxide, oxygen, and supplemental ketamine (1 mg/kg) when systolic blood pressure and heart rate (HR) exceeded 180 mmHg and 100 bpm, respectively.

MEASUREMENTS AND MAIN RESULTS

In the clonidine 2.5 micrograms/kg group, HR response to tracheal intubation was significantly less, while in the clonidine 5 micrograms/kg group both mean arterial pressure and HR responses were significantly suppressed, compared with the placebo group. Intraoperative coefficients of variations of HR were significantly less in both clonidine groups than the placebo group. Incidence of nightmare and degree of salivation were significantly less in the clonidine 5 micrograms/kg group than in the placebo group.

CONCLUSION

Oral clonidine 2.5 micrograms/kg and clonidine 5 micrograms/kg attenuates cardiostimulatory effects, while clonidine 5 micrograms/kg was associated with reduced incidence and severity of nightmare and salivation attributable to i.v. ketamine.

Hemodynamic responses induced by dopamine and dobutamine in anesthetized patients premedicated with clonidine

To test the hypothesis that the pharmacological effects of dopamine (DOA) and dobutamine (DOB) are altered when there is inhibition of the release of norepinephrine from nerve endings, we examined the hemodynamic responses to DOA and DOB in anesthetized patients premedicated with oral clonidine. Seventy adult patients were assigned to one of two groups (oral premedication with clonidine 5 microg/kg or no premedication). After the induction of general anesthesia, heart rate and systemic blood pressure (BP) were measured for 10 min after each of five IV infusions (3 and 5 microg x kg(-1) x min(-1) of DOA; 0.5, 1, and 3 microg x kg(-1) x min(-1) of DOB) in a randomized, double-blind manner. In patients given clonidine, the mean BP increases induced by DOA 5 microg x kg(-1) x min(-1) were significantly attenuated (P < 0.01), whereas the mean BP increases induced by DOB-0.5, 1, or 3 microg x kg(-l) x min(-1) were significantly enhanced (P < 0.01 or 0.05). The heart rate responses to DOA and DOB did not differ between patients with or without clonidine. Premedication with clonidine alters the effects on BP to both DOA and DOB. When small doses of DOA or DOB are used in clonidine-premedicated patients, differences of pharmacological profiles need to be considered for perioperative management.

IMPLICATIONS

Our randomized, double-blind study suggests that premedication with clonidine may enhance the effect on blood pressure response to a small dose of dobutamine (direct-acting) and attenuate that to a small dose of dopamine (mixed direct-and indirect-acting) in patients anesthetized with fentanyl and nitrous oxide.

Propofol anesthesia enhances pressor response to ephedrine in patients given clonidine

We studied the hemodynamic effects of ephedrine in patients with or without clonidine premedication during either isoflurane or propofol anesthesia. Forty adult patients were randomly assigned to one of two groups: 20 patients received famotidine 20 mg orally (control group) and 20 received clonidine 3 microg/kg and famotidine 20 mg orally (clonidine group). Within each group, 10 patients were then anesthetized with isoflurane and 10 with propofol. Hemodynamic measurements were taken at 1-min intervals for 10 min after a bolus injection of ephedrine 0.1 mg/kg. The magnitude of the maximal pressor response to ephedrine was no different whether patients without clonidine were anesthetized with isoflurane (increase 5+/-7 mm Hg) or propofol (3+/-9 mm Hg); however, this response was greater (P<0.05) with propofol (17+/-6 mm Hg) versus isoflurane (6+/-5 mm Hg) in patients given clonidine. The arterial blood pressure increase in clonidine-premedicated patients with propofol anesthesia was the largest among the four subgroups. The heart rate response to ephedrine was not significant in patients anesthetized with isoflurane and was small but significant in those anesthetized with propofol. The present results, together with previous studies on the effect of ephedrine in patients medicated with clonidine, suggest that the interaction between clonidine and ephedrine is modulated by the anesthetic used.

IMPLICATIONS

We evaluated the pressor response to ephedrine during isoflurane or propofol anesthesia with or without clonidine premedication. Our study suggests that, in anesthetized patients premedicated with clonidine, decreases in blood pressure may be easier to reverse with ephedrine with some types of anesthesia (e.g., propofol) than with others (e.g., isoflurane).

The effects of clonidine on sensitivity to phenylephrine and nitroprusside in patients with essential hypertension recovering from surgery

Clonidine reduces postoperative circulatory instability in patients with essential hypertension. It also increases the sensitivity to vasopressors before and during anesthesia. We investigated blood pressure responses to phenylephrine and nitroprusside pre- vs postoperatively and the effect of clonidine on these responses in patients with essential hypertension. Twenty patients received clonidine 6 microg/kg orally 120 min before anesthesia and 3 microg/kg IV over the final hour of surgery or an identical placebo. During increasing bolus doses of phenylephrine and nitroprusside (30-300 microg), the maximal systolic pressure responses were recorded at baseline on the day before surgery, before the induction of anesthesia, and 1 and 3 h postoperatively. Sensitivity to phenylephrine and nitroprusside was interpolated from linear regression of the data. There was no difference between preoperative and postoperative sensitivity to phenylephrine or nitroprusside in either group. Clonidine increased sensitivity to phenylephrine versus placebo before and after surgery (response to dose of 1.5 microg/kg: 42+/-14 vs 27+/-8 mm Hg preinduction, 37+/-10 vs 26+/-8 mm Hg 3 h postoperatively; both P < 0.01), but not to nitroprusside (38+/-6 vs 37+/-10 mm Hg preinduction and 40+/-6 vs 39+/-8 mm Hg postoperatively). Clonidine increases the sensitivity to phenylephrine but not nitroprusside at baseline and postoperatively in hypertensive patients.

IMPLICATIONS

Clonidine increases the sensitivity to bolus injections of the vasoconstrictor phenylephrine, but not the vasodilator sodium nitroprusside, before and after surgery in patients with preexisting hypertension. The doses of vasopressors should be reduced accordingly in hypertensive patients receiving perioperative clonidine.

Comparative effects of oral clonidine and intravenous esmolol in attenuating the hemodynamic response to epinephrine injection

STUDY OBJECTIVE

To evaluate oral clonidine and intravenous esmolol in blunting hemodynamic changes associated with intranasal injection of an epinephrine-containing local anesthetic solution during general anesthesia.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

University Medical Center.

PATIENTS

61 consenting ASA physical status I and II outpatients undergoing endoscopic sinus and septoplasty surgery with general anesthesia.

INTERVENTIONS

All patients were assigned to receive either a placebo (P) tablet or a similar-appearing tablet containing either clonidine 0.2 mg (C2) or 0.4 mg (C4) orally 1 hour prior to entering the operating room. Prior to the intranasal injection of epinephrine, patients were administered either saline, 0.03 ml.kg-1 followed by an infusion of 0.016 ml.kg-1.min-1, or esmolol (E) 300 micrograms.kg-1 followed by a continuous infusion of 160 micrograms.kg-1.min-1.

MEASUREMENTS AND MAIN RESULTS

Arterial blood pressure and heart rate (HR) values were recorded preoperatively, immediately before induction of anesthesia, and at 1-minute intervals after induction of anesthesia until 15 minutes after injection of an epinephrine-containing solution. Level of sedation was assessed using a linear visual analog scale (VAS) prior to oral premedication, immediately before induction of anesthesia, and 30 minutes after anesthesia. There were no significant differences in sedation scores among the four treatment groups. HR following injection of epinephrine-containing solution was significantly less in the C2, C4, and E groups than the placebo group. Compared to P and E treatment groups, MAP values were significantly lower in the C4 treatment group.

CONCLUSION

In this healthy, young, nonsmoking outpatient population, premedication with oral clonidine, 0.2 to 0.4 mg, was effective in blunting the acute hemodynamic changes associated with injection of an epinephrine-containing local anesthetic solution during endoscopic sinus or septoplasty surgery.

Oral clonidine premedication enhances the pressor response to ephedrine during spinal anesthesia

Clonidine premedication enhances the pressor effects of ephedrine in awake and anesthetized patients. To test the hypothesis that clonidine augments the pressor response to ephedrine during spinal anesthesia, 48 ASA physical status I or II patients were randomly assigned to either the clonidine group (n = 23), receiving oral clonidine approximately 5 microg/kg 90 min before spinal anesthesia, or the control group (n = 25), receiving no clonidine. Spinal anesthesia was performed at either the L2-3 or the L3-4 interspace using 0.5% hyperbaric tetracaine solution 1.4-3.0 mL. Blood pressure (BP), heart rate, and the upper dermatomal level of analgesia were determined at 1-min intervals with the patient in the supine position after tetracaine injections. When systolic BP decreased to <80% of the prespinal value or <100 mm Hg, IV ephedrine 0.2 mg/kg was administered as a bolus. There were no differences in the duration until the first dose of ephedrine after tetracaine injections, and the upper level of analgesia between groups (control group 8.5+/-3.7 min, T5; clonidine group 7.7+/-2.7 min, T6). Although prespinal and preephedrine BP values were higher in the control group, the magnitude of increases in mean BP after ephedrine was significantly greater in the clonidine group (P < 0.05). We conclude that oral clonidine premedication augments the pressor response to IV ephedrine during spinal anesthesia.

IMPLICATIONS

The pressor effect of ephedrine is enhanced in patients given oral clonidine premedication during spinal anesthesia.

Clonidine premedication modifies responses to adrenoceptor agonists and baroreflex sensitivity

PURPOSE

To evaluate the effects of clonidine on responses to adrenoceptor agonists and baroreflex sensitivity, we examined arterial blood pressure (AP) responses to phenylephrine and heart rate (HR) responses to isoproterenol and baroreflex sensitivity (HR response to AP changes due to phenylephrine or nitroglycerin).

METHODS

We studied 60 anaesthetized patients who either did or did not receive 5 micrograms.kg-1 clonidine po before they were anaesthetized. After induction of general anaesthesia, the patients received 3 micrograms.kg-1 phenylephrine, 0.02 microgram.kg-1 isoproterenol, or 2-3 micrograms.kg-1 nitroglycerin, and haemodynamic measurements were taken. Baroreflex sensitivity was expressed as the slope of the linear regression line (msec.mmHg-1; in msec of R-R interval change vs mmHg change in systolic arterial pressure) following the administration of phenylephrine and nitroglycerin.

RESULTS

Patients who received clonidine had greater augmented responses in AP to phenylephrine and in HR to isoproterenol (47.2 +/- 15.6% vs 23.7 +/- 11.9% for increase in systolic AP and 59.8 +/- 22.6% vs 26.2 +/- 11.0% for increase in HR, P < 0.05 respectively). There were no differences between the baroreflex sensitivities in the pressor (phenylephrine) test groups (3.77 +/- 1.08 vs 4.41 +/- 1.66 msec.mmHg-1). In contrast, the slopes of depressor (nitroglycerin) test groups were decreased in patients receiving clonidine (1.98 +/- 0.73 vs 3.68 +/- 1.72 msec.mmHg-1, P < 0.05).

CONCLUSION

The results suggest that premedication with clonidine might enhance critical hypotension during anaesthesia and surgery, but restoration both of AP and HR decrease can be achieved effectively by phenylephrine and isoproterenol i.v., respectively.

The optimal test dose of epinephrine for epidural injection with lidocaine solution in awake patients premedicated with oral clonidine

We attempted to determine the optimal test dose of epinephrine for use with epidural anesthesia in awake patients premedicated with clonidine. Eighty-eight adult patients were randomized into two groups [oral premedication with clonidine 5 microg/kg (CLON) or no premedication (CONT)]. Before induction of general anesthesia, heart rate (HR) and blood pressure (BP) were measured for 3 min after the i.v. injection of 3 mL of 1.5% lidocaine containing epinephrine (0, 1.25, 2.5, 5, 7.5, or 15 microg) in a randomized, double-blind manner. We calculated 95% confidence intervals for the peak HR and BP increases induced by each dose of epinephrine. At 7.5 microg, epinephrine induced a significantly greater increase in HR and BP in CLON than in CONT. The 95% confidence interval for the HR change induced by 7.5 microg of epinephrine in CLON was nearly the same as the accepted standard dose of epinephrine (15 microg) in CONT. We conclude that premedication with clonidine enhances HR and BP responses to the i.v. administration of epinephrine-containing epidural test solutions. Consequently, 7.5 microg of epinephrine may be sufficient to enable detection of accidental injection into a blood vessel in awake patients premedicated with clonidine 5 microg/kg.

IMPLICATIONS

Clonidine, a commonly used preanesthetic medication, alters patients' cardiovascular responses to drugs such as epinephrine. Our randomized, double-blind study suggests that, in awake patients receiving oral clonidine premedication, 7.5 microg of epinephrine (half the usual dose) is adequate as an indicator of accidental injection into the epidural vessels during epidural anesthesia.

The effects of intraoperative intravenous clonidine on fluid requirements, hemodynamic variables, and support during liver transplantation: a prospective, randomized study

In this prospective, nonblind study, we report the use of clonidine during orthotopic liver transplantation (OLT). Twenty adult patients in a stable medical condition were studied. General anesthesia consisted of isoflurane in air/oxygen and sufentanil. Patients in the clonidine group received a slow i.v. infusion (15 min) of 4 microg/kg clonidine during induction. The other patients were used as controls. I.v. fluid requirements were determined as follows: albumin (4% solution) was administered to maintain filling pressures to a pulmonary capillary wedge pressure (PCWP) of more than 12 mm Hg. Packed red blood cells were transfused to maintain a hemoglobin level of 8-9 g/dL. Circulatory stability was evaluated using: systolic and diastolic arterial blood pressure and heart rate recorded at 2-min intervals; and the vasopressor/inotropic support required to maintain adequate hemodynamic variables after reperfusion. Intraoperative albumin and packed red blood cell requirements were significantly reduced in patients in the clonidine group (1644 +/- 140 and 50 +/- 50 mL vs 2867 +/- 226 mL and 1350 +/- 443 mL; P < 0.05). Heart rate was significantly slower in patients of the clonidine group. There were no differences in systolic arterial blood pressure. After reperfusion, patients in the control group showed significantly lower diastolic arterial blood pressure, required more vasopressor/inotropic support, and were more acidotic than patients in the clonidine group. We conclude that the administration of 4 microg/kg clonidine during induction of OLT significantly reduced the intraoperative requirements of i.v. fluids and blood products without compromising circulatory stability. Improvement in immediate reperfusion-induced disturbances was observed.

IMPLICATIONS

The administration of 4 microg/kg clonidine during induction of liver transplantation significantly reduced the intraoperative requirements for i.v. fluids and blood products without compromising the circulatory stability. Improvement in immediate reperfusion-induced disturbances was also observed.

Oral clonidine premedication does not alter the efficacy of epidural test doses in adult patients anesthetized with isoflurane

Clonidine premedication has been increasingly used in clinical anesthesia. Though clonidine was found to alter pressor responses to various sympathomimetics, its effect on epidural test dose efficacy to detect intravascular injection has never been evaluated. Eighty healthy patients were randomly assigned to one of four groups, each of which was anesthetized with 1% end-tidal isoflurane and 67% nitrous oxide in oxygen after endotracheal intubation. The control-epinephrine group (n=20) given no clonidine premedication received 3 ml of 1.5% lidocain with 15 μg epinephrine (1:200000) intravenously to simulate an intravenously administered epidural test dose. The control-saline group (n=20) given no clonidine premedication received 3 ml of normal saline intravenously. The clonidine-epinephrine and clonidine-saline groups (n=20 each) were identical to the control groups, but were premedicated with oral clonidine, approximately 5 μg·kg(-1), 90 min before induction of general anesthesia. Heart rate (HR) and systolic blood pressure (SBP) were measured by a blinded observer at 20-s intervals for 4 min after intravenous injections of the test dose or saline. Following intravenous test dose injection, there were no significant diferences between the control-epinephrine and the clonidine-epinephrine groups in mean maximum increments of both HR (28±3vs 30±3 bpm, [mean±standard error], respectively) and SBP (46±6vs 45±4 mmHg, respectively). Six patients in the control-epinephrine and 4 in the clonidine-epinephrine group developed negative HR responses (HR increment <20 bpm). Since HR and SBP were essentially unchanged in the two groups receiving saline, sensitivities (negative predictive values) based on the HR criterion (positive if ≥20 bpm increase in HR) were 80% and 70% (83% and 77%) with and without clonidine premedication, respectively (P>0.05 between groups). However, when a modified HR criterion (positive if ≥10 bpm increase in HR) was used, sensitivities, specificities, and positive and negative predictive values were all 100% with or without clonidine. On the other hand, all of 20 patients in the control-epinephrine and the clonidine-epinephrine groups exhibited positive SBP responses (SBP increment ≥15 mmHg). Therefore, based on the SBP criterion, sensitivities, specificities, and positive and negative predictive values were all found to be 100% regardless of the presence of clonidine. We conclude that oral clonidine 5μg·kg(-1) premedication alters neither (a) hemodynamic responses to the intravenously administered epidural test dose containing 15 μg epinephrine, nor (b) the efficacy for detecting intravascular injection based on either criterion in adult patients under stable isoflurane anesthesia.

Hemodynamic effects of oral clonidine premedication in lumbar epidural anesthesia

Clonidine, an α₂-adrenergic agonist, has a potent sympatholytic effect and augments the pressor effect of ephedrine during general anesthesia. We evaluated whether oral clonidine premedication would alter the hemodynamic changes and enhance the pressor response to intravenous ephedrine during epidural anesthesia in 35 adult patients. They were randomly administered either premedication with clonidine approximately 5 μg·kg^-1 po (n=17) or no clonidine medication (n=18). After establishment of epidural anesthesia, the hemodynamic response to ephedrine iv was measured in the awake state at 1-min intervals for 10 min. Then, the same hemodynamic measurement was repeated in the asleep state induced with midazolam iv. There were no differences in blood pressure (BP) and heart rate values between groups during the onset of epidural anesthesia, except that BP before epidural anesthesia was lower in the clonidine group than the control group (P<0.05). The magnitude and duration of pressor responses to ephedrine were comparable between groups in awake and asleep states. In conclusion oral clonidine premedication 5 μg·kg^-1 alters neither the hemodynamic changes nor the pressor response to intravenous ephedrine during epidural anesthesia.

Oral clonidine premedication enhances the quality of postoperative analgesia by intrathecal morphine

Since clonidine potentiates the analgesia by morphine, the current study was performed to investigate whether oral clonidine premedication would enhance the postoperative analgesia by intrathecal morphine. Twenty-six patients, aged 37-60 yr, schedule for abdominal total hysterectomy under spinal anesthesia, were studied. Patients were randomly allocated to one of two groups; the clonidine group (n = 13) received oral clonidine approximately 5 micrograms/kg, and the control group (n = 13) received no clonidine. All patients received hyperbaric tetracaine 12 mg dissolved in 10% dextrose and morphine 0.2 mg for spinal anesthesia. We measured duration of analgesia (time to the first request for supplemental analgesics) and motor block. We also recorded the total number of injections of supplemental analgesics, and intensity of postoperative visual analog pain scores, nausea, and pruritus for 48 h after intrathecal administration. Duration of analgesia in the clonidine group was longer than the control group (2017 +/- 263 vs 1190 +/- 199 min, mean +/- SEM; P < 0.05). Although there was no difference in the total number of injections of supplemental analgesics (1.1 +/- 0.4 and 2.2 +/- 0.3 in the clonidine and control groups, respectively), the number of patients not requiring supplemental analgesics during the entire study period was larger in the clonidine group than the control group (six patients versus one patient; P < 0.05). There were no differences at any observation point between groups in visual analog pain scores, or the incidence of nausea and pruritus. Oral clonidine preanesthetic medication enhances the postoperative analgesia of intrathecal morphine plus tetracaine without increasing the intensity of side effects from morphine.

Enhancement of pressor response to ephedrine following clonidine medication

We studied pressor responses and changes in plasma catecholamine concentrations following two consecutive doses of ephedrine 0.1 mg.kg-1 with (n = 20) and without (n = 20) clonidine 5 micrograms.kg-1 premedication in patients presenting for a variety of major surgical procedures under general anaesthesia. Arterial blood pressure and heart rate were measured at 1 min intervals for 10 min, and plasma catecholamines were measured before and 3 min after each dose of ephedrine. Mean blood pressure changes from the baseline values were greater in the clonidine than in the control group 3-8 min and 4-9 min following the first and the second doses of ephedrine, respectively (p < 0.05). Plasma catecholamine concentrations tended to be lower in the clonidine group throughout the study. The augmented pressor response to ephedrine in clonidine-treated patients can be attributed to enhanced cardiovascular response rather than clonidine-induced accumulation and subsequent increased release of catecholamine.

Effects of ephedrine on oxygen consumption and cardiac output

Bolus doses of ephedrine are often used by anaesthesiologists for intraoperative hypotension. This randomized single-blind cross-over study was designed to simultaneously evaluate circulatory, respiratory and metabolic effects of intravenously given ephedrine in 12 healthy male volunteers. Oxygen uptake and carbon dioxide excretion were measured with indirect calorimetry and non-invasive transthoracic electrical bioimpedance was used for cardiac output measurements. The maximum effect on most variables was reached at 4-5 min. At 5 min after the administration of ephedrine 0.1 mg per kilogram body weight, there were significant increases in cardiac index, systolic and mean arterial blood pressure, expired minute volume, oxygen uptake and carbon dioxide excretion rates. There were no significant changes in the quotient between oxygen uptake rate and cardiac index, VO2/CI during the 30 min study period. The O2 saturation was not altered. The present study indicates that ephedrine increases oxygen demand and supply in a similar magnitude.

Epidemiology of the adverse hemodynamic events occurring during "clonidine anesthesia": a prospective open trial of intraoperative intravenous clonidine

STUDY OBJECTIVE

Determine the hemodynamic consequences of intraoperative clonidine during major abdominal surgery.

DESIGN

Prospective open trial.

SETTING

Teaching hospital.

PATIENTS

402 consecutive patients scheduled for major abdominal surgery.

INTERVENTIONS

350 consecutive patients received intravenous (IV) clonidine (loading dose of 4 micrograms/kg in 20 minutes at anesthesia induction, followed by a continuous infusion of 2 micrograms/kg/h until the end of surgery). Fifty-two additional patients served as controls. Anesthetic technique consisted of balanced anesthesia (isoflurane, fentanyl, atracurium). ECG, invasive arterial blood pressure (BP), expiratory PCO2 and pulse oximetry were continuously recorded. Hemodynamic events (HEs) were defined as moderate for a 20% reduction of the baseline systolic blood pressure (SBP) or a heart rate (HR) decreasing between 50 beats per minute (bpm) and 40 bpm. A 30% reduction of the baseline SBP or a HR below 40 bpm was considered an important HE. The rate and duration of these events were recorded from induction to recovery. HEs requiring a specific treatment were noted. Central venous pressure, volume of fluid infused, and urinary output were also recorded.

MEASUREMENTS AND MAIN RESULTS

21% of control patients and 31% of clonidine patients had no adverse HEs. A moderate reduction of the baseline BP was the most common episode in both groups. The incidence of the HEs (moderate and important) was similar in both groups but the duration HEs was significantly longer in the clonidine patients (p < 0.05). 40% of the control patients and 13% of the clonidine patients required specific management for their HEs (p < 0.05), the most common of which was hypotension without bradycardia. Neither coexisting pathology nor preoperative medications influenced the incidence of HEs.

CONCLUSION

IV clonidine can be used routinely during anesthesia for major abdominal surgery.