Clonidine provides opioid-sparing effect, stable hemodynamics, and renal integrity during laparoscopic cholecystectomy

Urinary oxygen tension and its role in predicting acute kidney injury: A narrative review

Acute kidney injury occurs frequently in the perioperative setting. The renal medulla often endures hypoxia or hypoperfusion and is susceptible to the imbalance between oxygen supply and demand due to the nature of renal blood flow distribution and metabolic rate in the kidney. The current available evidence demonstrated that the urine oxygen pressure is proportional to the variations of renal medullary tissue oxygen pressure. Thus, urine oxygenation can be a candidate for reflecting the change of oxygen in the renal medulla. In this review, we discuss the basic physiology of acute kidney injury, as well as techniques for monitoring urine oxygen tension, confounding factors affecting the reliable measurement of urine oxygen tension, and its clinical use, highlighting its potential role in early detection and prevention of acute kidney injury.

Effectiveness of the oral Clonidine as a pre-anesthetic medicine for thyroidectomy surgery; A randomized clinical trial

Introduction

Hemodynamic disturbance is a common problem in patients undergoing thyroid surgery. It may be due to episodic increases in thyroid hormones (thyroid storm) or stimulation of the carotid sinus baroreflex. The aim of the present study was to investigate effectiveness of the pre-operative oral Clonidine on reducing these hemodynamic changes during total thyroidectomy surgery.

Methods

In a prospective, randomized, double-blind study, 80 patients scheduled for elective total thyroidectomy were randomized to receive either 0.2 mg Clonidine (n=40) or a matched placebo (n=40) orally sixty minutes before entering the operating room. Hemodynamic variables, the duration of surgery, estimated amount of blood loss and the dose of administered remifentanil were recorded for further analysis.

Results

Oral Clonidine was found to be significantly better in maintaining stable hemodynamics compared to the control group. Also, In the Clonidine group, the estimated amount of blood loss (110.4±10 ml vs. 182.2±11.4 mL, P=0.04), duration of the surgery (78.26±55.2 min vs. 105.16±61.75 min, P=0.027) and administered dose of remifentanil (26.67±6.6 μg vs. 216.2±14.8 μg, P=0.01) were also significantly lower than the control group.

Conclusion

Pre-operative administration of 0.2 mg oral Clonidine in patients undergoing total thyroidectomy results in improved perioperative hemodynamic stability and reduced response to perioperative stress.

A Randomized Controlled Study to Compare Hemodynamic Effects between Clonidine and Pregabalin in Laparoscopic Cholecystectomy

Background:

Laparoscopic cholecystectomy (LC) is associated with pneumoperitoneum and hemodynamic disturbances. Pregabalin and Clonidine have been used for anesthetic effects, but a better drug for controlling hemodynamic parameters is being investigated.

Aims:

The study was done to assess and compare the efficacy of preoperative single oral dose of pregabalin and clonidine in maintaining the hemodynamic parameters in the LC.

Settings and Design:

The prospective, interventional, randomized, comparative, single-blinded study was conducted in the department of anesthesia and surgery from January 2015 to September 2016 after taking approval from the institutional ethical committee.

Materials and Methods:

The study included a total of 90 patients, aged between 18 and 56 years of both sexes scheduled for elective LC. Patients were randomized into three groups of 30 each who received oral pregabalin 150 mg, clonidine 200 ug, and placebo. The hemodynamic parameters were recorded at various time intervals along with any adverse events.

Statistical Analysis:

Quantitative variables were compared using unpaired t-test (when the data sets were not normally distributed) between the two groups. Qualitative variables were compared using Chi-square test/Fisher's exact test. P < 0.05 was considered statistically significant.

Results:

There was a significant increase in the heart rate (HR) and systolic, diastolic, and mean blood pressure during laryngoscopy and pneumoperitoneum in the control group as compared to both pregabalin and clonidine. HR was significantly lower in clonidine group after extubation and in postoperative period than both control group and pregabalin group. There was no major difference in the incidence of side effects.

Conclusion:

Both pregabalin (150 mg) and clonidine (200 ug) were effective in controlling the hemodynamic parameters during LC, with clonidine providing better hemodynamic stability than Pregabalin.

Increased Intra-Abdominal Pressure During Laparoscopic Pneumoperitoneum Enhances Albuminuria via Renal Venous Congestion, Illustrating Pathophysiological Aspects of High Output Preeclampsia

Intra-abdominal hypertension (IAH) causes severe organ dysfunction. Our aim is to evaluate the effect of increased intra-abdominal pressure (IAP) on renal function, hypothesizing that venous congestion may increase proteinuria and fluid retention without endothelial dysfunction. Three urine samples were collected from 32 non-pregnant women undergoing laparoscopic-assisted vaginal hysterectomy (LAVH) and from 10 controls placed in Trendelenburg position for 60 min. Urine sampling was done before (PRE), during or immediately after (PER), and two hours after (POST) the procedure. Urinary albumin, protein and creatinine concentrations were measured in each sample, and ratios were calculated and compared within and between groups. During LAVH, the albumin/creatinine ratio (ACR) increased and persisted POST-procedure, which was not observed in controls. A positive correlation existed between the LAVH duration and the relative change in both ACR and protein/creatinine ratio (PCR) PER- and POST-procedure. Iatrogenic IAH increases urinary ACR and PCR in non-pregnant women via a process of venous congestion. This mechanism might explain the presentation of one specific subtype of late-onset preeclampsia, where no drop of maternal cardiac output is observed.

Effects of Dexmedetomidine on Intraoperative Hemodynamics and Propofol Requirement in Patients Undergoing Laparoscopic Cholecystectomy

Background

Despite multiple benefits, laparoscopic surgery always poses anesthetic challenge due to significant alteration of hemodynamics. Various pharmacological agents have been used for the same with variable response. Dexmedetomidine, in addition to sympatholytic effect, diminishes intraoperative requirement of anesthetics including propofol. The present study was conducted to evaluate the effects of intravenous dexmedetomidine on intraoperative hemodynamics and propofol requirement using bispectral index (BIS) in laparoscopic cholecystectomy.

Methods

Forty patients undergoing laparoscopic cholecystectomy were randomly allocated to receive either dexmedetomidine (Group A; n = 20) or normal saline (Group B; n = 20). In Group A, dexmedetomidine was loaded (1 μg/kg) before anesthesia induction and infused (0.6 μg/kg/h) during surgery. Anesthesia was induced with propofol, and maintenance infusion rate was adjusted to a BIS of 55-60 in both groups. Mean arterial pressure (MAP) and heart rate (HR) were recorded at baseline and at various time points from loading of drugs to just after tracheal extubation. All infusions were stopped with removal of scope from abdominal cavity. Recovery time (time from end of all infusions to BIS = 80) and extubation time (time from end of all infusions to extubation) were noted.

Results

After intubation, MAP and HR values in Group A were significantly lower than Group B at various time points of study. To achieve similar BIS values, significantly low doses of propofol were required in Group A during induction and intraoperatively. Doses were reduced by 36% and 31%, respectively. Mean recovery time and mean extubation time in Group A were also significantly less.

Conclusion

During propofol-based anesthesia for laparoscopic cholecystectomy, dexmedetomidine provides stable intraoperative hemodynamics and reduces propofol requirement for induction as well as maintenance, without compromising recovery profile.

Laparoscopic surgery: a narrative review of pharmacotherapy in pain management

Laparoscopic surgery is widespread, and an increasing number of surgeries are performed laparoscopically. Early pain after laparoscopy can be similar or even more severe than that after open surgery. Thus, proactive pain management should be provided. Pain after laparoscopic surgery is derived from multiple origins; therefore, a single agent is seldom sufficient. Pain is most effectively controlled by a multimodal, preventive analgesia approach, such as combining opioids with non-opioid analgesics and local anaesthetics. Wound and port site local anaesthetic injections decrease abdominal wall pain by 1-1.5 units on a 0-10 pain scale. Inflammatory pain and shoulder pain can be controlled by NSAIDs or corticosteroids. In some patient groups, adjuvant drugs, ketamine and α2-adrenergic agonists can be helpful, but evidence on gabapentinoids is conflicting. In the present review, the types of pain that need to be taken into account while planning pain management protocols and the wide range of analgesic options that have been assessed in laparoscopic surgery are critically assessed. Recommendations to the clinician will be made regarding how to manage acute pain and how to prevent persistent postoperative pain. It is important to identify patients at the highest risk for severe and prolonged post-operative pain, and to have a proactive strategy in place for these individuals.

Premedication with clonidine versus fentanyl for intraoperative hemodynamic stability and recovery outcome during laparoscopic cholecystectomy under general anesthesia

BACKGROUND

Laparoscopic cholecystectomy under general anesthesia induced intraoperative hemodynamic responses which should be attenuated by appropriate premedication. The present study was aimed to compare the clinical efficacy of clonidine and fentanyl premedication during laparoscopic cholecystectomy for attenuation of hemodynamic responses with postoperative recovery outcome.

SUBJECTS AND METHODS

In this prospective randomized double blind study 64 adult consented patients of either sex with ASA I and II, scheduled for elective laparoscopic cholecystectomy under general anesthesia and met the inclusion criteria, were allocated into two groups of 32 patients. Group C patients have received intravenous clonidine 1μg kg(-1) and Group F patients have received intravenous fentanyl 2μg kg(-1) 5 min before induction. Anesthetic and surgical techniques were standardized. All patients were assessed for intraoperative hemodynamic changes at specific time and postoperative recovery outcome.

RESULTS

Premedication with clonidine or fentanyl has attenuated the hemodynamic responses of laryngoscopy and laparoscopy. Clonidine was superior to fentanyl for intraoperative hemodynamic stability. No significant differences in the postoperative recovery outcome were observed between the groups. Nausea, vomiting, shivering and respiratory depression were comparable between groups.

CONCLUSION

Premedication with clonidine or fentanyl has effectively attenuated the intraoperative hemodynamic responses of laparoscopic cholecystectomy.

Preemptive analgesia of oral clonidine during subarachnoid block for laparoscopic gynecological procedures: A prospective study

BACKGROUND

Preemptive analgesia is known modality to control the peri-operative pain. The present study was aimed to evaluate the effects of oral clonidine on subarachnoid block characteristics, hemodynamic changes, sedation and respiratory efficiency in patients undergoing laparoscopic gynecological procedures.

PATIENTS AND METHODS

A total of 64 adult consenting females of American Society of Anesthesiologist physical status I and II were randomized double blindly into two groups of 32 patients each. Patients in the clonidine group received oral clonidine (100 μg) and patients of the control group received placebo capsule, 90 min before subarachnoid block with 0.5% hyperbaric bupivacaine (3.5 ml). The onset of sensory and motor block, maximum cephalic sensory level and regression times of sensory and motor blockade were assessed. Intra-operative hemodynamic changes, respiratory efficiency, shoulder pain and sedation score were recorded. The other side-effects, if any were noted and managed.

RESULTS

The onset of sensory blockade was earlier in patients of clonidine group with prolonged duration of analgesia (216.4 ± 23.3 min vs. 165.8 ± 37.2 min, P < 0.05), but no significant difference was observed on motor blockade between groups. The hemodynamic parameters and respiratory efficiency were maintained within physiological limits in patients of clonidine group and no patient experienced shoulder pain. The Ramsey sedation score was 2.96 ± 0.75. In the control group, 17 patients experienced shoulder pain, which was effectively managed with small doses of ketamine and 15 patients required midazolam for anxiety.

CONCLUSION

Premedication with oral clonidine (100 μg) has enhanced the onset and prolonged the duration of spinal analgesia, provided sedation with no respiratory depression. The hemodynamic parameters remained stabilized during the pneumoperitoneum.

Comparison of clonidine and midazolam premedication before endoscopic sinus surgery: results of clinical trial

OBJECTIVES

Premedication with clonidine has been found to reduce the bleeding during endoscopic sinus surgery (ESS), therefore lowering the risk of surgical complications. Premedication is an essential part of pre-surgical care and can potentially affect magnitude of systemic stress response to a surgical procedure. The aim of this study was to compare the efficacy of premedication with clonidine and midazolam in patients undergoing sinus surgery.

METHODS

Forty-four patients undergoing ESS for chronic sinusitis and polyp removal were enrolled and randomly assigned to receive either oral clonidine or midazolam as a premedication before receiving propofol/remifentanil total intravenous anesthesia. The effect of this premedication choice on anesthetic requirements, intraoperative hemodynamic profile, preoperative anxiety and sedation as well as postoperative pain and shivering were examined in each premedication group.

RESULTS

Total intraoperative remifentanil requirement was lower in the clonidine group as compared to the midazolam group 503.2±147.0 µg vs. 784.5±283.8 µg, respectively (P<0.001). There was no difference between groups in required induction dose of propofol, level of preoperative anxiety, level of sedation and postoperative shivering. Intraoperative systemic blood pressure and heart rate response had a more favorable profile in patients premedicated with clonidine. Postoperative pain assessed by visual analogue scale for pain was lower in the clonidine group compared with to the midazolam premedication group.

CONCLUSION

Premedication with clonidine provides better attenuation of hemodynamic response and reduction of intraoperative remifentanil requirements in patients undergoing ESS. Postoperative pain seems to be better controlled after clonidine premedication as well.

Urinary oxygen tension: a clinical window on the health of the renal medulla?

We describe the determinants of urinary oxygen tension (Po2) and the potential for use of urinary Po2 as a “physiological biomarker” of the risk of acute kidney injury (AKI) in hospital settings. We also identify knowledge gaps required for clinical translation of bedside monitoring of urinary Po2. Hypoxia in the renal medulla is a hallmark of AKI of diverse etiology. Urine in the collecting ducts would be expected to equilibrate with the tissue Po2 of the inner medulla. Accordingly, the Po2 of urine in the renal pelvis changes in response to stimuli that would be expected to alter oxygenation of the renal medulla. Oxygen exchange across the walls of the ureter and bladder will confound measurement of the Po2 of bladder urine. Nevertheless, the Po2 of bladder urine also changes in response to stimuli that would be expected to alter renal medullary oxygenation. If confounding influences can be understood, urinary bladder Po2 may provide prognostically useful information, including for prediction of AKI after cardiopulmonary bypass surgery. To translate bedside monitoring of urinary Po2 into the clinical setting, we require 1) a more detailed knowledge of the relationship between renal medullary oxygenation and the Po2 of pelvic urine under physiological and pathophysiological conditions; 2) a quantitative understanding of the impact of oxygen transport across the ureteric epithelium on urinary Po2 measured from the bladder; and 3) a simple, robust medical device that can be introduced into the bladder via a standard catheter to provide reliable and continuous measurement of urinary Po2.

The comparative evaluation of intravenous with intramuscular clonidine for suppression of hemodynamic changes in laparoscopic cholecystectomy

Background:

Clonidine diminishes stress response by reducing circulating catecholamines and hence increases perioperative circulatory stability in patients undergoing laparoscopic surgeries. The aim of this study was to compare intravenous (IV) clonidine (2 μg/kg) with intramuscular (IM) clonidine (2 μg/kg) for attenuation of stress response in laproscopic surgeries.

Methods:

Eighty adult patients classified as ASA physical status I or II, aged between 20 and 60 years undergoing elective cholecystectomy under general anesthesia were enrolled for a prospective, randomized, and double-blind controlled trial. They received either IV clonidine (2 μg/kg) 15 min prior to the scheduled surgery (Group I) or IM clonidine (2 μg/kg) 60-90 min prior to the scheduled surgery (Group II). Hemodynamic variables (Heart rate, systolic (SBP), diastolic (DBP), mean arterial pressure (MAP)), SpO₂ and EtCO₂ were recorded at specific times - baseline, prior to induction, 1 min after intubation, before CO₂, insufflation, after CO₂ insufflation at 1,5,10,20,30,45,60 min, after release of CO₂, at 1 and 10 minutes after extubation. Secondary outcomes included evaluation of adverse effect profile of the two groups.

Results:

No significant difference was observed in the HR throughout the intraoperative period in between the two groups (P>0.05). There was statistically significant difference in SBP between the two groups starting from 1 minute after induction till 1 min after extubation (P<0.05) but not in DBP except at 1 minute after intubation (P=0.042). Significant difference in MAP was noted at 1 minute after intubation (P=0.004) and then from 5 minutes after CO₂ insufflation to 1 minute after extubation (P<0.05). Incidence of adverse effects were higher in group II (P=0.02) especially incidence of hypertension requiring treatment (0.006).

Conclusion:

We conclude that under the conditions of this study, hemodynamic parameters (SBP, DBP and MAP) were better maintained in the IV as compared to the IM route that had significantly higher incidence of hypertension requiring treatment.

A prospective, randomized, double blind and placebo-control study comparing the additive effect of oral midazolam and clonidine for postoperative nausea and vomiting prophylaxis in granisetron premedicated patients undergoing laparoscopic cholecystecomy

Background:

Reduction of postoperative nausea and vomiting (PONV) continues to be a major challenge in perioperative care in spite of introduction of newer antiemetics with better efficacy and safety profiles. Therefore, we evaluated the additive effect of oral midazolam and clonidine for PONV prophylaxis in granisetron premedicated patients undergoing laparoscopic cholecystectomy.

Materials and Methods:

In a prospective, randomized fashion, 120 selected cases were randomized into three groups: I, II or III to receive a tablet of midazolam (15 mg, n = 36), clonidine (150 mcg, n = 40), or glucose as placebo (5 g, n = 44) orally, 1 h before anesthesia. Occurrence of PONV along with need for rescue antiemetic during the first postoperative day was compared between groups as a primary outcome.

Results:

Episodes of PONV reduced significantly in Group II (15%) as compared to group I and III (22.2%, 59%) at various time points during the period of observation (P = 0.002). Need for rescue antiemetic was significantly lower in group I (13.88%) and II (5%) as compared to group III (52.27%, P < 0.001).

Conclusion:

Oral clonidine is better adjuvant for PONV prophylaxis, as compared to midazolam, in granisetron premedicated patients undergoing laparoscopic cholecystectomy.

Hemodynamic stress response during laparoscopic cholecystectomy: Effect of two different doses of intravenous clonidine premedication

Background:

Clonidine has emerged as an attractive premedication desirable in laparoscopic surgery wherein significant hemodynamic stress response is seen. The minimum safe and effective dose of intravenous clonidine to attenuate the hemodynamic stress response during laparoscopic surgery has however not yet been determined.

Materials and Methods:

This prospective, randomized, double-blind controlled study was conducted on 90 adults of ASA physical status I and II, scheduled for laparoscopic cholecystectomy under general anesthesia. Patients were randomized to one of the three groups (n= 30). Group I received 100 ml of normal saline, while groups II and III received 1 μg/ kg and 2 μg/ kg of clonidine respectively, intravenous, in 100 ml of normal saline along. All patients received glycopyrrolate 0.004 mg/kg and tramadol 1.5 mg/kg intravenously, 30 min before induction. Hemodynamic variables (heart rate, systolic, diastolic, mean arterial pressure), SpO2, and sedation score were recorded at specific timings. MAP above 20% from baseline was considered significant and treated with nitroglycerine.

Results:

In group I, there was a significant increase in hemodynamic variables during intubation pneumoperitoneum and extubation (P<0.001). Clonidine given 1 μg/kg intravenous attenuated hemodynamic stress response to pneumoperitoneum (P<0.05), but not that associated with intubation and extubation. Clonidine 2 μg/kg intravenous prevented hemodynamic stress response to pneumoperitoneum and that associated with intubation and extubation (P<0.05). As against 14 and 2 patients in groups I and II respectively, no patient required nitroglycerine infusion in group III.

Conclusions:

Clonidine, 2 μg/ kg intravenously, 30 min before induction is safe and effective in preventing the hemodynamic stress response during laparoscopic cholecystectomy.

Oral premedication with pregabalin or clonidine for hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy: A comparative evaluation

BACKGROUND

Hemodynamic responses of laryngoscopy and laparoscopy should be attenuated by the appropriate premedication, smooth induction, and rapid intubation. The present study evaluated the clinical efficacy of oral premedication with pregabalin or clonidine for hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy.

METHODS

A total of 180 healthy adult consented patients aged 35 to 52 years with American Society of Anesthesiologist (ASA) physical status I and II of both gender, who met the inclusion criteria for elective laparoscopic cholecystectomy, were randomized to receive placebo Group I, pregabalin (150 mg) Group II, or clonidine (200 μg) Group III, given 75 to 90 minutes before surgery as oral premedication. All groups were compared for preoperative sedation and anxiety level along with changes of heart rate and mean arterial pressure prior to premedication, before induction, after laryngoscopy, pneumoperitoneum, release of carbon dioxide, and extubation. Intraoperative analgesic drug requirement and any postoperative complications were also recorded.

RESULTS

Pregabalin and clonidine proved to have sedative and anxiolytic effects as oral premedicants and decreased the need of intraoperative analgesic drug requirement. Clonidine was superior to pregabalin for attenuation of the hemodynamic responses to laryngoscopy and laparoscopy, but it increased the incidence of intra-and postoperative bradycardia. No significant differences in the parameters of recovery were observed between the groups. None of the premedicated patient has suffered from any postoperative side effects.

CONCLUSION

Oral premedication with pregabalin 150 mg or clonidine 200 μg causes sedation and anxiolysis with hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy, without prolongation of recovery time and side effects.

The effects of high-frequency jet ventilation (HFJV) on pneumoperitoneum-induced cardiovascular changes during laparoscopic surgery

BACKGROUND

Standard mechanical ventilation may cause adverse cardiovascular effects in addition to those already related to positive-pressure pneumoperitoneum (PP) during laparoscopic surgery. High-frequency jet ventilation (HFJV) is associated with much less airway pressure, with potentially less influence on venous return, thus potentially it may reduce those effects. The aim of this study was to evaluate the benefits of HFJV to reduce the adverse cardiovascular effects during laparoscopic cholecystectomy.

METHODS

We conducted a randomized prospective trial, comparing 12 patients undergoing elective laparoscopic cholecystectomy under conventional mechanical ventilation (control) with 13 similar subjects under HFJV (study). Both groups were categorized as ASA I-II and underwent total intravenous anesthesia. Cardiac functionality was continuously evaluated by analysis of arterial pressure wave changes (Edwards Flo-Trac sensor and Vigileo monitor).

RESULTS

There was no significant difference between both groups regarding age, gender, BMI, and general medical condition, as well as hemodynamic stability and blood gases throughout surgery. A significant reduction in cardiac output was noted in the control group under PP during the initiation of anti-Trendelenburg position (from 5.6 to 5.0 l/min, P = 0.049). A reciprocal change was observed regarding stroke volume. Such changes were not noticed under HFJV. Total peripheral resistance was significantly increased during PP, and heart rate was not significantly affected throughout surgery in both groups. Unexpectedly, we did not observe marked adverse hemodynamic changes in the control group during PP without position adjustment.

CONCLUSIONS

The use of HFJV in upper laparoscopic surgery can impede the adverse cardiovascular changes that usually occur during induction of PP. We also suggest that the use of total intravenous anesthesia (as used in our study) may also lessen the cardiovascular impairment during PP.

Oral clonidine pre-treatment and diazepam/meperidine sedation

Clonidine has recently been used as a pre-operative medication and sedative/anxiolytic drug. Its extended duration of action makes it suitable for longer procedures. In this randomized, crossover, placebo-controlled clinical trial, we characterized the effects of oral clonidine pre-treatment on intravenous diazepam/meperidine sedation using the bi-spectral index (BIS) in 13 participants. Clonidine significantly increased the numbers of BIS-depressed readings and percent memory loss during sedation, while reducing total diazepam and post-operative analgesic dosages by 44% and 55%, respectively. Systolic, diastolic, and mean arterial blood pressures, as well as pulse rates, were reduced. Respiratory rate, oxygen saturation, end-tidal CO(2), and recovery from sedation were unchanged. Participants, surgeons, and sedationists preferred clonidine over the placebo. Clonidine pre-treatment increased and prolonged sedation and amnesia and stabilized vital signs while significantly decreasing diazepam and post-operative analgesic usage. These results suggest that pre-operative clonidine administration could be a useful supplement to intravenous sedation for dental procedures of long duration.

Systematic evaluation of different approaches for minimizing hemodynamic changes during pneumoperitoneum

BACKGROUND

Capnoperitoneum (CP) compromises hemodynamic function during laparoscopy. Three therapeutic concepts were evaluated with an aim to minimize the hemodynamic reaction to CP: First, a controlled increase of intrathoracic blood volume (ITBV) by intravenous fluids; second, partially reduced sympathetic activity by the beta1-blocker esmolol; and third, a decrease in mean arterial pressure (MAP) by the vasodilator sodium nitroprusside.

METHODS

For this study, 43 pigs were assigned to treatment with fluid and sodium nitroprusside (group A) or with esmolol (group B). In both groups, the pigs were assigned to head-up, head-down, or supine position, resulting in three different subgroups. Invasive hemodynamic monitoring was established including left heart catheter and cardiac oxygen lung water determination (COLD) measurements. Measurements were documented before CP with the animals in supine position, after induction of a 14-mmHg CP with the animals in each body position, after a 10% reduction in MAP by vasodilation, and after an increase in ITBV of about 30% by infusion of 6% hydroxyethylstarch solution.

RESULTS

Increasing ITBV improved hemodynamic function in all body positions during CP. Esmolol reduced cardiac output and myocardial contractility. Sodium nitroprusside did not improve hemodynamic function in any body position.

CONCLUSIONS

Optimizing volume load is effective for minimizing hemodynamic changes during CP in the head-up and in head-down positions. In general, beta(1)-blockers cannot be recommended because they might additionally compromise myocardial contractility and suppress compensatory reaction of the sympathetic nerve system. Vasodilation has not improved hemodynamic parameters during CP.

Oral clonidine pretreatment prior to venous cannulation

Clonidine is a preferential alpha-2 agonist drug that has been used for over 35 years to treat hypertension. Recently, it has also been used as a preoperative medication and as a sedative/anxiolytic drug. This randomized, double-blind, placebo-controlled crossover clinical trial characterized the effects of oral clonidine pretreatment on intravenous catheter placement in 13 patients. Parameters measured included the bispectral index (BIS), Observer's Assessment of Alertness/Sedation Scale (OAA/S), frontal temporal electromyogram (EMG), 30-Second Blink Count (Blink), Digit Symbol Substitution Test (DSST), State Anxiety Inventory (SAI), fingertip versus forearm skin temperatures, and multiple questionnaires. Oral clonidine significantly decreased SAI scores, OAA/S, EMG, and Blink, but did not cause statistically significant BIS or DSST reductions. Subjects preferred oral clonidine pretreatment prior to venipuncture compared to placebo. Questionnaires also indicated that clonidine provided minimal sedation, considerable anxiolysis, and some analgesia. Fingertip versus forearm skin temperature differentials were decreased. Reduced fingertip versus forearm temperature differentials suggest increased peripheral cutaneous blood flow prior to venous cannulation. Oral clonidine pretreatment not only helped control patient anxiety and pain but also provided cardiovascular stability.