CPD ACCREDITED ARTICLE
done at 15 minutes and 60 minutes after delivery
26,27,69
. This may be because more time was allowed to elapse for removal of depressive effects of the anaesthetic agents before an Apgar score was evaluated . In the current study the delay from delivery till Apgar score evaluation may have allowed for complete reversal of medetomidine in the puppy and for the concentration of propofol in the central nervous system to diminish by redistribution which is reported to take 15 to 20 min 8 , 72 . Furthermore , the low induction dose of propofol used and atipamezole administration , may also have favourably influenced Apgar scores .
In agreement with the studies by others 27 , 26 , the current study shows that Apgar scores correlate with mortality , with lower scores being associated with higher mortality rates . Although another study has shown that English Bulldog puppies were at increased risk compared to other breeds for suffering from poor vigour after CS 11 , our study showed only slightly reduced Apgar scores when compared to other purebreds and Boerboel puppies . The method of delivery may impact puppy vigour . In contrast to findings by others , we recorded higher Apgar scores for puppies from caesarean deliveries than those of the eutocic vaginally delivered puppies reported in the literature
73,74
. These differences may reflect the different anaesthetic protocols used in the studies and the timing of obstetric intervention . Our results show that medetomidine appeared not to have affected the Apgar score .
The effect of early intervention by CS ( at the first observation of a dilated cervix ), prior to foetal compromise may in part explain the good results obtained in our study . This agrees with the literature reporting positive correlation between timeous intervention
12 , 21 , 75-81 and puppy survival
Conclusions This study shows that anaesthetic protocol using medetomidine hydrochloride at 7 µ g / kg iv as premedicant combined with 1 to 2 mg / kg propofol as induction agent and 2 % sevoflurane in oxygen as maintenance , is safe for CS in the bitch . The Apgar scores 15 min after delivery , as well as the puppy and maternal survival rates at delivery , 2h and 7d compare favourably to those reported in publications using other anaesthetic protocols . The use of medetomidine as premedicant permits the use of less than half the induction dose of propofol usually required when no premedicant is used .
Practical hints The primary author has been using medetomidine in more than 2000 CSs and in bitches of all sizes . The weight ( real mass not lean body mass ) of the bitch requires discussion .
In this study , all anaesthetic subjects were 20kg or more . It is however the experience of the primary author when using medetomidine at 7 µ g / kg for CSs in toy breeds , the dose of propofol required to allow intubation approaches 2-3 mg / kg as opposed to 1-2 mg / kg . Furthermore , the time allowed following induction and intubation in the prep room whilst not on gas inhalation , is reduced when using medetomidine at the low dose of 7 µ g / kg . Therefore , the author uses 10 µ g / kg medetomidine premedication for CS in dogs under 20 kg with no observable differences in outcome . Not all practices perform CSs frequently and many may not have sufficient experienced staff to ensure rapid surgical preparation and neither do all prep rooms have access to gas-inhalation anaesthesia . Therefore , if delays between intubation and connection to gas-inhalation maintenance of anaesthesia are expected , the author advises using medetomidine premedication at 10 µ g / kg irrespective of the weight of the bitch and has observed no differences in outcome when doing so . Practitioners are reminded that propofol is available in 1 % and 2 % concentrations and should make sure that they adjust their volumes accordingly .
The question whether a bitch should be surgically prepped prior to premedication , after premedication or after premedication , induction and intubation is not straight forward . Some bitches are combative and will resist the restraint required to perform surgical preparation . Some heavily pregnant bitches of any breed that are placed in dorsal recumbency desaturate whilst all English bulldogs suffering from brachycephalic obstructive airway syndrome ( BOAS ) severely desaturate when doing so ( unpublished data , de Cramer ). Furthermore , in heavily pregnant bitches suffering from BOAS , the relaxation of the airway induced by premedication causes severe desaturation ( visible cyanosis ) even in the patient that is not handled and remains in the standing or sitting position ( unpublished date , de Cramer ). Because it cannot always be predicted how a bitch will respond to restraint and because a substantial proportion of all CSs are performed on brachycephalic bitches , the prime author prefers to surgically prepare all bitches following induction and intubation .
The volume of the medetomidine at the doses described in this paper is small and therefore accurate measurement of the required volume can more reliably made when using a 1 ml syringe . Also , when using very small volumes in toy breeds , a significant volume of medetomidine may be lost in the hub of the intravenous catheter and in the tip of the syringe and therefore extending the medetomidine volume with ringers or saline may ensure administration of the full required volume . Practitioners may be tempted to use the medetomidine intramuscularly in aggressive bitches to allow for the placement of an intravenous catheter . Very large doses of medetomidine are required intramuscularly to achieve this goal and this practice cannot be advised as its safety has not been established .
REFERENCES : Available on www . vet360 . vetlink . co . za vet360
Issue 04 | AUGUST 2017 | 20