Obstetric use of nitroglycerin: Anesthetic implications
The patient has consented for the clinical details of the case for publication in the journal for academic purpose.\nA 22-year old primigravida presented to obstetrics department with complaint of fever on sixth postpartum day after having undergone vaginal delivery elsewhere. Although the patient was febrile on presentation, the vital parameters were found to be normal. The per abdominal examination by the obstetrician revealed the uterine height of 24 weeks and abdominal ultrasonogram done showed placenta invading into the myometrium, short of serosa. The patient was scheduled to undergo manual removal of placenta. All the biochemical and hematological investigations were found to be normal. Airway was found to be normal. The patient was kept fasting and tablet ranitidine (150 mg) and alprozolam 0.25 mg was administered as premedication on the day of surgery.\nAn intravenous line was secured with 20 G cannula in the operating room. Standard noninvasive monitoring was done using anesthesia monitor (S/5™ critical care monitor, Datex Ohmeda, Helsinki, Finland). Induction was achieved with injection (inj.) fentanyl (100 μg), inj. propofol (100 mg) along with inj. atracurium (25 mg). Proseal laryngeal mask airway (PLMA) size 3 was inserted and the correct placement was confirmed by lube test and end tidal carbon dioxide tracing on monitor. Anesthesia was maintained with nitrous oxide –oxygen in 60:40 ratio and sevoflurane (1 MAC). Despite repeated attempts, the operating surgeon failed to gain access to the uterine cavity owing to the closed internal os. Therefore it was decided to administer NTG as a bolus in the dose of 50 μg to facilitate prompt cervico uterine relaxation. The desired relaxation and access to placenta was achieved in this manner. However a modest fall in arterial oxygen saturation (SpO2-94%) was noticed and N2O was discontinued to ascertain the cause of fall in saturation. The circuit disconnection, leaks, and soda lime exhaustion were ruled out. Chest auscultation revealed normal bilateral equal breath sounds. The oxygen saturation returned to normal (99%) after sometime. In the meantime, boluses of 50 μg and 100 μg of NTG were again repeated at the request of operating surgeon. The administration of second bolus led to significant fall in saturation with SpO2 falling to 89%. Along with, tachycardia was also witnessed with fall in both systolic and diastolic blood pressures. An arterial blood gas sample drawn during this time period revealed a paO2 of 56.4 mmHg and the difference from the baseline (ABG) arterial blood gas is shown in . However, this episode of desaturation too responded to volume resuscitation and discontinuation of nitrous oxide.\nPlacenta was completely removed following uterine relaxation achieved by the use of NTG without substantial hemorrhage. At the completion of procedure, inj. glycopyrrolate (0.5 mg) and inj. neostigmine (2.5 mg) was administered and PLMA removed with the assumption of spontaneous respiration and reflexes. The postoperative period was uneventful and the patient was subsequently discharged after 3 days.