Case series: Dexmedetomidine and ketamine for anesthesia in patients with uncorrected congenital cyanotic heart disease presenting for non-cardiac surgery.

The number of patients with uncorrected congenital cyanotic heart disease is less but at times some may present for non-cardiac surgery with a high anesthetic risk. Some of these may even be adults with compromised cardiopulmonary physiology posing greater challenges to the anesthesiologist. The authors have used a combination of dexmedetomidine and ketamine for anesthesia for non cardiac surgery in five patients with cyanotic heart disease and right to left shunt (3-Eisenmenger's syndrome, 2-Tetralogy of Fallot). The sympathoinhibitory effects of dexmedetomidine were balanced with the cardiostimulatory effects of ketamine, thereby maintaining good cardiovascular stability. The analgesia was good and there was no postoperative agitation. This drug combination was effective and safe for patients with cyanotic heart disease for non cardiac surgeries.

Introduction

The advancement in pediatric cardiac surgery has resulted in an increasing population of young adults with grown up congenital heart disease (GUCHD).[1] Most of these adults would have undergone a palliative, reparative, or a corrective surgery in early childhood or sometime later. Those with various congenital cyanotic heart diseases (CCHD) pose a greater risk to life and are usually corrected early. However, in many developing nations there still exist a number of patients with uncorrected CCHD, both as children or young adults. Some of the acyanotic heart diseases like atrial septal defect (ASD) and patent ductus arteriosus (PDA) may be relatively asymptomatic for several years because of the balance between the systemic and pulmonary circulation and therefore the diagnosis is missed. The pulmonary blood flow is more in the initial phase along with a high pulmonary artery pressure. Gradually, the pulmonary vascular resistance (PVR) starts rising and over the years, often reaches a point where it is irreversible and then they also pose as cyanotic CHD. Eisenmenger's syndrome is thereby a common cause of GUCHD in adults with a reversed or a bidirectional shunt flow. In children however, tetralogy of Fallot (TOF) remains the commonest cause of CCHD;[2] though there are reported series of 40 years and older, many of which without even a palliative surgery earlier.[3]

These children or adults often present for noncardiac surgery, mainly emergencies and the anesthetic risk is high even for minor surgeries.[45] We present a series of five different cases of cyanotic heart disease with right to left (R-L) shunt where a combination of dexmedetomidine and ketamine (ketodex)[6] was used and the patients recovered well.

Case Report

Written informed consent was taken from all the five cases being presented. There were three cases of Eisenmenger's syndrome and two of TOF. Four were GUCHD while one was a child (TOF), and they were all uncorrected cyanotic heart disease with (R-L) shunt. The complete perioperative data of all the patients is shown in Table 1. Case 1-3 were managed with total intravenous (IV) anesthesia with a combination of dexmedetomidine 1 μg/kg and ketamine 2 mg/kg IV infused over 10 min. They were short duration surgeries of >90 min with spontaneous respiration, supplemented with oxygen via face mask. Case 4 and 5 required endotracheal intubation (details mentioned later). IV paracetamol was added for analgesia and the hydration was maintained with a balanced salt solution 10-15 ml/kg/hr. Infective endocarditis prophylaxis was administered to all the patients. Standard monitoring was used in all cases and all the patients were observed in the intensive care unit (ICU) for at least 24 h.

Table 1

Patient characteristics and perioperative data

Case 4 was a 20-year-old female patient, a diagnosed case of TOF who presented with a frontal lobe abscess with a 12 mm midline shift and features of septic shock. She was posted for emergency craniotomy and drainage of the abscess. There was a history of occasional episodes of cyanotic spells since the last 1 year. However, she had not undergone any corrective or palliative surgery and was not on any medication. Preoperative evaluation revealed SpO286% on room air, arterial blood gas (ABG) analysis showed PaO247.8 mmHg, pH 7.465, PaCO250.3 mmHg, and HCO330 mmol/l. She was being managed with vasopressors (noradrenaline: 0.05-0.07 g/kg/min) to maintain the mean arterial pressure (MAP) above 65 mmHg. After preoxygenation, the patient was induced with dexmedetomidine 1 g/kg and ketamine 2 mg/kg over 10 min. Anesthesia was maintained on controlled ventilation with vecuronium and an infusion of dexmedetomidine (0.7-1.0 g/kg/h) and ketamine (2 mg/kg/h). Paracetamol 1 g IV was added for analgesia though no inhalational anesthetic was used for maintenance. Cardiac output and systemic vascular resistance (SVR) were monitored by FlotracTM. SVR was maintained <1,200 dyne.s/cm5 by an infusion of noradrenaline (0.05-0.1 g/kg/min). There was a large parietal abscess and about 100 ml of pus was drained. In view of the raised intracranial pressure (ICP) and septic shock, she was electively ventilated in the ICU.

Case 5 was a 2-year-old boy who was diagnosed as TOF with a large subaortic VSD, bidirectional shunt, severe pulmonic stenosis, and overriding of aorta with a small sized pulmonary artery on echocardiography.[7] The child had developed right hemiparesis at 1 year of age and his heart disease was detected during the work up. He recovered well over the next few months, but could not undergo any palliative surgery for TOF. He developed a malignant right parietal lobe infarct with features of raised ICP at 2 years of age. A decompressive right hemicraniectomy was done under general anesthesia. The child developed cerebrospinal fluid (CSF) leak from the surgical site and an external lumbar drain was placed 3 days later for controlled CSF drainage. During both the above procedures, dexmedetomidine (1 g/kg and 1-1.5 g/kg/h) and ketamine (2 mg/kg and 2-2.5 mg/kg/h), respectively were used for induction and maintenance of anesthesia. The former surgery was done with controlled ventilation using muscle relaxation and the latter procedure was carried out with the two drugs along with oxygen via face mask with spontaneous respiration. The child maintained hemodynamic stability perioperatively and recovered uneventfully.

Discussion

In patients with uncorrected CHD, some of whom may be adults, the anesthetic management is focused on preventing a further increase in the R-L shunt by maintaining SVR, controlling PVR, decreasing oxygen consumption, and prevention of arrhythmia and hypovolemia. Avoiding an increase in the R-L shunt prevents a decrease in the flow of blood to the lungs, thus preventing a further fall in the oxygenation of an already compromised circulation.

Transesophageal echocardiography is known to be very useful in real time assessment of the preload, cardiac contractility, and intracardiac shunting. We did not have it in our institution, but it should be used wherever possible even for noncardiac surgeries. Postoperative monitoring in a high dependency unit is recommended even after short procedures.[8]

Ketamine is preferred, though all commonly used IV induction agents can be used if given judiciously. It is important that the rate and dose used is adjusted so as to cause a minimal fall in the SVR in order to prevent an increase in the R-L shunt.[9] Theoretically, IV agents score over inhalation agents as the latter may prolong induction time in patients with R-L shunt.[10] Peripheral nerve blocks may be added where appropriate, but care should be taken to avoid systemic toxicity of local anesthetics.

Dexmedetomidine is a highly selective alpha-2 agonist that provides anxiolysis and cooperative sedation without respiratory depression. It decreases central nervous system sympathetic outflow in a dose-dependent manner and has analgesic effects. There is evidence that it alleviates postoperative delirium also.[11] It reduces the hyperdynamic responses (increased MAP and heart rate (HR)) mediated by the sympathetic nervous system and attenuates the cardiovascular and neuroendocrine response to surgery. The dose-dependent hypotension and bradycardia may limit the sole use for anesthesia or procedural sedation.[12]

Ketamine is a fast-acting general anesthetic which produces profound analgesia, maintains normal pharyngeal-laryngeal reflexes, and causes cardiovascular stimulation. The downside to its use is the high incidence of emergence agitation.

The sympatho-inhibitory effects of dexmedetomidine are balanced with the cardio-stimulatory effects of ketamine, thereby maintaining a stable hemodynamic profile within normal physiological range, in cases with R-L shunt. There is no significant rise in PVR or fall in SVR with this drug combination. Both the drugs offer analgesia via different modes and their effects appear additive. They are also known to preserve dose dependent airway reflexes and spontaneous breathing, thus useful in short duration surgeries where controlled ventilation can be avoided.[13] The emergence delirium likely to occur with ketamine is negated with the sedation of dexmedetomidine. Mester et al., used the same drug combination for cardiac catheterization in 16 children with CHD with good results.[14] There are no other reported cases of the use of these drugs in the literature for similar patients.

The authors have used this combination of ketamine and dexmedetomidine in five patients with R-L shunt who presented for emergency noncardiac surgery. The HR and blood pressure were maintained within 10% of the baseline. There was no episode of intraoperative hemodynamic instability, desaturation, arrhythmias, or heart failure. There was no requirement of any additional vasopressor to maintain SVR. The analgesia was also adequate for the surgery. Awakening from anesthesia was smooth and none of the patients had any postoperative agitation.

There are other known techniques of administration of safe anesthesia in such cases like various regional nerve blocks and general anesthesia with newer inhalational agents, which are safe and effective. However, each technique has its inherent pros and cons and it much depends on the attending anesthesiologist on what the person is most confident with.

In this series the combination of dexmedetomidine and ketamine provided excellent intraoperative hemodynamic stability. It was found to be effective and safe for anesthesia for patients with cyanotic heart disease, though larger controlled trials are recommended before any conclusion is drawn.