| Abstract: Introduction
Harrahill proposed a simple technique for measuring intra-abdominal pressure (IAP) using the elevated column of a urinary catheter drainage tube after instillation of 100mls of saline into the bladder (1) this technique has not been validated. This study assessed the clinical validity of the original and modified Harrahill technique.
Method
A prospective study of 30 patients undergoing abdominal surgery returning to a University Hospital ICU was undertaken. Patients without urinary catheters or following paediatric of gynaecological surgery were excluded. Three techniques were assessed; the gold standard modified Kron technique (2,3), the Harrahill technique and a modified Harrahill technique. The Harrahill technique was performed on supine patients following drainage of bladder and instillation of 100mls of saline through the injecting port with the urinary tubing held vertically at a 90-degree angle to the patient’s pelvis. The level of the meniscus in the urinary catheter was measured and converted to mmHg where 1mmHg = 1.36 cmH2O. The modified Harrahill technique was similar, omitting fluid instillation into the bladder. Three consecutive IAP measurements were performed for each patient and the mean measured. Raised IAP was defined as ³15mmHg. The status of ventilation, muscle relaxation, urine specific gravity and body mass index (BMI) were recorded.
Statistical analysis was undertaken using a Bland and Altman technique. Positive (PPV) and negative predictive values (NPV) were calculated.
Results
There were 21 males and 9 females, mean age 60.0 ± 20.5 following emergency surgery in 23/30, of which 66.6% had gastrointestinal surgery. 15 patients were ventilated, 14 receiving muscle relaxants. The mean specific gravity of the urine was 1.018 ±0.005. The mean BMI was 26.5. 15 patients had IAP’s greater or equal to 15mmHG. The Harrahill technique had a PPV for elevated IAP of 0.92 and a negative predictive value of 0.82, compared to the modified Harrahill techniques PPV of 0.59 and NPV of 0.75. The mean difference between the Kron and Harrahill technique was –2.6 (CI – 4.8215 to –0.393). The modified Harrahill technique mean difference was 1.509 (CI – 0.699 to 3.717).
Conclusion
The Kron technique remains the most reliable technique for IAP measurement but the Harrahill technique could be substituted when necessary. The modified Harrahill technique is unreliable.
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