Anaesthetic management of uncorrected TOF for emergency LSCS

ANAESTHETIC MANAGEMENT OF A PREGNANT PATIENT WITH UNCORRECTED TETROLOGY OF FALLOT COMING FOR EMERGENCY CAESAREAN SECTION - A CASE REPORT. ABSTRACT: Among the congenital heart diseases causing right to left shunt Tetrology of Fallot is one of the most common congenital heart disease. It is characterized by VSD, over-riding of aorta, right ventricular outflow obstruction and Right ventricular hypertrophy. Uncorrected TOF causes significant morbidity and mortality to the patient. Pregnancy in a patient with uncorrected TOF results in worsening of symptoms as well as poses additional challenge to the anesthesiologist. Anesthetic management in such a patient, requires a clear understanding of the anatomical defects, its physiological adaptations, events and drugs that can alter the magnitude of the R-L shunt. The challenges encountered in such a patient are due to chronic hypoxia, polycythemia, pulmonary hypertension, cardiac failure and altered acid-base status. We present a case report of a patient of uncorrected TOF who underwent Emergency Caesarean section. Key words: Tetrology of fallot, Pregnancy, General anesthesia. INTRODUCTION: TOF is one of the most common cyanotic congenital heart defect. It accounts for nearly 5% of the cases of congenital heart disease in pregnancy. The basic developmental defect is due to the displacement of anterior and superior infundibular septum which gives rise to the classical features of VSD, over-riding of aorta, right ventricular outflow obstruction and Right ventricular hypertrophy. The mortality rates of these patients without surgery is very high such that their survival upto the mid age group is very minimal and rare. More than 85% survival can be achieved with surgery. Intracardiac repair prior to pregnancy not only reduces the maternal risks and improves the fetal viability but also improves the quality of life. CASE SCENARIO: A 26 yr old primigravida weighing 62kg was admitted in the Labor ward on 14/6/13 at 8.15 PM , with H/O of 9 months of amenorrhea . She was referred from a peripheral hospital for severe oligohydramnios. She was a booked case. She was a known case of Tetrology of fallot diagnosed at 10 years of age and was advised to undergo surgery but she had not undergone surgery and she was not on any regular medications. She had undergone prenatal visits in the nearby peripheral hospital. In the past she had complaints of dyspnea, easy fatigability and cyanotic spells on and off. All the symptoms were exaggerated during the present pregnancy. Her LMP was on 1/10/2012 and EDD was on 8/7/2013. GENERAL EXAMINATION: Patient was conscious and oriented .She had Conjunctival suffusion, Pedal edema grade 1,Pan digital clubbing grade 2 and cyanosis(both peripheral & central). All the peripheral pulses were well felt. Her pulse rate was 117/min ,regular and her BP was 170/100 mm Hg in the Right Upper limb in the Supine position and 164/100 mmHg in the Right Upper limb in the Left Lateral Position. There was no variation in the pulse and BP in the extremities. Her oxygen saturation in the room air was 85-86%. SYSTEM EXAMINATION: On examination of the cardiovascular system, both first and second heart sounds were heard and a systolic murmur of grade 3 heard over the aortic and pulmonary areas, radiating all over the precordium. On examination of the respiratory system normal vesicular breath sounds were heard and there were no added sounds. Her abdominal examination showed uterus 32 weeks size and fetal heart sounds were heard. Her higher functions were normal and there were no functional neurological deficits. Her airway examination showed Modified Mallampatti Score-2 and her neck movements were adequate. She was on Nil Per Oral since 2 PM. LABORATORY INVESTIGATIONS (done at a peripheral hospital on 26/6/13): Her Complete blood picture showed Hb- 18 gm/dl and PCV- 57%. Her total count was 14,800 and Differential Counts were Polymorphs 68%, Lymphocytes 24% and Eosnophils 3% and her platelet count was 2,60,000/cu.mm. Her bleeding time was 2min 15sec and Clotting time was 4min 22sec. Her blood group was O positive, random blood sugar was 85mg/dl, Blood urea was 33mgm% and Serum creatinine was 0.9mgm%. Her routine urine examination was normal. Ultrasonogram of the abdomen showed single live Intrauterine fetus of 36 wks gestational age with cephalic presentation and with good fetal movements and heart rate. Biparietal Diameter was 9.4 cm, Femur Length was 7.2 cm and Amniotic Fluid Index was 2 cm. Her electrocardiogram showed Right Ventricular Hypertrophy with strain pattern. Echocardiogram done in the first trimester showed large subaortic ventricular septal defect with a predominant right to left shunt, there was 40-50% overriding of the aorta and right ventricular cavity was predominant with right ventricular hypertrophy. Her biventricular function was within normal limits. There was moderate to severe infundibular pulmonary stenosis and her pulmonary gradient was 68 mm. PRE OPERATIVE MANAGEMENT: She was assessed for surgery under General Anaesthesia under ASA III E. She was kept in propped up position with a wedge under the right hip and O2 was kept by mask. High risk informed consent was obtained from the patient and patient’s attender, after explaining the risk involved .18 gauge IV line was started and she was given crystalloids as per previous hour urine output. She was given infective endocarditis and aspiration prophylaxis. Ventilator was checked and kept ready. She was shifted to the theatre with O2 by mask and a wedge under the right hip. INTRAOPERATIVEMANAGEMENT: She was shifted inside the operating room and connected to pulse oximeter, Electrocardiogram and Non invasive blood pressure monitors. Phenylephrine , Esmolol and Metoprolol were kept ready. She was preloaded with 500 ml Ringer Lactate to maintain adequate Haemotocrit. Her pre induction vitals were Sp O2 -89% with O2 face mask, PR-108/min and BP- 160/100 mm Hg in the right upper limb. She was premedicated with Inj. Glycopyrrolate 0.2 mg IV, and laryngoscope, 6.0,6.5,7.0 size ET tubes, airways, gum elastic bougie , stylet, suction apparatus were kept ready. Painting & draping of the surgical field were done by the obstetrician. The patient was then induced by rapid sequence induction using titrated doses of diluted Inj.Ketamine 2 mg/kg IV slowly and Inj. suxamethonium 1.5mg /kg IV was given and intubated with 7.0mm cuffed oral ETT tube which was fixed after checking for B/L air entry. The bag compliance was checked soon after intubation & found to be well compliant. She was ventilated with 50% O2 : 50% N2O.Her PR was 100-110/min, BP was 140/90- 150/100 mmHg, SpO2 was 93-94% and her lungs were clear. She delivered a a term, alive, girl baby with weight of 2.25 kg and Apgar score of 6/10 at 1min and 9/10 at 5min. After the delivery of the baby she was given Inj.Morphine 0.1mg/kg IV and Inj. Oxytocin 15U was given slowly as infusion. Her uterus contracted well. Anesthesia was maintained with Inj. Vecuronium 4+1 mg IV, 66% N2O :33% O2 and Isoflurane 0.4-0.6%. Her Sp O2 was maintained above 90%. She was hyperventilated manually to avoid intraoperative hypoxia, hypercarbia and acidosis. Her PR was 80-90/min and BP was 130/80- 140/90 mm Hg. The wound was closed in layers after checking for adequate contraction of the uterus and absence of any bleeding points. The total intra operative blood loss was 400ml and Urine output was 100 ml . The entire intraoperative period was uneventful and smooth without any untoward events . POST OPERATIVE MANAGEMENT: She was planned for extubation after meeting with all the Extubation criteria. An emergency intubation tray and suction apparatus were all kept ready. A gentle suctioning of the mouth & pharynx was done & patient was reversed with Inj.Neostigmine 0.05mg/kg IV and Inj.Glycopyrrolate 0.01 mg/kg IV and she extubated uneventfully. She was supplemented with O2 by facemask at 4-6l/min. Her PR was 96/min, BP was 136/86 mm Hg and Sp O2 was 89-90% with O2. The patient was then shifted to PACU for observation. The patient was given Inj.Paracetamol 1g IV TDS and Inj.Tramadol 75 mg IM SOS for post op analgesia. Fluid management was carried out as per urine output monitoring. The post operative period was uneventful and she was discharged on 19/6/13 with the advise to undergo surgical intervention. DISCUSSION: Tetrology of fallot presents with four main classical features which were first described by Fallot in 1888. The four components of TOF are ventricular septal defect , obstruction to right ventricular outflow, aortic overriding of VSD, and right ventricular hypertrophy . The large VSD exposes the RV to the high aortic pressure which leads to Right ventricle hypertrophy. The pressure in the right ventricle is nearly equal to the systemic pressure. When the obstruction to pulmonary vessels is severe, the pulmonary blood flow is reduced markedly and a large volume of desaturated systemic venous blood is shunted from right to left across VSD. NORMAL CARDIOVASCULAR CHANGES DURING PREGNANCY: The pregnancy is neither uncommon nor a disease. Even though a normal occurrence, pregnancy does have a lot of physiological changes in all the systems more so in the cardio respiratory system. This is to cope with the high BMR and growing fetus. The early appearance of cardiovascular changes implicates hormonal cause due to estrogen and progesterone. As pregnancy advances there is increase in the metabolic demand and body mass imparting significant demand on the cardiovascular system. The blood volume increases by 40-50%, heart rate increases by 10-15 beats/min. The stroke volume and the cardiac output increase by 30-50% which is further accentuated during labor. Early signs of cardiac compromise may become apparent in the first trimester and peak at 20 to 24 weeks of pregnancy when cardiac output reaches a maximum. From 24 weeks onward cardiac output is maintained at high levels. Cardiac output only begins to decline only in the post-partum period. All these are well tolerated in a healthy female and child birth is uneventful. CARDIAC CHANGES IN A PREGNANT PATIENT WITH UNCORRECTED TOF: Pregnancy in a patient with uncorrected TOF posses serious risks. Preexisting pulmonary hypertension is a main concern. Adding to the flame, cardiac output is also elevated in pregnancy which leads to increased venous return to the hypertrophic right ventricle. These changes, together with decreased systemic vascular resistance in TOF increases the right to left shunt. Hence the oxygen supply is decreased, but the demand is increased. Hematocrit is increased , and cyanosis is worsened. These combined changes stresses a system which is already compromised. A pre pregnancy hematocrit of more than 65%, oxygen saturation of less than 80% , preceding cardiac failure and right ventricle pressure more than the systemic pressure indicate poor outcome. The shunt is increased by (1) the decreased systemic vascular resistance, (2) the increased pulmonary vascular resistance, and (3) the increased myocardial contractility.  CYANOTIC SPELL: Another main concern in these patients going for caesarian section is the cyanotic spell. A cyanotic spell presents with rapid drop in saturation in response to surgical or any other stimulation. Eletrocardiogram may show ischaemic changes and BP may fall. Although the precise pathology remains unknown, it is thought due to infundibular spasm which worsens right ventricular outflow obstruction. Beta blockers reduces the infundibular spasm and thereby decreases the heart rate , increase SVR and relieves the right ventricle outflow obstruction. Patients with history of cyanotic spell should continue beta blocker before surgery. Once there is a suspect of cyanotic spell during surgery the inspired oxygen concentration is increased and possibility of endotracheal tube disconnection should be ruled out. The plane of anaesthesia is deepened with narcotics and benzodiazepines. Fluid bolus should be given at 10-20 ml/kg. Phenylephrine bolus can be given. If repeated bolus needed then nor-adrenaline can be started as an infusion. In case of non availability of IV propranolol , either IV Metoprolol or IV Esmolol can be used to manage the intraoperative cyanotic spell. FETAL OUTCOME IN A PREGNANT PATIENT WITH TOF: In pregnant patients with TOF, there is exaggeration of maternal cyanosis and hypoxia which adds additional risks for both mother and fetus. Severe maternal hypoxia may lead to miscarriage, IUGR, preterm delivery and Intra Uterine Death. Patients with TOF have an increased risk of fetal loss, and their offspring are more likely to have congenital anomalies than offspring in the general population. Mothers who are not cyanosed and who have undergone surgical repair do well in pregnancy. ANAESTHETIC CONCERNS: Our main goal during anesthesia is to decrease the shunting ie, maintain systemic vascular resistance and to avoid any decrease in peripheral vascular resistance. Hence, we opted for General Anesthesia for this patient. We induced our patient with ketamine in order to maintain systemic vascular resistance. Though intermittent positive pressure ventilation can decrease pulmonary blood flow by increasing pulmonary vascular resistance, we did controlled ventilation of the patient's lungs to avoid excessive positive airway pressure. 50%N2O: 50% O2 was given till the birth of baby, and after delivery, N2O 60% : 40% O2 was given, keeping a close watch on oxygen saturation. A drop in saturation, sudden fall in BP and ischaemic changes in ECG should raise the suspicion of cyanotic spell. Phenylephrine, Esmolol and Metoprolol were kept ready. The patient was preloaded with 500 ml Ringer Lactate to maintain adequate hematocrit and maintained in adequate plane with narcotic and nitrous-oxygen mixture. The patient was deliberately hyperventilated manually to avoid intraoperative hypoxia, hypercarbia and acidosis which increases the pulmonary vascular resistance. Oxytocin was not administered as bolus since it would affect peripheral vascular resistance; however, we did administer intravenous oxytocin diluted in RL and very slowly. As the entire intraoperative period was uneventful and patient recovered from neuromuscular blockade, patient was extubated smoothly and observed in PACU where adequate care was given for postop analgesia and fluid balance to maintain her vitals stable. She was discharged on the 6th postoperative day and referred to the cardiologist. CONCLUSION: The above case report outlines a successful management of a parturient woman coming for emergency caesarean section with uncorrected Tetrology of Fallot & subsequently observed in the Intensive care unit, discharged uneventful. Patients with uncorrected Tetrology of Fallot surviving till their antenatal period is very rare. Their course in the antenatal period is life threatening. They carry a higher risk of morbidity & mortality and posses a great challenge to the anesthesiologist. So, these type of patients need to be managed in a tertiary center, where an integrated approach of various specialties is available in bringing out a successful outcome. REFERENCES: Stoeltings Anesthesia and co-existing disease, Fifth edition. Anderson RH, Allwork SP, Ho SY, Lenox CC, Zuberbuhler JR. Surgical anatomy of tetralogy of Fallot. J Thorac Cardiovasc Surg 1981;81:887–96. . Cunningham FG, Gant NF, Leveno JK. Medical and Surgical Complications in Pregnancy; Williams Obstetrics, 21st edition 2001, McGraw-Hill; 1193.  Iftikhar Ahmed, Tetrology of Fallot and Pregnancy, RMJ 2004;29: review article. Upasana Bhatia,Imdu A Chadha,V B Rupakar. Anesthetic management of known case of tetralogy of fallot undergoing brain abscess drainage – A case report. Indian J Anaesth 2001; 45: 370-371. Roberts SL, Chestnut DH. Anesthesia for the obstetric patient with cardiac disease. 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