Percutaneous nephrolithotomy
About 2% of the population have a urinary tract stone at any one time. Many people are asymptomatic, but pain is the commonest symptom. Preoperative investigations must identify the position, size, and number of stones that may be present in the renal parenchyma and/or the collecting system. Extracorporeal shock wave lithotripsy began in the 1980s and introduced a minimally invasive method of treating stones. However, this method has been found to have limitations in obese patients and those with an abnormal renal anatomy where it is difficult to put the stone in the focal zone of the wave generator. In these cases, surgical intervention is required.
1 Perform a preoperative assessment for percutaneous renal tract surgery
2 Understand patient positioning during these procedures
3 Anticipate and manage specific post-operative complications related to percutaneous nephrolithotomy (PNL).
2A03; 2A07
A 37-year-old man presented to his GP with intermittent severe left flank pain and haematuria. Investigations by the urology team found him to have a 3.0 cm calculus in the left kidney. He was seen in pre-admission clinic for work-up for an elective PNL.
He is fit and well, with no previous medical history, is not on any medications, and has no allergies.
◆ FBC
◆ U&E
◆ Urinalysis.
His results show Hb 141 g/L, WCC 8.5 × 109/L, Plt 289 × 109, urea 4.5 mmol/L, Cr 76 micromoles/L, Na+ 140 mmol/L, and K+ 4.3 mmol/L. Despite his haematuria, his ultrasound is normal. His renal function is also normal. Urinalysis shows blood ++, nitrite ++, and leucocytes ++.
Send off a urine sample for culture and sensitivity (C&S), as it indicates this gentleman has a urine infection. The microbiology must be followed up preoperatively and appropriate antibiotics started, before the patient comes in for the procedure. The urine will be re-tested on the day of admission.
The gentleman was advised to visit his GP 2 days later and be prescribed a suitable antibiotic from the C&S sample taken at the pre-admission clinic. However, due to work commitments, he had only managed to visit his GP 2 days before coming in for surgery. The GP had started him on a course of ciprofloxacin. On admission, his urinalysis was similar to the previous result.
The surgeon and the anaesthetist discussed the case and thought it best that the procedure be cancelled. He would be rescheduled after he had completed the course of antibiotics.
The patient was annoyed and argued against this decision—he felt fine and had made considerable plans to cover his business whilst in hospital and recovering from his procedure.
Further discussion ensued, and a review of his observations made—the patient was systemically well; he had a normal WCC and was apyrexial.
The decision was made to continue with the procedure.
◆ Renal function (drug metabolism considerations)
◆ Positioning
◆ Sepsis
◆ Bleeding
◆ The possibility of a prolonged procedure: stones have differing chemical make-up and require variable lengths of time for their destruction by ultrasonics or laser
◆ A change/delay of procedure: occasionally, at cystoscopy, it may be noted that there is an overt infection present, and the PNL procedure will not be perfomed. Instead, a nephrostomy will be performed and a post-operative course of appropriate antibiotic prescribed
◆ Crowded theatre: the procedure involves a urologist, a radiologist, and a radiographer. Equipment includes an X-ray C-arm with screens and a fibreoptic scope stack.
The patient should be intubated, preferably using a reinforced tube. The procedure involves two positions. First, the patient will go into a lithotomy position for the urologist to perform cystoscopy and insert a ureteric balloon catheter to be used for the retrograde study.
The patient will then be put into a prone position. The radiologist will perform access through the flank to the kidney, under radiological guidance. Initially, a needle is inserted, followed by dilators, then followed by a telescope sleeve inserted into the calyx of the kidney. It is through this access sleeve that the urologist is able to pass a scope and the ultrasound device or laser that will break up the stone.
◆ Consider midazolam 1–3 mg
◆ Propofol 2–4 mg/kg
◆ Remifentanil to be run as an infusion
◆ Atracurium 0.5 mg/mL
◆ Ondansetron 4 mg
◆ Morphine 10 mg
◆ Ephedrine and metaraminol.
Each anaesthestist should check with the local antimicrobial policy, but generally gentamicin 2 mg/kg is used if the renal function is normal. If there is significant renal impairment, then the alternative is ciprofloxacin 400 mg which should be given prior to the start of cystoscopy.
For the prone position, take care with regard to pressure areas, i.e. ankles, knees, male genitalia, breasts, and face. Use a pillow under the upper chest area, pelvis, and ankles. Ensure there is no pressure on the eyes and there is adequate padding where contact occurs. There are many types of face protectors available. The arms should be placed on boards in front of the head. Ensure the shoulders are positioned, so there is no stretch on the neck or brachial plexus.
◆ An active patient warming device, such as a Bair Hugger®, is imperative: this procedure may be prolonged, and there is often a lot of irrigation fluid that may soak through to the sheets
◆ Temperature probe
◆ The patient should be wearing thromboembolism deterrent (TED) stockings, and a mechanical calf compression device should be applied.
◆ Analgesia:
• Morphine PCA, with a loading dose prescribed
• Regular paracetamol
• For young patients with normal renal function: consider regular NSAID
◆ Antiemetics: ondansetron and cyclizine
◆ VTE prophylaxis 6 hours post-operatively
◆ Buscopan® 10 mg, as required, for urinary tract spasm.
The urologist has almost finished the process of stone breakdown. So far, the procedure has been uneventful. However, the patient begins to require more regular doses of pressor and inotropic support with metaraminol and ephedrine. The BP remains no more than 70/40, despite these drugs and turning off the remifentanil infusion.
The most likely cause is septic shock:
◆ Give colloid boluses, and start a vasopressor infusion
◆ Give antibiotics, as per local hospital guideline for severe urinary sepsis.
Within 15 min, the procedure is complete, but the patient is now on an infusion of metaraminol (0.5 mg/mL) running at 45 mL/hour. The anaesthetist has managed to put in a radial arterial line. His vital signs are: HR 85 bpm, BP 90/45 mmHg, SpO2 98% on FiO2 0.5. An ABG has been sent for analysis, demonstrating: H+ 54 nmol/L, pCO2 5.1 kPa, pO2 13.5 kPa, HCO3– 24.5 mmol/L, BE –8.2, and lactate 3.1 mmol/L.
Refer to the critical care consultant, and arrange admission to the ICU. This patient has severe urosepsis and should be admitted for continued ventilation, vasopressor support, and monitoring. Insert a CVC, and change the vasopressor support to a noradrenaline infusion.
The patient was stabilized in theatre and then transferred to the ICU. He was kept intubated and ventilated for 2 days, and he required vasopressor support for 3 days. His renal function deteriorated and reached a plateau of urea 15 and Cr 198, but he did not require haemofiltration. He was discharged from hospital 5 days after leaving the ICU.
Summary
PNL was established in the 1970s and is considered to be the best technique for removing large and multiple stones in the inferior calyx. A 2007 review of >1000 cases showed the incidence of post-operative fever is 21–32% and that of septicaemia of 0.3–4.7%. A careful selection of patients is recommended to reduce complications. PNL is contraindicated in patients with a UTI or pyonephrosis.