Eur J Anaesthesiol 2014; 31:388–394

CORRESPONDENCE Waiting for Godot An analysis of 2622 operating room turnover times Dietrich Doll, Katharina Wieferich, Thomas Erhart and Christian Hoenemann From the Department of Surgery, Marienhospital Vechta, Akademisches Lehrkrankenhaus der Medizinischen Hochschule Hannover (DD, TE), Vechta Institute for Research (VIFF e.V.) (DD, KW), Department of Anaesthesiology, Marienhospital Vechta, Akademisches Lehrkrankenhaus der Medizinischen Hochschule Hannover, Vechta, Germany (CH) Correspondence to Dietrich Doll, MD, PhD, Department of Surgery, Marienhospital Vechta, Akademisches Lehrkrankenhaus der Medizinischen Hochschule Hannover, Marienstr. 6-8, D-49377 Vechta, Germany Tel: +49 1723 585454; fax: +49 4441 99 1360; e-mail: [email protected] Published online 12 March 2014

Editor, Surgical theatre time is precious, and waiting time between surgical procedures is seen as wasted time. Thus, hospital managers increasingly intervene to minimise it.1,2 Most often, the start of the first procedure is the focus of interest.3–5 Less often, waiting times between operations (changeover time) are analysed. The first waiting time of the day is time taken to prepare the operating room, followed by multiple turnover times, which include resupply logistics, cleaning, disinfection and patient transfer, which need to be orchestrated. Are first and following turnover times influenced by the same factors, or are they independent factors? Analysing 2622 changing times (first waiting time and turnover times) in a 310-bed hospital between 1 January 2012 and 4 April 2012, we focused on ‘suture-to-cut’ times, also addressed as ‘nonoperative time’, which depict a longer interval than the Anglo-Saxon ‘wheelin-wheel-out time’. We found that the mean turnover time was 0.63  0.42 h (range 0 to 3.9). Forty six percent of all turnover times were less than 30 min, 65% were less than 36 min and 75% were less than 42 min (median 34 min). There was no extended waiting time in complex surgical procedures, refuting any anaesthesiological ‘tubingand-wiring’ delay. There was no significant additional further delay following timely procedures up to 1.5 h owing to increased tiredness of either surgeon or anaesthetist, tested by correlating duration of surgical procedure with the nonoperative time following the procedure, indicating a steady and efficient workflow (Spearman r ¼ 0.17; increase ¼ 0.018). If this effect

was compared for the 10 surgeons who performed most operations with procedures more than 1.5 h, there was a small, though significant, prolonged waiting time compared with shorter operations (median, 5.5 min; P ¼ 0.0027). Waiting time before and after surgery correlated in a highly significant manner (P < 0.0001), indicating an ‘operation room consistency factor’ attributable to factors not analysed here. Communication is of paramount importance in turnover times. If the next operation does not need a surgical change (same surgeon), waiting time between operations is lowest. If a change of surgeon occurs within a department, waiting time is significantly higher. Even longer waiting times occurred when a surgeon from a different department undertook the next procedure (P < 0.0001, Kruskal–Wallis). Larger surgical teams needed a longer time to prepare (0.54 to 0.87 h with 1 to 4 surgeons; P < 0.0001 Kruskal–Wallis). Time of day seemed to be an important (if not the most powerful) factor concerning turnover time (Fig. 1). While morning waiting and turnover times were 0 to 0.4 h, they increased over the day up to 0.7 to 0.9 h in the afternoon (P ¼ 0.0025; two-tailed). It may be speculated that this effect is because of increasing tiredness, fatigue or skills being worn out. There was no obvious time step around shift change of nurses. A similar ‘fatigue’ effect during the week between Monday and Friday was not seen. Interestingly, turnover times seem to decrease with operation volume per department, but this small tendency was far outweighed by interdepartmental differences. Turnover times are expensive, but to a certain extent they are inevitable and unavoidable, enabling anaesthesiological, surgical and nursing preparations. Our brief study, analysing 2622 datasets, showed that there are periodic changes during daytime that have not been described before. Indeed, Masursky et al.6 found that an increased turnover time occurred in the afternoon, and that this could be attributed to nurse shift changes. These effects of nurse shift changes were not seen in our small dataset. Nevertheless, we expected to find a similar effect because of change from septic operations at the end of the operating lists to clean operations that were scheduled later during the day, creating a need for operating room disinfection before continuing. Interestingly, turnover time around 4 p.m. was shorter than the turnover time at 2 and 3 p.m. (Fig. 1). Is it the proximity to the approaching leisure time which enhances efficiency? Comparing our crude turnover time numbers with those of Masursky et al.,6 their median operating room turnover

0265-0215 ß 2014 Copyright European Society of Anaesthesiology

Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.

Correspondence

Fig. 1

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Daytime changes of waiting time before operation (P ¼ 0.0025; twotailed).

Change of surgeon as time factor for delay between operations (P < 0.0001; Kruskal–Wallis).

time was 33 min. This compares well with our median turnover time of 34 min, although their turnover time was the difference between wheel-out and wheel-in. We used the suture-to-cut time traditionally used in Germany, which included all procedures between skin closure of one patient to incision in the next patient (dressing the patient, cleaning and kitting up the operating room, scrubbing and draping the patient).

communication gaps arise, which can be intradepartmental or between departments.

The influence of patient characteristics, anaesthetists, surgeons and nursing personnel has not been included in our investigation; thus, a lot of potential cofactors still remain to be unveiled. Nevertheless, this small study provides an interesting insight into turnover times and the characteristics they seem to follow. The daily increase of turnover time due to tiredness does not continue after a night of recovery, and begins at a lower level, as turnover times for the next day are seen starting small again. Otherwise, an increase in turnover time over the week would have been seen. It seems that overnight regeneration is sufficient even after a hard working day. Turnover times are neither evil nor good, as they seem to follow certain principles. Some of these have been outlined in this small study. Short turnover times and speed need communication to complete a large surgical team, change surgeons or change departments (P < 0.0001; Kruskal–Wallis; Fig. 2). Small departments are not slower and they do not lack routine. Motivation seems to be pivotal, as incentives like money have no positive influence on turnover times.7 Waiting times for a single surgeon or the surgical team can be minimised with a simple trick, that teams should be planned for consecutive operations as far as possible on the same day.8 A respected operating room manager could fill in if

Turnover times mirror a complex teamwork effort, and thus indicate how effective and team-orientated wards, anaesthesiology, nursing and technical staff, and surgeons are willing to work together. With motivation and communication, turnover times can be kept low within the limits of the outlined periodic changes.

Acknowledgements related to this article Assistance with the letter: none. Financial support and sponsorship: none. Conflicts of interest: none.

References 1 2 3

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Dexter F, Epstein RH. Typical savings from each minute reduction in tardy first case of the day starts. Anesth Analg 2009; 108:1262–1267. Dexter F. Is time on first-case starts well spent? OR Manager 2010; 26:22– 24. Ernst C, Szczesny A, Soderstrom N, et al. Success of commonly used operating room management tools in reducing tardiness of first case of the day starts: evidence from German hospitals. Anesth Analg 2012; 115:671– 677. Unger J, Schuster M, Bauer K, et al. Time delay in beginning first OR positions in the morning. Anaesthesist 2009; 58:293–298; 300. Schuster M, Pezella M, Taube C, et al. Delays in starting morning operating lists: an analysis of more than 20 000 cases in 22 German hospitals. Deutsches A¨rzteblatt 2013; 110:237–242. Masursky D, Dexter F, Isaacson SA, Nussmeier NA. Surgeons’ and anesthesiologists’ perceptions of turnover times. Anesth Analg 2011; 112:440–444. Masursky D, Dexter F, Garver MP, Nussmeier NA. Incentive payments to academic anesthesiologists for late afternoon work did not influence turnover times. Anesth Analg 2009; 108:1622–1626. Wachtel RE, Dexter F. Reducing tardiness from scheduled start times by making adjustments to the operating room schedule. Anesth Analg 2009; 108:1902–1909. DOI:10.1097/EJA.0000000000000059

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390 Correspondence

Is it useful to book ICU beds in advance?

(25%). Overall, therefore, only 20 of 131 requests (26%) resulted in an actual admission to HDUs/ICUs.

Xin Y. Chen, Shahla Siddiqui and Suk F. Yap

During the study period, 90 patients (80%) were admitted to the HDU and 36 patients (20%) to the surgical ICU. Sixty-six elective patients (73%) and 24 emergency patients were admitted to the HDU and 12 elective patients (33%) and 24 emergency patients (66%) to the ICU. Unplanned admission rate to HDU/ICU of elective patients was 6% (n ¼ 7).

From the Department of Anaesthesia, Khoo Teck Puat Hospital, Singapore, Singapore Correspondence to Shahla Siddiqui, MBBS, DABA, FCCM, Department of Anaesthesia, Khoo Teck Puat Hospital, 90 Yishun Central, Singapore 768828, Singapore Tel: +65 97966257; e-mail: [email protected] Published online 8 April 2014

Editor, Postoperative care in monitored units with high staffing such as recovery rooms, high dependency units (HDU) or intermediate care units and intensive care units (ICU) is important to prevent complications and to treat potential complications early. However, the number of beds in such units in most hospitals is limited because of the economic burden of such structures for a hospital. The three aims of this 1-month audit were to investigate: the rate of preoperative requests of beds in the HDU and ICU for surgical patents; the rate of actual admission following a request; and the rate of unplanned admission to the HDU and ICU for surgical patients with and without requests. The audit was performed in a tertiary public hospital with 500 beds which undertakes 3000 anaesthesiological interventions per year (2012). For the immediate postoperative care, our hospital has seven beds in the recovery room, six beds in the HDU and eight beds in surgical ICU. HDU and the surgical ICU are managed by the same staff. The preoperative requests for postoperative HDU/ICU were made by surgeons and anaesthesiologists. These requests were double checked by an ICU consultant before acceptance. The audit was performed from 6 May to 5 June 2013. During the study period, 660 patients were operated on (410 elective (62%) and 250 emergency patients (37%)). Eighty of 410 elective patients and 51 of 250 emergency postoperative patients had a request of beds in the HDU and ICU. This equates to a total of 131 requests 92% from the elective operating program and 8% from the emergency department. Sixty-three percent of all (emergency and elective) requests (n ¼ 82) were accepted and 37% were not accepted by the consultant of the ICU (n ¼ 49). The reasons for non-acceptance were as follows: 35 for no indication for HDU/ICU bed (73%) after surgical intervention; 7% for cancelled surgery; and 20% for lack of beds in ICU/HDU. Sixty-six percent of patients with no acceptance were elective (n ¼ 32) and 33% were emergent (n ¼ 16). Surprisingly, only 20 patients with acceptance were finally admitted to HDU/ICU

The main result of this audit was that the precise prediction of the need of postoperative admission to HDUs/ICU was very difficult even with a two-step decision model and that the booking system was not satisfactory. Why was the preoperative prediction so imprecise? First, the preoperative risk stratification of patients’ conditions including comorbidity, healthcare dependency and frailty was probably incomplete. Furthermore, severity of surgery was not estimated systematically with standardised preoperative criteria. Second, there was no consensus on admission criteria between preoperative decision makers and the ICU consultant; this was probably related to incomplete preoperative data and different professional experience. Third, discharge criteria of the recovery room may not have been optimal, which could explain the unplanned admission rates to HDU/ICU. In a highquality perioperative care system, a second risk stratification should be performed immediately postoperatively to avoid unplanned admission to HDU/ICU. An improvement initiative should now be performed replacing eminency-driven admissions by criteria or guideline-driven admissions to HDU/ICU and the discharge criteria of recovery room should be adapted. It is highly probable that such an improvement initiative would increase availability of beds with monitored care and potentially decrease postoperative complications including mortality. A successful improvement project would also need regular feedback from all decision makers in the perioperative patient flow with our three key parameters (rate of preoperative requests of beds in the HDU/ICU rate of actual admission with a request and rate of unplanned admission to HDU/ICU in conjunction with an outcome parameter such as inhospital 30-day mortality and length of hospital stay.

Acknowledgements relating to this article Assistance with the letter: none Financial support and sponsorship: none Conflicts of interest: none. DOI:10.1097/EJA.0000000000000079

Eur J Anaesthesiol 2014; 31:388–394 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.

Correspondence

Transversus abdominis plane block in inguinal hernia repair Jens Børglum, Katrine Tanggaard, Bernhard Moriggl and John G. McDonnell From the Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital: Bispebjerg, Copenhagen, Denmark (JB, KT), Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Innsbruck Medical University, Austria (BM), and Department of Anesthesia, Clinical Sciences Institute, National University of Ireland, Galway, Ireland (JGM) Correspondence to Jens Børglum, MD, PhD, Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital, Bispebjerg, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark Tel: +45 3070 0120; fax: +45 3531 3958, e-mail: [email protected] Published online 6 May 2014

Editor, We read with great interest the very interesting and thorough article by Petersen et al.1 on the effect of either transversus abdominis plane (TAP) block or local anaesthetic infiltration in inguinal hernia repair. However, we believe that there are some important aspects that need clarification. These are with regard to the choice of technique, knowledge of anatomy and results from previous studies. Petersen et al.1 found that ultrasound-guided TAP blocks did not reduce postoperative pain after inguinal hernia repair. They mention correctly that local anaesthetic, guided by the aid of ultrasound or anatomical landmarks, is injected into the transversus abdominis fascial plane, wherein the nerves from T6 to L1 are located. Referring to the initial clinical trials by McDonnell et al.2,3 they mention that the analgesic effect of a TAP blockade has been reported to last up to 24 h postoperatively. However, according to their description in the Methods section, Petersen et al.1 performed unilateral ultrasound-guided TAP blocks with the transducer placed transversely in the mid-axillary line between the iliac crest and the costal margin, although it remains clear that McDonnell et al.2,3 performed landmark-based TAP blocks more laterally and posterior at the triangle of Petit. Petersen et al.1 also mention in the Discussion section that they used the ultrasound-guided posterior approach at the umbilical level to perform the TAP block, which they hypothesised might produce a variable involvement of L1. The mentioning of a posterior approach in relation to their mid-axillary ultrasound-guided TAP block is not entirely correct. Thus, the description could be interpreted as somewhat confusing regarding the placement of the TAP blocks. Using MRI to examine the resulting spread from various truncal blocks, Carney et al.4 found the contrast solution to extend anteriorly to the mid-axillary line inferiorly to the iliac crest and superiorly to the costal margin within the TAP when they performed the landmark-based TAP block, that is double loss of resistance through the triangle of Petit. In addition, Carney et al.4 found contrast enhancement of the paravertebral spaces

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from T4 at the highest level, to L2 at the lowest level. They also examined the mid-axillary ultrasound-guided TAP block approach and they found that this technique produced a different contrast pattern anteriorly within the TAP. They concluded that the importance of these findings lies in the fact that the associated analgesia was likely to depend on the extent of spread of local anaesthetic within the TAP. It was also concluded that the mid-axillary ultrasound-guided TAP block approach provided for a relatively limited duration of analgesia compared with that resulting from the landmark-based TAP block at the triangle of Petit. Petersen et al.1 correctly comment that the possible superiority of one TAP block technique compared with another remains unanswered. We have previously published on the time dependent distribution pattern of the injected local anaesthetic resulting from the mid-axillary ultrasound guided TAP block with a similar volume (30 ml ropivacaine 0.375%).5 Using MRI, we found that the local anaesthetic injected with this approach never reached below to the anterior superior iliac spine. Interestingly, even after 6 h following the administration of the blocks, we were unable to detect dermatomal anaesthesia caudad to Th12. Thus, we never achieved dermatomal anaesthesia at the level of L1 with the mid-axillary ultrasound-guided TAP approach.5 Our findings seem to corroborate well with the detailed anatomical descriptions by Rozen et al.6 regarding the L1 branch. Rozen et al.6 described that a main division of L1, the ilioinguinal nerve, always entered the neurovascular plane at the level of the anterior superior iliac spine, consistent with the described literature. Rozen et al.6 performed cadaveric dissections of the anterolateral abdominal wall, and they consistently found the L1 branch at the level of the anterior superior iliac spine and medial to this point, which might well explain the inability of mid-axillary ultrasound-guided TAP blocks to anaesthetise this nerve. We believe that the best way to produce a consistent block of the L1 in relation to inguinal hernia repair with a mesh using the Lichtenstein technique is to block this nerve selectively guided by ultrasound close to and medial to the anterior superior iliac spine. The injection should be made from the lateral to the medial direction between the internal oblique and the transversus abdominis muscles wherein the L1 nerve branches run with the deep circumflex iliac artery in the neurovascular plane.7 Employing this technique for inguinal hernia repair with a mesh using the Lichtenstein technique, we have previously published results showing a significant reduction in pain scores at mobilisation (P < 0.001) and rest (P < 0.005) recorded in the active (bupivacaine 0.5%) group compared with the placebo group (isotonic saline).7 This significant effect was evident upon arrival in the postanaesthesia care unit and again after 30 min. Pain at rest was similarly reduced in the bupivacaine group at the time of discharge (P < 0.017). Further, in the

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392 Correspondence

bupivacaine group, we also reported significantly fewer patients (P < 0.05) with severe (numerical rating scale >5) and moderate (numerical rating scale >3) pain at mobilisation and rest, respectively. Opioid consumption and time spent in the postanaesthesia care unit were not significantly different between groups at any time. In addition, we were unable to detect any significant reduction in pain scores when we conducted telephonic interviews 24 and 48 h postoperatively. It would seem that in order to provide for a more prolonged analgesic effect following inguinal hernia repair, a more posterior approach, as compared with the mid-axillary technique, must be performed to ensure spread of the local anaesthetic to the paravertebral space. Moreover, if a more anterior and medial approach is chosen for this specific surgical procedure, then the direct ultrasound-guided ilioinguinal/iliohypogastric nerve block technique should probably be considered.

Reply to: transversus abdominis plane block in inguinal hernia repair

Acknowledgements relating to this article

The TAP block that was used in our study was performed with the ultrasound probe in the mid-axillary line between the iliac crest and the costal margin with the injection point anterior to the ultrasound probe.2 We call this a posterior TAP block according to Peter Hebbard, who was the first to describe this ultrasound-guided TAP block.3 This type of block is also called mid-axillary, classic or lateral TAP block and the TAP block applied via the triangle of Petit has been called posterior TAP block by some authors.

Assistance with the letter: none. Financial support and sponsorship: none. Conflicts of interest: none.

References 1

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Petersen PL, Mathiesen O, Stjernholm P, et al. The effect of transversus abdominis plane block or local anaesthetic infiltration in inguinal hernia repair. A randomised clinical trial. Eur J Anaesthesiol 2013; 30:415–421. McDonnell JG, O’Donnell B, Curley G, et al. The analgesic efficacy of transversus abdominis plane block after abdominal surgery: a prospective randomized controlled trial. Anesth Analg 2007; 104:193– 197. McDonnell JG, Curley G, Carney J, et al. The analgesic efficacy of transversus abdominis plane block after cesarean delivery: a randomized controlled trial. Anesth Analg 2008; 106:186–191. Carney J, Finnerty O, Rauf J, et al. Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks. Anaesthesia 2011; 66:1023–1030. Børglum J, Jensen K, Christensen AF, et al. Distribution patterns, dermatomal anesthesia and ropivacaine serum concentrations after bilateral dual transversus abdominis plane block. Reg Anesth Pain Med 2012; 37:294– 301. Rozen WM, Tran TM, Ashton MW, et al. Refining the course of the thoracolumbar nerves: a new understanding of the innervation of the anterior abdominal wall. Clin Anat 2008; 21:325–333. Bærentzen F, Maschmann C, Jensen K, et al. Ultrasound-guided nerve block for inguinal hernia repair: a randomized, controlled double-blinded study. Reg Anesth Pain Med 2012; 37:502–507.

Pernille L. Petersen, Ole Mathiesen and Joergen B. Dahl From the Department of Anaesthesia, Center of Head and Orthopaedics, Rigshospitalet, Copenhagen, Denmark Correspondence to Pernille L. Petersen, Department of Anaesthesia, Center of Head and Orthopaedics, Copenhagen, DK-2100, Denmark Tel: +45 30203897; fax: +45 35452059; e-mail: [email protected] Published online 31 March 2014

Editor, We thank Dr Børglum et al.1 for their interest in our study of transversus abdominis plane (TAP) block in inguinal hernia repair. Their letter pinpoints the difficultly in evaluating the effect of the TAP block, because there are different types of TAP blocks and there is no consensus of the nomenclature.

We agree with Dr Børglum et al. that the TAP block applied via the triangle of Petit and the more recently used ultrasound-guided TAP blocks that are applied more anteriorly, are two different blocks. Local anaesthetics applied via the triangle of Petit have a more distant spread via the paravertebral space. A recent review has demonstrated that the duration of analgesic efficacy of the TAP block applied via the triangle of Petit is longer than the ultrasound-guided TAP block.4

Acknowledgements relating to this article Assistance with the letter: none. Financial support and sponsorship: none.

DOI:10.1097/EJA.0000000000000074

Conflicts of interest: none.

References 1 2

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Børglum J, Tanggaard K, Moriggl B, McDonnell JG. Transversus abdominis plane block in inguinal hernia repair. Eur J Anaesthesiol 2014; 31:391–392. Petersen PL, Mathiesen O, Stjernholm P, et al. The effect of transversus abdominis plane block or local anaesthetic infiltration in inguinal hernia repair. A randomised clinical trial. Eur J Anaesthesiol 2013; 30:415–421. Lee TH, Barrington MJ, Tran TM, et al. Comparison of extent of sensory block following posterior and subcostal approaches to ultrasound-guided transversus abdominis plane block. Anaesth Intensive Care 2010; 38:452–460. Abdallah FW, Laffey JG, Halpern SH, Brull R. Duration of analgesic effectiveness after the posterior and lateral transversus abdominis plane block techniques for transverse lower abdominal incisions: a meta-analysis. Br J Anaesth 2013; 111:721–735. DOI:10.1097/EJA.0000000000000075

Eur J Anaesthesiol 2014; 31:388–394 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.

Correspondence

Association of haemoglobin levels with postoperative cardiovascular adverse events in patients undergoing vascular surgery Yi Cheng, Fu-Shan Xue, Shi-Yu Wang and Xin-Long Cui From the Department of Anaesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China Correspondence to Professor Fu-Shan Xue, Department of Anaesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 33 Ba-Da-Chu Road, Shi-Jing-Shan District, Beijing 100144, People’s Republic of China Tel: +86 13911177655; fax: +86 10 88772106; e-mail: [email protected]; [email protected] Published online 8 April 2014

Editor, In a recently published, retrospective observational study of vascular surgery patients, Valentijn et al.1 showed that preoperative haemoglobin levels, postoperative haemoglobin levels and haemoglobin decrease were all related to an increased risk of 30-day postoperative cardiovascular adverse events. Strengths of this study include the large sample of patients, and the use of multivariable and sensitivity analyses to adjust, and to reduce, the influence of confounding variables on study endpoints. However, other than the limitations described in the discussion of the article, we have noted further issues of this study making the interpretation of their results questionable. First, health status, type of surgery and comorbidities are important determinants of postoperative cardiovascular adverse events. This study showed that patients with postoperative cardiovascular adverse events had more risk factors of the Revised Cardiac Risk Index, more comorbidities, lower preoperative or postoperative haemoglobin levels and larger haemoglobin decreases. Furthermore, they were older, more likely to undergo open surgery and to receive transfusion. In our opinion, no matter how refined the adjustment is for differences in health status, surgery burden and comorbidities, it is never possible to ensure a complete adjustment for differences between patients with and without postoperative cardiovascular adverse events. Additionally, preoperative anaemia is actually associated with a number of other comorbidities and known risk factors that can significantly affect postoperative cardiovascular adverse events, such as advanced age, poor left ventricular ejection fraction, renal dysfunction, congestive heart failure, myocardial infarction, unstable angina, and so on. This can further make it difficult to identify the specific role of preoperative anaemia, and even sophisticated multivariable analyses are probably inadequate to clarify whether anaemia is a risk factor or simply a marker of a more severe and complex preoperative clinical pattern. Recently, a retrospective study including 574 860 noncardiac surgical patients has shown that preoperative anaemia was only associated with baseline diseases that

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markedly increased 30-day mortality and morbidity after surgery, whereas anaemia per se was only a weak and independent predictor of postoperative mortality and morbidity.2 Second, this study included and adjusted preoperative usage of many cardiovascular medications including b-blockers, but the authors did not specify whether patients taking these drugs before surgery continued their therapies after surgery. A systematic review of the literature showed that b-blockers lowered the perioperative risk of myocardial ischaemia and cardiovascular death among patients with clinical risk factors undergoing major vascular surgery.3 Furthermore, withdrawal of chronic b-blockade following vascular surgery has been shown to be associated with increased perioperative mortality.4 Third, this study did not include intraoperative haemodynamic data. In patients undergoing non-cardiac surgery, intraoperative hypotension, tachycardia and hypertension have been shown to be independently associated with postoperative myocardial injury and cardiac adverse events.5 Even short periods of an intraoperative mean arterial pressure less than 55 mmHg can result in myocardial injury, and there is an independent graded relationship between the duration of intraoperative hypotension and postoperative myocardial injury and cardiac complications.6 Finally, postoperative haemoglobin levels were measured within 0 to 3 days after surgery, but the authors did not specify the times when postoperative cardiovascular adverse events occurred and the times of postoperative troponin-T measurement. In high-risk patients undergoing vascular surgery under electrocardiographic monitoring, the majority of ischaemic events (67%) including those culminating in myocardial infarction, were reported to start between 50 min before and 60 min after the end of surgery and during the emergence from anaesthesia.7 Thus, in some patients who experienced postoperative cardiovascular adverse events, their postoperative haemoglobin levels might have been measured after occurrence of the events. Under these circumstances, great caution must be taken when interpreting the relationship of the measured postoperative haemoglobin levels with postoperative cardiovascular adverse events.

Acknowledgements related to this article Assistance with the letter: none. Financial support and sponsorship: none. Conflicts of interest: none.

References 1

Valentijn TM, Hoeks SE, Martienus KA, et al. Impact of haemoglobin concentration on cardiovascular outcome after vascular surgery: a retrospective observational cohort study. Eur J Anaesthesiol 2013; 30:664–670.

Eur J Anaesthesiol 2014; 31:388–394 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.

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Saager L, Turan A, Reynolds LF, et al. The association between preoperative anemia and 30-day mortality and morbidity in noncardiac surgical patients. Anesth Analg 2013; 117:909–915. Brooke BS. Perioperative beta-blockers for vascular surgery patients. J Vasc Surg 2010; 51:515–519. Biccard BM. Factors associated with mortality when chronic betablocker therapy is withdrawn in the peri-operative period in vascular surgical patients: a matched case-control study. Cardiovasc J Afr 2010; 21:97–102. Kheterpal S, O’Reilly M, Englesbe MJ, et al. Preoperative and intraoperative predictors of cardiac adverse events after general, vascular, and urological surgery. Anesthesiology 2009; 110:58–66. Walsh M, Devereaux PJ, Garg AX, et al. Relationship between intraoperative mean arterial pressure and clinical outcomes after noncardiac surgery: toward an empirical definition of hypotension. Anesthesiology 2013; 119:507–515. Landesberg G, Mosseri M, Zahger D, et al. Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depressiontype ischemia. J Am Coll Cardiol 2001; 37:1839–1845. DOI:10.1097/EJA.0000000000000078

Reply to: association of haemoglobin levels with postoperative cardiovascular adverse events in patients undergoing vascular surgery Tabita M. Valentijn, Sanne E. Hoeks, Hence J. Verhagen, Felix van Lier and Robert J. Stolker

postoperative haemoglobin levels and postoperative cardiovascular events.2 We agree that residual confounding could be an inherent bias due to the design and therefore we highlighted in the limitations section of the discussion that any assumptions about causality between haemoglobin and outcome cannot be made. Additional adjustments were made for the use of medication, but as stated in the results section, the reported estimates did not change. We did not assess whether medication was discontinued in the perioperative period, as this was beyond the research question. Cheng et al.1 commented on the lack of intraoperative haemodynamic data that could have influenced the results. Unfortunately, these data were not collected in our study and we agree that this information would have made our manuscript even more valuable. Finally, Cheng et al.1 are questioning the timing of postoperative haemoglobin levels and occurrence of events. However, in the methods section, we clearly state that all patients were excluded when they experienced an event that occurred before postoperative haemoglobin was measured.

Acknowledgements relating to this article Assistance with the letter: none.

From the Erasmus University Medical Center, Rotterdam, The Netherlands

Financial support and sponsorship: none.

Correspondence to Robert J. Stolker, MD, PhD, the Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands E-mail: [email protected]

Conflicts of interest: none.

Published online 20 May 2014

Editor, We appreciate the interest and comments of Cheng et al.1 regarding our manuscript about haemoglobin and adverse outcome in vascular surgery. In our retrospective study, we evaluated the relationship between pre and

References 1

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Cheng Y, Xue F-S, Wang S-Y, Cui X-L. Association of haemoglobin levels with postoperative cardiovascular adverse events in patients undergoing vascular surgery. Eur J Anaesthesiol 2014; 31:393–394. Valentijn TM, Hoeks SE, Martienus KA, et al. Impact of haemoglobin concentration on cardiovascular outcome after vascular surgery: a retrospective observational cohort study. Eur J Anaesthesiol 2013; 30:664–670. DOI:10.1097/EJA.0000000000000077

Eur J Anaesthesiol 2014; 31:388–394 Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited.

Waiting for Godot: an analysis of 2622 operating room turnover times.

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