Hypotension and Outcomes

Kamal Maheshwari MD MPH

Associate Professor of Anesthesiology

@kamalmaheshwar7

• Why should we avoid hypotension?

- To maintain organ perfusion

- To optimize the quality of care

- To avoid complications

- To optimize cost

• How hypotension should be avoided?

- Prediction

- Appropriate diagnosis

- Appropriate treatment

Organ Perfusion

Perfusion  Flow per unit tissue weight.

Guyton and Hall

Textbook of Medical

Physiology, Chapter

14, 169-178

Guyton and Hall Textbook of Medical Physiology, Chapter

14, 169-178

Low blood pressure

Poor organ perfusion

Complications

Mortality

Quality

• "the degree to which health care services for

individuals and populations increase the

likelihood of desired health outcomes and are

consistent with current professional knowledge"

• "by empowering perioperative teams to explore

variation in practice and identify opportunities for

change"

Institute of Medicine

https://mpog.org/quality/

Leading

indicators

Lagging

indicators

Low blood

pressure

Mortality

Readmission

LOS

Hypotension as quality metric

Anesthesia & Analgesia133(2):445-454, August 2021

Hypotension as quality metric

• Metric: Number of cases in one year who qualify for

hypotension which is defined as MAP <65 mm Hg for

15 minutes per case

Complications

• 25% (around $1 trillion) of US healthcare

spending is waste

- Avoidable complications

- Unnecessary readmissions

• Postoperative complications are third

leading cause of death [global]

Shrank, JAMA,2019

Nepogodiev, Lancet, 2019

Hypotension and complications

- Operating room

- Ward

- Critical care units

Ehrenwerth J, Eisenkraft JB, Berry JM, eds. Anesthesia

Equipment: Principles and Applications. 2nd ed.

Philadelphia, PA: Elsevier Saunders; 2013:Figure 12-1

What about commonly used

oscillometric technique?

Hypotension definition

Maheshwari, A&A, 2018

Walsh, Anesthesiology, 2013

Monk, Anesthesiology 2015

Sun, Anesthesiology 2015

• Absolute MAP 65 vs. relative

20-25% MAP threshold -

similar

• Baseline pressure – no

interaction

• 90 mmHg for systolic

• 65 mmHg for mean

• 50 mmHg for diastolic

• 35 mmHg for pulse

pressure.

• One-third of all

hypotension

happened before

surgery start

Futier RCT

• Intraoperative hypotension is associated with

postoperative cardiac and renal morbidity, and

mortality.

• A universally accepted standard definition of

hypotension would facilitate further research into this

topic.

• Both hypotension

and hypertension

are common,

prolonged, and

profound in surgical

wards.

• Often missed by

routine intermittent

monitoring.

Intensive Care Med (2018) 44:857–867

https://doi.org/10.1007/s00134-018-5218-5

Organ perfusion and cardiac output

• Are we ignoring the cardiac output?

• Between CO or MAP which is more

important?

• CO = (MAP – CVP)/ SVR

Maheshwari, BJA, 2021

• The model results suggest improved intraoperative

hypotension control in a hospital (10,000 surgery) is

associated with mean cost reductions ranging from

$1.2–$4.6 million per year.

• Hospital with1,000 annual sepsis cases in the ICU would save

• $417,000 per year based on a 5-mmHg increase (95% CI:

$187,000–$696,000) and $600,000 per year for a 10-mmHg

increase (95% CI:$268,000–$1,046.000).

Key message

• Hypotension is associated with kidney injury,

myocardial injury, delirium, and mortality,

therefore should be avoided

- To maintain organ perfusion

- To avoid complications

- To optimize the quality of care

- To optimize cost

POISE Trial, Lancet 2008

Futier, JAMA 2017; INPRESS Trial

Salmasi, Anesthesiology 2017

Maheshwari, A&A, 2019

How do we prevent hypotension?

Team effort

Maheshwari et al, Anesthesia and Analgesia, 2022

Prediction

Early

diagnosis

Treatment

Input Algorithm Output

Hemodynamic

state

Suggested

Intervention

Blood pressure: the input data

Intermittent : Oscillometric

Continuous: Invasive

Non-invasive

Awadallah, JCVA, 2021

Advanced hemodynamic parameters

Venous or tissue

oximetry

Cardiac output Pre-load Afterload

SvO2 CO SVV GEDI SVR / SVRI

StO2 CI PPV CVP Eadyn

ScvO2 SV RVEDV PASP/PADP PVR/ PVRI

SVI GEDI PAOP

Contractility Lung water Blood pressure Predictive

dP/dt EVLW SBP HPI

EF EVLWI DBP AFM

Echocardiography MAP

Pressure volume graphs PP

Blood pressure measurement

Intermittent

• Valid mean arterial pressure

- Systolic and diastolic are

derived parameters

• Intermittent

• Lack advanced

hemodynamic parameters

• Lack prediction parameters

Continuous

• Continuous invasive or

noninvasive arterial pressure

monitoring can reduce

hypotension

Maheshwari, Anesthesia and Analgesia, 2018

Michard, Intensive care medicine, 2018

Naylor, Anesthesia and Analgesia 2019

Prediction

Early

diagnosis

Treatment

Input Algorithm Output

Hemodynamic

state

Suggested

Intervention

Edyn

PPV

MAP

SVR

Arterial

waveform

features

SVV

Population

data

Algorithm

Prediction

• Hypotension

• Hypovolemia

Intervention

• Fluid

• Vasopressor

• Inotrope

Clinical workflow

Davies, Anesthesia and Analgesia 2019

HPI evaluation trials

• HPI multicenter study

• SMART BP trial

Appropriate treatment

Hypotension

Fluids

SVV, PPV, CI,

Edyn, blood

loss

Vasopressors

SVR

Ionotropes

CI, SV

Balanced

anesthetic

Stable surgical

conditions

Please give fluids

Please give

vasopressor

Please give

ionotrope

AFM is Effective and Safe

• AFM recommended

and completed bolus

led to around 60%

increase in stroke

volume compared to

Vasopressor use

• Systemic vascular resistance SVR

- Difficult to measure

• Dynamic elastance Edyn

- defined as the PPV/SVV ratio, accurately predicts the

arterial pressure response after volume administration in

hypotensive, preload-dependent patients with acute

circulatory failure.

- < 0.89 will not increase MAP with volume expansion

Monge Garcia, Critical care, 2011

Inotrope use

• Cardiac contractility

- LV contractility via echocardiography

- Cardiac output trends

- dP/dt from arterial pressure waveform

• combined interaction of the LV ejection and the

arterial system properties

Monge Garcia, Critical Care, 2018

Future

• SMART BP trial

• Decision support systems

• Direct organ perfusion sensors

- Microdialysis

- CO2 sensors

Summary

• Hypotension is associated with kidney injury,

myocardial injury, delirium, mortality and should

be avoided

• Hypotension reduction strategies include

- Continuous invasive or noninvasive blood pressure

monitoring

- Hypotension prediction and appropriate

treatment algorithms