Patients who undergo high-risk surgery represent a large amount of postoperative ICU-admissions. One of the most challenging issues is to identify the high-risk patient who should experience any complication in postoperative period and who could benefit from ICU surveillance and monitoring.
Many score systems developed aiming to quantify and predict the risk of a poor outcome, but none of these can be considered the best one. Further, several countries performed specific guidelines for ICU admission considering many aspects of the problem [
Renal resistive index (RRI = peak systolic velocity-end diastolic velocity/peak systolic velocity) consists of the measurement of renal arterial resistances to blood flow detected by echo-color-Doppler system and it is reliably correlated with kidney injuries and its severity [
Renal resistive index could be applicable also in the monitoring of critical patients. Recently Bossard et al. studied patients at risk of renal insufficiency undergoing cardiac surgery. In these patients, authors calculated the RRI after patients entered intensive care unit (ICU). They found that renal resistive index is greater in patients who develop renal failure. In addition, the resistivity index correlates well with the severity of kidney damage, [
Darmon et al. studied renal resistivity index in patients admitted to ICU measuring in order to predict the onset of kidney failure during the course. Authors found that RRI was able to predict the onset of renal failure and the potential reversibility of the same [
Furthermore, RRI may be an early independent factor detecting posttraumatic haemorrhagic shock in patients admitted to Emergency Department for traumatic injury [
The study was an observational phase II dual-center trial including patients who underwent major surgical operation, in accordance with the Helsinki Declaration. All subjects gave a written informed consent and the study was approved by the local Ethics Committee [
The trial was performed according to STROBE statement for observational studies [
Primary endpoint was the association between altered
Inclusion criteria were age > 18 years, any gender, elective cardiac and thoracic surgery, vascular, neurologic, and abdominal major surgery, intraoperative general anesthesia, and ability to give informed consent.
Exclusion criteria were total renal replace treatment (RRT) for bilateral nephrectomy or chronic kidney failure (serum Creatinine > 2 mg/dL), pregnancy, and emergency operation.
General anaesthesia started with Propofol 2.5 mg/kg + Fentanyl 1-2 mcg/kg. A gas mixture including air, oxygen (FiO2 0.50), and sevoflurane 1-2% was administered for anaesthesia maintenance. No-depolarizing myorelaxant drug (Atracurium 0.5 mg/kg or cis-Atracurium 0.15 mg/kg boluses, and repeated top up doses as needing) was administered for tracheal intubation and as requested after patient was connected to mechanical ventilator (protective ventilation: tidal volume 6 mL/kg; respiratory rate 10–12 apm; peak respiratory pressure limit 35 cm H2O; positive end-expiratory pressure 5 cm H2O). Fentanyl 1-2 mcg/kg bolus was readministered after 30 and 60 minutes.
Intraoperative monitoring included invasive blood pressure (IBP), electrocardiogram (EKG) with ST-segment analysis, heart rate (HR), end-tidal carbon dioxide (EtCO2), central venous pressure (CVP), and central venous oxygen saturation (ScvO2) according to clinical judgment. Cardiac output (CO) and correlated parameters were monitored by FloTrac/VigleoTM (Edwards Lifescience, Irvine, CA) in thoracic surgery and by pulmonary artery catheter (PAC) in cardiac operations, depending on the habits of the two centers participating to the trial. These data were recorded hourly reporting the worst value observed. Furthermore, a blood gas analysis was sampled and fluid balance was computed.
Within 15 minutes, after the transfer of the patient to the recovery room (or during awakening period in subjects submitted to cardiac surgery) a skilled anaesthesiologist performed renal resistive index measurement by C5-2 convex probe of EnVisor C HD sonogram (PHILIPS Ultrasound, Bothell, WA, USA 98041). We measured RRI in triplicate and then the average value was recorded. A blood sample was collected to test serum creatinine, serum lactate, and B-type natriuretic peptide (BNP). Outcome data were recorded for the whole period of hospital staying reporting the incidence of any type of complications occurring during the first postoperative week. Furthermore, at the end of operation we calculated the Surgical APGAR Score (SAS) aiming to explore any correlation of this validated system and RRI about detection of postoperative morbidity [
Our analysis was performed not only over the whole sample population, but also in the subgroup of patients who underwent cardiothoracic surgery as their abdominal-splanchnic district was not surgically injured. In these cases our hypothesis was that the subgroup may provide results not altered by surgical manipulation that could provoke any renal vascular bed reaction.
This was an observational dual-center trial, investigating whether
Variables are expressed as number and percentage within a 95% confidence interval (CI), mean and standard deviation, or median and range, as appropriate. Differences between group
ROC analysis was performed as appropriate.
Relative to the study of association with the presence or absence of complications, all the independent variables which have been found to have a statistical association with a
A
From July 2012 to February 2013 we enrolled 218 consecutive patients submitted to major high-risk surgery. Out of the whole sample 13 patients were excluded due to incomplete data collected, resulting in a final sample of 205 patients. We recorded 49 cardiac surgery (23 valve substitution/plasty, 21 CABG (coronary artery bypass graft), and 5 CABG + valve substitution/plasty), 96 thoracic surgery (35 lung lobectomy, 23 oesophageal surgery, 15 atypical resection, 11 VATS (video assisted thoracoscopy), 5 pneumonectomy, 3 pleurectomy, 2 pneumopericardial phrenectomy, and 2 thymectomy), 42 abdominal surgery (15 liver resection, 10 gastroenteric/colon resection, 8 abdominal aortic aneurysmectomy, 7 pancreatic-duodenal resection, and 2 pancreatectomy/splenopancreatectomy) 16 brain neoplasm resection, and 2 carotid endarterectomy.
The whole sample populations were labeled as ASA 1–4. Table
Population characteristics.
Age (years) |
|
BMI (Kg/m2 body surface area) |
|
ASA 3-4 ( |
102 (49.76%) |
Smoking ( |
98 (47.80%) |
Diabetes ( |
26 (12.68%) |
Hypertension ( |
100 (48.78%) |
COPD ( |
43 (20.98%) |
Myocardiopathy ( |
94 (45.85%) |
Serum creatinine (mg/dL) | 0.855 (0.44–2.0) |
EF (%)* |
|
EDV (mL)* | 154 (55–180) |
Urine albumin ( |
16 (7.80%) |
Systolic arterial pressure (SAP) mmH |
|
Diastolic arterial pressure (DAP) mmH |
|
Mean arterial pressure (MAP) mmH |
|
Heart Rate |
|
Haematocrit (%) |
|
BMI: Body Mass Index; COPD: chronic obstructive pulmonary disease;
EF: ejection fraction; EDV: end-diastolic volume.
Among the preoperative risk factors, age, BMI, ASA grading, smoking, diabetes, serum creatinine, sonographic end-diastolic volume, and haematocrit resulted significantly correlated with postawakening
Risk factors and
Global population | Cardiothoracic population | |||||
---|---|---|---|---|---|---|
|
|
|
|
|
| |
|
145 | 60 | 80 | 42 | ||
Male ( |
101 (69.66%) | 38 (63.33%) | 0.378 | 57 (71.25%) | 29 (69.05%) | 0.800 |
Age (years) |
|
|
0.045 |
|
|
0.388 |
BMI (Kg/m2 body surface area) |
|
|
0.020 |
|
|
0.092 |
ASA (3-4) | 65 (44.83%) | 37 (61.67%) | 0.028 | 48 (60.00%) | 28 (66.67%) | 0.470 |
Smoking ( |
62 (42.76%) | 36 (60.00%) | 0.025 | 32 (40.00%) | 26 (61.90%) | 0.021 |
Diabetes ( |
13 (8.97%) | 13 (27.67%) | 0.020 | 7 (8.75%) | 6 (14.29%) | 0.367 |
Hypertension ( |
65 (44.83%) | 35 (58.33%) | 0.078 | 35 (43.75%) | 23 (57.76%) | 0.247 |
COPD ( |
28 (19.31%) | 15 (25.00%) | 0.363 | 14 (17.50%) | 7 (16.67%) | 1.000 |
Myocardiopathy ( |
61 (42.07%) | 33 (55.00%) | 0.091 | 41 (51.25%) | 23 (54.76%) | 0.712 |
Serum creatinine (mg/dL) |
|
|
0.005 |
|
|
0.029 |
EF (%) |
|
|
0.127 |
|
|
0.149 |
EDV (mL) |
|
|
0.049 |
|
|
0.124 |
Urine albumin ( |
8 (5.52%) | 8 (13.33%) | 0.083 | 5 (6.25%) | 5 (11.90%) | 0.310 |
Systolic arterial pressure (SAP) mmHg |
|
|
0.813 |
|
|
0.274 |
Diastolic arterial pressure (DAP) mmHg |
|
|
0.164 |
|
|
0.013 |
Mean arterial pressure (MAP) mmHg |
|
|
0.204 |
|
|
0.058 |
Heart Rate (bpm) |
|
|
0.518 |
|
|
0.744 |
Haematocrit (%) |
|
|
0.030 |
|
|
0.014 |
Surgical APGAR score (points) | 7 (1–10) | 7 (1–10) | 0.520 | 6 (1–10) | 6.5 (1–10) | 0.913 |
Blood pressure and heart rate were recorded when patients arrived in operative room but before any drug administration.
Surgical Apgar Score was calculated at the end of operation as it considers three items that have to be recorded after surgery completion.
None of the intraoperative differences between the two groups of RRI, regarding hemodynamics, blood-gas analysis (serum Lactate included), and fluid balance were found. Also pO2/FiO2 ratio difference, 314 (73–707) in
We did not observe any patient with signs of sepsis, severe sepsis, or septic shock at time of RRI measurement.
Out of the 205 patients, 60 (29.3%; CI 23.0%–35.5%) showed
Table
Outcome results and RRI.
Global population | Cardiothoracic population | |||||
---|---|---|---|---|---|---|
|
|
|
|
|
| |
|
145 | 60 | 80 | 42 | ||
Global complications | 27 (18.62%) | 19 (31.67%) | 0.042 | 14 (17.50%) | 15 (35.71%) | 0.042 |
Suture leak | 2 (1.38%) | 2 (3.33%) | 0.582 | 0 | 0 | |
Bleeding | 4 (2.76%) | 1 (1.67%) | 1.000 | 3 (3.75%) | 0 | 0.550 |
ARDS | 1 (0.69%) | 3 (5.00%) | 0.076 | 1 (1.25%) | 3 (7.14%) | 0.117 |
Pneumonia | 4 (2.76%) | 7 (11.67%) | 0.016 | 1 (1.25%) | 6 (14.29%) | 0.007 |
Atelectasis | 3 (2.07%) | 3 (5.00%) | 0.361 | 1 (1.25%) | 3 (7.14%) | 0.117 |
SIRS/Sepsis | 2 (1.38%) | 4 (6.67%) | 0.062 | 2 (2.50%) | 4 (9.52%) | 0.180 |
Septic shock | 1 (0.69%) | 6 (10.00%) | 0.003 | 0 | 4 (9.52%) | 0.013 |
ARF | 2 (1.38%) | 8 (13.33%) | 0.001 | 2 (2.50%) | 7 (16.67%) | 0.008 |
Pulmonary embolism | 0 | 1 (1.67%) | 0.293 | 0 | 1 (2.38%) | 0.344 |
Acute respiratory failure | 4 (2.76%) | 2 (3.33%) | 1.000 | 1 (1.25%) | 2 (4.76%) | 0.272 |
Hepatic insufficiency | 1 (0.69%) | 0 | 1.000 | 0 | 0 | |
Arrhythmia | 8 (5.52%) | 5 (8.33%) | 0.530 | 6 (7.50%) | 4 (9.52%) | 0.735 |
ICU admission ( |
56 (38.62%) | 24 (40.00%) | 0.854 | 33 (41.25%) | 18 (42.86%) | 0.864 |
ICU staying (days) | 1 (1–36) | 4 (1–38) | 0.001 | 3 (1–36) | 5.5 (2–38) | 0.006 |
Mechanical ventilation ( |
53 (36.55%) | 19 (31.67%) | 0.505 | 33 (41.25%) | 17 (40.48%) | 0.934 |
Mechanical ventilation (hours) | 12 (1–240) | 32 (6–300) | 0.004 | 12 (1–240) | 32 (6–300) | 0.001 |
Length-of-stay (days) | 8 (1–37) | 8 (4–40) | 0.246 | 8 (1–22) | 8 (4–24) | 0.023 |
Death ( |
2 (1.38%) | 3 (5.00%) | 0.151 | 1 (1.25%) | 2 (4.76%) | 0.272 |
Complications that did not occur are not reported. Some patients experienced more than 1 adverse event.
Also in cardiothoracic population we observed an association between RRI and complications (
Neither the general nor the cardiothoracic population showed difference regarding mortality
Furthermore, we explored the risk of complications both for septic shock and for pneumonia. Then we divided our population in five classes according to RRI ranges: (1)
RRI classes and complications risk.
Global population ( |
Cardiothoracic subgroup ( | |
---|---|---|
|
1 | 1 |
RRI 0.60–0.65 | OR 1.34 (95% CI 0.39–4.75); |
OR 1.02 (95% CI 0.17–6.06); |
RRI 0.66–0.70 | OR 1.92 (95% CI 0.57–6.51); |
OR 1.38 (95% CI 0.25–7.67); |
RRI 0.71–0.75 | OR 2.93 (95% CI 0.79–10.9); |
OR 3.38 (95% CI 0.59–19.4); |
|
OR 3.10 (95% CI 0.85–11.3); |
OR 2.75 (95% CI 0.47–16.0); |
When
The ROC curve.
We did not report results about BNP because most of the enrolled patients did not receive the specific blood sampling as planned.
Our study highlighted that patients who have postoperative
The relationship between
Pinto et al., in an animal model, found that sepsis induces AKI by endothelial injury with hemodynamic dysfunction, release of inflammatory mediators, and reactive oxygen species (ROS) generation by tubular cells, in association with renal vasoconstriction due to hemodynamic and inflammatory disturbances, [
Recently, Futier et al. showed that protective mechanical ventilation in a mixed surgical population reduces the risk of postoperative complications (pneumonia, SIRS, and septic shock) probably due to its lower stimulation of inflammatory cascade [
Dewitte et al., found that RRI is unable to determine optimal mean arterial pressure at ICU admission of septic patients, [
Surgical APGAR Score (SAS) is a validated system to predict perioperative morbidity, based on three intraoperative variables: bleeding, the lowest MAP, and heart rate observed [
In high-risk surgery, the identification of patients who may benefit from postoperative observation and monitoring is an important issue both for patient safety and for a correct management of ICU resources [
Cardiothoracic subgroup of patients showed similar results. Then we may speculate that RRI is not affected by surgical manipulation. Nonetheless it could be another starting point for further studies. Finally, despite that they did not undergo abdominal surgery operations, we chose to not consider neurosurgical patients together with cardiothoracic subjects as central nervous system has a specific regulation of vascular resistance that could be a confounding factor of our results; even they consisted only of two patients. For this reason we preferred to include them in the general population.
Our study has some limitations.
First, despite that our analysis found that
Second, we enrolled a mixed population of patients undergoing different surgery; it may be a misleading factor.
Third, we considered cardiac-surgery population apart as patients had not surgically manipulated the splanchnic circulation, but we know the consequences of cardio-pulmonary circulation in terms of systemic inflammatory reaction, kidney injury, and haemodynamics.
In conclusion we may say that
The authors declare that there is no conflict of interests regarding the publication of this paper.