Inadvertent venous air embolism during cesarean section: collapsible intravenous fluid bags without self-sealing outlet have risks. Case report

Bakan, Mefkur; Topuz, Ufuk; Esen, Asim; Basaranoglu, Gokcen; Ozturk, Erdogan

doi:10.1016/j.bjan.2012.09.001

Abstracts

The anesthesiologist must be aware of the causes, diagnosis and treatment of venous air embolism and adopt the practice patterns to prevent its occurrence. Although venous air embolism is a known complication of cesarean section, we describe an unusual inattention that causes iatrogenic near fatal venous air embolism during a cesarean section under spinal anesthesia. One of the reasons for using self-collapsible intravenous (IV) infusion bags instead of conventional glass or plastic bottles is to take precaution against air embolism. We also demonstrated the risk of air embolism for two kinds of plastic collapsible intravenous fluid bags: polyvinyl chloride (PVC) and polypropylene-based. Fluid bags without self-sealing outlets pose a risk for air embolism if the closed system is broken down, while the flexibility of the bag limits the amount of air entry. PVC-based bags, which have more flexibility, have signifi cantly less risk of air entry when IV administration set is disconnected from the outlet. Using a pressure bag for rapid infusion can be dangerous without checking and emptying all air from the IV bag.

Cesarean Section; Embolism, Air; Fluid Therapy; Infusions, Intravenous

O anestesiologista deve estar ciente das causas, do diagnóstico e do tratamento de embolia venosa e adotar padrões de prática para prevenir sua ocorrência. Embora a embolia gasosa seja uma complicação conhecida da cesariana, descrevemos um caso raro de desatenção que causou embolia gasosa iatrogênica quase fatal durante uma cesariana sob raquianestesia. uma das razões para o uso de bolsas autorretráteis para infusão em vez dos frascos convencionais de vidro ou plástico é a precaução contra embolia gasosa. Também demonstramos o risco de embolia venosa com o uso de dois tipos de bolsas plásticas retráteis (à base de cloreto de polivinil [PVC] e de polipropileno) para líquidos intravenosos. As bolsas para líquidos sem saídas autovedantes apresentam risco de embolia gasosa se o sistema de fechamento estiver quebrado, enquanto a flexibilidade da bolsa limita a quantidade de entrada de ar. bolsas à base de pvc, que têm mais flexibilidade, apresentam risco significativamente menor de entrada de ar quando o equipo de administração intravenosa (IV) é desconectado da saída. usar uma bolsa pressurizada para infusão rápida sem verificar e esvaziar todo o ar da bolsa IV pode ser perigoso.

CIRURGIA, Cesárea; COMPLICAÇÕES, Embolia Gasosa; Infusões Intravenosas; Hidratação

El anestesiólogo debe de estar consciente de las causas, del diagnóstico y del tratamiento de la embolia venosa, y adoptar los estándares de práctica para prevenir su aparecimiento. Aunque la embolia gaseosa sea una complicación conocida de la cesárea, describimos aquí un caso raro de falta de atención que causó embolia gaseosa iatrogénica casi fatal durante una cesárea bajo raquianestesia. Una de las razones para el uso de bolsas autoretráctiles para infusión en vez de los frascos convencionales de vidrio o plástico, es la precaución contra la embolia gaseosa. También demostramos riesgo de embolia venosa con el uso de dos tipos de bolsas plásticas retráctiles (a base de cloruro de polivinil [PVC] y de polipropileno) para líquidos intravenosos. Las bolsas para líquidos sin salidas de autosellado, tienen un riesgo de embolia gaseosa si el sistema de cierre está roto, mientras la flexibilidad de la bolsa limita la cantidad de entrada de aire. Bolsas hechas a base de PVC, y que tienen más flexibilidad, también tienen un riesgo signifi cativamente menor de entrada de aire cuando el equipo de administración intravenosa (IV) se apaga en la salida. Usar una bolsa de presión para la infusión rápida sin verifi car y vaciar todo el aire de la bolsa IV puede ser peligroso.

CIRUGÍA, Cesarea; COMPLICACIONES, Embolia Gaseosa; Infusiones Intravenoso; Hidratación

CLINICAL INFORMATION

MD; Bezmialem Vakif University, School of Medicine, Department of Anesthesiology and Reanimation

Corresponding author

ABSTRACT

The anesthesiologist must be aware of the causes, diagnosis and treatment of venous air embolism and adopt the practice patterns to prevent its occurrence. Although venous air embolism is a known complication of cesarean section, we describe an unusual inattention that causes iatrogenic near fatal venous air embolism during a cesarean section under spinal anesthesia. One of the reasons for using self-collapsible intravenous (IV) infusion bags instead of conventional glass or plastic bottles is to take precaution against air embolism. We also demonstrated the risk of air embolism for two kinds of plastic collapsible intravenous fluid bags: polyvinyl chloride (PVC) and polypropylene-based. Fluid bags without self-sealing outlets pose a risk for air embolism if the closed system is broken down, while the flexibility of the bag limits the amount of air entry. PVC-based bags, which have more flexibility, have significantly less risk of air entry when IV administration set is disconnected from the outlet. Using a pressure bag for rapid infusion can be dangerous without checking and emptying all air from the IV bag.

Keywords: Cesarean Section; Embolism, Air; Fluid Therapy; Infusions, Intravenous.

Introduction

Venous air embolism (VAE) is a potentially life-threatening complication of surgical and invasive procedures. The anesthesiologist must be aware of its causes, diagnosis and treatment and adopt the practice patterns to prevent its occurrence. Although VAE is a known complication of cesarean section¹, we describe an unusual inattention that causes iatrogenic near fatal VAE during a cesarean section under spinal anesthesia. The patient gave written permission for the authors to publish this report.

Case Report

A 40-yr-old woman, (85 kg, 155 cm) at 38 weeks' gestation had uterine contractions and was scheduled for cesarean section. She was healthy (ASA physical status I) and had history of uneventful uterine (myomectomy) and thyroid (sub-total thyroidectomy) surgeries 1 and 3 years ago, respectively.

Upon arrival, her blood pressure was 120/80 mm Hg and her heart rate was 75 bpm. We inserted a 22G intravenous (IV) cannula at the dorsum of the hand (a large-bore cannula could not be inserted at the ward), and a bladder catheter, initiated volume preload, and performed blood work (hemoglobin level was 9.1 g.dL^-1). We obtained consent for surgery and anesthesia, and transferred the patient to the operating room.

Both the patient and the fetus were stable upon arrival in the operating room. We monitored ECG, non-invasive blood pressure and SpO₂, and administered oxygen 5 L.min^-1 via facemask, inserted another 18G intravenous canula to the antecubital vein for rapid volume expansion and performed spinal anesthesia with the patient in the sitting position. We placed a 25-gauge spinal needle atraumatically in the first attempt to the subarachnoid area at L3-L4 level and injected 2.5 mL of hyperbaric bupivacaine 0.5% without incident. At this point the patient had received a total of 600 mL of crystalloid solution through both catheters. The patient was positioned in supine and the surgery began at the 10^th minute of spinal anesthesia. Five minutes later, the patient had nausea while her arterial pressure tended to decrease slightly (Table 1). We administered ephedrine 5 mg twice and accelerated IV fluid administration by squeezing the IV fluid bag with a pneumatic pressure infuser. A healthy male infant was delivered with an APGAR score 9. We administered IV oxytocin 10 IU. Blood loss was approximately 400 mL and 1,100 mL of fluid had been administered up to this point. Between the 25^th and 30^th minutes of spinal anesthesia, the patient had suddenly become agitated and confused with SpO₂ levels 84-80%. We administered ephedrine 10 mg, midazolam 2 mg IV and began performing manual mask ventilation with 100% oxygen. The pulse of radial artery was palpable, both lungs were easily expanded with low airway resistance, but the SpO₂ level was decreasing and EtCO₂ was 12 mm Hg. At this time, the anesthesiologist recognized the IV administration set (both drip chamber and tubing) full of air and clamped immediately. There was also some amount of air in the IV bag (measured as 55 mL after the case) with no fluid remaining. We administered propofol 100 mg and rocuronium 20 mg and performed urgent endotracheal intubation, but the EtCO₂ level did not change and SpO₂ values decreased. Circulatory collapse developed in minutes and was treated with noradrenaline, atropine, adrenaline and volume expansion with a colloid solution (Table 1). After we restored hemodynamic condition, we inserted an arterial cannula and placed a central venous catheter to the left internal jugular vein (the attempt at the right internal jugular vein failed). Repeated attempts to aspirate the air from the central venous catheter had failed. The first arterial blood gases analysis revealed pH: 7.27, pCO₂: 43 mm Hg, pO₂: 111 mm Hg, HCO₃: 19 mmol.L^-1, BE: -7 mmol.L^-1, lactate: 3 mmol.L^-1. Before extubation pH was 7.38 and lactate level decreased to 2 mmol.L^-1. The patient was extubated 50 minutes after surgery. The patient regained consciousness with no neurologic deficits and was transferred to the postoperative care unit.

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After the case, a conversation with the nurse anesthetist cleared the story: when positioning the patient for spinal anesthesia, the IV administration set detached from the IV line and soiled unintentionally. When changing the set, she had turned the IV bag upside down (as in Figure 1-A) and some air entered into it. Using a pneumatic pressure infuser for rapid volume administration caused VAE.

Discussion

Generally, a small amount of air in the venous vasculature gets absorbed spontaneously without sequel, but the rapid entry of a large amount of air can result in significant morbidity and mortality. The lethal volume of air has been described as 200-300 mL or 3-5 mL.kg^-1 for adults from case reports, while the rate of air entrainment is also important². To calculate the estimated volume of air entered into the current patient's vasculature, we tested two different kinds of 1,000 mL IV fluid bags available in our institute and found some interesting outcomes.

Polyvinyl chloride (PVC) is a chemical widely used in the manufacturing of collapsible IV fluid containers preferred for its flexibility. However, vinyl-containing products represent a health risk³ and environmental hazard and many healthcare companies have undertaken programs designed to find replacements for PVC. The IV fluid bag in this recent case was a polypropylene (PP)-based material with lower flexibility compared with PVC. We tested PVC and PP-based bags, changed the IV set by turning the bag upside down (as in the recent case) after various amounts of fluid were evacuated, and then measure the amount of air in the bag with a 50 mL syringe and a three-way stopcock. We repeated the test 5 times and the median results are shown in Table 2. After changing the IV administration set, the amount of air entered into the IV fluid bag depends on the volume of fluid used (if more fluid was used, there will be more space for air entry) and the flexibility of the bag, while flexibility significantly limits the amount of air entry (Table 2).

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By the time that nurse anesthetist changed the IV set in the recent case, the volume of fluid used in the 1,000 mL bag was 300-400 ml and we found that a maximum of 240-300 mL of air can enter into a PP bag at the same conditions while in a PVC bag this amount decreases to 120-130 mL. The amount of air remaining in the bag in this recent case was 55 mL and the volume of drip chamber and tubing was 15 ml. Thus, the estimated volume of air embolism was 170-230 mL.

In literature, plastic bottles have been responsible for the risk of VAE^4,5. One of the reasons to use self-collapsible IV fluid bags instead of conventional glass or plastic bottles is to take precaution against air embolism. Air embolism is out of the question when collapsible bags are used as a closed infusion system. To our knowledge, this is the second case report on venous air embolism related to the use of collapsible IV fluid bags, where the estimated volume of air entry and the bag's material were not mentioned in that case⁶. There is risk for impairment of this closed system when IV administration set is disconnected from the outlet. Self-sealing outlets become safe guards to prevent air embolism and contamination. When the administration set has to be changed, the outlet of the bag may be clamped with a forceps to prevent air entry (Figure 1-B).

The incidence of VAE during cesarean delivery reportedly ranges between 11% and 97%, depending on the sensitivity of diagnostic tools used during the procedures and the patient's position¹. Predisposing factors in pregnancy include placenta previa, previous uterine surgery, hypovolemia and maternal positioning. Air entrance from ruptured uterine veins, especially during manual extraction of the placenta, is usually without clinical consequence despite its common occurrence. In the aforementioned case, possible air embolism from the surgical site may worsen the clinical effect of iatrogenic air embolism.

Due to increases in the right ventricular afterload, VAE may lead to acute right ventricular failure and a subsequent decrease in left ventricular output². Inotropic support to overcome the afterload is the logical management of this condition, while adrenaline was more effective than noradrenaline in our case.

In conclusion, collapsible intravenous fluid bags without self-sealing outlet carry risk of air embolism if the closed system is broken down, while the bag's flexibility decreases the amount of air entry. Using a pressure bag for rapid infusion can be dangerous without checking and emptying all air from the IV bag. Clinicians must be aware of this possibility, especially when other predisposing conditions exist - such as the cesarean section.

References

1. Lew TW, Tay DH, Thomas E - Venous air embolism during caesarean section: More common than previously thought. Anesth Analg. 1993;77:448-452.
2. Mirski MA, Lele AV, Fitzsimmons L, Toung TJK - Diagnosis and treatment of vascular air embolism. Anesthesiology. 2007;106:164-177.
3. Food and Drug Administration (FDA), Public Health Notification: PVC Devices Containing the plasticizer DEHP. Center for Devices and Radiological Health. From, www.fda.gov/safety/dehp.html Accessed July 2002.
4. Gray AJ, Glover P - Air emboli with Haemaccel^® Anaesthesia. 1999;54:790-792.
5. Suwanpratheep A, Siriussawakul A - Inadvertent venous air embolism from pressure infuser bag confirmed by transesophageal echocardiography. J Anesthe Clinic Res. 2011;2:2-10.
6. Pant D, Narani KK, Sood J - Signifi cant air embolism: A possibility even with collapsible intravenous fluid containers when used with rapid infusion system. Indian J Anaesth. 2010;54:49-51.