A comparison of labetalol and nitroprusside for inducing hypotension during major 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.

Comparing Labetalol and Nitroglycerine on Inducing Controlled Hypotension and Intraoperative Blood Loss in Rhinoplasty: A Single-Blinded Clinical Trial

Background

Uncontrolled bleeding during surgery is one of the main predisposing factors for failure of the surgeon and complications following rhinoplasty. The current study aimed at comparing the effects of nitroglycerine and labetalol on the induction of controlled hypotension and bleeding volume during septorhinoplasty.

Methods

The current randomized, controlled, clinical trial enrolled 60 patients candidate for septorhinoplasty at Firoozgar hospital in Tehran, Iran, in 2 equal groups receiving either 0.1 to 1 mcg/kg/minute nitroglycerine or 2 to 4 mg/minute labetalol to achieve a mean arterial blood pressure of about 60 to 65 mmHg. In case the targeted blood pressure was not achieved, isoflurane was added. Degree of bleeding was evaluated by the volume of suctioned blood and the blood remaining in surgical gauzes. Additionally, the surgeon's satisfaction with the surgical field was evaluated by a scoring system. The collected data were, then, compared between the study groups by the statistical methods.

Results

Based on the current study findings, systolic (P < 0.001), diastolic (P = 0.002), and the mean arterial blood pressures (P < 0.001) were significantly lower in the nitroglycerine group. Ninety percent of the patients in the labetalol group received isoflurane to achieve the targeted blood pressure defined as controlled hypotension. There was no significant difference between the groups regarding the volume of bleeding (P = 0.75); however, the surgeons were more satisfied with nitroglycerine than labetalol (P < 0.001).

Conclusions

It was concluded that nitroglycerine had a better effect, in comparison to labetalol, on inducing the controlled hypotension in septorhinoplasty.

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.

Pharmacologic drugs for controlled hypotension

Due to the risks of transfusion reactions and the transmission of infectious diseases, there has been increased interest in measures to limit intraoperative blood loss and avoid the need for homologous transfusion. Controlled hypotension is one technique that has been used to limit intraoperative blood loss. Several drugs have been used alone or in combination for controlled hypotension, including the inhalational anesthetics, direct acting vasodilators such as nitroglycerin and nitroprusside, beta adrenergic antagonists, and calcium channel blockers. Various drugs available to the clinician for controlled hypotension are reviewed.