Renal Function and the Abdominal Compartment Syndrome

1. Renal Function and the Abdominal Compartment Syndrome AW Kirkpatrick CD MD MHSc FRCSC FACS Calgary, Alberta, Canada

2. Scott D’Amores early gastroenterology practice

3. Historical • 1873 – Wendt of Germany said it all.. • Measured IAP through the rectum • “The higher the abdominal pressure the less the secretion of urine” Schein M, In: The Abdominal Compartment Syndrome”, Ivatury R et al (in press)

4. Further recognition of this over the years • Bradley 1947 • Studies to determine the effects of g-suits • “It is well established that increased intra-abdominal pressure alters renal function” • GFR & renal plasma flow • 25% of baseline with 20 mmHg increase in IAP Wilbur Franks Bradley, J Clin Invest 1947;26:1010-1015

5. Seminal canine studies • Intra-peritoneal inflatable bags • Steady state concentrations of • Para-aminohippuric acid • Inulin • Hemodynamic and renal function determined at • baseline • 20 mmHg • 60 mmHg • After dextran-40 fluid resuscitation Harman PK, Elevated intra-abdominal pressure and renal function., Ann Surg 1982:196:594-597

6. 20 mmHg GFR 21% normal Renal blood flow 23% of normal Cardiac output 83% normal Renal vascular resistance 555% increase Systemic vascular resistance 30% increase Renal/systemic resistance increase 15 times 40 mmHg GFR 3/7 anuric Others GFR and renal blood flow 7% normal Cardiac output 37% normal Renal vascular resistance 1512% increase Renal/systemic resistance increase 9 times Results Harman PK., Ann Surg 1982:196:594-597

7. Resuscitative attempts • Blood volume expansion corrected cardiac output • Did not restore renal blood flood nor GFR above 25% of normal • Ureteric stents did not influence renal response to raised IAP • Stents were not protective Harman PK., Ann Surg 1982:196:594-597

8. A local phenomenon • “.. the impairment in renal function produced by increased intra-abdominal pressure is a local phenomenon caused by direct renal compression and is not related to cardiac output” Harman., Ann Surg;1982:196:594-597

9. The Abdominal Compartment Syndrome • post-operative renal failure described • 4 observed – died • 10 thereafter had IAP pressures measured • 3 (10-15 mmHg) • normal post-operative course • 7 (IAP > 30 mmHg) • 4 explored • immediate diuresis • 3 observed • all died Kron et al, Ann Surg 1984;199:28-30

10. 1984 • “If intra-abdominal pressure rises above 25 mmHg in the early postoperative period and is associated with oliguria and normal blood pressure and cardiac index, the patient should undergo re-exploration and decompression of the abdomen.” • “An acute elevation of intra-abdominal pressure in the early postoperative period causes a marked impairment of renal function independent of blood pressure or cardiac output.” Kron et al, Ann Surg 1984;199:28-30

11. Ascitic fluid pressure and renal function • If IAP > 25 cmH20 • Paracentesis was performed to decrease IAP by min 10 cmH20 • Mean IAP Δ’d 33 to 19 cmH20 • Significant decreases • Total peripheral resistance • Creatinine, BUN, • Significant increase • Cardiac index • Stroke index • Left & right ventricular stroke work • Creatinine clearance • Osmolar clearance Savino JA, Manipulation of ascitic fluid pressure in cirrhotics to optimize hemodynamics and renal function Ann Surg 1988;208:504-511.

12. Discussion • “So what??” • …”little clinical application except in showing the noxious effect of intra-abdominal pressure.” • “..it is on this (other) circumstance that we must stay focused” Discussion of; Savino JA., Ann Surg 1988;208:504-511.

13. Association of IAH & renal deterioration after laparotomy • 88 patients prospectively studied after laparotomy • 33% had IAP > 20 mmHg • Increased complications associated with IAH • Death (11X) • Renal dysfunction (12X) • Does not prove causality • IAH preceded renal dysfunction in only 35% of cases Sugrue., Br J Surg 1995;82:235-238

14. IAH as an independent predictor of post-operative renal impairment • 263 ICU patients after abdominal surgery (prospective) • 41% IAP > 18mmHg • 33% renal impairment • Renal impairment independently associated with • Hypotension • Sepsis • Age > 60 • Increased IAP • Dose-dependant • Renal failure doubled with IAP 18  25 mmHg Sugrue M. Arch Surg 1999;134:1082-1085

15. “Treating” the ACS may not help the kidney’s • 49 patients prospectively undergoing a temporary abdominal closure • Variety of indications • Significantly improved • Mean IAP (24 to 14 mmHg) • Lung compliance • No improvement in • Hourly urine output • Serum creatinine worsened • 25% were not successfully decompressed (per IAP) Sugrue J Trauma 1998;45:914-921

16. Creatinine post decompression Sugrue J Trauma1998;45:914-921

17. Implications • Abdominal decompression alone will not reverse the renal sequele of excessive IAP once established

18. Volume loading is not the answer • 1Harman - Seminal canine ACS model • At 40 mmHg, cardiac output was doubled from baseline but GFR and renal blood flow remained 20% of baseline • 2Biancofiore – IAP’s in post-op liver transplant pts • Raised IAP significantly associated with ARF • Despite the fact they were given more IV fluids • 3,4Balogh – multiple trauma patients • Fluid boluses in those at risk may precipitate secondary ACS 1Harman 1982, 2Biancofiore 2003, Balogh 3Am J Surg 2003, 4Arch Surg 2003

19. Can the kidneys be the canary? • Postoperative ARF • “preventable” rather than a “treatable” 1 • 10 mmHg • Threshold for renal deterioration2 1Reddy, J Postgrad Med 2002;48:64-70, 2Harman Ann Surg 1982;196:594-597

20. Probable mechanisms of renal ischemia from increased IAP • Diminished cardiac output • Decreased GFR • But not ARF corrected through simple volume loading of pharmacologic increases in cardiac index • physical compression of renal vasculature • Renal parenchymal compression • Arterial compression • Venous compression • Increased rennin, aldosterone, and antidiuretic hormone Reddy, J Postgrad Med 2002;48:64-70

21. Implications • Changes in IAP have a greater impact upon renal function and urine production than will changes in MAP (factor of 2) • Decrements in renal function, as evidenced by oliguria, are one of the first visible signs of renal failure Malbrain M, Consensus Conference Definitions 2004

22. Filtration gradient PTP GFP • Renal filtration gradient (FG) • Key factors in development of IAP-induced renal failure • FG = GFP – Proximal tubular pressure (PTP) • GFP = MAP - PTP • Under sustained increased IAP, PTP = IAP • Thus GFP = MAP – IAP • Thus, FG = GFP – IAP =(MAP – IAP) – IAP = MAP – IAP 2 IAP Sugrue, Arch Surg 1999

23. Gastric tonometry and renal function • Sugrue 19961 • abnormal pHi • 11 times more likely to have IAP > 20 mmHg • Abnormal pHi marked renal impairment (64X) • Ivatury 19982 • 72% with IAH had abnormal pHi without classic ACS • Decompression improved pHi in 6 • Hameed 20033 • No trial has documented better outcomes with tonometry directed therapy 1Sugrue World J Surg 1996, 2Ivatury J Trauma 1998, 3Hameed Chest 2003

24. What is on the horizon?

25. Ventral hernia repair Why bother with the pressure when you can just get a Doppler???

26. Renal allograft compartment syndrome • 3 cases reports/series • Total of 6 patients diagnosed post-operatively1,2,3 • 4 designated 2° RACS1 • Diagnostic criteria • Poor graft function (urine output) • Doppler/US • Reversed diastolic blood flow • Lack of venous flow • Intra-compartmental/peritoneal pressures have not been measured!!! Resistive index = Psys – Pdiast ______________ Psys Normal is < 0.7 by Doppler US 1Humar Am J Kidney Dis 1996, 1Beasley Transplant Proceed 2003, 1Wiebe Pediatr Radiol 2004

27. Renal Doppler studies? Fascia closed Fascia closed • Flow dynamics in transplanted kidneys may be studied by intra- & post-operative Doppler US • 2 year old girl had living related renal Tx • Post-op anuria • Postop US • Reversal of diastolic flow ininterlobar and segmental arteries • Subsequent absence of venous flow Fascia open Fascia open Wiebe Set al. Pediatr Radiol 2004;34:432-434

28. Their conclusions • “Further study with intra-abdominal pressure measurement from the urinary bladder before, during, and after transplant surgery, coupled with Doppler ultrasound evaluation of the blood flow characteristics of the transplanted kidney, may provide more concrete evidence of this phenomenon” Wiebe Set al. Pediatr Radiol 2004;34:432-434

29. Renal Cortical Ratio of Resistive Indices • Variation in the resistive index of from the renal artery to the cortical vessels in percent • abnormal ratios differentiated normal grafts from acute dysfunction despite confusing creatinine levels and clinical signs • “A flat curve reflects reduced distal vascular function and can be related to a narrowing mainly because of edema” Drudi., Nephron Clin Pract 2004;98:c67-c72

30. Color Power Doppler • CPD superior to regular Doppler in determining the presence or absence of flow at the expense of directional information1,2,3 • Improved ability to identify low-velocity and low-volume flow (or motion)1,2,3 • We regularly use it to rule out pneumothoraces during resuscitation4 1Rubin 1994, 2Lencioni 1996, 3Turetschek 1999, 4Kirkpatrick 2002

31. Power Doppler sonography and raised intra-abdominal pressure • Normal kidney’s studied with color power Doppler (CPD) US during Valsalva • Intra-abdominal pressures from 0 to 100 mmHg, by 20 mmHg increments • CPD provides increased sensitivity for vascular imaging • Mean Doppler intensities of the region of interest (ROI) Takano R, J Clin Ultrasound 2001;29:384-388

32. Power Doppler sonography and raised intra-abdominal pressure • Corroborated through imaging the kidneys before and after paracentesis (1650 ml) in an ascitic patient • IAP Δ’d from 22 – 16 mmHg Takano R, J Clin Ultrasound 2001;29:384-388

33. Color Power Doppler and renal cortical perfusion • US Army Institute of Surgical Research • “urine output, a frequently used resuscitation endpoint, is presumed to represent renal perfusion” • CPD US used to image porcine renal cortices with varying degrees of occlusion • 0, 25, 50, 75, 100% Kuwa., J Trauma 2004;56:618-624

34. Cortical blood flow versus CPD Image intensity

35. Contrast-enhanced ultrasound • Gas-filled microbubbles remain entirely within the vascular tree • Rheology similar to red blood cells • Introduced through a femoral venous line • Excellent correlation (5 = 0.82, p < 0.82) over a 2.5 fold range of flow change Wei K., J Am Coll Cardiol 2001;37:1135-1140

36. 3D US • 106 healthy fetuses evaluated with 3-D CPD to asses fetal renal blood flow • Vascularization index • Flow index • Vascularization-flow index • Normal fetal renal vasculature and blood flow increase with advancement of gestational age Chang., Ultrasound in Med & Biol 2003;29:929-933

37. Is this a potential canary? • 4 – D ultrasound • Fully automated volume calculations combined with transducers that automatically perform fast real-time sweeps of a pre-defined area technology Mehwald., J Am Soc Echocardiogr 2002

38. Conclusions • Kidneys particularly susceptible • Overt dysfunction is too late • Early recognition is likely the key • How is the question?

39. Abdominal Perfusion Pressure (APP) • Retrospective review of 144 surgical ICU patients • Determination of decision thresholds for survival prediction • APP = (MAP – IAP) was superior to; • MAP • IAP • Arterial pH • Base deficit • Lactate • Urine output • Not prospectively validated! Cheatham., J Trauma 2000;49:621-627