Anesth Pain Med 2012; 7: 170～173 ￭Case Report￭
Hypoventilation and hypokalemia in a patient with poor oral intake in the postanesthesia care unit -A case report-
Department of Anesthesiology and Pain Medicine, Institute of Medical Sciences, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon, Korea
Yu-Ri Yi, and Byeong-Mun Hwang
We encountered a case of hypoventilation and hypokalemia in a of untreated depression. Recently, she had eaten very little. patient with poor oral intake in the postanesthesia care unit (PACU). Preoperative vital signs were maintained within normal values. A 44-year-old woman underwent a total abdominal hysterectomy Three days before surgery, laboratory findings were as follows: under general anesthesia. She was transferred to the PACU after
2 hr of surgery. After 11/2 hr, the patient exhibited hypoventilation, serum sodium levels, 140 mmol/L; serum potassium levels, 3.4 muscle weakness, and mental changes. She was reintubated and mmol/L; serum chloride levels, 107 mmol/L; blood urea nitro- transported from the PACU to the intensive care unit. The arterial gen, 3.8 mg/dl; blood creatinine levels, 0.4 mg/dl; and serum blood gas analysis results were as follows: pH, 7.27; PaCO2, 65 albumin levels, 2.8 g/dL. On the day of surgery, the results of mmHg; PaO2, 68 mmHg; and serum potassium levels, 2.48 mmol/L. After 6 hr, she recovered with full consciousness. (Anesth Pain a thyroid function test were as follows: serum T3, 0.90 (nor- Med 2012; 7: 170∼173) mal range, 0.7−2.0 ng/ml); serum thyroid-stimulating hormone, 0.79 (normal range, 0.3−4.6 μIU/ml); and serum free T4, Key Words: Hypokalemia, Hypoventilation, Postanesthesia care unit. 10.7 (normal range, 7.0−20.0 pmol/L). Before surgery, she had experienced extreme dietary restriction due to depression and stress. She was not medicated before surgery. Various complications can occur during the postanesthesia The patient underwent a total abdominal hysterectomy that period [1-3], including hypoventilation in patients admitted to lasted for 2 hr under general anesthesia. Anesthesia was admi- the postanesthesia care unit (PACU) [2]. However, it is rare nistered by intravenous injection of 80 mg of propofol and 30 for a middle-aged woman to hypoventilate after only 11/2 hr in mg of rocuronium. She was ventilated by a semiclosed circular the PACU. In the present report, we describe a case of circuit with a tidal volume of 400 ml and a respiratory rate of hypoventilation and hypokalemia in a patient with poor oral 12 breaths/min. The estimated partial pressure of the end-tidal intake in the PACU. carbon dioxide was 34−36 mmHg. Until the completion of the operation, 2 L/min of oxygen, 2 L/min of nitrous oxide, CASE REPORT and 2 vol% sevoflurane were administered. During the opera- tion, she received 1,000 ml of Hartmann’s solution, and the A 44-year-old woman (160 cm tall and weighing 41 kg) urine output was 100 ml. At the end of the surgery, 0.4 mg was scheduled to undergo a total abdominal hysterectomy for of glycopyrrolate and 15 mg of pyridostigmine were admini- the treatment of a uterine myoma. She had a medical history stered. She was able to open her eyes in response to a verbal order; therefore, she was extubated. After the patient regained Received: November 15, 2011. Revised: 1st, December 17, 2011; 2nd, February 20, 2012. consciousness, she was transferred to the PACU. In the PACU, Accepted: March 13, 2012. the electrocardiogram was monitored and blood pressure was Corresponding author: Byeong-Mun Hwang, M.D., Department of measured. Peripheral arterial oxygen saturation was measured Anesthesiology and Pain Medicine, Institute of Medical Sciences, Kangwon National University Hospital, School of Medicine, Kangwon National by pulse oximetry (SpO2); 10 L/min O2 was administered to University, 17-1, Hyoja 3-dong, Chuncheon 200-947, Korea. Tel: the patient through a facial Venturi mask. Postoperative vital 82-33-258-2238, Fax: 82-33-258-2271, E-mail: [email protected] signs were maintained within normal values. The SpO2 was
170 Yu-Ri Yi and Byeong-Mun Hwang：Hypoventilation and hypokalemia with malnutrition 171 maintained at 96−98%. She did not receive opioids during increase the likelihood of a positive outcome in such patients. perioperative periods. Rose et al. [1] reported several factors that increase the risk of The patient met the discharge criteria after 40 minutes of respiratory complications, including patient factors (age ＞ 60 transfer to the PACU. However, the patient was awaiting years, male gender, diabetes, and obesity), surgical factors discharge because of a busy clinical situation. After 11/2 hr, the (emergencies and cases ＞ 4 hr), and anesthetic choice (pre-
SpO2 of the patient was found to be 90%. The patient medication and induction with thiopental and fentanyl at ＞ exhibited hypoventilation, weakness of both upper and lower 2.0 μg/kg/hr, fentanyl and morphine combination, and atracu- extremities, and altered mental status (drowsiness). An rium at ≥ 0.25 μg/kg/hr) in the PACU. In the present case, electrocardiogram showed changes with ST depression and T the patient did not have any of the risk factors mentioned wave flattening. The patient was intubated after intravenous above. Airway obstruction, hypoventilation, and hypoxemia are injection of 30 mg of rocuronium with mask ventilation. the foremost manifestations of airway compromise [4]. Rose et Immediately after intubation, arterial blood gas analysis al. [1] reported that the risk of postoperative hypoventilation
(ABGA) results were as follows: pH, 7.27; PaCO2, 65 mmHg; was 0.2% in patients administered general anesthesia. Apnea - PaO2, 68 mmHg; HCO3 , 27 mmol/L; and serum potassium and hypoventilation are usually caused by central depression or levels, 2.48 mmol/L. No abnormal findings were detected on peripheral neuromuscular blockade [4]. postoperative brain magnetic resonance imaging and a simple Alveolar hypoventilation is the most common cause of chest radiograph. Two hours after the surgery, she was postoperative hypoxemia in the PACU. The persistent effects transported from the PACU to the intensive care unit (ICU) of inhaled and intravenous anesthesia, neuromuscular blocking for mechanical ventilation after intubation. drugs, and opioids all contribute to alveolar hypoventilation in In the ICU, mechanical ventilation on controlled ventilation the PACU [4]. Even without residual relaxant effects, the mode was administered with the following parameters: FiO2, patient can exhibit postoperative ventilatory insufficiency. 0.5; respiratory rate, 16 breaths/min; and tidal volume, 400 ml. Hypoventilation caused by hypokalemia can occur in patients Subsequently, the patient was treated with Hartmann’s solution, with diabetic acidosis, myopathy, thyrotoxic disease, familial 100 ml of 20% albumin, and 40 mEq of potassium chloride. hypokalemic periodic paralysis, and renal tubular acidosis [5-9]. Two hours after the surgery, laboratory findings were as Hypoventilation caused by hypokalemia may also occur in follows: pH, 7.37; PaCO2, 43 mmHg; PaO2, 265 mmHg; malnourished patients because malnutrition can cause hypoka- serum sodium levels, 139 mmol/L; serum potassium levels, 2.4 lemia, muscle weakness, and myopathy. mmol/L; serum chloride levels, 108 mmol/L; serum calcium In the present case, we considered and ruled out the follow- levels, 1.0 mmol/L; and serum magnesium levels, 0.49 mmol/L. ing diagnoses as the cause of the patient’s paralysis. First, we Four hours after the surgery, the ABGA results were as ruled out thyrotoxic hypokalemic periodic paralysis because the follows: pH, 7.39; PaCO2, 39 mmHg; PaO2, 142 mmHg; and results of a thyroid function test showed a euthyroid state with
FiO2, 0.3. Laboratory findings were as follows: serum sodium no symptoms of thyroid disease. Second, we ruled out the levels, 138 mmol/L; serum potassium levels, 3.2 mmol/L; familial form of hypokalemic periodic paralysis because the serum chloride levels, 111 mmol/L; serum calcium levels, 1.1 patient did not have a family history, and the age of onset for mmol/L; and serum magnesium levels, 0.59 mmol/L. Six hours the familial form is usually ＜ 20 years. However, we could after the surgery, the patient recovered with full consciousness not confirm this diagnosis because genetic testing was not and was extubated. The patient received nutritional care for 7 possible in our setting. Third, we ruled out renal tubular days from the second postoperative day. On the ninth posto- acidosis because the ABGA results indicated respiratory perative day, she was discharged without any complications. acidosis, not metabolic acidosis. Fourth, we ruled out residual
muscle relaxant effects because more than 31/2 hr had passed DISCUSSION since the administration of a single 30 mg dose of rocuro- nium. Furthermore, there was no evidence of other potential Respiratory complications are the most frequently encount- causes of residual neuromuscular blockade in the patient. ered problems in the immediate postanesthetic period and are However, we could not totally exclude this possibility because major contributors to the mortality and morbidity associated we did not assess nerve stimulation responses. with anesthesia [4]. Early diagnosis and treatment can greatly Malnutrition is often complicated by hypokalemia, which is 172 Anesth Pain Med Vol. 7, No. 2, 2012 a recognized cause of skeletal muscle weakness, paralysis, and that can be caused by redistribution of potassium between rarely, respiratory failure [10]. Hypoventilation can be caused intracellular and extracellular compartments (alkalosis, hypoka- by hypokalemia and muscle weakness [5,11]. We assumed that lemic periodic paralysis, or chronic heart failure; alcohol inges- extremity weakness and hypoventilation of the patient caused tion; administration of insulin, lithium, amphotericin B, mineral by hypokalemic non-thyrotoxic paralysis. In the present case, corticoids, or β2-mimetics; or intoxication with barium or this concept was supported by the occurrence of respiratory chloroquine) or by reduction in the total body potassium distress that improved with respiratory support and was resol- content (increased gastrointestinal liquid loss, loss of liquid via ved after potassium administration. This patient’s malnutrition the skin, renal potassium loss, or deficient potassium ingestion) may have been due to anorexia caused by depression and [6,11]. In the present case, except for malnutrition, all other stress. In the present case, hypoxia was assumed because of causes of hypokalemia could be excluded. The following respiratory muscle weakness and hypoventilation caused by factors favor malnutrition, rather than intoxication, as a cause malnutrition and hypokalemia. In the PACU, the patient’s of hypokalemia in a patient: (1) history of poor oral intake, hypoventilation may have been delayed because of stimuli (2) decreased albumin, (3) decreased blood urea nitrogen, and provided immediately after surgery. (4) decreased serum potassium levels. Based on this For these reasons, we concluded that hypokalemia was the background, we concluded that malnutrition was the cause of major cause of hypoventilation in a patient with malnutrition the patient’s hypokalemia in the PACU. During the surgery, in the PACU. However, hypoventilation of the patient may be except for malnutrition, all other causes for hypokalemia could caused by a combination of factors, such as persistent effects be excluded. of inhaled and intravenous anesthesia, residual effects of Adequate nutritional status affects survival and quality of life neuromuscular blocking agents, and used drugs during in surgical patients. More specifically, an adequate nutritional operation. status can improve a patient’s ability to tolerate therapies, Hypokalemia can cause a variety of clinical manifestations including surgery, chemotherapy, and radiation [13-15]. Poor due to alterations in the excitability of neuromuscular tissues. nutritional status has been associated with increased posto- From the clinical viewpoint, this effect accounts for the perative morbidity and mortality in surgical patients. Therefore, association of hypokalemia and muscle weakness [10,11]. Myo- the nutritional status of surgical patients should be assessed pathy also may occur in patients with malnutrition [6]. Addi- using various anthropometric measurements, immunologic mea- tionally, hypokalemia can lead to central nervous changes, with surements, and evaluation of serum protein markers. The most confusion and affective disorders [11,12]. In the present case, commonly used laboratory markers for assessing the nutritional altered mental changes may have been caused by hypokalemia status are serum protein markers, and some are more appro- and hypercarbia. The PaCO2 of the patient before reintubation priate for the short-term or long-term assessment of nutritional may have been higher than the measured value (65 mmHg) status [14,15]. after reintubation. A decreased albumin level is significantly associated with Postoperative hypokalemia was assumed to result from a low more postoperative complications, hospital readmissions, reope- dietary intake by the patient during the waiting period before rations, and ICU admissions [15]. The albumin level is the surgery. In the PACU, the ABGA results were as follows: included if the value is obtained within 20 days of surgery, as - pH, 7.27; PaCO2, 65 mmHg; PaO2, 68 mmHg; HCO3 , 27 this would be an accurate reflection of nutritional status before mmol/L; and serum potassium levels, 2.48 mmol/L. In the surgery [14,15]. In both clinical practice and epidemiology, - present case, the predicted pH and HCO3 were 7.275 and 26.5 BMI is the most frequently used indicator of individual and mmol/L, respectively. The patient had primary respiratory collective general nutritional status [13,15]. This nutritional acidosis without compensatory metabolic alkalosis, as suggested parameter is an important predictor of postoperative morbidity by the abovementioned cause. In the PACU and ICU, the and mortality [13]. In the present case, the albumin levels and change in serum potassium levels was insignificant, despite the BMI of the patient were lower at 2.8 g/dl and 16 kg/m2, change in pH from 7.37 to 7.27. The use of different measu- respectively. We neglected these aspects during the evaluation ring machines may account for this result. of nutritional status because of the relatively young age of the Malnutrition reduces the level of serum potassium in humans patient. Therefore, it is important to assess nutritional status [6]. 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