Canadian Cardiovascular Society Guidelines on Perioperative Cardiac Risk Assessment and Management for Patients Who Undergo Noncardiac Surgery

The Canadian Cardiovascular Society Guidelines Committee and key Canadian opinion leaders believed there was a need for up to date guidelines that used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system of evidence assessment for patients who undergo noncardiac surgery. Strong recommendations included: 1) measuring brain natriuretic peptide (BNP) or N-terminal fragment of proBNP (NT-proBNP) before surgery to enhance perioperative cardiac risk estimation in patients who are 65 years of age or older, are 45-64 years of age with significant cardiovascular disease, or have a Revised Cardiac Risk Index score ≥ 1; 2) against performing preoperative resting echocardiography, coronary computed tomography angiography, exercise or cardiopulmonary exercise testing, or pharmacological stress echocardiography or radionuclide imaging to enhance perioperative cardiac risk estimation; 3) against the initiation or continuation of acetylsalicylic acid for the prevention of perioperative cardiac events, except in patients with a recent coronary artery stent or who will undergo carotid endarterectomy; 4) against α₂ agonist or β-blocker initiation within 24 hours before surgery; 5) withholding angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker starting 24 hours before surgery; 6) facilitating smoking cessation before surgery; 7) measuring daily troponin for 48 to 72 hours after surgery in patients with an elevated NT-proBNP/BNP measurement before surgery or if there is no NT-proBNP/BNP measurement before surgery, in those who have a Revised Cardiac Risk Index score ≥1, age 45-64 years with significant cardiovascular disease, or age 65 years or older; and 8) initiating of long-term acetylsalicylic acid and statin therapy in patients who suffer myocardial injury/infarction after surgery.

Spontaneous cardiac baroreflex in humans. Comparison with drug-induced responses

We compared two methods of assessment of baroreflex sensitivity in eight supine healthy volunteers during repeated baseline measurements and various conditions of cardiac autonomic blockade. The spontaneous baroreflex method involved computer scanning of recordings of continuous finger arterial pressure and electrocardiogram to locate sequences of three or more beats in which pressure spontaneously increased or decreased, with parallel changes in pulse intervals. The mean regression slope of all these sequences during each study condition was considered to represent the mean spontaneous baroreflex slope. In the drug-induced method, sigmoidal curves were constructed from data obtained by bolus injections of phenylephrine and nitroprusside; the tangents taken at the resting pressure of each of these curves were compared with the mean spontaneous baroreflex slopes. The two methods yielded slopes that were highly correlated (r = .96, P < .001), with significant but similar intraindividual baseline variability. Atropine virtually eliminated the baroreflex slope; subsequent addition of propranolol did not alter it further. Propranolol or clonidine alone increased average baroreflex slope to the extent that they increased resting pulse interval (r = .69 to .83). The spontaneous baroreflex method provides a reliable, noninvasive assessment of human vagal cardiac baroreflex sensitivity within its physiological operating range.

The effects of perioperative beta-blockade: results of the Metoprolol after Vascular Surgery (MaVS) study, a randomized controlled trial

BACKGROUND

Patients undergoing vascular surgery comprise the highest risk group for perioperative cardiac mortality and morbidity after noncardiac procedures. Many current guidelines recommend the use of beta-blockers in all patients undergoing vascular surgery. We report a trial of the perioperative administration of metoprolol and its effects on the incidence of cardiac complications at 30 days and 6 months after vascular surgery.

METHODS

Patients undergoing abdominal aortic surgery and infrainguinal or axillofemoral revascularizations were recruited to a double-blind randomized controlled trial of perioperative metoprolol versus placebo. Patients were randomized to receive study medication, starting 2 hours preoperatively until hospital discharge or maximum of 5 days postoperatively. Primary outcome were postoperative 30-day composite incidence of nonfatal myocardial infarction, unstable angina, new congestive heart failure, new atrial or ventricular dysrhythmia requiring treatment, or cardiac death.

RESULTS

Patients were randomized to receive either metoprolol (n = 246) or placebo (n = 250). Primary outcome events at 30 days postoperative occurred in 25 (10.2%) versus 30 (12.0%) (P = .57) in metoprolol and placebo groups, respectively (relative risk reduction 15.3%, 95% CI -38.3% to 48.2%). Observed effects at 6 months were not significantly different (P = .81) (relative risk reduction 6.2%, 95% CI% -58.4% to 43.8%). Intraoperative bradycardia requiring treatment was more frequent in the metoprolol group (53/246 vs 19/250, P = .00001), as was intraoperative hypotension requiring treatment (114/246 vs 84/250, P = .0045).

CONCLUSION

Our results showed metoprolol was not effective in reducing the 30-day and 6-month postoperative cardiac event rates. Prophylactic use of perioperative beta-blockers in all vascular patients is not indicated.

Perioperative aspirin and clonidine and risk of acute kidney injury: a randomized clinical trial

IMPORTANCE

Acute kidney injury, a common complication of surgery, is associated with poor outcomes and high health care costs. Some studies suggest aspirin or clonidine administered during the perioperative period reduces the risk of acute kidney injury; however, these effects are uncertain and each intervention has the potential for harm.

OBJECTIVE

To determine whether aspirin compared with placebo, and clonidine compared with placebo, alters the risk of perioperative acute kidney injury.

DESIGN, SETTING, AND PARTICIPANTS

A 2 × 2 factorial randomized, blinded, clinical trial of 6905 patients undergoing noncardiac surgery from 88 centers in 22 countries with consecutive patients enrolled between January 2011 and December 2013.

INTERVENTIONS

Patients were assigned to take aspirin (200 mg) or placebo 2 to 4 hours before surgery and then aspirin (100 mg) or placebo daily up to 30 days after surgery, and were assigned to take oral clonidine (0.2 mg) or placebo 2 to 4 hours before surgery, and then a transdermal clonidine patch (which provided clonidine at 0.2 mg/d) or placebo patch that remained until 72 hours after surgery.

MAIN OUTCOMES AND MEASURES

Acute kidney injury was primarily defined as an increase in serum creatinine concentration from the preoperative concentration by either an increase of 0.3 mg/dL or greater (≥26.5 μmol/L) within 48 hours of surgery or an increase of 50% or greater within 7 days of surgery.

RESULTS

Aspirin (n = 3443) vs placebo (n = 3462) did not alter the risk of acute kidney injury (13.4% vs 12.3%, respectively; adjusted relative risk, 1.10; 95% CI, 0.96-1.25). Clonidine (n = 3453) vs placebo (n = 3452) did not alter the risk of acute kidney injury (13.0% vs 12.7%, respectively; adjusted relative risk, 1.03; 95% CI, 0.90-1.18). Aspirin increased the risk of major bleeding. In a post hoc analysis, major bleeding was associated with a greater risk of subsequent acute kidney injury (23.3% when bleeding was present vs 12.3% when bleeding was absent; adjusted hazard ratio, 2.20; 95% CI, 1.72-2.83). Similarly, clonidine increased the risk of clinically important hypotension. In a post hoc analysis, clinically important hypotension was associated with a greater risk of subsequent acute kidney injury (14.3% when hypotension was present vs 11.8% when hypotension was absent; adjusted hazard ratio, 1.34; 95% CI, 1.14-1.58).

CONCLUSIONS AND RELEVANCE

Among patients undergoing major noncardiac surgery, neither aspirin nor clonidine administered perioperatively reduced the risk of acute kidney injury.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01082874.

Post-discharge after surgery Virtual Care with Remote Automated Monitoring-1 (PVC-RAM-1) technology versus standard care: randomised controlled trial

OBJECTIVE

To determine if virtual care with remote automated monitoring (RAM) technology versus standard care increases days alive at home among adults discharged after non-elective surgery during the covid-19 pandemic.

DESIGN

Multicentre randomised controlled trial.

SETTING

8 acute care hospitals in Canada.

PARTICIPANTS

905 adults (≥40 years) who resided in areas with mobile phone coverage and were to be discharged from hospital after non-elective surgery were randomised either to virtual care and RAM (n=451) or to standard care (n=454). 903 participants (99.8%) completed the 31 day follow-up.

INTERVENTION

Participants in the experimental group received a tablet computer and RAM technology that measured blood pressure, heart rate, respiratory rate, oxygen saturation, temperature, and body weight. For 30 days the participants took daily biophysical measurements and photographs of their wound and interacted with nurses virtually. Participants in the standard care group received post-hospital discharge management according to the centre's usual care. Patients, healthcare providers, and data collectors were aware of patients' group allocations. Outcome adjudicators were blinded to group allocation.

MAIN OUTCOME MEASURES

The primary outcome was days alive at home during 31 days of follow-up. The 12 secondary outcomes included acute hospital care, detection and correction of drug errors, and pain at 7, 15, and 30 days after randomisation.

RESULTS

All 905 participants (mean age 63.1 years) were analysed in the groups to which they were randomised. Days alive at home during 31 days of follow-up were 29.7 in the virtual care group and 29.5 in the standard care group: relative risk 1.01 (95% confidence interval 0.99 to 1.02); absolute difference 0.2% (95% confidence interval -0.5% to 0.9%). 99 participants (22.0%) in the virtual care group and 124 (27.3%) in the standard care group required acute hospital care: relative risk 0.80 (0.64 to 1.01); absolute difference 5.3% (-0.3% to 10.9%). More participants in the virtual care group than standard care group had a drug error detected (134 (29.7%) v 25 (5.5%); absolute difference 24.2%, 19.5% to 28.9%) and a drug error corrected (absolute difference 24.4%, 19.9% to 28.9%). Fewer participants in the virtual care group than standard care group reported pain at 7, 15, and 30 days after randomisation: absolute differences 13.9% (7.4% to 20.4%), 11.9% (5.1% to 18.7%), and 9.6% (2.9% to 16.3%), respectively. Beneficial effects proved substantially larger in centres with a higher rate of care escalation.

CONCLUSION

Virtual care with RAM shows promise in improving outcomes important to patients and to optimal health system function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04344665.

Clonidine Does Not Reduce Pain or Opioid Consumption After Noncardiac Surgery

BACKGROUND

Clonidine is an α2-adrenoceptor agonist, which has analgesic properties. However, the analgesic efficacy of perioperative clonidine remains unclear. We, therefore, tested the hypothesis that clonidine reduces both pain scores and cumulative opioid consumption during the initial 72 hours after noncardiac surgery.

METHODS

Six hundred twenty-four patients undergoing elective noncardiac surgery under general and spinal anesthesia were included in this substudy of the PeriOperative ISchemia Evaluation-2 trial. Patients were randomly assigned to 0.2 mg oral clonidine or placebo 2 to 4 hours before surgery, followed by 0.2 mg/d transdermal clonidine patch or placebo patch, which was maintained until 72 hours after surgery. Postoperative pain scores and opioid consumption were assessed for 72 hours after surgery.

RESULTS

Clonidine had no effect on opioid consumption compared with placebo, with an estimated ratio of means of 0.98 (95% confidence interval, 0.70-1.38); P = 0.92. Median (Q1, Q3) opioid consumption was 63 (30, 154) mg morphine equivalents in the clonidine group, which was similar to 60 (30, 128) mg morphine equivalents in the placebo group. Furthermore, there was no significant effect on pain scores, with an estimated difference in means of 0.12 (95% confidence interval, -0.02 to 0.26); 11-point scale; P = 0.10. Mean pain scores per patient were 3.6 ± 1.8 for clonidine patients and 3.6 ± 1.8 for placebo patients.

CONCLUSIONS

Clonidine does not reduce opioid consumption or pain scores in patients recovering from noncardiac surgery.

Tetanus in developing countries: a case series and review

PURPOSE

Few anesthesiologists have expertise in the diagnosis and treatment of tetanus, a disease that remains prevalent in developing countries. We report on a series of four cases of tetanus cases recently encountered in Rwanda. We review the clinical epidemiology, pathophysiology, diagnosis and the treatment of tetanus, and provide implications for anesthesiologists and critical care physicians.

CLINICAL FEATURES

We report four cases, two involving adults who were inadequately vaccinated and experienced injuries, and two involving neonates, both of whom underwent umbilical cord transection using unsterilized equipment. All patients required tracheal intubation, and were mechanically ventilated when equipment was available. One adult and one neonate succumbed to the disease. These cases highlight the difficulties of diagnosis and management of complicated diseases in the resource-challenged health care setting of developing countries.

CONCLUSIONS

The differential diagnosis of tetanus may be confusing, and survival depends on the rapidity of treatment with antitoxin, as well as adequate supportive care. High doses of sedatives and muscle relaxants, as well as prolonged mechanical ventilation, are usually necessary. Mortality remains high, usually resulting from late respiratory failure and cardiovascular collapse, associated with autonomic instability. Anesthesiologists and critical care physicians have an important role to play in the management of these patients. Increased involvement in humanitarian health organizations, immigration from developing countries, and emergence of high risk groups in developed countries will likely result in more exposure of anesthesiologists to the complexities of this disease.

Relationship between oxygen uptake and mixed venous oxygen saturation in the immediate postoperative period

BACKGROUND

During muscular exercise, a negative correlation has been demonstrated between the value of mixed venous oxygen saturation (SvO2) and the level of muscular work, expressed at each level as the ratio of oxygen uptake (VO2) to each subject's maximal oxygen uptake (VO2max). Because the immediate postoperative period is associated with an increase in whole body oxygen demand, and in this regard resembles the effects of muscular exercise, a similar correlation may exist during this period.

METHODS

VO2max was determined in 11 patients 3-5 days before coronary artery bypass surgery. During the first 2 postoperative h, VO2 and SvO2 were monitored. VO2 was measured by indirect calorimetry and SvO2 by a fiberoptic pulmonary arterial catheter.

RESULTS

The highest postoperative value of VO2 was most often associated with visible shivering and ranged among patients from 19% to 53% of preoperatively measured VO2max. There was a highly significant negative correlation between SvO2 and the ratio VO2/VO2max. This correlation was observed when data were examined collectively (136 simultaneous determinations of the two variables) and at the individual level (10-18 determinations for each patient). The slopes and the y intercepts of individual lines of correlation were within a narrow range.

CONCLUSIONS

During the first 2 postoperative h after coronary artery bypass surgery, VO2 rarely exceeds 50% of preoperative VO2max. Assuming a stable state of myocardial function, SvO2 measurement may provide an indirect means of assessment of the "exercise test" imposed on patients recovering from general anesthesia.

Sympathovagal effects of spinal anesthesia assessed by the spontaneous cardiac baroreflex

BACKGROUND

The changes in sympathovagal balance induced by spinal anesthesia remain controversial. The spontaneous baroreflex method allows the continuous assessment of the spontaneous engagement of the cardiac baroreflex, giving an index of sympathovagal balance. The purpose of this study was to follow the effects of spinal anesthesia on spontaneous baroreflex sensitivity.

METHODS

Continuous electrocardiogram and noninvasive blood pressure were recorded in 24 patients scheduled for elective inguinal hernia repair and randomly assigned to three groups: (1) no volume loading, (2) volume loading of 15 ml/kg lactated Ringer's solution, and (3) continuous infusion of etilefrine (an ephedrine-like drug). Each patient was studied before, during, and after bupivacaine-induced spinal anesthesia (mean sensory block: T4). Spontaneous baroreflex sensitivity and parameters of time-domain analysis of heart rate variability were calculated from 30 min of recording of each period.

RESULTS

No significant change in spontaneous baroreflex slope or parameters of time-domain analysis were observed after regional anesthesia in any group. However, three patients experienced episodes of bradycardia and hypotension in the absence of a high block; these three patients showed an increase in spontaneous baroreflex sensitivity and time-domain parameters.

CONCLUSIONS

Using a noninvasive, continuous technique to estimate cardiac sympathovagal balance, no significant variation in autonomic balance induced by spinal anesthesia was observed. However, untoward episodes of bradycardia and hypotension occurred in three patients, who could not be prospectively identified by the parameters studied.

Heart rate variability following coronary artery bypass graft surgery as a function of recovery time, posture, and exercise

This study examined the claim made by Niemela et al. (1992) that the decline in heart rate variability after coronary artery bypass graft surgery is irreversible. We tested six women and 16 men six and 12 weeks postoperative in three postures: in the supine position, in the standing position, and during low-intensity steady-state exercise. Beat-by-beat arterial blood pressure and electrocardiographic R–R interval data were collected continuously for 10 min in each condition. R–R interval data were analyzed with spectral analysis; baroreflex data were analyzed using the sequence method. Our results show that the indices of parasympathetic modulation improved over time, as seen by an | increased spontaneous baroreflex sensitivity and parasympathetic indicator, that both indices were affected by posture, and that spontaneous baroreflex sensitivity was also affected by low-intensity exercise. The effects of posture are consistent with attenuated responses of healthy older subjects to orthostatic stress. Similarly, the effects of low-intensity exercise are consistent with findings in healthy subjects. We found that spontaneous baroreflex sensitivity declined during exercise, whereas, in healthy subjects, this is maintained during low-intensity steady-state exercise. Our results of significant functional recovery between six and 12 weeks postoperative suggest that at least some of the autonomic dysfunction following surgery is temporary. Previously, no such duration of study has lasted longer than four or six weeks following cardiac surgery, which may not have been long enough to show significant functional restoration in heart rate variability.Key words: heart rate variability, spontaneous baroreflex sensitivity, CABG surgery, posture, exercise.

Adverse event assessment and reporting in trials of newer treatments for post-operative pain

BACKGROUND

Assessment and reporting of adverse events (AEs) in studies of perioperative interventions is critical given the potential for unintended and preventable iatrogenic morbidity and mortality. This focused review evaluated the quality of AE assessment and reporting in acute post-operative pain treatment trials. Since older analgesics (e.g., opioids, NSAIDs) already have a well-characterized safety profile, we concentrated on trials of pregabalin and gabapentin as a representative sample of studies where the perioperative safety profile was relatively unknown.

METHODS

We reviewed primary reports of trials of pregabalin and gabapentin for treatment of acute post-operative pain for: (1) adherence to the 10 recommendations from the 'CONSORT Extension for Harms,' (2) AE assessment method, (3) timing of AE assessment and reporting, and (4) assessment and reporting of AE severity.

RESULTS

We identified 31 trials of pregabalin and 59 of gabapentin. The median number of CONSORT harms recommendations that were satisfied was 7 of 10. The most common (41%) method of AE assessment was direct questioning about specific AEs by investigators. However, AE assessment method was not described in 18% of trials. AE assessments were reported for specified perioperative time points in only 24% of trials. Of greatest concern, no AE data were reported whatsoever in 8 of the included publications.

CONCLUSIONS

Considerable widespread improvements are needed in AE reporting for post-operative pain treatment trials. In addition to heightened awareness among clinical investigators, mandatory journal editorial policies may further facilitate improvements in safety assessment and reporting.

Spontaneous baroreflex sensitivity after coronary artery bypass graft surgery as a function of gender and age

The effects of coronary artery bypass graft (CABG) surgery on spontaneous baroreflex (SBR) sensitivity and heart rate variability were examined in 11 women and 23 men preoperatively and 5 days postoperatively. Electrocardiograph R–R interval and beat-by-beat arterial blood pressure data were collected continuously for 20 min in the supine and standing postures. Coarse graining spectral analysis was performed on the heart rate variability data. Spontaneous baroreflex sensitivity declined after surgery with a differential influence of gender. Men showed a decrease in SBR slope following surgery, with a greater decrease in the standing posture; the parasympathetic (PNS) indicator was lower postoperatively and in the standing posture; the reduction in low-frequency (LF) power was greater for the younger men. In women, the PNS indicator was lower in the standing posture. Both men and women showed a decrease in high-frequency power following CABG surgery, which decreased the sensitivity of the short-term cardiac control mechanisms that modulate heart rate, with the greater effects occurring in men. The reduction in SBR sensitivity indicates that the ability of the cardiovascular system to respond rapidly to changing stimuli was compromised. The decline in the PNS indicator implies that patients were vulnerable to the risks of myocardial ischemia, sympathetically mediated cardiac dysrhythmias, and sudden cardiac death.Key words: spectral analysis, spontaneous baroreflex sensitivity, CABG surgery, gender, age, posture.

Barriers and facilitators to postoperative pain management in Rwanda from the perspective of health care providers: A contextualization of the theory of planned behavior

AIMS

Identify opportunities to improve knowledge translation for post-operative pain management in Rwanda by exploring clinician and environmental factors affecting this practice.

METHODS

The theory of planned behavior (TPB) guided development of a questionnaire to measure intent to assess and treat postoperative pain. Focus groups and individual interviews were used to contextualize the final questionnaire and generate questions related to pain management practice. Health care providers from two Rwandan teaching hospitals involved in postoperative pain management completed the TPB questionnaire in May 2015. TPB subscale scores were analyzed to identify demographic and practice characteristics associated with intention to treat pain. The general linear model was used to test effect of attitudes, subjective norms, and perceived control on behavioral intent to treat pain.

RESULTS

Forty-six percent of participants (N = 131) had training in acute pain management, 56% used a pain protocol, and 74% used pain scales. Tramadol (78%), morphine (79%), and paracetamol (75%) were used most often to treat pain. Drug availability was the most frequently reported barrier to treating pain. Though intention to treat pain was high, only attitudes and perceived control about assessing pain were associated with intention to treat pain. The theme of fear of the adverse effects of pain medications was consistent across focus groups and interviews in both sites.

CONCLUSIONS

System and knowledge barriers exist: interventions to address these barriers may lead to improved postoperative pain care. Further validation of the TPB questionnaire is required to address cultural and language factors specific to the Rwandan context.

Long-term opioid use in seniors following hip and knee arthroplasty in Ontario: a historical cohort study

PURPOSE

Canadian seniors who undergo hip and knee arthroplasty often experience significant postoperative pain, which could result in persistent opioid use. We aimed to document the impact of preoperative opioid use and other characteristics on postoperative opioid prescriptions in elderly patients following hip and knee replacement before widespread dissemination of opioid reduction strategies.

METHODS

We conducted a historical cohort study to evaluate postoperative opioid use in patients over 65 yr undergoing primary total hip and knee replacement over a ten-year period from 1 April 2006 to 31 March 2016, using linked de-identified Ontario administrative data. We determined the use of preoperative opioids and the duration of postoperative opioid prescriptions (short-term [1-90 days], prolonged [91-180 days], chronic [181-365 days], or undocumented).

RESULTS

The study included 49,638 hip and 85,558 knee replacement patients. Eighteen percent of hip and 21% of knee replacement patients received an opioid prescription within 90 days before surgery. Postoperatively, 51% of patients filled opioid prescriptions for 1-90 days, while 24% of hip and 29% of knee replacement patients filled prescriptions between 6 and 12 months, with no impact of preoperative opioid use. Residence in long-term care was a significant predictor of chronic opioid use (hip: odds ratio [OR], 2.64; 95% confidence interval [CI], 1.93 to 3.59; knee: OR, 2.46; 95% CI, 1.75 to 3.45); other risk factors included female sex and increased comorbidities.

CONCLUSION

Despite a main goal of joint arthroplasty being relief of pain, seniors commonly remained on postoperative opioids, even if not receiving opioids before surgery. Opioid reduction strategies need to be implemented at the surgical, primary physician, long-term care, and patient levels. These findings form a basis for future investigations following implementation of opioid reduction approaches.

Aspirin and clonidine in non-cardiac surgery: acute kidney injury substudy protocol of the Perioperative Ischaemic Evaluation (POISE) 2 randomised controlled trial

INTRODUCTION

Perioperative Ischaemic Evaluation-2 (POISE-2) is an international 2×2 factorial randomised controlled trial of low-dose aspirin versus placebo and low-dose clonidine versus placebo in patients who undergo non-cardiac surgery. Perioperative aspirin (and possibly clonidine) may reduce the risk of postoperative acute kidney injury (AKI).

METHODS AND ANALYSIS

After receipt of grant funding, serial postoperative serum creatinine measurements began to be recorded in consecutive patients enrolled at substudy participating centres. With respect to the study schedule, the last of over 6500 substudy patients from 82 centres in 21 countries were randomised in December 2013. The authors will use logistic regression to estimate the adjusted OR of AKI following surgery (compared with the preoperative serum creatinine value, a postoperative increase ≥26.5 μmol/L in the 2 days following surgery or an increase of ≥50% in the 7 days following surgery) comparing each intervention to placebo, and will report the adjusted relative risk reduction. Alternate definitions of AKI will also be considered, as will the outcome of AKI in subgroups defined by the presence of preoperative chronic kidney disease and preoperative chronic aspirin use. At the time of randomisation, a subpopulation agreed to a single measurement of serum creatinine between 3 and 12 months after surgery, and the authors will examine intervention effects on this outcome.

ETHICS AND DISSEMINATION

The authors were competitively awarded a grant from the Canadian Institutes of Health Research for this POISE-2 AKI substudy. Ethics approval was obtained for additional kidney data collection in consecutive patients enrolled at participating centres, which first began for patients enrolled after January 2011. In patients who provided consent, the remaining longer term serum creatinine data will be collected throughout 2014. The results of this study will be reported no later than 2015.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01082874.

Preoperative beta blocker use associated with cerebral ischemia during carotid endarterectomy

PURPOSE

Cerebral ischemia is a known complication of carotid cross-clamping during carotid endarterectomy. Selective intraluminal shunting for cerebral protection is not always effective and carries risks. The purpose of this study was to identify potentially modifiable risk factors for intraoperative cerebral ischemia and shunting during carotid endarterectomy.

METHODS

We performed an historical case-control chart review of primary carotid endarterectomies with electroencephalographic (EEG) monitoring and selective shunting. Randomized controls and cases that showed ischemic EEG changes and required shunting were matched by year of surgery and the presence or absence of a contralateral carotid occlusion. Detailed perioperative data were collected for all cases. Results were analyzed using the Mantel-Haenszel test, analysis of variance, and a multivariate logistic regression model.

RESULTS

Of 523 charts screened, 69 patients had experienced evidence of cerebral ischemia on clamping of the carotid and required shunting. These patients were more likely than their matched controls to have been receiving regular preoperative beta blockers (33/69 vs 18/69, respectively; P = 0.01; odds ratio [OR] 2.5; 95% confidence interval [CI] 1.2 to 5.1). Ipsilateral moderate carotid stenosis (60-80%) was also associated with increased risk. An adjusted multivariate regression model estimated an OR of 3.6 (95% CI 1.5 to 8.9; P = 0.005) for the association between use of a beta blocker and shunting. Intraoperative hemodynamic values were similar for the shunt and control groups as well as for patients receiving and not receiving preoperative beta blockers.

CONCLUSION

The current study found an association between regular preoperative use of beta blockers and intraoperative cerebral ischemia in patients undergoing carotid endarterectomy. This effect did not relate to intraoperative hemodynamics.

Post Discharge after Surgery Virtual Care with Remote Automated Monitoring Technology (PVC-RAM): protocol for a randomized controlled trial

BACKGROUND

After nonelective (i.e., semiurgent, urgent and emergent) surgeries, patients discharged from hospitals are at risk of readmissions, emergency department visits or death. During the coronavirus disease 2019 (COVID-19) pandemic, we are undertaking the Post Discharge after Surgery Virtual Care with Remote Automated Monitoring Technology (PVC-RAM) trial to determine if virtual care with remote automated monitoring (RAM) compared with standard care will increase the number of days adult patients remain alive at home after being discharged following nonelective surgery.

METHODS

We are conducting a randomized controlled trial in which 900 adults who are being discharged after nonelective surgery from 8 Canadian hospitals are randomly assigned to receive virtual care with RAM or standard care. Outcome adjudicators are masked to group allocations. Patients in the experimental group learn how to use the study's tablet computer and RAM technology, which will measure their vital signs. For 30 days, patients take daily biophysical measurements and complete a recovery survey. Patients interact with nurses via the cellular modem-enabled tablet, who escalate care to preassigned and available physicians if RAM measurements exceed predetermined thresholds, patients report symptoms, a medication error is identified or the nurses have concerns they cannot resolve. The primary outcome is number of days alive at home during the 30 days after randomization.

INTERPRETATION

This trial will inform management of patients after discharge following surgery in the COVID-19 pandemic and offer insights for management of patients who undergo nonelective surgery in a nonpandemic setting. Knowledge dissemination will be supported through an online multimedia resource centre, policy briefs, presentations, peer-reviewed journal publications and media engagement.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT04344665.

Unusual sinus arrhythmia

A juxtaposition of long and short RR intervals was observed in 2 hypertensive patients recovering from major surgery under spontaneous ventilation. Sinus rhythm was ascertained throughout the recording. These oscillations could not be linked one-to-one to ventilatory cycles.

Interscalene Block in an Anesthetized Adult with Hypertrophic Obstructive Cardiomyopathy Undergoing Clavicle Fracture Reduction

Whether regional anesthesia procedures should be performed in heavily sedated/anesthetized adults remains controversial. One of the purported advantages of performing regional nerve blocks in conversant patients is early warning against major nerve injury and, arguably, early detection of local anesthetic systemic toxicity. A 60-year-old man with hypertrophic obstructive cardiomyopathy (HOCM) underwent a clavicle fracture repair under general anesthesia. Intraoperative transesophageal echocardiography revealed dynamic left ventricular outflow track obstruction and systolic anterior motion of the posterior mitral valve leaflet. In part based on such echo findings, he received an ultrasound-guided interscalene plus a superficial cervical plexus block for postoperative analgesia prior to emergence from general anesthesia. Given the lack of robust data on the safety of ultrasound-guided regional techniques in heavily sedated/anesthetized adults, we use the example of echographic evidence of significant HOCM to argue for a pragmatic and individualized approach when faced with unusual situations in which the pros of such an approach may outweigh the cons - in this case for performing an interscalene block on an anesthetized adult.

Association between postsurgical pain and heart rate variability: protocol for a scoping review

INTRODUCTION

Surgical interventions can elicit neuroendocrine responses and sympathovagal imbalance, ultimately affecting cardiac autonomic function. Cardiac complications account for 30% of postoperative complications and are the leading cause of morbidity and mortality following non-cardiac surgery. One cardiovascular parameter, heart rate variability (HRV), has been found to be predictive of postoperative morbidity and mortality. HRV is defined as variation in time intervals between heartbeats and is affected by cardiac autonomic balance. Furthermore, altered HRV has been shown to predict cardiovascular events in non-surgical settings. In multiple studies, experimentally induced pain in healthy humans leads to reduced HRV suggesting a causal relationship. In a different studies, chronic pain has been associated with altered HRV, however, in the setting of clinical pain conditions, it remains unclear how much HRV impairment is due to pain itself versus autonomic changes related to analgesia. We aim to review the available evidence describing the association between postsurgical pain and HRV alterations in the early postoperative period.

METHODS AND ANALYSIS

We will conduct a scoping review of relevant studies using detailed searches of MEDLINE and EMBASE, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. Included studies will involve participants undergoing non-cardiac surgery and investigate outcomes of (1) measures of pain intensity; (2) measures of HRV and (3) statistical assessment of association between #1 and #2. As secondary review outcomes included studies will also be examined for other cardiovascular events and for their attempts to control for analgesic treatment and presurgical HRV differences among treatment groups in the analysis. This work aims to synthesise available evidence to inform future research questions related to postsurgical pain and cardiac complications.

ETHICS AND DISSEMINATION

Ethics review and approval is not required for this review. The results will be submitted for publication in peer-reviewed journals.

The Cost Implications of Dabigatran in Patients with Myocardial Injury After Non-Cardiac Surgery

BACKGROUND

The Management of Myocardial Injury after Non-Cardiac Surgery (MANAGE) trial demonstrated that dabigatran 110 mg twice daily was more effective than placebo in preventing the primary composite outcome of vascular mortality, non-fatal myocardial infarction, non-hemorrhagic stroke, peripheral arterial thrombosis, amputation and symptomatic venous thromboembolism in patients with myocardial injury after non-cardiac surgery (MINS). The cost implications of dabigatran for this population are unknown but are important given the significant clinical implications.

METHODS

Hospitalized events, procedures, and study and non-study medications were documented. We applied Canadian unit costs to healthcare resources consumed for all patients in the trial, and calculated the average cost per patient in Canadian dollars for the duration of the study (median follow-up of 16 months). A sensitivity analysis was performed using only Canadian patients, and subgroup analyses were also conducted.

RESULTS

The total study cost for the dabigatran group was $9985 per patient, compared with $10,082 for placebo, a difference of - $97 (95% confidence interval [CI] - $2128 to $3672). Savings arising from fewer clinical events and procedures in the dabigatran 110 mg twice-daily group were enough to offset the cost of the study drug. In Canadian patients, the difference was $250 (95% CI -$2848 to $4840). Both differences were considered cost neutral. Dabigatran 110 mg twice daily was cost saving or cost neutral in many subgroups that were considered.

CONCLUSION

Dabigatran 110 mg twice daily was cost neutral for patients in the MANAGE trial. Our cost findings support the use of dabigatran 110 mg twice daily in patients with MINS.

TRIAL REGISTRATION

ClinicalTrials.gov identifier number NCT01661101.