Noninvasive cardiac output monitoring during anaesthetic management for caesarean delivery in parturient with severe mitral stenosis: A more relaxed look.

Sir,

Heart disease in parturient is a leading non-obstetric cause of morbidity and mortality, with mitral stenosis being the single most prevalent lesion accounting for 88% of cases.[1] Associated pregnancy induced hypertension (PIH) in such patients is a challenge to the anaesthesiologist's skill. The safety of regional anaesthesia is always questioned in such patients due to the deleterious effects on preload and afterload.[23]

Non-invasive cardiac output monitor (NICOM) is a continuous, accurate and non-invasive haemodynamic monitoring device which measures the bioreactance or the phase shift in voltage across the thorax, in response to applied high frequency transthoracic currents and has a higher success rate than bioimpedance based techniques, where patient may not be totally immobile.[3] Here, we present our experience of managing a parturient posted for lower segment caesarean section, under regional anaesthesia using NICOM.

A 28-year-old parturient (height 150 cm, weight 55 kg) with rheumatic heart disease and PIH, as well as history of balloon mitral valvotomy done 3 years ago, was scheduled for elective caesarean section at 36 weeks of gestation, with precious pregnancy. She was on tablet metoprolol 12.5 mg, tablet hydrochlorothiazide 10 mg daily, since 15 days and antibiotic prophylaxis with benzathine penicillin throughout her antenatal period as per cardiologist's advice.

The examination revealed New York Heart Association (NYHA) II status, pallor, with heart rate of 68/min, blood pressure of 140/86 mmHg, jugular venous pressure of 6 cm of H2O, bilateral pedal oedema with bluish discolouration and mild tenderness over calf muscles. Cardiovascular examination revealed loud S1 and P2 at mitral and pulmonary area with a mid-diastolic murmur. Investigations showed haemoglobin (Hb) of 6.7 g/dl and other routine investigations were within normal limits. Electrolyte and coagulation profile were also normal. Electrocardiogram (ECG) revealed the right axis deviation with sinus rhythm. Echocardiography revealed mitral valve area of 0.875 cm2 with mild regurgitation with moderate pressure gradient (36 mmHg), tricuspid regurgitation, left ventricular ejection fraction of 55% and severe pulmonary arterial hypertension, no clot, mass or vegetation. Colour Doppler of lower limb suggested mild flow restriction in femoral and popliteal arteries. Pre-operatively, 2 units of whole blood were administered over 48 h. Low molecular weight heparin (LMWH) and antibiotic were given, 12 h prior to a surgical procedure. Hb of 8.8 g/dl after blood transfusions with a haematocrit of 27%. On the day of surgery, intravenous (IV) line with 18 gauge intracath was secured, and Ringer lactate (RL) was administered at 250 ml over ½ h, initially. She received injection ranitidine 50 mg, injection metoclopramide 10 mg IV, 30 min prior to the procedure. Monitors included pulse oximetry, non-invasive blood pressure and ECG and NICOM. Automatic pneumatic compression was applied to both legs, to mimic activity in the period of perioperative immobility. Epidural catheter was inserted in the sitting position using 18 gauge Touhy needle by the loss of resistance technique, in the L2-L3 interspace. About 2% lignocaine 3 ml as a test dose was given. Analgesia upto T6 was targeted by injecting incremental doses of local anaesthetic (total 9 cc of 2% lignocaine + 6 cc of bupivacaine 0.5% with 25 μg fentanyl) with continuous monitoring of cardiac parameters. After the second incremental epidural dose, there was fall in cardiac output (CO), stroke volume (SV) and increase in total peripheral resistance, treated with bolus of 250 ml RL, the response to which was appreciated by NICOM.

A healthy male baby weighing 2.5 kg was delivered. Intraoperatively, a total 600 ml of RL solution was administered under the guidance of NICOM. Injection furosemide 10 mg and oxytocin 10 U were given slowly IV after delivery.

Postoperatively, the patient was managed in surgical Intensive Care Unit, monitored using NICOM for 10 min, considering the continued stability of the patient. Analgesia was given epidurally using 0.125% injection bupivacaine (8 ml) and fentanyl (20 μg) supplemented by injection diclofenac 75 mg in drip twice a day, as an only single prophylactic dose of LMWH given.

The pre-operative short-term use of beta blockers is safe during pregnancies; it helps to optimize diastolic filling, prevents tachycardia and decreases the incidence of maternal pulmonary oedema without adverse effects on the foetus.[4]

Diuretics help to relieve pulmonary and systemic congestion, are safe during pregnancy and use of anticoagulation is reserved in the presence of atrial fibrillation.[4] In our case, due to suspicion of deep vein thrombosis (flow restriction only), LMWH (2500 IU SC) was used as it is safe in parturients with heart disease. Epidural anaesthesia is the better choice in NYHA I and II patients, the major advantage being it permits incremental and titrated dosing to achieve a desired sensory level.

NICOM helped to monitor the haemodynamics at short- and regular-intervals. A fall in CO and SV after the second incremental dose of epidural could have led to transfusing more fluids and later on pulmonary congestion. However, due to NICOM monitoring, a well-controlled fluid management (100 ml bolus) was easier as a response to therapy could be observed in parturients. Thus, the optimal fluids required to maintain haemodynamic stability in the hypovolaemic PIH patient is possible.[56789]

When considering CO and SV monitoring capabilities, non-invasive trans-thoracic bioreactance (NICOM), and a pulse contour analysis (PICCO) coupled to transpulmonary thermodilution have been validated to detect significant CO changes.[6810] Thus, pre-operative optimization, constant intraoperative monitoring and stabilization and adequate pain relief ensure better maternal and foetal outcome.Newer non invasive monitoring devices can improve quality of perioperative management in such patients where invasive procedures can be avoided.