Volume Overload: Prevalence, Risk Factors, and Functional Outcome in Survivors of Septic Shock #FOAMed

A study carried out in an academic county hospital in the US examined the associations between volume overload on ICU discharge, mobility limitation and discharge to a healthcare facility amongst survivors of septic shock.

Septic shock is commonplace in critical care and indeed, its incidence is on the increase. With this however, we are seeing a decrease in associated mortality rates as our patients survive more severe illness.

Improved recognition, protocol-based early intervention and early initial aggressive fluid resuscitation has contributed to this decline in mortality. Unsurprisingly, one of the common sequelae of such fluid resuscitation is a positive fluid balance. There is now an abundance of research suggesting an association between positive fluid balance or volume overload and mortality.

Arguably, much attention has been directed at the link between fluid balance and its impact on survival in septic shock, but consideration of the influence of fluid balance on septic shock survivors’ functional outcome has been neglected.

The authors of this study hypothesized that volume overload at ICU discharge was associated with inability to ambulate on ultimate hospital discharge and, as a corollary, discharge to a healthcare facility.

 

METHODS

Retrospective study, included 247 patients admitted with septic shock.

Inclusion criteria

• Suspected infection and ≥2 criteria for systemic inflammatory response syndrome (SIRS)
  • Body temperature >38°C or < 36°C
  • heart rate >90
  • respiratory rate >20 breaths/min or PaCO₂ <32mmHg (4.3kPa)
  • WBC >12 G/L (12000/mm³) or <4 G/L (4000/mm³) or >10% bands
• After 20ml/kg crystalloid resuscitation, patients were included if their systolic blood pressure <90mmHg, mean arterial pressure <60mmHg, or lactate >4mmol/L

 

TREATMENT

Fluid was administered during two distinct phases, then the patients were evaluated:

1. during shock
   • Any fluid given in the emergency department and ICU before shock resolution
2. after shock resolution
   1. End of 12-hour period in ICU without vasopressors and without sustained hypotension (no more than one MAP reading <60mmHg in a 12-hour period)
   2. Any fluid given from shock resolution until ICU discharge was considered as fluid administered ‘after shock resolution.’

Definition of volume overload on ICU discharge

• A fluid balance on the day of ICU discharge that would be expected to increase the patient’s body weight by 10% or more, in relation to ICU admission weight.

Mobility before hospital discharge

• Assessed using the Functional Independence Score (FIS) for ambulation
• Patients either requiring one or more people for assistance for ambulation or not able to ambulate at all, were considered unable to ambulate independently

 

RESULTS

• Mean duration of ICU stay after shock resolution was 4.1 days
• Mean duration of shock was 1.7 days
• 237 patients survived to hospital discharge
  • 90 patients (36%) had ≥1 pre-existing chronic condition [CHF, COPD, CKD, ESRD, cirrhosis]
• 247 patients admitted to ICU with septic shock survived to ICU discharge

• 213 patients (86%) had a positive fluid balance on ICU discharge
  • Median fluid balance was +5.2L (IQR, 2.1 – 10.3L)
  • 6.4% (IQR, 2.6 – 13.5%) of admission body weight

•  87 patients (35%) met criteria for volume overload on ICU discharge
  • Median fluid balance was +12.6L (IQR, 9.2 – 18.3L)
  • 16.5% (IQR, 12.5 – 22.4%) of admission body weight

• 105 patients (43.4%) were unable to ambulate on hospital discharge
  • 51 (82.3%) had been admitted from a healthcare facility
  • All patients admitted from a healthcare facility were discharged to another healthcare facility

• 54 (30%) had been admitted from home
  • 46 patients (25.6%) admitted from home were discharged to a healthcare facility

Volume overload on ICU discharge was associated with inability to ambulate independently on hospital discharge (OR, 2.29%; 95% CI, 1.24 – 4.25; P = 0.01). Independent of age, sex, APPACHE II score, duration of shock, need for vasopressors and mechanical ventilation

 

SUMMARY

From this single-centre cohort study, it is apparent that a large proportion of septic shock survivors have a positive fluid balance on ICU discharge. Also, volume overload was associated with inability to ambulate on hospital discharge. As a result, patients admitted from home, required discharge to a healthcare facility. This could have huge financial implications when you consider the increased burden placed on the healthcare system (this is the last thing we need in the UK!!).

Previous studies in patients with septic shock have shown an association between positive fluid balance or volume overload and poor outcomes (mortality, AKI). Example 1 Example 2

Although it is debatable whether volume overload is a ‘mediator or marker of illness severity’, it seems that avoiding and treating volume overload has the potential to improve mortality and morbidity outcomes in survivors of septic shock.

SO….this is why we seem pedantic on ward rounds regarding the EXACT input and output status of our patients. It is definitely one to keep drumming home to our trainees!

Written by Dr Richard Pertwee

Edited by Dr Jonny Wilkinson