Measured Central Venous Pressure and Physician Administration of Intravenous Fluids; Methods

TODD BELOK

PI: NEAL HANDLY, MD

HAHNEMANN UNIVERSITY HOSPITAL, EMERGENCY DEPARTMENT

Hypothesis• Low (< 8mmHg) measured central venous pressure of

hypotensive non-trauma patients correlates with the decision by physicians to administer intravenous fluids.

• Do doctors treat low BP/low CVP patients with IV fluids more frequently than they treat low BP/not low CVP patients with IV fluids?

Background and Recap Central Venous Pressure = Pressure in the Superior Vena Cava/Right atrium

Alongside other point of care measurements can be used to guide hemodynamic treatment◦ Hypotension in the presence of Low CVP indicates, but does not prove that the low BP is because of low blood volume

Early goal directed resuscitation Venous compliance = Change in Volume/Change in Pressure

Background and Recap…Ohm’s Law

http://www.physicsclassroom.com/class/circuits/Lesson-3/Ohm-s-Law

Background and Recap

Neal Handly, MD, Hahnemann University Hospital, Emergency Department

Background and Recap

Neal Handly, MD, Hahnemann University Hospital, Emergency Department

Background and Recap

Neal Handly, MD, Hahnemann University Hospital, Emergency Department

Study participants, who qualifies? Adults Non-pregnant females Blind to gender No recent trauma history No inmates Implied consent; informed consent is not required

Methods Check with Charge RN/registrar to see if any non-trauma patients have been admitted

Take CVP measurement and indicate on paperwork low or not low◦ Low: CVP <8 mmHg◦ Not low: CVP ≥ 8 mmHg

CVP measurement is not shared with Hahnemann ED staff Goal of 200 patients (at least 50)

Methods

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Statistical methods 1 tailed Chi squared test 1 independent variable with two levels

◦ Independent variable: CVP in hypotensive patients◦ Two levels: low and not low

Independent variables/levels are considered dichotomous variables◦ Categorical

Dependent variables: Whether or not the physician orders IV fluids for low CVP/low BP patients and if physicians order IV fluids for not low CVP/low BP patients

Potential sources of error Low number of study participants Hemodynamic sex differences

◦ Baroreflex response to carotid HTN greater in females than males◦ Larger reduction in cardiac output

◦ Baroreflex responses to carotid hypotension is similar between the sexes

Type I (False positive) and Type II (false negative) errors◦ Differences in physician background: Are we assuming that all

physicians have the same approach to hypotension treatment◦ Differences in pathology behind hypotension in each patient

Potential sources of error continued Physicians may treat patients differently based upon suspected cause of low BP

◦ Decreased SVR vs CO

Stressed vs. unstressed venous volume

Medical News Today

Stressed vs. Unstressed Venous Volume

Venous blood volume = Stressed volume + unstressed volume

◦ Venous compliance = Change in Volume/Change in Pressure

Unstressed volume◦ Volume of blood that fills venous system without involving venous compliance or distension

Stressed volume◦ Volume of blood that involves venous compliance and distends venous blood vessels

◦ Important for establishing pressure gradient to drive venous return

Stressed vs Unstressed volume continued

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University of Alberta Critical Care Medicine Training Program

Stressed vs Unstressed volume continued

Conditions that contribute to low BP may affect stressed vs unstressed volume◦ Decreased SVR in sepsis increases venous compliance and reduces

pressure gradient that contributes to venous return

Pregnant females have different stressed and unstressed volumes because of blood flow in the uterus and fetus/placenta

Neal Handly, MD, Hahnemann University Hospital, Emergency Department

Stressed vs Unstressed volume continued

Stressed vs Unstressed volume continued

Two compartment model for venous circulation◦ Splanchnic circulation has high compliance and low flow◦ Nonsplanchnic circulation has low compliance and high flow

Regional circulation and stressed vs unstressed volume ◦ “The constriction of splanchnic veins is not associated with an increase in resistance to VR

because the splanchnic system is outside of the mainstream of blood flow to the heart through the caval veins”

Dr. Sam George, Anesthesia and Intensive Care, Guajarat Cancer and Research Institute (GCRI)

Where do we go from here? Continue to identify patients who qualify for the study

Collect data

Does Mespere’s Venus 1000 have the potential to improve patient care outcomes?◦ Setting dependent?

Thank you PI: Neal Handly, MD

Dr. Karen Hurley, PhD

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