BMJ  2004;329:258 (31 July), doi:10.1136/bmj.38156.767118.7C (published 8 July 2004)

Paper

Randomised controlled trial assessing the impact of a nurse delivered, flow monitored protocol for optimisation of circulatory status after cardiac surgery

¹ Bloomsbury Institute of Intensive Care Medicine, Department of Medicine and Wolfson Institute of Biomedical Research, University College London, Middlesex Hospital, London W1T 3AA, ² Intensive Care National Audit and Research Centre, BMA House, London WC1H 9JR

Abstract

Objective To assess whether a nurse led, flow monitored protocol for optimising circulatory status in patients after cardiac surgery reduces complications and shortens stay in intensive care and hospital.

Design Randomised controlled trial.

Setting Intensive care unit and cardiothoracic unit of a university teaching hospital.

Participants 174 patients who had cardiac surgery between April 2000 and January 2003.

Interventions Patients were allocated to conventional haemodynamic management or to an algorithm guided by oesophageal Doppler flowmetry to maintain a stroke index above 35 ml/m².

Results 26 control patients had postoperative complications (two deaths) compared with 17 (four deaths) protocol patients (P = 0.08). Duration of hospital stay in the protocol group was significantly reduced from a median of nine (interquartile range 7-12) days to seven (7-10 days; P = 0.02). The mean duration of hospital stay was reduced from 13.9 to 11.4 days, a saving in hospital bed days of 18% (95% confidence interval -12% to 47%). Usage of intensive care beds was reduced by 23% (-8% to 59%).

Conclusions A nurse delivered protocol for optimising circulatory status in the early postoperative period after cardiac surgery may significantly shorten hospital stay.

Introduction

Hypovolaemia and tissue hypoperfusion can pass undetected during and after major surgery.¹ These are often not clinically apparent for several days, and may lead to increased morbidity and mortality.

Several perioperative studies have used invasive (pulmonary artery catheterisation) or minimally invasive (oesophageal Doppler flowmetry) monitoring technologies to optimise circulatory variables,² and have shown major improvements in postoperative complications and stay in intensive care or hospital. Others, however, have found no improvement in outcomes.³ To our knowledge, only one randomised study has specifically investigated optimisation of circulatory status after cardiac surgery,⁴ and this reported a reduction in median duration of hospital stay.

We previously reported that a low stroke volume index (< 35 ml/m²) and a high heart rate on admission to intensive care after cardiac surgery and at four hours were the best prognostic factors for the development of subsequent complications.⁵ We therefore studied the optimisation of circulatory status in patients in the first four hours, randomising them to receive treatment guided by oesophageal Doppler flowmetry to achieve a stroke volume index above 35 ml/m². This trial differs from the previous study in two major respects.⁴ Firstly, cardiac output was monitored using minimally invasive technology and, secondly, nurses conducted the study using a protocol driven approach.

Participants and methods

Participants were undergoing cardiopulmonary bypass surgery. We excluded patients undergoing off-pump surgery, aged under 18 years, or with relative contraindications to the use of the oesophageal Doppler probe, such as oesophageal disease. Patients were also excluded postoperatively if on admission to intensive care there was excessive bleeding, unstable arrhythmias, a need for intra-aortic balloon counterpulsation, or inotrope requirements 10 µg/kg/min of dopamine or dobutamine or 0.16 µg/kg/min of adrenaline (epinephrine) or noradrenaline (norepinephrine).

For the oesophageal Doppler technique a 6 mm probe was placed into the lower oesophagus through the mouth or nose. The probe is directed to detect midstream blood flow in the descending thoracic aorta, with the aid of an online monitor and an integral loudspeaker.

Objectives and intervention
Our primary objective was to compare the lengths of stay in intensive care and hospital after cardiac surgery between protocol and control groups, and secondary objective to compare postoperative complications between the two groups.

The control group received standard postoperative care determined by the intensive care and cardiac surgical teams. This, as in most UK centres, uses markers of tissue perfusion such as urine output and arterial base deficit. Monitoring of cardiac output could be included if considered clinically indicated. Within 10 minutes of admission to the intensive care unit and at four hours postoperatively, the study nurse took readings from these patients with an oesophageal Doppler probe. Doctors and nurses not involved with the study were not allowed sight of these readings. If patients in either group were ready for extubation before four hours, a Doppler recording was made before removal of the endotracheal tube.

The oesophageal Doppler probe was also inserted within 10 minutes of arrival of the protocol patients on the intensive care unit. The algorithm in figure 1 was followed to increase the stroke volume index to 35 ml/m² or greater using repeated colloid challenges, with nitrates and inotropes given as required. This management was directed by the study nurse, with indications for referral to medical staff.

View larger version (52K): [in this window] [in a new window]   Fig 1 Treatment algorithm to optimise circulatory status in patients after cardiac surgery

 

Recordings of standard haemodynamic variables and intravenous fluid and drug requirements were made manually over the first four hours. Follow up data were collected on days 1, 2, and 5 postoperatively, including complications, time to extubation, and length of stay in intensive care and hospital. If the patient was medically fit for hospital discharge but this was delayed for social or logistical reasons, a note was made. Both patients and staff on the general wards to which patients were sent after intensive care were unaware of the group assignment.

Statistical analysis
Patients were randomised on arrival at intensive care. We calculated a sample size of 170 patients (85 in each group), and tested for differences in postoperative measurements and complications between treatment groups (see bmj.com).

Results

Overall, 179 patients were recruited between April 2000 and January 2003 (see bmj.com). After exclusions, there were 89 patients in the protocol group and 85 in the control group. The groups were well matched for age, sex, weight, Parsonnet cardiac risk score, and type of surgery.⁶ The median first 24 hour acute physiological and chronic health evaluation II score was similar in both groups (10 protocol, 11 control).

The table shows the haemodynamic data and fluid requirements over the initial four hour postoperative period. Although stroke volume index, cardiac index, and use of colloid were well matched at baseline (within 10 minutes of admission), they were significantly greater in the protocol group at four hours; use of inotropes was similar between the two groups. Colloid was given to all but one of the control patients. None of the control patients had pulmonary artery catheters in situ or had Doppler probes placed because of perceived clinical need. Inotropes were not instituted as per protocol to increase stroke volume indices to 35 ml/m² or greater owing to the short duration of the study and the frequent need for repeated fluid challenges in the study period. At four hours, 35 (39%) protocol patients and 48 (56%) control patients had values below 35 ml/m².

View this table: [in this window] [in a new window]   Management of patients in four hours after cardiac surgery. Values are means (standard deviations)

 

In the protocol group, the mean number of days in intensive care, although not statistically significant, was reduced from 3.2 to 2.5 (23% reduction, 95% confidence interval -8% to 59%; fig 2). The mean duration of hospital stay in this group was reduced from 13.9 to 11.4 days (18% reduction, -12% to 47%), with a significant reduction in median duration of stay from nine to seven days (P = 0.02).

View larger version (23K): [in this window] [in a new window]   Fig 2 Duration of stay in intensive care and hospital in patients receiving strategy to optimise circulatory status after cardiac surgery (protocol) or conventional management (control)

 

Four deaths occurred in the protocol group and two in the control group, the causes of which were not considered directly attributable to early postoperative care. Comparisons of length of stay in survivors only were similar to those for all patients. The protocol group showed a trend towards fewer major postoperative complications and deaths than the control group (see bmj.com).

Discussion

A nurse delivered protocol to optimise circulatory status of patients early after cardiac surgery, using oesophageal Doppler flowmetry and targeted at improving stroke volume, reduced the length of hospital stay. This protocol was also associated with a trend towards fewer complications and reduced stay in intensive care.

What is already known on this topic After cardiac surgery many patients have complications that prolong hospital stay Perioperative tissue hypoxia is the postulated trigger for many of these complications What this study adds Optimisation of intravascular volume in the first four hours postoperatively reduces complications and bed usage Nurses could deliver the protocol using a minimally invasive device that monitors stroke volume and responses to interventions

Tissue hypoperfusion is common in patients perioperatively and is associated with high postoperative morbidity and mortality. Non-cardiac complications have been found to be associated with more adverse outcomes.⁷ As in our study, these were independent of Parsonnet score and bypass time.

Optimisation of circulatory status perioperatively was a concept first promulgated by Shoemaker.⁸ Comparable results from other groups using a similar goal directed approach lends further support to the importance of avoiding a tissue oxygen debt perioperatively.^9-11 In large Canadian and US studies, however, placement of a pulmonary artery catheter without targeting predefined haemodynamic end points produced no difference in postoperative outcomes.^{3 12} We believe our results are generalisable to countries where monitoring of cardiac output is performed more often during cardiac surgery than in the United Kingdom, and emphasise the need to obtain maximum utility from a monitoring technique by titrating therapy.

The necessity for treatment to be directed by invasive monitoring (pulmonary artery catheterisation) has been challenged by several groups that used oesophageal Doppler flowmetry to maximise intraoperative stroke volume by repeated fluid challenges.^13-16 These studies showed important (30-40%) reductions in length of hospital stay after cardiac, orthopaedic, or abdominal surgery. The lesser reduction in mean length of hospital stay (18%) achieved by us is comparable to that reported by Polonen,⁴ showing that optimisation of circulatory status should ideally begin at the start of, if not before, a major operation.

Our study shows that nurses can safely insert and align the oesophageal Doppler probe to detect descending aortic blood flow within a few minutes. Although staff could not be blinded to the randomisation schedule, the subsequent management of patients after the first four hours was identical and they were not made aware of the Doppler results.

The intention to use inotropes if fluid loading failed to achieve a target stroke index was not met, mainly because of time constraints but in part to the reticence of the nurses. Our study should thus be viewed as a trial of immediate optimisation of fluid status in the postoperative period.

Weaknesses of our trial were that it was of relatively small size and conducted in only one centre. A larger multicentre trial is needed to confirm the generalisability of our findings and the effect on mean rather than median length of hospital stay, which is more relevant to costs.

In conclusion, improvements in postoperative outcomes in patients after cardiac surgery may be achieved by early intervention targeted at optimising the stroke volume. A nurse delivered, protocol driven approach has the potential for widespread application as it is not routinely feasible for a clinician to be constantly at the bedside.

---

This is the abridged version of an article that was posted on bmj.com on 8 July 2004: http://bmj.com/cgi/doi/10.1136/bmj.38156.767118.7C

We thank for their cooperation the nursing and medical staff at the Heart Hospital and previously at the Middlesex Hospital intensive care and postoperative cardiothoracic units.

Contributors: See bmj.com

Funding: Deltex UK provided an unrestricted educational grant for this study.

Competing interests: Deltex provided research funds to the department and contributed towards the salaries of the research nurses (LC, DS, MMcK, and HMcG) and travel expenses and registration fees to enable them to present their research at national and international congresses. MS does consultancy work for Deltex.

Ethical approval: Ethics committee University College London Hospitals NHS Trust.

References

1. Shoemaker WC, Wo CC, Thangathurai D, Velmahos G, Belzberg H, Asensio JA, et al. Hemodynamic patterns of survivors and nonsurvivors during high risk elective surgical operations. World J Surg 1999;23: 1264-70.[Medline]
2. Kern JW, Shoemaker WC. Meta-analysis of hemodynamic optimisation in high-risk patients. Crit Care Med 2002;30: 1686-9.[CrossRef][ISI][Medline]
3. Sandham JD, Hull RD, Brant RF, Knox L, Pineo GF, Doig CJ, et al. A randomised, controlled trial of the use of pulmonary-artery catheters in high-risk surgical patients. N Engl J Med 2003;348: 5-14.[Abstract/Free Full Text]
4. Polonen P, Ruokonen E, Hippelainem M, Poyhonen M, Takala J. A prospective randomised study of goal oriented hemodynamic therapy in cardiac surgical patients. Anesth Analg 2000;90: 1052-9.[Abstract/Free Full Text]
5. Poeze M, Ramsay G, Greve JWM, Singer M. Prediction of postoperative cardiac surgical morbidity and organ failure within 4 hours of ICU admission using esophageal Doppler ultrasonography. Crit Care Med 1999;27: 1288-94.[CrossRef][ISI][Medline]
6. Parsonnet V, Dean D, Bernstein AD. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation 1989;79: I3-12.
7. Welsby IJ, Bennett-Guerrero E, Atwell D, White WD, Newman MF, Smith PK, et al. The association of complication type with mortality and prolonged stay after cardiac surgery with cardiopulmonary bypass. Anesth Analg 2002;94: 1072-8.[Abstract/Free Full Text]
8. Shoemaker WC, Appel PL, Kram HB, Waxman K, Lee TS. Prospective trial of supranormal values of survivors as therapeutic goals in high-risk surgical patients. Chest 1988;94: 1176-86.[Abstract/Free Full Text]
9. Shoemaker WC, Appel PL, Kram HB. Role of oxygen debt in the development of organ failure sepsis, and death in high-risk surgical patients. Chest 1992;102: 208-15.[Abstract/Free Full Text]
10. Boyd O, Grounds RM, Bennett ED. A randomized clinical trial of the effect of deliberate perioperative increase of oxygen delivery on mortality in high-risk surgical patients. JAMA 1993;270: 2699-707.[Abstract]
11. Wilson J, Woods I, Fawcett J, Whall R, Dibb W, Morris C, et al. Reducing the risk of major elective surgery: randomised controlled trial of preoperative optimisation of oxygen delivery. BMJ 1999;318: 1099-103.[Abstract/Free Full Text]
12. Polanczyk CA, Rohde LE, Goldman L, Cook EF, Thomas EJ, Marcantonio ER, et al. Right heart catheterization and cardiac complications in patients undergoing noncardiac surgery: an observational study. JAMA 2001;286: 309-14.[Abstract/Free Full Text]
13. Mythen MG, Webb AR. Perioperative plasma volume expansion reduces the incidence of gut mucosal hypoperfusion during cardiac surgery. Arch Surg 1995;130: 423-9.[Abstract]
14. Sinclair S, James S, Singer M. Intraoperative intravascular volume optimisation and length of hospital stay after repair of proximal femoral fracture: randomised controlled trial. BMJ 1997;315: 909-12.[Abstract/Free Full Text]
15. Gan TJ, Soppitt A, Maroof M, el-Moalem H, Robertson KM, Moretti E, et al. Goal-directed intraoperative fluid administration reduces length of hospital stay after major surgery. Anesthesiology 2002;97: 820-6.[CrossRef][ISI][Medline]
16. Venn R, Steele A, Richardson P, Poloniecki J, Grounds M, Newman P. Randomized controlled trial to investigate influence of the fluid challenge on duration of hospital stay and perioperative morbidity in patients with hip fractures. Br J Anaesth 2002;88: 65-71.[Abstract/Free Full Text]

(Accepted 24 May 2004)

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Relevant Article

Nurses using oesophageal Doppler improve outcome after heart surgery
BMJ 2004 329: 0. [Full Text]

This article has been cited by other articles:

• Buettner, M., Schummer, W., Huettemann, E., Schenke, S., van Hout, N., Sakka, S. G. (2008). Influence of systolic-pressure-variation-guided intraoperative fluid management on organ function and oxygen transport. Br J Anaesth 101: 194-199 [Abstract] [Full text]  
• Rubenfeld, G. D., McNamara-Aslin, E., Rubinson, L. (2007). The Pulmonary Artery Catheter, 1967 2007: Rest in Peace?. JAMA 298: 458-461 [Full text]  
• Bundgaard-Nielsen, M., Ruhnau, B., Secher, N. H., Kehlet, H. (2007). Flow-related techniques for preoperative goal-directed fluid optimization. Br J Anaesth 98: 38-44 [Abstract] [Full text]  
• Isakow, W., Schuster, D. P. (2006). Extravascular lung water measurements and hemodynamic monitoring in the critically ill: bedside alternatives to the pulmonary artery catheter. Am. J. Physiol. Lung Cell. Mol. Physiol. 291: L1118-L1131 [Abstract] [Full text]  
• Tote, S. P., Grounds, R. M. (2006). Performing perioperative optimization of the high-risk surgical patient. Br J Anaesth 97: 4-11 [Abstract] [Full text]  
• Vincent, J.-L., Fink, M. P., Marini, J. J., Pinsky, M. R., Sibbald, W. J., Singer, M., Suter, P. M., Cook, D., Pepe, P. E., Evans, T. (2006). Intensive care and emergency medicine: progress over the past 25 years.. Chest 129: 1061-1067 [Abstract] [Full text]  

Rapid Responses:

Read all Rapid Responses

Does this prove that nurses are not a safe substitute for anaesthetists?

Richard G Fiddian-Green
bmj.com, 30 Jul 2004 [Full text]

Flow monitored protocol for optimisation of circulatory status after cardiac surgery

michael poullis
bmj.com, 1 Aug 2004 [Full text]

Would like to see haemodynamic data

Eugene B Campbell, et al.
bmj.com, 3 Aug 2004 [Full text]

Surgeons contest the conclusions drawn from this study

Fraser W.H. Sutherland, et al.
bmj.com, 4 Aug 2004 [Full text]

Without strong biologically plausible explanation, dramatic impact on outcomes by single interventions is unlikely to be reproducible

Ani C Anyanwu
bmj.com, 9 Aug 2004 [Full text]

Senior author's reply

Mervyn Singer, et al.
bmj.com, 25 Sep 2004 [Full text]