Whether or not to administer intravenous (iv) fluid is a common, difficult, and controversial challenge in clinical practice. The main aim of fluid therapy during surgery or critical illness is to provide adequate tissue perfusion by increasing stroke volume (SV) or cardiac output (CO). Goal-directed fluid therapy aiming to increase oxygen (O2) delivery reduces morbidity and mortality in various clinical settings [
Photoplethysmography (more specifically pulse oximetry plethysmographic waveform analysis) as a noninvasive tool in evaluation of fluid responsiveness was first described by Partridge [
This paper is based on searches performed in PubMed, Medline, and Embase on November 10, 2011 with the following search criteria: “(pulse oximetry OR plethysmographic OR Pleth variability index OR PVI) AND ((fluid responsiveness) OR (volume status)).” The searches generated 217 hits. Papers were checked for relevant references and 22 [ reporting predictive values of ΔPOP and/or PVI after fluid challenges and/or reporting correlations between ΔPOP, PVI, and ΔPP, mechanically ventilated patients, written in English.
14 studies performed fluid challenges and these are summarized in Table
Papers in which ΔPOP and/or PVI have been evaluated and fluid challenges performed.
Author, Ref. | Fluid challenge | CO/CI/SVI measurement | Responder | ROC | Threshold value | Sens/spec |
---|---|---|---|---|---|---|
Solus-Biguenet et al. [ | 250 mL colloid | Thermodilution | SVI: 10% | 0.81 | PPVfina: 14% | No data |
0.68 | ΔPOP: 9.5% | No data | ||||
0.79 | PPVart: 12.5% | No data | ||||
Natalini et al. [ | 500 mL HES 6% | Thermodilution | CI: 15% | 0.72 | ΔPOP: 15% | 56/86 (PPV/NPV) |
0.74 | ΔPP: 15% | 55/100 (PPV/NPV) | ||||
Cannesson et al. [ | 500 mL HES 6% | Thermodilution | CI: 15% | 0.847 | ΔPOP: 13% | 93/90 |
0.847 | ΔPP: 11% | 80/90 | ||||
Feissel et al. [ | 8 mL/kg HES 6% | Echo-Doppler | CI: 15% | 0.94 | ΔPP: 12% | 100/70 |
0.94 | ΔPOP: 14% | 94/80 | ||||
Wyffels et al. [ | 500 mL HES 6% | Intermittent thermodilution | CO: 15% | 0.94 | PPV: 11.3% | 95/91.7 |
by pulm. artery catheter | 0.89 | ΔPOP: 11.3% | 90/83.3 | |||
Cannesson et al. [ | 500 mL HES 6% | Thermodilution | CI: 15% | 0.94 | ΔPP: 12.5% | 87/89 |
0.94 | ΔPOP: 12% | 87/89 | ||||
0.93 | PVI: 14% | 81/100 | ||||
Westphal et al. [ | 500–1000 mL NaCl | Not measured | ΔPP > 13% | 0.95 | ΔPOP: 11% | 91/100 |
Zimmermann et al. [ | 7 mL/kg HES 6% | FloTrac | SVI: 15% | 0.97 | PVI: 9.5 % | 93/100 |
Loupec et al. [ | 500 mL HES | Echocardiography | CO: 15% | 0.88 | PVI: 17% | 95/91 |
or PLR if ΔPP < 13% | ||||||
Desgranges et al. [ | 500 mL HES | Thermodilution | CI: 15% | 0.91 | PVIforehead : 15% | 89/78 |
0.88 | PVIear: 16% | 74/74 | ||||
0.84 | PVIfinger : 12% | 74/67 | ||||
0.84 | PPV > 11% | 74/89 | ||||
PVIforehead : 15% | 89/100 | |||||
and PIforehead : 1.37 | ||||||
Renner et al. [ | HES 10 mL kg−1 | Transoesophageal echocardiography | SVI: 15% | 0.79 | PVI > 13% | 84/64 |
De Souza Neto et al. [ | Saline, 20 mL/kg | Transthoracic echography | AVTI: 15% | 0.51 | 0–6 yr: ΔPOP | No data |
(aortic velocity-time integral) | 0.63 | 0–6 yr: PVI | No data | |||
0.71 | 0–6 yr: ΔPP | No data | ||||
0.52 | 0–6 yr: PPV | No data | ||||
0.57 | 6–14 yr: ΔPOP | No data | ||||
0.54 | 6–14 yr: PVI | No data | ||||
0.60 | 6–14 yr: ΔPP | No data | ||||
0.60 | 6–14 yr: PPV | No data | ||||
Hoiseth et al. [ | 250 mL colloid | Esophageal doppler | SV ≥ 15% | 0.67 | ΔPP: 8.8% | 82/67 |
0.72 | ΔPOP: 11.4% | 86/67 | ||||
Hood and wilson [ | 500 mL colloid | Esophageal doppler | SV ≥ 10% | 0.96 | PVIfinger (baseline) 10% | 86/100 |
0.98 | PVIearlobe (baseline) 9.5% | 95/100 | ||||
0.71 | PVIfinger (during surgery) 10% | 65/67 | ||||
0.54 | PVIearlobe (during surgery) |
ΔPOP: pulse oximetry plethysmography; ΔPP: pulse pressure; PVI: Pleth variability index; CI: cardiac index; SV: stroke volume; SVI: stroke volume index; SVV: stroke volume variation; CO: cardiac output; PPVfina: pulse pressure variation obtained with Finapres; PPVart: pulse pressure variation obtained with intraarterial equipment; PPV/NPV: positive predictive value/negative predictive value.
Papers in which correlations between ΔPOP, PVI, and ΔPP have been investigated.
Author, Ref. | Relation | Correlation | Pulse oximeter/monitor |
---|---|---|---|
Cannesson et al. [ | ΔPOP-ΔPP | M1190A, Philips, Suresnes, France | |
Natalini et al. [ | ΔPOP-ΔPP | Datex-Engstrom CS/3 Critical Care Monitor, Instrumentarium, Helsinki, Finland | |
Cannesson et al. [ | ΔPOP-ΔPP | Oxymax Tyco Healthcare Group LP, Pleasanton, CA, USA | |
Intellivue MP70, Philips Medical Systems, Suresnes, France | |||
Landsverk et al. [ | ΔPOP-ΔPP | OxiMax 451N5, Nellcor, Boulder, CO, USA | |
Cannesson et al. [ | ΔPOP-PVI | LNOP Adt, Masimo Corp., Irvine, CA, USA | |
PVI-ΔPP | Oxymax, Tyco Healthcare Group LP, Pleasanton, CA, USA | ||
ΔPOP-ΔPP | Intellivue MP70, Philips Medical Systems, Suresnes, France | ||
Pizov et al. [ | ΔPOP-ΔPP | Datex-Ohmeda AS-3, Datex, Helsinki, Finland | |
Desebbe et al. [ | PVI VT = 6-PVI VT = 10 | 9%–12%, | LNOP Adt, Masimo Corp., Irvine, CA, USA |
PVIPEEP- PVInon - PEEP | (Significant change) | ||
Biais et al. [ | PVI-ΔPP | LNOP Adt, Masimo Corp., Irvine, CA, USA | |
PVINE(+)-ΔPP | Masimo Radical 7 monitor, Masimo SET, Masimo Corp., Irvine, CA, USA | ||
PVINE(−)-ΔPP | |||
Solus-Biguenet et al. [ | No data | ||
Natalini et al. [ | Datex-Engstrom CS/3 Critical Care Monitor, Instrumentarium, Helsinki, Finland | ||
Cannesson et al. [ | ΔPOP-ΔPP | Oxymax Tyco Healthcare Group LP, Pleasanton, CA, USA | |
Intellivue MP70, Philips Medical Systems, Suresnes, France | |||
Feissel et al. [ | ΔPOP-ΔPP | SpO2/Pleth, M3150A technology, Philips Medical Systems, Andover, MA, USA | |
Wyffels et al. [ | Monitor Hewlett Packard M1166A model G65 | ||
Cannesson et al. [ | ΔPOP-PVI | LNOP Adt, Masimo Corp., Irvine, CA, USA, with Masimo Radical 7, 7.0.3.3 | |
Oxymax, Tyco Healthcare Group LP, Pleasanton, CA, USA | |||
Westphal et al. [ | ΔPOP-ΔPP | S/5, Datex-Ohmeda, Helsinki, Finland | |
Zimmermann et al. [ | LNCS, Masimo Corp., Irvine, CA, USA, Masimo Radical-7 monitor, 7.0.3.3 | ||
Loupec et al. [ | PVIbaseline -ΔPPbaseline | LNCS Adtx, Masimo corp., Irvine, CA, USA | |
Desgranges et al. [ | LNOP Adt, Masimo Corp., Irvine, CA, USA | ||
LNOP TC-I, Masimo Corp., Irvine, CA, USA | |||
LNOP TF-I, Masimo Corp., Irvine, CA, USA | |||
Masimo Radical 7, Masimo SET, Masimo Corp., version 7.1.1.5 | |||
Renner et al. [ | Masimo Rainbow SET, Masimo Corp., Radical 7, V7.6.2.2 | ||
De Souza et al. [ | ΔPOP-PVI | Oxymax | |
ΔPOP-ΔPP | LNOP, Masimo Corp., Irvine, CA, USA | ||
PVI-PPV | |||
Hoiseth et al. [ | ΔPOP-ΔPP | OxiMax 451N5, Nellcor, Boulder, CO, USA | |
Hood and wilson [ | Masimo Rainbow SET, Masimo Corp., Irvine, CA, USA |
ΔPOP: pulse oximetry plethysmography; ΔPP: pulse pressure; PVI: Pleth variability index; PEEP: positive end expiratory pressure; NE: norepinephrine; VT: tidal volume.
General characteristics.
Author, Ref. | Year | Patient category | Ventilation | Site of meas. | Reg. period | Vasoact. | |
---|---|---|---|---|---|---|---|
Cannesson et al. [ | 2005 | 22 | ICU | Mech. vent. 6–10 mL/kg, volume | Finger | 3 respiratory cycl. | Incl. |
Natalini et al. [ | 2006 | 49 | OR/ICU | Mech. vent. 6–9 mL/kg, volume | Finger/toe | 5 respiratory cycl. | No data |
Cannesson et al. [ | 2007 | 25 | Preop. CABG/AAA | Mech. vent. 8–10 mL/kg, volume | Finger | 3 respiratory cycl. | Excl. |
Gen.anaesthesia | |||||||
Landsverk et al. [ | 2008 | 14 | ICU | Mech. vent. 8 mL/kg, volume/pressure | Finger | 15 min | Incl. |
Cannesson et al. [ | 2008 | 25 | Preop.CABG | Mech. vent. 8–10 mL/kg | Finger | 3 respiratory cycl. | Excl. |
Gen.anaesthesia | |||||||
Pizov et al. [ | 2010 | 33 | Preop. surgery | Mech. vent. 8–10 mL/kg | Finger | 3 min | Incl. |
Desebbe et al. [ | 2010 | 21 | Postop. CABG and ICU | Mech. vent. 6–10 mL/kg, volume | Finger | 3 respiratory cycl. | Excl. |
Biais et al. [ | 2011 | 67 | ICU | Mech. vent. 8 mL/kg, volume | Finger | 3 respiratory cycl. | Incl. |
Solus-Biguenet et al. [ | 2006 | 8 | During hepatic surgery | Mech. vent. 8–10 mL/kg | Finger | 3 respiratory cycl. | No data |
Natalini et al. [ | 2006 | 22 | ICU | Mech. vent. 6–10 mL/kg, volume | Finger | 2 min | No data |
Cannesson et al. [ | 2007 | 25 | Preop. CABG | Mech. vent. 8–10 mL/kg, volume | Finger | 3 respiratory cycl. | Excl. |
Feissel et al. [ | 2007 | 23 | ICU | Mech. vent. 8 mL/kg, pressure | Finger | No data | Incl. |
Wyffels et al. [ | 2007 | 32 | Postop. heart surgery | Mech. vent. 8–10 mL/kg | Finger | 3 respiratory cycl. | No data |
Cannesson et al. [ | 2008 | 25 | Preop.CABG | Mech. vent. 8–10 mL/kg, volume | Finger | 3 respiratory cycl. | Excl. |
Gen.anaesthesia | |||||||
Westphal et al. [ | 2009 | 43 | Postop. heart surgery | Mech. vent. 8–10 mL/kg, volume | Finger | 1 min | Incl. |
Zimmermann et al. [ | 2010 | 20 | Preop. abd. surgery | Mech. vent. 7 mL/kg, volume | Finger | No data | No data |
Loupec et al. [ | 2011 | 40 | Several categories | Mech. vent. 8 mL/kg, volume | Finger | No data | Incl. |
Desgranges et al. [ | 2011 | 28 | Preop. cardiac surgery | Mech. vent. 8 mL/kg, volume | Finger, earlobe | No data | No data |
and forehead | |||||||
Renner et al. [ | 2011 | 27 | Infants preop. cardiac surgery | Mech. vent. 10 mL/kg, volume | No data | No data | Excl. |
Pereira de Souza et al. [ | 2011 | 30 | Children preop neurosurgery | Mech. vent. 10 mL/kg, volume | Finger | 3 respiratory cycl. | Excl. |
Hoiseth et al. [ | 2011 | 25 | During abd. surgery | Mech. vent. 8 mL/kg, volume | Finger | App. 5 min | Incl. |
Hood and wilson [ | 2011 | 25 | During colorectal surgery | Mech. vent. 8–10 mL/kg, volume | Finger/earlobe | No data | No data |
ICU: intensive care unit; OR: operating room; CABG: coronary artery bypass grafting; AAA: abdominal aortic aneurysm
Nine studies calculated areas under receiver operating characteristics curves (ROC curves) for ΔPOP [
Seven studies calculated ROC curves for PVI [
ΔPP is considered to be a good predictor of fluid responsiveness [
Photoplethysmography is applicable on most patient categories and is noninvasive, simple, widely available, and without risk of complications. Several physiological, clinical, and practical factors must be taken into account when evaluating whether or not it is a noninvasive alternative to evaluate fluid responsiveness.
Firstly, there are several physiological prerequisitions for using dynamic variables.
Mechanical ventilation provides the stable and predictable variations in intrathoracic pressure required for photoplethysmography to be accurate. A large mechanical tidal volume will influence intrathoracic pressure to a greater extent than a small tidal volume. It is presumed that the influence of tidal volume reaches significance at >8 mL/kg. It is a challenge that the accuracy of photoplethysmography increases with larger tidal volumes, whereas it is clinically desirable to minimize the tidal volume. The accuracy of photoplethysmography relies on a continuous beat-to-beat-analysis. Thus, patients need to have stable heart rate. Additionally, decreased RV ejection fraction can lead to false-positive variations in pulse pressure [
Secondly, the complex network of correlations between ΔPOP/PVI and ΔPP/other hemodynamic variables varies greatly between different studies. The best correlations are found in studies where short registration periods (3–5 respiratory cycles) have been used and in patients under stable pre- and postoperative conditions. These conditions do not reflect genuine intraoperative instability, the setting where precise guidance of fluid therapy is perhaps most important. The correlations are poorer with longer periods of registration [
Finally, a number of additional factors must be considered. Variations in total peripheral resistance and vasomotor tone increase under the influence of general anesthesia [
A threshold value refers to a value of ΔPOP, ΔPP, or PVI that separates responders from nonresponders. Failure to agree upon a threshold value in clinical settings does not necessarily make the parameters (i.e., PVI or POP) less valuable. Different patient groups may well present with different threshold values. A septic patient may have a threshold value different from that of a hemodynamically stable patient undergoing surgery. In the same way, threshold values may also change pre-, peri-, and postoperatively. Cannesson et al. [
Cut-off values for increases in SV/CO/CI are defined to separate reponders and nonresponders. These thresholds are based on the variability and errors in the chosen measuring technique as well as what change is believed to be clinically important. These thresholds may be more or less arbitrarily chosen and differ between the studies.
Level of intra-abdominal pressure may influence ΔPP and ΔPOP and is relevant in three of the articles included [
In theory, a number of potentially confounding factors exist. Different pulse oximeter-technology, errors due to software autogain features which filter and amplify the raw signal (thus making it unreliable for quantitative analysis), atherosclerosis, type of fluid, skin pigmentation, saturation, movement artefacts, statistical weaknesses, variations in pleural and transpulmonary pressures, and venous components of the pulsatile signal may affect measurements.
We conclude that although photoplethysmography is a promising technique, predictive values and correlations with other hemodynamic variables indicating fluid responsiveness vary substantially. Based on studies using short registration periods photoplethysmography might seem promising for evaluation of volume status. However, in studies using longer registration periods it has been shown that intra- and interindividual variability for ΔPOP is greater than for ΔPP, leading to poor agreement between ΔPOP and ΔPP. Thus, it is not presently evident that photoplethysmography is adequately accurate, valid, and reliable to be included in clinical practice for evaluation of volume status. In future studies it is important to evaluate new hemodynamic methods in clinically relevant settings and to test their reproducibility in clinically relevant time frames. Relatively poor predictive values during ongoing major surgery further underscore this point and results vary in different patient groups. The greatest potential for photoplethysmography in evaluation of volume status might be in settings where invasive monitoring is not indicated.
There is no conflict of interests for any of the authors.