Michel van Genderen

The relation of near-infrared spectroscopy with changes in peripheral circulation in critically ill patients

Objective:We conducted this observational study to investigate tissue oxygen saturation during a vascular occlusion test in relationship with the condition of peripheral circulation and outcome in critically ill patients. Design:Prospective observational study. Setting:Multidisciplinary intensive care unit in a university hospital. Patients:Seventy-three critically ill adult patients admitted to the intensive care unit. Interventions:None. Measurements and Main Results:Patients were followed every 24 hrs until day 3 after intensive care admission. Near-infrared spectroscopy was used to measure thenar tissue oxygen saturation, tissue oxygen saturation deoxygenation rate, and tissue oxygen saturation recovery rate after the vascular occlusion test. Measurements included heart rate, mean arterial pressure, forearm-to-fingertip skin-temperature gradient, and physical examination of peripheral perfusion with capillary refill time. Patients were stratified according to the condition of peripheral circulation (abnormal: forearm-to-fingertip skin-temperature gradient ≥4 and capillary refill time >4.5 secs). The outcome was defined based on the daily Sequential Organ Failure Assessment score and blood lactate levels. Upon intensive care unit admission, 35 (47.9%) patients had abnormal peripheral perfusion (forearm-to-fingertip skin-temperature gradient >4 or capillary refill time >4.5 secs). With the exception of the tissue oxygen saturation deoxygenation rate, tissue oxygen saturation baseline and tissue oxygen saturation recovery rate were statistically lower in patients who exhibited abnormal peripheral perfusion than in those with normal peripheral perfusion: 72 ± 9 vs. 81 ± 9; p = .001 and 1.9 ± 0.7 vs. 3.2 ± 0.9; p = .001, respectively. When a mixed-model analysis was performed over time for estimate (s) calculation, adjusted to the condition of disease, we did not find a significant clinical effect between vascular occlusion test-derived tissue oxygen saturation measurements (as response variables) and mean systemic hemodynamic variables (as independent variables): tissue oxygen saturation vs. heart rate: s (95% confidence interval) = 0.007 (–0.08; 0.09); tissue oxygen saturation vs. mean arterial pressure: s (95% confidence interval) = –0.02 (–0.12; 0.08); tissue oxygen saturation deoxygenation rate vs. heart rate: s (95% confidence interval) = 0.002 (–0.0004; 0.006); tissue oxygen saturation deoxygenation rate vs. mean arterial pressure: s (95% confidence interval) – 0.0007 (–0.003; 0.004); tissue oxygen saturation recovery rate vs. heart rate: s (95% confidence interval) = –0.009 (–0.02; –0.0015); tissue oxygen saturation recovery rate vs. mean arterial pressure: s (95% confidence interval) = 0.01 (0.002; 0.018). However, there was a strong association between tissue oxygen saturation baseline and tissue oxygen saturation recovery rate with abnormal peripheral perfusion: tissue oxygen saturation vs. abnormal peripheral perfusion: s (95% confidence interval) = –10.1 (–13.9; –6.2); tissue oxygen saturation recovery rate vs. abnormal peripheral perfusion: s (95% confidence interval) =−10.1 (−13.9; −6.2); tissue oxygen saturation recovery rate vs. abnormal peripheral perfusion: s (95% confidence interval) = −1.1 (−1.4; −0.81). Poor outcome was more closely related to abnormalities in peripheral perfusion than to tissue oxygen saturation-derived parameters. Conclusions:We found that the condition of peripheral circulation in critically ill patients strongly influences tissue oxygen saturation resting values and the tissue oxygen saturation reoxygenation rate but not the tissue oxygen saturation deoxygenation rate. In addition, changes in near-infrared spectroscopy-derived variables were independent of condition of disease and were not accompanied by any major differences in systemic hemodynamic variables.

Persistent peripheral and microcirculatory perfusion alterations after out-of-hospital cardiac arrest are associated with poor survival*

Objective: To evaluate sublingual microcirculatory and peripheral tissue perfusion parameters in relation to systemic hemodynamics during and after therapeutic hypothermia following out-of-hospital cardiac arrest. Design: Prospective observational study. Setting: Intensive cardiac care unit at a university teaching hospital. Subjects: We followed 80 patients, of whom 25 were included after out-of-hospital cardiac arrest. Intervention: In all patients, we induced therapeutic hypothermia to 33°C during the first 24 hrs of admission. Measurements and Main Results: Complete hemodynamic measurements were obtained directly on intensive cardiac care unit admission (baseline), during induced hypothermia (T1), directly after rewarming (T2), and another 24 hrs later (T3). In addition, the sublingual microcirculation was observed using sidestream dark-field imaging, and peripheral tissue perfusion was monitored with the peripheral perfusion index, capillary refill time, tissue oxygen saturation, and forearm-to-fingertip skin temperature gradient. During hypothermia, all sublingual microcirculatory parameters decreased significantly together with peripheral capillary refill time and the peripheral perfusion index, followed by a significant increase at T2. Changes in sublingual and peripheral tissue perfusion parameters were significantly related to changes in central body temperature, but not to changes in systemic hemodynamic variables such as cardiac index or mean arterial pressure. Surprisingly, these parameters were significantly lower in nonsurvivors (n = 6) at admission and after rewarming. Persistent alterations in these parameters were related with the prevalence of organ dysfunction and were highly predictive of mortality. Conclusions: Following out-of-hospital cardiac arrest, the early postresuscitation phase is characterized by abnormalities in sublingual microcirculation and peripheral tissue perfusion, which are caused by vasoconstriction due to induced systemic hypothermia and not by impaired systemic blood flow. Persistence of these alterations is associated with organ failure and death, independent of systemic hemodynamics.

Microvascular perfusion as a target for fluid resuscitation in experimental circulatory shock.

Objectives:To study regional perfusion during experimental endotoxemic and obstructive shock and compare the effect of initial cardiac output-targeted fluid resuscitation with optimal cardiac output-targeted resuscitation on different peripheral tissues. Design:Controlled experimental study. Setting:University-affiliated research laboratory. Subjects:Fourteen fasted anesthetized mechanically ventilated domestic pigs. Interventions:Domestic pigs were randomly assigned to the endotoxemic (n = 7) or obstructive shock (n = 7) model. Central and regional perfusion parameters were obtained at baseline, during greater than or equal to 50% reduction of cardiac output (T1), after initial resuscitation to baseline (T2), and after optimization of cardiac output (T3). Measurements and Main Results:Regional perfusion was assessed in the sublingual, intestinal, and muscle vascular beds at the different time points and included visualization of the microcirculation, measurement of tissue oxygenation, and indirect assessments of peripheral skin perfusion. Hypodynamic shock (T1) simultaneously decreased all regional perfusion variables in both models. In the obstructive model, these variables returned to baseline levels at T2 and remained in this range after T3, similar to cardiac output. In the endotoxemic model, however, the different regional perfusion variables were only normalized at T3 associated with the hyperdynamic state at this point. The magnitude of changes over time between the different vascular beds was similar in both models, but the endotoxemic model displayed greater heterogeneity between tissues. Conclusions:This study demonstrates that the relationship between the systemic and regional perfusion is dependent on the underlying cause of circulatory shock. Further research will have to demonstrate whether different microvascular perfusion variables can be used as additional resuscitation endpoints.

Clinical assessment of peripheral perfusion to predict postoperative complications after major abdominal surgery early: A prospective observational study in adults

IntroductionAltered peripheral perfusion is strongly associated with poor outcome in critically ill patients. We wanted to determine whether repeated assessments of peripheral perfusion during the days following surgery could help to early identify patients that are more likely to develop postoperative complications.MethodsHaemodynamic measurements and peripheral perfusion parameters were collected one day prior to surgery, directly after surgery (D0) and on the first (D1), second (D2) and third (D3) postoperative days. Peripheral perfusion assessment consisted of capillary refill time (CRT), peripheral perfusion index (PPI) and forearm-to-fingertip skin temperature gradient (Tskin-diff). Generalized linear mixed models were used to predict severe complications within ten days after surgery based on Clavien-Dindo classification.ResultsWe prospectively followed 137 consecutive patients, from among whom 111 were included in the analysis. Severe complications were observed in 19 patients (17.0%). Postoperatively, peripheral perfusion parameters were significantly altered in patients who subsequently developed severe complications compared to those who did not, and these parameters persisted over time. CRT was altered at D0, and PPI and Tskin-diff were altered on D1 and D2, respectively. Among the different peripheral perfusion parameters, the diagnostic accuracy in predicting severe postoperative complications was highest for CRT on D2 (area under the receiver operating characteristic curve = 0.91 (95% confidence interval (CI) = 0.83 to 0.92)) with a sensitivity of 0.79 (95% CI = 0.54 to 0.94) and a specificity of 0.93 (95% CI = 0.86 to 0.97). Generalized mixed-model analysis demonstrated that abnormal peripheral perfusion on D2 and D3 was an independent predictor of severe postoperative complications (D2 odds ratio (OR) = 8.4, 95% CI = 2.7 to 25.9; D2 OR = 6.4, 95% CI = 2.1 to 19.6).ConclusionsIn a group of patients assessed following major abdominal surgery, peripheral perfusion alterations were associated with the development of severe complications independently of systemic haemodynamics. Further research is needed to confirm these findings and to explore in more detail the effects of peripheral perfusion–targeted resuscitation following major abdominal surgery.

Serum C-reactive protein as a predictor of morbidity and mortality in intensive care unit patients after esophagectomy.

BACKGROUND Serum C-reactive protein (CRP) is an acute-phase protein, synthesized during any proinflammatory response in the body. Preoperative elevation of serum CRP has been reported to be a prognostic indicator in oncologic surgery. The aim of this study was to investigate the value of postoperative serum CRP elevation as a prognostic parameter in patients undergoing elective esophagectomy followed by routine admission to the intensive care unit (ICU). METHODS In a prospective follow-up cohort study, data were collected of 63 patients admitted to the ICU after elective esophagectomy surgery from October 2007 to December 2008. Postoperative serum CRP levels were determined at the moment of admission to the ICU, 24, 48, and 72 hours postoperatively, and the relation with the development of complications and the 1-year survival status was investigated. RESULTS In postoperative esophagectomy patients admitted to the ICU, CRP levels at T24 and T48 were significantly higher in the patients who developed postoperative complications, which in itself was associated with lower 1-year survival. CONCLUSIONS In patients undergoing esophagectomy with gastric tube reconstruction, increased CRP levels were associated with the occurrence of postoperative complications and higher 1-year mortality. Postoperative serum CRP levels can easily be monitored in the ICU in order to identify patients at risk for the development of postoperative complications; future research is needed to determine whether these complications can be prevented and improve outcome.

Peripheral perfusion index as an early predictor for central hypovolemia in awake healthy volunteers

BACKGROUND:In healthy volunteers, we investigated the ability of the pulse oximeter–derived peripheral perfusion index (PPI) to detect progressive reductions in central blood volume. METHODS:Twenty-five awake, spontaneously breathing, healthy male volunteers were subjected to progressive reductions in central blood volume by inducing stepwise lower body negative pressure (LBNP) with 20 mm Hg for 5 minutes per step, from 0 to −20, −40, −60, and back to 0 mm Hg. Throughout the procedure, stroke volume (SV), heart rate (HR), and mean arterial blood pressure were recorded using volume-clamp finger plethysmography. Assessment of the PPI was done by pulse oximetry. Additionally, the forearm-to-fingertip skin-temperature gradient was measured. Data are presented as mean ± SE. PPI underwent log transformation and is presented as median (25th–75th). RESULTS:Of the 25 subjects, one did not complete the study because of cardiovascular collapse. After the first LBNP step (−20 mm Hg), PPI decreased from 2.2 (1.6–3.3) to 1.2 (0.8–1.6) (P = 0.007) and SV decreased from 116 ± 3.0 mL to 104 ± 2.6 mL (P = 0.02). The magnitude of the PPI decrease (41% ± 6.0%) was statistically different from that observed for SV (9% ± 1.3%) and HR (3% ± 1.9%). During progression of LBNP, SV decreased and HR increased progressively with the increased applied negative pressure, whereas the PPI remained low throughout the remainder of the protocol and returned to baseline values when LBNP was released. At −60 mm Hg LBNP, SV decreased and HR increased by 36% ± 0.9 % and 33% ± 2.4% from baseline, respectively. Mean arterial blood pressure remained in the same range throughout the experiment. CONCLUSIONS:These results indicate that the pulse oximeter–derived PPI may be a valuable adjunct diagnostic tool to detect early clinically significant central hypovolemia, before the onset of cardiovascular decompensation in healthy volunteers.

Monitoring peripheral perfusion in critically ill patients at the bedside.

Purpose of reviewThe goal of circulatory monitoring is the use of an accurate, continuous and noninvasive method that can easily assess tissue perfusion under clinical conditions. As peripheral tissues are sensitive to alterations in perfusion, the noninvasive monitoring of peripheral circulation could be used as an early marker of systemic haemodynamic derangement. We, therefore, aim to discuss the currently available methods that can be used at the bedside as well as the role of peripheral perfusion monitoring in critically ill patients. Recent findingsThe deterioration of peripheral circulation has frequently been observed in critically ill patients with the use of subjective assessment and several optical techniques. In various patient categories, more severe and persistent alterations have been associated with worse outcomes, and these associations were independent of systemic haemodynamic parameters. Interventions aimed at systemic parameters have an unpredictable effect on peripheral circulation parameters, especially during hyperdynamic conditions. Thus, it appears that changes in peripheral perfusion reflect changes in regional vasomotor tone rather than systemic blood flow. SummarySubjective assessments and optical techniques provide important information regarding peripheral circulation. Moreover, these techniques are relatively easy to implement and interpret at the bedside and can be applied during acute conditions. Further research is warranted to investigate the effects of therapeutic interventions on peripheral perfusion parameters and patient outcome.

Two-Lung High-Frequency Jet Ventilation as an Alternative Ventilation Technique During Transthoracic Esophagectomy

OBJECTIVE The aim of this study was to evaluate two-lung high-frequency jet ventilation during esophagectomy and evaluate the influence of high-frequency jet ventilation on pulmonary complications as compared with one-lung ventilation. DESIGN A retrospective study. SETTINGS A single-center study in a university hospital. PARTICIPANTS The authors analyzed the data of patients who had undergone an elective esophagectomy by transthoracic esophagectomy between January 2000 and December 2006. INTERVENTION The patients had undergone a cervicothoracoabdominal subtotal esophagectomy via a right-sided thoracotomy. Patients with high-frequency jet ventilation were intubated with a single-lumen endotracheal tube, and an oxygen insufflation catheter was placed inside the endotracheal tube and connected to a high-frequency jet ventilator. MEASUREMENTS AND MAIN RESULTS Eighty-seven patients were enrolled, 30 with high-frequency jet ventilation and 57 with 1-lung ventilation. Both groups were adequately oxygenated, but patients in the one-lung ventilation group had a higher PaCO2 (42.75 +/- 7.5 mm Hg) compared with that for the high-frequency jet ventilation group (35.25 +/- 8.25 mm Hg) (p < 0.05). There were no differences in postoperative respiratory complications between the 2 groups. Mean blood loss was significantly lower for patients in the high-frequency jet ventilation group (1,243 +/- 787 mL). CONCLUSIONS High-frequency jet ventilation to 2 lungs, using a single-lumen tube, is a safe and adequate ventilation technique for use during esophagectomy. High-frequency jet ventilation had no influence on the incidence of postoperative pulmonary complications but reduced perioperative blood loss and led to a decreased need for fluid replacement.

The effects of intravenous nitroglycerine and norepinephrine on gastric microvascular perfusion in an experimental model of gastric tube reconstruction

BACKGROUND Esophagectomy with gastric tube reconstruction is the surgical treatment for cancer of the esophagus. Perfusion of the anastomotic site of the tube depends exclusively on microcirculation, making it susceptible to hypoperfusion. It is unknown whether vasodilatation is superior to increased perfusion pressure to improve gastric tissue perfusion of the anastomosis. METHODS We performed a gastric tube reconstruction in 12 pigs, mean body weight 32 +/- 2 kg. Besides systemic hemodynamic parameters, gastric microvascular blood flow (MBF) was assessed with laser Doppler flowmetry and gastric microvascular HbO(2) saturation (microHbSO(2)) and Hb concentration (microHbcon) with spectrophotometry. Animals were randomized over 2 groups: with and without intravenous nitroglycerin (NTG). In both groups, mean arterial pressure (MAP) was increased from 50 to 110 mmHg with infusion of norepinephrine; in the NTG group, central venous pressure was maintained below 10 mmHg throughout the experiment with NTG. RESULTS Except for central venous and pulmonary capillary wedge pressures, all hemodynamic parameters were similar in both groups. Especially in corpus and fundus, MBF decreased following surgery. However, overall MBF was significantly higher in the NTG group. Increasing MAP had no effect on fundus MBF. Gastric microHbSO(2) and microHbcon were not different between groups and did not change at higher MAP levels. CONCLUSION In our experimental model of gastric tube reconstruction, tissue perfusion is severely compromised; this effect is aggravated by systemic hypotension independent from cardiac output. Impaired venous outflow might contribute to this effect and can be counteracted with infusion of nitroglycerine.

Interrater Reliability and Diagnostic Performance of Subjective Evaluation of Sublingual Microcirculation Images by Physicians and Nurses: A Multicenter Observational Study.

ABSTRACT Introduction: This was a cross-sectional multicenter study to investigate the ability of physicians and nurses from three different countries to subjectively evaluate sublingual microcirculation images and thereby discriminate normal from abnormal sublingual microcirculation based on flow and density abnormalities. Methods: Forty-five physicians and 61 nurses (mean age, 36 ± 10 years; 44 males) from three different centers in The Netherlands (n = 61), Uruguay (n = 12), and Japan (n = 33) were asked to subjectively evaluate a sample of 15 microcirculation videos randomly selected from an experimental model of endotoxic shock in pigs. All videos were first analyzed offline using the A.V.A. software by an independent, experienced investigator and were categorized as good, bad, or very bad microcirculation based on the microvascular flow index, perfused capillary density, and proportion of perfused capillaries. Then, the videos were randomly assigned to the examiners, who were instructed to subjectively categorize each image as good, bad, or very bad. An interrater analysis was performed, and sensitivity and specificity tests were calculated to evaluate the proportion of A.V.A. score abnormalities that the examiners correctly identified. Results: The &kgr; statistics indicated moderate agreement in the evaluation of microcirculation abnormalities using three categories, i.e., good, bad, or very bad (&kgr; = 0.48), and substantial agreement using two categories, i.e., normal (good) and abnormal (bad or very bad) (&kgr; = 0.66). There was no significant difference between the &kgr; three and &kgr; two statistics. We found that the examiner’s subjective evaluations had good diagnostic performance and were highly sensitive (84%; 95% confidence interval, 81%–86%) and specific (87%; 95% confidence interval, 84%–90%) for sublingual microcirculatory abnormalities as assessed using the A.V.A. software. Conclusions: The subjective evaluations of sublingual microcirculation by physicians and nurses agreed well with a conventional offline analysis and were highly sensitive and specific for sublingual microcirculatory abnormalities.