Urine Flow Is a Novel Hemodynamic Monitoring Tool for the Detection of Hypovolemia

Early Postoperative Use of Diuretics After Kidney Transplantation Showed Increase in Delayed Graft Function

PURPOSE

In acute renal injury, diuretics are widely considered to be harmful. Nevertheless, they are used frequently after kidney transplantation. We hypothesized that diuretics administered in the early postoperative treatment after kidney transplantation increase the incidence of delayed graft function (DGF).

METHODS

In this monocentric, retrospective cohort analysis, we screened the closed files of all consecutive patients who underwent kidney transplantation from 2011 to 2017. The outcome variable was DGF, defined as at least 1 hemodialysis within 7 days postoperatively. To stratify for baseline characteristics such as waiting time or cold ischemic period, we employed a propensity score-matched analysis. Further statistical processing included basic descriptive statistics, Mann-Whitney U test, and binary logistic regression analysis.

RESULTS

The unmatched cohort included 445 patients and showed a significantly increased rate of DGF for patients who received either furosemide or mannitol or a combination of both (5% vs 25%; P < .001). Mannitol (odds ratio [OR]: 4.094) and furosemide (OR: 2.915) showed a significant correlation with DGF in the multivariate regression analysis. Propensity score-based matching resulted in a matched cohort of 214 patients with balanced baseline risk variables. In this matched cohort, the rate of DGF was significantly increased in patients who received diuretics in the early postoperative treatment (7% vs 16%; P = .031).

CONCLUSION

Our results show that postoperatively administered diuretics are associated with an increased rate of DGF even in a cohort with balanced preoperative risk variables. This study supports recently published reviews, which call diuretics in the transplantation process into question.

Minute-to-minute urine flow rate variability: a retrospective survey of its ability to provide early warning of acute hypotension in critically ill multiple trauma patients

PURPOSE

Dynamic changes in urine output and neurological status are the recognized clinical signs of hemodynamically significant hemorrhage. In the present study, we analyzed the dynamic minute-to-minute changes in the UFR and also the changes in its minute-to-minute variability in a group of critically ill multiple trauma patients whose blood pressures were normal on admission to the ICU but who subsequently developed hypotension within the first few hours of their ICU admission.

PATIENTS AND METHODS

The study was retrospective and observational. Demographic and clinical data were extracted from the computerized register information systems initially; the clinical and laboratory data of 100 critically ill patients with multiple trauma who were admitted to the ICU during the study period were analyzed. Of this group, ten patients were eventually included in the study on the basis of the inclusion criteria.

RESULTS

The minute-to-minute urine flow rate (UFR) and urine flow rate variability (UFRV) both decreased significantly during the periods of hypotension (p values 0.001 and 0.006, respectively). Notably, the decrease in UFRV preceded by at least 30 min a corresponding decline in the systolic and mean arterial blood pressures, which manifested as a flattening of UFRV amplitude which was observed prior to the occurrence of the lowest recorded systolic and mean arterial blood pressures. Statistical analysis by the Pearson method demonstrated a strong direct correlation between the decrease in UFRV and the decrease in the MAP (R = 0.9, p = 0.001), and SBP (R = 0.86, p = 0.001) and the decreasing urine output per hour (R = 0.88, p < 0.001).

CONCLUSION

We found that changes in UFRV correlate strongly with systolic and mean arterial blood pressures. We feel that this parameter could potentially serve as an early signal of hemodynamic deterioration due to occult bleeding in critically ill trauma patients, and might also be able to identify the optimal end-point of hemodynamic resuscitative measures in these patients.

Robust monitoring of hypovolemia in intensive care patients using photoplethysmogram signals

The paper presents a fingertip photoplethysmography based technique to assess patient fluid status that is robust to waveform artifacts and health variability in the underlying patient population. The technique is intended for use in intensive care units, where patients are at risk for hypovolemia, and signal artifacts and inter-patient variations in health are common. Input signals are preprocessed to remove artifact, then a parameter-invariant statistic is calculated to remove effects of patient-specific physiology. Patient data from the Physionet MIMICII database was used to evaluate the performance of this technique. The proposed method was able to detect hypovolemia within 24 hours of onset in all hypovolemic patients tested, while producing minimal false alarms over non-hypovolemic patients.

Urine flow rate monitoring in hypovolemic multiple trauma patients

Background

The urine output is an important clinical parameter of renal function and blood volume status, especially in critically ill multiple trauma patients. In the present study, the minute-to-minute urine flow rate and its variability were analyzed in hypotensive multiple trauma patients during the first 6 h of their ICU (intensive care unit) stay. These parameters have not been previously reported.

Methods

The study was retrospective and observational. Demographic and clinical data were extracted from the computerized Register Information Systems. A total of 59 patients were included in the study. The patients were divided into two study groups. Group 1 consisted of 29 multiple trauma patients whose systolic blood pressure was greater than 90 mmHg on admission to the ICU and who were consequently deemed to be hemodynamically compromised. Group 2 consisted of 30 patients whose systolic blood pressure was less than 90 mmHg on admission to the ICU and who were therefore regarded as hemodynamically uncompromised.

Results

The urine output and urine flow rate variability during the first 6 h of the patients’ ICU stay was significantly lower in group 2 than in group 1 (p < 0.001 and 0.006 respectively). Statistical analysis by the Pearson method demonstrated a strong direct correlation between decreased urine flow rate variability and decreased urine output per hour (R = 0.17; P = 0.009), decreased mean arterial blood pressure (R = 0.24; p = 0.001), and increased heart rate (R = 0.205; p = 0.001).

Conclusion

These findings suggest that minute-to-minute urine flow rate variability is a reliable incipient marker of hypovolemia and that it should therefore take its place among the parameters used to monitor the hemodynamic status of critically ill multiple trauma patients.

Hemodynamic coherence in critically ill pediatric patients

Differences in physiology and pathophysiology make the treatment of developing, critically ill children particularly challenging as compared to that of adults. Significant differences in the cardiovascular system of neonates and children in size, weight, body proportions, and metabolism should be considered. Hemodynamic monitoring is crucial for early warning of pending deterioration and to guide therapy. Current monitoring is limited to the macrocirculation, but an adequately functioning macrocirculation does not guarantee a well-functioning microcirculation. Research in children revealed loss of hemodynamic coherence, i.e., microcirculatory alterations despite normal systemic hemodynamics. Implementing the framework of hemodynamic coherence in microcirculatory monitoring in children can aid physicians in titrating therapy on both macrocirculatory and microcirculatory effects to assure optimal oxygen delivery. Monitoring the microcirculation at the bedside requires further technical development. Although more research is necessary to validate the concept of hemodynamic coherence in children, the possibilities of applying this concept in children seem promising.

Correlations between physiological parameters related with kidney function and minute-by-minute urine output

AIM

Recently, devices capable of measuring minute-by-minute urine output (UOm) have become available. It is not known how UOm correlates with physiological parameters in normal conditions and in disease states characterized by vascular dysfunction. This paper analyzes correlations between UOm and physiological parameters related to kidney perfusion to provide some insight about UOm pathophysiological interpretation and its relationship with renal blood flow.

METHODS

We studied 14 male pigs were anesthetized, tracheostomized, and mechanically ventilated. Mean systemic blood pressure (P_ART ), mean pulmonary artery blood pressure (P_PA ), carotid artery blood flow (Q_CA ), as well as total (Q_REN ), cortical (Q_COR ) and medullary (Q_MED ) renal blood flows, and the renal resistive index (RRI) were measured or calculated. Animals received an intravenous dose of live E. coli for the induction of sepsis (septic group), or an equivalent amount of normal saline (nonseptic group). Three groups were studied: nonseptic (n = 6) and septic (n = 4), both receiving for resuscitation NaCl 0.9% at 4 mL/kg per h; and septic (n = 4), receiving for resuscitation NaCl 0.9% at 17 mL/kg per h. Animals were monitored for 5 h after the induction of sepsis.

RESULTS

In septic animals, UOm was strongly positively correlated with Q_REN (Kendall's τ = 0.770, P < 0.05), Q_COR (τ = -0.566, P < 0.05) and Q_MED (τ = 0.632, P < 0.05); and negatively correlated with P_PA (τ = -0.524, P < 0.05) and RRI (τ = -0.672, P < 0.05). Control animals exhibited weaker correlations.

CONCLUSION

UOm is a good physiological surrogate marker of total and regional renal blood flows and vascular resistance, particularly under septic conditions, probably reflecting glomerulo-tubular dysfunction in sepsis.

A new device to automate the monitoring of critical patients' urine output

Urine output (UO) is usually measured manually each hour in acutely ill patients. This task consumes a substantial amount of time. Furthermore, in the literature there is evidence that more frequent (minute-by-minute) UO measurement could impact clinical decision making and improve patient outcomes. However, it is not feasible to manually take minute-by-minute UO measurements. A device capable of automatically monitoring UO could save precious time of the healthcare staff and improve patient outcomes through a more precise and continuous monitoring of this parameter. This paper presents a device capable of automatically monitoring UO. It provides minute by minute measures and it can generate alarms that warn of deviations from therapeutic goals. It uses a capacitive sensor for the measurement of the UO collected within a rigid container. When the container is full, it automatically empties without requiring any internal or external power supply or any intervention by the nursing staff. In vitro tests have been conducted to verify the proper operation and accuracy in the measures of the device. These tests confirm the viability of the device to automate the monitoring of UO.

On the minute by minute variations of urine output: a study in a porcine model

BACKGROUND

Urine output (UO) is usually measured hourly in acutely ill patients. Devices capable of more continuous (minute by minute urine output, UOm) measurements have become available recently. This paper aims to (1) analyze the minute by minute variations of UO, (2) analyze the impact of sepsis on those variations and (3) test if UO measured over periods shorter than 60 min provides information not available in hourly measurements.

METHODS

Fifteen male pigs were anesthetized, tracheostomized and mechanically ventilated. Sepsis was induced by the administration of live Escherichia coli. Three groups were studied: nonseptic (n = 7) and septic (n = 4), both receiving sodium chloride (NaCl) 0.9 % at 4 ml kg(-1) h(-1); and septic (n = 4) receiving NaCl 0.9 % at 17 ml kg(-1) h(-1). UOm was measured during 6 h.

RESULTS

There was a significant variation of UOm over time, as assessed by the coefficient of variation of the root-mean-squared error (CV(RMSE)), which was significantly more pronounced under conditions of sepsis than under control conditions. A UO production pattern in sepsis was identified, characterized by low UO production compared to baseline levels for approximately 30 min, followed by high UO production for approximately 30 min after initiation of the septic challenge. This pattern was noticeable if UO was measured every 10 min but not over longer periods of time.

CONCLUSIONS

UOm provides information not conveyed by hourly measurements, especially under the cardiovascular alterations associated to sepsis. This information could enable an early identification of sepsis.

Perioperative risk factors for prolonged mechanical ventilation after liver transplantation due to acute liver failure

Background

Acute liver failure (ALF) is a rapidly progressing and fatal disease for which liver transplantation (LT) is the only treatment. Posttransplant mechanical ventilation tends to be more prolonged in patients with ALF than in other LT patients. The present study examined the clinical effects of prolonged posttransplant mechanical ventilation (PMV), and identified risk factors for PMV following LT for ALF.

Methods

We reviewed data of patients undergoing LT for ALF between January 2005 and June 2011. After grouping patients according to administration of PMV (≥ 24 h), donor and recipient perioperative variables were compared between the groups with and without PMV. Potentially significant factors (P < 0.1) from the univariate intergroup comparison were entered into a multivariate logistic regression to establish a predictive model for PMV.

Results

Twenty-four (25.3%) of 95 patients with ALF who received PMV had a higher mortality rate (29.2% vs 11.3%, P = 0.038) and longer intensive care unit stay (12.9 ± 10.4 vs 7.1 ± 2.7 days, P = 0.012) than patients without PMV. The intergroup comparisons revealed worse preoperative hepatic conditions, more supportive therapy, and more intraoperative fluctuations in vital signs and less urine output in the with- compared with the without-PMV group. The multivariate analysis revealed that preoperative hepatic encephalopathy (≥ grade III), intraoperative blood pressure fluctuation, and oliguria (< 0.5 ml/kg/h) were independent risk factors for PMV.

Conclusions

PMV was associated with deleterious outcomes. Besides care for known risk factors including hepatic encephalopathy, meticulous attention to managing intraoperative hemodynamic circulatory status is required to avoid PMV and improve the posttransplant prognosis in ALF patients.

Point of care devices for assessing bleeding and coagulation in the trauma patient

Severe trauma is associated with bleeding, coagulopathy, and transfusion of blood and blood products, all contributing to higher rates of morbidity and mortality. The aim of this review is to focus on point-of-care devices to monitor coagulation in trauma. Close monitoring of bleeding and coagulation as well as platelet function in trauma patients allows goal-directed transfusion and an optimization of the patient's coagulation, reduces the exposure to blood products, reduces costs, and probably improves clinical outcome. Noninvasive hemoglobin measurements are not to be used in trauma patients due to a lack in specificity and sensitivity.

An automatic critical care urine meter

Nowadays patients admitted to critical care units have most of their physiological parameters measured automatically by sophisticated commercial monitoring devices. More often than not, these devices supervise whether the values of the parameters they measure lie within a pre-established range, and issue warning of deviations from this range by triggering alarms. The automation of measuring and supervising tasks not only discharges the healthcare staff of a considerable workload but also avoids human errors in these repetitive and monotonous tasks. Arguably, the most relevant physiological parameter that is still measured and supervised manually by critical care unit staff is urine output (UO). In this paper we present a patent-pending device that provides continuous and accurate measurements of patient's UO. The device uses capacitive sensors to take continuous measurements of the height of the column of liquid accumulated in two chambers that make up a plastic container. The first chamber, where the urine inputs, has a small volume. Once it has been filled it overflows into a second bigger chamber. The first chamber provides accurate UO measures of patients whose UO has to be closely supervised, while the second one avoids the need for frequent interventions by the nursing staff to empty the container.

Implementation of molecular phenotyping approaches in the personalized surgical patient journey

OBJECTIVE

The present review describes commonly employed metabolic profiling platforms and discusses the current and likely future application of these technologies in surgery.

BACKGROUND

The metabolic adaptations that occur in response to surgical illness and trauma are incompletely understood. Evaluating these will be critical to the development of personalized surgical health solutions. Metabonomics is an advancing field in systems biology, which provides a means of interrogating these metabolic shifts.

METHODS

Recent literature regarding metabolic profiling technologies and their applications in surgical practice are discussed. Future strategies are proposed for the incorporation of these and next-generation technologies in the evaluation of all steps in the patient surgical pathway.

RESULTS

Metabolite-based profiling has provided valuable insights into the metabolic irregularities that occur in cancer development and progression across a variety of cancer subclasses including colorectal, breast, prostate, and lung cancers. In addition, metabolic modeling has shown considerable promise in other surgical conditions including trauma and sepsis and in the assessment of pharmacotherapeutic efficacy.

DISCUSSION

Metabonomics offers a posttranscriptional view of system activity providing functional information downstream of the genome and proteome. Information at this level will provide the surgeon with a novel means of evaluating major socioeconomic problems such as cancer and sepsis. In addition, the rapid nature of emerging next generation profiling platforms provides a viable means of "real-time" perioperative metabolic assessment and optimization.

The current status of continuous noninvasive measurement of total, carboxy, and methemoglobin concentration

Intraoperative early detection of anemia, identifying toxic levels of carboxyhemoglobin after carbon monoxide exposure and titrating drug dosage to prevent toxic levels of methemoglobin are important goals. The pulse oximeter works by illuminating light into the tissue and sensing the amount of light absorbed. The same methodology is used by laboratory hemoglobinometers to measure hemoglobin concentration. Because both devices work in the same way, efforts were made to modify the pulse oximeter to also measure hemoglobin concentration. Currently there are 2 commercial pulse oximeters (Masimo Rainbow SET and OrSense NBM-200MP) that measure total hemoglobin concentration and one (Masimo) that also measures methemoglobin and carboxyhemoglobin. In this review, we describe the peer-reviewed literature addressing the accuracy of these monitors.