Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.55 no.2 Campinas Mar./Apr. 2005
Total intravenous anesthesia for partial laryngectomy in 28 weeks pregnant patient. Case report*
Anestesia venosa total para laringectomía parcial en paciente en la 28ª semana de embarazo. Relato de caso
José Costa, TSA, M.D.I; Dalva Maria Carvalho Mendes, TSA, M.D.II; José Eduardo de Oliveira Lobo, TSA, M.D.III; Adriana Barrozo Ribeiro Furuguem, M.D.IV; Gabriel Gilberto Santos, M.D.V
IResponsável CET HNMD
IICo-Responsável CET HNMD
IIIMédico assistente do HNMD
IVEx-residente da CNRM do HNMD
VME3 do CET do HNMD
BACKGROUND AND OBJECTIVES: Anesthesia
for pregnant patients is a challenge to the anesthesiologist because of the
risks for mother and fetus. There are many complications described by the literature,
such as fetal malformations, premature birth, maternal hemodynamic instability
and even fetal death. The objective here is to show a 28 weeks pregnant patient
submitted to partial laryngectomy under total intravenous general anesthesia
with propofol, remifentanil and cisatracurium.
CASE REPORT: Patient 29 years, 59 kg, primigravida of 28 weeks with previous diagnosis of epidermoid carcinoma close to the right vocal chord, scheduled for laryngectomy. Initial monitoring consisted of noninvasive and invasive blood pressure, cardioscopy, oxicapnography and continuous cardiotocography accomplished by the obstetrician. Venous puncture in right and left arm with 16G and 18G catheter, respectively. Patient received intravenous midazolam (1 mg), cefazolin (1 g), metoclopramide (10 mg) and dipirone (1 g). Patient was oxygenated with 100% O2 under mask for 3 minutes and intravenous anesthesia was induced with propofol in controlled target infusion (3 µg.mL-1) and continuous remifentanil (1 µg.kg-1 in bolus and 0.2 µg.kg-1.min-1 for maintenance). Cisatracurium (13 mg) was administered for muscle relaxation and tracheal intubation was achieved with 6.5 mm spiral-reinforced cuffed tube. Anesthesia was maintained with propofol and remifentanil in infusion pump, in addition to cisatracurium complementation. Fetus was continuously monitored with cardiotocography accomplished and analyzed by the obstetrician. Propofol and remifentanil infusion pumps were turned off at the end of completion and patient woke up 10 minutes later, without pain and hemodynamically stable, being then referred to the post-anesthetic care unit.
CONCLUSIONS: Total intravenous anesthesia with propofol and remifentanil has provided hemodynamic stability for mother and fetus, with early and smooth emergence.
Key words: ANESTHETIC TECHNIQUES, General: total intravenous; PREGNANCY; SURGERY, Laryngeal: partial laryngectomy
JUSTIFICATIVA Y OBJETIVOS: Anestesia para
paciente embarazada constituye un desafío al anestesiologista en virtud de los
riesgos para la madre y el feto. Son muchas las complicaciones descritas por
la literatura como malformaciones fetales, alumbramiento prematuro, instabilidad
hemodinámica materna y hasta muerte fetal. El objetivo de este caso es mostrar
una paciente embarazada de 28 semanas, sometida a laringectomía parcial bajo
anestesia general venosa total con propofol, remifentanil y cisatracúrio.
RELATO DEL CASO: Paciente con 29 años, 59 kg, primigesta de 28 semanas con diagnóstico previo de carcinoma epidermóide próximo a la cuerda vocal derecha, siendo indicada laringectomía. La monitorización inicial se constituyó de presión arterial no invasiva y invasiva, cardioscopía, oxicapnografía y cardiotocografía continuada realizada por el tocólogo. Punción venosa en el miembro superior derecho y miembro superior izquierdo con catéter 16G y 18G respectivamente. Fueron administrados por vía venosa midazolan (1 mg), cefazolina (1 g), metoclopramida (10 mg) y dipirona (1 g). La paciente recibió oxígeno a 100% bajo máscara por 3 minutos e inducción venosa fue hecha con el uso de propofol en infusión en la dosis escogida de 3 µg.mL-1 y remifentanil continuado (1 µg.kg-1 en bolus y 0,2 µg.kg-1.min-1 de mantenimiento). Como bloqueador neuromuscular fue administrado cisatracúrio (13mg) y procedida la intubación traqueal con un tubo de 6,5mm alambrado con balonete. Fue mantenida en un plano anestésico con propofol y remifentanil en bomba además de complementaciones de cisatracúrio. El feto permaneció monitorizado continuamente con cardiotocografía realizada y analizada por el tocólogo. Después del término de la cirugía fueron apagadas las bombas infusoras de propofol y remifentanil con la paciente despertando 10 minutos después. Despertó sin dolor y hemodinámicamente estable siendo entonces encaminada a la sala de recuperación pos-anestésica.
CONCLUSIONES: La anestesia venosa total con propofol y remifentanil proporcionó estabilidad hemodinámica para la madre y el feto, con un suave y precoz despertar.
It is estimated that 1% to 2% of pregnant women will need surgery during pregnancy. Most common cases include appendicitis, cholelithiasis, ovarian cyst, breast tumors and trauma, among others. Whenever possible, regional anesthesia should be the technique of choice. However, when general anesthesia is required, there is a major challenge for the medical team: protect the binomial mother-fetus 1-3.
Several periods should be considered during pregnancy. In the early period, until the 17th day, embryo exposure to chemical agents may lead to two different situations: injured cells that are totally replaced without compromising the embryo, or large numbers of injured cells leading to early embryo death and abortion 2. As from this period until the 60th day there is a stage with massive cell proliferation and differentiation, when embryo organs and systems are formed. This is the critical period where fetal exposure to undesired drugs may lead to fetal malformations. That is, whenever possible, surgeries during this period should be postponed.
There is then a period in which fetal exposure to chemical agents no longer results in malformations, but in interference with fetal growth and/or with the development of already formed systems, among them central nervous system 2.
Aiming at orienting professionals about the fetal risk of some drugs, the FDA (Food and Drug Administration) has proposed a drug classification 2,4:
· Category A - controlled studies have shown no risk
· Category B - without evidence of human risk
· Category C - risk cannot be ruled out
· Category D - positive evidence of risk
· Category X - counterindicated during pregnancy.
Anesthetic drugs vary in category. Propofol, for example, belongs to category B. But the evaluation in a case-by-case basis is what counts most. If propofol is used in high doses, with hemodynamic changes, it may be more prejudicial than a category C drug. Opioids, halogenates and muscle relaxants blockers belong to category C. However, the high molecular weight of muscle relaxants blockers and the presence in their structure of two amino quaternary groups (high ionization level) make difficult its placental crossing and they are considered safe agents 2,5. Benzodiazepines, widely used in anesthesia, belong to category D, but their use in single dose has no fetal effect. Evidences of risk with benzodiazepines during gestation are only observed in patients under continuous use of the drug 2.
The objective here is to show the anesthetic approach and intraoperative care a patient with 28 weeks of pregnancy, submitted to total intravenous general anesthesia for partial laryngectomy.
Pregnant patient, 29 years old, 59 kg, 152 cm, physical status ASA III, previously submitted to biopsy of a lesion close to right vocal chord with histopathological diagnosis of epidermoid carcinoma. Laryngectomy was indicated after a meeting with the Oncology Committee.
During preanesthetic evaluation patient was alert, oriented, hydrated, pale (+/4+), with no jaundice, cyanosis or fever. Patient was also hemodynamically stable with blood pressure of 110 x 70 mmHg, heart rate of 70 bpm and respiratory rate of 16 irpm. Cardiovascular and respiratory systems evaluation was normal.
Preoperative tests had the following results: red cells: 3.63 million, hematocrit: 30%; hemoglobin: 10.4 g/dL: leucocytes: 10,900; Na: 133; K: 4.1; G: 91; U: 18; Cr: 0.7. Coagulogram, ECG and chest X-rays were normal. Intubation difficulty was evaluated according to Mallampati index in class II.
Patient was monitored with cardioscopy at DII lead, pulse oximetry, mean noninvasive and invasive blood pressure (radial E), capnography and diuresis/h. Two veins were assessed with 18G and 16G catheters in left and right upper limbs, respectively.
Fetus was monitored with cardiotocography and the obstetrician was present in the operating room. A pad was placed under the right hip aiming at shifting the uterus to the left and decreasing aortocaval compression.
Patient received midazolam (1 mg), cefazolin (1 g), dipirone (1 g) and metoclopramide (10 mg). After 3-minute oxygenation with 100% O2 under mask, total intravenous general anesthesia was induced with propofol infusion in target dose of 3 µg.mL-1 and 1 µg.kg-1 bolus remifentanil plus 0.2 µg.kg-1.min-1 for maintenance. After loss of consciousness, Sellick's maneuver was performed. Cisatracurium (13 mg) was used as muscle relaxant and tracheal intubation was easily achieved with 6.5 mm spiral-reinforced cuffed tube. Patient was maintained under controlled ventilation with O2 (2 L.min-1) and tidal volume of 7 mL.kg-1.
Surgery has evolved without intercurrences and lasted 210 minutes with patient stable throughout the procedure, with heart rate around 60 to 70 bpm, SpO2 around 98% to 100%, systolic blood pressure around 100 to 120 mmHg and PETCO2 around 28 to 35.
Cardiotocography was also normal with normal fetal heart rate and lack of uterine contractions indicating premature labor. Tracheal intubation was replaced by tracheostomy without decreasing oxygen saturation. Superficial cervical block with 0.25% bupivacaine (10 mL) was performed for postoperative analgesia.
Patient was hydrated with lactated Ringer's solution (2000 mL) and 5% glucose solution (500 mL). Diuresis was maintained in approximately 100 mL/h.
Ten minutes after propofol and remifentanil infusions withdrawal patient was spontaneously breathing and cooperative. Since there was no neuromuscular function monitoring, a clinical parameter, namely the ability to maintain head raised for 5 seconds, was adopted. This indicates enough muscle strength to protect airways and maintain adequate ventilation, when neuromuscular block monitoring is unavailable. Patient received atropine (0.75 mg) and neostigmine (1.5 mg) and was transferred to the PACU with tracheostomy, hemodynamically stable and with no complaints, where she was maintained with O2 (5 L.min-1) under Hudson's mask and forced air warming system.
Patient was discharged one week later and returned one month later for tracheostomy removal. Patient was followed by Obstetrics and Head and Neck Surgery clinics.
Labor started at 41 weeks gestation, however due to encephalopelvic disproportion a C-section was indicated. A female baby was born with Apgar scores 9 and 10 in the 1st and 5th minutes, respectively.
Pregnancy related physiological changes due to hormonal and mechanical factors bring major consequences for anesthetic handling 3,7, especially when patient has to be submitted to general anesthesia.
In our case, patient had a severe disease requiring urgent intervention. There could be systemic disease manifestations, such as paraneoplastic syndrome and local tumor invasion, which would also influence the technique to be adopted.
Patient's clinical and lab evaluation should always be very careful. It is critical to evaluate the presence of disease-related airway obstruction, such as local compression, hemodynamic changes due to position and difficult tracheal intubation. Impossibility of tracheal intubation and effective ventilation is the major anesthesia-related mortality cause 3. Tracheal intubation is more difficult in pregnant women as compared to non-pregnant population due to increased chest diameter, increased breasts and laryngeal edema 1. Material to deal with difficult airways should be readily available. Attention should be given to hemoglobin concentration, which should be kept above 10 g% 8 to assure adequate oxygen transportation. Changes in electrolytes concentration could have been observed in our case due to paraneoplastic syndrome, but this has not been found.
Oximetry evaluates maternal oxygen saturation and indirectly fetal oxygen supply. Other factors contribute for this supply, such as maintenance of adequate pressure levels to maintain placental perfusion. So, blood pressure monitoring is also very useful and ideally systolic blood pressure should be maintained above 100 mmHg to maintain adequate placental perfusion 8,9. The presence of both endogenous (caused by surgical stress - superficial anesthesia) and exogenous (drug administration) catecholamines may also determine uterine vasoconstriction impairing fetal oxygenation. Maternal hyperventilation should be avoided for shifting hemoglobin dissociation curve to the left thus impairing placental oxygen transfer, in addition to stimulating uterine vasoconstriction. The ideal is to maintain normal ventilation with PaCO2 in approximately 32 mmHg 5,7,8.
Uterine activity and fetal heart rate monitoring is critical and should be routinely performed. This technique allows the diagnosis of premature labor and physiological or pathological fetal decelerations. For initial stage pregnancy, an option would be to monitor through transvaginal ultrasound 1. Early treatment with b-adrenoceptor agonist seems to be effective for premature labor 1,10. It is important to understand the effect of anesthetic drugs on fetal heart rate to prevent misinterpretation of fetal heart rate changes caused by these drugs 8.
Because patient was in the supine position, a pad was placed under the right hip to shift the uterus to the left and minimize aortocaval compression, which would impair placental blood flow.
Oxygenation with 100% O2 for 3 to 5 minutes is needed in pregnant patients to decrease the risk of hypoxemia during anesthesia induction 1,3.
Pregnant patients are always considered with full stomach and measures should be taken to prevent bronchoaspiration. In our case, measures included Sellick's maneuver throughout induction until endotracheal tube cuff inflation after intubation. Tracheal tube choice (6.5 mm) has taken into consideration patient's size in addition to possible presence of airway edema.
Drugs were chosen due to their short action.
Remifentanil has been widely studied for labor and C-section analgesia, especially in patients with counterindications for regional anesthesia 11-14. Its prolonged use does not change excretion time and most studies highlight its fast onset, fast metabolism and excretion as major factors to prevent undesirable effects such as neonate respiratory depression. Continuous infusion provides stable plasma concentration maintaining adequate blood pressure. In addition, due to drug peculiarities, blood concentration is rapidly decreased after its withdrawal without residual effects.
Cisatracurium was the muscular relaxant of choice due to its low histamine release. As to placental transfer, this class of drugs does not lead to any fetal impairment in most cases, due to its minimal crossing. There is no clinical effect on the neonate 5,7.
In this specific surgery, when tracheal tube is replaced by tracheostomy tube, there may be oxygen saturation decrease, which was not observed in our case due to the easiness of the technique.
Studies have shown that maternal pain leads to placental blood flow decrease3 and an adequate postoperative analgesia is required. For such, in addition to intravenous dipirone, the surgeon has performed cervical block with 0.25% bupivacaine (10 mL).
Pregnant women are major glucose suppliers to fetus, since fetus is unable to synthesize it. So, it is important to prevent maternal hypoglycemia through hydration with 120 mL/h of 5% glucose solution 8. We have used 500 mL of 5% glucose solution in addition to lactated Ringer's solution.
In the postoperative period, patient was maintained with 5 L.min-1 oxygen under Hudson's mask and with a forced air warming system already used during surgery. Cold may also trigger catecholamine release with lower fetal oxygen supply due to uterine vasoconstriction 8.
We acknowledge Dr. Paulo Roberto Alcântara Aguiar and Dr. Maryangela Monteiro for their support and cooperation with the team involved in this case report.
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Dra. Adriana Barrozo Ribeiro Furuguem
Address: Av. Ary Parreiras, 15/1004 Icaraí
ZIP: 24230-320 City: Niterói, Brazil
Submitted for publication July 12, 2004
Accepted for publication December 2, 2004
* Received from CET/SBA do Serviço de Anestesiologia do Hospital Naval Marcílio Dias, Rio de Janeiro RJ