Mortality and utilisation of critical care resources amongst high-risk surgical patients in a large NHS trust

Defining higher-risk surgery

PURPOSE OF REVIEW

Defining the contemporary high-risk noncardiac surgical population using objective clinical outcomes data is paramount for the rational allocation of healthcare resources, truly informed patient consent and improving patient-centered outcomes.

RECENT FINDINGS

Data from independent healthcare systems have identified that the development, and consequences, of postoperative morbidity extend beyond the immediate postoperative hospital period and confer substantially increased risk of death. Cardiac insufficiency, rather than the relatively heavily explored paradigm of perioperative cardiac ischemia, is emerging as the dominant factor associated with excess risk of prolonged postoperative morbidity. The development of prospective, validated, time-sensitive morbidity data collection tools has also helped define patients at higher risk of noncardiac morbidities and short-term perioperative outcomes.

SUMMARY

Higher risk surgical patients present an increasingly major challenge for healthcare resource utilization. Detailed outcome studies using validated morbidity tools are urgently required to establish the extent to which postoperative morbidity may be predicted. Robust identification of patients at the highest risk of perioperative morbidity may permit further clinic-to-bench translational understanding of the pathophysiologic mechanisms underlying postoperative organ dysfunction. Defining the high-risk surgical patient population is as critically important for global public health planning as it is for the perioperative team.

The role of a multidisciplinary pre-assessment clinic in reducing mortality after complex orthopaedic surgery

INTRODUCTION

This paper describes an audit loop. The aim of this study was to audit the effect of a specialised preoperative anaesthetic assessment clinic after hip and knee arthroplasty and revision arthroplasty.

PATIENTS AND METHODS

We studied patients undergoing hip and knee surgery (arthroplasty and revision arthroplasty). We collected data concerning postoperative admissions to the high dependency unit (HDU), intensive care unit (ICU) and post-anaesthesia care unit (PACU) (planned and unplanned rates of admission, length of stay). We also noted mortality. In the first part of the study (April 2005 to March 2006) we studied 298 patients. All patients were assessed independently by an anaesthetist on the day of surgery. A multidisciplinary preoperative assessment clinic commenced in April 2006. After this date all patients were assessed preoperatively by a multidisciplinary anaesthetic lead team. In the second part of the study (May 2006 to April 2009) a further 1,147 arthroplasty patients were studied. Data were again collected regarding HDU, ICU, PACU and mortality, as noted above.

RESULTS

We found statistically significant (p = 0.001) reductions in the admissions to PACU (22% down to 10%) and in mortality (6.1% down to 1.2%) after the introduction of the pre-assessment clinic. There was also a statistically significant (p = 0.01) reduction in the HDU length of stay (2.1 days to 1.6 days), ICU unplanned admissions (1.3% to 0.4%) and the ICU length of stay (2.3 to 1.9 days). We estimated cost savings of nearly £50,000 in the second part of the study. This is based on the average decrease in HDU and ICU length of stay.

CONCLUSIONS

We recommend the use of a multidisciplinary pre-assessment clinic for complex orthopaedic surgery.

[Perioperative mortality: retrospective cross-sectional study of surgical patients who died between 2004 and 2008 in a tertiary care hospital]

OBJECTIVE

Retrospective analysis of all surgical, early postoperative, and 1-week to detect risk factors.

MATERIAL AND METHODS

A database was established to record clinical, anesthetic, and surgical variables, grouped as preoperative, intraoperative and postoperative factors, and reflecting comorbidities and postoperative complications. Each patient's cause of death was also recorded. Factors influencing mortality during surgery, at 48 hours, and at 1 week were explored by comparing frequencies to detect correlations.

RESULTS

From 2004 to 2008, a total of 809 deaths occurred in the 82412 hospitalized surgical patients. Patients who died during surgery or within 48 hours were younger, had a higher ASA physical status classification, had more cardiovascular risk factors, were less likely to have a diagnosis of cancer, and had spent less time in hospital before the operation. Intraoperative complications, particularly bleeding and cardiac events, were more frequent in patients whose condition was more complex and who died during surgery; that pattern was similar but less marked in patients dying within 48 hours. The patients who died within 48 hours had a higher rate of postoperative hemodynamic complications; the patients who died during the week following surgery had higher rates of septic, neurologic, and respiratory complications.

CONCLUSIONS

Emergency surgery stands out as an important predictor of death during or after surgery; other significant risk factors are postoperative complications.

Haemodynamic optimisation improves tissue microvascular flow and oxygenation after major surgery: a randomised controlled trial

INTRODUCTION

Post-operative outcomes may be improved by the use of flow related end-points for intra-venous fluid and/or low dose inotropic therapy. The mechanisms underlying this benefit remain uncertain. The objective of this study was to assess the effects of stroke volume guided intra-venous fluid and low dose dopexamine on tissue microvascular flow and oxygenation and inflammatory markers in patients undergoing major gastrointestinal surgery.

METHODS

Randomised, controlled, single blind study of patients admitted to a university hospital critical care unit following major gastrointestinal surgery. For eight hours after surgery, intra-venous fluid therapy was guided by measurements of central venous pressure (CVP group), or stroke volume (SV group). In a third group stroke volume guided fluid therapy was combined with dopexamine (0.5 mcg/kg/min) (SV & DPX group).

RESULTS

135 patients were recruited (n = 45 per group). In the SV & DPX group, increased global oxygen delivery was associated with improved sublingual (P < 0.05) and cutaneous microvascular flow (P < 0.005) (sublingual microscopy and laser Doppler flowmetry). Microvascular flow remained constant in the SV group but deteriorated in the CVP group (P < 0.05). Cutaneous tissue oxygen partial pressure (PtO2) (Clark electrode) improved only in the SV & DPX group (P < 0.001). There were no differences in serum inflammatory markers. There were no differences in overall complication rates between the groups although acute kidney injury was more frequent in the CVP group (CVP group ten patients (22%); pooled SV and SV & DPX groups seven patients (8%); P = 0.03) (post hoc analysis).

CONCLUSIONS

Stroke volume guided fluid and low dose inotropic therapy was associated with improved global oxygen delivery, microvascular flow and tissue oxygenation but no differences in the inflammatory response to surgery. These observations may explain improved clinical outcomes associated with this treatment in previous trials.

TRIAL REGISTRATION NUMBER

ISRCTN 94850719.

Influence of general health and degree of surgical insult on long-term survival

BACKGROUND

This study investigated the relationship of American Society of Anesthesiologists Physical Status (ASA-PS) grade and degree of surgical insult to long-term postoperative survival.

METHODS

National death records to June 2007 were matched against records of patients undergoing elective surgery between January 1997 and December 2001. Stratified survival analysis was performed to allow baseline hazard functions to vary among four patient groups (15-64 years with no malignancy, at least 65 years with no malignancy, 15-64 years with malignancy and at least 65 years with malignancy).

RESULTS

Of 8134 patients, 6185 (76.0 per cent) were alive after a median follow-up of 7.1 (range 0-10.5) years. The overall mortality rate was 3.62 (95 per cent confidence interval (c.i.) 3.46 to 3.78) per 100 person-years. The 10-year probability of survival was significantly higher in ASA-PS I or II for minor or intermediate surgery (90.7 (89.1 to 92.1) per cent) than in ASA-PS I or II for major or complex major surgery (79.6 (77.5 to 81.6) per cent), ASA-PS III or IV for minor or intermediate surgery (41.2 (36.2 to 46.7) per cent) and ASA-PS III or IV for major or complex major surgery (44.6 (41.4 to 47.7) per cent) (P < 0.001). Priority of admission modified survival probabilities. Adjusted survival probabilities were lowest in the elderly with malignancy.

CONCLUSION

ASA-PS grade has a more significant and persistent effect on long-term survival than degree of surgical insult.

Latest developments in peri-operative monitoring of the high-risk major surgery patient

Peri-operative monitoring technology has made great strides in the last 20 years with the introduction of minimally invasive devices to measure inter alia stroke volume, cardiac output, depth of anaesthesia and cerebral and tissue oxygen monitoring. Despite these technological advances, peri-operative management of the high risk major surgery patient has remained virtually unchanged. The vast majority of patients undergo a pre-operative assessment which is neither designed to quantify functional capacity nor predict outcome. Anaesthetists then usually monitor these patients using the same technology (e.g. pulse oximetry (SpO2), invasive systemic BP and CVP, end tidal carbon dioxide (etCO2) and anaesthetic agent monitoring) that was available in the early 1980s. Conventional intra-operative management can result in occult low levels of blood flow and oxygen delivery that lead to complications that only occur days or weeks following surgery and give false re-assurance to the anaesthetist that he or she is doing a "good job". Post-operative management then often takes place in an environment with reduced levels of both monitoring equipment and staff expertise. It is perhaps not surprising that outcome still remains poor in high-risk patients.(1) In this review, we will briefly describe the role of peri-operative optimization, some of the available monitors and indicate how their combined use might be beneficial in managing the high-risk surgical patient. We believe that although there is now evidence to suggest that the use of individual new monitors (such as assessment of fluid status, depth of anaesthesia, tissue oxygenation and blood flow) can influence outcome, it will only be their combination that will radically improve the peri-operative management and outcome of high-risk surgical patients. It is a matter of some urgency that large scale, prospective and collaborative studies be designed, funded and executed to prove or disprove this hypothesis.

The use of early intervention to prevent postoperative complications

PURPOSE OF REVIEW

The incidence of complications following major surgery is surprisingly high. Patients who develop complications suffer a reduction in long-term survival. This review aims to explore recent advances in the management of surgical patients aimed at preventing postoperative complications.

RECENT FINDINGS

Identifying patients prior to surgery who are at risk of a poor outcome remains challenging. There are a number of scoring systems to assist clinical risk assessment. Recent work has investigated the use of plasma biomarkers for perioperative risk prediction. Therapies aimed at reducing complication rates by attempting to improve tissue oxygen delivery include goal-directed haemodynamic therapy and postoperative noninvasive ventilation. The role of perioperative beta-adrenoceptor antagonists remains unclear. Other important measures include the use of a surgical safety checklist and thromboprophylaxis.

SUMMARY

Current systems for the identification and treatment of high-risk surgical patients are inadequate. Further research is required to establish the optimal approach to the identification and management of the high-risk surgical patient.

Microvascular flow and tissue oxygenation after major abdominal surgery: association with post-operative complications

OBJECTIVE

To evaluate the relationship between global oxygen delivery (DO(2)I), microvascular flow and tissue oxygenation in patients who did and did not develop complications following major abdominal surgery.

DESIGN

Prospective observational study.

SETTING

Post-operative critical care unit.

PARTICIPANTS

Twenty-five patients receiving standard peri-operative care following major abdominal surgery.

MEASUREMENTS AND MAIN RESULTS

Data were collected before, and for 8 h after surgery. DO(2)I was measured by lithium dilution and arterial waveform analysis. Cutaneous PtO(2) was measured at two sites on the abdominal wall using a Clark electrode. The sublingual microcirculation was visualised using sidestream darkfield imaging. Cutaneous red cell flux was measured using laser Doppler flowmetry. Fourteen patients (56%) developed complications with two deaths. Small vessel (<20 microm) microvascular flow index in those patients who developed complications was lower before (P < 0.05) and after surgery (P < 0.0001) compared to patients who did not develop complications. Both the proportion and density of perfused small vessels were also lower in patients who developed complications after surgery (P < 0.01) but not before surgery. DO(2)I was low in all patients but did not differ between patients who did and did not develop complications. Similarly, there were no associated differences in cutaneous red cell flux or PtO(2).

CONCLUSION

In a group of patients with low DO(2)I following major abdominal surgery, microvascular flow abnormalities were more frequent in patients who developed complications. However, there were no differences in DO(2)I, cutaneous PtO(2) or red cell flux between the two groups. Impaired microvascular flow may be associated with the development of post-operative complications.

Non-invasive automated measurement of cardiac output during stable cardiac surgery using a fully integrated differential CO(2) Fick method

OBJECTIVES

To re-evaluate the accuracy and precision of a non-invasive method for measurement of cardiac output based on the differential CO(2) Fick approach using an automated change in respiratory rate delivered by a ventilator under control by a prototype measurement system.

METHODS

Twenty-four patients during coronary artery bypass surgery, pre- and postcardiopulmonary bypass were recruited. After routine cannulation including pulmonary artery catheter, relaxant general anesthesia was induced. After hemodynamic and ventilatory stability were achieved, simultaneous paired measurements were made by the differential Fick method and by bolus thermodilution. Measurements were generated by inducing a change in respiratory rate by the ventilator under computer control. In Group 1, this involved an increase in respiratory rate from 8 to 12 breaths/min. In Group 2, this involved a decrease from 12 to 6 breaths/min.

RESULTS

Nineteen measurements were made in each Group, 12 pre-CPB and 7 post-CPB. In Group 1 mean bias was -0.06 l/min, with a precision of agreement of 0.87 l/min, r = 0.91. In Group 2 (excluding one outlier) mean bias was -0.07 l/min, with a precision of 1.12 l/min, r = 0.71.

CONCLUSIONS

Acceptable agreement with thermo- dilution during surgery was found, particularly where the ventilatory change involved an increase in respiratory rate from a lower baseline. This approach has potential to be readily integrated into modern anesthesia delivery platforms, allowing routine non-invasive cardiac output measurement.