Post-Anesthetic Care of Pediatric Patients with Pulmonary Arterial Hypertension: Associated Factors, Results of a Survey and a Proposal for Care

Destiny F. Chau, MD
Department of Pediatrics, Division of Anesthesiology
Children's Hospital of the King's Daughters

Meera Gangadharan, MBBS
Department of Anesthesiology
University of Texas Medical Branch at Galveston

Introduction
Pulmonary hypertension (PH) is a detrimental hemodynamic state of increased pulmonary arterial pressure representing the end result of a heterogeneous group of diseases. It is well-recognized that PH is associated with major perioperative morbidity and mortality in children. Rates of cardiac arrest and death in children with pulmonary arterial hypertension (PAH) are at least 20-fold greater than the rates for all children undergoing anesthesia or sedation for all procedures (Table 1). Although PH remains a challenging disease without a cure, significant advances have been made over the last decade in the understanding of PAH, resulting in expanded therapeutic options and improvement in disease prognosis and survival.1,2 Consequently, an increasing number of these patients are presenting to the cardiac catheterization laboratory, non-cardiac operating rooms (OR) and other venues for procedures requiring anesthesia and sedation. Intraoperative management has extensively been discussed, however, there is little written about the postoperative disposition of these patients. In this article, the focus will be on PAH as it is the most prevalent form of PH in children,9 differing much in its clinical profile and treatment from PH due to left heart disease. We have attempted to gather evidence for a risk stratification strategy, thus allowing practitioners to make a decision on the post-anesthetic disposition of these patients.

Classifications of PAH
Classification of PAH severity in the anesthesiology literature is typically based on the ratio of mean pulmonary artery pressure to mean systemic blood pressure (mPAP/mSAP) or systolic PAP to systolic systemic blood pressure (sPAP/sSAP). Expressed as percentages, subsystemic PAH is < 70%, systemic PAH 70-100% and suprasystemic PAH > 100%.  sPAP and mPAP are obtained through Doppler echocardiography in the absence of cardiac catheterization data. This ratio is used as one indicator of higher risk in pediatric PAH if mPAP/mSAP > 0.75 by catheterization.2 It has been found in the adult population to be a prognostic indicator too.

While cardiac catheterization is currently the gold standard for diagnosis and ongoing evaluation of PAH, the ease of Doppler echocardiographic data acquisition and its non-invasive nature (the majority of studies can be done without an anesthetic) has made it a routine tool for screening and serial assessments of PH related parameters including the identification of congenital cardiac abnormalities.3 However, echocardiography has inherent limitations. Some patients with severe PAH have trivial or no TR jet or the Doppler pattern is incomplete, resulting in underestimation of disease severity.1 Assessment using the pulmonary regurgitant flow also has its own limitations. Other measures such as RV function, RV hypertrophy and septal bowing also provide important clues to the severity of PAH. It is important to note that one preoperative Doppler echocardiography report is only one criterion at one point in time in the assessment of a complex disease.

Determining risk factors for adverse post-anesthetic events
The preliminary step for determining post-anesthetic disposition is an assessment of the patient’s overall risk for adverse postoperative events. This overall risk is composed of the patient’s baseline risk conferred by the disease state of PAH and additional comorbidities and the incremental risks imposed by the procedure and the anesthetic.  

The relevant factors for risk stratification of the patient with PAH are summarized in Table 2. These factors have been compiled from a review of the current literature where referenced and from commonly accepted precepts in clinical management supported by the adult literature.

Patient risk factors
The patient’s total baseline risk is composed of the risk from the PAH disease status and the patient’s relevant comorbidities.

PAH disease severity
PAH disease severity correlates with increased perioperative morbidity and mortality. Four relevant publications were found describing complications in pediatric patients with PAH.

Carmosino et al found that complications were directly correlated with PAH severity based on the above mPAP/mSAP criteria, and patients with baseline suprasystemic PAH were at the highest risk for pulmonary hypertensive crisis and death with all major complications occurring during cardiac catheterization procedures as compared to other anesthetizing sites, excluding the cardiac OR.4 Taylor et al found a correlation between major complications (cardiac massage and death) and tricuspid regurgitation (TR) jet > 4 m/s (calculated RVSP > 64 mmHg), presence of symptoms such as syncope or dizziness, and idiopathic PAH.5 Williams and colleagues, however, found no correlation between PAH disease severity and increased rate of complications in all procedures when using the sPAP/sSAP criteria described above or the pulmonary vascular resistance index (PVRI) criteria when it was available.6 Zuckerman et al did not find a correlation between rate of complications in pediatric patients for cardiac catheterization with mPAP, PVRI nor cardiac index (CI), but the authors did find a correlation with elevated mean right atrial pressure (RAP) measurements.7 Van der Griend et al analyzed the postoperative mortality in 101,885 pediatric patients and found that 5 of 10 anesthetic-related deaths were in patients with PH: two patients for surgically inserted intravenous lines, two for cardiac catheterizations and one during arterial line placement for cardiac surgery. One patient was described as having severe PH, another as having intermittent suprasystemic PAPs during cardiac catheterization, and no report of PH severity was available in the other three patients. The cardiac arrests occurred on induction, during the procedure and in the post-anesthetic care unit (PACU), thus covering the entire perioperative period.8

The discrepancy of these findings could be partly attributed to the retrospective nature of all the studies and to the study time period; the studies by Williams and Zuckerman include patients from more recent years. Another reason could be that the criteria for evaluating disease severity were not uniform.

Disease severity assessment in pediatric PAH is actually difficult, and no consensus exists.9  The criteria developed for adult PAH do not translate adequately into the pediatric population.3,10 Currently, risk stratification is assessed by various measures on a continuum as “lower risk” and “higher risk”. Published determinants for risk stratification for PAH in pediatric cardiology are: 1) echocardiographic findings: RV enlargement, RV dysfunction and presence of pericardial effusion, 2) symptomatology: functional capacity, history of syncope, progression of symptoms, and clinical evidence of RV failure, 3) growth, 4) Beta Natriuretic Peptide (BNP) or N-terminal proBNP (NT-proBNP) levels, and 5) hemodynamic catheterization indices: PVRI, CI, RAP and mPAP/mSAP.2 These factors help determine disease severity and guide therapy as the risk increases. The number of therapeutic agents and the stability of a patient’s therapy reflect the severity of disease.11 It is obvious that the complexity of the above and the high stakes of PAH in perioperative risk demand the involvement of the patient’s primary cardiologist in the pre-procedure discussion and planning and post-procedural disposition and care.

Patients with suspected or newly diagnosed PAH require a high degree of precaution. Right ventricular function is a key determinant of disease status and outcome. Children with PAH commonly present with minor symptoms and retain good functional status in the absence of RV failure despite high PAP.3 Children in this category are at higher risk for acute pulmonary hypertensive crisis due to increased vasoreactivity in the early stages of PAH, especially if still untreated or have not yet achieved a stable optimum therapeutic regimen. This group stands in contrast to the children with chronic PAH with greater disease progression who are more likely to have a hypertrophied RV and are at increased risk for RV ischemia and failure from relative coronary hypoperfusion. Obviously some overlap is present. There is some evidence that idiopathic forms of PAH may carry a higher perioperative risk in comparison to PAH due to congenital heart disease.5

Patient comorbidities
 The presence of comorbidities decreasing cardiopulmonary or airway reserve increase the patient’s baseline risk of cardiac arrest and hypertensive crisis: e.g. significant sleep-disordered breathing, reactive airway disease, chronic lung disease, history of chronic aspiration, obesity, sickle cell disease, neuromuscular disease, coronary artery abnormalities, congenital/acquired cardiac disease. Other major organ dysfunction increases the general risk of complications.8,13

Procedure and anesthetic related risk factors
Incremental risks imposed by the procedure as well as the anesthetic are associated with the same factors that would challenge the clinical status of any child with magnified detrimental effects in patients with PAH. The risk relates to the effects on PVR and RV perfusion and function.

Procedural factors
These include surgeries involving major fluid shifts, significant systemic inflammatory response, extreme sympathetic nervous system responses, compromise of lung vessels and significant risk of embolization of air, carbon dioxide, and/or surgical materials such as in abdominal, thoracic, cranial, and major orthopedic surgeries. Procedures involving the airway or head and neck with effects on airway or respiratory function present an increased risk due to the critical impact of ventilation and oxygenation on PVR. Emergent procedures, increased procedural length, procedures associated with difficult pain control and significant post-procedural complications place patients at a higher risk requiring close postoperative observation.

Procedures in the catheterization lab have been shown to be associated with a higher risk of cardiac arrest than in the non-cardiac OR.4 Interventional procedures incur the highest risk.12,15 Contrast injection for angiography has been associated with hemodynamic instability. Cardiac arrests in PAH patients have occurred during surgical placement of central venous access in the non-cardiac OR.8 Probably these patients have more severe disease as the central access was likely for continuous intravenous PAH vasodilator therapy.

Anesthetic factors
Anesthetic factors that increase risk for any child yet are more detrimental in this patient population are: young age (< 1 year old),13-16 ASA status 3 and above,13 difficult airway, use of large amounts of opioids and sedatives, intraoperative hemodynamic instability and ventilation and oxygenation issues.

Determining post-anesthetic disposition
The ideal post-anesthetic management and disposition actively minimizes the risk of pulmonary hypertensive crisis, coronary hypoperfusion, RV ischemia/failure and cardiac arrest in the face of acute procedure-specific and post-anesthetic challenges. These favorable conditions must be maintained until the patient has returned to either baseline risk status, or is consistently at a lower risk level at which point the patient’s care can be de-escalated and his/her disposition reassessed. This initial place could be the intensive care unit (ICU), the step down ICU or the PACU. The choice could be institution-dependent as levels of care and nursing protocols vary. The length of observation is currently unknown, and intuitively it would depend on the time necessary for stabilization of acute post-procedural effects and recovery from anesthetic drugs. When is the patient ready? No studies have directly addressed readiness for de-escalation of care. Cardiac arrests have occurred in the evening, many hours after an anesthetic. Pain control, sedation, airway and respiratory problems are usually the dynamic issues preventing patients from post-anesthetic de-escalation. Christensen and colleagues demonstrated that almost 50% of cardiac arrests in the PACU are respiratory related.17 Respiratory depression and airway obstruction that is seen after administration of anesthetic agents and re-dosing of opioids to treat pain lead to hypoventilation, desaturations and increased risk of adverse events. If there is a need for prolonged pain management with opioids post-discharge, does the risk of adverse events increase during sleep after an oral dose of opioids? When are the patient’s abilities to self-rescue restored? Do the residual anesthetic drugs and opioids change the tone of upper airway muscles during sleep on the first post-procedural night? Do they change sleep patterns? These are valid questions in search of answers. Data could be extrapolated from the 2006 ASA guidelines for OSA (obstructive sleep apnea)—observation for a median of three hours longer than the non-OSA patient for discharge from the PACU, when the patient is no longer thought to be in danger of post-anesthetic respiratory depression,18 with the caveat that the new 2014 guidelines no longer offer recommendations on this particular point.19  Also, the presence of nausea and vomiting would weigh against de-escalation of care as adequate hydration and ability to continue oral vasodilator therapy is critical. When in doubt, err on the side of safety.

Results of survey on current practices
Thirty institutions with congenital heart programs were informally surveyed via email or personal communication. The questions were as follows: (1) Does your institution have formal policies or guidelines for the post-anesthetic care of pediatric patients with pulmonary arterial hypertension (PAH) regarding place and length of observation, including non-cardiac procedures? …If so, would your group mind sharing the main points? (2) Is there an “every patient with PAH gets admitted overnight” policy? To the ICU? Step down? Ward? Do some patients go home after minor procedures and uneventful anesthetics? (3) Or is it more case-by-case? And provider dependent?

Of the surveyed institutions 5/30 (17%) were private practice, and 25/30 (83%) were academic.  1/30 (3.3%) did not reply to our survey. 23/29 (79%) institutions made decisions on a case-by-case basis. One institution was in the process of developing guidelines. 6/29 (21%) had guidelines. The guidelines of 4/6 institutions solely address the patients with moderate to severe pulmonary hypertension. The common practices of these institutions are based on a combination of the following factors: 1) severity, 2) etiology –PAH secondary to congenital heart disease, chronic lung disease of prematurity and congenital diaphragmatic hernia being considered less fragile than primary PAH, and 3) procedure complexity - with specific mention of airway procedure or intubation for case as being admitted to ICU. Most institutions with guidelines recommend sending patients to PICU directly, bypassing the PACU. If PACU stay is decided prior to transfer to PICU, a detailed sign-out is emphasized. For length of observation, the guidelines only make mention of overnight stay. 

No institution specifically reported to have a “blanket policy” for admission of every patient with PAH, although two institutions report that almost all of their patients with PAH stay in house post-anesthetic, with most of them admitted to the PICU.

Summary of recommended pre-operative preparation
Development of institution-specific guidelines with joint input from anesthesiology, cardiology and ICU is highly recommended for the perioperative management of these patients. The minimization of unnecessary variability in the management of high-risk patients has been linked to improved overall patient safety. This protocol should address pre-procedural communication among the involved team members with inclusion of the surgeon or proceduralist. The multidisciplinary discussion would cover: 1) the risk vs. benefit of the anesthetic, 2) the anticipated overall perioperative risk level with plans for coordination of risk-appropriate safeguards as indicated (e.g. ECMO for high-risk cases), 3) the preoperative optimization of the patient’s status with minimization of risk at all 3 levels (patient’s PAH disease status and comorbid conditions, anesthetic and procedural-related factors), 4) post-anesthetic disposition and 5) logistics and implementation.

Allocation of preoperative time for planning and optimization is imperative but often overlooked. Some patients will need a preoperative re-evaluation of PAH disease status with revision of PAH treatment along with optimization of other significant comorbid conditions. To minimize perioperative procedural and anesthetic risk, consider the following:

  1. Continuation of all pulmonary vasodilator therapy without interruption,
  2. schedule for an early time slot with avoidance of prolonged fasting,
  3. confirmation of ICU bed availability if indicated,
  4. adequate preoperative preparation (i.e., logistics/equipment/material) to eliminate unnecessary interruptions during the anesthetic or surgical conduct of the procedure,
  5. assignment of experienced staff, proceduralists and PAH-knowledgeable anesthesia providers on the case, and
  6. a courtesy communication with the cardiology and the ICU service about this patient on the day of the procedure.

For those patients suspected of having PAH who present without prior cardiology work up for elective surgery, a discussion with the surgeon or proceduralist should be held regarding rescheduling the case until an appropriate work up is completed.

Proposal for post-anesthetic disposition

  1. Patients with any of the higher risk factors are admitted directly to the PICU for post- procedural observation with detailed hand-off given to PICU staff.
  2. Patients whose only risk determinants come from the lower risk status for all three categories and who have had an uneventful procedure and anesthetic could be recovered in the PACU.  Consider monitoring for a longer period than routine (extra three hours after meeting discharge criteria?). These patients are candidates for discharge from the hospital only after a completely uneventful PACU course after the effects of sedatives have worn off (if used) and no opioids/sedatives are needed after discharge.
  3. All other patients not covered in the above two groups, who have determinants that are in between risk categories, are candidates for PACU recovery after an uneven tful intraoperative course. A comprehensive hand-off in PACU is needed with emphasis on the early recognition of signs and symptoms of impending acute pulmonary hypertensive crisis and RV strain/ischemia with immediate notification of the primary anesthesiologist should they occur. After an uneventful course and adequate length of observation in the PACU, at the discretion of the primary team, the patient could be transferred to the step down ICU or ward as appropriate (this is institution specific as the level of monitoring and care can vary widely in these settings). Any escalation of care deserves consideration for ICU admission.

Conclusion
As the medical management of pediatric PAH continues to improve, the perianesthetic care of these patients must evolve with it. Even in this high risk patient group, an indiscriminative overly-conservative approach for every patient with this diagnosis is unlikely to be in their best interest. The national trend in current practices gathered from the survey seems to reflect this evolution of care. As this paradigm shifts, evidence-based guidelines are needed to guide these children’s perianesthetic care. With so much remaining unknown, the pediatric cardiac anesthesiology community must take the lead role in this important area of research.

References

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