Wessex Intensive Care Society (WICS)

ESA 2013: Hot Topics: Last Year's Top Publications in Anaesthesia

Presented at ESA 2013 by Benedikt Pannen
Past Chairman of the ESA Scientific Committee, and Professor and Chair of the Department of Anaesthesiology at the University Hospital Düsseldorf, Germany

Summarised by Dr Adrian Wong

1. Perioperative mortality - how are we doing?
Mortality after Surgery in Europe: A 7 day cohort study
Lancet, September 22, 2012; 380: 1059-1065.
R. Pearse et al. for the EuSOS group.


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Previous work on estimating postoperative mortality in Europe showed an overall mortality rate of 1.8% (Anesthesiology 2010; 112(5): 1105-1115). This obviously varied depending on the type of surgery.

I think most of us would have read this observational study that looked at patients undergoing assessed non-cardiac surgery patients between the 4
th to 11th of April, 2011. It covered a total of 498 Hospitals in 28 European nations.

Overall, the death rate in hospital after surgery was found to be 4%, higher than many previous estimates and with a substantial degree of variation between countries. Scandinavian countries had better mortality rate compared to the Eastern European ones (UK mortality was referenced). There were obvious questions and rebuttals over the quality of data collected.

5% of patients underwent a planned admission to critical care but 73% of patients who died were not admitted to critical care at any stage after surgery, and of patients who died after admission to critical care, 43% did so after the initial episode was complete and the patients had already been discharged to a standard ward.

Discussion points
  • Mortality rate for patients undergoing non-cardiac surgery is higher than anticipated.
  • Variation in mortality rates suggest need for national and international strategies to improve care.
  • Systematic failure in the process of allocation of critical care resources.

2. Myocardial protection - do volatile anaesthetics do the job?
Randomised Comparison of Sevoflurane versus Propofol to reduce Perioperative Myocardial Ischaemia in Patients undergoing Non-Cardiac Surgery
Circulation, December 4, 2012; 126: 2696-270
G. A. L. Lurati Buse et al.


This study found no significant difference between propofol and sevoflurane in reducing myocardial ischaemia in patients undergoing non-cardiac surgery.

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A multinational study of 8351 patients undergoing non-cardiac surgery by Devereaux et al (Ann Intern Med 2011; 154: 523-528) showed that 5% of patients had a perioperative MI, and the 30-day mortality rate was higher for patients who had an MI (12%) than for those who did not (2%). The idea of preconditioning, either ischaemic or pharmacologically, is not a new one (Anaes 1976; 45: 287). Halothane decreases ST elevation in experimental dog models). Despite the paucity of robust studies, the American College of Cardiology Foundation/American Heart Association called for the use of volatile anaesthetics in their 2011 guidelines.

Volatile anesthetic-based regimens can be useful in facilitating early extubation and reducing patient recall (Myles et al., 2003; Dowd et al., 1998; Groesdonk, et al., 2010; Cheng et al., "Early," 1996). (Level of Evidence: A)

European guidelines do not. Note that the references provided by the ACCF/AHA are at least 3 years old.

More recent studies discussed by Prof Pannen –
  • Circulation 2012;126:2696-2704. RCT multicentre. Etomidate induction. Maintenance with either sevoflurane or propofol. Primary end point MI measured at day 1 and 2 postop. No difference between propofol and sevoflurane groups. No significance difference in multiple secondary end points.
  • J Cardiothorac Vasc Ana 2011;25:902-907. TIVA vs sevoflurane - no difference. Limitations - clearly not blinded. Lack of standardisation e.g. Opioid doses. Other drugs which are protective e.g. Beta blockers, statins, are exerting maximum protective effect.

Conclusion
Sevoflurane does not reduce the incidence of myocardial ischemia in high-risk patients undergoing non-cardiac surgery compared with propofol.

3. Delirium and POCD. Can we further minimise the risk?

ISPOCD1 (International Study on Post-Operative Cognitive Dysfunction) study (Lancet 1998; 351: 857-861) showed an incidence of POCD of 25.8% at 1 week and 9.9% at 3 months. Post-operative delirium has a long-term effect on cognitive function (NEJM 2012; 367: 30-39).

Bis-guided Anesthesia decreases Postoperative Delirium and Cognitive Decline J Neurosurg Anesthesiol, January 2013; 25: 33-42
M.T. Chan et al. for the CODA Trial Group

RCT in Hong Kong. BIS (40-60) guided vs routine care. Primary outcome POCD at 3 months. BIS guided group had mean BIS 53 compared to 36 in control. BIS group had less volatile or propofol administered. BIS group had lower incidence of delirium and POCD. For every 1000 patients, BIS-guided anaesthesia prevented 83 patients from suffering delirium (number needed to treat = 12).

Monitoring depth of anaesthesia in a randomized trial decreases the rate of postoperative delirium but not postoperative cognitive dysfunction
Br J Anaesth, March 28, 2013 [Epub ahead of print]
F. M. Radtke et al.

Bis guided vs routine care. Mean BIS was similar in both groups but BIS guided group spent shorter time with lower BIS less than 40. Lower incidence of delirium in BIS group.

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The Triple Low (MAP, BIS and MAC) has been shown to be associated with increased mortality risk (
Anaes 2012; 116: 1195-1203).

Conclusion
BIS reduces risk of delirium in elderly patients undergoing non-cardiac surgery NNT 12.

Adapted from the ESA 2013 Summary Newsletter
Comments

Sir Robert Macintosh Lecture (ESA 2013, Barcelona) - No patient has to die of anaesthesia

Anaesthesia and the Lung: Can Oxygen Be Harmful?
Presented at ESA 2013 by Professor Goran Hedenstierna, University Hospital, Uppsala, Sweden.

Summarised by Dr Adrian Wong

It is estimated that over 234 million anaesthetics are given across the world every year (Weiser
et al., 2008). Some studies have suggested that prolonged and sustained hypoxia occurs in up to 50% cases. (Moller et al., 1991).

Anaesthetics reduce functional residual capacity (FRC) and promote airway closure leading to hypoxia. This can be attributed to a loss of respiratory muscle tone, thus allowing the elastic forces of the lung to pull in the chest wall, reducing lung volume. Hence, there is significant atelecstasis and reduced lung compliance in both SV and IPPV. This has been shown using CT studies (Rusca
et al., 2001). Prof. Hedenstierna reminisced about scanning anaesthetised horses in the hospital CT scanner in the dead of night (he had to leave this particular hospital a few weeks later when his “experiments” were discovered).

Radiologically, 40cm H
2O pressure was needed to reinflate the collapsed lungs. 20cm H2O had minimal effect. Even with recruitment manoeuvres, the lungs will start to collapse immediately unless PEEP is applied.

Furthermore, these effects can last a few days and may not be evident on plain chest radiographs. Atelectasis is fertile breeding ground for infection in the post-operative period – this begs the question: are anaesthetists to blame for post-operative pneumonia? Post-operative pulmonary complications have been found in 2 - 20% of patients after non-cardiac surgery, and in a retrospective study of 161,000 patients after major non-cardiac surgery, pneumonia was found in 1.5% with a mortality of 21% in this group. “The goal of the anaesthetic regime should be to deliver a patient with no atelectasis to the post-operative ward and to keep the lungs open”. Using a lung-protective strategy of ventilation, it is possible to reduce the incidence of pneumonia in the post-operative period (Severgnini
et al., 2013).

Pre-oxygenation using an FiO
2 of 100% has become common practice to avoid hypoxia during the peri-induction period. However, oxygen is rapidly adsorbed behind closed airways, causing lung atelectasis and shunt. Patients who had been induced and pre-oxygenated with 100% O2 for 3 min had atelectasis in 10% of the lung area. Pre-oxygenation with 80% O2 for a similar time resulted in much less atelectasis - 2% of the lung area. Pre-oxygenation with 30% O2 caused almost no atelectasis on CT scans (Acka et al., 1999).

The Professor recommends pre-oxygenation with 100% O
2, followed by a recruitment manoeuvre (inflation to an airway pressure of 40 cm H2O for 10 seconds and to higher airway pressures in patients with reduced abdominal compliance e.g. obesity or abdominal disorders). Pre-oxygenation with 80% O2 may be sufficient in most patients with no anticipated difficulty in managing the airway, but time to hypoxaemia during apnoea decreases from mean 7 to 5 min (Edmark et al., 2001). An alternative, possibly more challenging procedure is induction of anaesthesia with CPAP/PEEP to prevent fall in FRC enabling use of 100% O2. A continuous PEEP of 7–10 cm H2O may not necessarily improve oxygenation but should keep the lung open until the end of anaesthesia. An inspired oxygen concentration of 30–40% or even less, should suffice if the lung is kept open.

The final disaster - post oxygenation. In preparation for extubation, the patient is put on an FiO2 of 100% and a suctioned catheter is passed down the endotracheal tube into the airway. All the good work done by the anaesthetist to keep the lungs open during the operation could be swiftly undone at the very end.

Prof. Hederstierna’s Top Tips
  • Pre-oxygenation with 100% O2 should be followed by a recruitment manoeuvre to reopen collapsed alveoli, or induction of anaesthesia can be done with CPAP/PEEP to maintain FRC. Pre-oxygenation with 80% O2 may be possible in the lung- healthy, non-obese patient with no anticipated difficulty in airway management, followed by a gentle inflation of the lung (shorter apnoea tolerance time but easier to open closed airways than collapsed alveoli).
  • Recruitment by inflation of the lung to an airway pressure of 40 cm H2O for 10 seconds in lung-healthy, normal-weight patients and to higher airway pressures in patients with reduced abdominal compliance (obese and patients with abdominal disorders) after pre-oxygenation with 100% O2 and every 30 min, or a continuous PEEP of 7–10 cm H2O.
  • Low inspired oxygen concentration (30–40% or even less) if no need of higher concentration.
  • High inspired oxygen concentration should only be given together with PEEP.
  • Post-oxygenation with or without a recruitment manoeuvre and with or without airway suctioning should not be performed routinely but on indication.
  • Deliver a patient with no atelectasis to the post-operative ward and keep the lung open.
References
  1. Hedenstierna G. Oxygen and anesthesia: what lung do we deliver to the post-operative ward? Acta Anaesthesiol Scand. 2012; 56(6): 675-85.
  2. Weiser et al. An estimation of global volume of surgery: a modelling strategy based on data available. Lancet 2008; 372: 139-144.
  3. Moller et al. Hypoxia during anaesthesia – an observational study. BJA 1991; 66: 437-444.
  4. Rusca M, Wicky S, Proietti S, et al. Continuous positive airways pressure prevents atelectasis formation during induction of general anaesthesia. Anesthesiology 2001; 95: A1331.
  5. Akca O, Podolsky A, Eisenhuber E, et al. Comparable postoperative pulmonary atelectasis in patients given 30% or 80% oxygen during and 2 hours after colon resection. Anesthesiology 1999; 91: 991–8.
  6. Edmark L, Enlund M, Kostova‐Aherdan K, Hedenstierna G. Atelectasis formation and apnoea tolerance after pre‐oxygenation with 100%, 80%, or 60% oxygen. Anesthesiology 2001; 95: A1330.
  7. Severgnini et al. Protective Mechanical Ventilation during General Anesthesia for Open Abdominal Surgery Improves Postoperative Pulmonary Function. Anaesthesiology 2013; 118: 1307-1321.

Adapted from the ESA 2013 Summary Newsletter


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