Preoperative inhibition of angiotensin-converting enzyme improves systemic and renal haemodynamic changes during aortic abdominal surgery

Perioperative Renin-Angiotensin System Inhibitors Improve Major Outcomes of Heart Failure Patients Undergoing Cardiac Surgery: A Propensity-Adjusted Cohort Study

OBJECTIVE

The aim of this study was to study the association of perioperative administration of renin angiotensin system inhibitors (RASi) and clinical outcomes of patients with heart failure (HF) undergoing cardiac surgery.

SUMMARY BACKGROUND DATA

It is controversial whether the perioperative RASi should be administered in HF patients undergoing cardiac surgery.

METHODS

A total of 2338 patients with HF and undergoing CABG and/or valve surgeries at multiple hospitals from 2001 to 2015 were identified from STS database. After adjustment using propensity score and instrumental variable, logistic regression was conducted to analyze the influence of preoperative continuation of RASi (PreRASi) on short-term in-hospital outcomes. Independent risk factors of 30-day mortality, major adverse cardiovascular events (MACE), and renal failure were analyzed by use of stepwise logistic regression. The effects of pre- and postoperative use of RASi (PostRASi) on long-term mortality were analyzed using survival analyses. Stepwise Cox regression was conducted to analyze the independent risk factors of 6-year mortality. The relationships of HF status and surgery type with perioperative RASi, as well as PreRASi-PostRASi, were also evaluated by subgroup analyses.

RESULTS

PreRASi was associated with lower incidences of 30-day mortality [ P < 0.0001, odds ratio (OR): 0.556, 95% confidence interval (CI) 0.405-0.763], stroke ( P =0.035, OR: 0.585, 95% CI: 0.355-0.962), renal failure ( P =0.007, OR: 0.663, 95% CI: 0.493-0.894). Both PreRASi ( P =0.0137) and PostRASi ( P =0.007) reduced 6-year mortality compared with the No-RASi groups.

CONCLUSIONS

Pre- and postoperative use of RASi was associated with better outcomes for the patients who have HF and undergo CABG and/or valve surgeries. Preoperative continuation and postoperative restoration are warranted in these patients.

Incidence of and risk factors for severe acute kidney injury in children with heart failure treated with renin-angiotensin system inhibitors

No large cohort study has yet determined the incidence of acute kidney injury (AKI) in children with heart failure treated with renin-angiotensin system (RAS) inhibitors. We thus retrospectively analyzed the incidence and risk factors for severe AKI (stages 2-3 according to the Kidney Disease Improving Global Outcomes (KDIGO) guidelines) at our institutions from 2008 to 2011. Among 312 children (162 boys; median age, 7.3 months), 59 cases of AKI occurred in 45 children. The incidence of AKI was 14.3 cases per 100 person-years overall (follow-up 413.6 person-years), or 27.3, 16.8, and 4.5 cases per 100 person-years in children aged <1, 1-3, and ≥4 years, respectively. Among them, 23 (39.0 %) children had metabolic acidosis and 14 (23.7 %) had hyperkalemia. Younger age, myocardial disease, cyanotic congenital heart disease, use of spironolactone, and cardiac surgery were independent risk factors for AKI. Furthermore, 37.3 % of children suffered dehydration during AKI.

CONCLUSION

AKI incidence is relatively high in children, particularly younger children, with heart failure treated using RAS inhibitors. Careful monitoring of renal function and serum electrolytes is essential. Proper management of fluid balance after infection and cardiac surgery may reduce the risk of AKI. Temporary discontinuation in RAS inhibitors should be considered during dehydration or surgery.

WHAT IS KNOWN

• Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are the two main classes of renin-angiotensin system (RAS) inhibitors used to treat hypertension, heart failure, and chronic kidney disease. Acute kidney injury (AKI) and hyperkalemia are potentially life-threatening complications associated with the use of ACEIs and ARBs. Some reports have suggested that dehydration and cardiac surgery are risk factors for AKI in children. However, no large-scale cohort studies have determined the incidence of AKI, its risk factors, and its outcomes in children with heart failure treated with ACEIs and/or ARBs. What is new: • In this retrospective cohort study, we determined the incidence, severity, and risk factors for severe AKI in children with heart failure treated with ACEIs and/or ARBs. The incidence of AKI in these children was relatively high (14.3 episodes per 100 person-years). In addition, younger age, myocardial disease, cyanotic congenital heart disease, concomitant use of spironolactone, and cardiac surgery were risk factors for AKI. Furthermore, 37.3 % of children had dehydration during AKI episodes. • Our results suggested that appropriate fluid balance after infection and cardiac surgery might reduce the risk of AKI and its complications. Temporary discontinuation or reductions in the levels of ACEIs and/or ARBs during dehydration or before surgery may also be warranted in these patients.

Perioperative angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers for preventing mortality and morbidity in adults

BACKGROUND

Perioperative hypertension requires careful management. Angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II type 1 receptor blockers (ARBs) have shown efficacy in treating hypertension associated with surgery. However, there is lack of consensus about whether they can prevent mortality and morbidity.

OBJECTIVES

To systematically assess the benefits and harms of administration of ACEIs or ARBs perioperatively for the prevention of mortality and morbidity in adults (aged 18 years and above) undergoing any type of surgery under general anaesthesia.

SEARCH METHODS

We searched the current issue of the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 12), Ovid MEDLINE (1966 to 8 December 2014), EMBASE (1980 to 8 December 2014), and references of the retrieved randomized trials, meta-analyses, and systematic reviews.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing perioperative administration of ACEIs or ARBs with placebo in adults (aged 18 years and above) undergoing any type of surgery under general anaesthesia. We excluded studies in which participants underwent procedures that required local anaesthesia only, or participants who had already been on ACEIs or ARBs.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, assessed the risk of bias, and extracted data. We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included seven RCTs with a total of 571 participants in the review. Two of the seven trials involved 36 participants undergoing non-cardiac vascular surgery (infrarenal aortic surgery), and five involved 535 participants undergoing cardiac surgery, including valvular surgery, coronary artery bypass surgery, and cardiopulmonary bypass surgery. The intervention was started from 11 days to 25 minutes before surgery in six trials and during surgery in one trial. We considered all seven RCTs to carry a high risk of bias. The effects of ACEIs or ARBs on perioperative mortality and acute myocardial infarction were uncertain because the quality of the evidence was very low. The risk of death was 2.7% in the ACEIs or ARBs group and 1.6% in the placebo group (risk ratio (RR) 1.61; 95% confidence interval (CI) 0.44 to 5.85). The risk of acute myocardial infarction was 1.7% in the ACEIs or ARBs group and 3.0% in the placebo group (RR 0.55; 95% CI 0.14 to 2.26). ACEIs or ARBs may improve congestive heart failure (cardiac index) perioperatively (mean difference (MD) -0.60; 95% CI -0.70 to -0.50, very low-quality evidence). In terms of rate of complications, there was no difference in perioperative cerebrovascular complications (RR 0.48; 95% CI 0.18 to 1.28, very low-quality evidence) and hypotension (RR 1.95; 95% CI 0.86 to 4.41, very low-quality evidence). Cardiac surgery-related renal failure was not reported. ACEIs or ARBs were associated with shortened length of hospital stay (MD -0.54; 95% CI -0.93 to -0.16, P value = 0.005, very low-quality evidence). These findings should be interpreted cautiously due to likely confounding by the clinical backgrounds of the participants. ACEIs or ARBs may shorten the length of hospital stay, (MD -0.54; 95% CI -0.93 to -0.16, very low-quality evidence) Two studies reported adverse events, and there was no evidence of a difference between the ACEIs or ARBs and control groups.

AUTHORS' CONCLUSIONS

Overall, this review did not find evidence to support that perioperative ACEIs or ARBs can prevent mortality, morbidity, and complications (hypotension, perioperative cerebrovascular complications, and cardiac surgery-related renal failure). We found no evidence showing that the use of these drugs may reduce the rate of acute myocardial infarction. However, ACEIs or ARBs may increase cardiac output perioperatively. Due to the low and very low methodology quality, high risk of bias, and lack of power of the included studies, the true effect may be substantially different from the observed estimates. Perioperative (mainly elective cardiac surgery, according to included studies) initiation of ACEIs or ARBs therapy should be individualized.

An update of the role of renin angiotensin in cardiovascular homeostasis

The renin angiotensin system (RAS) is thought to be the body's main vasoconstrictor system, with physiological effects mediated via the interaction of angiotensin II with angiotensin I receptors (the "classic" RAS model). However, since the discovery of the heptapeptide angiotensin 1-7 and the development of the concept of the "alternate" RAS system, with its ability to reduce arterial blood pressure, our understanding of this physiologic system has changed dramatically. In this review, we focus on the newly discovered functions of the RAS, particularly the potential clinical significance of these developments, especially in the realm of new pharmacologic interventions for treating cardiovascular disease.

Interventions for protecting renal function in the perioperative period

BACKGROUND

Various methods have been used to try to protect kidney function in patients undergoing surgery. These most often include pharmacological interventions such as dopamine and its analogues, diuretics, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, N-acetyl cysteine (NAC), atrial natriuretic peptide (ANP), sodium bicarbonate, antioxidants and erythropoietin (EPO).

OBJECTIVES

This review is aimed at determining the effectiveness of various measures advocated to protect patients' kidneys during the perioperative period.We considered the following questions: (1) Are any specific measures known to protect kidney function during the perioperative period? (2) Of measures used to protect the kidneys during the perioperative period, does any one method appear to be more effective than the others? (3) Of measures used to protect the kidneys during the perioperative period,does any one method appear to be safer than the others?

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2012), MEDLINE (Ovid SP) (1966 to August 2012) and EMBASE (Ovid SP) (1988 to August 2012). We originally handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery) (1985 to 2004). However, because these journals are properly indexed in MEDLINE, we decided to rely on electronic searches only without handsearching the journals from 2004 onwards.

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery for which a treatment measure was used for the purpose of providing renal protection during the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 72 studies for inclusion in this review. Two review authors extracted data from all selected studies and entered them into RevMan 5.1; then the data were appropriately analysed. We performed subgroup analyses for type of intervention, type of surgical procedure and pre-existing renal dysfunction. We undertook sensitivity analyses for studies with high and moderately good methodological quality.

MAIN RESULTS

The updated review included data from 72 studies, comprising a total of 4378 participants. Of these, 2291 received some form of treatment and 2087 acted as controls. The interventions consisted most often of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, NAC, ANP, sodium bicarbonate, antioxidants and EPO or selected hydration fluids. Some clinical heterogeneity and varying risk of bias were noted amongst the studies, although we were able to meaningfully interpret the data. Results showed significant heterogeneity and indicated that most interventions provided no benefit.Data on perioperative mortality were reported in 41 studies and data on acute renal injury in 44 studies (all interventions combined). Because of considerable clinical heterogeneity (different clinical scenarios, as well as considerable methodological variability amongst the studies), we did not perform a meta-analysis on the combined data.Subgroup analysis of major interventions and surgical procedures showed no significant influence of interventions on reported mortality and acute renal injury. For the subgroup of participants who had pre-existing renal damage, the risk of mortality from 10 trials (959 participants) was estimated as odds ratio (OR) 0.76, 95% confidence interval (CI) 0.38 to 1.52; the risk of acute renal injury (as reported in the trials) was estimated from 11 trials (979 participants) as OR 0.43, 95% CI 0.23 to 0.80. Subgroup analysis of studies that were rated as having low risk of bias revealed that 19 studies reported mortality numbers (1604 participants); OR was 1.01, 95% CI 0.54 to 1.90. Fifteen studies reported data on acute renal injury (criteria chosen by the individual studies; 1600 participants); OR was 1.03, 95% CI 0.54 to 1.97.

AUTHORS' CONCLUSIONS

No reliable evidence from the available literature suggests that interventions during surgery can protect the kidneys from damage. However, the criteria used to diagnose acute renal damage varied in many of the older studies selected for inclusion in this review, many of which suffered from poor methodological quality such as insufficient participant numbers and poor definitions of end points such as acute renal failure and acute renal injury. Recent methods of detecting renal damage such as the use of specific biomarkers and better defined criteria for identifying renal damage (RIFLE (risk, injury, failure, loss of kidney function and end-stage renal failure) or AKI (acute kidney injury)) may have to be explored further to determine any possible benefit derived from interventions used to protect the kidneys during the perioperative period.

Multifactorial Model and Treatment Approaches of Refractory Hypotension in a Patient Who Took an ACE Inhibitor the Day of Surgery

In the field of anesthesiology, there is wide debate on discontinuing angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy the day of noncardiac surgery. Although there have been many studies attributing perioperative hypotension to same-day ACEI and ARB use, there are many additional variables that play a role in perioperative hypotension. Additionally, restoring blood pressure in these patients presents a unique challenge to anesthesiologists. A case report is presented in which a patient took her ACEI the day of surgery and developed refractory hypotension during surgery. The evidence of ACEI use on the day of surgery and development of hypotension is reviewed, and additional variables that contributed to this hypotensive episode are discussed. Lastly, current challenges in restoring blood pressure are presented, and a basic model on treatment approaches for refractory hypotension in the setting of perioperative ACEI use is proposed.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine and its analogues, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes that included renal failure and mortality as well as changes in renal function tests, such as urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to June, 2007), and EMBASE (1988 to June, 2007); and handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 53 studies for inclusion in this review. As well as data analysis from all the studies, we performed subgroup analysis for type of intervention, type of surgical procedure, and pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high and moderately good methodological quality.

MAIN RESULTS

The review included data from 53 studies, comprising a total of 2327 participants. Of these, 1293 received some form of treatment and 1034 acted as controls. The interventions mostly consisted of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, or selected hydration fluids. The results indicated that certain interventions showed minimal benefits. All the results suffered from significant heterogeneity. Hence we cannot draw conclusions about the effectiveness of these interventions in protecting patients' kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the available literature to suggest that interventions during surgery can protect the kidneys from damage. There is a need for more studies with high methodological quality. One particular area for further study may be patients with pre-existing renal dysfunction undergoing surgery.

Preoperative use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers is associated with increased risk for acute kidney injury after cardiovascular surgery

BACKGROUND AND OBJECTIVES

Acute kidney injury (AKI) occurs commonly after cardiac surgery. Most patients who undergo cardiac surgery receive long-term treatment with angiotensin-converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB). The aim of this study was to determine whether long-term use of ACEI/ARB is associated with an increased incidence of AKI after cardiac surgery.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a retrospective cohort study of 1358 adult patients who underwent cardiac surgery between January 1, 2001, and December 31, 2005, in two tertiary care hospitals in Buffalo, NY. The incidence of AKI was determined after cardiac surgery. Clinical data were collected using a standardized form that included comorbid condition, use of ACEI/ARB, and intraoperative and postoperative complications.

RESULTS

Overall, 40.2% of patients developed AKI. Preoperative variables that were significantly associated with development of AKI included increasing age; nonwhite race; combined valve surgery and coronary artery bypass grafting compared with coronary artery bypass grafting alone; American Society of Anesthesiologists (ASA) Risk Score category 4/5 compared with 2 to 3; presence of diabetes, congestive heart failure, or neurologic disease at baseline; use of ACEI/ARB; and emergency surgery. Intra- and postoperative factors that were associated with postoperative AKI were hypotension during surgery, use of vasopressors, and postoperative hypotension. Multiple regression logistic model confirmed an independent and significant association of AKI and preoperative use of ACEI/ARB. This was confirmed using a bivariate-probit and propensity score model that adjusts for confounding by indication of use and selection bias.

CONCLUSIONS

Preoperative use of ACEI/ARB is associated with a 27.6% higher risk for AKI postoperatively. Stopping ACEI or ARB before cardiac surgery may reduce the incidence of AKI.

Anesthesia and renal disease

PURPOSE OF REVIEW

To present and interpret the relevant research (Jan 2001-Feb 2002) which has the most important implications for clinical anesthesiology as regards the prevention of perioperative renal dysfunction and the anesthetic management of patients with renal disease.

RECENT FINDINGS

Prolonged sevoflurane anesthesia with fresh gas flow less than 1 l min is unlikely to lead to clinically significant renal injury. When used as maintenance agents for patients undergoing coronary artery bypass grafting, sevoflurane anesthesia at a fresh gas flow of 3 l min, isoflurane and propofol are associated with similar rates of postoperative renal dysfunction. Less compound A is produced with smaller soda lime containers. High flow sevoflurane anesthesia (fresh gas flow of 4-6 l min) in combination with perioperative ketorolac is unlikely to lead to renal injury. Chronic treatment with angiotensin-converting enzyme inhibitors is associated with an increased incidence of postoperative renal impairment in patients undergoing elective aortic surgery. Thoracic epidural anesthesia and postoperative analgesia are associated with a decreased incidence of renal failure in patients undergoing coronary artery bypass grafting. Compared with open surgical repair, endovascular repair of aortic aneurysm is associated with less renal injury.

SUMMARY

Sevoflurane anesthesia at low or high fresh gas flow rates is probably no more injurious to the kidneys than other commonly used maintenance agents. Chronic angiotensin-converting enzyme inhibition may increase perioperative renal dysfunction. The use of thoracic epidural anesthesia and analgesia may reduce the incidence of postoperative renal failure.

Perioperative management of chronic heart failure

Heart failure (HF) is one of the few cardiac conditions that is increasing. Despite a better understanding of how hormones and other signaling systems underlie the pathophysiology, and despite improved outcomes from pharmacologic therapy, many HF patients receive no effective treatment. Patients with HF commonly require medical diagnosis and management in operating rooms and critical care units; thus anesthesiologists are obliged to remain up-to-date both with advances in outpatient (chronic) medical management and with inpatient treatments for acute exacerbations of HF. Accordingly, we reviewed angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-adrenergic receptor blockers, and aldosterone antagonists because these drugs prolong life and are included in current clinical practice guidelines for treating patients with chronic HF. We also reviewed the implications of chronic HF for patients undergoing surgery and anesthesia and discuss how best to provide intensive treatment for acute exacerbations of symptoms, such as might be caused by excessive intravascular volume, inappropriate drug "holidays," or worsening of the underlying cardiac disease.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials, which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes such as renal failure and mortality, as well as changes in the renal function tests, including urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to 2004) and EMBASE (1988 to 2004) and hand searched six journals (British Journal of Anaesthesia; Anesthesia and Analgesia; Anesthesiology; Annals of Surgery; Journal of Thoracic and Cardiovascular Surgery and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adult population undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 37 studies for inclusion in this review. As well as analysis of the data from all the studies, we also performed subgroup analysis for type of interventions, types of surgical procedures and those with pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high methodological quality.

MAIN RESULTS

The review included data from 37 studies, comprising a total of 1227 patients. Of these, 658 received some form of treatment and 569 acted as controls. The interventions were mostly employing different pharmaceutical agents such as dopamine, diuretics, calcium channel blockers. ACE inhibitors or selected hydration fluids. The results indicated that certain interventions showed some benefits, but all the results suffered from significant heterogeneity. Hence we can draw no conclusions about the effectiveness of these interventions in protecting the kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from available literature to suggest that interventions during surgery can protect the kidneys from damage. However, there is a need for more studies of high methodological quality. One particular area for further studies may be on patients with pre-existing renal dysfunction undergoing surgery.

The Management of Abdominal Aortic Aneurysms in Patients with Concurrent Renal Impairment

INTRODUCTION

Patients with concurrent renal impairment and abdominal aortic aneurysms present a significant challenge in terms of pre-operative, intra-operative and post-operative management. This aim of this review was to determine the risks of surgery in this patient group and determine whether any clear management strategies exist to enhance their clinical management.

METHODS

Systematic review of published literature giving details of the outcome of open or endovascular abdominal aortic aneurysm repair in patients with pre-operative renal impairment. Papers concerning the management of post-operative acute renal failure in patients with normal pre-operative renal function has not been included.

RESULTS

There is little data regarding patients with end-stage renal failure and AAA although these patients appear to have a high peri-operative mortality rate. In contrast, those with renal impairment do not have a significantly higher mortality rate than those with normal renal function, rather they have a higher risk of complications associated with surgery and may require more intensive post-operative organ system support than normal patients. Many have a transient deterioration in renal function in the immediate peri-operative period that will resolve. In the case of patients with ruptured AAA, it is not clear whether pre-operative renal impairment affects mortality.

The chronic inhibition of angiotensin-converting enzyme impairs postoperative renal function

Postoperative renal impairment can increase postoperative mortality and morbidity. We sought to identify preoperative risk factors responsible for postoperative renal impairment in patients undergoing aortic surgery. This prospective study included 249 patients admitted for aortic surgery. Preoperative and postoperative glomerular filtration rates (GFRs) were assessed with pre- and postoperative creatinine clearance measurements. Postoperative renal impairment was defined as a 20% decrease in GFR between Day 0 (before surgery) and Day 7 +/-1 day (after surgery). Preoperative and intraoperative variables considered as potentially responsible for postoperative renal impairment were tested. Chronic treatment with angiotensin-converting enzyme inhibitors (ACEIs) was the only factor significantly associated with postoperative renal impairment (odds ratio [95% confidence interval] = 2.01 [1.05-3.83]). Chronic preoperative ACEI treatment is significantly associated with postoperative renal impairment. Inhibition of renal compensatory mechanisms caused by renin angiotensin system blockade might be responsible for the observed decrease in renal function in patients chronically treated with ACEIs undergoing aortic surgery. However, age and preoperative renal dysfunction were not associated with a postoperative decrease in GFR, but they were associated with a postoperative creatinine clearance <60 mL/min.

IMPLICATIONS

The aim of this study was to identify preoperative risk factors responsible for postoperative renal impairment in vascular surgery. Chronic angiotensin-converting enzyme inhibitor treatment was the only factor significantly associated with postoperative renal impairment. Inhibition of renal compensatory mechanisms caused by renin angiotensin system blockade might be responsible for the observed decreased renal function.

Angiotensin in cardiac surgery: efficacy in patients on angiotensin converting enzyme inhibitors

BACKGROUND

Patients presenting for cardiac surgery are often treated with angiotensin converting enzyme inhibitors (ACEIs), either for heart failure or hypertension. Control of systemic vascular resistance (SVR) during surgery can be difficult in such patients. Angiotensin II has been available as an unlicensed vasoconstrictor, but there is concern about renal damage and its use.

AIM

This study compared a standard vasoconstrictor with angiotensin II and examined the effect on renal function after cardiac surgery.

METHOD

Twenty consecutive, consenting patients scheduled for cardiac surgery that had been taking ACEIs for at least 6 months, were randomly assigned to receive either phenylephrine or angiotensin II for the control of SVR during and for 24 h after cardiac surgery. A pulmonary artery catheter was used to guide therapy. Creatinine clearance was measured before, 24 and 48 h after surgery.

RESULTS

Low SVR and blood pressure requiring intervention was seen in all patients, particularly during cardiopulmonary bypass. One patient in the control group failed to respond to P, but responded normally to angiotensin II. Neither drug caused renal impairment.

CONCLUSION

Angiotensin II is a safe alternative to phenylephrine in patients on ACEIs and should be considered in patients who fail to respond to conventional vasoconstrictors.

Haemodynamic and renal effects of intravenous enalaprilat during coronary artery bypass graft surgery in patients with ischaemic heart dysfunction

Renal dysfunction occurring after open heart surgery is multifactorial in origin but activation of the renin-angiotensin system may have a prominent role. Fourteen patients with ischaemic heart dysfunction scheduled for elective coronary artery bypass graft (CABG) surgery were allocated to a treatment group [enalaprilat for 2 days; ACEI (angiotensin-converting enzyme inhibitor) group, n=7] or a control group (n=7). The cardiac index was significantly higher in ACEI-treated patients than in the controls before and after cardiopulmonary bypass (CPB) (P<0.05) and on postoperative day 2 (P<0.05). The systemic vascular resistance was significantly lower in the ACEI-treated patients than in the controls before and after CPB (P<0.05). Renal plasma flow, measured as [131I]orthoiodohippuran clearance (ClH), was higher in the ACEI group than in the control group before CPB, as was endogenous creatinine clearance after CPB (P<0.05). On post-operative day 7, ClH was significantly higher in the ACEI group than in the control group (P<0.05). Plasma renin activity and vasopressin concentration increased in both groups during CPB (P<0.05). The study demonstrates that administration of an i.v. ACEI, enalaprilat, improves cardiac output during CABG surgery in patients with ischaemic heart dysfunction. Moreover, renal perfusion was better maintained during surgery, and this effect was sustained up to post-operative day 7.

Effect of intra-aortic magnesium on renal function during and after abdominal aortic surgery: a pilot study

BACKGROUND

Infrarenal aortic cross-clamping causes renal vasoconstriction. Magnesium may protect against renal deterioration through its vasodilatory properties.

METHODS

Thirty patients with normal preoperative renal function undergoing infrarenal aortic cross-clamping for elective aortic surgery received magnesium (4 mmol) or saline into the aorta immediately after aortic cross-clamping and again just before unclamping in a double-blind fashion. Pulmonary artery occlusion pressure was maintained 215 mmHg. Five patients with magnesium were excluded due to need for intravenous nitroglycerine because of myocardial ischaemia during the study.

RESULTS

Postoperative creatinine clearance remained unchanged in both groups. Urinary N-acetyl-beta-D-glucosaminidase excretion increased before and decreased after aortic cross-clamping in both groups. The concentrations of glutathione peroxidase in serum were identical between the two groups.

CONCLUSIONS

These data indicate that intra-aortic magnesium had no effect on renal function during or after aortic cross-clamping.

The dynamics of glomerular filtration after Caesarean section

The objective of this study was to determine whether the glomerular hyperfiltration of pregnancy is maintained even after Caesarean section and, if so, to define the responsible hemodynamics. The dynamics of glomerular filtration were evaluated in 12 healthy women who had just completed an uncomplicated pregnancy and were delivered by Caesarean section. Age-matched but non-gravid female volunteers (n = 22) served as control subjects. GFR in postpartum women was elevated above control values by 41%; 149+/-10 versus 106+/-3 ml/min per 1.73 m2, respectively (P < 0.001). In contrast, corresponding renal plasma flow was the same in the two groups, such that the postpartum filtration fraction was significantly elevated by 20%. Computation of glomerular intracapillary oncotic pressure (piGC) from knowledge of plasma oncotic pressure and the filtration fraction revealed this quantity to be significantly reduced in postpartum women, 20.6+/-1.7 versus 26.1+/-2.0 mmHg in control subjects (P < 0.001). A theoretical analysis of glomerular ultrafiltration suggests that depression of piGC, the force opposing the formation of filtrate, is predominantly or uniquely responsible for the observed postpartum hyperfiltration.

Chronic angiotensin converting inhibition does not influence renal hemodynamic and function during cardiac surgery

PURPOSE

Treatment with angiotensin-converting enzyme (ACE) inhibitors affects the autoregulation of renal blood flow and glomerular filtration and provides renal protective effects. The purpose of this case-control study was to investigate the effects of chronic ACE inhibition on perioperative renal hemodynamics and function.

METHOD

We prospectively studied renal function in two groups of patients, chronically treated or not, with ACE inhibitors (ACEI and control; n = 16, in each group) who underwent elective cardiac surgery under hypothermic cardiopulmonary bypass. Glomerular filtration rate, effective renal plasma flow, osmolar clearance and fractional excretion of sodium and potassium were determined before, during and after CPB. Additional measurements included plasma atrial natriuretic factor (ANF) as well as plasma and urinary cyclic GMP (cGMP), thromboxane B2 (TxB2) and 6-keto-PGF1.

RESULTS

Renal functional and hemodynamic variables did not differ between the two groups, at any period. Cardiopulmonary bypass induced increases in urinary flow, osmolar clearance and fractional excretion of sodium and potassium in both groups. Plasma and urinary ratio of 6-keto-PGF to TxB2 increased markedly and reflected a predominant systemic and renal release of vasodilatory prostaglandins. Intraoperatively, ANF was higher in ACEIs than in control patients.

CONCLUSIONS

Long term treatment with ACE inhibitors does not influence the perioperative changes in renal hemodynamics and function. During cardiopulmonary bypass, a transient impairment in solute reabsorption is associated with renal release of vasodilatory mediators (nitric oxide and prostacyclin).

Treatment of intraoperative refractory hypotension with terlipressin in patients chronically treated with an antagonist of the renin-angiotensin system

The goal of the present study was to determine whether terlipressin, an agonist of the vasopressin system, could counteract perioperative hypotension refractory to common vasopressor therapy and to analyze its circulatory effects. We enrolled 51 consecutive vascular surgical patients chronically treated with angiotensin-converting enzyme inhibitors or antagonists of the receptor of angiotensin II, who received a standardized opioid-propofol anesthetic. Of these 51 patients, 32 had at least one episode of hypotension, which responded to epinephrine or phenylephrine. In 10 other patients, systolic arterial pressure (SAP) did not remain above 100 mm Hg for 1 min, despite three bolus doses of ephedrine or phenylephrine. In these patients, we injected a bolus of 1 mg of terlipressin, repeated twice if necessary. Hemodynamic and echocardiographic variables were recorded every 30 s over 6 min. In eight patients, arterial pressure was restored with one injection of terlipressin; in two other patients, three injections were necessary. One minute after the last injection of terlipressin, the SAP increased from 88+/-3 to 100+/-4 mm Hg and reached 117+/-5 mm Hg (P = 0.001) 3 min after the injection and remained stable around this value. This increase in SAP was associated with significant changes in left ventricular end-diastolic area (17.9+/-2 vs 20.2+/-2.2 cm2; P = 0.003), end-systolic area (8.1+/-1.3 vs 9.6+/-1.5 cm2; P = 0.004), end-systolic wall stress (45+/-8 vs 66+/-12; P = 0.001), and heart rate (60+/-4 vs 55+/-3 bpm; P = 0.001). Fractional area change and velocity of fiber shortening did not change significantly. No additional injection of vasopressor was required during the perioperative period. No change in ST segment was observed after the injection.

IMPLICATIONS

Terlipressin is effective to rapidly correct refractory hypotension in patients chronically treated with antagonists of the renin-angiotensin system without impairing left ventricular function.

Inhibitors of the renin angiotensin system: implications for the anaesthesiologist

The major long-term benefits of angiotensin-converting enzyme (ACE) inhibitors have now clearly been demonstrated in patients with arterial hypertension, cardiac insufficiency, coronary artery disease and several renal diseases. Such long-term treatment markedly alters the cardiovascular response to anaesthesia and surgery, whereas preliminary data suggest that short-term renin angiotensin system blockade might provide perioperative organ protection and improved circulatory conditions. Besides the classic view that the conversion of angiotensin I to angiotensin II is mainly due to ACE, alternative pathways have recently been identified, including cathepsin G as well as chymostatin- and aprotinin-sensitive serine proteases that are released from mastocytes and endothelial cells and which are insensitive to the effects of ACE inhibitors. These proteases are thought to contribute to tissue perfusion under hypoxic conditions and to structural remodelling. In clinical practice, ACE inhibitors may be preferred to angiotensin II receptor antagonists since the former, besides reducing angiotensin II synthesis, also lead to an accumulation of kinins (e.g. bradykinin), which have important cardio- and renal protective effects through liberation of prostacyclin and nitric oxide in endothelial cells and through stimulation of guanylate cyclase to form cyclic GMP.

Treating anesthesia-induced hypotension by angiotensin II in patients chronically treated with angiotensin-converting enzyme inhibitors

Although angiotensin II bolus administration may be used to increase blood pressure in patients chronically treated with angiotensin-converting enzyme inhibitors (ACEI) who have severe hypotension on anesthetic induction, no data are available describing its time course and its effects on the left ventricular function. Fourteen patients chronically treated with ACEI for hypertension and scheduled for vascular surgery were prospectively studied. Patients with cardiac insufficiency were excluded. A transesophageal echocardiography probe was inserted to assess systolic left ventricular function. When hypotension was observed (systolic arterial pressure [SAP] <85 mm Hg), an I.V. bolus of 2.5 microg of angiotensin II (AII) was given, and hemodynamic variables were recorded each 30 s over 5.5 min. Results are expressed as mean +/- SEM. Sixty seconds after the AII bolus injection, the SAP increased from 78 +/- 3 to 152 +/- 6 mm Hg. SAP remained higher than control until the 5th min. This was associated with significant increases in end-diastolic area (from 15.1 +/- 0.6 to 19.3 +/- 1.0 cm2, P < or = 0.001), end-systolic area (from 6.6 +/- 0.4 to 10.7 +/- 0.7 cm2, P < or = 0.001), end-systolic wall stress (from 32 +/- 0.05 to 82 +/- 7 kdynes/cm2, P < or = 0.001). In addition, a decrease in fiber-shortening velocity (from 1.1 +/- 0.05 to 0.76 +/- 0.04 circ/s, P < or = 0.05) and in fractional area change (from 0.57 +/- 0.02 to 0.44 +/- 0.02, P < or = 0.05) was observed. Heart rate did not significantly change during the study. Increases in preload and afterload were observed. However, the administration of AII causes a transient impairment in left ventricular function. We conclude that AII, given as an I.V. bolus of 2.5 microg, is effective in restoring arterial blood pressure within 60 s in patients chronically treated with ACEI.

IMPLICATIONS

Severe hypotension on anesthetic induction in patients chronically treated with angiotensin-converting enzyme inhibitors for hypertension could be treated with an I.V. bolus of 2.5 microg of angiotensin II.