Labetalol as a hypotensive agent for middle ear microsurgery

Evaluation of the perioperative effects of dexmedetomidine on tympanoplasty operations

PURPOSE

This randomized double-blind study aimed to evaluate the effects of dexmedetomidine on hemodynamic parameters and the quality of surgery and recovery criteria in tympanoplasty operations.

MATERIALS AND METHODS

A total of 75 patients 18-55 years undergoing tympanoplasty, who were graded as American Society of Anesthesiologists physical status I-II, were randomly divided into three groups. Group 1 included patients receiving remifentanil alone, Group 2 included patients receiving dexmedetomidine + remifentanil and Group 3 included patients receiving dexmedetomidine + ½ remifentanil. Anesthesia was induced with propofol and cisatracurium. For maintenance of anesthesia, a mixture of 2-2.5% sevoflurane, 40-60% oxygen/air was used. The groups were compared in terms of hemodynamic parameters, surgical area, recovery criteria, modified Aldrete, pain scores, additional analgesic requirements and adverse effects.

RESULTS

Mean arterial pressure and heart rate values of Group 1 were higher at the time of intubation, incision, spontaneous breathing and extubation compared to Group 2 and Group 3. Surgical field satisfaction was higher in Group 2 and Group 3 than Group 1. Spontaneous breathing, eye opening and verbal cooperation times were shorter in Group 3 compared to Group 2. Eye opening and verbal cooperation times were longer in Group 2 compared to Group 1. The 30-minute modified Aldrete scores was higher in Group 3 compared to Group 1. There was no difference between the groups in terms of postoperative pain and adverse effects.

CONCLUSION

The use of dexmedetomidine during tympanoplasty operations may provide better hemodynamic control and surgical view, may provide faster recovery and may reduce remifentanil consumption.

The Effect of the Total Intravenous Anesthesia Compared with Inhalational Anesthesia on the Surgical Field during Endoscopic Sinus Surgery

Background

Bleeding during endoscopic sinus surgery (ESS) may increase complications and negatively effect the surgery and its outcome. The aim of this study was to compare the surgical field in patients in whom total intravenous anesthesia (TIVA) is used as opposed to inhalation anesthesia. A prospective randomized controlled trial was performed.

Methods

Fifty-six patients undergoing ESS were randomly assigned to receive either inhaled sevoflurane with incremental doses offentanyl (n = 28) or TIVA via a propofol and remifentanil infusion (n = 28) for their general anesthesia. The surgical field was graded every 15 minutes using a validated scoring system.

Results

The two groups were matched for surgical procedure and computed tomography scores. Patients in the TIVA group were found to have a significantly lower surgical grade score than in the sevoflurane group (p < 0.001). Surgical grade score increased with time in both groups. Mean arterial pressure and pulse were found to influence the surgical field independently (p = 0.003 and p = 0.036 respectively). Mean surgical field grade scores were higher in the patients with allergic fungal sinusitis and nasal polyposis as opposed to chronic rhinosinusitis without polyps or fungus. Lund-Mackay computed tomography scores were found to correlate positively with surgical grade (Spearman rank correlation, p = 0.001).

Conclusion

In patients undergoing ESS, TIVA results in a better surgical field than inhalational anesthesia.

An Evaluation of Effect of Pterygopalatine Fossa Injection with Local Anesthetic and Adrenalin in the Control of Nasal Bleeding during Endoscopic Sinus Surgery

Background

The aim of this study was to determine the effect of pterygopalatine fossa infiltration with lidocaine and adrenalin on bleeding in the surgical field during endoscopic sinus surgery.

Methods

A prospective blind randomized controlled trial was performed. Fifty-five patients were randomized to receive a unilateral transoral infiltration of the pterygopalatine fossa with 2 mL of 2% lidocaine and 1:80,000 adrenalin. The operating surgeon was blinded as to which side had been infiltrated at the start of surgery. The surgical field was graded on a previously validated surgical field grading scale every 15 minutes with the side being operated on alternated every 30 minutes. The pulse, mean arterial blood pressure, and end-tidal CO2 concentration were monitored with each surgical field observation.

Results

At each individual time point from 30 minutes to 3.5 hours there was a significant difference in surgical grade between injected and noninjected sides in favor of the injected side (p = 0.01). The difference between surgical grades averaged across all time points was slight but significant. The injected side had an overall mean of 2.59 (SE, 0.22) compared with 2.99 (SE, 0.23) for the noninjected side. Heart rate also was found to correlate independently to surgical grade.

Conclusion

Injection of the pterygopalatine fossa resulted in an improved surgical field during endoscopic sinus surgery.

Evaluation of the efficacy of desflurane with or without labetalol for hypotensive anesthesia in middle ear microsurgery

Background and Aims:

Hypotensive anesthesia technique is used to reduce intraoperative bleeding and to improve the visibility of the operative field. The aim was to evaluate the efficacy of desflurane with and without labetalol for producing hypotensive anesthesia.

Material and Methods:

Sixty adult patients undergoing elective middle ear surgery were administered general anesthesia and randomly divided into two groups – Group D and Group L. The target mean arterial pressure (MAP) was 55–65 mmHg during hypotensive period. Group D patients received an increasing concentration of desflurane alone. Group L patients received 3% desflurane plus labetalol (loading dose 0.3 mg/kg intravenously, followed by 10 mg increments every 10 min). Student's t-test and paired t-test were used to compare the hemodynamic parameters. Visibility of the operative field, anesthetic and rescue drug requirement, partial pressure of oxygen in arterial blood, time taken for induction and reversal of hypotension and recovery characteristics were noted.

Results:

Target MAP was achieved in both the groups. Group D was associated with a higher mean heart rate compared with Group L (77.3 ± 11.0/min vs. 70.5 ± 2.5/min, respectively; P < 0.001) during the hypotensive period, along with a higher requirement for desflurane (P = 0.000) and metoprolol (P = 0.01). Time taken to achieve target MAP was lesser in Group L compared with Group D (33.7 ± 7.1 vs. 39.8 ± 6.2 min, respectively; P = 0.000). Time taken to return to baseline MAP was faster in Group D (P = 0.03). Emergence time was longer with desflurane alone (P = 0.000) resulting in greater sedation (P = 0.000) in the immediate postoperative period.

Conclusion:

Although desflurane is effective for inducing deliberate hypotension in middle ear microsurgery, the combination of desflurane with labetalol is associated with decreased requirement of desflurane, absence of reflex tachycardia, faster induction of hypotension, faster recovery from anesthesia, and less postoperative sedation.

Is Pterygopalatine Fossa Injection with Adrenaline an Effective Technique for Better Surgical Field in Fess?

Functional endoscopic sinus surgery (FESS) is one of most common surgeries in otorhinolaryngology practice. It is done in the narrow confines of the nasal cavity. Bleeding into the surgical field is a major problem faced by endoscopic surgeons. To assess the effectiveness of pterygopalatine fossa infiltration with lignocaine and adrenaline in controlling surgical field bleeding during endoscopic sinus surgery. A randomized blinded study was done among 68 patients who underwent FESS. Infiltration with 2% lignocaine with 1:80,000 adrenaline was given only on one side and the surgeon was blinded as to which side was infiltrated and he was asked to assess the surgical field using a standard scale. There was statistical significant improvement in surgical field on the infiltrated side (p = 0.001) with almost 25-30% improvement in surgical field on the infiltrated side. The surgical field bleeding also varied with the blood pressure with a positive correlation. There were no complications associated with the procedure. Pterygopalatine fossa infiltration with lignocaine and adrenaline is an effective technique in reducing surgical field bleeding during FESS. It can be combined with nasal decongestion or hypotensive anaesthesia for an optimum surgical field.

Controlled hypotension with desflurane combined with esmolol or dexmedetomidine during tympanoplasty in adults: A double-blind, randomized, controlled trial

BACKGROUND

Controlled hypotension is a technique that is used to limit intraoperative blood loss to provide the best possible surgical field during surgery.

OBJECTIVE

The aim of this double-blind, randomized, controlled study was to compare the effects of desflurane combined with esmolol or dexmedetomidine on the amount of blood in the surgical field, recovery time, and tolerability in adult patients undergoing tympanoplasty.

METHODS

Turkish patients aged 18 to 60 years, classified as American Society of Anesthesiologists physical status I or II, who were scheduled for tympanoplasty were randomly divided into 2 groups: the esmolol group or the dexmedetomidine group. After the anesthesia induction in the esmolol group, a loading dose of esmolol was infused intravenously over 1 minute at 1 mg/kg, followed by a maintenance rate of 0.4 to 0.8 mg/ kg/h. In the dexmedetomidine group, a loading dose of dexmedetomidine was infused intravenously over 10 minutes at a rate of 1 μg/kg, followed by a maintenance rate of 0.4 to 0.8 μg/kg/h. The infusion rates were then titrated to maintain mean arterial pressure (MAP) of 65 to 75 mm Hg. General anesthesia was maintained with desflurane 4% to 6%. Heart rate (HR) and MAP were recorded during anesthesia. The following 6-point scale was used to assess the amount of bleeding in the operative field: 0 = no bleeding, a virtually bloodless field; 1 = bleeding that was so mild that it was not a surgical nuisance; 2 = moderate bleeding that was a nuisance but did not interfere with accurate dissection; 3 = moderate bleeding that moderately compromised surgical dissection; 4 = bleeding that was heavy but controllable and that significantly interfered with surgical dissection; and 5 = massive bleeding that was uncontrollable and made dissection impossible. Scores ≤2 were considered to be optimal surgical conditions. The sedation score was determined at 15, 30, and 60 minutes after tracheal extubation using the following scale: 1 = anxious, agitated, or restless; 2 = cooperative, oriented, and tranquil; 3 = responsive to commands; 4 = asleep, but with brisk response to light, glabellar tap, or loud auditory stimulus; 5 = asleep, sluggish response to glabellar tap or auditory stimulus; and 6 = asleep, no response. Time to extubation and to total recovery from anesthesia (Aldrete score ≥9 on a scale of 0-10), adverse effects (eg, intraoperative hypotension [blood pressure <65 mm Hg], bradycardia [HR <50 beats/min]), intraoperative fentanyl consumption, and postoperative nausea and vomiting were recorded. Arterial blood gas analysis and kidney and liver function tests were conducted. All patients were evaluated by the same attending surgeon and anesthesiologist, both of whom were blinded to the administered study drugs.

RESULTS

Fifty-two consecutive white patients undergoing tympanoplasty were identified. Two patients had to be excluded because of hypertension and 2 refused to participate. Forty-eight patients were equally randomized to either the esmolol group (n = 24 [16 women, 8 men]; mean [SD] age, 38.4 [10.5] years) or the dexmedetomi-dine group (n = 24 [17 women, 7 men]; mean age, 35.5 [14.7] years). Sedation scores were not collected for 1 patient in the esmolol group; therefore, analysis was conducted for 23 patients. The median (range) of the scores for the amount of blood in the surgical field in the esmolol and dexmedetomidine groups was 1 (0-3) and 1 (0-2), respectively (P = NS). Mean intraoperative fentanyl consumption in the esmolol group was significantly higher than in the dexmedetomidine group (50.0 [3.0] vs 25.0 [2.5] μg/min; P = 0.002). In the esmolol group, the mean times to extubation and to recovery from anesthesia were significantly shorter than those of the dexmedetomidine group (7.0 [1.4] vs 9.1 [1.9] minutes, respectively; 5.9 [2.1] vs 7.9 [2.3] minutes; both, P = 0.001). The mean sedation scores were significantly lower in the esmolol group (n = 23, because of intent-to-treat analysis) compared with the dexmedetomidine group at 15 minutes (2.5 [0.6] vs 3.6 [0.5]; P = 0.001) and 30 minutes (2.6 [0.6] vs 3.3 [0.6]; P = 0.001) postoperatively. No significant differences were found between the study groups in regard to blood urea nitrogen or creatinine concentration, aspartate aminotransferase or alanine aminotransferase activities, pH, partial pressure of carbon dioxide, or bicarbonate, before or after the operation.

CONCLUSIONS

Both esmolol and dexmedetomidine, combined with desflurane, provided an effective and well-tolerated method of achieving controlled hypotension to limit the amount of blood in the surgical field in these adult patients undergoing tympanoplasty. Esmolol was associated with significantly shorter extubation and recovery times and significantly less postoperative sedation compared with dexmedetomidine.

Comparative induction of controlled circulation by magnesium and remifentanil in spine surgery

AIM: To evaluate the efficacy of magnesium sulfate (MGS) in comparison with remifentanil for induction of relative hypotension in posterior fusion of spine (PSF).

METHODS: In this randomized clinical trial, 40 patients with the American Society of Anesthesiologists I and II physical status undergoing lumbar PSF were randomized to receive remifentanil (REM) 0.15 μg/kg or MGS 50 mg/kg for controlled hypotension. The administering anesthesiologist was blinded to the medication. Continuous infusion was maintained at a fixed volume rate to deliver precalculated doses of either study drugs. All other aspects of anesthesia and surgery were similar in the two groups. The target mean arterial pressure (MAP) range used in this study was 60-70 mmHg. In the course of surgery, the hemodynamic variables, volume of blood loss, urine output, fluid intake and surgeon’s satisfaction were recorded. Data was analyzed with SPSS version 13.0 and P values less than 0.05 were considered significant.

RESULTS: Twenty patients in the MGS group and 19 patients in the REM group were studied. There was no difference between the two groups in the hemodynamic variables, blood loss, urine output, fluid requirement and surgeon’s satisfaction for exposure. The target MAP was achieved in 75% of Mg and 58% of remifentanil groups. Although a higher number of patients in the REM group required nitroglycerin (42.1%) to reach the target MAP than those in the MGS group (25%), this difference was not statistically significant (P = 0.32).

CONCLUSION: Our findings showed that in patients undergoing lumbar PSF surgery, remifentanil and MGS have a similar hypotensive effect and comparable amount of blood loss without any significant adverse effects.

General anaesthetic considerations for haemostasis in orbital surgery

Orbital surgery is often conducted in areas with limited exposure where vital structures are tightly crowded together. A bloodless field is paramount in orbital surgery for the proper identification of normal and pathologic tissue and even minimal bleeding can obscure the surgical field, making surgery more difficult and increasing the risk of complications. Surgery for highly vascular orbital lesions is an additional situation where maintaining an adequate surgical field is often challenging but paramount. The role of the anaesthetist in controlling surgical blood loss has been increasingly recognized in the last few decades. Various techniques including hypotensive anaesthesia have been described, but the control of intraoperative bleeding does not rely on a single particular technique, but a series of well-designed interventions that result in optimal conditions. An understanding of the anaesthetic considerations pertinent to haemostasis is invaluable for oculoplastic surgeons. Additionally, with the growing use of endonasal approaches to medial wall decompression and accessing the medial orbit, it has become increasingly important that orbital surgeons understand the anaesthetic requirements of their colleagues in other disciplines.

Intravenous esmolol infusion improves surgical fields during sevoflurane-anesthetized endoscopic sinus surgery: a double-blind, randomized, placebo-controlled trial

BACKGROUND

There is increasing evidence to support the use of anesthetics to affect operative fields during endoscopic sinus surgery and thus the speed, thoroughness, and safety of the surgery itself. Previous research has suggested preoperative beta-blockers improve surgical fields (SFs); our study is novel in showing the impact of a beta-blocker infusion on SFs during sinus surgery.

METHODS

A prospective, randomized, double-blind, placebo-controlled trial was conducted in 40 patients. Patients undergoing endoscopic sinus surgery for chronic rhinosinusitis received a constant infusion of i.v. esmolol or saline in addition to a standard inhaled anesthetic protocol. At regular 15-minutes intervals, the quality of SF, heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were assessed. Total blood loss was also recorded.

RESULTS

Average vital sign parameters (HR/SBP/DBP) were significantly lower in the esmolol group (69.1/90.2/55.1 versus 77.2/99.5/63.5; p < 0.01). The esmolol infusion improved SFs relative to control (2.3 versus 2.6; p = 0.045). Esmolol infusion resulted in good SFs (grades 1 and 2) more often than poor fields (grades 3 and 4); on the contrary, the control group showed more poor than good SFs (chi-square; p = 0.04). A correlation between increasing HR and worsening SFs was identified (r = 0.259; p = 0.002). The control group had significantly higher average blood loss (1.3 versus 0.8 mL/min; p = 0.037).

CONCLUSION

Esmolol-induced relative hypotension and bradycardia during endoscopic sinus surgery achieves significantly improved SFs relative to saline control.

Effects of premedication with metoprolol on bleeding and induced hypotension in nasal surgery

BACKGROUND

One of the major problems in surgery is intraoperative bleeding which reduces visibility in the operative field. An important task for an anesthetist during head and neck surgery is to improve intraoperative visibility.

OBJECTIVES

The purpose of this study was to compare the amount of bleeding using different doses of oral metoprolol during three common types of nasal operation; rhinoplasty, septoplasty and functional endoscopic sinus surgery, as this is one of the complications during head and neck surgery.

PATIENTS AND METHODS

In a randomized, controlled, open clinical trial, 88 patients who were candidates for nasal operations were studied. Patients entering the study were divided into four groups and randomly assigned to receive 50 mg metoprolol a night before the operation, 50 mg metoprolol on the day of operation, 50 mg metoprolol on the night and on the day of operation, or a placebo. Following the patient's preparation on the operating table and after intubation, systolic and diastolic blood pressures were measured in a non-invasive oscillometric way, and their pulse rate was recorded simultaneously. All the data were recorded during the surgery as well. Bleeding was measured by the quality scale proposed by Formme and Boezaart.

RESULTS

There was a statistical significance between using metoprolol and the amount of intraoperative bleeding. All patients who received metoprolol the night before surgery and on the day of surgery had slight bleeding during the surgery. In addition, there was a statistical significance between patients' agitation levels and the time they received metoprolol.

CONCLUSIONS

Decreases in both systolic blood pressure and heart rate to less than 60 beats per minute reduces intraoperative bleeding. These rates can be achieved by using beta-blocker drugs. In this study, using a double-dose of metoprolol significantly reduced intraoperative bleeding and improved the quality of the operative field. It also reduced patients' agitation in the recovery room.

Risks and benefits of deliberate hypotension in anaesthesia: a systematic review

This systematic review was performed to investigate and review the evidence on the risks and benefits of hypotensive anaesthesia in order to answer the following question: 'Should deliberate hypotension be used routinely during orthognathic surgery?' An electronic search on MEDLINE and the Cochrane Library database was carried out for all relevant articles using specific search keywords. All articles were classified by their levels of evidence. Studies with highest level of evidence and rated to have the lowest risk of bias were reviewed. Regarding the benefits of hypotensive anaesthesia, three studies reported significant decrease of blood loss in patients receiving hypotensive anaesthesia. Two studies reported a significant decrease in transfusion rate. Two studies demonstrated improved surgical field and significant reduction in operation time. In terms of risk, no significant changes in cerebral, cardiovascular, renal and hepatic functions in patients receiving hypotensive anaesthesia compared to control were reported. In conclusion, hypotensive anaesthesia appears to be effective in reducing blood loss. Serious consequences due to organ hypoperfusion are uncommon. Hypotensive anaesthesia can be justified as a routine procedure for orthognathic surgery especially bimaxillary osteotomy. Patient selection and appropriate monitoring are mandatory for this technique to be carried out safely.

Hypotensive anaesthesia with remifentanil combined with desflurane or isoflurane in tympanoplasty or endoscopic sinus surgery: a randomised, controlled trial

Objective:

To compare the effect of remifentanil combined with desflurane or isoflurane on the quality of the operative field and surgical conditions, blood loss, and recovery during tympanoplasty or endoscopic sinus surgery.

Design:

Randomised, double-blinded clinical study.

Subjects:

Sixty-four patients were scheduled for elective tympanoplasty or endoscopic sinus surgery. The patients were randomly divided into two groups: desflurane or isoflurane. After anaesthesia induction, all patients received a continuous remifentanil infusion of 0.2–0.5 µg/kg/min until a mean arterial pressure of 65–75 mmHg was achieved. Heart rate and mean arterial pressure were recorded throughout anaesthesia. Blood loss was measured at the end of surgery. Achievement of a bloodless operative field was rated on a 100 mm visual analogue scale. Following completion of surgery, the time to extubation and to achievement of an Aldrete score of nine or more was recorded.

Results:

Sixty-three patients were evaluated. The total dose of remifentanil and the total blood loss were similar in both groups (p > 0.05). Time to extubation and to an Aldrete score of nine or more for the desflurane group was significantly less than for the isoflurane group (p < 0.05). No differences were found in the extent of achievement of a bloodless operative field, as assessed via visual analogue scale, comparing the study groups (p > 0.05).

Conclusion:

Although desflurane and isoflurane both enabled good surgical conditions (in terms of quality of operative field) and convenient induction of hypotension for tympanoplasty and endoscopic sinus surgery, the recovery characteristics of desflurane were better than those of isoflurane. Therefore, desflurane may be preferable to isoflurane in such circumstances.

The effect of beta-blocker premedication on the surgical field during endoscopic sinus surgery

OBJECTIVES/HYPOTHESIS

A number of previous studies have tried to assess the effects of hypotension on the surgical field during endoscopic sinus surgery. These studies have been limited by inadequate sample sizes, lack of a control group, and limited data collection. The aim of the present study was to determine whether the routine use of beta-blockers as a pre-medication could improve the operative field in endoscopic sinus surgery.

STUDY DESIGN

A prospective, randomized, double-blinded, placebo-controlled trial.

METHODS

Eighty patients undergoing endoscopic sinus surgery who fit the inclusion and exclusion criteria were randomly assigned to receive either a beta-blocker, Metoprolol (group 1), or a placebo tablet (group 2) 30 minutes before surgery. A standard anesthetic protocol was followed. At the commencement of surgery and at regular 15-minute intervals the surgical field, blood loss, heart rate, blood pressure, and isoflurane concentration were assessed.

RESULTS

There was a significant difference in overall mean heart rate between the placebo and beta-blocker groups (P <.0001). In the entire group, surgical grade correlated with heart rate (r = 0.36, P <.05) but not with mean arterial blood pressure. Mean surgical grade was similar between the placebo and beta-blocker groups, but early in the study a significantly better surgical field was recorded in the beta-blocker group (P <.001). Surgical grade was significantly better in those with a mean heart rate of less than 60 beats per minute (P <.02).

CONCLUSION

Although "optimum" conditions were present in the patients receiving beta-blocker, the authors thought that the grading system was not discriminating enough to demonstrate a significant difference between the groups. The crucial finding in the study was the correlation between heart rate and surgical grade in the entire group. During endoscopic sinus surgery surgery, anesthetic manipulations should be directed at maintaining a low heart rate.

Remifentanil induces consistent and sustained controlled hypotension in children during middle ear surgery

PURPOSE

To determine in children whether remifentanil combined with sevoflurane, could induce controlled hypotension, reduce middle ear blood flow (MEBF) measured by laser-Doppler, and provide a satisfactory operative field.

METHODS

Forty children undergoing middle ear surgery and anesthetized with sevoflurane were randomly assigned to receive either 1 micro g x kg(-1) remifentanil iv followed by a continuous infusion of 0.2 to 0.5 micro g x kg(-1) x min(-1) or 0.25 micro g x kg(-1) x min(-1) nitroprusside iv and alfentanil iv (n = 20 in each group).

RESULTS

Controlled hypotension was achieved at the target mean arterial pressure (MAP) of 50 mmHg (P < 0.01) within 121 +/- 21 and 62 +/- 9 sec for remifentanil and nitroprusside respectively. MEBF decreased by 22 +/- 4 and 20 +/- 6% and preceded the decrease in MAP within 20 +/- 7 and 10 +/- 3 sec for remifentanil and nitroprusside respectively. Remifentanil, and nitroprusside decreased MEBF autoregulation (0.41 +/- 0.2 and 0.37 +/- 0.3 respectively). Controlled hypotension was sustained in both groups throughout surgery, and the surgical field rating was good. Nitroprusside increased PaCO(2) slightly, and there were no postoperative circulatory, neurological or metabolic complications in any of the groups.

CONCLUSION

Remifentanil combined with sevoflurane in children enabled controlled hypotension, reduced MEBF and provided good surgical conditions for middle ear surgery with no need for additional use of a specific hypotensive agent.

Remifentanil and controlled hypotension; comparison with nitroprusside or esmolol during tympanoplasty

PURPOSE

To determine whether remifentanil, combined with propofol, could induce controlled hypotension, reduce middle ear blood flow (MEBF) measured by laser-Doppler flowmetry, provide a "dry" operative field, and could be compared with nitroprusside or esmolol combined with alfentanil and propofol.

METHODS

Thirty patients undergoing tympanoplasty and anesthetized with 2.5 mg x kg(-1) propofol iv followed by a constant infusion of 120 microg x kg(-1) x min(-1), were randomly assigned in three groups to receive either 1 microg x kg(-1) remifentanil iv followed by a continuous infusion of 0.25 to 0.50 microg x kg(-1) x min(-1), or nitroprusside iv, or esmolol iv combined for the latter two groups with alfentanil iv.

RESULTS

Controlled hypotension was achieved at the target pressure of 80 mmHg within 107 +/- 16, 69 +/- 4.4, 53.3 +/- 4.4 sec for remifentanil, nitroprusside and esmolol respectively. MEBF decreased by 24 +/- 0.3, 22 +/- 3.3, 37 +/- 3% and preceded the decrease in SABP, within 30 +/- 6.1, 11.2 +/- 3.1, 15 +/- 2.8 sec for remifentanil, nitroprusside and esmolol respectively. Remifentanil, and nitroprusside decreased MEBF autoregulation less than esmolol (0.36 +/- 0.1, 0.19 +/- 0.2, -0.5 +/- 0.2). Controlled hypotension was sustained in all three groups throughout surgery, and the surgical field rating decreased in a range of 80% in all three groups. Nitroprusside decreased pH and increased PaCO2. There were no postoperative complications in any of the groups.

CONCLUSIONS

Remifentanil combined with propofol enabled controlled hypotension, reduced middle ear blood flow and provided good surgical conditions for tympanoplasty with no need for additional use of a potent hypotensive agent.

Labetalol attenuates the negative effects of deliberate hypotension induced by isoflurane

The effect of labetalol on deliberate hypotension was studied in 24 adult patients undergoing middle-ear surgery. Hypotension was induced in Group I (12 patients) with isoflurane 3.0 vol% in inspiratory gas, and in Group II (12 patients) with labetalol 0.5 mg.kg-1 i.v., in addition to isoflurane. The induction time of hypotension was 4.9 +/- 1.0 (s.e.mean) min in Group I, and 1.8 +/- 0.2 min in Group II (P less than 0.01). The mean isoflurane concentration in inspiratory gas for the maintenance of hypotension was 1.4 +/- 0.2 vol% in Group I, and 0.7 +/- 0.1 vol% in Group II (P less than 0.01). There were no differences in urine flow rates (UF) between the groups during any phase, though UF decreased in Group I from the prehypotensive value 0.58 +/- 0.12 ml.min-1 to 0.07 +/- 0.02 ml.min-1 during hypotension (P less than 0.01) and increased to 1.28 +/- 0.17 ml.min-1 after anaesthesia (P less than 0.05). UF in Group II were 0.56 +/- 0.17, 0.25 +/- 0.10 and 0.56 +/- 0.06 ml.min-1, respectively. Creatinine clearances per 1.73 m2 body surface area (CCreat) in Group I were 78 +/- 14 ml.min-1, and in Group II 78 +/- 11 ml.min-1 before hypotension. During hypotension, CCreat were lower in Group I (8 +/- 1 ml.min-1) than in Group II (33 +/- 8 ml.min-1) (P less than 0.01). After anaesthesia, there was no difference in CCreat between the groups (Group I: 110 +/- 17 ml.min-1 and Group II: 120 +/- 17 ml.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Deliberate hypotension induced by labetalol with halothane, enflurane or isoflurane for middle-ear surgery

The feasibility of using labetalol, an alpha- and beta-adrenergic blocking agent, as a hypotensive agent in combination with inhalation anaesthetics (halothane, enflurane or isoflurane) was studied in 23 adult patients undergoing middle-ear surgery. The mean arterial pressure was decreased from 86 +/- 5 (s.e. mean) mmHg to 52 +/- 1 mmHg (11.5 +/- 0.7 to 6.9 +/- 0.1 kPa) for 98 +/- 10 min in the halothane (H) group, from 79 +/- 5 to 53 +/- 1 mmHg (10.5 +/- 0.7 to 7.1 +/- 0.1 kPa) for 129 +/- 11 min in the enflurane (E) group, and from 80 +/- 4 to 49 +/- 1 mmHg (10.7 +/- 0.5 to 6.5 +/- 0.1 kPa) for 135 +/- 15 min in the isoflurane (I) group. The mean H concentration during hypotension in the inspiratory gas was 0.7 +/- 0.1 vol%, the mean E concentration 1.6 +/- 0.2 vol%, and the mean I concentration 1.0 +/- 0.1 vol%. In addition, the patients received fentanyl and d-tubocurarine. The initial dose of labetalol for lowering blood pressure was similar, 0.52-0.59 mg/kg, in all the groups. During hypotension, the heart rate was stable without tachy- or bradycardia. The operating conditions regarding bleeding were estimated in a double-blind manner, and did not differ significantly between the groups. During hypotension, the serum creatinine concentration rose significantly in all groups from the values before hypotension and returned postoperatively to the initial level in the other groups, except the isoflurane group. After hypotension there was no rebound phenomenon in either blood pressure or heart rate. These results indicate that labetalol induces easily adjustable hypotension without compensatory tachycardia and rebound hypertension.

Labetalol. A reappraisal of its pharmacology, pharmacokinetics and therapeutic use in hypertension and ischaemic heart disease

Since labetalol was first reviewed in the Journal (1978), its scope of therapeutic use has expanded and become better defined. Labetalol is an adrenoceptor blocking drug with combined alpha- and beta-blocking properties. These result in a more favourable haemodynamic profile for labetalol compared with 'pure' beta-blockers or pure alpha-blockers, but also contribute to a wider range, but not an overall increased incidence, of adverse effects. The drug is effective and well-tolerated in patients with all grades of hypertension, but is of particular value in special subgroups such as Black patients, the elderly and patients with renal hypertension. While comparative studies are not extensive, available data show that the drug reduces blood pressure to a similar extent, and in a similar proportion of patients, as 'pure' beta-blockers such as propranolol, pure alpha-blockers such as prazosin, calcium antagonists (nifedipine, verapamil), and centrally acting drugs (clonidine and methyldopa). Labetalol is very effective in hypertensive pregnant women and in hypertensive crises, where it provides good control of blood pressure without serious adverse effects, and where few therapeutic options exist. Few controlled studies have investigated the use of labetalol in deliberate induction of hypotension or prevention of hypertension during anaesthesia, and also in patients with ischaemic heart disease. However, available evidence suggests a role for labetalol in these indications and further studies should aid in clarification of its efficacy in these areas. Thus, with its broad scope of therapeutic use in hypertension labetalol remains an important therapeutic option, and the drug may well find an additional place in the treatment of myocardial ischaemia if further evidence confirms encouraging preliminary findings.

Effect of labetalol or lidocaine on the hemodynamic response to intubation: a controlled randomized double-blind study

Labetalol, a combined alpha 1- and nonselective beta-adrenergic blocking drug, was compared to lidocaine or saline to minimize the hypertensive and tachycardic response to intubation in a controlled randomized double-blind study in patients undergoing surgical procedures under general anesthesia. Forty adult patients were divided into four groups of 10 each: placebo (saline), lidocaine 100 mg, labetalol 5 mg, or labetalol 10 mg. The double-blind preparation was administered as an IV bolus just prior to induction and 2 min before the stimulus of laryngoscopy and intubation. Heart rate and blood pressure were measured at 1-min intervals for 2 min prior to induction of anesthesia and through 6 min following induction of anesthesia. Labetalol 10 mg prevented a rise in heart rate after intubation compared to patients who received placebo, lidocaine 100 mg, or labetalol 5 mg. The hypertensive response to intubation was similar in all four groups. Labetalol 10 mg IV just prior to induction of anesthesia is a safe and cost-effective means of preventing tachycardia but not hypertension in response to laryngoscopy and intubation.

[Comparison in healthy volunteers of the systemic beta adrenergic receptor blockade by beta blockader eye drops]

The isoproterenol dose-response curve was used to assess quantitatively the degree of systemic beta-adrenoceptor blockade induced by metipranolol (Bétanol) and betaxolol (Bétoptic) eye drops. The study was carried out in twelve healthy volunteers, aged 22 +/- 1.4 yr. In a randomized double-blind trial, each volunteer received, on separate occasions at least one week apart, one drop in each eye of either placebo (physiological saline) or either of the ophthalmic beta-blockers. The intraocular pressure (Pio), heart rate (fc), arterial systolic (Pasys) and diastolic (Padia) pressures were measured before instillation of the eye drops after 15 to 30 min rest, and 3 h afterwards. The isoproterenol dose-response curve was studied 3 h after instillation of the drops. The CD25 (the amount of isoproterenol needed to increase fc by 25 b.min-1) was obtained by extrapolation on the least square linear regression curve. Both beta-blockers gave a significant fall in Pio compared with placebo, metipranolol more than betaxolol (p less than 0.02). There was also a significantly greater fall in fc with both metipranolol and betaxolol than with placebo. There were no changes in Pasys and Padia. CD25 was significantly increased with both beta-blocker eye drops as compared with placebo (p less than 0.05 for betaxolol; p less than 0.01 for metipranolol), but there was no difference between the two. Systemic absorption after topical application of ocular beta-blockers was thus confirmed for both metipranolol and betaxolol. However, the degree of beta-adrenoceptor blockade was weaker than that observed with other older ocular beta-blockers (timolol and carteolol).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of labetalol on arterial blood gas data, pulmonary haemodynamics and pulmonary shunting

The arterial oxygen and carbon dioxide tensions, pulmonary and systemic haemodynamics and pulmonary shunting and mechanics were measured during the first 30 min after intravenous labetalol administration. Thirty patients, recovering in the intensive care unit after neurosurgical interventions were randomly divided in 2 groups of 15 patients, receiving either labetalol or placebo. In the labetalol treated group the arterial oxygen tension decreased from 553.6 +/- 16.8 to 529.3 +/- 19.8 mmHg 5 min after the injection of labetalol. A concomitant increase in arterial carbon dioxide tension from 40.1 +/- 1.1 to 45.5 +/- 1.3 mmHg was noticed. Pulmonary vascular resistance decreased from 159.6 +/- 14.7 to 116.7 +/- 11.7 dynes.sec.cm-5 and pulmonary shunting increased from 4.8% +/- 1.4% to 8.1% +/- 2.4% 5 min following injection. All these changes were statistically significant for p less than 0.01. After 30 min all values had returned to their initial level. No changes were registered in the control group. As airway resistance appeared not to be affected by the labetalol administration it may be concluded that the observed changes in blood gas data are most likely due to a transient decrease of the pulmonary vascular resistance with a concomitant increase in pulmonary shunting.