Anesthesia & Co-existing Disease

Cardiopulmonary exercise testing

Cardiopulmonary Exercise Testing (CPET) is increasingly used to assess risk and optimize planning before major surgery. Deficiencies in the CPET-derived variables anaerobic threshold, peak oxygen consumption, and ventilatory efficiency for carbon dioxide are associated with poor postoperative outcomes.

This educational article seeks to enlighten on the interpretation of the ‘nine-panel plot’ and enhance understanding of the results:

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Guidelines for day‐case surgery 2019

Day case surgery continues to proliferate and is intended to be the method of choice in the majority of surgeries. It’s self-evident meaning should not be confused with 23-hour stay in the US.

This updated free paper from the Association of Anaesthetists in Britain/Ireland provides an excellent overview of the practice of ambulatory surgery.

Topics include the need for organization, leadership and governance involving physicians and non-physicians in pre-admission clinics, and selection of patients. Discussion around specific issues like obesity and obstructive sleep apnea occurs. Spinal anesthesia need not be a barrier. ‘Fitness for a procedure should relate to the patient’s functional status as determined at pre‐anaesthetic assessment, and not by ASA physical status, age or body mass index’.

Multimodal analgesia techniques including regional nerve blocks should be the norm.

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Second Generation Drug Eluting Stents and Surgery

Non-cardiac elective surgery after placement of coronary stents is performed after time guidelines delineated previously (eg. link ).

Second generation drug eluting stents were reviewed in medical records in this study. The rates of major adverse cardiac events were 17.1%, 10.0%, 0.0%, and 3.1% for patients undergoing non-cardiac surgery at 0–90, 91–180, 181–365, and ≥366 days, respectively. 

The rate of excessive surgical bleeding was 6.7% with the highest observed rate in those on dual antiplatelet therapy although not statistically significant compared to those not receiving dual antiplatelet therapy in the 7 days before surgery, although numbers were small.

The important takeaway is that 180 days (6 months) is still a reasonable minimum before elective non-cardiac surgery for those on dual antiplatelet therapy.

Full details are discussed, along with comparisons to various guidelines at the link.

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Neuroanesthesia & Critical Care Guidelines

The Society of Neuroscience in Anesthesiology and Critical Care (SNACC) guidelines and consensus statements are available in full text at the link below.

They encompass guidelines for managing patients at risk of stroke, those with external ventricular/lumbar drains, and anesthetic management of endovascular treatment of acute ischemic stroke.

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Perioperative Hypotension and Cardiovascular Events

Another study adds to the now established theme that perioperative hypotension increases cardiovascular events and does so independently of the degree of coronary artery disease.

Hypotension is defined in this study as systolic blood pressure < 90mm Hg for at least 10 mins. Other studies have also used mean arterial pressure < 65.

The nuances show the effects were additive if not multiplicative. There was insufficient evidence that perioperative hypotension may have less deleterious cardiovascular effects in patients with a lesser degree of coronary artery disease compared to greater coronary artery disease.

“These data support efforts for the prevention, monitoring, and treatment of perioperative hypotension regardless of the presence or absence of significant coronary artery disease”.

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Intraoperative Controlled Hypotension and Acute Kidney Injury

This was a retrospective study (immediate caveat!) on total hip arthroplasty under neuraxial anesthesia with intraoperative controlled hypotension (MAP < 60).

Acute kidney injury occurred in 45 (1.85%) of the 2431 patients in this cohort. Longer duration of hypotension was not associated with increased odds of postoperative AKI. Preexisting differences, such as compromised renal function, best predicted increased odds of AKI.

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The authors speculate that inadvertent and controlled hypotension may be different. Hypotension may have surgical benefits but this study should be interpreted with caution in view of the known evidence on the cardiac, renal and mortality associations ( link ).

Methylprednisolone for AKI in Cardiac Surgery

A sub study of a randomized trial finds: “Intraoperative corticosteroid use did not reduce the risk of acute kidney injury in patients with a moderate-to-high risk of perioperative death who had cardiac surgery with cardiopulmonary bypass. Our results do not support the prophylactic use of steroids during cardiopulmonary bypass surgery”.

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A previous review casts doubt on the use of steroids for various purposes in cardiac surgery, finding that they had “an unclear impact on mortality, increased the risk of myocardial injury, and the impact on atrial fibrillation should be viewed with caution given that large trials showed no effect”. link

Anesthesia and Cancer Outcome

Another meta-analysis reflecting ongoing interest in inhalational vs. total intravenous anesthesia (TIVA) and cancer outcomes.

The use of TIVA was associated with improved recurrence-free as well as overall survival in all cancer types. It was especially evident where major cancer surgery was undertaken. Breast surgery was studied most extensively.

Most studies were retrospective, with varying follow-up, demographic variations, population imbalance, cancer grade/stage differences, different surgery magnitude, and other anesthetic technique differences. It is therefore necessary to be cautious about the findings and wait for larger randomized studies to confirm what could be a major finding in favour of Propofol-based TIVA.

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Perioperative Sleep Apnea & Regional Anesthesia

This study was retrospective with unaccounting for many variables such as concomitant sedation and does not prove causation, but found even in a setting with almost universal regional anesthesia for total knee and hip arthroplasties, OSA was associated with significantly increased odds for prolonged length of stay, pulmonary and gastrointestinal complications.

It nonetheless calls for further randomized studies in such a population, as neuraxial anesthesia is often felt to be a safer option.

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Overlapping Surgeries and Outcome

It is common for surgeons to leave before the end of surgery to commence another case while more junior staff complete closure.

This retrospective study found that in common operations, overlapping surgery was not significantly associated with differences in in-hospital mortality or postoperative complication rates but was significantly associated with increased surgery length.

An exploratory subgroup analysis however suggests some caution may be appropriate for higher risk patients and CABG surgery as there were small increases in mortality and complications in that group which requires further study.

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