Effects of Norepinephrine and Vasopressin Discontinuation Order in the Recovery Phase of Septic Shock: A Systematic Review and Individual Patient Data Meta‐Analysis

Surviving Sepsis Campaign Research Priorities 2023

OBJECTIVES

To identify research priorities in the management, epidemiology, outcome, and pathophysiology of sepsis and septic shock.

DESIGN

Shortly after publication of the most recent Surviving Sepsis Campaign Guidelines, the Surviving Sepsis Research Committee, a multiprofessional group of 16 international experts representing the European Society of Intensive Care Medicine and the Society of Critical Care Medicine, convened virtually and iteratively developed the article and recommendations, which represents an update from the 2018 Surviving Sepsis Campaign Research Priorities.

METHODS

Each task force member submitted five research questions on any sepsis-related subject. Committee members then independently ranked their top three priorities from the list generated. The highest rated clinical and basic science questions were developed into the current article.

RESULTS

A total of 81 questions were submitted. After merging similar questions, there were 34 clinical and ten basic science research questions submitted for voting. The five top clinical priorities were as follows: 1) what is the best strategy for screening and identification of patients with sepsis, and can predictive modeling assist in real-time recognition of sepsis? 2) what causes organ injury and dysfunction in sepsis, how should it be defined, and how can it be detected? 3) how should fluid resuscitation be individualized initially and beyond? 4) what is the best vasopressor approach for treating the different phases of septic shock? and 5) can a personalized/precision medicine approach identify optimal therapies to improve patient outcomes? The five top basic science priorities were as follows: 1) How can we improve animal models so that they more closely resemble sepsis in humans? 2) What outcome variables maximize correlations between human sepsis and animal models and are therefore most appropriate to use in both? 3) How does sepsis affect the brain, and how do sepsis-induced brain alterations contribute to organ dysfunction? How does sepsis affect interactions between neural, endocrine, and immune systems? 4) How does the microbiome affect sepsis pathobiology? 5) How do genetics and epigenetics influence the development of sepsis, the course of sepsis and the response to treatments for sepsis?

CONCLUSIONS

Knowledge advances in multiple clinical domains have been incorporated in progressive iterations of the Surviving Sepsis Campaign guidelines, allowing for evidence-based recommendations for short- and long-term management of sepsis. However, the strength of existing evidence is modest with significant knowledge gaps and mortality from sepsis remains high. The priorities identified represent a roadmap for research in sepsis and septic shock.

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.

Effects of Collagen Antibacterial Functional Dressing plus Continuous Nursing on Lower Extremity Skin Injury Caused by Norepinephrine in Patients with Septic Shock

Background

This study was designed to explore the effects of collagen antibacterial functional dressing plus continuous care on norepinephrine-induced lower extremity skin injury in patients with septic shock.

Methods

In this prospective, randomized, controlled study, 120 patients with septic shock receiving norepinephrine in our hospital from February 2020 to February 2021 were recruited. All the enrollments were randomized into the experimental group (n = 60) and the control group (n = 60). The control group received continuous care, while the experimental group additionally received collagen antibacterial functional dressing. Outcome measures included skin sensation scores, incidence of lower extremity skin injuries, recovery time, inflammatory factor levels, and care satisfaction.

Results

Collagen antibacterial functional dressing plus continuous care resulted in significantly lower skin sensation scores and a lower incidence of skin injuries versus continuous care alone. Patients in the experimental group had faster recovery of lower extremity skin injury than those in the control group. Collagen antibacterial functional dressing plus continuous care was associated with significantly lower levels of inflammatory factors and a higher satisfaction rate than continuous care alone.

Conclusion

Collagen antibacterial functional dressing plus continuous care improves the local skin condition of patients with septic shock receiving norepinephrine, regulates the levels of inflammatory factors, reduces the risk of skin injuries, and enhances care satisfaction.

Association Between Vasopressin Rebranding and Utilization in Patients With Septic Shock

OBJECTIVES

Vasopressin is suggested as an adjunct to norepinephrine in patients with septic shock. However, after vasopressin was rebranded in November 2014, its cost exponentially increased. Utilization patterns of vasopressin after its rebranding are unclear. The objective of this study was to determine if there is an association between the rebranding of vasopressin in November 2014 and its utilization in vasopressor-dependent patients with severe sepsis or septic shock.

DESIGN

Retrospective, multicenter, database study between January 2010 and March 2017.

SETTING

Premier Healthcare Database hospitals.

PATIENTS

Adult patients admitted to an ICU with severe sepsis or septic shock, who received at least one vasoactive agent for two or more calendar days were included.

INTERVENTIONS

The proportion of patients who received vasopressin and vasopressin cost was assessed before and after rebranding, and evaluated with segmented regression.

MEASUREMENTS AND MAIN RESULTS

Among 294,733 patients (mean age, 66 ± 15 yr), 27.8% received vasopressin, and ICU mortality was 26.5%. The proportion of patients receiving vasopressin was higher after rebranding (31.2% postrebranding vs 25.8% prerebranding). Before vasopressin rebranding, the quarterly proportion of patients who received vasopressin had an increasing slope (prerebranding slope 0.41% [95% CI, 0.35-0.46%]), with no difference in slope detected after vasopressin rebranding (postrebranding slope, 0.47% [95% CI, 0.29-0.64%]). After vasopressin rebranding, mean vasopressin cost per patient was higher ($527 ± 1,130 vs $77 ± 160), and the quarterly slope of vasopressin cost was higher (change in slope $77.18 [95% CI, $75.73-78.61]). Total vasopressin billed cost postrebranding continually increased by ~$294,276 per quarter from less than $500,000 in Q4 2014 to over $3,000,000 in Q1 2017.

CONCLUSIONS

After vasopressin rebranding, utilization continued to increase quarterly despite a significant increase in vasopressin cost. Vasopressin appeared to have price inelastic demand in septic shock.

Evaluation of Evidence, Pharmacology, and Interplay of Fluid Resuscitation and Vasoactive Therapy in Sepsis and Septic Shock

ABSTRACT

We sought to review the pharmacology of vasoactive therapy and fluid administration in sepsis and septic shock, with specific insight into the physiologic interplay of these agents. A PubMed/MEDLINE search was conducted using the following terms (vasopressor OR vasoactive OR inotrope) AND (crystalloid OR colloid OR fluid) AND (sepsis) AND (shock OR septic shock) from 1965 to October 2020. A total of 1,022 citations were reviewed with only relevant clinical data extracted. While physiologic rationale provides a hypothetical foundation for interaction between fluid and vasopressor administration, few studies have sought to evaluate the clinical impact of this synergy. Current guidelines are not in alignment with the data available, which suggests a potential benefit from low-dose fluid administration and early vasopressor exposure. Future data must account for the impact of both of these pharmacotherapies when assessing clinical outcomes and should assess personalization of therapy based on the possible interaction.

The order of vasopressor discontinuation and incidence of hypotension: a retrospective cohort analysis

The optimal order of vasopressor discontinuation during shock resolution remains unclear. We evaluated the incidence of hypotension in patients receiving concomitant vasopressin (VP) and norepinephrine (NE) based on the order of their discontinuation. In this retrospective cohort study, consecutive patients receiving concomitant VP and NE infusions for shock admitted to intensive care units were evaluated. The primary outcome was hypotension incidence following discontinuation of VP or NE (VP1 and NE1 groups, respectively). Secondary outcomes included the incidence of acute kidney injury (AKI) and arrhythmias. Subgroup analysis was conducted by examining outcomes based on the type of shock. Of the 2,035 included patients, 952 (46.8%) were VP1 and 1,083 (53.2%) were NE1. VP1 had a higher incidence of hypotension than NE1 (42.1% vs. 14.2%; P < 0.001), longer time to shock reversal (median: 2.5 vs. 2.2 days; P = .009), higher hospital [29% (278/952) vs. 24% (258/1083); P = .006], and 28-day mortality [37% (348/952) vs. 29% (317/1,083); P < 0.001] when compared with the NE1 group. There were no differences in ICU mortality, ICU and hospital length of stay, new-onset arrhythmia, or AKI incidence between the two groups. In subgroup analyses based on different types of shock, similar outcomes were observed. After adjustments, hypotension in the following 24 h and 28-day mortality were significantly higher in VP1 (Odds ratios (OR) 4.08(3.28, 5.07); p-value < .001 and 1.27(1.04, 1.55); p-value < .001, respectively). Besides, in a multivariable model, the need for renal replacement therapy (OR 1.68 (1.34, 2.12); p-value < .001) was significantly higher in VP1. Among patients with shock who received concomitant VP and NE, the VP1 group was associated with a higher incidence of hypotension in comparison with NE1. Future studies need to validate our findings and their impact on clinical outcomes.

Vasopressor-Sparing Strategies in Patients with Shock: A Scoping-Review and an Evidence-Based Strategy Proposition

Despite the abundant literature on vasopressor therapy, few studies have focused on vasopressor-sparing strategies in patients with shock. We performed a scoping-review of the published studies evaluating vasopressor-sparing strategies by analyzing the results from randomized controlled trials conducted in patients with shock, with a focus on vasopressor doses and/or duration reduction. We analyzed 143 studies, mainly performed in septic shock. Our analysis demonstrated that several pharmacological and non-pharmacological strategies are associated with a decrease in the duration of vasopressor therapy. These strategies are as follows: implementing a weaning strategy, vasopressin use, systemic glucocorticoid administration, beta-blockers, and normothermia. On the contrary, early goal directed therapies, including fluid therapy, oral vasopressors, vitamin C, and renal replacement therapy, are not associated with an increase in vasopressor-free days. Based on these results, we proposed an evidence-based vasopressor management strategy.

Hitting the Vasopressor Ceiling: Finding Norepinephrine Associated Mortality in the Critically Ill

BACKGROUND

There is no consensus on what dose of norepinephrine corresponds with futility. The purpose of this study was to investigate the maximum infusion and cumulative doses of norepinephrine associated with survival for patients in medical and surgical intensive care units (MICU and SICU).

MATERIALS AND METHODS

A retrospective review was conducted of 661 critically ill patients admitted to a large academic medical center who received norepinephrine. Univariate, multivariate, and area under the curve analyses with optimal cut offs for maximum infusion rate and cumulative dosage were determined by Youden Index.

RESULTS

The population was 54.9% male, 75.8% white, and 58.7 ± 16.1 y old with 384 (69.8%) admitted to the MICU and 166 (30.2%) admitted to the SICU, including 38 trauma patients. Inflection points in mortality were seen at 18 mcg/min and 17.6 mg. The inflection point was higher in MICU patients at 21 mcg/min and lower in SICU patients at 11 mcg/min. MICU patients also had a higher maximum cumulative dosage of 30.7 mg, compared to 2.7 mg in SICU patients. In trauma patients, norepinephrine infusions up to 5 mcg/min were associated with a 41.7% mortality rate.

CONCLUSION

A maximum rate of 18 mcg/min and cumulative dose of 17.6 mg were the inflection points for mortality risk in ICU patients, with SICU patients tolerating lower doses. In trauma patients, even low doses of norepinephrine were associated with higher mortality. These data suggest that MICU, SICU, and trauma patients differ in need for, response to, and outcome from escalating norepinephrine doses.

Analysis of Vasopressor Discontinuation and the Incidence of Rebound Hypotension in Patients With Septic Shock

Purpose: The purpose of this study was to examine the incidence of rebound hypotension in patients with septic shock requiring both norepinephrine and vasopressin infusions once discontinuation of 1 of these agents is warranted. Methods: A multicenter, retrospective study was conducted in 3 hospitals within a single health system between January 1, 2016, and December 31, 2017. The study population included adults, 18 years and older, diagnosed with septic shock and requiring concurrent infusions of norepinephrine and vasopressin. The primary outcome evaluated the incidence of rebound hypotension within 24 hours after the first vasopressor was discontinued. Secondary outcomes included intensive care unit length of stay, hospital length of stay, total vasopressor duration, and the time to rebound hypotension after first vasopressor discontinuation. Results: A total of 69 patients were included in the study, 38 in the vasopressin discontinued first group and 31 in the norepinephrine discontinued first group. Rebound hypotension occurred in 82% of patients in the vasopressin discontinued first group compared with 48% in the norepinephrine discontinued first group ( P = .004). No differences were observed in secondary outcomes, including intensive care unit or hospital length of stay, total vasopressor duration, or the time to rebound hypotension. Conclusions: Discontinuation of norepinephrine before vasopressin may lead to less incidence of rebound hypotension in patients with septic shock who require concurrent norepinephrine and vasopressin infusions. Similar to previous studies, this study found no difference in secondary outcomes.

Abrupt Discontinuation Versus Down-Titration of Vasopressin in Patients Recovering from Septic Shock

PURPOSE

To compare patient outcomes based on management of arginine vasopressin (AVP) during the recovery phase of septic shock (abrupt vs. tapering discontinuation).

PATIENTS AND METHODS

Multicenter, retrospective cohort study of patients receiving AVP with concomitant norepinephrine for septic shock. Primary outcome measure was time to intensive care unit (ICU) discharge (from decision to titrate or stop AVP). Secondary outcomes included ICU and hospital mortality, and incidence of hypotension.

RESULTS

A total of 958 (73%) abrupt discontinuation and 360 (27%) down-titration patients were included. Patient characteristics and septic shock treatment courses were similar between groups. Median time to ICU discharge was similar between abrupt discontinuation (7.9 days, 95% CI 7.2-8.7 days) and tapered patients (7.3 days, 95% CI 6.3-9.3 days, P = 0.60). After controlling for baseline discrepancies, down-titration was not an independent predictor of time to ICU discharge (HR = 0.99, 95% CI: 0.85-1.15, P = 0.91). There was no difference in ICU mortality (21.8% vs. 18.0%, P = 0.13) or hospital mortality (28.9% vs. 31.1%, P = 0.44). Although incidence of hypotension was similar (39.7% vs. 41.7%, P = 0.53), patients in the down-titration group more frequently required an escalation of AVP dose (5.7% vs. 11.1%, P < 0.001). Median AVP duration was shorter in the abrupt discontinuation group (1.4 days [IQR: 0.6-2.6 days] vs. 1.8 days [IQR: 1.1-3.2 days], P < 0.001).

CONCLUSIONS

A difference in time to ICU discharge was not detected between abrupt AVP discontinuation and down-titration in patients recovering from septic shock. In patients recovering from septic shock, abrupt discontinuation of AVP appears to be safe and may lead to shortened AVP duration.

Comparison of Hemodynamic Responses to Administration of Vasopressin and Norepinephrine Under General Anesthesia: A Systematic Review and Meta-analysis of Randomized Controlled Trials with Trial Sequential Analysis

OBJECTIVE

The authors performed a meta-analysis to determine if vasopressin improves hypotension more than norepinephrine under general anesthesia.

DESIGN

Meta-analysis.

SETTING

Operating room.

PATIENTS

Patients who underwent surgery, with general anesthesia.

INTERVENTIONS

Administration of vasopressin or norepinephrine in order to increase blood pressure.

MEASUREMENTS AND MAIN RESULTS

The primary outcome of this study was to determine if vasopressin increased mean blood pressure more effectively compared with norepinephrine for patients under general anesthesia. The secondary outcome was to see if vasopressin increased heart rate (HR), central venous pressure (CVP), cardiac output (CO), and cardiac index (CI) more significantly compared with norepinephrine under general anesthesia. The authors calculated the weighted mean difference, with 95% confidence interval (CI) using the random-effects model, and calculated the required information size (RIS) by performing trial sequential analysis (TSA). The authors selected 6 studies for analysis. Vasopressin did not improve hypotension compared with norepinephrine under general anesthesia. (weighted mean difference = -0.84 mmHg, 95% CI: -5.90 to 4.23, p = 0.75, Cochran Q = 24.6, I² = 84%) In TSA, only 35.5% of RIS was achieved. Similarly, vasopressin and norepinephrine were not significantly different in terms of HR, CVP, CO, and CI. In TSA, only 23.7% of the RIS was reached for HR but RIS was almost achieved for CVP and CO.

CONCLUSIONS

Vasopressin did not improve hypotension compared with norepinephrine under general anesthesia. The RIS was not reached in TSA, and Grading of Recommendations Assessment, Development and Evaluation is very low. Therefore, further research is needed to reach more robust conclusions.

Diabetes Insipidus After Discontinuation of Vasopressin Infusion for Treatment of Shock

OBJECTIVES

Vasopressin has achieved common usage for the treatment of catecholamine-requiring and catecholamine-resistant shock. Diabetes insipidus is a syndrome characterized by excretion of abnormally large volumes of dilute urine. To date, very few reports of diabetes insipidus after discontinuation of vasopressin infusion have been published; the majority of previous reports describe neurosurgical patients. The purpose of the present study was to investigate the occurrence rate of diabetes insipidus after discontinuation of vasopressin infusion among patients treated with vasopressin infusion for shock.

DESIGN

Retrospective analysis of electronic health records of patients receiving continuous vasopressin infusion for the treatment of shock within a 5-year period (2012-2016).

SETTING

Medical, surgical, and cardiothoracic ICUs within one academic medical center.

PATIENTS

One-thousand eight-hundred ninety-six patients received vasopressin infusion for the treatment of shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The occurrence rate of diabetes insipidus after discontinuation of vasopressin infusion was 1.53% among all patients. Sixteen of 29 patients with diabetes insipidus after discontinuation of vasopressin infusion had undergone cardiothoracic intervention, such as coronary artery bypass graft and valve replacement surgery, extracorporeal membrane oxygenation, and placement of ventricular assist devices. No neurosurgical patients were identified in our cohort. In a control group of patients receiving norepinephrine but not vasopressin infusion for treatment of shock, criteria for diabetes insipidus were observed in two of 1,320 subjects (0.15%).

CONCLUSIONS

Despite a paucity of published reports, diabetes insipidus after discontinuation of vasopressin infusion appears not to be a rare phenomenon, and is likely to be encountered by intensivists who regularly employ vasopressin for the treatment of vasoplegic shock. Previous reports consisted predominantly of neurosurgical patients. Our findings demonstrate the occurrence of diabetes insipidus after discontinuation of vasopressin infusion among patients with septic shock as well as vasoplegic shock after cardiothoracic intervention. The mechanism of diabetes insipidus after discontinuation of vasopressin infusion remains to be elucidated but may involve transient downregulation of V2 receptors induced by exposure to supraphysiological doses of vasopressin.

Narrative Review of Controversies Involving Vasopressin Use in Septic Shock and Practical Considerations

Objective: To summarize literature evaluating vasopressin use, focusing on clinical controversies regarding initiation, dosing, and discontinuation and interaction of vasopressin with other therapies in septic shock patients. Data Sources: A PubMed English-language literature search (January 2008 to December 2019) was performed using these terms: arginine vasopressin, septic, shock, and sepsis. Citations, including controlled trials, observational studies, review articles, guidelines, and consensus statements, were reviewed. Study Selection and Data Extraction: Relevant clinical data focusing on specific controversial questions regarding the utility of vasopressin in patients with septic shock were narratively summarized. Data Synthesis: Current literature does not strongly support the use of vasopressin as a first-line initial therapy for septic shock. Additionally, there are conflicting data for weight-based dosing of vasopressin in overweight patients. Evidence for vasopressin renal protection and interaction with corticosteroids is minimal. However, vasopressin has the ability to reduce catecholamine requirements in septic shock patients and may provide a mortality benefit in specific subgroups. Discontinuation of vasopressin last, not second to last, in resolving septic shock may reduce hypotension development. Relevance to Patient Care and Clinical Practice: This review addresses specific clinical controversies that drive vasopressin use in septic shock patients in real-world practice. Conclusion: Vasopressin should remain second-line adjunct to norepinephrine to augment mean arterial pressures. Dosing should be initiated at 0.03 U/min, and higher doses offer minimal benefit. There are conflicting data on the impact of weight on vasopressin response. Studies have failed to show renal benefit with vasopressin use or an interaction with corticosteroid therapy.

Mortality, Morbidity, and Costs After Implementation of a Vasopressin Guideline in Medical Intensive Care Patients With Septic Shock: An Interrupted Time Series Analysis

Background: Vasopressin decreases vasopressor requirements in patients with septic shock. However, the optimal norepinephrine dose for initiation or cessation of vasopressin is unclear. Objective: Analyze monthly intensive care unit (ICU) mortality rates 1 year preimplementation and postimplementation of a guideline suggesting a norepinephrine dose of 50 µg/min or more for initiation of vasopressin and early cessation of vasopressin. Methods: This retrospective quasi-experimental study included adult patients with septic shock admitted to the medical ICU of a tertiary care medical center over 2 years. Time periods were evaluated with interrupted time series analysis. Results: A total of 1148 patients were included: 573 patients preguideline and 575 patients postguideline. Group characteristics were well balanced at baseline, except patients postguideline had higher sequential organ failure assessment scores. Postguideline, fewer patients were initiated on vasopressin (305 [53.2%] vs 217 [37.7%], absolute difference -15.5% [95% CI -21.2% to -9.8%]), and the norepinephrine dose at vasopressin initiation was higher (median 25 [interquartile range 18, 40] µg/min vs 40 [22, 52] µg/min; median difference 15 [95% CI 11 to 19] µg/min; P < 0.01). After guideline implementation, there was no evidence for a difference in ICU mortality rate slope (slope change 0.07% [95% CI -0.8% to 1.0%] per month; P 0.87), but the vasoactive cost level decreased by US$183 (95% CI -US$327 to -US$39) per patient immediately after implementation. Conclusion and Relevance: Implementation of a guideline suggesting a high norepinephrine dose threshold for vasopressin initiation and early vasopressin cessation in patients with septic shock appears to be safe and may decrease vasoactive costs.

Norepinephrine and Vasopressin Compared With Norepinephrine and Epinephrine in Adults With Septic Shock

Background: The optimal adjuvant vasopressor to norepinephrine in septic shock remains controversial. Objective: To compare durations of shock-free survival between adjuvant vasopressin and epinephrine. Methods: A retrospective, single-center, matched cohort study of adults with septic shock refractory to norepinephrine was conducted. Patients receiving norepinephrine not at target mean arterial pressure (MAP; 65 mm Hg) were initiated on vasopressin or epinephrine to raise MAP to target. Vasopressin-exposed patients were matched to epinephrine-exposed patients using propensity scores. Mortality outcomes were examined using multivariable Poisson regression with robust variance estimation. Results: Of 166 patients, 96 (entire cohort) were included in the propensity score-matched cohort. Shock-free survival durations in the first 7 days were similar between epinephrine- and vasopressin-exposed patients in the matched cohort (median = 13.2 hours, interquartile range [IQR] = 0-121.0, vs median = 41.3 hours, IQR = 0-125.9; P = 0.51). Seven- and 28-day mortality rates were similar in the matched cohort (7-day: 47.9% vs 39.6%, P = 0.35; 28-day: 56.3% vs 58.3%, P = 0.84). Mortality rates were similar between epinephrine- and vasopressin-exposed patients in propensity score-matched regression models with and without adjustments at 7 (relative risk [RR] = 1.28, 95% CI = 0.92-1.79; RR = 1.21, 95% CI = 0.81-1.81) and 28 days (RR = 1.04, 95% CI = 0.81-1.34; RR = 0.96, 95% CI = 0.69-1.34). Conclusion and Relevance: Shock-free survival durations were similar in matched epinephrine- and vasopressin-exposed groups. Adjuvant epinephrine or vasopressin alongside norepinephrine to raise MAP to target requires further investigation.