Aortocaval Compression Syndrome


Article Author:
Diann Krywko


Article Editor:
Kevin King


Editors In Chief:
Ron Feller
Grant Goold
Kyle Cohen


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Kyle Blair
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Daniyal Ameen
Altif Muneeb
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
6/6/2019 3:41:27 PM

Introduction

Aortocaval compression syndrome is also known as a supine hypotensive syndrome.  This pathophysiologic state occurs in a pregnant female, typically after 20 weeks gestation, when the patient is placed in the percent position. The impedance of blood flow back from the lower extremities to the maternal heart and central circulation occurs from compression of the uterus on the inferior vena cava, and also the aorta.  This subsequently limits blood flow out to the placenta, and may result in morbidity and mortality to the mother and fetus alike.  Due to the increased morbidity and mortality to both patients involved, it is critical that the health care team be aware and recognize this entity as a cause of hypotension in the pregnant patient, and immediately initiate maneuvers to correct it if suspected.

Etiology

The lordotic curvature of the lumbar spine causes an outward bowing of the vertebral column in the lower (L4 - L5) spinal area towards the abdominal-pelvic cavity. The uterus is located intra-abdominally at the same L4 – L5 vertebral level.  Juxtaposed between the lumbar spine and the uterus is the inferior vena cava. While gravity works to keep the uterus and enclosed fetus outward and off of the inferior vena cava and lumbar spine when the mother is upright or sitting, that is not the case when in the supine position. Once in the supine position, gravity allows the uterus to rest posteriorly onto the lordotic spine, potentially compressing the inferior vena cava under its weight. As a result of this compression, the blood flow returning from the extremities may be impeded drastically, resulting in maternal hypotension.

The description of the supine hypotensive syndrome was originated in 1953 by Howard et al[1]. This paper noted a decrease in blood pressure in 18 of 160 gravid females studied who were placed in a supine position.  They attributed this decrease in systemic blood pressure to occlusion of the inferior vena cava by the gravid uterus, though without radiologic or angiographic confirmation.  In 1966, Bieniarz et al[2]. measured blood pressure in the upper and lower extremities in conjunction with aortic angiographic measurements to infer aortic compression by the uterus with supine positioning. Following this study, the aorta was implicated in the supine hypotensive syndrome, making the term aortocaval compression syndrome synonymous with the supine hypotensive syndrome.

Epidemiology

Unfortunately, trauma and/or accidental injury occurs not infrequently during pregnancy, with a known complication rate of six to seven percent of all pregnancies[3].  Aortocaval compression syndrome may occur in the setting of trauma when the patient is placed in the position of safe transport, spinal immobilization precautions and resuscitation position, however, has also been noted to occur in routine procedures and deliveries when the maternal patient is placed in the same position. It occurs in patients with gestational age greater than 20 weeks, though may occur earlier in certain conditions.

Pathophysiology

The uterus has a blood flow of approximately 60 milliliters per minute in the non-pregnant state.  However, at term, the uterus commands an impressive 600 milliliters per minute, which is a ten-fold increase.  Because of this increased vascular dynamic state, even a mild decrease in blood return may result in marked negative effects on maternal and fetal circulation. Aortocaval compression syndrome is characterized by initial tachycardia and late bradycardia, pallor, diaphoresis, nausea, hypotension, and dizziness. All of these symptoms are attributable to the impedance of blood flow back into maternal circulation from the lower extremities, which have increased venous pressures progressively throughout pregnancy.  It occurs when a pregnant woman lies on her back and subsequently resolves when she is turned on her side, thus alleviating the compressing pressure of the gravid uterus on the vena cava.

History and Physical

Physical examination does not reveal specific, pathognomonic signs for this syndrome.  Diagnosis of aortocaval compression is based upon clinical assessment and suspicion, however, may be accompanied by ultrasound diagnosis.  Without knowledge of this pathophysiologic state, the syndrome will likely go unrecognized.  Particular attention should always be paid to the vital signs, with knowledge as to normal changes in pregnancy as related to trimester[4].  Blood pressure decreased throughout pregnancy, however, returns to normal at term.  In the first and second trimesters, both the diastolic blood pressure and the systolic blood pressure decrease by 15 to 20 mmHg.  Therefore, any hypotension is abnormal in a third-trimester patient. As with any hypotensive patient, multiple etiologies should be simultaneously sought after and treated expeditiously.  These include, but are not limited to, traumatic hepatic, splenic or renal bleeding, pelvic fractures, ruptured uterus, placental abruption, amniotic fluid embolus, pulmonary embolus, sepsis and other. 

Evaluation

Evaluation of aortocaval compression syndrome is done clinically alone. There may be a possible role in ultrasound evaluation, though this has yet to be studied.

Treatment / Management

Once other causes of hypotension are treated and/or ruled out, then the physical movement of the uterus off of the spine (and inferior vena cava) is necessary.  This may be accomplished in one of the following ways.  When trauma is not involved, simply placing the patient in the left lateral position may be done. However, when trauma is present, immobilization of the spine must simultaneously occur, and different maneuvers are indicated[5].

The patient will likely be on a backboard with cervical spine immobilization necessary, which presents a unique challenge.  There are three ways listed to accomplish the lateral position without compromising the immobilization. First, isolated elevation of the right hip alone may alleviate the compression. According to the Advanced Trauma Life Support Guidelines, tilting the backboard 15 to 30 degrees to the left (right side upwards) is an additional option.  This may be done either manually or with elevators, including premade elevators or towel rolls placed under the board. This option is sometimes difficult as the weight of gravid abdomen gravitationally pulls the patient to the left side, potentially compromising spinal immobilization. Though difficult, in-line immobilization is a priority.  Finally, when either of the first two maneuvers is not optional due to moribund condition and CPR, or other, a manual displacement of the uterus to the left of the midline is the treatment. This is done by placing the provider's hand on the right side of the abdomen, lateral to the gravid uterus, and shifting the uterus to the left, and thus off of the vena cava. This maneuver is simple, requires no expertise, and is not harmful to the uterus or fetus. 

Pearls and Other Issues

 

Enhancing Healthcare Team Outcomes

The diagnosis of aortocaval syndrome is very difficult and is best done with a multidisciplinary team that includes an obstetrician, emergency department physician, radiologist, nurse practitioner, internist, and intensivist. Once the diagnosis is made, the key is to relieve pressure from the vena cava. In many cases, depending on the cause positional change will improve the symptoms. The patient should be warned that the symptoms may occur when in the supine position and a position change may be required to ease the symptoms.

 

 


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Aortocaval Compression Syndrome - Questions

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A 23-year-old female who is 33 weeks pregnant presents to the emergency department after a motor vehicle accident. The patient is supine on a backboard with a cervical collar in place. Given the patient's mechanism of injury, there is a concern for possible cervical spine injury. On arrival, the patient is hypotensive with a blood pressure of 90/70 mmHg with a heart rate of 95 beats per minute. The evaluating physician is concerned about the aortocaval compression syndrome and knows the patient needs to be re-positioned immediately to help treat the hypotension. What is the most appropriate next step of management?



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Which of the following is not caused by aortocaval compression syndrome?



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A 30-year-old G2P1 is in labor and is being prepared for normal vaginal delivery. The patient has not yet started to deliver, and misoprostol has just been placed by the obstetrician to facilitate the ripening of the cervix and facilitate the delivery. Immediately after this, the nurse informs you that the patient's blood pressure is dropping while all the other vital signs are within normal limits. On assessment, the patient is in the lithotomy position, awake and alert, and has no major complaints. Repeat vital signs show that the patient's BP is 76/50 mmHg and the pulse is 96/min. What is the next most immediate step in managing this patient?



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A 33-year-old female was brought in by the rescue team on a backboard with a cervical collar in place following a motor vehicle accident. She had been the restrained front seat passenger in a car versus car accident. The patient was 31 weeks pregnant with a normal pregnancy to this point. The patient denied abdominal pain. Vital signs at the time of arrival showed the patient was hypotensive with blood pressure 67/50 mmHg with a heart rate of 98 beats per minute. The clinician immediately tilted the patient to the left side on the backboard while the nurses established IV access. After re-positioning the patient, the blood pressure improved to 100/68 mmHg and the heart rate was then 76 beats per minute. Which of the following is the cause of the decreased maternal cardiac output in the underlying diagnosis?



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A 24-year-old pregnant female was brought to the emergency department after a motor vehicle accident. The patient was a restrained front seat driver, was wearing her seatbelt, and the airbags had deployed. She states that she is 40 weeks pregnant and has had no problems during her pregnancy. The patient is alert and oriented, has a Glasgow Coma Score (GCS) of 15, and complaining of abdominal discomfort and chest pain. Her vital signs on arrival to the emergency department are heart rate 90 beats/min, blood pressure 100/82 mmHg, respiratory rate 21 breaths per minute, and oxygen saturation 98% on room air. While the nurse is running to get the fetal doppler to check for fetal heart tones, what is the next most appropriate step in the management of this patient?



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A thirty-one-year-old woman in her third trimester of pregnancy presents to the obstetrics clinic with symptoms of dizziness, "seeing stars"/blurred vision, and palpitations. Her problems began about one month ago and upon further inquiry seem to be most prominent after she rests while lying flat. She has not lost consciousness or fallen while experiencing these symptoms. Although she did experience nausea and vomiting earlier in the pregnancy, she has not had nausea or vomiting since the first trimester. The patient has had no vaginal bleeding or spotting. She has no significant past medical or family history. She takes her daily prenatal vitamin and does not have any allergies. Vitals signs are taken and recorded. Blood pressure is 87/60 mmHg, heart rate is 113 beats per minute, her temperature is 99 degrees Fahrenheit, and respiratory rate is 16 per minute. Oxygen saturation is 98% by a pulse oximeter. Physical examination reveals tachycardia. There are no cardiac murmurs. Distal pulses are 1+ bilaterally in upper and lower extremities, and the lungs are clear to auscultation and percussion bilaterally. The patient has a gravid uterus with the fundus located approximately 30 centimeters above her pubic symphysis, and the fetal heart rate is 135 beats per minute via doppler ultrasonography. Cervical examination indicates a firm, closed, and non-effaced cervix. An EKG was performed and revealed only supraventricular tachycardia. What is the recommended first step to try and alleviate this patient's symptoms?



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Aortocaval Compression Syndrome - References

References

Supine hypotensive syndrome in late pregnancy., HOWARD BK,GOODSON JH,MENGERT WF,, Obstetrics and gynecology, 1953 Apr     [PubMed]
Compression of aorta by the uterus in late human pregnancy. I. Variations between femoral and brachial artery pressure with changes from hypertension to hypotension., Bieniarz J,Maqueda E,Caldeyro-Barcia R,, American journal of obstetrics and gynecology, 1966 Jul 15     [PubMed]
Murphy NJ,Quinlan JD, Trauma in pregnancy: assessment, management, and prevention. American family physician. 2014 Nov 15     [PubMed]
Soma-Pillay P,Nelson-Piercy C,Tolppanen H,Mebazaa A, Physiological changes in pregnancy. Cardiovascular journal of Africa. 2016 Mar-Apr     [PubMed]
Kortbeek JB,Al Turki SA,Ali J,Antoine JA,Bouillon B,Brasel K,Brenneman F,Brink PR,Brohi K,Burris D,Burton RA,Chapleau W,Cioffi W,Collet e Silva Fde S,Cooper A,Cortes JA,Eskesen V,Fildes J,Gautam S,Gruen RL,Gross R,Hansen KS,Henny W,Hollands MJ,Hunt RC,Jover Navalon JM,Kaufmann CR,Knudson P,Koestner A,Kosir R,Larsen CF,Livaudais W,Luchette F,Mao P,McVicker JH,Meredith JW,Mock C,Mori ND,Morrow C,Parks SN,Pereira PM,Pogetti RS,Ravn J,Rhee P,Salomone JP,Schipper IB,Schoettker P,Schreiber MA,Smith RS,Svendsen LB,Taha W,van Wijngaarden-Stephens M,Varga E,Voiglio EJ,Williams D,Winchell RJ,Winter R, Advanced trauma life support, 8th edition, the evidence for change. The Journal of trauma. 2008 Jun     [PubMed]

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