An example of the steps involved in spaying a young cat on heat (caterwauling was the reason for spaying) done by me is given as follows:

Record No. 155
Toa Payoh Vets Anaesthesia & Surgery Record
Patient's Name: Mimi
TP Ref: 43711     Date: 13-8-12  Age: 10 m  Wt: 3.8kg*  Temp: 38.6*
Surgical procedure: Spay (on heat)
Type of suture: polysorb  Size:2/0   No. of packets used: One

DOCUMENTATION OF STEPS IN A SPAY OF AN AGGRESSIVE YOUNG CAT ON ESTRUS

1. Restraint. Owner to take the cat out of its carrier bag and put into the crate which has top and side doors. Do NOT put cat with its carrier bag inside the crate as in this case.
Use phone books to corner the cat or lasso if aggressive as it is not possible to sedate just by holding the cat, causing staff to be in danger of being scratched and cat escaping. I used the latter method as the cat was extremely aggressive.

2. Sedation. For a 3.8 kg cat, I injected xylazine 0.15 ml + ketamine 0.6 ml combined IM left back muscles.

3. Pre-op clipping and cleaning was done 2 minutes later.

4. Surgery: A very bloody surgery as the ovaries and uterus were swollen with large blood vessels. More care in ligation is needed in such situations.

For younger vets, do make a larger skin incision of more than 2 cm long to get good exposure. In this case, I started the skin incision 1.5 cm from the umbilical scar, then made a 1.5 cm skin incision.

OVARIES. I hooked out the left ovary at the first attempt. I used 2 artery forceps* to clamp the ovarian ligament and ligate cranial to the lower clamp. I ligate in one direction (5 throws of the knot) and then swung back to ligate in the opposite direction for the ovary. 

Then I used the scalpel to sever the ovarian ligament between the two forceps. I used the forceps to grasp the ovarian stump and inspected to see that it was securely tight before releasing it into the abdomen.  The ligature might slip if the vet just let it slide in, leading to bleeding and death of the cat on heat. In cats not on heat, the ovarian blood vessels are fine and should not bleed should there be a slippage of the ligature.  

UTERINE BODY. I asked my assistant to loosen the front paws and in some cases to elevate the front half of the body (hand under the shoulders) to gain access to the uterine horn (right). Or I would extend my skin incision to 1.8 cm long to access the swollen and vascularised uterine body.

In this case, the uterine body was easily taken out after ligation of the right ovary. I clamped the uterine body with 2 artery forceps. Then I put the 2/0 suture below the lower forceps. I loosen the lower clamp to expose the grooved indentation. I slipped this suture into the groove and ligate 3 times. First in one direction, then in the other direction as for the ovarian ligament ligature. However, I ligate once more.

Normal cats not on heat. I ligate the ovaries and uterus twice only.

SPAY PROCEDURE TIMES
I asked Min to record:
Left ovary hooked out (first attempt)                   8.08pm
Right ovary taken out                                          8.15pm
Uterine body ligated started (with 3 ligatures)      8.21pm
Linea alba muscles stitched started                      8.26pm  (2 simple interrupted sutures)
Skin stitched up                                                  8.29 pm (2 horizontal mattress)

As the cat was full of swollen blood vessels, extra care and time were needed to ensure that there would be no complications of bleeding to death. The left ovary was hooked out at the first attempt and the ovaries were unusually enlarged at around 8 mm x 8 mm x 6 mm (see images). The 0.15 ml xylazine + 0.6 ml ketamine IM injection was slightly insufficient for a 3.8 kg cat, as isoflurane gas at 5% top up was need for 2 minutes.

The first incision must not be delayed and was done 12 minutes after the injection of xylazine and ketamine as I had to clip and saved the coat which would have been done prior to sedation in non-aggressive cats, saving 3 minutes of time, depending on the assistant.

The above report serves as a benchmark for my associate vets. Elevate the op table to be comfortable doing surgery as each vet has his or her own height. If there is proper planning and preparation, a spay of a caterwauling cat can be as fast as 23 minutes.

Much less time of around 15 minutes would do,  if the cat was not caterwauling as the ovarian blood vessels and uterus will be not swollen and bleeding much. Usually I ligate once for each of the ovaries and the uterine body if the cat is not on heat. In this cat, I ligated twice per ovary and thrice per uterine body, adding up to more minutes of spay. I dislike spaying caterwauling cats but in practice, owners bring in the caterwauling cat for spay because of the noise nuisance in HDB flats, affecting the neighbour's sleep, I explained to Dr Daniel. So, they want the cat spayed fast.

*in the ovarian ligament, 2 artery forceps are used instead of the 3 forceps as in the dog as the length of this ligament is shorter.