Negotiating the Unanticipated Costs of Success

Development of many of the less invasive surgical techniques has facilitated shorter hospital stays, less postoperative pain, and, in many cases, fewer overall complications. The growth of these less invasive surgical techniques has occurred in parallel with development of shorter-acting anesthetic drugs, more extensive but less invasive monitoring equipment, and perhaps better anesthetic technique, allowing patients to recover cardiovascular, pulmonary, and vital protective functions more quickly and predictably. But unlike the introduction of new drugs or medical devices, the development and implementation of novel surgical and anesthetic procedures carries no regulatory requirement for proof of efficacy or safety.1 At times in the past, medical interventions that were believed to provide unequivocal benefit have been found to have significant downside after large randomized trials produced data demonstrating these interventions to be complicated, ineffective, or blatantly harmful (i.e., administration of high-dose, untitrated perioperative β blockers to a broad noncardiac surgical population, high-dose chemotherapy with stem cell transplant for metastatic breast cancer, or suppression of premature ventricular contractions after acute myocardial infarction).2–4 Frequently, new processes that should afford better outcomes are marketed to the public, without any information about which patient(s) might actually benefit. As anesthesiologists responsible for the physiologic welfare of the surgical patient, we in turn must craft techniques that we believe will minimize complications, sometimes in conflict with what has been previously believed. For example, in the development of anesthetic techniques for laparoscopic surgery, we have had to come to terms with significantly decreased, but acceptable, urine output during the period of pneumoperitoneum.5,6 Currently, prostate cancer accounts for one-third of all cancer diagnoses among U.S. men, and of the 192,000 cases diagnosed in 2009, the majority involved localized disease. By 2025, the number of individuals diagnosed through prostate-specific antigen screening is expected to double.7 With these projections, a growing number of patients will face a variety of treatment choices, including surveillance, radiation, and radical prostatectomy. Although the surgical approach carries the theoretical advantage of potential cure, it has also been associated with considerable medical and urologic risk. For that reason, surgery has been traditionally restricted to those with longer life expectancy, absence of medical comorbidity, and overall personal preference for surgery.8 Over the past decade, the advent and rapid adoption of robotic-assisted minimally invasive surgery has begun to shift the perceived balance point in the risk-benefit calculation among both surgeons and patients. Robotic-assisted laparoscopic radical prostatectomy (RALRP) was first performed in 2000, and by 2007 RALRP accounted for 60% of all prostatectomy surgery performed in the United States. With increasing patient demand, more extensive investment in robotic equipment, and a greater number of surgeons gaining skill in the technique, we can expect a dramatic increase in the number of patients undergoing robotic procedures in the next decade. One consequence of this growth may be the inclusion of an increasing number of medically complex patients as surgical candidates. Compared to open radical prostatectomy, RALRP is performed through very small incisions. It has postulated advantages of shorter hospital stay, lesser blood loss and risk of blood transfusion, along with a lower overall incidence of perioperative complications. There remains controversy about long-term outcomes, because in most studies, patients undergoing conventional laparoscopic or RALRP procedures have been healthier than those undergoing open procedures.9,10 Although the influence of peritoneal insufflation on cardiovascular and ventilatory parameters has been studied previously,11–13 imposition of the extreme Trendelenburg position required for exposure of the pelvic contents during RALRP has not been examined in this context. Although this steep head-down position during peritoneal insufflation appears to be relatively well tolerated in a healthy population, based on the large number of patients who have undergone the procedure without complications,7 the physiologic impact of this position, pneumoperitoneum, and surgical duration remain poorly understood. Furthermore, the clinical consequences in very young and elderly patients or in patients with impaired cardiopulmonary reserve are unknown. Thus, as the surgical population continues to age, with attendant increases in cardiopulmonary disease as well as obesity, an understanding of the physiologic changes we might expect in the course of RALRP will be of increasing importance. In this issue of Anesthesia & Analgesia, Lestar et al.14 have taken the first step in examining the physiologic changes related to the positioning required to facilitate robotic-assisted laparoscopic surgery. They report hemodynamic, echocardiographic, gas exchange, and ventilation-perfusion distribution measurements in 16 ASA physical status 1 to 2 patients undergoing RALRP in a 45-degree Trendelenburg position.14 Compared to baseline supine measurements, the institution of 12-mm Hg pneumoperitoneum and 45-degree head-down positioning resulted in decreased lung compliance by 40% along with >2-fold increases in central venous, mean pulmonary artery, and pulmonary capillary occlusion wedge pressures. On the other hand, echocardiographic dimensions, stroke volume, cardiac output, mixed venous oxygen saturation, and ventilation-perfusion distribution did not differ significantly from baseline measurements, and oxygenation actually improved. Overall, the clinical implications of these physiologic findings are not clear. Elevation in left ventricular end-diastolic pressure threatens subendocardial bloodflow due to decreases in coronary perfusion pressure. If the transmural pressure gradient were to increase 2- to 3-fold, we could expect adverse sequelae in marginally compensated patients, including those with preexisting cardiomyopathy, critical coronary artery or valvular stenosis or ventricular enlargement. However, the extent to which these increased filling pressures reflect actual increases in transmural pressure, extrinsic compression on the vessels and cardiac chambers, or a combination of both cannot be determined by the methods used by Lestar and colleagues.14 Under ordinary circumstances, an increased transmural pressure should translate into increased chamber size, but the 2-dimensional echocardiographic imaging suggested no significant change in dimensions. The increase in Emax implies impairment of diastolic function, although the modest increase in calculated pressure gradient again raises the question of clinical relevance. Utilitization of more sensitive imaging technology, including 3-dimensional echocardiography, may yield more reliable information on the clinical impact of these maneuvers during RALRP. Improvement in oxygenation after institution of pneumoperitoneum and minimal decline after Trendelenburg positioning, despite significant deterioration in lung compliance and avoidance of positive end-expiratory pressure, is not easily explained. Possible reasons for this improvement include management issues (avoidance of alveolar derecruitment after tracheal intubation), patient-specific issues (normal body habitus, healthy physical status), and chance (type 1 error). The extent to which any of these factors contributed, however, is unclear. In any case, expectation of a similarly benign course in an individual clearly burdened with obesity or cardiopulmonary disease would not be warranted based upon these findings. However, given the usual nature of medical practice, we should expect that our future patients undergoing RALRP will be more fragile than those in whom the procedure is performed today, even though our understanding of the physiologic consequences and overall surgical risk in such a population is far from complete. Accurate characterization of both risks and benefits of the procedure are needed for informed clinical decision-making, and these characterizations should be based upon both large outcome-oriented trials and thorough, careful analysis of hemodynamic and respiratory findings as they relate to a broad spectrum of patients, including those who are asymptomatic but at greater perceived risk of clinical deterioration. At this time, we cannot reliably identify many of these higher risk patients. For example, mild pulmonary hypertension (pulmonary artery systolic pressure 40 to 60 mm Hg) or cardiomyopathy (left ventricular ejection fraction 35%–45%) often creates few symptoms, but might render patients at increased hemodynamic risks from these procedures. Thus, we cannot be reliably assured by data from Lestar and colleagues that every asymptomatic patient is a candidate for this surgical technique. Should physically inactive patients scheduled to undergo RALRP receive more extensive preoperative cardiac evaluation based upon these findings (i.e., should we consider this “high risk” surgery)? In the absence of data from larger outcome trials to inform our practice, this decision must be made on an individual basis. Perhaps some thought should be given to the creation of a registry, at least to provide some early warning about perioperative issues, should they arise. Currently, a prospective multicenter trial comparing RALRP to open retropubic prostatectomy is underway in Sweden.15 Whether or not this trial will assist in patient selection, identification of useful preoperative screening tools or anesthetic protocols remains to be determined. DISCLOSURES Name: Rachel Eshima Mckay, MD. Contribution: This author helped write the manuscript and perform manuscript revision. Attestation: Rachel Eshima Mckay approved the final manuscript. Name: Marc Rozner, PhD, MD. Contribution: This author helped write the manuscript and perform manuscript revision. Attestation: Marc Rozner approved the final manuscript. This manuscript was handled by: Sorin J. Brull, MD.