Introduction
Surgical patient preparation is everything that happens between a planned surgery and the first skin incision: fasting, emptying the bladder, positioning, hair removal, skin antisepsis, eye protection, grounding for electrosurgery and keeping the patient warm. The veterinary technician carries out most of these steps. Good preparation lowers the risk of surgical site infection, burns, corneal ulcers and hypothermia, and it gives the surgeon a clean, wide field to work in. This guide walks through the sequence from induction to incision, the clip areas and scrub patterns you need to know, and how each surgical position changes breathing and blood flow.
Key facts
- Clip after anesthetic induction and outside the surgical suite, at least 15 cm (6 in) around the incision in small animals and 25 cm in large animals.8
- Use clippers with a number 40 blade, never a razor. Razor shaving has been linked to a 10-fold increase in surgical infections.48
- Scrub from the incision site outward toward the hair, and never bring a used sponge back toward the center. Repeat at least three times for each solution.5
- Chlorhexidine and povidone-iodine both need about 2 minutes of contact for full effect. Chlorhexidine stays active in organic material; iodophors are inactivated by it.678
- Prepared skin is very clean but never sterile.5
- Apply corneal lubricant after induction and every 2 to 4 hours.9
- Do not express the bladder of a pyometra patient; pressure may rupture the uterus.3
- Never use an electric heating pad under an anesthetized patient; use a circulating warm water pad or forced warm air.8
How the VTNE tests this
- Prepare the patient for a surgical procedure (Domain 2, Surgical Nursing, Task C).16
- Choose the correct clip area, clipper technique and scrub pattern for a named procedure, such as an ovariohysterectomy or a limb surgery.
- Compare antiseptics: contact time, residual activity, effect of organic debris, and which to avoid near eyes or mucous membranes.
- Pick the position for a procedure and predict its effect on ventilation or blood pressure, then name the technician action that reduces the risk.
- Recognize safety steps: eye lubrication, grounding pad placement, safe warming, and when bladder expression is contraindicated.
Core concepts
Why hair comes off
Hair carries large numbers of microorganisms, stops the skin from being cleaned properly, and causes a foreign body reaction if it gets into the wound.8 Every hair removal method causes some skin trauma. Clipping is efficient, relatively atraumatic and has the lowest infection rates. A razor leaves little stubble but makes many small cuts in the skin (microlacerations) and should not be used. Depilatory creams work poorly on animals and often cause skin reactions, especially in cats.8
Clip on the day of surgery, after induction, outside the surgical suite.8 Clip wide: extra margin at each end lets the surgeon lengthen the incision without reaching unclipped skin in an emergency.4 If the paw or hoof is not needed, cover it instead of clipping it, because feet carry more resident bacteria and are hard to clean.8
How antiseptics differ
An antiseptic kills or inhibits microorganisms on living tissue. Three measures matter: immediate action (organisms removed or killed within about 3 minutes), persistent action (preventing regrowth for up to 6 hours) and residual action (a cumulative effect over days of use).8 Patient skin prep usually pairs a detergent scrub with alcohol, then finishes with a more concentrated antiseptic solution, often in an alcohol base.5
| Feature | Chlorhexidine gluconate | Povidone-iodine (iodophor) | Isopropyl or ethyl alcohol |
|---|---|---|---|
| Contact time | Works within 30 seconds; 2 minutes advised for maximum kill | At least 2 minutes | Acts until it evaporates |
| Residual activity | At least 6 hours (binds keratin) | Persistent for several hours; no residual action | Some |
| Organic debris (blood, pus) | Stays active | Inactivated | Not listed |
| Main cautions | Irritating to the eye; ototoxic; neurotoxic on brain or meninges | Contact dermatitis; absorbed from mucous membranes and open wounds; stains | Not used on mucous membranes or open wounds |
Sources: Ontario Veterinary College, Veterinary Surgery Online; WCVM VSAC Lab 5.5678
How position changes breathing and perfusion
General anesthesia reduces functional residual capacity (FRC), the volume of air left in the lungs at the end of a normal breath. In one study of dogs, anesthesia reduced FRC by a mean of 16.9% in dorsal recumbency compared with awake dogs in the same position.10 Lost muscle tone lets the abdominal organs push the diaphragm toward the head. A head-down position (Trendelenburg, made by tilting the table so the head is lowered12), abdominal surgery and laparoscopy with insufflation all add to this shift and to intra-abdominal pressure, which lowers chest compliance and lung volume.10
Position also affects blood return to the heart. When a pregnant cat is placed in dorsal recumbency for a cesarean section, the enlarged uterus may compress the caudal vena cava and aorta and reduce venous return, which the authors list among possible contributors to low blood pressure during cesarean surgery.11 The technician's job is to watch SpO2, end-tidal CO2 and blood pressure closely after any change in position, and to tell the veterinarian early when they drift.
| Procedure | Usual position | Clip area and notes |
|---|---|---|
| Ovariohysterectomy (spay) | Dorsal recumbency | Xiphoid to pubis, and laterally beyond the mammary chains |
| Canine castration, cystotomy, gastrointestinal foreign body | Dorsal recumbency | Ventral abdomen with wide margins; palpate and express a full bladder first (unless contraindicated) |
| Perineal hernia repair | Perineal: sternal, hindquarters raised over the padded table edge, tail lifted forward over the back | Perineum around the anus; sites near mucous membranes get aqueous (non-alcohol) antiseptic |
| Limb surgery | As the surgeon directs for the approach; the limb is often hung from an IV pole for clipping and prep | Clip 10 to 15 cm above and below the site, around the whole limb; cover the paw with tape and elastic wrap if it is not needed |
| Any small animal site | As the surgeon directs | At least 15 cm (6 in) around the incision; 25 cm in large animals |
Sources: Veterinary Surgery Online (Clipping, Patient Positioning, Skin Preparation); WCVM VSAC Lab 5; Sangmanee et al. 2025; Kim et al. 2023.2458181921
Procedure or technique
Before induction
- Confirm the patient, procedure and site, and work through the practice's anesthesia and surgery checklist. AAHA recommends a checklist to prevent critical oversights before, during and after surgery.9
- Confirm fasting. Adult animals are generally fasted up to 12 hours to reduce the risk of vomiting, regurgitation and aspiration pneumonia. Young animals can become hypoglycemic, so their fast is shortened. Water stays available.1
- Walk the dog just before surgery so it can urinate and defecate.1
After induction, in the prep area
- Apply corneal lubricant to both eyes right after induction. Repeat every 2 to 4 hours.9 Anesthesia lowers tear production, and the drop can last up to 24 hours.15
- Start active warming as soon as possible. Heat loss is fastest in the first stage of anesthesia, partly because core heat redistributes to the body surface.14
- If the bladder is full before an abdominal procedure, express it: palpate with one or two hands and apply steady pressure, collecting urine in a bowl or towel. It rarely empties fully in one try.3 Skip this in a pyometra patient.
- Wearing a lab coat over scrubs, clip with a number 40 blade held in a pencil grip. Clip with the hair first to remove bulk, then against the hair for a close clip.4
- Vacuum the clipped hair from the patient, table and padding. Remove the lab coat, then put on exam gloves, cap and mask.4
- Perform the initial scrub. At OVC this is two soap scrubs with a chlorhexidine scrub brush for a total of 5 minutes of contact. Lather well; you do not need to scrub hard the whole time if the skin is clean.5
- Wipe off the suds, then alternate alcohol and the antiseptic solution from the center outward, at least three times each. Discard a sponge once it touches hair.5
- Cover the prepared site with a sterile towel or drape for the move to the operating room.5
In the operating room
- Move the patient on a trolley. Place a circulating warm water pad between the patient and the table.8
- If monopolar electrosurgery will be used, place the dispersive (grounding) pad with full, even contact (see Safety).
- Position the patient so the surgeon has full access to the site. Secure it with ropes, sandbags, tape or vacuum positioning bags.28
- The gowned and gloved surgeon performs the final prep with sterile sponge forceps and gauze dipped in antiseptic, using the same center-outward pattern, then drapes.5
Flowchart
Figure 1 shows the order of work. The order matters: clipping comes after induction and outside the operating room, the dirty steps (clipping and vacuuming) come before the clean ones, and the final sterile prep is done by a gowned and gloved person only after the patient is positioned in the operating room.5817
Species differences
- Dogs: walk before anesthesia so they void; express the bladder under anesthesia only when it is full and there is no contraindication.18
- Cats and toy-breed dogs: AAHA lists all cats and very small or toy-breed dogs as being at higher anesthetic risk, partly because they are more prone to hypothermia.9 Start warming early. Avoid depilatory creams, which often cause skin reactions in cats.8
- Large animals: clip at least 25 cm around the incision instead of 15 cm.8 In horses, anesthesia in lateral recumbency reduced FRC by almost 50% compared with the standing awake horse, so large patients lose more lung volume when recumbent.10
- Pediatric patients: shorten the fast, because young animals can become hypoglycemic.1
Calculation
Worked example: how long is the patient covered by eye lubricant? A dog is induced at 08:10 and the lubricant is applied at 08:15. Your protocol repeats it every 3 hours (within the AAHA 2 to 4 hour window).9 The procedure is expected to end at 13:00.
Next doses: 08:15 + 3 h = 11:15; 11:15 + 3 h = 14:15.
The surgery ends at 13:00, before 14:15, so one repeat dose at 11:15 is needed during the procedure. Record each application time on the anesthetic record so the next person knows when the following dose is due.
Safety, legal and client education
- Grounding pad. In monopolar electrosurgery, current returns through a wide dispersive electrode at low current density. Place it over an even, well-perfused muscle mass near the field, away from where fluid can pool. Avoid scars, hair, bony prominences, metal implants, tattoos and pressure points. Partial detachment concentrates current and burns the skin under the pad.13
- Warming. Inadvertent perianesthetic hypothermia occurs in up to 85 to 89% of dogs under inhalant anesthesia. Cold IV fluids, cold dry gases and cold prep solutions add to heat loss.14 Use circulating warm water pads, forced warm air and warmed fluids; never an electric heating pad, whose erratic temperature can cause severe burns.8
- Eyes and ears. Keep chlorhexidine out of eyes and ear canals: it irritates the eye and is ototoxic.6 Near mucous membranes, use an aqueous (non-alcohol) antiseptic.5
- Client education. Explain the fasting instructions and why they matter (aspiration risk). Tell owners to expect a clipped area wider than the incision; an even clip and a tidy incision line are the quality markers the client sees.20
Common mistakes and exam traps
- Clipping before induction or inside the surgical suite. Both are wrong; clip after induction, in the prep area.8
- Scrubbing from the edge toward the incision, or reusing a sponge after it touches hair.5
- Calling prepared skin "sterile". It is clean, not sterile.5
- Choosing povidone-iodine for a field contaminated with blood or pus; iodophors are inactivated by organic material.8
- Expressing the bladder of a pyometra patient.3
- Assuming a head-down tilt is harmless. It pushes abdominal organs against the diaphragm and reduces lung volume.10
Quick review
- Fast adults up to 12 hours; shorten the fast for young animals; water stays available.
- Walk dogs to void; express a full bladder before abdominal surgery, but never in pyometra.
- Lubricate the eyes after induction and every 2 to 4 hours.
- Clip after induction, outside the OR, with a #40 blade; no razors.
- Clip margin: at least 15 cm in small animals, 25 cm in large animals.
- Clip with the hair, then against it; vacuum all loose hair.
- Scrub center to periphery, never back; at least three passes per solution.
- Chlorhexidine and povidone-iodine: about 2 minutes contact.
- Chlorhexidine works in organic debris; iodophors do not.
- Dorsal recumbency is the most common surgical position; anesthesia lowers FRC, and a pregnant uterus can compress the caudal vena cava.
- Perineal position: sternal, hindquarters raised over the padded table edge, tail forward.
- Grounding pad: flat, well-perfused muscle, full contact, no hair or bony points.