Материал: Oxford American Handbook of Urology ( PDFDrive )

COMPLICATIONS OF SURGERY IN GENERAL: DVT AND PE 577

Tests

•CXR may be normal or show linear atelectasis, dilated pulmonary artery, and small pleural effusion.

•ECG may be normal or show tachycardia, right bundle branch block, and inverted T waves in V1–V4 (evidence of right ventricular strain). The classic SI, QIII, TIII pattern is rare.

•Arterial blood gases show low PO2 and low PCO2.

•Imaging: Computed tomography pulmonary angiogram (CTPA) has superior specificity and sensitivity compared with that of ventilationperfusion (VQ) radioisotope scan.

•Spiral CT: A negative CTPA rules out a PE with similar accuracy to a normal isotope lung scan or a negative pulmonary angiogram.

Treatment of established DVT

•Below-knee DVT: above-knee thromboembolic stockings (AK-TEDs), if no peripheral arterial disease (enquire for claudication and check pulses) + unfractionated heparin (UFH) 5000 u SC 12 hourly

•Above-knee DVT: start a low molecular-weight heparin (LMWH) and warfarin, and stop heparin when INR is between 2 and 3. Continue treatment for 6 weeks for postsurgical patients; it should be lifelong if there is an underlying cause (e.g., malignancy).

•LMWH

Treatment of established PE

Fixed-dose, subcutaneous (SC) LMWH seems to be as effective as adjust- ed-dose, intravenous (IV) UFH for the treatment of PE found in conjunction with a symptomatic DVT.3 Rates of hemorrhage are similar with both forms of heparin treatment.

Start warfarin at the same time and stop heparin when INR is 2–3. Continue warfarin for 3 months.

578 CHAPTER 16 Urological surgery and equipment

Box 16.1 Options for prevention of VTE

•Early mobilization.

•Above-knee thromboembolic stockings (AK-TEDs) (provide graduated, static compression of the calves, thereby reducing venous stasis). More effective than below-knee TEDS for DVT prevention.1

•Subcutaneous heparin (low-dose unfractionated heparin [LDUH] or low molecular weight heparin [LMWH]). In unfractionated preparations, heparin molecules are polymerized, with molecular

weights from 5000 to 30,000 daltons. LMWH is depolymerized, with a molecular weight of 4000–5000 daltons.

•Intermittent pneumatic calf compression (IPC) boots, which are placed around the calves, are intermittently inflated and deflated, thereby increasing the flow of blood in calf veins.2

•For patients undergoing major urological surgery (radical prostatectomy, cystectomy, nephrectomy), AK-TEDS with IPC intraoperatively, followed by SC heparin (LDUH or LMWH) should be used. For TURP, many urologists use a combination of AK-TEDS and IPCs; relatively few use SC heparin.3

1 Howard A, et al. (2004). Randomized clinical trial of low molecular weight heparin with thighlength or knee-length antiembolism stockings for patients undergoing surgery. BJS 91:842–847. 2 Soderdahl DW, Henderson SR, Hansberry KL (1997). A comparison of intermittent pneumatic compression of the calf and whole leg in preventing deep venous thrombosis in urological surgery. J Urol 157:1774–1776.

3 Golash A, Collins PW, Kynaston HG, Jenkins BJ (2002). Venous thromboembolic prophylaxis for transurethral prostatectomy: practice among British urologists. J Roy Soc Med 95:130–131.

Further reading

British Thoracic Society guidelines for management of suspected acute pulmonary embolism (2003) Thorax 58:1–14.

Kelly J, Rudd A, Lewis RR, Hunt BJ (2002). Plasma D-dimers in the diagnosis of venous thromboembolism. Arch Intern Med 162:747–756.

Kruip MJH, Slob MJ, Schijen JH, et al. (2002). Use of a clinical decision rule in combination with D-dimer concentration in diagnostic workup of patients with suspected pulmonary embolism. Arch Intern Med 162:1631–1635.

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580 CHAPTER 16 Urological surgery and equipment

Fluid balance and management of shock in the surgical patient

Daily fluid requirement

This can be calculated according to patient weight:

•For the first 10 kg: 100 mL/kg per 24 hours (= 1000 mL)

•For the next 10 kg (i.e., 10–20 kg): 50 mL/kg per 24 hours (= 500 mL)

•For every kg above 20 kg: 20 mL/kg per 24 hours (= 1000 mL for a patient weighing 70 kg).

Thus, for every 24 hours, a 70 kg adult will require 1000 mL for their first 10 kg of weight, plus 500 mL for their next 10 kg of weight, and 1000 mL for their last 50 kg of weight = total 24-hour fluid requirement, 2500 mL.

Daily sodium requirement is ~100 mmol, and for potassium, 770 mmol. Thus, a standard 24-hour fluid regimen is 2 L of 5% dextrose + 1 L of normal saline (equivalent to about 150 mmol Na+), with 20 mmol K+ for every liter of infused fluid.

Fluid losses from drains or nasogastric aspirate are similar in composition to plasma and should be replaced principally with normal saline.

Shock due to blood loss

Inadequate organ perfusion and tissue oxygenation occur. The causes are hypovolemia, cardiogenic, septic, anaphylactic, and neurogenic. The most common cause in the surgical patient is hypovolemia due to blood and other fluid loss. Hemorrhage is an acute loss of circulating blood volume.

Hemorrhagic shock may be classified as follows:

•Class I: up to 750 mL of blood loss (15% of blood volume); normal pulse rate (PR), respiratory rate (RR), blood pressure (BP), urine output, and mental status

•Class II: 750–1500 mL (15–30% of blood volume); PR >100; decreased pulse pressure due to increased diastolic pressure; RR 20–30; urinary output 20–30 mL/hr

•Class III: 1500–2000 mL (30–40% of blood volume); PR >120; decreased BP and pulse pressure due to decreased systolic pressure; RR 30–40; urine output 5–15 mL/hr; confusion

•Class IV: >2000 mL (>40% of blood volume); PR >140; decreased pulse pressure and BP; RR >35; urine output <5 mL/hr; cold, clammy skin

Management

•Remember ABC (Airway, Breathing, Circulation): 100% oxygen to improve tissue oxygenation

•ECG, cardiac monitor, pulse oximetry

•Insert two short and wide IV cannulae in the antecubital fossa (e.g., 16G). A central venous line may be required.

•Infuse 1 L of warm Hartmann’s solution or, if severe hemorrhage, then start a colloid instead. Aim for a urinary output of 0.5 mL/kg/hr and maintenance of blood pressure.

FLUID BALANCE AND MANAGEMENT OF SHOCK 581

•Check complete blood count (CBC), coagulation screen, and cardiac enzymes.

•Cross-match 6 units of blood.

•Obtain arterial blood gases (ABG) to assess oxygenation and pH.

Obvious and excessive blood loss may be seen from drains, but drains can also block, so assume there is covert bleeding if there is a tachycardia (and low blood pressure).

If this regimen fails to stabilize pulse and blood pressure, return the patient to the operating room for exploratory surgery.

Further reading

American College of Surgeons Committee on Trauma (1999). Advanced Trauma Life Support for Doctors—Student Course Manual, 6th Edition.