Resuscitation with hyperoncotic human albumin following cardiovascular surgery
The advantages and risks of resuscitation with isooncotic albumin are potentially of even greater significance when volume expansion is achieved with hyperosmolar albumin [45, 54]. Prospective studies performed in various ICU settings have indicated that the volume-expanding effect of hyperosmolar albumin is twice that of 5% human albumin [45, 55] with results demonstrating a less positive fluid balance in patients resuscitated with hyperoncotic albumin [43, 45, 55].
Similar investigations in patients following cardiac surgery had not been performed until recently. In a prospective, sequential, open-label study by Wigmore, et al., authors aimed to compare the effects of FBT using 20% albumin (200mL bolus) versus crystalloid (500mL bolus) on fluid balance, hemodynamic markers and clinical course in the ICU in a cohort of post-cardiac patients (n=100) [20]. FBT was given in response to clinical signs of hemodynamic instability or in response to a low cardiac index (<2.2 L/min/m2) [20]. Patients in the albumin group were noted to have a less positive fluid balance in the first 24 hours (p=0.001), and required fewer FBT compared to those in the crystalloid group (p<0.001) [20]. Further, individuals in the concentrated albumin group required vasopressors for a shorter period of time and had a shorter length of ICU stay compared to their study counterparts (p =0.048) [20]. Despite these findings, there was no appreciable difference between the two groups in cardiac output (CO), mean arterial pressure (MAP) or central venous pressure (CVP) following the first fluid bolus [20]. Furthermore, this study showed no difference in mortality between study groups [20].
In a smaller prospective observational study by Cutuli, et al., authors investigated the effects of 20% albumin boluses on cardiac index (CI) and MAP in a cohort of twenty post-cardiac patients [24]. Patients included in this single center analysis were those admitted to the ICU following an on-pump cardiovascular surgery, who were given a bolus of 20% albumin within the first twelve hours of ICU admission [24]. The clinical indications of when to administer FBT was similar to the study conducted by Wigmore, et al [20, 24]. After the administration of FBT, 55% of the study cohort demonstrated an appreciable increase in MAP (>10%) [24]. This effect dissipated in nearly half of the responders within 30 minutes of their FBT, returning to their MAP baseline [24]. Interestingly, the impact FBT had on CI for the study cohort varied from these results [24]. While only 25% of participants had a significant increase in CI (>15%) immediately after receiving hyperoncotic albumin, 25% of the cohort demonstrated a delayed increase in CO, one that persisted beyond 30 minutes [24]. One explanation to these incongruent findings is the notion that the effect of hyperoncotic albumin peaks at 30 minutes after administration [24].
The parameters used when FBTs were given in these two analyses highlights the individualized practice of fluid resuscitation in the perioperative setting [12]. In a retrospective, non-interventional descriptive study performed at a tertiary care medical center, Torbic, et al. aimed to describe the prescribing practice of concentrated albumin within the ICUs at their institution (n=2,066) [12]. During the study period, the majority of the hyperoncotic albumin administered within their institution occurred in the cardiovascular ICU (CVICU) in patients following cardiac surgery (n=1509, 73%) [12]. In this analysis, authors describe the medical conditions that may benefit from the administration of human albumin, where the use of hyperosmotic albumin is potentially superior to isooncotic albumin [12]. The evidence-based indications include post-subarachnoid hemorrhage vasospasm, large-volume paracentesis, spontaneous bacterial peritonitis and hepatorenal syndrome [12, 56-58]. Based on these indications, authors discussed the hyperosmolar albumin administration practices in the CVICU, emphasizing the use of hypertonic albumin in response to hypotension, low urine output or perceived hypovolemia to be inappropriate and unsupported by the current literature [12]. From a health care utilization standpoint, the authors also discuss the enormous cost associated with the use of concentrated human albumin [12].
In an effort to identify best practice and further delineate the appropriateness of the routine administration of concentrated albumin, Rabin, et al., studied the effect of restrictive albumin practices following cardiac surgery over a thirteen month period [52]. During this retrospective analysis, authors investigated the use of hyperoncotic albumin in patients admitted to the CVICU following cardiac surgery before and after institutional guidelines limiting the use of albumin administration (n=1,401) [52]. Outcomes of interest included the amount of albumin use, number of blood transfusions, ventilator free days, mortality and length of hospital stay [52]. During the first nine months of the study period, there were no restrictions in albumin administration [52]. Following the implementation of the restrictive guidelines, the use of albumin was limited to patients that required more than three liters of crystalloids 24 hours after surgery [52]. Following the initiation of restrictive guidelines, authors found the amount of hyperoncotic albumin given decreased from a mean of 280 monthly doses to a mean of 101 monthly doses (p <0.001) [52]. This decrease in 180 albumin doses equated to more than $45,000 saved per month [52]. Authors found no difference in average length of stay, mortality, ventilator free days or number of transfusions required between the two study period [52].