Systemic Vascular Resistance and Pulmonary Vascular Resistance: What’s the Difference?

In a previous blog post, we discussed preload and afterload. You may recall, preload is the amount of ventricular stretch at the end of diastole. Afterload is the pressure the myocardial muscle must overcome to push blood out of the heart during systole. The left ventricle ejects blood through the aortic valve against the high pressure of the systemic circulation, also known as systemic vascular resistance (SVR).1 The right ventricle ejects blood through the pulmonic valve against the low pressure of the pulmonary circulation, or pulmonary vascular resistance (PVR).1

Let’s dig a little deeper into these concepts.


Systemic vascular resistance (SVR)*

Systemic vascular resistance (SVR) reflects changes in the arterioles2, which can affect emptying of the left ventricle. For example, if the blood vessels tighten or constrict, SVR increases, resulting in diminished ventricular compliance, reduced stroke volume and ultimately a drop in cardiac output.1 The heart must work harder against an elevated SVR to push the blood forward, increasing myocardial oxygen demand. If blood vessels dilate or relax, SVR decreases, reducing the amount of left ventricular force needed to open the aortic valve. This may result in more efficient pumping action of the left ventricle and an increased cardiac output.2 Understanding SVR will help the bedside clinician treat a patient’s hemodynamic instability. If the SVR is elevated, a vasodilator such as nitroglycerine or nitroprusside may be used to treat hypertension. Diuretics may be added if preload is high. If the SVR is diminished, a vasoconstrictor such as norepinephrine, dopamine, vasopressin or neosynephrine may be used to treat hypotension. Fluids may be administered if preload is low.

SVR is calculated by subtracting the right atrial pressure (RAP) or central venous pressure (CVP) from the mean arterial pressure (MAP), divided by the cardiac output and multiplied by 80. Normal SVR is 700 to 1,500 dynes/seconds/cm-5.

Here’s an example:
If a patient's MAP is 68 mmHg, his CVP is 12 mmHg, and his cardiac output is 4.3 L/minute, his SVR would be 1,042 dynes/sec/cm-5.
 
SVR.jpg
 
Conditions that can increase SVR include1,2:
  • Hypothermia
  • Hypovolemia
  • Cardiogenic shock
  • Stress response
  • Syndromes of low cardiac output
Conditions that can decrease SVR include1,2:
  • Anaphylactic and neurogenic shock
  • Anemia
  • Cirrhosis
  • Vasodilation


Pulmonary vascular resistance (PVR)*

Pulmonary vascular resistance (PVR) is similar to SVR except it refers to the arteries that supply blood to the lungs. If the pressure in the pulmonary vasculature is high, the right ventricle must work harder to move the blood forward past the pulmonic valve. Over time, this may cause dilation of the right ventricle, and require additional volume to meet the preload needs of the left ventricle.1
 
PVR can be calculated by subtracting the left atrial pressure from the mean pulmonary artery pressure (PAP), divided by the cardiac output (CO) and multiplied by 80. To obtain the left atrial pressure, a pulmonary artery catheter (PAC) is needed to perform a pulmonary artery occlusion pressure (PAOP), also known as pulmonary artery wedge pressure (PAWP). Normal PVR is 100 – 200 dynes/sec/cm-5.

Here’s an example:
If a patient's mean PAP is 16 mmHg, his PAOP is 6 mmHg, and his cardiac output is 4.1 L/minute, his PVR would be 195 dynes/sec/cm-5.
 
PVR.jpg
 
Factors that increase PVR include1:
  • Vasoconstricting drugs
  • Hypoxemia
  • Acidemia
  • Hypercapnia (high partial pressure of arterial carbon dioxide [PaCO2])
  • Atelectasis
 Factors that decrease PVR include1:
  • Vasodilating drugs
  • Alkalemia
  • Hypocapnia (low PaCO2)
  • Strenuous exercise
The accuracy of SVR and PVR depends on the direct pressure measurements and indirect cardiac outputs from a pulmonary artery catheter which are subject to error. However, SVR can provide critical information when differentiating various types of shock and PVR is useful when diagnosing the severity of pulmonary hypertension.3 Understanding these parameters will help the bedside clinician better manage medications and hemodynamic instability.
 
*You may also see systemic vascular resistance index (SVRI) or peripheral vascular resistance index (PVRI) reported; these measurements are calculated by substituting cardiac index (CI) for CO in the equations.

References:
1. Breitenbach, J. (2010). Putting an end to perfusion confusion. Nursing Made Incredibly Easy!. 5(3): 50 60
2. Gowda, C. (2008). Don’t be puzzled by cardiovascular concepts. Nursing Made Incredibly Easy!. 6(4): 27-30.
3. Silvestry, F. (2015). Pulmonary artery catheterization: interpretation of hemodynamic values and waveforms in adults. Uptodate. Retrieved on April, 17, 2017 from https://www.uptodate.com/contents/pulmonary-artery-catheterization-interpretation-of-hemodynamic-values-and-waveforms-in-adults
 
Myrna B. Schnur, RN, MSN 

 
Posted: 5/25/2017 10:11:09 AM by Lisa Bonsall, MSN, RN, CRNP | with 0 comments

Categories: Diseases & Conditions


Transmission-based isolation precautions for common pathogens

As a follow-up to our previous post on isolation guidelines, here is a list of transmission-based precautions recommended for common pathogens. 
 
Disease-specific-isolation-recommendations-500x750.png

Megan Doble, MSN, RN, CRNP
 
References:
Centers for Disease Control (CDC), 2016. Prevention Strategies for Seasonal Influenza in Healthcare Settings: Guidelines and Recommendations. Available at: https://www.cdc.gov/flu/professionals/infectioncontrol/healthcaresettings.htm#

Siegel, J.D., Rhinehart, E., Jackson, M., Chiarello, L., & the Healthcare Infection Control Practices Advisory Committee, (2007). Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007. Available at: http://www.cdc.gov/ncidod/dhqp/pdf/isolation2007.pdf
 

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Posted: 4/9/2017 5:43:04 AM by Lisa Bonsall, MSN, RN, CRNP | with 0 comments

Categories: Diseases & Conditions Patient Safety


GI Nurses & Associates Week 2017

GI Nurses & Associates Week is March 20-24, 2017!

We wish those of you in this specialty a wonderful week, and we thank you for compassion and dedication. Please enjoy the content below, specially selected to help you in your practice.

For those of us in other specialties, GI disorders can be challenging. Please explore, and share, the content in this collection with your colleagues!
 
Colorectal Cancer  
Inflammatory Bowel Disease  
Irritable Bowel Syndrome  
Clostridium difficile  
Pancreatitis   
Have a great week!

 
Posted: 3/20/2017 7:42:52 AM by Lisa Bonsall, MSN, RN, CRNP | with 0 comments

Categories: Diseases & Conditions


Laboratory signs of sepsis [Infographic]

Patients with sepsis can present in a variety of ways making sepsis very difficult to diagnose. Clinicians are now encouraged to use tools, such as the Sequential (Sepsis-Related) Organ Failure Assessment Score (SOFA), to assist in screening for septic patients. In addition to the parameters outlined in the SOFA score (hypoxemia, blood pressure, platelets, bilirubin, creatinine, urine output, and Glascow Coma Scale), several other laboratory values may help identify patients at high risk for organ failure and sepsis.

Use this infographic as reference guide for lab results that you may see in septic patients.

Myrna B. Schnur, RN, MSN  
Reference:
Neviere, R. (2017, February 28). Sepsis syndromes in adults: Epidemiology, definitions, clinical presentation, diagnosis, and prognosis. Retrieved from UpToDate: https://www.uptodate.com/contents/sepsis-syndromes-in-adults-epidemiology-definitions-clinical-presentation-diagnosis-and-prognosis
Laboratory-signs-of-sepsis_300x750.png

 

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Posted: 3/11/2017 5:09:52 AM by Lisa Bonsall, MSN, RN, CRNP | with 1 comments

Categories: Diseases & Conditions


World Cancer Day and How Nurses Can Help

world cancer dayFebruary 4th is World Cancer Day, and the theme for the day between 2016 and 2018 is “We can. I can.” Here, at Lippincott Nursingcenter, we know there are a number of ways nurses can help bring awareness to this day, along with ways nurses can better care for patients affected by cancer. 

1. Spread the word: Follow these hashtags on your social media accounts to join the discussion around World Cancer Day. 

  • #WorldCancerDay
  • #WeCanICan

2. Stay informed: Stay up-to-date on the latest research and evidence around cancer.  
Subscribe to the peer-reviewed journals, Cancer Nursing and Oncology Times.
.Cancer NursingOncology Times
  • Earn continuing education credits with over 160 CE activities related to oncology.
  • Access evidence-based cancer content instantly at the point of care with Lippincott Advisor. The individual version of the app used by leading hospitals includes over 1,000 evidence-based content entries on cancer symptoms, drugs, treatments, and more. Download it now for only $29.95.
3. Take action: Get certified in oncology by visiting our Guide to Certification page and scrolling down to the Oncology Nursing Certification Corporation.  
Posted: 1/31/2017 8:34:22 AM by Cara Deming | with 0 comments

Categories: Diseases & Conditions


Cardiac Output and Cardiac Index – What's the Difference?

Mastering hemodynamics can be tricky, but the first step is understanding the terminology. Let’s take a look at cardiac output and cardiac index – how to calculate them and why they’re important.

Cardiac Output (CO)

Cardiac output is the volume of blood the heart pumps per minute. Cardiac output is calculated by multiplying the stroke volume by the heart rate. Stroke volume is determined by preload, contractility, and afterload. The normal range for cardiac output is about 4 to 8 L/min, but it can vary depending on the body’s metabolic needs. Cardiac output is important because it predicts oxygen delivery to cells.
 
Here’s an example:
If a patient's stroke volume is 75 mL with each contraction and his heart rate is 60 beats/minute, his cardiac output is 4,500 mL/minute (or 4.5 L/minute).
 
Cardiac-Output.png

Cardiac Index (CI)

The cardiac index is an assessment of the cardiac output value based on the patient’s size. To find the cardiac index, divide the cardiac output by the person’s body surface area (BSA). The normal range for CI is 2.5 to 4 L/min/m2.

Here’s an example of how to calculate the cardiac index:
If a patient’s cardiac output is 4.5 L/minute and his BSA is 1.25 m2, his CI would be 3.6 L/min/m2. If another patient has a cardiac output of 4.5 L/minute, but he has a BSA of 2.5 m2, his CI would be 1.8 L/min/m2.  
 
 Cardiac-Index.png
 
Both cardiac output and cardiac index are important to let us know if a patient’s heart is pumping enough blood and delivering enough oxygen to cells. We also use CO and CI values to manage certain drug therapy, such as inotropics and vasopressors.
   
References
Gowda, C. (2008). Don't be puzzled by cardiovascular concepts. Nursing Made Incredibly Easy!, 27-30.
Smeltzer, S. B. (2010). Brunner & Suddarth's Textbook of Medical-Surgical Nursing, Twelfth Edition. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
Warise, L. (2015). Understanding Cardiogenic Shock: A Nursing Approach to Improve Outcomes. Dimensions of Critical Care Nursing, 67-77.

 
Posted: 12/13/2016 9:40:25 AM by Lisa Bonsall, MSN, RN, CRNP | with 3 comments

Categories: Diseases & Conditions


Breath sounds: Test your knowledge

Below are the results of a recent nursing quiz about lung auscultation posted on our Twitter page. This revealed a need for clarification of common adventitious lung sounds and the commonly associated clinical conditions. 
breath sounds quiz
Answer: B. Crackles are heard when collapsed or stiff alveoli snap open, as in pulmonary fibrosis. Wheezes are commonly associated with asthma and diminished breath sounds with neuromuscular disease. Breath sounds will be decreased or absent over the area of a pneumothorax.
 
First, let’s review the most common adventitious lung sounds.
A wheeze is high-pitched continuous musical sound, which may occur during inspiration and/or expiration, due to an obstructive process. The classic wheeze may be referred to as “sibilant wheeze.” This refers to the high-pitched whistle-like sound heard during expiration, typically in the setting of asthma, as air moves through a narrow or obstructed airway.
wheeze breath sound.png
 
Alternately, what we often refer to as rhonchi is the “sonorous wheeze,” which refers to a deep, low-pitched rumbling or coarse sound as air moves through tracheal-bronchial passages in the presence of mucous or respiratory secretions.
rhonchi breath sound

In stridor, you’ll hear high-pitched, monophonic inspiratory wheezing. It’s typically loudest over the anterior neck, as air moves turbulently over a partially-obstructed upper airway.
 
stridor breath sound

Crackles, or rales, are short, high pitched, discontinuous, intermittent, popping sounds created by air being forced through an airway or alveoli narrowed by fluid, pus, or mucous. These sounds may also be heard when there is delayed opening of collapsed alveoli.
 
Crackles are typically heard during inspiration and can be further defined as coarse or fine. Coarse crackles are heard during early inspiration and sound harsh or moist. They are caused by mucous in larger bronchioles, as heard in COPD. Fine crackles are heard during late inspiration and may sound like hair rubbing together. These sounds originate in the small airways/alveoli and may be heard in interstitial pneumonia or pulmonary fibrosis.
 
coarse crackles breath sound

fine crackles breath sound

Now, let’s think about test-taking strategies. In this instance, it would be helpful to go through each clinical condition separately and predict what you may hear on auscultation.
 
The first choice was asthma. Asthma is a condition mediated by inflammation. The resulting physiologic response in the airways is bronchoconstriction and airway edema. This response is triggered by an irritant, allergen, or infection. As air moves through these narrowed airways, the primary lung sound is high-pitched wheeze. Initially the wheezes are expiratory but depending on confounding factors or worsening clinical symptoms, there may be inspiratory wheezes, rhonchi or crackles. For testing purposes, however, expiratory wheezes are associated with asthma.

The second choice was pulmonary fibrosis. This is a form of interstitial lung disease in which scarring (or fibrosis) is the hallmark clinical feature. This scarring leads to thickness and stiffness in the lungs. The most common adventitious sound associated with pulmonary fibrosis is fine bibasilar crackles. This may be hard to distinguish from congestive heart failure. The crackles are the result of the snapping open of collapsed, stiff alveoli.

Neuromuscular disease was the third choice. Neuromuscular disorders can cause respiratory problems through several pathways as the muscles responsible for breathing are affected. Diaphragmatic weakness can lead to hypoventilation; chest wall muscle weakness can lead to ineffective cough; and upper airway muscle weakness can lead to difficult swallowing and ineffective clearing of upper airway secretions. In general, there are not specific adventitious sounds associated with neuromuscular disorders.

Lastly, a pneumothorax is a collapsed lung. There would be loss of breath sounds over the area of a pneumothorax as there is no air movement in the area of auscultation.

So, this leads us to the correct answer. During lung auscultation, crackles are heard in pulmonary fibrosis, which is choice B.  

Reviewing what you know and thinking about each response choice can help you focus in on the correct answer. Do you have an easy acronym or pearl for remembering breath sounds, or some test-taking strategies to share?
 
Reference:
Hinkle, J. & Cheever, K.  (2013). Brunner & Suddarth's Textbook of Medical-Surgical Nursing. Philadelphia: Lippincott Williams & Wilkins.
 
Megan Doble, MSN, RN, CRNP
 
 
 
Posted: 10/11/2016 7:54:17 AM by Lisa Bonsall, MSN, RN, CRNP | with 4 comments

Categories: Diseases & Conditions


Preventing mosquito-borne illnesses [Infographic]

With Zika virus in the news and on our minds this season, we know some of the best advice for preventing this illness is to prevent infection via mosquito bites. See the infographic below for recommendations to prevent transmission of Zika virus and other mosquito-borne illnesses.
 
preventing-mosquito-born-illnessess.png

 

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Posted: 7/29/2016 8:35:34 PM by Lisa Bonsall, MSN, RN, CRNP | with 3 comments

Categories: Diseases & Conditions


Zika Virus: 5 More Things for Nurses to Know

Aedes-aegypti-mosquito.pngIn January of 2016, we shared 5 Things Nurses Need to Know about Zika Virus. Since that time, ongoing research and monitoring has increased what we know, and recommendations have been updated based on the latest evidence. Here are five more things that are important for nurses to understand:

1. Is there a test for Zika virus?
Early in the course of Zika virus, a serum real-time reverse transcription-polymerase chain reaction (rRT-PCR) may detect Zika virus RNA in the blood. The virus RNA may remain present in the urine longer than in the blood; the CDC recommends that urine samples be collected less than 14 days after onset of symptoms for rRT-PCR testing. Virus-specific IgM and neutralizing antibodies typically develop toward the end of the first week of illness, so Zika virus serologic testing can be done later in the course of illness. All submissions go through the state or local health department and there are specific instructions from the CDC on how to collect, prepare, and ship specimens for testing.

2. What are the current recommendations related to sexual transmission?
  • Men who have been diagnosed with Zika virus should use condoms or abstain from sex for at least six months.
  • Pregnant women with male partners who live in or travel to areas with Zika should use condoms every time they have vaginal, anal, or oral sex, or abstain from sex for during the pregnancy.
  • Both men and women should be counselled about contraceptive planning. Women with Zika virus should wait at least eight weeks after symptom onset before conceiving; men with Zika virus should wait at least six months, as it is unknown how long the virus may remain in semen. Women with possible exposure to Zika virus should wait at least eight weeks after being exposed to attempt conception; men should wait at least six months. 
3. What is microcephaly?
Microcephaly is a neonatal malformation in which infants are born with a head smaller than normal due to abnormal brain development. In some cases, newborns may develop normally, however, possible associated neurologic complications include developmental delay and seizures, as well as speech, hearing, and vision deficits, and feeding difficulties. Diagnosis can be made by ultrasound late in the second trimester or early in the third trimester, or after a baby is born. Microcephaly is a lifelong condition and treatment depends on the severity of the malformation and associated health problems.

4. Is Zika virus associated with Guillain-Barré syndrome (GBS)?
The CDC is investigating the link between Zika virus and GBS, as the Brazil Ministry of Health has reported an increased number of people who have been infected with Zika virus who also have GBS. GBS is an autoimmune disease which attacks the peripheral nervous system. Weakness of the arms and legs results, and flaccid paralysis often develops. In severe cases, the muscles of the face weaken and affect the eyes, swallowing, and breathing. Many patients with GBS have a history of a recent viral or bacterial infection, so it is possible that a percentage of those infected with Zika virus could develop GBS as well.

5. How should symptoms of Zika virus be managed?
At this time, there is no antiviral or other medication available to prevent or treat Zika virus. Rest, fluids, antipyretics, and analgesics are recommended for symptom management. It’s important to remember that aspirin and NSAIDs should be avoided until dengue virus is ruled out.

References
Centers for Disease Control and Prevention. (2016, July 14). Zika virus. Retrieved from Centers for Disease Control and Prevention: http://www.cdc.gov/zika/
Coyle, A. (2016). Zika virus: What nurses need to know. Nursing2016, 22-24.
O'Malley, P. A. (2016). Zika Virus: What We Know and Do Not Know. Clinical Nurse Specialist: The Journal for Advanced Nursing Practice, 194-197.
Todd, B. (2016). Zika Virus: An Unfolding Epidemic. AJN, American Journal of Nursing, 59-60.
 
Posted: 7/29/2016 5:15:26 AM by Lisa Bonsall, MSN, RN, CRNP | with 5 comments

Categories: Diseases & Conditions


Who you gonna call? ...Bugbusters!

Bugbuster.PNGDon’t you wish it was that easy? You could just pick up the phone, hire Bugbusters, and they’d come out and use their Sci-fi equipment to rid your facility of all those nasty “bugs” or organisms that cause health care-associated infections (HAIs). Unfortunately, it isn’t that easy; there’s no Sci-fi equipment to magically rid your facility of organisms. We’ve made strides, however, towards reducing the incidence of these infections by using a variety of evidence-based best practices.


Progress report

The Centers for Disease Control and Prevention recently published the National and state healthcare associated infections: Progress report using 2014 infection data from national acute care hospitals. This report revealed significant progress towards reducing HAIs:

  • Central line-associated bloodstream infections declined by 50% between 2008 and 2014.
  • Catheter-associated urinary tract infections showed no change overall, but there was progress made in non-critical care settings between 2009 and 2014, and in all settings between 2013 and 2014.
  • Surgical site infection declined by 17% between 2008 and 2014.
  • Clostridium difficile infections declined by 8% between 2011 and 2014.
  • Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia declined by 13% between 2011 and 2014.
As you can see, we’ve made significant progress, but there’s still much more work to be done. Every day, nearly one in 25 patients in the United States has at least one infection that they acquired during their stay in a health care facility. This shows the need to improve infection control and prevention practices in health care facilities, and other various settings.


Bugbusting best practices

So, what can we do to bust those “bugs” and prevent HAIs in our health care facilities? To start, research shows that when members of the multidisciplinary team are aware of infections and join together to take steps to prevent those infections, infection rates can be reduced by more than 70%.  Developing a culture of safety that includes teamwork, evidence-based infection prevention processes, and accountability for preventing infections is key.


Making it real

Make infections real to all members of the health care team, including environmental services personnel, transportation staff, sterile processing department staff, patients, visitors, and volunteers; not just those directly involved in patient care. After all, everyone plays a role in preventing the spread of infection.
Share stories… nothing hits home like a story of a patient who suffered harm as a result of an infection that could’ve been prevented. Take for instance, the story of an elderly patient admitted to a health care facility for knee replacement surgery.  The surgical procedure itself went smoothly, but the patient soon developed a surgical site infection, the responsible organism was MRSA. The patient spent months in the hospital for IV antibiotics, prosthetic joint removal, spacer insertion, and eventually an above the knee amputation of the affected leg. The patient, the mother of a staff physician, eventually succumbed to complications of the MRSA infection.

How could a seemingly uncomplicated surgery result in an infection that ultimately resulted in this patient’s death? Was it by the hands of a health care worker who didn’t take time to perform hand hygiene? An operating room team member who failed to follow sterile technique during the procedure? An environmental services staff member who didn’t properly clean surfaces in the patient care area? A sterile processing staff member who didn’t properly sterilize surgical instruments? A visitor who failed to perform hand hygiene before visiting the patient? The patient herself who failed to properly perform personal hygiene after surgery? Any of these scenarios could’ve caused the patient’s infection and subsequent death. When this story was told, it was difficult not to feel accountable.


Zero tolerance

There are many opportunities for infection to spread in a health care facility.  It’s important to make sure that everyone is educated about measures to prevent infection, using methods that they understand. Start with the basics...we’ve all heard it before, hand hygiene is the single most effective thing you can do to keep infection from spreading. Make sure everyone performs hand hygiene properly, every time that it’s indicated.

Develop a culture that has zero tolerance for infection and zero tolerance for failure to follow proper infection prevention practices. Empower patients, family, and other staff to speak up when infection prevention practices aren’t followed. Getting to zero is the only sure way to keep our patients safe from infection.

What infection prevention practices have been successful at your facility? Have you done anything creative to engage staff, patients, and visitors; something outside the box that you’d like to share with us?
References:
Centers for Disease Control and Prevention. (2016). “National and state healthcare associated infections: Progress report” [Online]. Accessed April 2016 via the Web at http://www.cdc.gov/HAI/pdfs/progress-report/hai-progress-report.pdf

Institute for Healthcare Improvement. (n.d.). “What zero looks like: Eliminating hospital-acquired infections” [Online]. Accessed April 2016 via the Web at http://www.ihi.org/resources/Pages/ImprovementStories/WhatZeroLooksLikeEliminatingHospitalAcquiredInfections.aspx

Yokoe, D.S., et al. (2014). SHEA/IDSA practice recommendation: Introduction to a compendium of strategies to prevent healthcare-associated infections in acute care hospitals: 2014 updates. Infection Control & Hospital Epidemiology, 36(5), 455-459.
 
Collette Bishop Hendler, RN, MS, CIC
Senior Clinical Editor
Clinical Project Manager, Lippincott Procedures

Wolters Kluwer, Health Learning Research & Practice


 
Posted: 5/9/2016 7:35:08 AM by Lisa Bonsall, MSN, RN, CRNP | with 2 comments

Categories: Diseases & Conditions Patient Safety


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