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

Does preoperative administration of hypotensive agents affect the quality of the surgical field during endoscopic sinus surgery? A triple-blind randomized controlled trial

PURPOSE

Endoscopic sinus surgery (ESS) is a surgical procedure widely used in the treatment of various sinonasal conditions. Excessive bleeding during ESS leads to potentially major complications. The primary aim of this trial was to explore any different effects of bisoprolol and nifedipine on the intraoperative surgical field. In addition, the correlations regarding surgical field state, total blood loss (TBL), mean arterial pressure (MAP), and heart rate (HR) were also examined.

METHODS

A prospective, triple-blinded, randomized, placebo-controlled trial was conducted, including 72 patients between 18 and 65 years of age who underwent ESS. As an indicator of the worst state of the intraoperative surgical field, the Boezaart scale score was used, as evaluated by two surgeons. Appropriate statistical analysis was conducted to explore score comparisons across groups and correlations between vital signs, bleeding, and the operative field state.

RESULTS

No statistically significant difference was found among different intervention groups regarding the worst state of the surgical field (p = 0.367 > 0.05). The Boezaart scale score was positively correlated with TBL (rxy = 0.619, p = 0.000 < 0.001) and MAP (rxy = 0.259, p = 0.028 < 0.05). Furthermore, MAP was positively correlated with HR (rs = 0.254, p = 0.32 < 0.05).

CONCLUSION

Our study demonstrates that preoperative administration of bisoprolol and nifedipine does not affect the worst state of the operative field. However, vital signs seem to either directly or indirectly affect bleeding and operative field state, and agents affecting them are worth exploring further.

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.

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.

Target-controlled infusion of propofol and remifentanil combined with dexmedetomidine reduces functional endoscopic sinus surgery bleeding

The aim of the present study was to investigate the effects of target-controlled infusion (TCI) of propofol and remifentanil combined with dexmedetomidine on functional endoscopic sinus surgery (FESS) bleeding and surgical field. 62 patients scheduled to undergo FESS were randomly divided into experimental group (intravenous 0.5 µg kg^-1 h^-1 dexmedetomidine after 0.5 µg kg^-1 bolus within 15 min until the end of surgery) or control group (intravenous saline administration at the same dose). All patients underwent endotracheal intubation under general anesthesia with TCI of propofol and remifentanil for anesthesia induction and maintenance. During anesthesia, arterial pressure (MAP), heart rate (HR), intraoperative propofol and remifentanil dosage and intraoperative blood loss were recorded. Surgeons rated their satisfaction with the surgical field using the Numeric Rating Scale (NRS). Following surgery, visual analog scale (VAS) was assessed. During tracheal intubation and extubation, HR and MAP in the experimental group were significantly lower compared with the control group (P<0.05); HR was also significantly lower compared with the control group throughout surgery (P<0.05). The mean infusion rate of propofol and remifentanil was significantly lower in the experimental group compared with the control group (P=0.001 and P=0.045, respectively). Blood loss in the experimental group was significantly lower compared with the control group (P=0.007). NRS and VAS scores in the experimental group were significantly improved compared with control group (P<0.01). In conclusion, TCI of propofol and remifentanil for FESS combined with dexmedetomidine reduced intraoperative bleeding and improved the quality of surgical field compared with the same procedure without dexmedetomidine. Dexmedetomidine also reduced the increase in MAP and HR during tracheal intubation and extubation, and improved postoperative analgesia quality.

Controlled hypotension and blood loss during frontoorbital advancement

OBJECT

Controlled hypotension is routinely used during open repair of craniosynostosis to decrease blood loss, although this benefit is unproven. In this study the authors analyzed the longitudinal relationships between intraoperative mean arterial pressure (MAP) and calculated blood loss (CBL) during frontoorbital advancement (FOA) for craniosynostosis.

METHODS

The authors reviewed the records of infants with craniosynostosis who had undergone primary FOA between 1997 and 2009. Anesthesia records provided preoperative and serial intraoperative MAP. Interval measures of CBL had been determined during the course of the operation. The longitudinal relationships between MAP(mean), MAP(change), and CBL(change) were assessed over the same time interval and compared between adjacent time intervals to determine the directionality of associations.

RESULTS

Ninety infants (44 males and 46 females) underwent FOA at a mean age and weight of 10.7 ± 12.9 months and 9.0 ± 7.0 kg, respectively. The average intraoperative MAP was 56.1 ± 4.8 mm Hg, 22.6 ± 12.1% lower than preoperative baseline. A negative correlation was found between CBL(change) and MAP(mean) over the same interval (r = -0.31, p < 0.05), and an inverse relationship was noted between CBL(change) of the previous interval and MAP(change) of the next interval (r = -0.07, p < 0.05). Finally, there was no significant association between MAP(change) of the previous interval and CBL(change) of the next interval.

CONCLUSIONS

Calculated blood loss demonstrated a negative correlation with MAP during FOA. Directionality testing indicated that MAP did not affect intraoperative blood loss; instead, blood loss drove changes in MAP. Overall, these findings challenge the benefit of controlled hypotension during open craniofacial repair.

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.

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.

Pituitary-adrenal, hormonal changes during induced hypotension with labetol or isoflurane for middle-ear surgery

BACKGROUND

Pituitary-adrenal secretion during induced hypotension for middle-ear surgery has received little attention. Previous work failed to differentiate the effects of induced hypotension from surgical stimulation. We have undertaken a preliminary study examining the effects of hypotension, achieved with labetalol or isoflurane, on pituitary-adrenal secretion before, during and after middle-ear surgery.

METHODS

Twenty-four patients were allocated randomly to 3 groups. The control group were anaesthetised with isoflurane, and normotension maintained for 30 min before hypotension was induced with isoflurane and surgery started. In the labetalol group, this drug was given i.v. to obtain a mean arterial pressure (MAP) of 60 mm Hg for 30 min before surgery and hypotension maintained with labetalol during the operation. In the isoflurane group, hypotension was induced to a MAP of 60 mm Hg for 30 min before surgery and continued throughout the procedure. All 3 groups received metoprolol i.v. before hypotension was established. Blood samples were collected before induction of anaesthesia, during anaesthesia alone (normotensive or hypotensive), surgery with hypotension, and recovery. They were analysed for adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), cortisol and aldosterone.

RESULTS

Induced hypotension before surgery failed to stimulate release of ACTH, AVP and cortisol. No significant increase in these hormones occurred until the postoperative period. Aldosterone concentrations increased significantly during anaesthesia and hypotension in the labetalol and isoflurane groups (P<0.05) and continued to rise significantly in all 3 groups during surgery. However, there was no significant difference in aldosterone concentration before surgery between the control and the 2 hypotensive groups.

CONCLUSION

ACTH, AVP and cortisol secretion were not stimulated by induced hypotension to MAP of 60 mm Hg before surgery. Increased aldosterone secretion occurred and a further study with a larger sample size is needed.

Drug interactions with inhalational anaesthetics

The literature concerning the interactions between volatile anaesthetics, nitrous oxide and other compounds is reviewed. The majority are well known and most can be managed by careful dosage of the anaesthetics. The following interactions should be stressed since these are less predictable or potentially fatal. Of the cardiovascular drugs mainly the Ca++ channel blockers require attention. The volatile anaesthetics act synergistically with these drugs on the inhibition of cardiac conduction and may induce cardiac arrest. Aminoglycoside therapy should prompt an alternative to enflurane because of increased nephrotoxicity with this combination. Thiopentone induction makes the dog heart more susceptible to arrhythmias, especially during anaesthesia with volatile anaesthetics. Probably pentobarbitone, etomidate or a benzodiazepine should be preferred as an alternative to thiopentone when the use of adrenergic drugs peroperatively is anticipated. Nitrous oxide augments the sequelae after coronary air emboli and impaired cerebral perfusion in animals. The necessity of this drug should therefore be considered when anaesthetizing patients undergoing open heart surgery and patients with severe carotid or cerebral arteriosclerosis.

Effects of deliberate hypotension induced by labetalol with isoflurane on neuropsychological function

The effect of deliberate hypotension on brain function measured by neuropsychological tests was studied in 41 adult patients. Twenty-four patients were anaesthetized for middle-ear surgery with deliberate hypotension induced by labetalol with isoflurane (hypotensive group). Seventeen patients without hypotension served as a control group. The mean arterial pressure was 77 +/- 2 mmHg (10.3 +/- 0.3 kPa) before hypotension and 50 +/- 0 mmHg (6.7 +/- 0.0 kPa) during hypotension in the hypotensive group, and 86 +/- 2 mmHg (11.5 +/- 0.3 kPa) during anaesthesia in the control group. The following psychological tests were performed: four subtests of the Wechsler Adult Intelligence Scale (similarities, digit span, vocabulary and digit symbol), Trail-Making tests A and B, Zung tests (self-rating anxiety scale and self-rating depression scale) and two-part memory test battery with immediate and delayed recall. The tests were performed preoperatively and 2 days postoperatively. There were no statistically significant differences between the groups in any of the tests in the changes from preoperative value to postoperative value. The results indicate that hypotension induced by labetalol with isoflurane has no significant harmful effects on mental functions compared to normotensive anaesthesia.

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)

Plasma renin, catecholamines, vasopressin and aldosterone during hypotension induced by labetalol with isoflurane

Deliberate hypotension may induce secretion of stress hormones. In the present study, the effects of hypotension induced by labetalol with isoflurane or plasma renin activity, plasma concentrations of adrenaline, noradrenaline, vasopressin, and aldosterone were investigated in eight adult patients undergoing middle-ear surgery. The mean arterial pressure was 50 mmHg (6.7 kPa) during hypotension. Plasma renin activity rose significantly during anaesthesia before hypotension, being similar during hypotension and before hypotension, and in returned postoperatively to the initial level. Plasma adrenaline fell significantly during hypotension and rose after anaesthesia to the preanaesthetic level. Plasma noradrenaline rose slightly during hypotension and after anaesthesia, but not significantly. Plasma vasopressin rose significantly after anaesthesia. Plasma aldosterone increased slightly throughout the study, but not significantly during any phase. In conclusion, labetalol with isoflurane-induced hypotension seems to attenuate the stress response in these operations. During hypotension, plasma renin activity is not an essential compensatory mechanism, which antagonises the decrease of blood pressure. Plasma vasopressin has no role in regulating blood pressure during labetalol-induced hypotension.

Clonidine premedication: a useful adjunct in producing deliberate hypotension

The effect of clonidine on the dose requirements of labetalol and isoflurane for hypotension was studied in 20 adult patients undergoing middle-ear surgery. Group I (10 patients) received as premedication only pethidine 1 mg.kg-1 i.m., and Group II (10 patients) clonidine 4-5 micrograms.kg-1 p.o. in addition to pethidine. Fentanyl was used for analgesia and d-tubocurarine for muscle relaxation. The dose of labetalol required to induce hypotension to the mean arterial pressure (MAP) 50 mmHg (6.7 kPa) was 0.85 +/- 0.08 mg.kg-1 in Group I, and 0.56 +/- 0.08 mg.kg-1 in Group II (P less than 0.05). The mean isoflurane concentration in inspiratory gas for the maintenance of hypotension was 0.8 +/- 0.1 vol% in Group I, and 0.6 +/- 0.1 vol% in Group II (P less than 0.05). Before hypotension, MAP decreased significantly in Group II, and the heart rate (HR) decreased in both groups. There were no significant differences in MAP and HR between the groups during any phase. Urine flow rates (UF) were lower in Group II (0.23 +/- 0.04 ml.min-1) than in Group I (0.68 +/- 0.16 ml.min-1) before hypotension (P less than 0.05) and during hypotension (0.08 +/- 0.02 ml.min-1 vs. 0.68 +/- 0.32 ml.min-1, P less than 0.05). After anaesthesia, there was no difference in UF between the groups. The results indicate that clonidine can be used for deliberate hypotension to decrease the dose requirements of labetalol and isoflurane.