The Hemodynamic Effects of Anesthetic Induction in Vascular Surgical Patients Chronically Treated with Angiotensin II Receptor Antagonists

Withholding vs. Continuing Angiotensin-Converting Enzyme Inhibitors or Angiotensin Receptor Blockers Before Non-cardiac Surgery in Older Patients: Study Protocol for a Multicenter Randomized Controlled Trial

Background: Older hypertensive adults are at increased risk for postoperative morbidity and mortality. As first line antihypertensive drug therapy, angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) have many beneficial effects. However, the use of ACEIs/ARBs in the perioperative period remains controversial. This study aims to determine the effects of withholding vs. continuing ACEIs/ARBs before non-cardiac surgery on perioperative hypotension and postoperative outcomes in older patients.

Methods: In this multicenter, randomized, double-blind, placebo-controlled trial, a total of 2036 patients aged 60–80 years undergoing non-cardiac surgical procedures will be randomly assigned, in a 1:1 ratio, to receive oral ACEIs/ARBs (the ACEIs/ARBs continued group) or inactive placebos (the ACEIs/ARBs withheld group) on the morning of surgery. For both groups, the ACEIs/ARBs will be continued from the first postoperative day. The primary outcome measure is the incidence of perioperative hypotensive events, defined as mean blood pressure (MBP) < 65 mmHg or ≥30% reduction in MBP from baseline during surgery and in a post-anesthesia care unit. The secondary outcomes include duration of perioperative hypotension, intraoperative use of fluids and vasopressors, hypotensive events within postoperative 3 days, and perioperative neurocognitive disorders, major adverse cardiocerebral events (a composite outcome of stroke, coma, myocardial infarction, heart block, and cardiac arrest), and mortality within 30 days after surgery.

Discussion: The results of this trial will offer an evidence-based perioperative ACEIs/ARBs therapy for older hypertensive adults undergoing non-cardiac surgery.

Study Registration: This study is approved by the Medical Ethics Committee of The First Affiliated Hospital of Soochow University (Approval No. 2020-077-1) and by the institutional ethics review board of each participating center. This protocol is registered at the Chinese Clinical Trials Registry (ChiCTR2000039376).

Short-Term Angiotensin Subtype 1 Receptor Blockade Does Not Alter the Circulatory Responses to Sympathetic Nervous System Modulation in Healthy Volunteers Before and During Sevoflurane Anesthesia: Results of a Pilot Study

OBJECTIVE

The mechanism of perioperative hypotension in patients taking an angiotensin-receptor blocker up to the time of surgery remains unclear. This study tested the hypothesis that short-term angiotensin-receptor blocker treatment attenuated the sympathetic and vascular responses to autonomic stimuli in volunteers undergoing anesthesia.

DESIGN

Randomized, crossover, blinded, pilot design.

SETTING

Zablocki Veterans Affairs Medical Center, Milwaukee, WI.

PARTICIPANTS

The study comprised 8 male and 6 female healthy, young volunteers (age 23±1.2 years [mean±standard error of the mean]).

INTERVENTIONS

Volunteers were studied after receiving oral placebo or 50 mg of losartan (angiotensin-receptor blocker) for 3 days before each test day. The effectiveness of angiotensin-receptor blocker treatment was confirmed using the mean arterial blood pressure response to intravenous angiotensin II (1-µg bolus). Eight volunteers underwent direct mean arterial pressure and forearm bloodflow measurements during conscious baseline, a cold pressor test, induction of anesthesia, tracheal intubation, maintenance of anesthesia with 1 minimum alveolar concentration of sevoflurane, and airway irritation with 12% desflurane. Six volunteers experienced mean arterial pressure responses to 0.1 mg of phenylephrine at baseline and during 1 minimum alveolar concentration of sevoflurane.

MEASUREMENTS AND MAIN RESULTS

Comparisons were made over time and across groups. Angiotensin-receptor blocker treatment significantly reduced-mean arterial pressure and forearm vascular resistance (forearm blood flow/mean arterial pressure) over time and blocked the mean arterial pressure response to angiotensin-II challenge. The changes in mean arterial pressure and forearm vascular resistance in response to all stressors did not differ between treatments. Mean arterial pressure increases from phenylephrine were preserved.

CONCLUSIONS

In healthy, young volunteers, sympathetically-mediated responses from the short-term use of an angiotensin-receptor blocker were not altered and most likely did not contribute to perioperative hypotension during the intraoperative period.

Cardiovascular anesthetic complications and treatment in oral surgery

Perioperative hypertension is a common problem. If hypertension is left untreated in patients at risk, infarctions and stroke are possible. There are limited choices of antihypertensive agents for the office. Aggressive antihypertensive therapy is not indicated because most of the episodes seen in the office are hypertensive urgencies and not emergencies. Hypotension is usually managed by decreasing the depth of anesthesia, intravenous fluids, and then vasopressors, typically ephedrine or phenylephrine. Consider treatment of hypotension whenever the mean arterial pressure decreases less than 60 mm Hg.

Perioperative blood pressure variability in the treated hypertensive patients

Perioperative blood pressure (BP) management is important to prevent cardiovascular complication, especially for hypertensive patients. In the present study, we investigated perioperative BP variability and contributing factors in hypertensive patients. Subjects were 28 treated hypertensive patients who underwent total or subtotal gastrectomy. Ambulatory BP monitoring was carried out before and after (16 days in average) the surgery. Angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and diuretics were withdrawn on the previous day, while other drugs were administered until the day of surgery. BP, body weight, blood chemistry, as well as the use of intravenous vasopressor or vasodepressor agents during the perioperative period were investigated. The 24-hour BP before surgery was 124 ± 19/70 ± 12 mm Hg, and the number of antihypertensive drugs was 1.8. In 22 patients, intravenous vasopressor agents were used during surgery, while another patient received intravenous vasodepressor agents after surgery. The 24-hour BP significantly decreased after surgery (-8.2 ± 14.7/-2.6 ± 7.3 mm Hg). Body weight, serum Na, and hematocrit also decreased. There were nine patients whose 24-hour systolic BP decreased by more than 10 mm Hg and for two patients more than 20 mm Hg. The decrease in BP correlated with the change in serum Na. Forty-three percent of the patients who took ACE inhibitors/ARBs showed BP reduction greater than 10 mm Hg, while 25% of the patients without these drugs showed such BP reduction. Our findings suggest that 24-hour BP decreases after gastrectomy. Patients taking ACE inhibitors or ARBs may need careful monitoring to prevent excessive BP fall.

Cardiac Arrest during Total Hip Arthroplasty in a Patient on an Angiotensin Receptor Antagonist

Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor antagonists (ARA) are effective and well-tolerated first-line drugs in the therapy of hypertension and, therefore, are frequently encountered in the perioperative setting. Hemodynamic compensation for volume depletion seen in the perioperative period is normally mediated by the renin-angiotensin system, which is blocked by ACEI/ARA. These drugs may contribute to severe hypotension during anesthesia induction and may have contributed to the cardiac arrest seen in this patient. Additional factors such as increased intra-abdominal pressures and respiratory obstructive episodes leading to diminished venous return, as well diuretic use and the fasting state, common in the perioperative orthopedic patient, are likely to have contributed as well. Medication use may be an easily modifiable risk factor for severe hypotension and possible cardiac arrest in the perioperative setting.

Beta-blockers, calcium channel blockers, angiotensin converting enzyme inhibitors and angiotensin receptor blockers: should they be stopped or not before ambulatory anaesthesia?

PURPOSE OF REVIEW

As day surgery continues to expand, more patients will be encountered who are chronically taking a range of cardiovascular medications for the management of hypertension and ischaemic heart disease. This review will consider the available evidence relating to whether or not these medications should be continued throughout the perioperative period in ambulatory surgical patients.

RECENT FINDINGS

There has been relatively little research in this area which is specific to ambulatory surgery and much of the available evidence from major surgery has been assembled over the many years that these medications have been in use. In order to provide a comprehensive and balanced review, we have considered relevant evidence outside of the usual review period.

SUMMARY

Patients should continue to take beta-blockers and calcium channel blockers on the day of surgery. Continuing angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers increases the likelihood of intraoperative hypotension. This can be reduced by withholding these drugs, but will also respond to simple treatments without any apparent adverse outcomes. It may therefore simplify instructions to patients if they are told to take all cardiac medications as normal.

Chronic AT1-receptor blockade does not alter cerebral oxygen supply/demand ratio during cardiopulmonary bypass in hypertensive patients

BACKGROUND

The angiotensin II receptor type 1 antagonist candesartan has been hypothesized to alter vasopressor requirements and brain-blood flow by changing cerebrovascular autoregulation. Therefore, we assessed the effects of a pre-anaesthetic treatment course with candesartan on cerebral arterial-jugular bulb oxygen content difference, middle cerebral artery blood velocity, and vasopressor requirements in hypertensive patients undergoing elective on-pump coronary artery bypass graft surgery.

METHODS

In a randomized, double-blind, placebo-controlled study, we evaluated the effects of candesartan (8 mg po/d, given for 6-8 days before surgery) in 35 hypertensive patients. The mean arterial pressure was maintained above 60 mmHg by bolus administration of phenylephrine, if required, and dosages were recorded.

RESULTS

Candesartan did not significantly alter oxygen content difference across the cerebral circulation, mean middle cerebral artery blood velocity during cardiopulmonary bypass, or phenylephrine requirements either before (0.0067 microg/kg/min+/-0.0042 vs. 0.0056 microg/kg/min+/-0.0049, P=0.48) or during cardiopulmonary bypass (0.0240 microg/kg/min+/-0.0240 vs. 0.0250 microg/kg/min+/-0.0190, P=0.97) compared with placebo.

CONCLUSION

Thus, a 6-8-day treatment course with candesartan does not alter global cerebral perfusion and oxygen supply/demand ratio during cardiopulmonary bypass, or vasopressor requirements in hypertensive patients undergoing on-pump coronary artery bypass graft surgery, and no deleterious consequences of AT1-receptor blockade were detected.

Effect of Isoflurane Anesthesia on Hemodynamics Following the Administration of an Angiotensin-Converting Enzyme Inhibitor in Cats

The objective of this study was to evaluate the hemodynamics of the anesthetic isoflurane in healthy cats given angiotensin-converting enzyme inhibitor (ACEI). The 7 healthy young cats and 3 old cats were received placebo or enalapril 0.5 mg/kg orally. The change in systolic arterial pressure from the baseline to 30 min postanesthesia in the ACEI group was significantly higher than in the placebo group (mean +/- SD: -39 +/- 13% vs. -17 +/- 12%, respectively). The present study indicated that general anesthesia may induce hypotension after the administration of an ACEI.

Should the angiotensin II antagonists be discontinued before surgery?

Angiotensin II antagonists (AIIA) are part of a new rational treatment of hypertension. Because adverse circulatory effects during anesthesia can occur in patients chronically treated with angiotensin-converting enzyme inhibitors, some clinicians discontinue them at least 24 h before operation. No data are available concerning AIIA administration in patients scheduled for vascular surgery performed under general anesthesia. The aim of this prospective randomized study was to compare hemodynamics during induction of anesthesia in patients chronically treated with AIIA and those of patients not receiving this drug on the morning before operation. Thirty-seven patients chronically treated with AIIA for hypertension were randomly assigned to two groups: Group I: AIIA discontinued on the day before surgery (n = 18); Group II: AIIA given 1 h before anesthesia (n = 19). Patients received sufentanil 0.4 microg/kg, propofol 1.5 mg/kg, and atracurium 0.5 mg/kg. During the procedure, the anesthesiologist was required to maintain systolic blood pressure and heart rate within 30% of baseline values using intravascular fluid administration and vasoconstric- tors (e.g. , ephedrine, phenylephrine, or terlipressin). Hemodynamic variables were recorded each 1 min. Hemodynamic study ended at incision. The number and duration of hemodynamic events were collected, and total doses of vasoactive drugs were noted in each group. Systolic arterial pressure was significantly decreased in Group II at 5, 15 and 23 min after induction of anesthesia (*P < 0.05). In this group, the decrease in systolic arterial pressure was associated with more frequent episodes of hypotension (AIIA withdrawn: 1 +/- 1; AIIA given: 2 +/- 1; P < 0.01), with a larger number of patients developing at least 1 episode of hypotension (AIIA withdrawn: 12; AIIA given: 19; P < 0.01), and a longer duration of an episode of hypotension (AIIA withdrawn: 3 +/- 4 min; AIIA given: 8 +/- 7 min; P < 0.01), and an increased need for vasoactive drugs. In conclusion, blockade of the renin-angiotensin system increases the potential hypotensive effect of anesthetic induction. A severe hypotensive episode, requiring vasoconstrictor treatment, occurs after induction of general anesthesia in patients chronically treated with AIIA. Recommendations to discontinue AIIA drugs on the day before the surgery may be justified.

IMPLICATIONS

This prospective randomized study demonstrated that more severe hypotensive episodes, requiring vasoconstrictor treatment, occur after induction of general anesthesia in patients chronically treated with AIIA and receiving this drug on the morning before operation, in comparison with those in whom AIIA were discontinued on the day before operation. Recommendations to discontinue these drugs on the day before the surgery may be justified.