Abstract
Transplantation of adult-sized kidneys to pediatric patients weighing less than 10 kg is a challenge to both surgical and anesthetic management. For survival of the graft, a large-size kidney graft transferred to a pediatric patient needs extraphysiological cardiac output to compensate for adequate renal blood flow. We report here a boy weighing 8.4 kg who received transplantation of a kidney donated by his 56.4-kg mother. Since monitoring of the central venous pressure was not accurate enough and Swan–Ganz catheterization was not feasible in this patient for monitoring the fluid status and cardiac function, we used transesophageal echocardiography to guide intravascular volume expansion and to titrate inotropic support during the surgery. It was demonstrated to be a useful tool for optimization of renal perfusion in this scenario. The transplanted graft served its function well.
Keywords
central venous pressure; echocardiography, transesophageal; kidney transplantation: pediatric; perioperative care: fluid management;
1. Introduction
Transplantation of adult-sized kidneys to small pediatric recipients remains a challenge to both surgical and anesthetic management, largely because of the body mass discrepancy between the donor and the recipient. Augmentation of cardiac output is therefore necessary after graft reperfusion in order to early restore graft function and prevent graft loss due to vascular thrombosis.1, 2 Aggressive intravascular volume supplementation is conventionally used to avoid hypoperfusion of the freshly transplanted kidney.3, 4 Nonetheless, fluid overload, manifested by lung edema, is exceptional risky, especially in chronically dialysed children.5 Hemodynamic optimization with intravascular volume expansion and titration of inotropic agents at this critical period, precisely monitoring both heart function and fluid status, is of great importance.
We report here a 20-month-old boy, weighing 8.4 kg, with end-stage renal disease (ESRD) who underwent transplantation of a kidney donated by his mother, who weighed 56.4 kg. Intraoperative transesophageal echocardiography (TEE) was used to guide fluid optimization and hemodynamic management. TEE was demonstrated to be a useful tool in this case.
2. Case report
A 20-month-old boy weighing 8.4 kg with bilateral hydronephrosis diagnosed prenatally due to a posterior urethral valve, which progressed to ESRD, was scheduled for pre-emptive (dialysis-naïve) living-related transplantation of a kidney donated by his mother. Preoperative transthoracic echocardiography revealed normal cardiac function with a left ventricle end-diastolic dimension of 2.70 cm and a left ventricle ejection fraction of 74.3%. The body weight of the graft donor was 54.6 kg, and the weight of donated graft was 270 g.
After premedication with 0.1 mg intravenous atropine, inhalational general anesthesia was induced with sevoflurane, and tracheal intubation was facilitated with 2 mg intravenous cisatracurium. Anesthesia was maintained with sevoflurane in O2 and intravenous fentanyl, while neuromuscular blockade was made possible by cisatracurium.
Continuous arterial blood pressure (ABP) and central venous pressure (CVP) were monitored via the right radial artery (a 24-G intra-arterial catheter) and right internal jugular vein (a pediatric three-way central venous catheter, 20G/22G/22G), respectively. Preoperative hemodynamic readings were ABP 85/45 mmHg, heart rate 125 beats/min, and CVP 3 mmHg.
A specially designed TEE probe for pediatric patients (9T; GE Medical Systems Ultrasound, Wauwatosa, WI, USA) was used for intraoperative echocardiography. Before surgery, the TEE imaging of heart showed that all four chambers were normal in size and there was good left ventricular contractility. Intravascular volume expansion was made possible by infusion of crystalloid (2.5% dextrose in 0.45% saline at 60 mL/h) and 10% hydroxyethyl starch (HAES-Steril 10%; Fresenius Kabi, Friedburg, Germany) to attain a targeted CVP of around 10–12 mmHg. TEE was also performed with great effort to avoid right ventricular distension and abnormal regional wall motion.
The artery and vein of the transplanted kidney were anastomosed end-to-side to the recipient’s right common iliac artery and right common iliac vein, respectively, using running suture techniques. Before reperfusion of the donated kidney, dopamine 6 μg/kg/min was empirically infused to augment cardiac output. Intravenous methylprednisolone 80 mg was given as an immunosuppressive agent. Intravenous sodium bicarbonate and calcium chloride were also slowly introduced intravenously to prevent acidosis and hyperkalemia caused by ischemia–reperfusion injury of the donated graft. Nevertheless, the ABP and the CVP still dropped from 123/73 to 69/41 mmHg and from 12 to 5 mmHg, respectively, after vascular unclamping.
Acute hypovolemia resulting from reperfusion was thought of, as evidenced on the TEE monitoring by a well-contracting heart with poorly filled chambers (Fig. 1A). Intravascular volume was expanded immediately by blood products under the guidance of TEE, gradually increasing the left ventricle end-diastolic volume from 8.77 cm3 to 13.66 cm3 (Fig. 1B). Dopamine was increased to 10 μg/kg/min to further augment the cardiac output for optimization of graft perfusion. Furosemide 10 mg was also given empirically to strengthen the renal blood flow and facilitate diuresis.
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Once the grafted kidney was producing clear urine, the graft ureter was implanted to the bladder using an extravesical technique. The transplanted kidney was settled in the right retroperitoneal space, and the abdominal wound was closed using an absorbable mesh to avoid compression of the graft.
The operation lasted for 3 hours from graft reperfusion until the end of the surgery. The total blood products transfused were 2 units of packed red blood cells, 1 unit of fresh frozen plasma, and 2 units of platelet concentrate to maintain augmentation of cardiac output (Table 1).
The boy was transferred to the pediatric intensive care unit. Rigorous intravascular volume was managed to achieve a targeted systolic blood pressure of more than 80 mmHg, a CVP between 6 and 10 mmHg and a urine output of more than 1 mL/kg/h; transfusion of red blood cells was mandatory if the hemoglobin level was less than 10 g/dL so as to keep the grafted kidney well perfused. The follow-up chest X-ray did not reveal fluid overload or pulmonary atelectasis. The endotracheal tube was smoothly removed on the next day. The boy was discharged on Day 7 postoperatively with good renal function, and his serum creatinine levels at 3 months and 6 months were 0.7 mg/dL and 0.6 mg/dL, respectively.
3. Discussion
Renal transplantation is a better treatment than dialysis for ESRD, especially in the pediatric population. Living-related renal transplantation not only shortens the waiting period, but also exempts the patient from the need for dialysis. Thus, renal transplantation can be timely and pre-emptively performed to avoid dialysis-associated co-morbidities, and, above all, better long-term outcomes can be provided than with cadaveric renal transplantion.6, 7
Nevertheless, the disparity in body size between an adult donor and a small pediatric recipient complicates the surgical techniques and anesthetic management.3, 8 Optimization of intravascular volume to maintain adequate renal blood flow of the transplanted graft is crucial during surgery. Inadequate aortic blood flow may result in graft hypoperfusion, which causes acute tubular necrosis, early vascular thrombosis, and primary dysfunction of the graft. Any of these complications alone or in combination will jeopardize the long-term survival of the implanted kidney.4, 9
A single in-situ adult kidney usually receives more than 500 mL/min of blood flow,4 or 3.47 mL/min/cm3 of renal volume in a healthy women.10 Even though the cardiac output of the pediatric recipient doubles, it is still not enough to fully perfuse the implanted kidney. Consequently, the transplanted kidney usually atrophies due to relative hypoperfusion, reducing its mass by 26% some 4–6 months after surgery.4 Thus, it can be seen that strengthening of cardiac function and augmentation of intravascular volume are crucial to compensate the deficit caused by increased cardiac output demand driven by an adult-sized kidney graft, especially as that cardiovascular insufficiency is usually the forerunner of ESRD.5
TEE is a useful tool for real-time cardiac function surveillance. It gives more reliable information than CVP during rapid expansion of intravascular volume and helps to differentiate whether the acute ventricular distension is being caused by rapid fluid supplementation or congestive heart failure. Aggressive volume expansion with either crystalloid or colloid solution before vascular unclamping is mostly suggested, using a targeted CVP level to attain adequate graft perfusion. However, differences in CVP levels, ranged from 2 to 18 mmHg, have existed in successful cases.3, 4, 6, 9, 11, 12 In smaller pediatric cases, supraphysiological fluid supplementation complicates lung edema and prolonges ventilator support.3, 4 We suggest that the use of TEE to monitor cardiac performance combined with CVP readings to guide the expansion of intravascular volume not only makes the surveillance more precise, but also helps more quickly to differentiate the causes of post-reperfusion hypotension from whatever origin, the use of CVP alone being inferior for this.
Although the hemodynamic readings were best optimized before graft reperfusion, the boy still suffered from an abrupt decrease of ABP from 123/73 to 69/41 mmHg. Post-reperfusion hypotension (amounting to nearly 50% in this case) is a hemodynamic character of ischemia–reperfusion injury that can occur from both metabolic acidosis and release of vasoactive mediators to cause myocardial stunning, low systemic vascular resistance, and relative central hypovolemia.13 Therefore, intravascular fluid supplementation, vasoconstrictors, and inotropic agents can be used to support circulatory insufficiency. However, vasoconstrictors are not much favored because of their potential compromise of renal blood flow, especially in cases of hypovolemia. Rapid fluid challenge is also problematic and can easily exacerbate pre-existing acute congestive heart failure. With the aid of intraoperative TEE in our case, causes of post-reperfusion hypotension were rapidly differentiated (Fig. 1) and thus enabled us to treat the disorder promptly.
In summary, adult-sized kidney transplantation in a small pediatric recipient requires intense perioperative fluid management to ensure good graft survival. Discrepancy in size between a living adult donor and a small pediatric recipient contributes to acute hemodynamic changes after graft reperfusion. Since TEE can provide precise, real-time information about volume status, myocardial contractility and other procedure-related events,14 it should be considered as a standard monitor modality to help obtain precise hemodynamic information and guide fluid management during pediatric renal transplantation.
Acknowledgments
This article is attributed to the Department of Anesthesiology, National Taiwan University Hospital; support was provided solely from institutional and/or departmental sources.