|Year : 2016 | Volume
| Issue : 2 | Page : 89-90
Occult hypothyroidism and postoperative noninvasive ventilation
Uma Hariharan MBBS, DNB, PGDHM, Fellowship Oncoanesthesia
Unrecognized Hypothyroidism, Respiratory Failure and Non-invasive Bilevel Ventilation
|Date of Submission||04-Oct-2015|
|Date of Acceptance||19-Mar-2016|
|Date of Web Publication||6-Sep-2016|
Department of Anesthesia and Intensive Care, Assistant Professor, Dr Ram Manohar Lohia Hospital and PGIMER, BH 41, East Shalimar Bagh, Delhi 110088, India
Source of Support: None, Conflict of Interest: None
Hypothyroidism can sometimes be first diagnosed in the perioperative period. It is one of the differential diagnoses of postoperative respiratory depression, necessitating ventilatory support. Mechanical ventilation to tide over the crisis can be either noninvasive or invasive. Noninvasive ventilation with the help of a facemask or a nasal mask must be available in the postoperative recovery area for ready use in such situations. Preoperative thyroid function tests must be carried out in suspected or high-risk cases as symptoms of hypothyroidism may not be overt or may be masked by concurrent diseases. It must be suspected as one of the causes of delayed awakening, delayed extubation, or recurrence of respiratory depression in the postoperative period.
Keywords: bi-level positive airway pressure, hypothyroidism, noninvasive ventilation, postoperative recovery, respiratory depression
|How to cite this article:|
Hariharan U. Occult hypothyroidism and postoperative noninvasive ventilation. Res Opin Anesth Intensive Care 2016;3:89-90
| Introduction|| |
Hypothyroidism can present for the first time in the postoperative period and lead to increased patient morbidity. Thyroid function tests are not routinely carried out in preanaesthetic assessment and hence asymptomatic derangements may go unnoticed. If not diagnosed in time, it can cause delayed awakening  or prolonged postoperative ventilation or even reintubation. Every postoperative area must be well equipped to handle such events successfully. Noninvasive ventilation may be considered the initial mode of airway and ventilatory management for indicated cases, especially for short-term use.
| Case report|| |
A 45-year-old American Society of Anesthesiologist grade 3 female patient with a past history of rheumatic heart disease was posted for semielective laparatomy for ileal stricture. Balloon mitral valvotomy had been performed 25 years ago for mitral stenosis (MS). She had undergone two uneventful vaginal deliveries after the balloon mitral valvotomy. Currently, she was on the following cardiac drugs: oral tablet diltiazem 30 mg twice daily, warfarin (acitrom) 4 mg twice daily, furosemide 20 mg twice daily, and digoxin 0.25 mg once daily. All of the above except warfarin were continued up to the day of surgery. Warfarin was discontinued 5 days before surgery and ecosprin 150 mg was started in the interim period. International normalized ratio was checked frequently and found to be 1.5 preoperatively. On cardiac evaluation, she had severe MS (diameter 1 cm2) with moderate mitral regurgitation with mild aortic regurgitation and tricuspid regurgitation. The left atrium was dilated with right ventricular systolic pressure = 50 mmHg and left ventricular ejection fraction = 55%. Her blood investigations were as follows: serum urea, 24 mg/dl; creatinine, 1 mg/dl; bilirubin, 0.8 mg/dl; sodium, 140 mEq/l; potassium, 4.5 mEq/l; and blood glucose, 89 mg/dl. All other preoperative blood chemistries were normal. Chest radiograph showed prominent left atrial appendage and straightening of the left heart border. In addition to standard American Society of Anesthesiologists monitoring, invasive monitoring in the form of arterial and central venous catheters was commenced. To monitor the cardiac status, intraoperative transesophageal echocardiography (TEE) monitoring was instituted after intubation. Anesthesia was induced with intravenous etomidate (8 mg), intravenous midazolam 1 mg, and intravenous fentanyl 80 μg. After confirming mask ventilation, intravenous rocuronium (muscle relaxant) 50 mg was injected slowly. Just before direct laryngoscopy and intubation, intravenous esmolol hydrochloride 10 μg and preservative-free lidocaine (40 mg) were given intravenously. After a smooth intubation and confirming bilateral air entry, the patient was put on mechanical ventilation. Anesthesia was maintained with O2+air+sevoflurane along with propofol infusion under bi-spectral index monitoring. Muscle relaxant topups were given under neuromuscular monitoring. Intraoperative TEE findings include the following: severe MS, moderate mitral regurgitation, mild tricuspid regurgitation, thickened aortic cusps with normal coaptation, aortic annulus 1.73 m2, and left ventricular ejection fraction = 45–50%. The rest of the intraoperative course was uneventful. Perioperative analgesia was provided using ultrasound-guided bilateral transversus abdominis plane block with 15 ml of 0.25% bupivacaine on each side. After return of spontaneous respiration and twitches on the neuromuscular monitor and a normal arterial blood gas analysis, the patient was extubated using standard protocols. Postoperative vital parameters were within normal limits. After being shifted to the postoperative recovery room, the patient started experiencing oxygen desaturation to 90%, which did not improve with supplemental oxygen. SpO2 further dropped to 80% over 15 min, along with labored breathing and a fall in consciousness level. Immediately, noninvasive ventilation with a tight-fitting nasal mask was instituted, along with full preparations for intubation. After 4 h of bi-level positive airway pressure (BIPAP) ventilation, the patient's condition started improving, both in oxygen saturation and consciousness level. BIPAP support was gradually decreased and the patient was finally weaned from the noninvasive ventilator once her arterial blood gas analysis normalized. She maintained her oxygen saturation and other vital parameters well. The patient was observed in the postoperative ICU for 24 h with full monitoring. At that time, thyroid function tests were carried out, apart from other routine investigations. Her thyroid stimulating hormone had increased to 18.5 μU/ml and she was immediately started on thyroxine replacement therapy. The patient was shifted to the ward later with resumption of all cardiac medicines.
| Discussion|| |
Hypothyroidism  can be subclinical and may be asymptomatic in some patients. It may manifest as delayed-onset respiratory depression and necessitate airway management as well as prolonged ventilation . The postoperative period is a crucial time and hence strict monitoring is mandatory for every patient in the recovery area. Further, equipment for noninvasive ventilation must be readily available during postoperative recovery, in addition to routine invasive ventilation equipment. In this case, hypothyroidism was diagnosed only in the postoperative period as the patient was asymptomatic preoperatively. Thyroid stimulating hormone was evaluated keeping in mind that occult hypothyroidism is a differential diagnosis in delayed respiratory depression. Noninvasive BIPAP  ventilation was successful in tiding over the crisis in our patient with undiagnosed hypothyroidism. The rest of the perioperative course was uneventful. As the patient was a known case of rheumatic heart disease, invasive intraoperative monitoring was instituted, along with other precautions including the use of etomidate  for intravenous induction, blunting of laryngoscopic response with esmolol, use of intraoperative TEE , and neuromuscular and bi-spectral index monitoring. A high index of suspicion for occult hypothyroidism should be maintained in such high-risk patients. Opioids can induce delayed respiratory depression in such patients. Noninvasive ventilation may be considered a viable option in selected patients with no risk of aspiration, with full preparations for intubation. Our patient's condition improved after thyroxine replacement therapy and short-term ventilation.
Dr Dhirja Sharma, Dr Puneet Sharma and Dr Vishal Sharma, Department of Anesthesiology and Surgical Intensive Care, Max Superspeciality Hospital, FC-60, Shalimar Bagh, Delhi 110088.
Conflicts of interest
There are no conflicts of interest.
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