Effects of perfusion pressure on tissue perfusion in septic shock

Linear Correlation Between Mean Arterial Pressure and Urine Output in Critically Ill Patients

OBJECTIVE

Mean arterial pressure (MAP) plays a significant role in regulating tissue perfusion and urine output (UO). The optimal MAP target in critically ill patients remains a subject of debate. We aimed to explore the relationship between MAP and UO.

DESIGN

A retrospective observational study.

SETTING

A general ICU in a tertiary medical center.

PATIENTS

All critically ill patients admitted to the ICU for more than 10 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

MAP values and hourly UO were collected in 5,207 patients. MAP levels were categorized into 10 groups of 5 mm Hg (from MAP < 60 mm Hg to MAP > 100 mg Hg), and 656,423 coupled hourly mean MAP and UO measurements were analyzed. Additionally, we compared the UO of individual patients in each MAP group with or without norepinephrine (NE) support or diuretics, as well as in patients with acute kidney injury (AKI).Hourly UO rose incrementally between MAP values of 65-100 mm Hg. Among 2,226 patients treated with NE infusion, mean UO was significantly lower in the MAP less than 60 mm Hg group (53.4 mL/hr; 95% CI, 49.3-57.5) compared with all other groups (p < 0.001), but no differences were found between groups of 75 less than or equal to MAP. Among 2500 patients with AKI, there was a linear increase in average UO from the MAP less than 60 mm Hg group (57.1 mL/hr; 95% CI, 54.2-60.0) to the group with MAP greater than or equal to 100 mm Hg (89.4 mL/hr; 95% CI, 85.7-93.1). When MAP was greater than or equal to 65 mm Hg, we observed a statistically significant trend of increased UO in periods without NE infusion.

CONCLUSIONS

Our analysis revealed a linear correlation between MAP and UO within the range of 65-100 mm Hg, also observed in the subgroup of patients treated with NE or diuretics and in those with AKI. These findings highlight the importance of tissue perfusion to the maintenance of diuresis and achieving adequate fluid balance in critically ill patients.

Impact of Norepinephrine and Dopamine Infusion on Renal Arterial Resistive Index during Pre-Emptive Living Donor Kidney Transplantation: Propensity Score Matching Analysis

Background: Living donor kidney transplantation (LDKT) is a crucial treatment for end-stage renal disease, with pre-emptive LDKT (transplantation before dialysis initiation) offering significant benefits in graft function and patient survival. The selection of a vasopressor during LDKT, particularly between norepinephrine and dopamine, and its impact on renal arterial hemodynamics measured using the renal arterial resistive index (RARI) is poorly understood. Methods: This retrospective observational cohort study enrolled 347 eligible pre-emptive LDKT recipients from the Seoul St. Mary's Hospital between January 2019 and June 2023. Utilizing propensity score matching (PSM), the patients were categorized into dopamine and norepinephrine groups to compare the effects of these vasopressors on the intraoperative RARI, postoperative estimated glomerular filtration rate (eGFR), and hourly urine output. The RARI was measured via the Doppler ultrasonography of the renal hilum and parenchyma post-graft vascular and ureteral anastomoses. Results: The preoperative differences in the recipients' and donors' characteristics were mitigated following PSM. The dopamine group exhibited higher intraoperative RARI values at the renal hilum (0.77 ± 0.11 vs. 0.66 ± 0.13, p < 0.001) and parenchyma (0.71 ± 0.1 vs. 0.6 ± 0.1, p < 0.001) compared to those of the norepinephrine group. However, these differences were not statistically significant on postoperative day 7. The norepinephrine infusion adjusted for the propensity scores was associated with significantly lower odds of an RARI > 0.8 (hilum: OR = 0.214, 95% CI = 0.12-0.382, p < 0.001; parenchyma: OR = 0.1, 95% CI = 0.029-0.348, p < 0.001). The early postoperative outcomes showed a higher eGFR (day 1: 30.0 ± 13.3 vs. 25.1 ± 17.4 mL/min/1.73 m2, p = 0.004) and hourly urine output (day 1: 41.8 ± 16.9 vs. 36.5 ± 14.4 mL/kg/h, p = 0.002) in the norepinephrine group. Furthermore, the long-term outcomes were comparable between the groups. Conclusions: Norepinephrine infusion during pre-emptive LDKT is associated with more favorable intraoperative renal arterial hemodynamics, as evidenced by a lower RARI and improved early postoperative renal function compared to those of dopamine. These findings suggest a potential preferential role for norepinephrine in optimizing perioperative management and early graft functions in LDKT recipients. Given the retrospective nature of this study, further prospective studies are needed to confirm these observations. Additionally, the study limitations include the potential for unmeasured confounding factors and the inability to determine causality due to its observational design.

Parsimonious Waveform-derived Features consisting of Pulse Arrival Time and Heart Rate Variability Predicts the Onset of Septic Shock

Sepsis is a major public health emergency and one of the leading causes of morbidity and mortality in critically ill patients. For each hour treatment is delayed, shock-related mortality increases, so early diagnosis and intervention is of utmost importance. However, earlier recognition of shock requires active monitoring, which may be delayed due to subclinical manifestations of the disease at the early phase of onset. Machine learning systems can increase timely detection of shock onset by exploiting complex interactions among continuous physiological waveforms. We use a dataset consisting of high-resolution physiological waveforms from intensive care unit (ICU) of a tertiary hospital system. We investigate the use of mean arterial blood pressure (MAP), pulse arrival time (PAT), heart rate variability (HRV), and heart rate (HR) for the early prediction of shock onset. Using only five minutes of the aforementioned vital signals from 239 ICU patients, our developed models can accurately predict septic shock onset 6 to 36 hours prior to clinical recognition with area under the receiver operating characteristic (AUROC) of 0.84 and 0.8 respectively. This work lays foundations for a robust, efficient, accurate and early prediction of septic shock onset which may help clinicians in their decision-making processes. This study introduces machine learning models that provide fast and accurate predictions of septic shock onset times up to 36 hours in advance. BP, PAT and HR dynamics can independently predict septic shock onset with a look-back period of only 5 mins.

Determinants of acute kidney injury during high-power mechanical ventilation: secondary analysis from experimental data

BACKGROUND

The individual components of mechanical ventilation may have distinct effects on kidney perfusion and on the risk of developing acute kidney injury; we aimed to explore ventilatory predictors of acute kidney failure and the hemodynamic changes consequent to experimental high-power mechanical ventilation.

METHODS

Secondary analysis of two animal studies focused on the outcomes of different mechanical power settings, including 78 pigs mechanically ventilated with high mechanical power for 48 h. The animals were categorized in four groups in accordance with the RIFLE criteria for acute kidney injury (AKI), using the end-experimental creatinine: (1) NO AKI: no increase in creatinine; (2) RIFLE 1-Risk: increase of creatinine of > 50%; (3) RIFLE 2-Injury: two-fold increase of creatinine; (4) RIFLE 3-Failure: three-fold increase of creatinine; RESULTS: The main ventilatory parameter associated with AKI was the positive end-expiratory pressure (PEEP) component of mechanical power. At 30 min from the initiation of high mechanical power ventilation, the heart rate and the pulmonary artery pressure progressively increased from group NO AKI to group RIFLE 3. At 48 h, the hemodynamic variables associated with AKI were the heart rate, cardiac output, mean perfusion pressure (the difference between mean arterial and central venous pressures) and central venous pressure. Linear regression and receiving operator characteristic analyses showed that PEEP-induced changes in mean perfusion pressure (mainly due to an increase in CVP) had the strongest association with AKI.

CONCLUSIONS

In an experimental setting of ventilation with high mechanical power, higher PEEP had the strongest association with AKI. The most likely physiological determinant of AKI was an increase of pleural pressure and CVP with reduced mean perfusion pressure. These changes resulted from PEEP per se and from increase in fluid administration to compensate for hemodynamic impairment consequent to high PEEP.

Methylene Blue Reduces Mortality in Critically Ill and Perioperative Patients: A Meta-Analysis of Randomized Trials

Vasodilatory hypotension is common in critically ill and perioperative patients, and is associated with adverse outcomes. As a nitric oxide production inhibitor, methylene blue (MB) exerts its vasoconstrictor property and is an adjuvant for catecholamine-refractory vasodilatory shock. However, the effects of MB on clinically relevant outcomes remain unclear. Therefore, the authors performed a meta-analysis of randomized trials on MB in critically ill and perioperative patients. The authors searched through databases for randomized trials on MB in critically ill and perioperative patients, which yielded 11 studies consisting of 556 patients. The primary outcome was mortality at the longest follow-up. Secondary outcomes included hemodynamic parameters and organ dysfunction (PROSPERO: CRD42023409243). Nine out of the 11 included randomized trials reported mortality, which was significantly lower in the MB group (risk ratio, 0.60 [95% CI 0.43-0.84] p = 0.003), with findings confirmed in septic shock and cardiac surgery subgroups. The authors found reduced lengths of stay in the intensive care unit (mean difference [MD], -0.9 days [95% CI -1.06 to -0.77] p < 0.001) and in the hospital (MD, -2.2 days [95% CI, -2.68 to -1.70] p < 0.001) in the MB group. MB was associated with increased mean arterial pressure (MD, 8.4 mmHg [95% CI 5.01-11.75] p < 0.001) and systemic vascular resistance (MD, 94.5 dyn/s/cm5 [95% CI 17.73-171.15] p = 0.02), with no difference in cardiac output (standardized MD, 0.16 [95% CI, -0.25 to 0.57] p = 0.45). This meta-analysis showed that MB reverses vasodilation in critically ill and perioperative patients and might improve survival. Further adequately powered randomized trials are needed to confirm these findings.

The effect of higher or lower mean arterial pressure on kidney function after cardiac arrest: a post hoc analysis of the COMACARE and NEUROPROTECT trials

BACKGROUND

We aimed to study the incidence of acute kidney injury (AKI) in out-of-hospital cardiac arrest (OHCA) patients treated according to low-normal or high-normal mean arterial pressure (MAP) targets.

METHODS

A post hoc analysis of the COMACARE (NCT02698917) and Neuroprotect (NCT02541591) trials that randomized patients to lower or higher targets for the first 36 h of intensive care. Kidney function was defined using the Kidney Disease Improving Global Outcome (KDIGO) classification. We used Cox regression analysis to identify factors associated with AKI after OHCA.

RESULTS

A total of 227 patients were included: 115 in the high-normal MAP group and 112 in the low-normal MAP group. Eighty-six (38%) patients developed AKI during the first five days; 40 in the high-normal MAP group and 46 in the low-normal MAP group (p = 0.51). The median creatinine and daily urine output were 85 μmol/l and 1730 mL/day in the high-normal MAP group and 87 μmol/l and 1560 mL/day in the low-normal MAP group. In a Cox regression model, independent AKI predictors were no bystander cardiopulmonary resuscitation (p < 0.01), non-shockable rhythm (p < 0.01), chronic hypertension (p = 0.03), and time to the return of spontaneous circulation (p < 0.01), whereas MAP target was not an independent predictor (p = 0.29).

CONCLUSION

Any AKI occurred in four out of ten OHCA patients. We found no difference in the incidence of AKI between the patients treated with lower and those treated with higher MAP after CA. Higher age, non-shockable initial rhythm, and longer time to ROSC were associated with shorter time to AKI.

CLINICAL TRIAL REGISTRATION

COMACARE (NCT02698917), NEUROPROTECT (NCT02541591).

Effects of Postoperative Blood Pressure Management on Delirium Among Patients in the Intensive Care Unit After Cardiac Surgery: An Observational Cohort Study

OBJECTIVES

This study aimed to determine whether blood pressure control in the early postoperative period was associated with postoperative delirium in the cardiovascular intensive care unit (ICU).

DESIGN

Observational cohort study.

SETTING

Single large academic institution with a high volume of cardiac surgery.

PARTICIPANTS

Cardiac surgery patients admitted to the cardiovascular ICU after surgery.

INTERVENTIONS

Observational study.

MEASUREMENTS AND MAIN RESULTS

A total of 517 cardiac surgery patients had mean arterial pressure (MAP) data recorded minute-by-minute for 12 postoperative hours. The time spent in each of the 7 prespecified blood pressure bands was calculated, and the development of delirium was recorded in the ICU. A multivariate Cox regression model was developed using the least absolute shrinkage and selection operator approach to identify associations between time spent in each MAP range band and delirium. Compared with the reference band of 60-to-69 mmHg, longer durations spent in 3 bands were independently associated with a lower risk of delirium: 50-to-59 mmHg band (adjusted hazard ratio [HR] 0.907 [per 10 minutes]; 95% CI 0.861-0.955); 70-to-79 mmHg band (adjusted HR 0.923 [per 10 minutes]; 95% CI 0.902-0.944); 90-to-99 mmHg band (adjusted HR 0.898 [per 10 minutes]; 95% CI 0.853-0.945).

CONCLUSIONS

The MAP range bands above and below the authors' reference band of 60-to- 69 mmHg were associated with decreased risk of ICU delirium development; however, this was difficult to reconcile with a plausible biologic mechanism. Therefore, the authors did not find a correlation between early postoperative MAP control and increased risk of the development of ICU delirium after cardiac surgery.

Correlation Between Mean Arterial Pressure and Capillary Refill Time in Patients with Septic Shock: A Systematic Review and Meta-analysis

Background: The initial hemodynamic goal during septic shock resuscitation is to achieve a mean arterial pressure (MAP) above 65 mm Hg, although this does not assure a normal tissue perfusion. Capillary refill time (CRT), a marker of skin blood flow, has been validated as a marker of the reperfusion process. The aim of the study was to explore the relationship between MAP and CRT in patients in septic shock. Methods: We systematically reviewed studies which reported CRT and MAP in septic shock patients. Authors of eligible studies were asked to provide necessary data for performing a meta-correlation of Spearman's rank correlation coefficients. Subgroup analyses were performed, including studies of good quality and studies with higher/lower norepinephrine doses. Results: We identified 10 studies, comprising 917 patients. There were 5 studies considered to be of good quality. A meta-correlation showed a statistically significant but poor negative correlation between MAP and CRT (R = -0.158, range -0.221 to -0.093, P < .001, I2 = 0.0%). Subgroup analysis of best-quality studies gave similar results (R = -0.201, range -0.282 to -0.116, P < .001, I2 = 0.0%). In subanalysis concerning norepinephrine doses, no significant correlations were found. Conclusions: In patients with septic shock, there is poor inverse correlation between MAP and CRT. MAP > 65 mm Hg does not guarantee normalization of CRT.Registration code: PROSPERO: CRD42022355996. Registered on 5 September 2022.

Author Reply: Comparison of Norepinephrine and Terlipressin vs Norepinephrine Alone for Management of Septic Shock: A Randomized Control Study

How to cite this article: Sahoo P, Kothari N, Sharma A, Goyal S. Author Reply: Comparison of Norepinephrine and Terlipressin vs Norepinephrine Alone for Management of Septic Shock: A Randomized Control Study. Indian J Crit Care Med 2023;27(8):603-604.

The Eight Unanswered and Answered Questions about the Use of Vasopressors in Septic Shock

Septic shock is mainly characterized-in addition to hypovolemia-by vasoplegia as a consequence of a release of inflammatory mediators. Systemic vasodilatation due to depressed vascular tone results in arterial hypotension, which induces or worsens organ hypoperfusion. Accordingly, vasopressor therapy is mandatory to correct hypotension and to reverse organ perfusion due to hypotension. Currently, two vasopressors are recommended to be used, norepinephrine and vasopressin. Norepinephrine, an α₁-agonist agent, is the first-line vasopressor. Vasopressin is suggested to be added to norepinephrine in cases of inadequate mean arterial pressure instead of escalating the doses of norepinephrine. However, some questions about the bedside use of these vasopressors remain. Some of these questions have been well answered, some of them not clearly addressed, and some others not yet answered. Regarding norepinephrine, we firstly reviewed the arguments in favor of the choice of norepinephrine as a first-line vasopressor. Secondly, we detailed the arguments found in the recent literature in favor of an early introduction of norepinephrine. Thirdly, we reviewed the literature referring to the issue of titrating the doses of norepinephrine using an individualized resuscitation target, and finally, we addressed the issue of escalation of doses in case of refractory shock, a remaining unanswered question. For vasopressin, we reviewed the rationale for adding vasopressin to norepinephrine. Then, we discussed the optimal time for vasopressin administration. Subsequently, we addressed the issue of the optimal vasopressin dose, and finally we discussed the best strategy to wean these two vasopressors when combined.

Tissue oxygen saturation is predictive of lactate clearance in patients with circulatory shock

BACKGROUND

Tissue oxygen saturation (StO₂) decrease could appear earlier than lactate alteration. However, the correlation between StO₂ and lactate clearance was unknown.

METHODS

This was a prospective observational study. All consecutive patients with circulatory shock and lactate over 3 mmol/L were included. Based on the rule of nines, a BSA (body surface area) weighted StO₂ was calculated from four sites of StO₂ (masseter, deltoid, thenar and knee). The formulation was as follows: masseter StO₂ × 9% + (deltoid StO₂ + thenar StO₂) × (18% + 27%)/ 2 + knee StO₂ × 46%. Vital signs, blood lactate, arterial and central venous blood gas were measured simultaneously within 48 h of ICU admission. The predictive value of BSA-weighted StO₂ on 6-hour lactate clearance > 10% since StO₂ initially monitored was assessed.

RESULTS

A total of 34 patients were included, of whom 19 (55.9%) had a lactate clearance higher than 10%. The mean SOFA score was lower in cLac ≥ 10% group compared with cLac < 10% group (11 ± 3 vs. 15 ± 4, p = 0.007). Other baseline characteristics were comparable between groups. Compared to non-clearance group, StO₂ in deltoid, thenar and knee were significantly higher in clearance group. The area under the receiver operating curves (AUROC) of BSA-weighted StO₂ for prediction of lactate clearance (0.92, 95% CI [Confidence Interval] 0.82-1.00) was significantly higher than StO₂ of masseter (0.65, 95% CI 0.45-0.84; p < 0.01), deltoid (0.77, 95% CI 0.60-0.94; p = 0.04), thenar (0.72, 95% CI 0.55-0.90; p = 0.01), and similar to knee (0.87, 0.73-1.00; p = 0.40), mean StO₂ (0.85, 0.73-0.98; p = 0.09). Additionally, BSA-weighted StO₂ model had continuous net reclassification improvement (NRI) over the knee StO₂ and mean StO₂ model (continuous NRI 48.1% and 90.2%, respectively). The AUROC of BSA-weighted StO₂ was 0.91(95% CI 0.75-1.0) adjusted by mean arterial pressure and norepinephrine dose.

CONCLUSIONS

Our results suggested that BSA-weighted StO₂ was a strong predictor of 6-hour lactate clearance in patients with shock.

Association of systolic, diastolic, mean, and pulse pressure with morbidity and mortality in septic ICU patients: a nationwide observational study

BACKGROUND

Intensivists target different blood pressure component values to manage intensive care unit (ICU) patients with sepsis. We aimed to evaluate the relationship between individual blood pressure components and organ dysfunction in critically ill septic patients.

METHODS

In this retrospective observational study, we evaluated 77,328 septic patients in 364 ICUs in the eICU Research Institute database. Primary exposure was the lowest cumulative value of each component; mean, systolic, diastolic, and pulse pressure, sustained for at least 120 min during ICU stay. Primary outcome was ICU mortality and secondary outcomes were composite outcomes of acute kidney injury or death and myocardial injury or death during ICU stay. Multivariable logistic regression spline and threshold regression adjusting for potential confounders were conducted to evaluate associations between exposures and outcomes. Sensitivity analysis was conducted in 4211 patients with septic shock.

RESULTS

Lower values of all blood pressures components were associated with a higher risk of ICU mortality. Estimated change-points for the risk of ICU mortality were 69 mmHg for mean, 100 mmHg for systolic, 60 mmHg for diastolic, and 57 mmHg for pulse pressure. The strength of association between blood pressure components and ICU mortality as determined by slopes of threshold regression were mean (- 0.13), systolic (- 0.11), diastolic (- 0.09), and pulse pressure (- 0.05). Equivalent non-linear associations between blood pressure components and ICU mortality were confirmed in septic shock patients. We observed a similar relationship between blood pressure components and secondary outcomes.

CONCLUSION

Blood pressure component association with ICU mortality is the strongest for mean followed by systolic, diastolic, and weakest for pulse pressure. Critical care teams should continue to follow MAP-based resuscitation, though exploratory analysis focusing on blood pressure components in different sepsis phenotypes in critically ill ICU patients is needed.

Mean Arterial Pressure Targets and Patient-Important Outcomes in Critically Ill Adults: A Systematic Review and Meta-Analysis of Randomized Trials

OBJECTIVE

To conduct a systematic review and meta-analysis to determine whether targeting a higher mean arterial pressure (MAP) compared with a lower MAP in adults with shock results in differences in patient important outcomes.

DATA SOURCES

We searched MEDLINE, EMBASE, the Cochrane Library, and ClinicalTrials.gov through May 2021.

STUDY SELECTION

Titles and abstracts were screened independently and in duplicate to identify potentially eligible studies, then full text for final eligibility. We included parallel-group randomized controlled trials in adult patients with a diagnosis of shock requiring vasoactive medications. The higher MAP group was required to receive vasoactive medications to target a higher MAP as established by study authors, whereas the lower MAP group received vasoactive medications to target lower MAP.

DATA EXTRACTION

In triplicate, reviewers independently extracted data using a prepiloted abstraction form. Statistical analyses were conducted using the RevMan software Version 5.3.

DATA SYNTHESIS

Six randomized controlled trials (n = 3,690) met eligibility criteria. Targeting a higher MAP (75-85 mm Hg) compared with lower MAP of 65 mm Hg resulted in no difference in mortality (relative risk [RR], 1.06; 95% CI, 0.98-1.15; I2 = 0%; p = 0.12; moderate certainty. Targeting a higher MAP resulted in no difference in the risk of undergoing renal replacement therapy (RR, 0.96; 95% CI, 0.83-1.11; I2 = 24%; p = 0.57; moderate certainty); however, a subgroup analysis comparing patients with and without chronic hypertension demonstrated that a higher MAP may reduce the risk of undergoing renal replacement therapy (RR, 0.83; 95% CI, 0.71-0.98; I2 = 0%; p = 0.02).

CONCLUSIONS

In conclusion, our systematic review and meta-analysis demonstrated with moderate certainty that there is no difference in mortality when a higher MAP is targeted in critically ill adult patients with shock. Further studies are needed to determine the impact of mean arterial pressure on need for renal replacement therapy in this population.

Circulatory shock in adults in emergency department

Circulatory shock is a common condition that carries high morbidity and mortality. This review aims to update the critical steps in managing common types of shock in adult patients admitted to medical emergency and intensive care units. A literature review was performed by searching PubMed, EMBASE Ovid, and Cochrane Library, using the following search items: ("shock" OR "circulatory shock" OR "septic shock" OR "cardiogenic shock") AND ("management" OR "treatment" OR "resuscitation"). The review emphasizes prompt shock identification with tissue hypoperfusion, knowledge of the underlying pathophysiological mechanism, initial fluid resuscitation with balanced crystalloids, norepinephrine as the preferred vasopressor in septic and profound cardiogenic shock, and tailored intervention addressing specific etiologies. Point-of-care ultrasound may help evaluate an undifferentiated shock and determine fluid responsiveness. The approach to septic shock is improving; however, confirmatory studies are required for many existing (e.g., amount of initial fluids and steroids) and emerging (e.g., angiotensin II) therapies. Knowledge gaps and wide variations persist in managing cardiogenic shock that needs urgent addressing to improve outcomes.

Effects of Norepinephrine on Renal Cortical and Medullary Blood Flow in Atherosclerotic Rabbits

OBJECTIVE

The aim of this study was to explore the effect of norepinephrine (NE) on renal cortical and medullary blood flow in atherosclerotic rabbits without renal artery stenosis.

METHODS

Atherosclerosis was induced in 21 New Zealand white rabbits by feeding them a cholesterol-rich diet for 16 weeks. Thirteen healthy New Zealand white rabbits were randomly selected as controls. After atherosclerosis induction, standard ultrasonography was performed to confirm that there was no plaque or accelerated flow at the origin of the renal artery. Contrast-enhanced ultrasound (CEUS) was performed at baseline and during intravenous injection of NE. The degree of contrast enhancement of renal cortex and medulla after the injection of contrast agents was quantified by calculating the enhanced intensity.

RESULTS

The serum nitric oxide (NO) level in atherosclerotic rabbits was higher than that in healthy rabbits (299.6±152 vs. 136.5±49.5, P<0.001). The infusion of NE induced a significant increase in the systolic blood pressure (112±14 mmHg vs. 84±9 mmHg, P=0.016) and a significant decrease in the enhanced intensity in renal cortex (17.78±2.07 dB vs. 21.19±2.03 dB, P<0.001) and renal medulla (14.87±1.82 dB vs. 17.14±1.89 dB, P<0.001) during CEUS. However, the enhanced intensity in the cortex and medulla of healthy rabbits after NE infusion showed no significant difference from that at baseline.

CONCLUSION

NE may reduce renal cortical and medullary blood flow in atherosclerotic rabbits without renal artery stenosis, partly by reducing the serum NO level.

New Strategies to Optimize Hemodynamics for Sepsis-Associated Encephalopathy

Background: Sepsis-associated encephalopathy (SAE) is associated with high morbidity and mortality. Hemodynamic dysfunction plays a significant role in the incidence and mortality of SAE. Therefore, this study aimed to explore the relationship between hemodynamic indicators and SAE. Methods: 9033 patients with sepsis 3.0 were selected in a prospective study cohort. The LASSO regression model was used to select characteristic variables and remove the collinearity between them. In addition, a generalized additive model was used to find the optimal hemodynamic index value for patients with SAE. Multivariate logistic regression models, propensity matching scores, inverse probability weighting, and doubly robust estimation confirmed the reliability of the study results (i.e., the optimal hemodynamic indicators targeting patients with SAE). Results: A mean arterial pressure ≥ 65 mmHg, systolic blood pressure ≥ 90 mmHg, and lactate levels ≤ 3.5 mmol/L decrease the incidence of SAE, whereas a mean arterial pressure ≥ 59 mmHg and lactate levels ≤ 4.5 mmol/L decrease the 28-day mortality in patients with SAE. Conclusions: The hemodynamic indices of patients with SAE should be maintained at certain levels to reduce the incidence and mortality in patients with SAE, such that the mean arterial pressure is ≥65 mmHg, lactate levels are ≤3.5 mmol/L, and systolic blood pressure is ≥90 mmHg. These hemodynamic indicators should be targeted in patients with SAE.

Acute gastrointestinal failure is associated with worse hemodynamic and perfusion parameters over 48 h after admission in patients with septic shock: Retrospective cohort study

BACKGROUND

This study aimed to investigate the relationship between acute gastrointestinal injury (AGI) and hemodynamic and perfusion parameters in the first week of intensive care unit (ICU) admission and evaluate the association of AGI with ICU and hospital outcomes in patients with septic shock undergoing mechanical ventilation.

METHODS

This retrospective cohort study applied the criteria proposed by the European Society of Intensive Medicine to classify the participants into risk/dysfunction group (AGI grade I and II) and failure group (AGI grade III and IV). Hemodynamic and perfusion parameters data previously collected in the first 48 h after ICU admission (admission, 12, 24, 48 h) were analyzed.

RESULTS

A total of 163 were included and classified into AGI grades I (n = 79), II (n = 64), III (n = 20), and IV (none). Groups consisted of AGI risk/dysfunction (n = 143, 87.8%) and AGI failure (n = 20, 12.2%) patients. Patients with AGI failure had higher heart rate and mottling score (MS) at admission, lower mean arterial pressure, and an oliguria incidence at 12 h compared with those without AGI failure. Skin MS and abdominal primary site of infection were risk factors for AGI failure. AGI failure tended to be a risk factor for ICU mortality (risk ratio [95% CI]: 1.37 [0.99-1.89]; P = 0.053).

CONCLUSION

AGI was frequently observed in patients with septic shock in the first week of ICU admission. Higher heart rate and MS and lower mean arterial pressure and incidence of oliguria were identified in patients with AGI failure compared with those without. AGI failure was associated with ICU mortality.

Use of vasopressors for treatment of vasodilatory hypotension in dogs and cats by Diplomates of the American College of Veterinary Emergency and Critical Care

OBJECTIVE

To identify the most common practices of Diplomates of the American College of Veterinary Emergency and Critical Care (DACVECCs) as they relate to the recognition and treatment of hypotension in dogs and cats, particularly concerning the use of vasopressors in vasodilatory shock states.

DESIGN

A survey regarding vasopressor use was sent to all active DACVECCs using the Veterinary Information Network. Questions focused on respondent characteristics, method of recognition of hypotension, triggers for initiation of vasopressor therapy, first- and second-line vasopressor choice, and methods of determining response to therapy.

SUBJECTS

A total of 734 DACVECCs were invited to participate, and 203 Diplomates (27.7%) completed the survey.

RESULTS

For both dogs and cats, the most common first-line vasopressor was norepinephrine (87.9% in dogs and 83.1% in cats). The most common second-choice vasopressor was vasopressin (44.2% in dogs and 39.0% in cats). Cutoff values for initiating vasopressor therapy varied between species and modality used for blood pressure measurement. In general, most DACVECCs chose to initiate vasopressor therapy at a Doppler blood pressure <90 mm Hg or a mean arterial pressure of <60 or <65 mm Hg when using oscillometric or direct arterial blood pressure measurements in dogs and cats.

CONCLUSIONS

Most DACVECCs adhere to published human guidelines when choosing a first-line vasopressor. However, there is significant variability in blood pressure measurement technique, cutoffs for initiation of vasopressor use, and choice of second-line vasopressors.

Prehospital Bundle of Care Based on Antibiotic Therapy and Hemodynamic Optimization Is Associated With a 30-Day Mortality Decrease in Patients With Septic Shock

OBJECTIVES

This study aims to investigate the association between the 30-day mortality in patients with septic shock (SS) and a prehospital bundle of care completion, antibiotic therapy administration, and hemodynamic optimization defined as a fluid expansion of at least 10 mL.kg-1.hr-1.

DESIGN

To assess the association between prehospital BUndle of Care (BUC) completion and 30-day mortality, the inverse probability treatment weighting (IPTW) propensity method was performed.

SETTING

International guidelines recommend early treatment implementation in order to reduce SS mortality. More than one single treatment, a bundle of care, including antibiotic therapy and hemodynamic optimization, is more efficient.

PATIENTS

From May 2016 to March 2021, patients with SS requiring prehospital mobile ICU (mICU) intervention were retrospectively analyzed.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among the 529 patients with SS requiring action by the mICU enrolled in this study, 354 (67%) were analyzed. Presumed pulmonary, digestive, and urinary infections were the cause of the SS in 49%, 25%, and 13% of the cases, respectively. The overall 30-day mortality was 32%. Seventy-one patients (20%) received prehospital antibiotic therapy and fluid expansion. Log binomial regression weighted with IPTW resulted in a significant association between 30-day mortality and prehospital BUC completion (respiratory rate [RR] of 0.56 [0.33-0.89]; p = 0.02 and adjusted RR 0.52 [0.27-0.93]; p = 0.03).

CONCLUSIONS

A prehospital bundle of care, based on antibiotic therapy and hemodynamic optimization, is associated with a 30-day mortality decrease among patients suffering from SS cared for by an mICU.

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

Prehospital norepinephrine administration reduces 30-day mortality among septic shock patients

Background

Despite differences in time of sepsis recognition, recent studies support that early initiation of norepinephrine in patients with septic shock (SS) improves outcome without an increase in adverse effects. This study aims to investigate the relationship between 30-day mortality in patients with SS and prehospital norepinephrine infusion in order to reach a mean blood pressure (MAP) > 65 mmHg at the end of the prehospital stage.

Methods

From April 06th, 2016 to December 31th, 2020, patients with SS requiring prehospital Mobile Intensive Care Unit intervention (MICU) were retrospectively analysed. To consider cofounders, the propensity score method was used to assess the relationship between prehospital norepinephrine administration in order to reach a MAP > 65 mmHg at the end of the prehospital stage and 30-day mortality.

Results

Four hundred and seventy-eight patients were retrospectively analysed, among which 309 patients (65%) were male. The mean age was 69 ± 15 years. Pulmonary, digestive, and urinary infections were suspected among 44%, 24% and 17% patients, respectively. One third of patients (n = 143) received prehospital norepinephrine administration with a median dose of 1.0 [0.5–2.0] mg h⁻¹, among which 84 (69%) were alive and 38 (31%) were deceased on day 30 after hospital-admission. 30-day overall mortality was 30%. Cox regression analysis after the propensity score showed a significant association between prehospital norepinephrine administration and 30-day mortality, with an adjusted hazard ratio of 0.42 [0.25–0.70], p < 10^–3. Multivariate logistic regression of IPTW retrieved a significant decrease of 30-day mortality among the prehospital norepinephrine group: ORa = 0.75 [0.70–0.79], p < 10^–3.

Conclusion

In this study, we report that prehospital norepinephrine infusion in order to reach a MAP > 65 mmHg at the end of the prehospital stage is associated with a decrease in 30-day mortality in patients with SS cared for by a MICU in the prehospital setting. Further prospective studies are needed to confirm that very early norepinephrine infusion decreases septic shock mortality.

[Vasoactive drugs in the treatment of septic shock]

Septic shock is a high mortality complication frequently associated with sepsis. Early initiation of vasopressor treatment, even before completion of initial fluid resuscitation, is a determining factor in prognosis. In this sense, norepinephrine continues to be the drug of first choice, although there is increasing evidence of benefit combining it with other non-adrenergic drugs, such as vasopressin, instead of escalating norepinephrine doses. The pathophysiology of septic shock is multifactorial, and sometimes is associated with a situation of myocardial dysfunction that contributes to hemodynamic instability. It is essential to identify this situation since it worsens the prognosis and may benefit from combined treatment with inotropic drugs. There are novel vasoactive agents under study, more selective than the classic ones that in a next future could help to design more individualized and precise treatments. In the present work, the current knowledge about vasoactive drugs and their use in the management of septic shock is summarized according to the most recent scientific evidence.

Microcirculation during surgery

Throughout the long history of surgery, there has been great advancement in the hemodynamic management of surgical patients. Traditionally, hemodynamic management has focused on macrocirculatory monitoring and intervention to maintain appropriate oxygen delivery. However, even after optimization of macro-hemodynamic parameters, microcirculatory dysfunction, which is related to higher postoperative complications, occurs in some patients. Although the clinical significance of microcirculatory dysfunction has been well reported, little is known about interventions to recover microcirculation and prevent microcirculatory dysfunction. This may be at least partly caused by the fact that the feasibility of monitoring tools to evaluate microcirculation is still insufficient for use in routine clinical practice. However, considering recent advancements in these research fields, with more popular use of microcirculation monitoring and more clinical trials, clinicians may better understand and manage microcirculation in surgical patients in the future. In this review, we describe currently available methods for microcirculatory evaluation. The current knowledge on the clinical relevance of microcirculatory alterations has been summarized based on previous studies in various clinical settings. In the latter part, pharmacological and clinical interventions to improve or restore microcirculation are also presented.

Practices of Initiation of Vasoactive Drugs in Relation to Resuscitation Fluids in Children with Septic Shock: A Prospective Observational Study

Background: The role of vasoactive medications in septic shock is well-defined, but the appropriate time of initiation of these medications in reference to fluid boluses is not clear. We planned to study prospectively the practices and outcome of initiation of vasoactive infusions with respect to resuscitation fluids boluses in pediatric septic shock.

Patients and methods: Children aged 1 month to 18 years diagnosed with septic shock were enrolled to receive fluid resuscitation boluses along with vasoactive drugs. The primary outcome was to look at various practices of the initiation of vasoactive infusions; accordingly, patients were categorized into three groups: N1 received vasoactive infusions after completion of the first bolus (20 mL/kg), N2 after the second (40 mL/kg), and N3 after the third fluid (60 mL/kg) bolus. Secondary outcomes were to compare the time taken, amount of fluid required to achieve hemodynamic stability, total fluid required, and complications in the first 24 hours of treatment and mortality.

Results: Hundred children were enrolled and grouped into N1, N2, and N3 with 46, 10, and 44 patients, respectively. The volume of fluid required to achieve the resolution of shock in N1 (40 ± 10 mL/kg) was significantly less than in N2 (70 ± 10 mL/kg) and N3 (70 ± 20 mL/kg); p = 0.02. The time taken to achieve hemodynamic stability was significantly less in N1 (115 ± 45 minutes) than in N2 (196 ± 32 minutes) and N3 (212 ± 44 minutes); p = 0.02. The volume of intravenous fluid required in the first 24 hours (p = 0.02) and complications were lower in the N1 group (p = 0.04). No statistical difference in mortality was seen.

Conclusion: Early initiation of vasoactive infusions (after the first bolus) resulted in less total fluid volume, lesser time to achieve hemodynamic stability, less fluid boluses, less length of stay in the pediatric intensive care unit, and lesser complications in the first 24 hours.

Highlight: Early initiation of vasoactive infusions—after completion of the first fluid bolus resulted in less need for further fluid boluses, lesser time for shock resolution, lesser fluid overload, and less PICU stay—in pediatric septic shock.

How to cite this article: Karanvir, Gupta S, Kumar V. Practices of Initiation of Vasoactive Drugs in Relation to Resuscitation Fluids in Children with Septic Shock: A Prospective Observational Study. Indian J Crit Care Med 2021;25(8):928–933.

Heterogeneous impact of hypotension on organ perfusion and outcomes: a narrative review

Arterial blood pressure is the driving force for organ perfusion. Although hypotension is common in acute care, there is a lack of accepted criteria for its definition. Most practitioners regard hypotension as undesirable even in situations that pose no immediate threat to life, but hypotension does not always lead to unfavourable outcomes based on experience and evidence. Thus efforts are needed to better understand the causes, consequences, and treatments of hypotension. This narrative review focuses on the heterogeneous underlying pathophysiological bases of hypotension and their impact on organ perfusion and patient outcomes. We propose the iso-pressure curve with hypotension and hypertension zones as a way to visualize changes in blood pressure. We also propose a haemodynamic pyramid and a pressure-output-resistance triangle to facilitate understanding of why hypotension can have different pathophysiological mechanisms and end-organ effects. We emphasise that hypotension does not always lead to organ hypoperfusion; to the contrary, hypotension may preserve or even increase organ perfusion depending on the relative changes in perfusion pressure and regional vascular resistance and the status of blood pressure autoregulation. Evidence from RCTs does not support the notion that a higher arterial blood pressure target always leads to improved outcomes. Management of blood pressure is not about maintaining a prespecified value, but rather involves ensuring organ perfusion without undue stress on the cardiovascular system.

Liver Transplantation in Acute-on-chronic Liver Failure

Liver transplantation (LT) has revolutionized outcomes for cirrhotic patients. Current liver allocation policies dictate patients with highest short-term mortality receive the highest priority, thus, several patients become increasingly ill on the waitlist. Given cirrhosis is a progressive disease, it can be complicated by the occurrence of acute-on-chronic liver failure (ACLF), a syndrome defined by an acute deterioration of liver function associated with extrahepatic organ failures requiring intensive care support and a high short-term mortality. Successfully bridging to transplant includes accurate prognostication and prioritization of ACLF patients awaiting LT, optimizing intensive care support pre-LT, and tailoring immunosuppressive and anti-infective therapies post-LT. Furthermore, predicting futility (too sick to undergo LT) in ACLF is challenging. In this review, we summarize the role of LT in ACLF specifically highlighting (a) current prognostic scores in ACLF, (b) critical care management of the ACLF patient awaiting LT, (c) donor issues to consider in transplant in ACLF, and (d) exploring of recent post-LT outcomes in ACLF and potential opportunities to improve outcomes including current care gaps and unmet research needs.

Associations between peripheral perfusion disorders, mean arterial pressure and dose of norepinephrine administrated in the early phase of septic shock

The aim of the study was to explore the correlations between peripheral perfusion, mean arterial pressure and the dose-rate of norepinephrine (NE) infused for the treatment of septic shock. The study is retrospective analysis of data acquired prospectively on 57 patients during the first 24 hours after the occurrence of the shock. Clinical and haemodynamic characteristics, skin perfusion parameters (capillary refill time [CRT], mottling score and temperature gradients) and the dose rate of NE infusion were collected. Negative correlations between mean arterial pressure (MAP) and temperature gradients (core-to-toe: P = .03, core-to-index: P = .04) were found and abnormal CRT was associated with lower MAP (P = .02). The dose rate of NE was negatively correlated with temperature gradients (core-to-toe: P = .02, core-to-index: P = .01, forearm-to-index: P = .008) in the overall population. In patients receiving NE for at least 12 hours, the NE dose rate positively was correlated with the mottling score (P = .006), temperature gradients (core-to-toe: P = .04, forearm-to-index: P = .02, core-to-index: P = .005) and CRT (P = .001). The dose of NE administrated was associated with 14-days mortality (odds ration [OR] = 1.21 [1.06-1.38], P = .006) and with 28-days mortality (OR = 1.17 [1.01-1.36], P = 0.04). In conclusion, the study described the presence of correlations between peripheral perfusion and MAP and between peripheral perfusion and the dose rate of NE infusion.

Associations Between Mean Arterial Pressure and Poor ICU Outcomes in Critically Ill Patients With Cirrhosis: Is 65 The Sweet Spot?

OBJECTIVES

Mean arterial pressure is critically important in patients with cirrhosis in the ICU, however, there is limited data to guide therapies and targets.

DESIGN

Retrospective observational study.

SETTING

Tertiary care ICU.

PATIENTS

Two hundred and seventy-three critically ill patients with cirrhosis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We performed a comprehensive time-weighted mean arterial pressure analysis (time-weighted-average-mean arterial pressure and cumulative-time-below various mean arterial pressure-thresholds) during the first 24-hours after ICU admission (median: 25 mean arterial pressure measurements per-patient). Time-weighted-average-mean arterial pressure captures both the severity and duration of hypotension below a mean arterial pressure threshold and cumulative-time-below is the total time spent below a mean arterial pressure threshold. Individual univariable and multivariable logistic regression models were assessed for each time-weighted-average-mean arterial pressure and cumulative-time-below mean arterial pressure threshold (55, 60, 65, 70, and 75 mm Hg) for ICU-mortality. Time-weighted-average-mean arterial pressure: for 1 mm Hg decrease in mean arterial pressure below 75, 70, 65, 60, and 55 mm Hg, the odds for ICU-mortality were 14%, 18%, 26%, 41%, and 74%, respectively (p < 0.01, all thresholds). The association between time-weighted-average-mean arterial pressure and ICU-mortality for each threshold remained significant after adjusting for model for end-stage liver disease-sodium score, mechanical ventilation, vasopressor use, renal replacement therapy, grade 3/4 hepatic encephalopathy, WBC count, and albumin. Cumulative-time-below: odds for ICU-mortality were 4%, 6%, 10%, 12%, and 12% for each-hour spent below 75, 70, 65, 60, and 55 mm Hg, respectively. In the adjusted models, significant associations only remained for mean arterial pressure less than 65 mm Hg (odds ratio, 1.07; 95% CI, 1.00-1.14; p = 0.05) and < 60 mm Hg (odds ratio, 1.10; 95% CI, 1.01-1.18; p = 0.04).

CONCLUSIONS

These data suggest that maintaining a mean arterial pressure of greater than 65 mm Hg may be a reasonable target in patients with cirrhosis admitted to the ICU. However, further prospective randomized trials are needed to determine the optimal mean arterial pressure-targets in this patient population.

Vasopressor Responsiveness Beyond Arterial Pressure: A Conceptual Systematic Review Using Venous Return Physiology

ABSTRACT

We performed a systematic review to investigate the effects of vasopressor-induced hemodynamic changes in adults with shock. We applied a physiological approach using the interacting domains of intravascular volume, heart pump performance, and vascular resistance to structure the interpretation of responses to vasopressors. We hypothesized that incorporating changes in determinants of cardiac output and vascular resistance better reflect the vasopressor responsiveness beyond mean arterial pressure alone.We identified 28 studies including 678 subjects in Pubmed, EMBASE, and CENTRAL databases.All studies demonstrated significant increases in mean arterial pressure (MAP) and systemic vascular resistance during vasopressor infusion. The calculated mean systemic filling pressure analogue increased (16 ± 3.3 mmHg to 18 ± 3.4 mmHg; P = 0.02) by vasopressors with variable effects on central venous pressure and the pump efficiency of the heart leading to heterogenous changes in cardiac output. Changes in the pressure gradient for venous return and cardiac output, scaled by the change in MAP, were positively correlated (r2 = 0.88, P < 0.001). Changes in the mean systemic filling pressure analogue and heart pump efficiency were negatively correlated (r2 = 0.57, P < 0.001) while no correlation was found between changes in MAP and heart pump efficiency.We conclude that hemodynamic changes induced by vasopressor therapy are inadequately represented by the change in MAP alone despite its common use as a clinical endpoint. The more comprehensive analysis applied in this review illustrates how vasopressor administration may be optimized.

Stepwise lactate kinetics in critically ill patients: prognostic, influencing factors, and clinical phenotype

Background

To investigate the optimal target e of lactate kinetics at different time during the resuscitation, the factors that influence whether the kinetics achieve the goals, and the clinical implications of different clinical phenotypes.

Methods

Patients with hyperlactatemia between May 1, 2013 and December 31, 2018 were retrospectively analyzed. Demographic data, basic organ function, hemodynamic parameters at ICU admission (T0) and at 6 h, 12 h, 24 h, 48 h, and 72 h, arterial blood lactate and blood glucose levels, cumulative clinical treatment conditions at different time points and final patient outcomes were collected.

Results

A total of 3298 patients were enrolled, and the mortality rate was 12.2%. The cutoff values of lactate kinetics for prognosis at 6 h, 12 h, 24 h, 48 h, and 72 h were 21%, 40%, 57%, 66%, and 72%. The APACHE II score, SOFA score, heart rate (HR), and blood glucose were risk factors that correlated with whether the lactate kinetics attained the target goal. Based on the pattens of the lactate kinetics, eight clinical phenotypes were proposed. The odds ratios of death for clinical phenotypes VIII, IV, and II were 4.39, 4.2, and 5.27-fold of those of clinical phenotype I, respectively.

Conclusion

Stepwise recovery of lactate kinetics is an important resuscitation target for patients with hyperlactatemia. The APACHE II score, SOFA score, HR, and blood glucose were independent risk factors that influenced achievement of lactate kinetic targets. The cinical phenotypes of stepwise lactate kinetics are closely related to the prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01293-x.

Prehospital hemodynamic optimisation is associated with a 30-day mortality decrease in patients with septic shock

INTRODUCTION

Septic shock (SS) is characterized by low blood pressure resulting in organ failure and poor prognosis. Among SS treatments, in hospital studies reported a beneficial effect of early hemodynamic resuscitation on mortality rate. This study aims to investigate the relationship between prehospital hemodynamic optimisation and 30-day mortality in patients with SS.

METHODS

From April 6th, 2016 to December 31th, 2019, patients with SS requiring prehospital Mobile Intensive Care Unit intervention (mICU) were included. Prehospital hemodynamic optimisation was defined as a arterial blood pressure of >65 mmHg, or >75 mmHg if previous hypertension history, at the end of the prehospital stage.

RESULTS

Three hundred thirty-seven patients were retrospectively analysed. The mean age was 69 ± 15 years, and 226 patients (67%) were male. One hundred and thirty-six patients (40%) had previous hypertension history. Pulmonary, digestive and urinary infections were the suspected cause of the SS in respectively 46%, 23% and 15% of the cases. 30-day overall mortality was 30%. Prehospital hemodynamic optimisation was complete for 204 patients (61%). Cox regression analysis reports a significant association between prehospital hemodynamic optimisation and 30-day mortality (HRa = 0.52 95%CI [0.31-0.86], p = 0.01).

CONCLUSION

In this study, we report that prehospital hemodynamic optimisation is associated with a decrease in 30-day mortality in patients with SS cared for by a mICU in the prehospital setting. An individualized mean arterial pressure target, based on previous hypertension history, may be considered from the prehospital stage of SS resuscitation.

New strategies to optimize renal haemodynamics

PURPOSE OF REVIEW

This review discusses the macrocirculatory and microcirculatory aspects of renal perfusion, as well as novel methods by which to measure renal blood flow. Finally, therapeutic options are briefly discussed, including renal-specific microcirculatory effects.

RECENT FINDINGS

The optimal mean arterial pressure (MAP) needed for preservation of renal function has been debated but is most likely a MAP of 60-80 mmHg. In addition, attention should be paid to renal outflow pressure, typically central venous pressure. Heterogeneity in microcirculation can exist and may be mitigated through appropriate use of vasopressors with unique microcirculatory effects. Excessive catecholamines have been shown to be harmful and should be avoided. Both angiotensin II and vasopressin may improve glomerular flow through a number of mechanisms. Macrocirculatory and microcirculatory blood flow can be measured through a number of bedside ultrasound modalities, sublingual microscopy and urinary oxygen measurement, SUMMARY: Acute kidney injury (AKI) is a common manifestation of organ failure in shock, and avoidance of hemodynamic instability can mitigate this risk. Measurement of renal haemodynamics is not routinely performed but may help to guide therapeutic goals. A thorough understanding of pathophysiology, measurement techniques and therapeutic options may allow for a personalized approach to blood pressure management in patients with septic shock and may ultimately mitigate AKI.

Macrocirculatory and Microcirculatory Endpoints in Sepsis Resuscitation

Sepsis is a common disease process encountered by physicians. Sepsis can lead to septic shock, which carries a hospital mortality rate in excess of 40%. Although the Surviving Sepsis Guidelines recommend targeting a mean arterial pressure (MAP) of 65 mmHg and normalization of lactate, these endpoints do not necessarily result in tissue perfusion in states of shock. While MAP and lactate are commonly used markers in resuscitation, clinicians may be able to improve their resuscitation by broadening their assessment of the microcirculation, which more adequately reflects tissue perfusion. As such, in order to achieve a successful resuscitation, clinicians must optimize both macrocirculatory (MAP, cardiac output) and microcirculatory (proportion of perfused vessels, lactate, mottling, capillary refill time) endpoints. This review will summarize various macrocirculatory and microcirculatory markers of perfusion that can be used to guide the initial resuscitation of patients with sepsis.

Prevention and Therapy of AKI in Asia: A Big Challenge

Asia is the largest and most populous continent and has huge differences in socioeconomic status, development, and health care between the different countries and regions within each country. This manifests in the varied causes of acute kidney injury (AKI), particularly higher rates of community-acquired AKI and in the differential access to health care for the population. Because of resource limitations, prevention and treatment of AKI is a difficult challenge. This review highlights the differences in AKI in Asia compared with the developed world and discusses prevention and treatment of AKI within the context of resource limitations.

Infection, Sepsis and the Inflammatory Response: Mechanisms and Therapy

Sepsis secondary to bacterial infection remains a significant cause of morbidity and mortality globally. Recent decades have seen the evolution of international collaborations to improve care for these patients and identify areas for research. In this article we discuss the pathophysiology underlying the condition, review the current recommended management strategies, discuss areas of controversy, and highlight the need for ongoing research, particularly in diagnostics.

Monitoring coherence between the macro and microcirculation in septic shock

PURPOSE OF REVIEW

Currently, the treatment of patients with shock is focused on the clinical symptoms of shock. In the early phase, this is usually limited to heart rate, blood pressure, lactate levels and urine output. However, as the ultimate goal of resuscitation is the improvement in microcirculatory perfusion the question is whether these currently used signs of shock and the improvement in these signs actually correspond to the changes in the microcirculation.

RECENT FINDINGS

Recent studies have shown that during the development of shock the deterioration in the macrocirculatory parameters are followed by the deterioration of microcirculatory perfusion. However, in many cases the restoration of adequate macrocirculatory parameters is frequently not associated with improvement in microcirculatory perfusion. This relates not only to the cause of shock, where there are some differences between different forms of shock, but also to the type of treatment.

SUMMARY

The improvement in macrohemodynamics during the resuscitation is not consistently followed by subsequent changes in the microcirculation. This may result in both over-resuscitation and under-resuscitation leading to increased morbidity and mortality. In this article the principles of coherence and the monitoring of the microcirculation are reviewed.

Carotid Ultrasound to Predict Fluid Responsiveness: A Systematic Review

OBJECTIVES

To perform a systematic review of the accuracy of carotid ultrasound measures in determining volume responsiveness in adults.

METHODS

We conducted a systematic review of Ovid MEDLINE and Scopus from conception until January 1, 2019. Two independent reviewers used an iterative process to identify relevant articles and abstract information from them. The quality and risk of bias were assessed with the Quality Assessment of Diagnostic Accuracy Studies version 2 tool.

RESULTS

We identified 17 relevant articles with 956 patients. The 2 most frequently cited carotid measures of fluid responsiveness were corrected flow time and peak velocity or change in peak velocity with respiration (ΔCDPV). Accordingly, the diagnostic characteristics of corrected flow time in these studies varied widely, with sensitivities from 60% to 73%, specificities from 82% to 92%, and areas under the receiver operating characteristic curves from 0.75 to 0.88. Optimal cutoff values for ΔCDPV ranged from 9.1% to 14%, with areas under the receiver operating characteristic curves from 0.81 to 0.91, sensitivities from 73% to 86%, and specificities from 78% to 86%. Other measures, such as carotid blood flow and carotid diameter, had limited data to support their use. Heterogeneity of the studies prohibited a meta-analysis. Most studies had a moderate risk of bias and high applicability.

CONCLUSIONS

Preliminary research suggests that carotid ultrasound measures may be useful adjunct measures of fluid status; however, they should not be interpreted as absolute and should be placed in a clinical context. The most well-defined and supported measure currently is ΔCDPV, with cutoffs from 9% to 14%. Corrected flow time shows promise, because of heterogeneity of how this value is measured, an optimal cutoff has not been established.

Deletion of the adenosine A2A receptor increases the survival rate in a mice model of polymicrobial sepsis

We aim to investigate the role of A_2A receptor in peritonitis-related sepsis by injection of a fecal solution (FS) as a model of polymicrobial infection. C57/black J6 wild-type (WT) and A_2A-deficient mice (A_2AKO) were exposed to sepsis induced by intraperitoneal injection of a FS (FS-induced peritonitis) or instead was injected with saline buffer (Sham). Survival rate and sepsis score were measured up to 48 h. The presence of bacteria in tissue homogenates was analyzed. Telemetry and speckle laser Doppler were used for systemic blood pressure and peripheral blood perfusion analysis, respectively. Histological analysis and identification of active caspase 3 were performed in selected organs, including the liver. The survival rate of A_2AKO mice exposed to FS-induced peritonitis was significantly higher, and the sepsis score was lower than their respective WT counterpart. Injection of FS increases (50 to 150 folds) the number of colonies forming units in the liver, kidney, blood, and lung in WT mice, while these effects were significantly attenuated in A_2AKO mice exposed to FS-induced peritonitis. A significant reduction in both systolic and diastolic blood pressure, as well as in the peripheral perfusion was observed in WT and A_2AKO mice exposed to FS-induced peritonitis. Although, these last effects were significantly attenuated in A_2AKO mice. Histological analysis showed a large perivascular infiltration of polymorphonuclear in the liver of WT and A_2AKO mice exposed to FS-induced peritonitis, but again, this effect was attenuated in A_2AKO mice. Finally, high expression of active caspase 3 was found only in the liver of WT mice exposed to FS-induced peritonitis. The absence of the A_2A receptor increases the survival rate in mice exposed to polymicrobial sepsis. This outcome was associated with both hemodynamic compensation and enhanced anti-bacterial response.

Timing of norepinephrine initiation in patients with septic shock: a systematic review and meta-analysis

Background

The effect of the timing of norepinephrine initiation on clinical outcomes in patients with septic shock is uncertain. A systematic review and meta-analysis was performed to evaluate the impact of early and late start of norepinephrine support on clinical outcomes in patients with septic shock.

Methods

We searched the PubMed, Cochrane, and Embase databases for randomized controlled trials (RCTs) and cohort studies from inception to the 1st of March 2020. We included studies involving adult patients (> 18 years) with septic shock. All authors reported our primary outcome of short-term mortality and clearly comparing early versus late norepinephrine initiation with clinically relevant secondary outcomes (ICU length of stay, time to achieved target mean arterial pressure (≥ 65 mmHg), and volume of intravenous fluids within 6 h). Results were expressed as odds ratio (OR) and mean difference (MD) with accompanying 95% confidence interval (CI).

Results

Five studies including 929 patients were included. The primary outcome of this meta-analysis showed that the short-term mortality of the early group was lower than that of the late group (odds ratio [OR] = 0.45; 95% CI, 0.34 to 0.61; P < 0.00001; χ² = 3.74; I² = 0%). Secondary outcomes demonstrated that the time to achieved target MAP of the early group was shorter than that of the late group (mean difference = − 1.39; 95% CI, − 1.81 to − 0.96; P < 0.00001; χ² = 1.03; I² = 0%). The volume of intravenous fluids within 6 h of the early group was less than that of the late group (mean difference = − 0.50; 95% CI, − 0.68 to − 0.32; P < 0.00001; χ² = 33.76; I² = 94%). There was no statistically significant difference in the ICU length of stay between the two groups (mean difference = − 0.11; 95% CI, − 1.27 to 1.05; P = 0.86; χ² = 0.85; I² = 0%).

Conclusions

Early initiation of norepinephrine in patients with septic shock was associated with decreased short-term mortality, shorter time to achieved target MAP, and less volume of intravenous fluids within 6 h. There was no significant difference in ICU length of stay between early and late groups. Further large-scale RCTs are still required to confirm these results.

Timing of norepinephrine initiation in patients with septic shock: a systematic review and meta-analysis

BACKGROUND

The effect of the timing of norepinephrine initiation on clinical outcomes in patients with septic shock is uncertain. A systematic review and meta-analysis was performed to evaluate the impact of early and late start of norepinephrine support on clinical outcomes in patients with septic shock.

METHODS

We searched the PubMed, Cochrane, and Embase databases for randomized controlled trials (RCTs) and cohort studies from inception to the 1st of March 2020. We included studies involving adult patients (> 18 years) with septic shock. All authors reported our primary outcome of short-term mortality and clearly comparing early versus late norepinephrine initiation with clinically relevant secondary outcomes (ICU length of stay, time to achieved target mean arterial pressure (≥ 65 mmHg), and volume of intravenous fluids within 6 h). Results were expressed as odds ratio (OR) and mean difference (MD) with accompanying 95% confidence interval (CI).

RESULTS

Five studies including 929 patients were included. The primary outcome of this meta-analysis showed that the short-term mortality of the early group was lower than that of the late group (odds ratio [OR] = 0.45; 95% CI, 0.34 to 0.61; P < 0.00001; χ² = 3.74; I² = 0%). Secondary outcomes demonstrated that the time to achieved target MAP of the early group was shorter than that of the late group (mean difference = - 1.39; 95% CI, - 1.81 to - 0.96; P < 0.00001; χ² = 1.03; I² = 0%). The volume of intravenous fluids within 6 h of the early group was less than that of the late group (mean difference = - 0.50; 95% CI, - 0.68 to - 0.32; P < 0.00001; χ² = 33.76; I² = 94%). There was no statistically significant difference in the ICU length of stay between the two groups (mean difference = - 0.11; 95% CI, - 1.27 to 1.05; P = 0.86; χ² = 0.85; I² = 0%).

CONCLUSIONS

Early initiation of norepinephrine in patients with septic shock was associated with decreased short-term mortality, shorter time to achieved target MAP, and less volume of intravenous fluids within 6 h. There was no significant difference in ICU length of stay between early and late groups. Further large-scale RCTs are still required to confirm these results.

Manipulating the Microcirculation in Sepsis - the Impact of Vasoactive Medications on Microcirculatory Blood Flow: A Systematic Review

BACKGROUND

Sepsis is life-threatening organ dysfunction because of a dysregulated host response to infection. Disturbed microvascular blood flow is associated with excess mortality and is a potential future target for interventions. This review addresses the evidence for pharmacological manipulation of the microcirculation in sepsis assessed by techniques that evaluate the sublingual microvasculature.

METHODS

Systematic review using a published protocol. Eligibility criteria were studies of septic patients published from January 2000 to February 2018. Interventions were drugs aimed at improving perfusion. Outcome was improvement in microvascular flow using orthogonal polarization spectral, sidestream dark field, or incident dark field imaging (Grades of Recommendation, Assessment, Development, and Evaluation criteria used).

RESULTS

Two thousand six hundred and six articles were screened and 22 included. (6 randomized controlled trials, 12 interventional, 3 observational, and 1 pilot, n = 572 participants). Multiple measurement techniques were described, including: automated analyses, subjective, and composite scoring systems. Norepinephrine was not found to improve microvascular flow (low-grade evidence, n = 6 studies); except in chronic hypertension (low, n = 1 study). Addition of arginine vasopressin or terlipressin to norepinephrine maintained flow while decreasing norepinephrine requirements (high, n = 2 studies). Neither dobutamine nor glyceryl trinitrate consistently improved flow (low, n = 6 studies). A single study (n = 40 participants) demonstrated improved flow with levosimendan (high). In a risk of bias assessment 16/16 interventional, pilot and observational studies were found to be high risk.

CONCLUSIONS

There is no robust evidence to date that any one agent can reproducibly lead to improved microvascular flow. Furthermore, no study demonstrated outcome benefit of one therapeutic agent over another. Updated consensus guidelines could improve comparable reporting of measurements and reduce bias, to enable meaningful comparisons around the effects of individual pharmacological agents.

Vasopressors in septic shock: which, when, and how much?

In addition to fluid resuscitation, the vasopressor therapy is a fundamental treatment of septic shock-induced hypotension as it aims at correcting the vascular tone depression and then at improving organ perfusion pressure. Experts’ recommendations currently position norepinephrine (NE) as the first-line vasopressor in septic shock. Vasopressin and its analogues are only second-line vasopressors as strong recent evidence suggests no benefit of their early administration in spite of promising preliminary data. Early administration of NE may allow achieving the initial mean arterial pressure (MAP) target faster and reducing the risk of fluid overload. The diastolic arterial pressure (DAP) as a marker of vascular tone, helps identifying the patients who need NE urgently. Available data suggest a MAP of 65 mmHg as the initial target but a more individualized approach is often required depending on several factors such as history of chronic hypertension or value of central venous pressure (CVP). In cases of refractory hypotension, increasing NE up to doses ≥1 µg/kg/min could be an option. However, current experts’ guidelines suggest to combine NE with other vasopressors such as vasopressin, with the intent to rising the MAP to target or to decrease the NE dosage.

Vasopressor Therapy and Blood Pressure Management in the Setting of Acute Kidney Injury

Acute kidney injury (AKI) is common in the setting of shock. Hemodynamic instability is a risk factor for the development of AKI, and pathophysiological mechanisms include loss of renal perfusion pressure and impaired microcirculation. Although restoration of mean arterial pressure (MAP) may mitigate the risk of AKI to some extent, evidence on this is conflicting. Also debatable is the optimal blood pressure needed to minimize the risk of kidney injury. A MAP of 65 mm Hg traditionally has been considered adequate to maintain renal perfusion pressure, and studies have failed to consistently show improved outcomes at higher levels of MAP. Therapeutic options to support renal perfusion consist of catecholamines, vasopressin, and angiotensin II. Although catecholamines are the most studied, they are associated with adverse events at higher doses, including AKI. Vasopressin and angiotensin II are noncatecholamine options to support blood pressure and may improve microcirculatory hemodynamics through unique mechanisms, including differential vasoconstriction of efferent and afferent arterioles within the nephron. Future areas of study include methods by which clinicians can measure renal blood flow in a macrocirculatory and microcirculatory way, a personalized approach to blood pressure management in septic shock using patient-specific measures of perfusion adequacy, and novel agents that may improve the microcirculation within the kidneys without causing adverse microcirculatory effects in other organs.

A new photoplethysmographic device for continuous assessment of urethral mucosa perfusion: evaluation in a porcine model

This study proposes to evaluate an innovative device consisting of an indwelling urinary catheter equipped with a photoplethysmography (PPG) sensor in contact with the urethral mucosa that provides a continuous index called urethral perfusion index (uPI). The goal of this study was to determine if the uPI could bring out tissue perfusion modifications induced by hypotension and vasopressors in a porcine model. Twelve piglets were equipped for heart rate, MAP, cardiac index, stroke volume index, systemic vascular resistance index and uPI monitoring. The animals were exposed to different levels of mean arterial pressure (MAP), ranging from low to high values. Friedman tests with a posteriori multiple comparison were performed and a generalized linear mixed model (GLMM) was used to assess the relationship between uPI and MAP. Urethral Perfusion Index and other haemodynamic parameters varied significantly at the different time-points of interest. There was a positive correlation between MAP and uPI below a specific MAP value, called dissociation threshold (DT). Above this threshold, uPI and MAP were negatively correlated. This relationship, assessed with the GLMM, yielded a significant positive fixed effect coefficient (+ 0.2, P < 0.00001) below the DT and a significant negative fixed effect (- 0.14, P < 0.00001) above DT. In an experimental setting, the PPG device and its index uPI permitted the detection of urethral mucosa perfusion alterations associated with hypotension or excessive doses of vasopressors. Further studies are needed to evaluate this device in a clinical context.

Lymphatic flow modulation as adjunct therapy for septic shock

The lymphatic system is an important component of human health and is critical in maintaining microcirculatory flow and immune system homeostasis. During septic shock, increased capillary permeability results in excess filtration of intravascular fluid and solutes producing interstitial edema with subsequent hydrostatic and oncotic gradient breakdown. The accumulation of interstitial fluid results in impaired solute exchange, leukocyte signaling, and aberrancy in capillary flow. Modulation of lymphatic flow during times of interstitial volume overload such as septic shock may decrease interstitial volume resulting in improved perfusion, decreased end-organ damage, and contribute to disease resolution. Multiple studies in both humans and animals have shown nitric oxide to be a potent modulator of lymphatic function. The present study suggests a hypothetical adjunct therapy for patients with septic shock through the use of phosphodiesterase inhibitors, which may improve microcirculatory flow by decreasing interstitial fluid volume via increased lymphatic fluid drainage.

Effect of Increasing Blood Pressure With Noradrenaline on the Microcirculation of Patients With Septic Shock and Previous Arterial Hypertension

OBJECTIVES

To assess whether an increase in mean arterial pressure in patients with septic shock and previous systemic arterial hypertension changes microcirculatory and systemic hemodynamic variables compared with patients without arterial hypertension (control).

DESIGN

Prospective, nonblinded, interventional study.

SETTING

Three ICUs in two teaching hospitals.

PATIENTS

After informed consent, we included patients older than 18 years with septic shock for at least 6 hours, sedated, and under mechanical ventilation. We paired patients with and without arterial hypertension by age.

INTERVENTIONS

After obtaining systemic and microcirculation baseline hemodynamic variables (time 0), we increased noradrenaline dose to elevate mean arterial pressure up to 85-90 mm Hg before collecting a new set of measurements (time 1).

MEASUREMENTS AND MAIN RESULTS

We included 40 patients (20 in each group). There was no significant difference in age between the groups. After the rise in mean arterial pressure, there was a significant increase in cardiac index and a slight but significant reduction in lactate in both groups. We observed a significant improvement in the proportion of perfused vessels (control: 57.2 ± 14% to 66 ± 14.8%; arterial hypertension: 61.4 ± 12.3% to 70.8 ± 7.1%; groups: p = 0.29; T0 and T1: p < 0.001; group and time interaction: p = 0.85); perfused vessels density (control: 15.6 ± 4 mm/mm to 18.6 ± 4.5 mm/mm; arterial hypertension: 16.4 ± 3.5 mm/mm to 19.1 ± 3 mm/mm; groups: p = 0.51; T0 and T1: p < 0.001; group and time interaction: p = 0.70), and microcirculatory flow index (control: 2.1 ± 0.6 to 2.4 ± 0.6; arterial hypertension: 2.1 ± 0.5 to 2.6 ± 0.2; groups: p = 0.71; T0 and T1: p = 0.002; group and time interaction: p = 0.45) in both groups.

CONCLUSIONS

Increasing mean arterial pressure with noradrenaline in septic shock patients improves density and flow in small vessels of sublingual microcirculation. However, this improvement occurs both in patients with previous arterial hypertension and in those without arterial hypertension.