*3.2.1 Primary graft dysfunction*

PGD is an acute manifestation of ischemia-reperfusion injury associated with multiple risk factors (donor-derived and related to procurement/preservation and reperfusion) with a peak incidence within the first 72 h after lung transplantation [17, 18]. The severity of PGD is graded based on the presence or absence of diffuse opacities on chest radiograph and the ratio of arterial oxygen pressure to inspired oxygen concentration, i.e., the PaO2/FiO2 ratio. The severity ranges from

*Perioperative Care for Organ Transplant Recipient*

*3.1.7 The use of pulmonary vasodilator therapy*

**3.2 Intensive care unit management**

will include, but are not limited to, the following:

prevent/minimize PGD [15, 16].

(FFP, cryoprecipitate, and platelets).

or as needed depending on clinical status.

the patient is being transported. Gentle Valsalva maneuvers to 30 cm H2O are performed immediately after any disruptions to positive pressure ventilation.

The use of pulmonary vasodilator therapy with INO or epoprostenol (Flolan) is indicated for: (i) hypoxemia during single-lung ventilation, (ii) refractory hypoxemia in severe primary graft dysfunction (PGD), (iii) to prevent/mitigate exacerbations in PHTN and subsequent cardiorespiratory perturbations during induction and pulmonary artery clamping and thus potentially avoiding the institution of CPB [14].

Initial postoperative care for all lung transplant recipients is provided on the intensive care unit. Interventions specific to the care of the lung transplant patient

i.*Ventilator management*: The goal is to provide adequate minute ventilation while preventing oxygen toxicity, barotrauma, and volutrauma. As such, ventilatory parameters are individualized and adjusted to achieve these goals. The aim is early extubation as soon as is clinically feasible. Recommended ventilatory parameters are detailed in Section 3.1.4 above. In particular, the goal is the use the lowest FiO2 to maintain arterial oxygen saturations greater than 91% and a tidal volume based on donor height (where possible) to

ii.*INO weaning protocol*: In single-lung transplants for pulmonary fibrosis, the author [SB] recommends weaning INO first (if used) within the first 6–12 h followed by oxygen and PEEP weaning, as tolerated. In single-lung transplants for COPD, the PEEP is weaned first (to prevent compression of the less compliant lung allograft by the hyperinflated native lung) followed by INO (within 6–12 h) and oxygen weaning, as tolerated. After double-lung transplants, the goal is to wean INO within 24 h. Following extubation, the patient will be instructed in the use of the incentive spirometer and the flut-

ter valve. Early mobilization out of bed to chair is instituted.

iii.*Hemodynamic management and fluid administration protocol*: Due to the propensity of lung allografts to develop pulmonary edema (altered tissue hydrostatic forces, endothelial dysfunction, destruction of lymphatic drainage channels), the goals are to maintain adequate cardiac output; avoid high cardiac output states; wean inotropes rapidly when no longer clinically indicated; use colloid (albumin 5%) rather than crystalloid for volume replacement; medication infusions are concentrated to reduce volume loading; maintain hemoglobin at 10 g/dL with leukocyte-depleted packed red blood cells, CVP 10–12 mmHg, and MAP 65–75 mmHg; and adjust appropriately for urine output above 0.5 mL/kg body weight, SvO2 > 65%, and lactate <2 mmol/L. Additional blood products are given per clinical need

• A cardiac index of 2.2–2.5 is ideal—to minimize the risk of significant pulmonary edema. Specific hemodynamic optimization strategies are detailed in Section 3.1.3 above. Serial lactate levels and SvO2 are measured every 6 h

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grade 0 (absent radiographic infiltrates, any PaO2/FiO2 ratio, extubated patient with/without supplemental oxygen) to grade 3 (radiographic infiltrates present bilaterally or, if single-lung transplant—absent in the native lung, PaO2/FiO2 ratio <200, mechanical ventilation with FiO2 >50% for 48 h, requirement for extracorporeal life support). Severe PGD negatively impacts short-term outcome after lung transplantation (30-day mortality up to 50%) and is also associated with the development of chronic allograft dysfunction, i.e., bronchiolitis obliterans syndrome [15, 19, 20]. Management of PGD is predominantly supportive, i.e., cardiorespiratory support including lung protective ventilation, inhaled pulmonary vasodilator therapy, fluid and transfusion restriction, diuretic therapy, and extracorporeal life support for refractory hypoxemia with/without hemodynamic instability [21, 22].

### *3.2.2 The role of extracorporeal support: ECMO versus CPB in lung transplantation*

In the United States, the rate of CPB use during lung transplantation varies widely. CPB provides hemodynamic stability with the heart in a decompressed state, which affords technical advantages by reducing right heart distension and vascular wall tension/shear stress, especially in the presence of moderate pulmonary hypertension. This facilitates nontraumatic vascular clamping and the performance of tension-free anastomoses. However, several studies have reported worse early postoperative outcomes as compared to off-pump lung transplantation [23, 24]. ECMO as an alternative to CPB provides certain advantages: reduced heparin requirements, reduced systemic inflammatory response, and coagulopathy resulting in less bleeding and lower transfusion requirements. Additionally, ECMO can be continued into the early postoperative period to facilitate allograft recovery while optimizing cardiorespiratory support.

#### **3.3 Immunologic assessment of the lung transplant recipient**

To decrease the immunologic AMR risk posttransplant, high-titer pretransplant DSAs that result in positive complement-dependent cytotoxicity (CDC) crossmatch and cause hyperacute rejection should be effectively avoided or preemptively treated based on acceptable risk defined by the transplant center. However, antibody avoidance results in longer waiting times and death on waiting list. At TUH, about 13% of waitlisted patients have CPRA > 80% (11 out of 83 active patients), but only about 3.5% of transplanted patients have CPRA > 80% (12 out of 345 patients transplanted between 2016 and 2017), showing a disparity in transplantation rates for highly sensitized patients (**Figure 2**). In thoracic transplantation, the use of the virtual crossmatch without a prospective serologic crossmatch became the standard practice. In virtual crossmatch, compatibility between donor and recipient is predicted by comparing the recipient's HLAspecific antibodies with the HLA antigens of the prospective donor. The primary method for antibody identification is the solid-phase single-antigen bead (SAB) assay that provides information about antibody specificities and their relative strengths based on mean fluorescence intensity (MFI) readout. **Figure 3** shows examples of positive and negative virtual crossmatches performed using SAB results that allow evaluation of compatibility between the donor and the recipient. However, there are several limitations to accurate virtual crossmatching based on SAB assay alone, including (1) that SAB assay is prone to detection of the so-called naturally occurring antibodies against denatured/cryptic antigens and that (2) it is not clearly understood at what MFI threshold DSA should be considered as clinically relevant [25].

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**Figure 3.**

**Figure 2.**

*waitlist have CPRA >80%.*

*Perioperative Care for Lung Transplant Recipients: A Multidisciplinary Approach*

*Only 4% of transplanted patients (12/296) have CPRA > 80%, while 13% (11/83) patients on the* 

The precise role of naturally occurring antibodies is not well understood yet, but several studies suggest that such antibodies do not have clinical significance [26–29]. Usually antibodies against cryptic epitope do not result in positive flow cytometric or CDC crossmatches and do not impact clinical posttransplant outcomes. Several reports demonstrated that some antibodies detected in SAB assays may be directed against cryptic epitopes on recombinant HLA proteins created by missing peptides and/or b2-macroglobulin [30]. Other studies estimate that about 20–30% of waitlisted patients have antibodies against denatured antigens [28]. The naturally occurring antibodies can easily be recognized by negative reactions in cell-based crossmatch testing, but thoracic programs rarely have a luxury of performing a prospective crossmatch. Therefore, when/if not recognized as antibodies against denatured antigens, these specificities can deny an organ transplant based on virtual crossmatch. Starting in October 2016, our center began modifying our existing HLA testing protocols to better identify patients with and without pretransplant DSA by using multiple assay platforms, including FlowPRA Screen, phenotypic beads, and the well-established single-antigen beads. We studied 58 consecutive

*Examples of negative (A) and positive (B) virtual crossmatches using results of single-antigen bead assay.*

*DOI: http://dx.doi.org/10.5772/intechopen.85277*

*Perioperative Care for Lung Transplant Recipients: A Multidisciplinary Approach DOI: http://dx.doi.org/10.5772/intechopen.85277*

#### **Figure 2.**

*Perioperative Care for Organ Transplant Recipient*

instability [21, 22].

optimizing cardiorespiratory support.

**3.3 Immunologic assessment of the lung transplant recipient**

grade 0 (absent radiographic infiltrates, any PaO2/FiO2 ratio, extubated patient with/without supplemental oxygen) to grade 3 (radiographic infiltrates present bilaterally or, if single-lung transplant—absent in the native lung, PaO2/FiO2 ratio <200, mechanical ventilation with FiO2 >50% for 48 h, requirement for extracorporeal life support). Severe PGD negatively impacts short-term outcome after lung transplantation (30-day mortality up to 50%) and is also associated with the development of chronic allograft dysfunction, i.e., bronchiolitis obliterans syndrome [15, 19, 20]. Management of PGD is predominantly supportive, i.e., cardiorespiratory support including lung protective ventilation, inhaled pulmonary vasodilator therapy, fluid and transfusion restriction, diuretic therapy, and extracorporeal life support for refractory hypoxemia with/without hemodynamic

*3.2.2 The role of extracorporeal support: ECMO versus CPB in lung transplantation*

In the United States, the rate of CPB use during lung transplantation varies widely. CPB provides hemodynamic stability with the heart in a decompressed state, which affords technical advantages by reducing right heart distension and vascular wall tension/shear stress, especially in the presence of moderate pulmonary hypertension. This facilitates nontraumatic vascular clamping and the performance of tension-free anastomoses. However, several studies have reported worse early postoperative outcomes as compared to off-pump lung transplantation [23, 24]. ECMO as an alternative to CPB provides certain advantages: reduced heparin requirements, reduced systemic inflammatory response, and coagulopathy resulting in less bleeding and lower transfusion requirements. Additionally, ECMO can be continued into the early postoperative period to facilitate allograft recovery while

To decrease the immunologic AMR risk posttransplant, high-titer pretransplant DSAs that result in positive complement-dependent cytotoxicity (CDC) crossmatch and cause hyperacute rejection should be effectively avoided or preemptively treated based on acceptable risk defined by the transplant center. However, antibody avoidance results in longer waiting times and death on waiting list. At TUH, about 13% of waitlisted patients have CPRA > 80% (11 out of 83 active patients), but only about 3.5% of transplanted patients have CPRA > 80% (12 out of 345 patients transplanted between 2016 and 2017), showing a disparity in transplantation rates for highly sensitized patients (**Figure 2**). In thoracic transplantation, the use of the virtual crossmatch without a prospective serologic crossmatch became the standard practice. In virtual crossmatch, compatibility between donor and recipient is predicted by comparing the recipient's HLAspecific antibodies with the HLA antigens of the prospective donor. The primary method for antibody identification is the solid-phase single-antigen bead (SAB) assay that provides information about antibody specificities and their relative strengths based on mean fluorescence intensity (MFI) readout. **Figure 3** shows examples of positive and negative virtual crossmatches performed using SAB results that allow evaluation of compatibility between the donor and the recipient. However, there are several limitations to accurate virtual crossmatching based on SAB assay alone, including (1) that SAB assay is prone to detection of the so-called naturally occurring antibodies against denatured/cryptic antigens and that (2) it is not clearly understood at what MFI threshold DSA should be considered as clini-

**104**

cally relevant [25].

*Only 4% of transplanted patients (12/296) have CPRA > 80%, while 13% (11/83) patients on the waitlist have CPRA >80%.*

#### **Figure 3.**

*Examples of negative (A) and positive (B) virtual crossmatches using results of single-antigen bead assay.*

The precise role of naturally occurring antibodies is not well understood yet, but several studies suggest that such antibodies do not have clinical significance [26–29]. Usually antibodies against cryptic epitope do not result in positive flow cytometric or CDC crossmatches and do not impact clinical posttransplant outcomes. Several reports demonstrated that some antibodies detected in SAB assays may be directed against cryptic epitopes on recombinant HLA proteins created by missing peptides and/or b2-macroglobulin [30]. Other studies estimate that about 20–30% of waitlisted patients have antibodies against denatured antigens [28]. The naturally occurring antibodies can easily be recognized by negative reactions in cell-based crossmatch testing, but thoracic programs rarely have a luxury of performing a prospective crossmatch. Therefore, when/if not recognized as antibodies against denatured antigens, these specificities can deny an organ transplant based on virtual crossmatch. Starting in October 2016, our center began modifying our existing HLA testing protocols to better identify patients with and without pretransplant DSA by using multiple assay platforms, including FlowPRA Screen, phenotypic beads, and the well-established single-antigen beads. We studied 58 consecutive

VXM performed during July–December 2016 for lung candidates with CPRA>10%. Twenty-eight patients had no DSAs or had acceptably weak DSAs; they proceeded to transplant based VXM. All retrospective flow crossmatches were negative. The other 30 patients had positive VXM due to one or more moderate to strong DSAs, and the organ offers were refused. We found that 7 out of 30 (23.3%) VXM were called unacceptably positive due to the presence of antibody against denatured antigens [31]. Among these seven patients, three patients had antibodies against class I denatured antigens (2500–3500 MFI), and four patients had antibodies against class II denatured antigens (2000–14,000 MFI). We also found that by using LSPRA (Phenotypic Bead) and FlowPRA Screen assays along with SAB, we can preemptively recognize antibodies against denatured antigens not to deny organ offers unnecessarily. Instead of performing VXM using only SAB results, we now confirm that donor's antigens are positive by other assays as well (**Figure 3A**). Whenever antibody is detected only by SAB assay, it is considered to be directed against a cryptic epitope and, therefore, to be clinically irrelevant and not able to cause positive flow cytometry crossmatch (**Figure 4A**). DSAs detected by both SAB and phenotypic bead assays are considered as antibody against native HLA antigens (**Figure 4B**). The "true" DSAs undergo evaluation for strength as described below. Using this strategy we successfully transplanted five out of seven patients who were denied offers during July–December 2016 period. Since January 2017, all transplant candidates undergo antibody testing by SAB and LSPRA/FlowPRA Screen assays, so the presence of antibodies against cryptic epitopes can be easily recognized at the time of donor evaluation. This strategy results in reducing the number of unacceptable antigens and reduces percentage

**Figure 4.** *Accuracy of virtual crossmatch can be improved by performing SAB alone with screening assays.*

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*Perioperative Care for Lung Transplant Recipients: A Multidisciplinary Approach*

crossmatches and provides additional opportunities for sensitized patients.

on the urgency for transplant and the strength of antibody specificities.

the risk of complications for patients who did not proceed to transplant.

Induction therapy is determined at the time of listing and is modified for the patient as medically indicated. Induction therapy is administered in the operating room by the

**3.4 Immunosuppressive therapy**

*3.4.1 Induction therapy*

Data from our center show that it is possible to reduce HLA antibody levels temporarily using various protocols, including high dose of IVIG plus Rituxan or five plasma exchanges with or without bortezomib (Velcade) followed by high dose of IVIG. However, if not transplanted during that "window of opportunity," the patient's antibodies invariably rebound and sometimes to the levels even higher than prior to initiation of desensitization. Even for patients with high LAS, who receive a priority during allocation, it is not easy to predict when a "compatible" donor may become available. Instead of implementing desensitization while patients are waiting for the offers, the Toronto Lung Transplant Program has developed a perioperative desensitization protocol-guiding organ allocation and maintenance immunotherapy [34]. At TUH, Toronto's protocol is implemented with some modifications. Highly sensitized patients with antibodies >3000 MFI are additionally tested at 1:16 serum dilution. Antibodies that become <3000 MFI at 1:16 are usually not listed as unacceptable antigens (UA) in UNET, while antibodies >3000 MFI at 1:16 are generally listed as UA. Our center experience is that antibodies <3000 MFI would result in borderline or low-positive flow cytometry crossmatch and can be managed postoperatively as needed. Therefore, if antibody decreases to <3000 at 1:16 dilution, it will result only at most in low-positive flow crossmatch after a single plasma exchange. This additional step allows us to avoid a prospective crossmatch for rapidly declining patients with high CPRA and to accept an offer based on VXM. The treatment usually continues posttransplant with additional 4–5 plasma-exchange sessions, followed by high dose of IVIG and Rituxan as needed. The perioperative desensitization is implemented at the time of transplant decision-making, which reduces unnecessary treatments and

Another important consideration is how to determine a threshold level below which DSA is clinically irrelevant or manageable perioperatively. Mean fluorescence intensity units somewhat indicate the quantity of antibody binding, when serum is pretreated with EDTA to inactivate complement and remove prozone-like inhibition in SAB assay. It is important to note that when untreated serum is used, the correlation between MFI and antibody quantity is very poor [33]. MFI values cannot be reliably measured above 20,000 MFI due to saturation effect, and intercenter studies suggest that the positive cutoff for DSA should be ~1500 MFI [33]. At TUH, antibodies <3000 are considered as weak and can be crossed without perioperative treatment, while antibodies >10,000 strong in general considered as strong and present unacceptably high risk. For patients with CPRA < 50%, UA are listed in UNET based on 3000 MFI cutoff. However, for patients with CPRA >50%, the immunologic management strategy differs depending

of CPRA (the percent of incompatible donors). Our data on relevance of antibodies against cryptic epitopes correlate well with several recent studies, including metaanalysis of 13 cohorts of lung recipients (total 3039 patients) showed that only DSAs that were detected by both SAB and screening assays were associated with CLAD (HR = 2.02, 95% CI = 1.37–2.97, P < 0.001). When DSAs were detected by SAB alone, the association with CLAD was no longer significant [32]. Overall, our experience is that use of SAB assay by itself may unnecessarily deny an organ offer due to the falsepositive reactions and that use of screening assays improves the accuracy of virtual

*DOI: http://dx.doi.org/10.5772/intechopen.85277*

#### *Perioperative Care for Lung Transplant Recipients: A Multidisciplinary Approach DOI: http://dx.doi.org/10.5772/intechopen.85277*

of CPRA (the percent of incompatible donors). Our data on relevance of antibodies against cryptic epitopes correlate well with several recent studies, including metaanalysis of 13 cohorts of lung recipients (total 3039 patients) showed that only DSAs that were detected by both SAB and screening assays were associated with CLAD (HR = 2.02, 95% CI = 1.37–2.97, P < 0.001). When DSAs were detected by SAB alone, the association with CLAD was no longer significant [32]. Overall, our experience is that use of SAB assay by itself may unnecessarily deny an organ offer due to the falsepositive reactions and that use of screening assays improves the accuracy of virtual crossmatches and provides additional opportunities for sensitized patients.

Another important consideration is how to determine a threshold level below which DSA is clinically irrelevant or manageable perioperatively. Mean fluorescence intensity units somewhat indicate the quantity of antibody binding, when serum is pretreated with EDTA to inactivate complement and remove prozone-like inhibition in SAB assay. It is important to note that when untreated serum is used, the correlation between MFI and antibody quantity is very poor [33]. MFI values cannot be reliably measured above 20,000 MFI due to saturation effect, and intercenter studies suggest that the positive cutoff for DSA should be ~1500 MFI [33]. At TUH, antibodies <3000 are considered as weak and can be crossed without perioperative treatment, while antibodies >10,000 strong in general considered as strong and present unacceptably high risk. For patients with CPRA < 50%, UA are listed in UNET based on 3000 MFI cutoff. However, for patients with CPRA >50%, the immunologic management strategy differs depending on the urgency for transplant and the strength of antibody specificities.

Data from our center show that it is possible to reduce HLA antibody levels temporarily using various protocols, including high dose of IVIG plus Rituxan or five plasma exchanges with or without bortezomib (Velcade) followed by high dose of IVIG. However, if not transplanted during that "window of opportunity," the patient's antibodies invariably rebound and sometimes to the levels even higher than prior to initiation of desensitization. Even for patients with high LAS, who receive a priority during allocation, it is not easy to predict when a "compatible" donor may become available. Instead of implementing desensitization while patients are waiting for the offers, the Toronto Lung Transplant Program has developed a perioperative desensitization protocol-guiding organ allocation and maintenance immunotherapy [34]. At TUH, Toronto's protocol is implemented with some modifications. Highly sensitized patients with antibodies >3000 MFI are additionally tested at 1:16 serum dilution. Antibodies that become <3000 MFI at 1:16 are usually not listed as unacceptable antigens (UA) in UNET, while antibodies >3000 MFI at 1:16 are generally listed as UA. Our center experience is that antibodies <3000 MFI would result in borderline or low-positive flow cytometry crossmatch and can be managed postoperatively as needed. Therefore, if antibody decreases to <3000 at 1:16 dilution, it will result only at most in low-positive flow crossmatch after a single plasma exchange. This additional step allows us to avoid a prospective crossmatch for rapidly declining patients with high CPRA and to accept an offer based on VXM. The treatment usually continues posttransplant with additional 4–5 plasma-exchange sessions, followed by high dose of IVIG and Rituxan as needed. The perioperative desensitization is implemented at the time of transplant decision-making, which reduces unnecessary treatments and the risk of complications for patients who did not proceed to transplant.
